texts: Sulfuric Acid - Bond Lengths and Charge Separation

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So I know that the best Lewis Structure representation of sulfuric acid is one with only single bonds - i.e. sulfur isn't hypervalent.

However, why are the $\ce{S-O}$ and $\ce{S-OH}$ bonds not equivalent then? Why do their lengths differ?

I suspect this has something to do with the addition of the hydrogen on the oxygen atom.

What else could be a cause for the discrepancy?

I ask because my teacher challenged the fact that sulfur might not be hypervalent on the basis that the bond lengths differ.

In retrospect, I think that he:

1) Is placing too much weight on Lewis Structures - which are just rough renditions of what chemicals really are.

2) The $\ce{S-O}$ bonds and $\ce{S-OH}$ bonds may differ in length not because the $\ce{S-O}$ bonds are necessarily double bonded but also because the $\ce{S-OH}$ bonds are different in that S is bound to a hydroxyl group rather than a single oxygen. Also can't there be very minor resonance contributors involving 5-6 bonds on sulfur? It's not that sulfur absolutely can't access its d-orbitals but rather it doesn't to any great extent.


texts: Confusion regarding a stoichiometric formula

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In a book, which contains only stoichiometry problems, I came across this formula.

  For any given compound $\ce{M_xN_y}$, $x \text{ Moles of N} = y \text{ moles of M}$

According to this rule if I take $\ce{H2O}$ then, $x = 2 \text{ and } y = 1$.

So by the above formula,

$2 \text{ moles of Oxygen} = 1 \text{ mole of Hydrogen}$

But surely,

$2 * \mathrm{N_A} \not= 1 * \mathrm{N_A}$, where $\mathrm{N_A}$ is Avogadro's number.

However, in an example, the author has used this formula and successfully solved a problem? So, if it's correct, can anyone prove this and point out where my contradiction is wrong.

Example as requested:

  What weight of oxygen will react with $1$g of calcium?($\ce{Ca}= 40\mathrm{g \over mol}$)

Answer by author :
Since all the atoms of $\ce{Ca}$ have changed into $\ce{CaO}$, the amount of $\ce{Ca}$ in $\ce{CaO}$ is $1$g. Now from the formula of $\ce{CaO}$, we have,

$\text{Moles of Ca = Moles of O}$

$$\frac{\text{mass of Ca}}{\text{atomic mass of Ca}}= \frac{\text{mass of O}}{\text{atomic mass of O}}$$

therefore, $\text{mass of O} = {1\over40} * 16 = 0.4$g


texts: What effect does diluting a buffer have on its buffer capacity? I am not worried about the effect on the pH, just the buffer capacity.


texts: Ring closure via intramolecular nucleophilic substitution or intermolecular dimerization: which is favoured?

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What reaction does the following enolate undergo?

Both are nucleophilic substitution reactions. Ordinarily, the intramolecular product should be favoured, but I know that the transition state has a geometrical constraint in that the incoming nucleophile must approach the C-Br bond from the opposite side. Would that favour the intermolecular reaction instead?

I went through March's Advanced Organic Chemistry and found this:

And this from Clayden's Organic Chemistry:

That's why I am not able to decide if the reaction is intermolecular or intramolecular.


texts: Can static electricity damage solar cells?

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How does static electricity damage common solar cells making them less photo reactive? At watt voltage and/or amps would change the chemistry of the common solar cell?

I want to think that as long as the amps are low with a high voltage the static electricity would not change the silicon?

____________________________________________________________
Related: https://space.stackexchange.com/questions/35661/could-a-solar-panel-be-modified-to-also-collect-a-static-charge-on-mars

From comments: How they should accumulate that static charge?

This similar to the method I would use to generate static electricity but is not limited to this method. Only the body above the line is important for an answer.

They would accumulate a static charge by moving dust and air past the cells like the blades of this helicopter but with more surface area with less speed.

https://space.stackexchange.com/questions/35587/could-electricty-be-generated-from-a-martian-dust-storm
https://defence.pk/pdf/threads/helicopter-static-electricity-phenomenon.75190/


texts: What are some reactions which can be used to study "Effect of Catalyst on the Rate of Reaction"?

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I wish to study the effect of catalyst on the rate of reaction as an investigatory project.
What are some reactions and ideas that I could use to study this?

One example to this is the decomposition of $\ce{KClO_3}$ with $\ce{MnO_2}$ catalyst, The time for which $\ce{O_2}$ is evolved can be studied while varying the amount of catalyst.

What are some similar nice reactions with which notable changes in the reaction with changing amount of catalyst can be observed ?

What can be other changes I could bring in the reaction to study different aspects of the reaction and this topic effectively?

Suggestions please.

I know this question is open ended but please feel free to suggest anything that comes to your mind that can be done in high school laboratory.


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Iron(II) sulphate solution is added to a test-tube. Following this, potassium manganate solution is added gradually to the test-tube as well. The observation seen is that the green solution turns pink at first, then potassium manganate turns colourless as manganese(VII) is oxidised to manganese(II).

But Fe(II) is oxidised to Fe(III) ions as well, which are brown in colour, so shouldn’t the solution turn brown instead of colourless?

I have seen these observations experimentally in the lab but still did not understand. I know I’m probably thinking about it the wrong way so any help would be much appreciated.


texts: Deciding the major product in this Wurtz reaction

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Today I was told:

  When 2-chlorobutane is reacted with 2-chloropropane in the presence of sodium and dry ether the following products are formed:

2,3-dimethylpentane
3,4-dimethylhexane
2,3-dimethylbutane

  3,4-dimethylhexane, being most symmetric, is the major product.

I'm not satisfied with the reason provided. Can anyone please explain the fact in a better manner?

What I'm unable to understand is that both 3,4-dimethylhexane and 2,3-dimethylbutane and equally symmetric since both have a plane of symmetry, don't they? Then how are we using symmetry to compare the yield?


texts: Is there any rule why a crystal made of Si and C is named silicon carbide SiC, but never carbon silicate CSi? Both silicon and carbon are in the same group, so share many of the atomic properties, so why the asymmetry in naming? Are all such compounds named like <HigherPeriod> <LowerPeriod>?


texts:
Today I was asked to show that the perpendicular height, $H,$ of a regular tetrahedron is related to the length of a side, $L,$ of the tetrahedron, by $H = \sqrt{(2/3)} \cdot L$. I did this no problem.

I was then asked:
Explain how this is relevant in determining a relationship between the unit cell parameters, $a$ and $c$ of a hexagonal-close packed crystal structure: $c = 1.633 · a$.

Could anyone possibly help me out here?


texts: What is the difference between strontium-86 and strontium-90?

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I know that strontium ($\ce{Sr^90})$ has a higher mass number than its counterpart, but strontium ($\ce{Sr^86}$) is non-radioactive and not deadly to humans.

What makes $\ce{Sr^90}$ so different that it is cancerous and lethal to humans? Is it just the chemical makeup of the element that makes the difference?


texts: Deriving an expression for reaction time in terms of the total concentration

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Consider the dimerization of protein $\ce{A}:$
$$\ce{2A <=> A2}$$
with forward rate constant $k_1$ and backwards rate constant $k_{-1}.$ Derive the following expression for the reaction time in terms of the total concentration of protein
$$\frac{1}{\tau^2} = k^2_\mathrm b + 8k_\mathrm ak_\mathrm b[\ce{A}]_t,$$
where $[\ce{A}]_t = [\ce{A}] + 2[\ce{A2}].$

I assumed the 1st order in the forward direction and the 2nd order in the reverse direction. Rate law:
$$-\frac{\mathrm d[\ce{A}]}{\mathrm dt} = k_1[\ce{A}]^2 - k_{-1}[\ce{A2}].\tag{1}$$
At equilibrium
$$k_1[\ce{A}]^2_\mathrm{eq} - k_{-1}[\ce{A2}]_\mathrm{eq} = 0.\tag{2}$$
I then substituted that into the rate law and factored out the rate constants with the aim of getting rid of all of the equilibrium concentrations. The equation indicates that
$$\frac{-1}{2}\frac{-\mathrm d[\ce{A}]}{\mathrm dt} = \frac{-\mathrm d[\ce{A_2}]}{\mathrm dt} \quad\implies\quad \frac{\mathrm d[\ce{A}]}{\mathrm dt} = -2\frac{\mathrm d[\ce{A2}]}{\mathrm dt}.\tag{3}$$
I then got stuck. I saw something where you define a displacement variable $x$ and then try to get the rate law in terms of $x,$ but I've tried that approach and keep running into dead ends.


texts: What is the melting point of glycerol in a vacuum?

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Can anyone tell me what the melting point of glycerin would be in a vacuum?

From researching online (disclaimer: I'm definitely not a chemist) it seems the boiling point is $\approx \pu{170^\circ C}$ in a vacuum (vs. $\approx \pu{290^\circ C}$ at sea level), and the melting point at sea level is $\approx \pu{18^\circ C}$ so my best guess for a melting point is $\pu{-102^\circ C}$?


texts: Is an explosion merely an exothermic reaction?

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An exothermic reaction is apparently one that releases energy to it's environment. According to Wikipedia, an explosion is a rapid increase in volume & energy.

Does this mean that an explosion is basically an exothermic reaction?


texts: Why is the thioester bond weaker than a regular ester bond?

texts: What are the contributing factors to the fact that thioesters are less stable than their oxygen counterparts?


texts: What are the magnetic properties of [Ni(S2C2Ph2)2]^z's 3 oxidation states?

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I was doing some research on Wikipedia and I came across the article on non-innocent ligands. It talked about the chemical $$[\ce{Ni(S_2C_2Ph_2)_2}]^z$$ as an example. It mentioned that the transition metal complex was diamagnetic when it was neutral(z=0). I decided to figure out how many unpaired electrons the central nickel atom would have at various formal oxidation states. I found the following:

$$
\begin{array}{ccc}
\ce{Ni(II)}&(z=-2)&=2~\text{unpaired}\\
\ce{Ni(III)}&(z=-1)&=3~\text{unpaired}\\
\ce{Ni(IV)}&(z=0)&=4~\text{unpaired}\\
\end{array}$$
I don't understand why the complex is diamagnetic when its charge is 0. The radical ligands would be coupled with each other anti-ferromagneticly but there would still be 4 unpaired electrons in the central nickel atom. Wouldn't they make the complex paramagnetic? Could someone please explain to me why it is diamagneic and tell me whether the other 2 oxidation states are para or dia-magnetic.


texts:
I read that Prafulla Chandra Ray prepared Mercurous nitrite for the first time and published a paper.

Both Mercurous ions and nitrite ions are quite stable. So they should readily form the compound.

Why is it difficult to prepare it, and how to prepare it?
Can it be obtained by simply mixing $\ce {Hg2Cl2}$ and $\ce{AgNO2}$, where $\ce{AgCl}$ will be precipitated?


texts: Can a catalyst appear in the rate equation?

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According to Wikipedia:

  Chemical reactions occur faster in the presence of a catalyst because the catalyst provides an alternative reaction pathway with a lower activation energy than the non-catalyzed mechanism. In catalyzed mechanisms, the catalyst usually reacts to form a temporary intermediate, which then regenerates the original catalyst in a cyclic process.

Since catalysts react in intermediate reaction and hence in the rate-determining step, is it possible that they appear in the kinetic rate equation?

If so are there some examples?

Edit: For more clarity I encountered this doubt in a true or false question which went like this:" Catalyst can appear in kinetic rate equation".

Edit 2: As told in the comments, another similar question says specifically that catalyst are not included in rate equations, but the question I encountered says it might sometimes. So there is some irregularity in my question which seems highly unlucky to me as I have read some examples like hydrolysis of esters where rate is directly proportional to H+ concentration.

Am I wrong?


texts: Why do they flush people with water after chemical attack?

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I recently viewed a video (dated April the 6th 2017), which purports to show the aftermath of a chemical attack (where Sarin was employed).
Could anyone explain why the victims in the video were doused with water? To what degree does such measure help?


texts: How is it possible to get an attractive charge-dipole interaction using the modified Coulomb law?

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Vqµ = − qµ / (4π ε0εr r2)

Say you had a negative charge, interacting with the positive end of a dipole then the charge would be -1.602 x 10-19 C and the dipole moment would always be a positive value. This means Vqµ would always be positive.

However a negative charge interacting with the positive end of a dipole is an attractive interaction so Vqµ should be negative. What am I missing here?


texts: How did Scientists Capture The First Images of Molecules Before and After Reaction?

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Using a state-of-the-art atomic force microscope, the scientists have taken the first atom-by-atom pictures, including images of the chemical bonds between atoms, clearly depicting how a molecule's structure changed during a reaction. Until now, scientists have only been able to infer this type of information from spectroscopic analysis.  — Source

Are there any papers how this thing actually works?


texts: According to MO theory, why is the dilithium cation more stable than the dilithium anion?

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According to molecular orbital theory, $\ce{Li2}$ fills up two electrons in the $\sigma_\mathrm{g2s}$ molecular orbital;
$\ce{Li2+}$ fills up one electron in the $\sigma_\mathrm{g2s}$ MO, and
$\ce{Li2-}$ fills up two electrons in the $\sigma_\mathrm{g2s}$ MO and one electron in $\sigma^*_\mathrm{u2s}$, resulting in the same bond order for the ions.

I first thought that $\ce{Li2+}$ is stable, because they don't have paired electrons in $\sigma_\mathrm{g2s}$, therefore there is no pairing energy.
I soon found that $\ce{Li2+}$ is stable, but someone said it is due to the unfilled antibonding orbital. Is this a right explanation?

Because $\ce{Li2}$ is homonuclear, the weight that imposed on each $\mathrm{2s}$ $\ce{Li}$ atomic orbital would be almost the same. Even though $\ce{Li2-}$ is unstable by filling an antibonding orbital, it will be offset by filling two electrons into the bonding orbital and it has the same bond order as $\ce{Li2+}$ does.

What am I missing now?


texts: I know the mathematical form of HUC and its statement i.e.It   is   impossible     to   determine   simultaneously. , the exact  position  and  momentum  of  an  electron. i don't know why this principle exists. Moreover, i read that this all is not due to technique inadequancies, but due to the nature of electron. What all is this? I tried to understand derivation for the mathematical form of HUC (just to get the idea why such thing exist), but it used advanced mathematics (I'm in class 11). Please give me the idea about why this principle exists. Why it is so that we are unable to measure velocity and position at the same time to high accuracy. (No usage of earlier established principles and maths please, in the answer.)


texts: Why are multiple oxidation states useful for a catalyst?

texts: Transition elements are good catalysts because they have multiple oxidation states?Why multiple oxidation states matter?


texts:
Glycine $(\ce{NH2CH2COOH})$ is an amino acid with two $\mathrm{p}K_a$ values $(\mathrm{p}K_{a,1}=2.0, \  \ce{COOH};\  \mathrm{p}K_{a,2}=10.0, \ \ce{NH2})$.
(a) If $\pu{0.01 mol}$ of this amino acid is used to prepare one $\pu{1 L}$ solution. Calculate the $\mathrm{p}\ce{H}$ and the $\ce{NH3+CH2COOH}$ concentration in the solution.
(b) If $\pu{10 mL}$ of the above glycine amino acid solution is mixed with $\pu{90 mL}$ of basic buffer system. If the concentration of the $\ce{NH2CH2COO-}$ was identified to be $\pu{1.05 \cdot 10^{-4} M}$ indicate the $\mathrm{p}\ce{H}$ of the glycine solution.
(c) If $\pu{10 mL}$ of strong base $\ce{NaOH}$ ($\pu{0.01 M}$) was added to solution in (a) what is the final $\mathrm{p}\ce{H}$.

For part (a):
I used $[\ce{H+}]=\sqrt{10^{-10}\cdot0.01} =10^{-6}$.
Then I used $\mathrm{p}\ce{H} =14-\log(10^{-6})$ to get a $\mathrm{p}\ce{H}$ of $8$.
While my $\ce{NH3+CH2COOH}$ is $\pu{10^{-6} L}$.

For part (b):
I used the Henderson-Hasselbalch equation for a basic buffer $$\mathrm{p}\ce{H} =\mathrm{p}K_a     +\log\left(\frac{\ce{[NH2CH2COO- ]}}{\ce{[NH2CH2COOH]}}\right)$$ I got a $\mathrm{p}\ce{H}$ of $10.97$. But I'm   unsure of my answer.

For part (c):
I suspect that it is a basic buffer but I'm not sure which value to use. could anyone help me out with this.


texts: Mechanism of conversion of Cr from FeCr2O4 (chromite)

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The basic steps involved in the conversion of $\ce{FeCr2O4 -> Cr}$ involves,

$$\ce{FeCr2O4 ->[NaOH / air, \Delta] Na_2CrO4 ->[C, \Delta] CrO3 ->[Al, \Delta] Cr}$$

Basically, I'm having problems in learning so large amount of inorganic reactions, so I thought it would be easy to learn the mechanism behind these reactions, just like we do in organic chemistry.
Therefore, I'm keen to know the mechanism behind first conversion (i.e., from $\ce{FeCr2O4 -> Na_2CrO4}$). I've already tried to search for this, but found nothing related.

My attempt
I know some basic sets of inorganic mechanisms, as follows

Ion-exchange
Decomposition
Water-addition
Redox
Complex reaction

From the above listed, I don't think it would be ion-exchange (bcoz, $\ce{FeCr2O4 -> FeCr+ + CrO4-}$ is very unlikely to happen), water-addition or complex reaction. I guess it could be decomposition or redox, but I'm not sure on the "bond-movement" mechanism part.


texts: is my reasoning for enantiomers/meso compounds correct?

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I think a and b are enantiomers because a has R configuration but b has S configuration.

I think c and d are identical compounds which makes them a meso compound. If you just turn it 180 degrees they look the same to me. Am I right or is there something wrong with what I'm saying?


texts: Assuming the molecule is a sphere, would the radius of amylopectin be $9.17*10^{-22}~cm^3$? I arrived at this answer by deriving the molar volume by dividing the molar mass ($828.72~g/mol$) of amylopectin by its density ($1.5~g/cm^3$). Then I divided the quotient by Avogadro's constant to arrive at my aforementioned answer. However, I don't know if this is correct so please correct me if I am not.


texts: Are there common diluents for oils that will not cause an emulsion when added to water

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If I combine a viscous oil into solution in a carrier in a ratio of between say 1:10 or 1:100 to make it low viscosity but not separate into layers.

I then place a few drops onto a larger quantity of water (think indoor water feature) to spread out as a thin film. Boiled water with a gas barrier may be less likely to start going green.

My thoughts are 100% isopropyl alcohol, 100% acetone or 95% denatured ethyl alcohol but not sure if they will cause my oil to go in to emulsion rather than float on top.

Is there a carrier that will dissolve into the water but leave
the very thin oil on the surface?
Do I need to use a non-polar hydrocarbon that can evaporate instead of
a polar solvent that would move into the water?

The carrier should be safe enough to handle and any residue non toxic to your lawn or kitchen drain when disposing of the water later and any vapours not highly flammable or toxic to inhale. It is not intended for consumption.

EDIT:
Addition to clarify for comments.

I apologize that am not able to give the specific application at this point.
The water not going green was an attempt at illustrating a possible application (I did not realise it might not even work), another similar application would be the layer of paraffin oil (iirc) that was sprayed on stagnant ponds to control mosquito larva (though mechanical sealing of their breathing tubes iirc), the sprayers were used as an aid to dispersal but I don't want a sprayer, the right carrier for me might even work for this application though no my goal.

The aim is to have some way to dispense a thin layer of oil on to the surface of still water.  The final layer will be very thin and the amount of remaining oil would be less than the dispensing amount.

The oils will be of organic origin, possibly semi viscous.
The carrier is intended to get out of the way in a few minutes.
The carrier is to ease dosing and assist with spreading otherwise I could just mix it with lots of oil have thick film and large doses, not ideal.
I am indifferent of whether the carrier goes into the water or evaporates as long as it is not horrible stuff.
I will avoid noxious, toxic, explosive and greenhouse type chemicals, we are talking about drops and no likely ignition sources so flammability is not a big concern.
Part of this problem is to avoid having to require shaking, mixing or other special handling or storage of the dispensing mixture.
I am worried that if I use water as a carrier with an emulsifier to prevent separation, on application the oil will not float on the surface but will disperse into the water pool.

Additional problem is that the vapour pressure cannot be so high that it needs to be held under pressure, this is the other extreme where I could just use an aerosol can with propane but that is really far from ideal.

Pentane may be in the right direction, I will look further, are there consumer applications that use pentanes?

I wonder what perfumes would do if dropped onto water, will the carrier drag oily scents into the water or let them float (note to self must run a few tests)? What are the carriers, alcohol (and read some labels)?


texts: Why Cu looses 2 electrons to become stable instead of gaining one electron to fill its 4s2 3d10 configuration?

texts: Cu has 4s1 3d10 configuration so why it does not gain 1 electron and complete its suborbital. Why it looses its 2 electrons to become Cu++ which is more stable. Why?


texts: Why do we use coefficients for RFM (relative formula mass) in atom economy?

texts:
Usually when calculating using moles = mass / RFM, the coefficient is not multiplied by a compound's RFM to calculate RFM.

But in calculations for atom economy, the (balanced) coefficient of a compound is used in calculating RFM. Why is this the case?


texts:
I am currently taking a chemistry course about acids and bases. One of the things I am a bit confused about, is the acid and base neutralization reaction, and how to balance it. For Example:

$$\ce{NaOH + HCl -> NaCl + H2O}$$ How do you write the ionic and net ionic equations for that?

Note: My main problem here is that my teacher requires us to first write the ionization of the $\ce{HCl}$ into $\ce{H3O+}$ and $\ce{Cl-}$. This is when I get confused, because I don't know how to balance the equations with the $\ce{H3O+}$

Also, I had another question in my exam, which I got wrong because of the balancing. Can you please tell me the correction of it:

  Consider the neutralization reaction between nitric acid and calcium hydroxide. Write the balanced neutralization reaction and the ionic and net ionic reactions of it:


texts: What is the probability of 3 possible products, between two chemical species?

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I am not a chemist. I hope I will be specific enough.

Suppose there are two chemical species $\ce{A}$, $\ce{B}$ with the following properties:

at temperature $t < T_r$, no reaction occurs between $\ce{A}$ and $\ce{B}$ (in any combination).
at $t\ge T_r$, $\ce{A}$ interacts with itself to create $\ce{A_2}$, $\ce{B}$ reacts with itself to create $\ce{B_2}$, and $\ce{A}$ and $\ce{B}$ are reacting to create $\ce{AB}$.
$\ce{A_2}$, $\ce{B_2}$ and $\ce{AB}$ are never reacting.

In experiment, we first mix $\ce{A}$ and $\ce{B}$ in temperature $t<T_r$. Amounts of species mixed are $a$ for $\ce{A}$, $b$ for $\ce{B}$. Then, we add heat to obtain temperature $t\ge T_r$ and start the reaction.

What amounts of $\ce{A_2}$, $\ce{B_2}$, and $\ce{AB}$ can be expected to be produced?
To obtain the amounts, should probability theory be used? E.g., amount of $\ce{AB}$ equals to probability that species $\ce{A}$, $\ce{B}$ will interact ("collide" or similar interpretation).

Assume the rates of the reactions are equal.


texts:
In the nonideal solution, why can't one of the solute be positive deviation and the other be negative deviation?
Let's say A and B makes a nonideal solution.
The moleculat force between A and B means A-B.
Let's say A-A > A-B > B-B.
Then A would evaporate more than in the pure state, and B would evaporate less than in the pure state.


texts: Why does benzene have only 2 resonance structures? Please answer keeping in mind I am in highschool

texts:
Why isn't this structure a part of resonating structures
I can't upload the desired image so I will describe the structure. cyclohex 1,3 diene where carbon with numbering 2 has negative charge and carbon with numbering 5 has positive charge


texts: Limit the production of hydrogen in a small container

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I have to produce hydrogen at a near-constant pressure inside of a really small container without using an automatic pressure release value. I would like the pressure to be relatively high, but the most important aspect is that the exact pressure needs to be predictable. I was thinking of utilizing the reaction between aluminum, water, and sodium hydroxide.

Al2O3 + 2 NaOH + 3 H2O  → 2 NaAl(OH)4
Al2O3 + 2 NaOH          → 2Na+ + 2[Al(OH)4]-

2 Al + 2 NaOH + 6 H2O   → 2Na+ + 2[Al(OH)4]- + 3 H2
2Al + 2NaOH + 2H2O      → 2NaAlO2 + 3H2.

Now, I know the pressure will slow down the reactions, but will the reactions completely stop at a certain pressure? If so, how can I deduce that specific pressure given the different concentrations of reactants and constraints of the container?

Safety is my number one priority, so I need to make sure that I can predict this pressure to a high degree of accuracy. If the pressure is too high, I won't even attempt anything. Any advice on this would be greatly appreciated.


texts:
In theory you should be able to turn $\ce{CO2}$ to $\ce{CO}$ and then to $\ce{C}$ and connect all the C-atoms together to form graphene.
That should be possible, because plants do something similar, they take $\ce{H2O}$ and $\ce{CO2}$ and link the C-atoms together as $\ce{C6H12O6}$.

Is it possible to produce graphene out of air? Here is a related article from the RCS: "Conjuring graphene oxide from thin air"


texts: What is the nature of the oxide of boron?

texts:
I think it should be acid, as I am aware that a compound by the name of Boric acid exists. But how can the oxide be acidic when it is electropositive? Also, other members of its group are well known metals. Why isn't the oxide amphoteric, when its group member Aluminium has an amphoteric oxide?

My teacher told us that the oxide of boron is basic in nature? So what exactly is its nature?


texts: Where to find Atmospheric data for various cities

texts:
Hi im searching for atmospheric data on the following:

Air quality, Dust Particle Concentration, Pollution, Average Temperature etc

for various cities such as Frankfurt, London, Hong Kong, Bangkok...

Are there any websites that can give me this data (or similar atmospheric measurements) for each city?


texts: Why does STED microscopy cause photodamage?

texts:
STED (stimulated emission depletion) microscopy is a technique which enables sub-diffraction limit of light imaging.
The depletion laser is at 775nm, and about 500 mW, concentrated for a short sequence of pulses on an area about the size of ~0.2 um^2
As far as I can tell very few organic molecules, nor water, absorb in this range of 775nm.
So why does it cause photodamage?
Thermal damage sure, but why bleaching fluorophores so fast?


texts: I was given a question to draw the structure of $\ce{Fe(CO)6}$ and tell the hybridization. Hybridization came out to be $\ce{sp^3d^2}$ and structure as Octahedral. But does $\ce{Fe(CO)6}$ really exist? I could not find anything about it on the internet.


texts: I have seen KIT-6 used in literature as a catalyst support, but cannot find the chemical formula for it.


texts: Identifying endothermic and exothermic reaction

texts:
How can I know that a given reaction is endothermic or exothermic? I know that all combustion reactions are exothermic. But what about other reactions?

In my school exam I was asked about whether the reaction

$$\ce{N2 + O2 -> 2 NO}$$

is exothermic or endothermic. I didn't know that it is endothermic reaction and left that question. My teacher hence suggested me to learn all exothermic and endothermic reactions! Is it possible to do so? (Obviously not.) Please help me.


texts: What is the reason behind the characteristic colours of elements?

texts:
I've been trying to find out about this for some time now and when I searched online, I couldn't get any proper reasons.
My question is: What is the reason for the characteristic colours of elements? For eg: Why does Sodium have a characteristic colour of silvery-white?
Is there any solid scientific reason behind this?


texts: What is the effect of polar protic solvent on nucleophilicty?

texts:
Question

Attempt:

I could figure out the answer correctly using simple rules governing nucleophilicity . But my doubt is how does polar protic solvent affect nucleophicity. And what would be the answer in case of polar aprotic solvent?. Please help.


texts: How to compare the energies of sigma and pi bonds in molecular orbitals of diatomic heteronuclear species?

texts:
There is a rule for diatomic homo-nuclear species that says that if $Z<8$ then $$E(\sigma_{2p})>[E(\pi_{2p_y})=E(\pi_{2p_z})]$$ and the inverse if $Z\geq8$ and in both case we have energy of $$E(\sigma_{2s}^{*})>[E(\pi_{2p_y}^{*})=E(\pi_{2p_z}^{*})].$$

This is understandable but what if we have diatomic heteronuclear species like $\ce{NO}$ or $\ce{CO}$?

How can we determine which of the molecular orbitals $\sigma$ or $\pi$ is higher in energy? I.e. how should we know which to place below which in the molecular orbital diagram (sigma or pi orbitals)?


texts: Why did my beer slowly froth up after removing from freezer?

texts:
I got a beer out of the freezer last night and opened it, only to realize that it was almost frozen, so I left it to warm up. 10mins later I hear a dripping noise and realize that the beer had overflowed and was starting to spill off the table.

What causes this slow expansion of beer after it is warmed from a near 0°C temperature?


texts: Why does pKa of a acid-base indicator equal to the pH when the equivalence point is reached?

texts:
To be honest, I just don't get it.
I had this question while reading a Chemguide article, on this topic:

I think my confusion is caused by the way I look at pKa of acid-base indicator. Should you think of it more as a reaction quotient. Because technically, at equilibrium, the two concentration aren't the same so cannot be cancelled out.


texts: How do I find the ratio in which the residue of a reaction combines with HCl?

texts:
A mixture weighing $4.08\ \mathrm g$ of $\ce{BaO}$ ($M(\ce{Ba})$ = $138\ \mathrm{g\ mol^{-1}}$) and an unknown carbonate $\ce{XCO3}$ was heated strongly. The residue weighed $3.64\ \mathrm g$. This was dissolved in $100\ \mathrm{ml}$ of $1\ \mathrm M$ $\ce{HCl}$. The excess acid required $16\ \mathrm{ml}$ of $2.5\ \mathrm M$ $\ce{NaOH}$ solution for complete neutralization. What is the molar mass of $\ce{X}?$

My approach:

$16\ \mathrm{ml}$ of $2.5\ \mathrm M$ $\ce{NaOH}$ means $0.04\ \mathrm{mol}$ of $\ce{NaOH}$. Thus, the excess acid was $0.04\ \mathrm{mol}$ of $\ce{HCl}$. $100\ \mathrm{ml}$ of $1\ \mathrm M$ $\ce{HCl}$ means $0.1\ \mathrm{mol}$ of $\ce{HCl}$. Thus, $0.06\ \mathrm{mol}$ of $\ce{HCl}$ reacted with the residue. Now, how can I find the ratio in which the residue reacted with $\ce{HCl}?$ What is the composition of the residue?


texts:
The commonly shown structure of the ClO radical described here has a single bond between the chlorine and oxygen atoms. In that structure, chlorine has a formal charge of 1, and oxygen has a formal charge of -1.

Why doesn't ClO have a double bond between the chlorine and oxygen atoms instead? That way, the radical would exist on the chlorine atom, and both atoms would have a formal charge of 0.


texts:
Compare the acidity of the following compounds: $\ce{CF3OH}$ and $\ce{CCl3OH}$.

My attempt: according to me $\ce{CCl3}$ group will show a stronger Negative hyperconjugation effect than $\ce{CF3}$, and thus would stabilize the anion more effectively.

But the answer is $\ce{CF3OH}$ is more acidic. What is wrong in my approach?


texts: Where is the mirror plane in 1-bromo-1-chloroethene?

texts:
I am studying point groups in inorganic chemistry and having a very difficult time understanding some of these concepts.

In my book, Inorganic Chemistry: Fifth Edition by Miessler, Fischer, & Tarr, I am presented with a table showing that $\ce{CHFClBr}$ is in the $C_1$ point group and has no symmetry other than the identity operation.

$\ce{H2C=CClBr}$ is in the $C_\mathrm s$ point group and its symmetry is listed as having only one mirror plane.

I'm having difficulty seeing this mirror plane. I would have listed this compound as being in the $C_1$ point group. Does this have something to do with the molecule being flat?


texts: Estimating amount of Hydrogen Sulfide released into the air? and how fast does gas expand when it is produced?

texts:
I unknowingly exposed myself to hydrogen sulfide gas and am trying to figure out how much Hydrogen Sulfide gas i may have been exposed to.
I mixed .5 grams of Sodium Sulfide Nonahydrate into a solution containing excess acid (NH4+) as shown below. So I expect all of the Sodium Sulfide to react to form Hydrogen Sulfide.
KH2PO4  0.4
NA2HPO4 0.53
NH4CL   4.0
Na2S.9H2O   0.5

100mL water

If all the Na2S.9H2O reacts , then 70.83mg of Hydrogen Sulfide are produced.
At room temperature and one atmosphere (inside of a small room say a studio sized room), is there any way to estimate how much exposure I received? in terms of PPM given how much Hydrogen Sulfide was produced?
I immediately smelled rotten eggs and then the smell went away after a second. Is this because I inhaled so much? Or because it dissipated so quickly?
That Hydrogen Sulfide is heavy also complicates things (does it not spread as easily? would it settle around me instead of spreading all around the room?)

To add, this paper shows that most of the hydrogen sulfide is released from solution amost immediately in HEPES buffer, so I wonder if  it would be the same here, and what that means for exposure
(did i just breath in most of the hydrogen sulfide at once,  or did it spread out  into the air so fast i did not breath much in?)
https://www.sciencedirect.com/science/article/pii/S0003269711006695?via%3Dihub
"A preweighed crystal was dropped into an open 150-ml beaker containing 100 ml of
Hepes buffer (arrow). The solution was mixed with a magnetic stir bar, and H2S
was recorded with the H2S sensor. More than 80% of the H2S was formed during the
first 10 s, essentially as fast as the crystals was dissolved, and H2S
concentration subsequently declined due to volatilization. Panels A and B are
from the same experiment with different time scales."

```````


texts: How do I determine the average carbon oxidation numbers in ethanol and ethanal?

texts:
I have an assignment (I quote it word by word):

  Determine the oxidation number of carbon in (A) ethanol and (B) ethanal. Answers are (A) -2 and (B) -1.

I reviewed similar question at SE: Oxidation of Carbons
and I found first answer to be clear and links given in this answer to be useful.
I also found a good  Khan Academy video, which basically confirms all in this answer

Now, here is my problem: There are two carbons in ethanol. Oxidation number of carbon which is connected to three hydrogens is $-3$; oxidation number of carbon which is connected to two hydrogens and one oxygen is $-1$. How do we get answer $-2$ out of it then? (Do we add $-3 + (-1)$ and then divide by 2?)

And again there are two carbons in ethanal. Oxidation number of carbon which is connected to three hydrogens is $-3$; oxidation number of carbon which is connected to one hydrogen and one oxygen (but with double bond) is $+1$. How do we get answer $-1$ out of it? (Do we add $-3 + 1$ and divide it by 2?)

Overall, my question does not seem to concentrate on one of the carbons present in ethanol (or ethanal). And answers given look like there is oxidation number of first carbon added to oxidation number of second carbon and then divided by 2. This situation seems to be true for ethanol, and again the same happens for ethanal.
Where can I read about adding two oxidation states and then calculating average (I have never heard of it)? Or maybe these calculations done in some other way? Thank you very much in advance for answering.


texts: Detection limit for log-log calibration curves

texts:
The limit of detection ($LOD$) for an analytical method can be derived from its calibration curve using the following equation:
$$ LOD = {\dfrac{(3.3 \cdot {\sigma_
\mathrm{resids}})} {m}} \tag{1} $$ [see reference at bottom]
where:

$ \sigma_\mathrm{resids} $ is the standard deviation of the residuals of the regression fit
$m$ is the slope of the regression curve.

Would the above equation still apply if I were to apply it to a calibration curve generated through linear regression of $\ln(y)$ on $\ln(x)$?
Here's an example data set that I generated (artifically - hence apparent rounding errors) to reflect what would be seen in some electrospray ionisation-mass spectrometry data (non-linear and heteroscedastic):
$$\begin{array}{|c|c|c|c|}
\hline
\text{Calibrant} & x \ (\pu{mg/L}) & y \text{ (peak area, AU)} & \ln(x) & \ln(y) \\ \hline
\text{S1} & 1 & 550 & 0 & 6.309918 \\ \hline
\text{S2} & 1 & 500 & 0 & 6.214608 \\ \hline
\text{S3} & 1 & 450 & 0 & 6.109248 \\ \hline
\text{S4} & 2 & 1100 & 0.693147 & 7.003065 \\ \hline
\text{S5} & 2 & 1200 & 0.693147 & 7.090077 \\ \hline
\text{S6} & 2 & 1300 & 0.693147 & 7.17012 \\ \hline
\text{S7} & 10 & 6500 & 2.302585 & 8.779557 \\ \hline
\text{S8} & 10 & 7000 & 2.302585 & 8.853665 \\ \hline
\text{S9} & 10 & 7500 & 2.302585 & 8.922658 \\ \hline
\text{S10} & 50 & 40000 & 3.912023 & 10.59663 \\ \hline
\text{S11} & 50 & 45000 & 3.912023 & 10.71442 \\ \hline
\text{S12} & 50 & 50000 & 3.912023 & 10.81978 \\ \hline
\text{S13} & 125 & 140000 & 4.828314 & 11.8494 \\ \hline
\text{S14} & 125 & 150000 & 4.828314 & 11.91839 \\ \hline
\text{S15} & 125 & 160000 & 4.828314 & 11.98293 \\ \hline
\text{S16} & 250 & 400000 & 5.521461 & 12.89922 \\ \hline
\text{S17} & 250 & 420000 & 5.521461 & 12.94801 \\ \hline
\text{S18} & 250 & 440000 & 5.521461 & 12.99453 \\ \hline
\text{S19} & 500 & 1000000 & 6.214608 & 13.81551 \\ \hline
\text{S20} & 500 & 1200000 & 6.214608 & 13.99783 \\ \hline
\text{S21} & 500 & 1400000 & 6.214608 & 14.15198 \\ \hline
\end{array}$$

Applying equation (1) and exponentiating the result, the $LOD$ would come out as:
$$ LOD = \exp {\left(\dfrac{3.3 \times 0.177}{1.2265} \right) } = \pu{1.61 mg/L} $$
The strange thing for me is that if I multiply the original concentrations ($x$) by 1000, say to convert to from $\pu{mg/L}$ to $\pu{\mu g/L}$,and then generate the calibration curve of $\ln(y)$ on $\ln(x)$, the $LOD$ comes out at exactly the same value, i.e. 1.61. This is because the slope and the standard deviation of the regression fit are unchanged by multiplying the concentration by 1000 - only the intercept value changes. Note, given that concentration axis was in $\pu{\mu g/L}$ before $\ln$-transformation, this would presumably mean an $LOD$ of $\pu{1.61 \mu g/L}$?
My suspicion is that I've missed a crucial step in calculating $LOD$ from the $\ln$-transformed calibration curve model.
Thanks for any pointers you can provide!
Reference: https://www.ema.europa.eu/en/documents/scientific-guideline/ich-q-2-r1-validation-analytical-procedures-text-methodology-step-5_en.pdf


texts: To calculate expansion work for a process

texts:
[1 mark] To calculate the expansion work for a process,
  1) the formula $w = -P_\mathrm{ex}(V_2 - V_1)$ always works under all conditions.
  2) the formula $\mathrm dw = -P_\mathrm{ex}\,\mathrm dV$ can only be used for irreversible processes.
  3) the formula $\mathrm dw = -P_\mathrm{ex}\,\mathrm dV$ always works under all conditions.
  4) the formula $w = -nRT\ln (V_2/V_1)$ always works for any isothermal reversible process.
  5) None of the above is applicable.

I'm torn between options 1, 3 and 4. I see those 3 all as correct. Can someone point to me which one might be right and why?


texts: Find the initial volume of the weak acid given a titration graph

texts:
Question:

  Below is a picture of a titration between a weak acid, $\ce{HA}$, and a 0.150 M $\ce{NaOH}$ solution. Find the initial volume of the weak acid in milliliters in this titration.

My work so far:
From the graph, I think that the two most important points are (0,3.0) and (20.00,8.0) - I don't know the reason, but it looks important.
At (0,3.0), there is no $\ce{NaOH}$. This equilibrium takes place:
$$ \ce{HA_{(aq)} + H2O_{(l)} <=> A_{(aq)}- + H3O+_{(aq)} } $$

The constant $K_\text{a}$ can be found from:
$$
 K_\text{a} = \frac{[ \ce{H_3O^+}][\ce{A^-}]}{[\ce{HA}]}
$$
with $[\ce{H_3O^+}] = 10^{-3}$ since $\text{pH}=-\log_{10}[\ce{H_3O^+}]=3$
This is a dead end for me.
At (20.00, 8.0), $[\ce{H_3O^+}] =10^{-8}$, this number has decreased because some $\ce{H_3O+}$ have reacted with the newly dissolved $\ce{OH^-}$, although how much I can't tell. I have reached another dead end
Other facts I do know:

0.150 M of $\ce{NaOH}$ means for every 1 liter of the solution, there will be exactly 0.150 moles of $\ce{NaOH}$.
$\ce{NaOH}$ dissolves completely as a strong base. So, for every 1 mole of $\ce{NaOH}$ there will be 1 mole of $\ce{OH^-}$


texts: Relativistic effects and lanthanide contraction

texts:
So I understand than the lanthanide contraction is due to poor shielding of the 4f electrons which decreases the radius.
However, if Im not mistaken the relativistic effects lead to a contraction of the core orbitals (s,p) while the f and d orbitals expand. So what I do not understand how do they match, one of them decreases the radius and the other one should expand it as the f orbitals expand right?
They usually say relativistic effects are one of the reasons for the lanthanide contraction
Thanks


texts:
This drug hydroxychloroquine has become a new burning topic of discussion as a chemistry enthusiast:

I know that in an industrial preparation we need to account fpr a lot of factors like temperature, solvent, expenditure etc. I tried this, which did not seem good enough:

It seems that the nucleophilic aromatic substitution is not appropriate and the starting products chosen may not be commercially available. Can someone suggest a better yielding and more economical pathway?


texts:
I know that there already exist multiple questions concerning buffers and buffer capacities, but I would nevertheless like to clarify two things with your help:

Adding to a buffer $n$ moles of an acid of negligible volume or a solution of the same acid (also containing $n$ moles of the acid) both produce the same change in $pH$. Correct?
However there is a difference between the two, as the latter diminishes the buffer's capacity. How can I observe, from a mathematical standpoint, the decrease in the buffer capacity for the second approach; more precisely:
Given,say an acidic buffer solution of volume $V_i$ with $HA$ being the weak acid and $A^-$, its conjugate base (with concentrations $c_a, c_b$ respectively), how does the buffer capacity change upon the addition of a solution of volume $V_s$, containing $n$ moles of a strong base?

Any help would be appreciated.


texts: Confusion about boiling point and vapor pressure

texts: It is said that a liquid boils when its vapor pressure equals to the external pressure of its environment (e.g. atmospheric pressure). That’s because the bubbles of water vapor that form will be crushed if the vapor pressure is below the atmospheric pressure. However, it’s the fluid’s pressure that actually does the crushing, isn’t it? And the fluid pressure varies with depth, with only the fluid at the top of the liquid being equal to atmospheric pressure. Shouldn’t we say that the liquid boils when its vapor pressure is equal to the greatest fluid pressure in the liquid?


texts: Setup for Sensing change in concentration of NaCl

texts: I am making a sensor to sense the change in concentration of NaCl. My background is in electronics and chemistry is not my strong area. I got some screen printed electrodes, with Silver (Working Electrode) and Ag/AgCl (Reference Electrode). My initial test is to put the electrodes in separate solutions, with Reference Electrode in a reference solution of known concentration of NaCl and the Working Electrode in the test solution of varying concentration of NaCl. Will this give me a potential difference and will I be able to determine the change in Concentration of NaCl in the working electrode? If not can you make any suggestion on the setup? Thanks.


texts:
How to remove epoxy on clothes in the perspective of chemistry?
More precisely in my case, how to remove the hardener of epoxy, which consists of two components: hardener and resin.
The clothes is made in nylon, please take the least damage to the cloth into high priorities of consideration.
Does alcohol help?
Thank you very much for your reply.


texts: Which ring expansion in cyclobutyl(cyclopropyl)methanol is favourable?

texts:
Predict major product:

In this question first I've protonated the OH group and then water is removed to form a carbocation. Now I have to expand the ring, but I'm confused which ring to choose: 3-membered ring or 4-membered ring?

Note:  I can make an alkene (which would be the final product of the reaction) by removing an alpha hydrogen if it is known which ring to expand.


texts: Yttrium -- rare earth or transition metal?

texts:
The element yttrium is called a rare earth element, yet periodic tables label it as a transition metal.

Why is that?
Thanks


texts: What exactly is the "oxygen reduction reaction"?

texts:
Is it

$\ce{O2(g) + 4H^+(aq) + 4e^- \rightarrow 2H_2O(l)}$

and are there multiple types of ORR?

See here for context: http://www.nature.com/srep/2014/140122/srep03821/full/srep03821.html


texts: Color change of aqueous ferric salt when reacted with phosphate

texts:
I have a question about an equilibrium system:

$$\ce{Fe^3+ (aq) + SCN-(aq) <=> [Fe(SCN)]^2+ (aq)}\\
\text{(yellow)} \quad \text{(colorless)}\quad \qquad\text{(red)}\qquad\quad$$

The question is about what happens to  $\ce{Fe^3+}$ when you add $\ce{HPO4^2-}$ to the solution above.

I'm not sure (that's why I'm asking), but when you add $\ce{HPO4^2-}$ to the solution it reacts with $\ce{Fe^{3+} (aq)}$ and forms $\ce{Fe2(HPO4)3}$ (I’m guessing):

$$\ce{2Fe^3+ (aq) + 3HPO4^2-(aq) -> Fe2(HPO4)3}\\
\ \ \ \ \text{(yellow)} \quad \text{(colorless)}\qquad \qquad\text{(colorless)}\qquad$$

My hypothesis is: When you add $\ce{HPO4^2-}$, there is a "loss" of  $\ce{Fe^3+}$ because $\ce{HPO4^2-}$ reacts with $\ce{Fe^3+}$. This also means that there is a chemical shift to the left (The solution produces more  $\ce{Fe^3+}$), and because $\ce{Fe2(HPO4)3}$ is colorless the solution also turns colorless.


texts: A mole of atoms is the number of atoms whose total weight equals the atomic weight?

texts:
My textbook says, a mole of atoms is the number of atoms whose total weight = the atomic weight. There's something in the definition that's confusing me.

Now what is confusing me is:

Atomic weight = weight of 1 atom
Therefore, number of atoms whose total weight is atomic weight = 1.
Going by definition then, 1 mole atoms=1 atom. Which is incorrect.
Because 1 mole atoms = $\pu{6.022*10^23 atoms}$.
So from the definition apparently, weight of $\pu{6.022*10^23 atoms}$ = atomic weight(weight of 1 atom)
Which is contradictory.

Could someone clarify where am I wrong and explain the same?

PS: There are no units in the provided definition in the book.


texts: How to make equal density pool dye without diffusion

texts:
I have a leak I have been struggling to find in my in-ground pool.  I am losing about 1/4" of water per day and I believe the issue is one of the fittings in the bottom of the pool.  There are two main drain fittings and one deep pot that has two pipe plugs that if removed allows groundwater to enter into the pool to prevent the forces of buoyancy from floating the shell out of the ground like a boat when the pool is drained.

I want to make a dye that is has a specific gravity equal to water that has minimal to no diffusion.  It has to be safe because it will be introduced to the pool water.

The only thing I have found that is almost the same gravity of freshwater is beer, or milk.  The problem with those is the diffusion rate.  I was hoping to find something that I could mix with dye that had a specific gravity (I hope that is right) as near to freshwater as possible that wouldn't diffuse when introduced to freshwater.

My intention, hope, is that I would place a blob of dye over these plugged fittings and if there was a leak around the fitting it would eventually suck that dye into it.  It could take 15 minutes or more for the dye to be pulled into the leak, so it has to have a very slow diffusion rate.


texts: Does expansion of an ideal gas not always represent an increase in entropy of the system?

texts:
Expansion of an ideal gas not always represent an increase in entropy of the system. Statement is True or False?

What I thought is that whenever an ideal gas expands the randomness of gas molecules increases. So, entropy must increase.


texts: What happens to the carbon in carbon steel when it rusts?

texts:
Carbon steel is iron containing some carbon in various forms of iron carbide.

When it rusts (oxidises), the iron becomes part of all kinds of crystalline and amorphous iron oxides and hydroxides, mostly as Fe3+.

Where does the carbon go in this process? Does it also oxidise to carbon dioxide or monoxide and leaves the system as a gas? Does it combine with the iron to form siderite (iron carbonate)? Does it remain as graphite or some other form of elemental carbon? Something else?


texts: Le Chatelier's principle with pure solids and liquids

texts:
In the following reaction:

$$\ce{A(s) <=> B(g) + C(g)}$$

since adding a pure solid is not supposed to shift the equilibrium in any way, does that mean that I can essentially remove all of the solid except for 1 molecule, and the equilibrium will not shift at all since the concentration of the solid stays the same? Similarly, does this mean that I can essentially fill up the container with the solid, and no extra B and C will be produced?


texts: Reactivity comparison of phenol and toluene towards electrophilic substitution

texts:
Which aromatic compound is more reactive towards electrophilic substitution?

  benzene
  chlorobenzene
  phenol
  toluene

  Correct answer: phenol

But, according to me, the answer should be toluene.

My reason: Toluene is an ortho-para directing group as well as an electron-donating group which increases the electron density at ortho-para position and activates the aromatic ring towards electrophilic substitution.

Where I am wrong?


texts: Why CCl4 does not react with water,while SiCl4 do react,as both central atom are surrounded by 4 chlorine atom?


texts:
I read in my old Polish history handbook about the black powder recipe that was taken from some medieval manuscript, if I remember correctly.
One of the ingredients was called “salpotricon”, but years passed and I still have no clue what could it be.

So, I'm asking the internet to solve this mystery. Maybe it's a Latin word, I'm not sure.


texts: Migratory preference in a rearrangement involving carbocations

texts:
I just read about the Pinacol rearrangement and the following reaction was presented just after it. The book (Clayden) shows path 1 being taken.

My question is why is the second path not taken? I know that migratory aptitude of $\ce{Ph>H}$ but all we want is stability, so why can't the $\ce{H}$ migrate?


texts:
I was reading around about the different solid states of materials and I got to a point where I have reached the multi-component solids. I was not able to find a major difference between the cocrystal and the eutectic mixture from their definitions. Do you know of any fundamental difference?

The question in another way: if you had a mixture of 2 solids that bind to each other somehow, how can you know whether this is a cocrystal or a eutectic mixture?

Many thanks,


texts:
Learning about Oxides. Basically when oxygen is combined with a metal.

$$\ce{FeO}$$

This is called "Iron Oxide (II)" according to my book.

Apparently, the II represents the valence. But how come? Look:

$\ce{Fe}$ has the configuration $1s^22s^22p^63s^23p^6\color{red}{4s^2}3d^6$. Since the outermost shell has $2$ electrons, the valence is $2$.

Now $\ce{O}$ has the configuration $1s^2\color{red}{2s^22p^4}$. Its outermost shell has $6$ electrons so oxygen has a valence of $6$ right?

Then how come $\ce{FeO}$ has valence $2$? Shouldn't the valence of $\ce{FeO}$ be like, the combination of the two valences? So $6 - 2 = 4$? (I read somewhere you had to subtract it).

Not only that. I am starting to think that my definition of valence is completely messed up. I just checked in here and apparently Oxygen has $-2$ valence? Why? And Iron has +2, +3, (+4), (+6)? What does all that even mean?


texts: The order of increasing Covalent nature in Group 12 (Zn,Cd and Hg)

texts:
Suppose $\ce{Zn}$, $\ce{Cd}$ and $\ce{Hg}$ were to form a bond with the same element; say $\ce{ZnCl2}$, $\ce{CdCl2}$ and $\ce{HgCl2}$ Then which of the compounds would be showing most covalent character
I feel like there are two schools of thought with regards to the covalent nature of group 12 elements.
One says according to Fajans' rule covalent character is greatest for smaller cations. Therefore the covalent bond character should be $\ce{Zn}$ > $\ce{Cd}$ > $\ce{Hg}$
The other says (my theory), due to weaker shielding effect of the $\mathrm d$-block there would be more effective nuclear charge for $\ce{Hg}$ than $\ce{Zn}$. So it should be able to cause more distortion and be able have stronger covalent bond. Therefore the order should be $\ce{Zn}$< $\ce{Cd}$< $\ce{Hg}$.
Which one is correct and why?


texts: Why we need halogens of different periods in wurtz-fittig reaction? + which is the correct mechanism?

texts:
For the mechanism of wurtz-fittig reaction I got two different ones on the net.
1. From another question   on stackexchange:

From tutorvista:

They are not really the same. In the first one the alkyl group is acting as the nucleophile and as Sn reaction do not occur at sp2 hybridized orbitals, it goes through an SnAr reaction. But in the second one the aryl group is acting as a nucleophile. So the same reasoning does not apply here, because here Sn2 is happening at a primary sp3 hybridized carbon whereas the aryl group is just the nucleophile. So is the second mechanism wrong or I am missing some point? Neither of the mechanisms really show why we used two different halogens in the alkyl and aryl group (or maybe I can't understand), in fact the first mechanism is using Cl on the alkyl group whereas the second mechanism is using iodine (which is a far better leaving group). But the aryl group has bromine on both. Really confusing if I am to search for explanations myself. Please clear me up.


texts: Why is arsenic more chemically similar to phosphorus than is nitrogen?

texts:
Why is arsenic more chemically similar to phosphorus than is nitrogen (to phosphorus)?

I thought that it may be because both phosphorus and arsenic have d orbitals (albeit one has one that is filled and the other has an unfilled one).

Another possibility I thought was that because nitrogen held the electrons very closely, and thus the difference between the second and third period may be more pronounced than the difference between the third and fourth periods.

I'd really appreciate it if anyone could help clarify/ explain. Thanks!


texts:
In the German Wikipedia there are two reactions on the poles of the battery shown with the following potentials:

  $$
\begin{align}
\ce{Pb + SO4^2- &-> PbSO4 + 2 e-} &|\pu{-0.36 V}\\
\ce{PbO2 + SO4^2- + 4 H+ + 2 e- &-> PbSO4 + 2 H2O} &|\pu{+1.68 V}
\end{align}
$$

  $$E_\mathrm{Ges}^0 = \pu{1.68 V} - (\pu{-0.36 V}) = \pu{2.04 V}$$

I do understand the potential for the second $\pu{1.68 V}$ since for the second reaction the underlying redox pair is $\ce{Pb^4+ + 2 e- -> Pb^2+} $. For this redox pair the electrochemical standard potential is $\pu{1.69 V}$.

But for the first reaction I think that the underlying redox pair has to be $\ce{Pb^2+ + 2 e- -> Pb}$. This redox pair has standard potential of $\pu{-0.1263 V}$.

This result in a voltage of $\approx\pu{1.55 V}$. But Wikipedia and a book of mine tell the the voltage of this battery type is $\pu{2.04 V}$.

What the reason for the $\pu{-0.36 V}$?

Source: This is from the German Wikipedia article on lead-acid batteries. Unfortunately the English version doesn't contain the calculation of the voltage. I took the standard potentials from the book Elektrochemie by Hamann.


texts: Does lead carry the negative charge in plumbane?

texts: It says in Wikipedia that lead tetrahydride or hydrogen plumbide or plumbane ($\ce{PbH4}$) is supposed to have lead in its -4 state and the hydrogen is in its +1 state because supposedly lead has a higher electronegativity than hydrogen. Is this possible to be synthesized and actually be stable for long enough to at least view it?


texts: I know this sounds like a stupid question, but do electrons truly flow in a circuit? It doesn't seem logical for electrons to just break away from their atoms to go move through a circuit. If they did, they would probably go through a bunch of reactions and behave oddly (right?). Do the atoms lose/gain electrons to become ions and flow through the circuit? If so, wouldn't they too big to be able to flow easily through a conductor?


texts: What are the units of P and V when R is expressed in terms of J/(mol K)?

texts:
I have learnt the ideal gas equation $PV=nRT$. However, I have some doubts regarding the units of the quantities in this equation.

When we take the gas constant $R=8.314\ \mathrm{J\ mol^{-1}\ K^{-1}}$, what should be the units of $P$ and $V$?


texts: Why C4 position in pyrimidine ring is more reactive then C2 position in nucleophilic aromatic substitution and Pd chemistry? Should not be the C2 position the most reactive because of the effect of the 2 N atoms?


texts: I an currently studying acid-base titrations. There is a concept of double titration. Can someone provide me an idea on what actually it is? Also what resources can I refer to?


texts:
This is the Raman spectrum of water. There is $\pu{1635 cm-1}$ Raman peak corresponding to $\ce{HOH}$ and $\pu{3410 cm-1}$ Raman peak corresponding to $\ce{OH}$. But why is there general nonzero background in intensity? What caused it?

This is taken using 532nm wavelength raman system:

This is taken using 785nm wavelength raman system up to 2750 cm-1 only (versus 4000 cm-1 of the first spectrum):

In the above picture. Why is the background dimishing to zero towards 2750 cm-1. My guess is that as wavelength gets higher, water absorbs more. But can it absorb the noise too?


texts: Identifying orbital given electron probability density plot

texts:
Being a high-school student, I only have a qualitative understanding of the wave mechanical model of atom.

Below are my inferences regarding the plot shown in the above picture:

The concerned orbital has $3$ radial nodes (I'm counting the places where the value of the y-coordinate is zero excluding the ones at the extreme left and right).

Hence, the orbital should satisfy $n-l-1=3$. The orbitals satisfying the condition are $4s, 5p, 6d, 7f,\ldots$.

Are my inferences correct?


texts:
I have a very basic question. Energy is absorbed to break bonds. Bond-breaking is an endothermic process. Energy is released when new bonds form. Bond-making is an exothermic process.

But ATP breaks down to ADP and releases energy right? Is there anything wrong in my understanding?


texts: How do you find the heat capacity of a calorimeter?

texts:
My instructor gave me the formula:
$$C_\mathrm{cal} = \frac{C_\mathrm{bomb}}{\text{steel}+C_\mathrm{water}}$$
I know that the heat capacity for water is $4.184~\mathrm{J\,g^{-1}\,^\circ C^{-1}}$ and I calculated the value for $C_\mathrm{bomb}$, which is $356.7555~\mathrm{J\,g^{-1}\,^\circ C^{-1}}$. The part I don't understand is where it says steel. Is “steel” the same as “$C_\mathrm{bomb}$”?


texts: Dissolving collagen in water: Why does the weighing scale reading fall?

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Every day I take 10g of hydrolysed collagen dissolved in about 200ml of water.

First I put the cup of water on my digital scale (which measures in 0.1g increments) then I add exactly 10g of collagen and stir it with a spoon until it dissolves.

As the collagen dissolves, the total weight always gradually decreases by about 1.5g - 2g in total. If the total weight of the cup, spoon and water is 300g, when I add the collagen, it becomes 310g, then as it dissolves over the next 15 seconds it decreases to about 308g. All I've done is stir it.

I can't see how this is due to evaporation since I can leave the pure water on the scale for 5 minutes beforehand and the weight doesn't change; but as soon as I stir the collagen in it always decreases.

What's happening?


texts: Exact meaning of "degree of crosslinking" in polymer chemistry

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In the ion-exchange chromatography literature, a term "degree of crosslinking" appears frequently. Ion exchange resins are typically made from divinylbenzene and styrene. One of the stated characteristics is the "degree of crosslink" which is often stated as 5% to 55% crosslink with DVB.
The term degree of crosslink does not appear in the IUPAC's glossary; yet it is a very well established terminology. What is the physical significance of, say, 55% crosslink when the manufacturers quote this number? Is it simply the mole percent of DVB present in the polymer?
I am looking for its exact definition from a reliable source but it seems to be elusive.


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In the reaction CH3-CH2-Li + ethyne

Do the lithium and a hydrogen from ethyne just switch places? And how would i draw the curved arrow notation for this? I'm assuming from the C-Li bond in one to the C-H bond in the other and vice versa? Will upload a pic of my attempt when I get home.


texts: Guess the shape and phase of the MOs of butadiene using LCAO and Hückel's method?

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I used Hückel's method along with a Linear Combination of Atomic Orbitals (LCAO) to calculate an estimate for the orbital energies of cyclobutadiene ($\ce{C4H4}$) and butadiene ($\ce{C4H6}$). For butadiene, I ended up with the result

$E = \alpha \pm 1.62  \beta$ and $E = \alpha \pm 0.62 \beta$,

where $\alpha$ and $\beta$ are both negative (and are the Coulomb integral and the exchange integral, respectively). I'm fairly confident with the method and interpretation of these integrals so far, but I don't know how to use these results to "guess and draw" the shapes and phases of the molecular orbitals, and I'm also not sure how to tie in what $\alpha$ and $\beta$ represent.

As I understand things, in these molecules, hybridisation of the orbitals occur and $\mathrm{sp^2}$ orbitals form, taking up three electrons from each carbon atom and leaving one electron left over in the third p orbital. This p orbital is the one I assume is portrayed in the below images.

Could someone please give me a hint towards the following:

relating the molecular orbital shapes/phases with the Coulomb integral (overlap of one carbon's electron wavefunction with a neighbouring carbon's potential) and the exchange integral (the overlap of two electrons' wavefunctions in the field of one of the carbons
how to get any sort of information about the phases of the different orbitals. I understand that $E = \alpha + 2\beta$ will have the lowest energy, as both $\alpha$ and $\beta$ are negative, but how does that correspond to the phase configurations shown below? Why do the size of the circles in the first image vary?

Note: I've been sent here from the Physics Stack Exchange, please be nice. :) Thanks for any help! This is my first post so please also let me know if the posting etiquette passes muster.

Sources: First image, second image


texts: When do lone pairs on nitrogen contribute to aromaticity?

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I've been told that 1,2,4-trimethyl-1H-imidazole is aromatic. As it has four obvious pi electrons (in the double bonds), I assumed that it was anti-aromatic as opposed to aromatic.

I've been operating under the assumption that a nitrogen does not contribute its pi electrons to the aromaticity count for Hückel's rule unless it is attached to a hydrogen. Does the nitrogen with a methyl group here donate its pi electrons to the count?


texts: How to make permanent ink that appears after some time?

texts: I'd like to ask,  how to make permanent ink, that will be invisible when used, but after like 30 minutes it will appear (preferably dark color)? Thanks.


texts: Maximum pressure that can be produced by a combustion reaction

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Multiple-chamber artillery can launch a projectile with energies much higher than single-chamber guns.  I'm interested in setting a fundamental upper bound on the energy that a chamber (of a known volume) can impart to a projectile.  This would, for example, set a limit on the needed volume for a sub-orbital gun (given a projectile mass).  Since the pressure drop-off (like with single-chamber) isn't a constraint, the kinetic energy would be theoretically limited by pressure times volume.  But you can't possibly achieve infinite pressure with any chemical reaction.

For that limit, some sources claim that pressures of 60,000 psi can be achieved.  Coming from a physics perspective, I understand that a reaction should have a defined energy associated with an individual molecular transition.  We've had related questions on physics stack exchange, but my thinking is that chemical equilibrium may be be a necessary tool.

If we ignore reaction kinematics, I believe that the maximum pressure that a reaction can achieve is limited by two things:

the density of the reactants before reaction and
the energy of the reaction

Given this, we could simply model the reaction with ideal gas assumptions, resulting in simple algebra.  But I think this is wrong.  Higher pressure would push the reaction to incomplete combustion.  From a chemistry perspective, is there any theoretical maximum pressure that we could restrict all combustion reactions to?


texts: Particle size of oxides of nitrogen and sulfur pollutants and HEPA filters

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I am thinking about buying air purifier as pollution is high in my city.
Going through the specifications of HEPA filters, I found that they block particulate matter of 2.5. PM 2.5 contains dust and other fine particles.
Googling tells me that their size is around 2.5 micrometers.

My question is: Do pollutants such as sulfur oxides and nitrogen oxides (and related compounds) fall into this category, specifically in regards to size?


texts: What is the meaning of the "colon" notation in chemical formulas?


texts: Effectiveness of getters to keep gasses sulfur free

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My engineering task poses a problem with sulfur damaging electronic components. There are enclosed gas volumes which contain sensitive electronic devices as well as NBR sealings and gaskets. The sealings can evaporate sulfur in different compounds, the most dangerous seemingly beeing hydrogen sulfide. I have two options protecting the electronics.

geometric separation by confining the electronics in separate housings. This might be possible but is very difficult due to the geometry of all devices.
removal of evaporating sulfur compounds from the air surrounding the electronics.

I want to evaluate option 2.

My first question is about the getter material in general. I know of only two usable materials: silver and zinc carbonate. Are there other usable (solid) materials?

Silver could be applied as a foil inside the common housing exhibiting a considerable surface to the gases. Zinc carbonate must be applied in a permeable containment like a paper or Tyvek bag, similar to desiccant bags.

I assume, the number of sulfur compounds which can eventually evaporate from some sealings, is rather limited. But the evaporation will probably never cease to happen. Hence the getter must be active for the whole product lifetime. Is there any mechanism that could prevent this? E.g. oxidation of silver or weird reactions of zinc carbonate?

I understand by using a getter, I cannot prevent the effect of the detrimental gasses on the sensible equipment in total, but I can limit concentration and time to extend the period until the destruction of the electronics. I assume, that by exposing a silver foil to the gas mixture with a surface n-times as big as that of the semiconductor, the resorbed sulfur will at least n-times as much as that of the semiconductor? So if I increase the surface of the silver foil the amount of sulfur likely absorbed by the semiconductor will decrease by the same factor, given a constant evaporation rate (ev=const [mol/s]).

I guess this is difficult to formulate for a bag of zinc carbonate, isn't it? Might the surface of the bag correlate the same way?

It seems, after installing sulfur sources and sinks, an equilibrium will establish. Given a constant gas concentration around getters and sensitive equipment, I want to make further considerations. Silver surfaces can bind sulfides directly while the housing of electronics has to be traversed by diffusion. Is it fair to assume that due to the presence of uncovered getters the mass flow by diffusion through the housings is reduced by much a greater degree than just by the proportion of surfaces between getter and electronics? Can I hope that this reduction is one or more orders of magnitude?


texts: Why is the hydbridization of the N atom (rightmost) in diazomethane sp and not sp2?

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Why is the hydbridization of the $N$ atom (rightmost) in diazomethane $sp$ and not $sp^2$ ?

Most books claim that the negative charge (electron pair) of nitrogen can participate in resonance and is placed in a pure $p$ orbital. However, according to the general rule the hydribization number (number of sigma bonds + number of lone pairs) of the $N$ comes out to be $3$ implying ($sp^2$). However, according to several books the hybrdization is $sp$ and not $sp^2$. Why is it so?


texts: Chair conformations of cyclohexane with two substituents

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I have been studying the chair conformations of cyclohexane but I get confused when it comes to two substituents.

I came across an example, in which the one substituent is the ethyl group (Et) and the other one is methyl (Me).  The ethyl is drawn like a solid wedge, whereas the methyl is drawn like a dashed wedge. As far as I  know, I have to draw the chair and then the equatorial positions and the axial ones. I thought that since the bigger substituent is the ethyl group, that it would be better in a equatorial position and the methyl would be better in a axial position. But the example, draws the ethyl group in an axial position and the methyl in an equatorial position

Why is that?I really don't understand.

Thank you.


texts: Why would sulfuric acid turn gray/black?

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About 2 years ago I purchased 2 liters of 98% concentrated sulfuric acid. It's in a standard poly bottle with leakproof lids, and originally was clear. Recently I noticed the acids have turned a dark gray; almost black color. They have both never been opened.

I suspect there was something in the lid that was eroded by the acid, but is there any other reason sulfuric acid would darken over time?


texts:
In the volumetric estimation of calcium in a given solution as calcium oxalate. We convert the calcium oxalate to oxalic acid by dissolving the former in hot (~70 °C) 2 N sulfuric acid solution. This is titrated against $\ce{KMnO4}$.

The reaction would be
$\ce{H2SO4 + CaC2O4 -> H2C2O4 + CaSO4}$

The calcium sulfate formed is normally not soluble in water. But here we get a clear solution which we titrate against $\ce{KMnO4}$.
Why does the calcium sulfate not precipitate in the solution?


texts: I noticed the fact that all the hydrides of the elements belonging to group IV has bond angle 109.5° while in group V it varies from 107.3° for $\ce{NH3}$ to 91.3° for $\ce{SbH3}$. Similarly we see in group VI that water has highest bond angle then it significantly decreases to 89.5° for $\ce{H2Te}$. Is there any specific reason for hydrides of group IV metals to have remarkably equal bond angles, and other groups to have varying angles?


texts:
So I have been working on a project for a while, and there is one mechanism that I need a little bit of advice about.

The project is chemical-biology based, so don't be deterred :)

Theoretically, by this point in the experiment:

I put cells (let's say lymphatic or endometrial) into stasis, through means of lyopreservation, and now, I have brought them out of stasis, through exposure to a sucrose (trehalose)-based medium.

Now I am attempting to chemically detect mitotic growth within the cells, how can I do this?

This is where the chemistry comes in: My first thought was to use a chromatic indicator that would fluoresce or irradiate in response to mitotic acceleration, but I have not yet found a suitable chemical. In research, I found that a similar experiment had been done in bacteria, and the chemical dimyristoylphosphatidylcholine (1,2-Dimyristoyl-sn-glycero-3-phosphocholine) had been used. Would this work in mammalian cells? Another idea was to use a chemical that detects the unnatural growth from the spindle fiber and centriole point of view, reacting when the centrioles entered the phase to replicate. I have been unable to find any chemicals that make use of the replication of centrioles, or the spindle fibers, so I need ideas.

To summarize: Does anybody know of any biochromatic indicators that react through detection of rapid, mammalian, mitotic growth? Not necessarily cancerous and uninhibited, but rapid meaning 'a speed of mitosis that is faster than the norm.' Preferrably, the indicator would be able to stay in stasis for extended periods of time.

If such an indicator is not available (or you do not believe so) then does there exist a biochromatic indicator that reacts in the presence of any sort of cell division?

Is there a way to chemically detect cell division?

I am welcome to all ideas.

(figure source / chemspider.com)


texts: I have a solution of citric acid, tartaric acid, water and glucose. How do I find the concentration of the citric acid present in the solution?

texts: If I try to find the concentration of citric acid through back titration or reverse titration, the base I would use, like NaOH, would react with both acids to form sodium citrate and sodium tartrate, which are both white compounds that are colourless in aqueous form. How do I find the concentration of citric acid?


texts:
I am currently studying the textbook Infrared and Raman Spectroscopy, 2nd edition, by Peter Larkin. In a section entitled Symmetry: Infrared and Raman Active Vibrations, the author says the following:

In a molecule with a center of symmetry, vibrations that retain the center of symmetry are IR inactive and may be Raman active. Such vibrations, as shown in Fig. 2.12, generate a change in the polarizability during the vibration but no change in a dipole moment. Conversely, vibrations that do not retain the center of symmetry are Raman inactive, but may be IR active since a change in the dipole moment may occur.

For molecules without a center of symmetry, some vibrations can be active in both the IR and Raman spectra. Molecules that do not have a center of symmetry may have other suitable symmetry elements so that some vibrations will be active only in Raman or only in the IR. Good examples of this are the in-phase (symmetric) stretches of inorganic nitrate and sulfate shown in Fig. 2.13. These are Raman active and IR inactive. Here, neither molecule has a center of symmetry but the negative oxygen atoms move radially simultaneously resulting in no dipole moment change. Another example is the 1,3,5 trisubstituted benzene where the C-Radial in-phase stretch is Raman active and IR inactive.

What is the precise meaning of "in-phase" (and "out-of-phase") in this context? I understand the concept of phase in the context of waves (physics), but their use here, as related to molecules and vibrational spectroscopy, is unclear to me. I would greatly appreciate it if people would please take the time to explain this, including the associated mathematics, so that I have a more substantive understanding of what this means in this context.


texts: Is there a melting analogy for evaporative cooling

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Evaporative cooling can occur in an air-liquid water system initially at the same temperature. If the air is not saturated with water vapor, the liquid water will evaporate until the partial pressure reaches its vapor pressure. In this process, the temperature of the liquid water decreases. This is because there is a distribution of speeds among the water molecules, and only the water molecules moving fast enough with enough kinetic energy to break their hydrogen bonds will escape into the gas phase. This selection based on kinetic energy leaves the slower molecules in the liquid phase, thereby lowering the temperature of the liquid.

My question concerns the parallel process of an ice cube melting. If the ice cube is in thermal equilibrium with a super-cooled salty brine, say -20 degrees C, there will still be a distribution of speeds among the water molecules in the ice lattice. Since only the fastest moving water molecules in the ice lattice will have enough energy to break the hydrogen bonds, would the melting of the ice cube cause a similar cut-off of the speed distribution curve and lower the ice cube temperature? If the volume of the brine solution was large enough so that the brine temperature doesn't rise much, could there be a situation where the ice cube both melts and also get cooler?


texts: How to find partial pressures of gases only given their percentages?

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How do I find partial pressures if I am only given their percentages? Where do I begin?

Example: Assume $\ce{O}=21\%$ , $\ce{N}=78\%$ , $\ce{Ar}=1\%$ by volume. How would I calculate the partial pressures if total pressure is $\pu{1 atm}$.


texts:
From the table of the saturated vapor pressure of the water, at 20 degrees C, the saturated vapor pressure is 2.3388 kPa.

My question is: If I put a water in a closed container, and I pressurize the container up 2.3388 kPa (above the atmosphere pressure) by nitrogen or any other inert gas, will the water evaporate, or it will never evaporate because we are already above its saturated pressure?

In other words, is the saturated vapor pressure of a substance affected only by the partial pressure of the substance itself, or by the amount of pressure above its surface regardless of the substances cause that pressure?


texts:
Should the benzene group be taken as a substituent, so as to select the longest C atom chain?
In what cases is it taken as as a substituent?


texts: How does aniline react with HNO3 in the absence of sulfuric acid?

texts: How does aniline react with $\ce{HNO3}$ in the absence of sulfuric acid? I read that nitration occurs at slow rate, but it didn't explain how nitronium ion is formed.


texts:
Why does scandium has +2 oxidation state unstable? It only has +3 oxidation state stable.
Scandium has outermost electronic configuration as 3d¹4s². Why it does not lose two 4s e- only instead of all three?


texts: How is drift due to static electricity eliminated from an analytical balance?

texts:
I've recently encountered a problem when using an analytical (0.1 mg accuracy) scale to determine the mass of a sample of ferrocene powder. The reading in the balance seems to drift either upwards or downwards when I drop some of the powder in an erlenmeyer flask. The reading stabilizes when I add water to form a solution.

I've heard that static electricity might cause this kinds of problems when measuring powders so I suspect this is the case here, because the problem only appears when I add the ferrocene powder. I've try reaserching some ways to get rid of the problem, a static gun seems to work in some cases (no idea if it would work with a powder though) and I've heard that air ionisers also work, but don't have access to either of these.

Although this is the first time I've encountered this situation, I've heard its pretty common, so what do people usually do to get rid of the problem in a cheap manner? Is there an easy solution?

I'm using gloves to operate the scale, which I've been told to do in order to keep the flasks clean of oil from my fingers. Can the gloves be worsening the problem? What can I do about that?


texts: I was wondering is someone could please help answer this question for me. I was recently reading the ingredients on my toothpaste container, and one of the compounds in it was 'Sodium Pyrophosphate'; what does the 'Pyro-' prefix mean? I see it elsewhere but I've never come across such a nomenclature such as this. What does it mean in terms of Chemistry?


texts:
I know that complete oxidation of primary alcohols produces acids:

$$\ce{R-CH2(OH) ->[\ce{[O]}] R-CH(OH)(OH) ->[][-\ce{H2O}] R-CHO ->[\ce{[O]}] RCOOH}$$

I wonder if that is the case of methanol. Why doesn't formic acid complete oxidation to $\ce{CO2}$?

$$\ce{HC(O)OH ->[\ce{[O]}] C(O)(OH)(OH) ->[][-\ce{H2O}] CO2}$$

Note: by [O] I mean an oxidizing agent as $\ce{KMnO4}$ or acidified potassium dichromate.


texts:
I am studying the very BASIC introduction of catalysis in general chemistry and encountered an example of a heterogeneous catalyst, which is catalytic hydrogenation of alkene into alkane using Pt/C or Pd/C, I have some questions:

why sometimes we need to use Pt, and sometimes we need to use Pd? Are there any differences in reactivity, or just purely depends on what is at hand?

I know the addition of activated carbon powder is to increase the surface area between reactants and catalyst. However, the carbon powder isn't added all the time when doing different heterogeneous catalysis reactions, why is it so if it is beneficial?

Bond dissociation energy of H2 = 436kJ/mol. But when H2 is adsorbed on the metal surface, the bond is broken. How come this simple step can break this strong bond? I suspect the metal-H bond formed is stronger than H-H bond, which means it is favorable, but I still have no idea where does the 436kJ/mol energy comes from.

Thanks


texts:
This is the iron complex in question:

$\ce{Fe2Cl6[H2O]5}$

I'm pretty sure according to the nomenclature it should be: pentaaquahexachloroiron(III) but I wanted to check somewhere to be sure.


texts: What happens to the chlorine in epichlorohydrin when a two-part epoxy is air-cured?

texts: Where does the chlorine go? Does it evaporate as a by-product or does it remain in the epoxy? I'm using a two-part resin and hardener and curing them at room temp. The resin is bisphenol-A-epichlorohydrin, and I believe the final cured epoxy does not have chlorine as a part of its main structure. I need to know the whereabouts of Cl because I'm trying to study neutron interaction with materials in my detector, and I suspect there's some chlorine in there but not sure entirely.


texts: Calculating amount of base needed to achieve a specific pH in a mixed ethanol-water solvent

texts:
I'm looking for some way to calculate how much base I will need to add to an unbuffered solvent consisting of a mixture of ethanol and water in order to basify it to a specific reading (10) on an a pH probe calibrated with an aqueous standard.

I have several mixtures of ethanol and water, ranging from about 85% ethanol to nearly 100% ethanol, and I plan to basify these solutions.  Using the method defined by ASTM D6423, one of these solutions was measured to have a pHe of 5.2 due to the presence of some acidic species, but I don't expect these species to act as buffers.

Now, I'm aiming to get these solutions to a pHe of approximately 10, and in practice I'm just going to add the base and check the pHe as I go.  However, motivated by the fact that I'll potentially need to do this on quite a large scale at some point, I'm curious if it's possible to put a mathematical backing behind this.

If this were a pure water solvent, I would calculate $[\ce{OH^-}]=10^{-8.8}$, since the self ionization constant of water is $K_W = 10^{-14}$ and $K_W \approx [\ce{OH^-}][\ce{H^+}]$.  From there it's relatively simple to calculate the amount of base I should need to add to reach $[\ce{OH^-}] = 10^{-4}$, resulting in a pH of 10.

If this were a pure ethanol solvent, I would do something similar using the self ionization constant for ethanol, except nobody has published one as far as I can tell.  This answer also failed to find one.  The Wikipedia page on the leveling effect depicts ethanol having a wider acid-base discrimination window than water, so I would expect $K_{EtOH}$ to be somewhat higher than $K_W$, but no numbers are given.  I checked the source of the graphic as well, and they also give no numbers.

Finding $K_\ce{EtOH}$ wouldn't even fully solve the problem though, as there is a non-negligible amount of water in the solvent.  The only source I was able to find discussing pH in mixed-solvent system was this one, which discusses using a correction factor ($\delta$) to allow the measurement of something analogous to pH in mixed solvent systems using an electrode calibrated in an aqueous standard.  However they only determined this correction factor in solutions of up to about 72% ethanol, and the relationship is decidedly non-linear, as shown by this plot:

We know that when our probe reads 10 we'll get good results with the rest of the process, so presumably this means in the math I would want to target a pH of $10+\delta$, were $\delta$ known.

This is as far as I've been able to get with my own literature search.  If anyone here has any insight into this problem I would greatly appreciate it!

EDIT: Additional detail.  I just had some 200 proof ethanol measured by the ASTM D6423 method, and the pHe was measured as 6.5.  This is counter to what I expected.  I expected it to have a pHe greater than 7 since pure ethanol should be a somewhat weaker acid than water based on everything I've read.  I'm not certain if this is helpful information at all, but it's another data point.


texts:
In the synthesis of Illudinine by Dudley et al., steps are performed which include a tandem base catalyzed fragmentation followed by a Knoevenagel-type condensation, as shown in the picture below. However, why isn't the fragmentation product $3$ received immediately after treating with DIBAL-H? In the intermediate received after the installation of the triflate group, can't the DIBAL-H added in step 2 push a hydrogen atom in to form a tetrahedral intermediate with the top carbonyl group, which would then collapse to form an aldehyde, simultaneously completing the fragmentation?

DOI for the paper


texts: membrane for a reverse osmosis desalination experiment

texts:
We are second year cram schoolers , we are currently working on a project tackling water desalination by reverse osmosis and are required to do an experience. During the process, we encountered some difficulties regarding applying pressure and the fabrication of membranes . Given our unfavorable circumstances (low budget , lack of material ), we were wondering if someone could give us some insights on how to proceed. Although , we have tried to diy one with accessible materials and this is what we could come up with so far .

First ,we took an unglazed flowerpot and we filled its hole with cement, we filled it with a 0.1 mol / L potassium ferrocyanide solution. Simultaneously, we soak it in a 0.1 mol / L copper sulphate solution. After waiting several hours, the two products are going to spread in the pores, one from the inside, the other from the outside. In the middle of the pores, a chemical reaction had taken place , forming a precipitate of copper ferrocyanide which closes the large pores and transforms the pottery into a semi-permeable membrane. Finally, we rinsed the pottery well with water, and left it to soak for several days so as to remove the initial reagents.

However, we didn't meet our expectations and we don't know what is it that we're doing wrong . How thick should the cement layer be ? what are the rinses so as to remove the reagents ? and how could we simulate the pressure in a compartment ? and is there any other ways to make a membrane to work with ?


texts: Total valence electrons in a rhodium complex

texts:
How many valence electrons does the following metal complex have?

I have read that benzene donates 6 electrons to a transition metals valence electrons. Rh has 9 from itself, and H and Cl add 1 each; hence in this assignment above I thought one would end up with: 9+1+1+2+2+6=21 valence electrons.
However, the given answer is 16. How is that so?


texts: How was it concluded that the H3O+ rather than H+ is the "acid" ion?

texts:
I suspect that initially, scientists believed that the acid ion was $\ce{H^+}$ since $\ce{H2}$ is released through electrolysis, right? But what experiment was done to change the standpoint to assume that it is instead the $\ce{H3O^+}$ ion?

Or perhaps there's both $\ce{H^+}$ and $\ce{H3O^+}$ ions?


texts:
This is a question that has been bugging me for over 15 years!
In high school while studying elements our teacher showed us a clear white rock or element.

It was simply flat on both sides but when placed on a sheet of paper would transfer the letters from the page beneath it to the top surface of the rock.

I remember being amazed by this rock, but could not remember what it was.
Now I am working on a creative project and would love to see if I can incorporate the material in my design.


texts:
I have seen some books indicated sigma bond has C2 symmetry. I understand pi and delta bond change their signs about C2 and C4 rotation about bond axis, but I don't  understand why sigma bond has C2 symmetry not C∞ about its bond axis.
The example of the sigma bond came from two 1s orbitals.


texts: Electrochemistry conditions for voltage to increase in a galvanic cell

texts:
I understand that increasing the concentration of reactants in a galvanic cell generally causes the voltage of the cell to increase. But is that really the case always?

Consider a standard cell of zinc and copper, 1 M and 1 L each solution of copper nitrate and zinc nitrate in each half cell. Another cell, increased the concentration of copper nitrate to 4 M, but added 0.25 L of it and kept the same zinc nitrate 1 M and 1 L.

This way I increased the concentration, but the amount of substance is the same. Does the voltage increase in the new cell? I would really appreciate someone to explain to me the specifics of what causes the voltage of a cell to increase based on the reactants


texts: Nernst equation: half cell vs overall reaction

texts:
Can the Nernst equation always be applied to the overall redox reaction as opposed to only half cell reactions?

For example, in the following silver-silver chloride electrode: $$\ce{Ag (s)|AgCl (s)|Cl- (aq)}$$ rather than applying the Nernst eqution to the half cell reaction $$\ce{AgCl + e- -> Ag + Cl-}$$ can I apply it to $$\ce{AgCl -> Ag+ + Cl-}$$

The answer is the same for the question I was trying to solve (whether I use the overall reaction or the half-cell reaction), but I was wondering if this was just a coincidence or if it was the same.

If they are the same, are there any other factors I should consider such as whether or not the electrolyte fully dissociates in the given conditions?


texts: How did chemists in the 18th century learn that magnesium gain mass when it's burned?

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Crucial to disprove the phlogiston hypothesis was the observation that magnesium gains mass when burns.

But how was this observation made in the 18th century? Is there any way this property of magnesium would be obvious to a layman today?


texts: Why does the emission of dansyl group diminish with time in this experiment?

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I don't know how to make sense of this. I what is happening when an enzyme (carboxypeptidase, which contains tryptophan as its only chromophore and uses a Zn(II) ion in its active center) hydrolises a dansyl-Gly-Phe peptide. The enzyme and the peptide are mixed and the reaction is studied by fluorescence measurements: the whole reaction is excited with 280 nm light, and emissions at 310 nm (for Trp) and 550 nm (dansyl) are studied (see the two graphs below).

All I know is that this is an energy transfer process, which is known to lose effectiveness following a $1/r^{6}$ law regarding distance between emitter and absorber. Also, I know how Trp and dansyl emission spectra overlap, and I know that the enzyme is active but does not show fluorescence if Co(II) is used instead of Zn(II). My guess is that Trp emits light which is absorbed by the dansyl group due to the overlap in their emission/absorbance diagrams, but I don't see why the dansyl emission graph would go down w/ time. Isn't the number of dansyl groups constant, even if they are not bonded to the peptide in the end.


texts: How to list elements according to their radius? For example Ag, Cd, Au Can you check the accuracy of these sentences I've created?

texts: I've asked a similar question before, but now I want to find out the real rule. Pleas tell me if my interpretation is correct: Cd, Ag , Au (increasing ray order). This happens because although we know that period and group effect the radius length, most important one is the group. So firstly we should list the elements according to their group and then list them in the same group... For example Zn, Cd (same group), then Pd, Pt, (same group), then Ph, ir (same group). From our lesson we know that from Cd to Hg the ray doesn't change but I think when we have to list them we should consider that it grows a little. Are these statements right? If not, please help me clear the concept. I'm not a native speaker of english, so I may not express correctly in some occasions


texts: How to obtain pure aniline from a mixture of phenol and aniline?

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There is a mixture of aniline and phenol. I need to obtain (just the procedure) pure aniline.

So I think the mixture should heat with Zn powder(to convert phenol to benzene) and then I thought to synthesize aniline from benzene.

I am not sure about this method?

Please help me


texts: What is the correct equation for calculating the electric potential of an electrochemical cell?

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When I'm studying electrochemistry, we were given an equation that all chemistry students are familiar with, which is:

                    Ecell = Eoxidation - Ereduction

However, when I came to study electroanalytical methods, I came upon this equation:

          Ecell = Eoxidation + Ejunction - Ereduction  - Eelectrode

where Ejuntion is the uncertain potential produced from the salt bridge and the Eelectrode is the potential produced from the reference electrode used in the experiment.

My question is, is this the real equation when calculating problems for an electrochemical cells? I'm thinking that they probably cut Ejunction out of the equation because it is impossible to know the exact value for it. In addition, I think that they cut out the Eelectrode in the equation because most of the experiment data came from a SHE electrode where Eelectrode = 0.00 V.


texts: How do you track Iodine on a black surface?

texts: While spraying with starch solution seems to be standard procedure, blue-black colouring seems not to stand out from a black (charcoal) surface.


texts: Consequences of using reagent preserved with sodium azide on gold film

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I am running experiments using reagents preserved with 0.1% sodium azide, which are applied to a gold film.  Unfortunately, there are very few options for using reagents without sodium azide.

I understand that sodium azide reacts with gold to form heavy metal azides, which are explosive.

I would like to know:

How long will it take for sodium azide to react with gold?
Generally, what is going to happen to the gold film?
Any other info you can think of


texts: Are there any other elements that get less dense in their solid state?

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I was learning about how water, because of its hydrogen bonds, actually gets less dense as it goes into its solid state - I was just wondering, what other elements do this? Are they similar to water?

P.S. I want to make sure that I understand why ice is less dense than water in its liquid state, so please correct me if I am wrong.

In water, the hydrogen bonds have the ability to move around and bounce with other hydrogen bonds. They also have the ability to break and reform. Their ability to move around and bounce around allow them to be more 'closely knit'. But, as they get cooler, they, the molecules, loose their kinetic energy and thus stop moving around and become more framed and rigid. They loose the ability to come closely together. And thus, ice is less dense.

What I don't understand also, is why making water cold makes the hydrogen bonds spread out. Why don't they just freeze in the position they are in, instead of spreading out?


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Methyl chloride belongs to the $C_{3\mathrm{v}}$ point group. This is because it has a $C_3$ axis down the $\ce{Cl-C}$ bond.

However what I do not understand is how it has three vertical mirror planes? It has three planes down each of the $\ce{C-H}$ bonds, but don't these bisect a bond making them dihedral planes? Although I'm wrong I can't fathom why it isn't a $C_{3\mathrm{d}}$ point group. I have used a molecular viewer to visualise it but I still get the vertical mirror planes bisecting a bond...


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I asked this question to my teacher a few days ago. In a reaction such as

$$\ce{NH3 + H2O -> NH4+ + OH-},$$

$\ce{NH3}$ is a Lewis base, but is $\ce{H2O}$ a Lewis acid?

He said that it isn't. Now I fail to see the reason why. Can someone explain?