texts: What exactly is a 'chiral centre' in a carbon compound?

texts:
The typical progression (in books, YouTube videos) of explanation of chiral carbons in a compound is as follows:

Chiral compounds are non-superimposable by their mirror-image;
It is easily seen that only carbon atoms with all substituents different are chiral;
In a carbon compound with more than one atom, (2.) is exactly how you check for chirality;
It isn't necessary for a compound to be chiral despite having chiral carbons.

It seems to me that something between (2) and (3) is being eaten up. How does a chiral carbon in an chiral compound show the non-superimposability property? How does it satisfy the basic definition of chirality?


texts: Determining a molecular formula of the catalyst for polymerisation of butadiene

texts:
I've got the following question in a workbook which I need to solve:

  A $\pu{50 g}$ sample of an experimental catalyst used in the polymerisation of butadiene is made up of $\pu{11.65 g}$ of $\ce{Co}$ and $\pu{25.7 g}$ of $\ce{Cl}$. If the molar mass of the compound is $\pu{759 g/mol},$ find the molecular formula of the catalyst.

I attempted to first find the percentage by mass of each given element by dividing their masses ($\pu{11.65g}$ and $\pu{25.7 g},$ respectively) by the mass of the entire catalyst $(\pu{50 g}).$ From there, I divided both percentages ($23.3$ and $51.4)$ by the smallest one, and multiplied the results $(1$ and $2.2)$ by $5$ to get two whole numbers. The formula I ended up with was $\ce{Co5Cl11}.$

Now that made sense to me, but somehow the correct answer is $\ce{Co3Mo2Cl11}$. I don't understand how I'm supposed to figure out that $\ce{Mo}$ is required? Could somebody please shed some light on this for me?


texts: Finding mass percentage of components of a solid mixture

texts:
A workbook question asks:

  $\pu{2.184g}$ of a solid mixture containing only $\ce{K2CO3}$ ($\mathrm{FW = 138.2058}\pu{ g/mol}$) and $\ce{KHCO3}$ ($\mathrm{FW = 100.1154} \pu{g/mol}$) is dissolved in distilled water. $\pu{31.29mL}$ of a $\pu{0.742\!M}\ \ce{HCl}$ standard solution is required to titrate the mixture to a bromocresol green end point. Calculate the weight percent of $\ce{K2CO3}$ and $\ce{KHCO3}$ in the mixture.

I started this problem by finding the amount of moles of $\ce{HCl}$ added to the titration, assuming that the solution was completely neutralized at the endpoint.

In $\pu{0.03129L}$ of a solution of $\pu{0.742\!M}\ \ce{HCl}$, there are
$$\mathrm{0.03129\; \pu L \times \frac{0.742\; mol\; \ce{HCl}}{\pu L} = 0.0232\; mol\; \ce{HCl}}$$

Then I set up the balanced equations:

$$\ce{2HCl_{(aq)} + K2CO3_{(aq)} -> 2KCl_{(aq)} + CO2_{(g)} + H2O_{(l)}}$$
$$\ce{HCl_{(aq)} + KHCO_{3(aq)} -> KCl_{(aq)} + CO2_{(g)} + H2O_{(l)}}$$

This should indicate that the $\ce{HCl}$ will combine with the carbonate and bicarbonate in a 2:1 ratio, favoring the carbonate, since two moles of HCl are required to neutralize one mole of carbonate.

Then:

$$\ce{\pu{0.0232mol}\ HCl \times \frac{1\; mol\; CO_3}{2\; mol\; HCl} = 0.0116\; mol\; CO3}$$

$$\ce{0.0232\; mol\; HCl \times \frac{1\; mol\; HCO_3}{1 \pu{mol} HCl} = 0.0232\; mol\; HCO3}
$$

And:

$$\ce{0.0116\; mol\; CO3 \times \frac{1\; mol\; K2CO3}{1\; mol\; CO3} = 0.0116\; mol\; K2CO3}$$

$$\ce{0.0232\; mol\; HCO3 \times \frac{1\; mol\; KHCO3}{1\; mol\; HCO3} = \pu{0.0232\; mol}\; KHCO3}$$

Converting moles to grams:

$$
\ce{0.0116\; mol\; K2CO3 \times \frac{138.2058\; g}{mol\; K2CO3} = 1.60\; g}
\\
\ce{0.0232\; mol\; KHCO3 \times \frac{100.1154\; g}{mol\; KHCO3} = 2.32\; g}
$$

When I add these masses together, I get $\pu{3.92 g}$, which is greater than $\pu{2.184 g}$.

Where did I go wrong?


texts:
I am having one doubt in weight percent standard state...Please see the quote(Taken from the legendary thermodynamics book by David Gaskell):

If deviations from Henry's law occur below 1 wt %,then the procedure is to extrapolate the Henry's law line upto 1 wt% and conceive that as standard state,which will be hypothetical.But it does not matter for thermodynamic treatment.

Firstly,why are we assuming a negative deviation here.I even am not motivated how to judge between positive and negative deviation.Secondly,Could someone explain the quote with reference to the diagram provided?I do not understand a single thing between the quote and the picture.


texts: Why do most explosives have symmetrical chemical structures?

texts:
I was just turning the pages of my chemistry dictionary, when I found the structure of TNT (Trinitrotoluene):

...there after I got interested in its symmetry as an explosive, and started looking for structures of other explosive compounds and found that almost all of them have very symmetrical structures.... Here are some that I found:

RDX

HMX: High Molecular Weight RDX (cyclotetramethylene-tetranitramine)

PETN [Pentaerythritol tetranitrate (PETN)]

Heptanitrocubane

HHTDD (hexanitrohexaazatricyclododecanedione)

TATB, triaminotrinitrobenzene or 2,4,6-triamino-1,3,5- trinitrobenzene

There are many others which can be found here: wikipedia/chemical-explosives

I wonder why they generally tend to be so symmetrical (as compared to any other random non-explosive molecule)?


texts: When expressing a quantity, do the non-significant figures determine whether you round up the last significant figure?

texts:
I had thought that the non significant figures determined whether the least significant figure was to be rounded up. For example, given the number $9.1145$, if the number is to be expressed as three significant figures, then, I had thought that, it would be expressed as $9.12$.

However, I noticed that in one of my chemistry professor's calculations in which the quantities were expressed as significant to three figures, she expressed $8.125 \times 10^2$ as $813$. In another calculation she expressed $9.1145 \times 10^{-3}$ as $0.00911$. However, it seems to me that $0.00912$ is the correct expression of $9.1145 \times 10^{-3}$, as the $5$ requires rounding up the $4$, which requires rounding up the least significant $1$ to $2$.

Is there a rule for rounding that my professor is following that I don't know?

(Note: this isn't a homework question, but the homework tag seemed to be the most appropriate one.)


texts:
I was doing lewis structures and i came across a question asking the structure of POCl3. Here, the answer is a tetrahedral shape with P as central atom connected to 3Cl atoms by a single bond and 1 oxygen atom by a double bond. The valency of P is 3. So, it needs 3 electrons to get the nobel gas configuration and become stable so it could have formed single bonds with 2 cl atoms and single bond with an oxygen atom which would be single bonded to cl atom. Why isn't this structure correct?

And how can P form 4 bonds while it needs only 3? I think it's something related to D-orbital but if it undergoes sp3d hybridisation, it would need 5 bonds. Also, the structure of this compound is tetrahedral and hybridisation of P is sp3. How can this be? How can it form 4 bonds although it has only 3 unpaired electrons? Nitrogen couldn't form such compounds.

I googled about it and could find nothing but the hybridisation and lewis structure. My actual question isn't answered anywhere


texts:
I've looked at the MSDS of a couple of products for removing hardened polyurethane (PU) foam. Both contained only ethanolamine as a dangerous substance, but only between 1-5%. So I'm guessing this might not be the active substance. The Wikipedia page on polyurethane doesn't indicate any degraders (and the page on polymer degradation doesn't mention polyurethane), so what (active) substances are typically used to degrade hardened polyurethane in commercial cleaners?

I also found that some metal acetate-ethanolamine complexes can be used as catalysts for preparing PU foam. So possibly ethanolamine is the active substance or just a catalyst for removal as well. Can someone shed some light on the purpose of ethanolamine?

Example for one of the products I was looking at "Soudal PU remover SDS"; there's also a consumer leaflet for that one which might have additional hints. It's "very active", "odourless", "free of aromatic hydrocarbons", pH 10.5.


texts: How is ATP generated by cellular respiration?

texts:
I learned in a high school level Biology class that the chemical equation for cellular respiration is

$$\ce{6O2 + C6H12O6 -> 6CO2 + 6H2O + ATP}$$

When I looked up the chemical formula for ATP I found that it is

$$\ce{C10H16N5O13P3}$$

Knowing that, that must mean that the first equation becomes

$$\ce{6O2 + C6H12O6 -> 6CO2 + 6H2O + C10H16N5O13P3}$$

One of the products contains nitrogen and phosphorus, but none of the reactants contain those two elements, but there should be in order to produce a product that contains nitrogen and phosphorus. With my high school knowledge, I cannot figure this out. Where do the nitrogen and the phosphorus atoms come from?


texts:
I recently got a glass tea mug. It's has double wall construction with a vacuum insulation (advertised as such). I noticed on the label, it specifically mentioned it's made of borosilicate glass, and to "discard if dropped".

I understand the purpose of making it out of borosilicate glass (thermal expansion when adding hot tea). But what would be the reason for the directions to link the material to needing to discard the mug if dropped (and not cracked or broken)?

Does the fact that it's made of borosilicate mean it's structural or thermal properties might be compromised if it's dropped?


texts: What needs to happen to this: Ca5(PO4)3Cl to get this: CaCl2?

texts:
$\ce{Ca5(PO4)3Cl}$ is a mineral called Chlorapatite

So lets say I have some chlorapatite in my garage, what do I need to do to it so that I am left with Calcium Chloride $\ce{CaCl2}$?


texts: Calculating temperature after adding heat to ice

texts:
If $53.2~\mathrm{kJ}$ of heat are added to $15.5~\mathrm{g}$ of ice at $-5^\circ\mathrm{C}$, what will be the resultant state of matter in which water is present and also calculate its final temperature.

I have done this:

Step 1: Energy required to make ice at 0 Celsius
Step 2:Energy required to make  water at 0 Celsius
Step 3: Energy required to make steam at 0 Celsius
Step 4: Energy required to make steam at 100 Celsius
Step 5:Energy required to make steam at 'x-100' Celsius

Please leave a comment stating if any errors are present. The answer I got is x = 808 Celsius. The correct answer is 303 Celsius.


texts: What is it called when a benzene ring loses a hydrogen atom?

texts:
Does not get substituted by another group it just gets removed  (so not aryl) what is it? Like when two benzene rings lose one H atom each we get arylene? Whats another name for it? I just need the name for when the atom is removed and NOT subtituted
Thank you

Edit: thats not the answer I asked for
I asked what it was called when it lost the hydrogen atom and you say its aryl but thats when a group is in place of the lost atom


texts: Why is the ionization energy of radium higher than barium?

texts: The ionization energy of radium is higher than barium. The reason provided is that occurs fue to lanthanide contraction. But, Radium isnt a member of lanthanide series. How come we say that lanthanide contraction occurs in it?


texts: Jahn-Teller Distortions in Square Planar Complexes?

texts:
A Jahn-Teller distortion is predicted whenever a non-linear symmetric molecule has degenerate orbitals and has unequal electron occupation in those degenerate orbitals. Of course, this most often is discussed in the context of octahedral complexes, but it also occurs in other species - it's a general effect.

When I was teaching inorganic chemistry this term, my students asked if this could occur in square planar complexes. My immediate answer was "yes because, of course, there are degenerate MOs:"

Later, I was trying to figure out what the exact geometric distortion would be. As Wikipedia notes:

  Jahn–Teller theorem does not predict the direction of the distortion, only the presence of an unstable geometry.

I consulted the Walsh diagram posted above from Orbital Interactions in Chemistry by Albright, Burdett, and Whangbo.

My initial inclination would be a "scissor" distortion towards a tetrahedral shape since I know $\ce{T_d}$ complexes undergo similar Jahn-Teller distortions.

Based on the Walsh diagram, depending on the electron count (e.g., $\ce{d^3}$ as suggested by the students) it seems as if you would always have a Jahn-Teller distortion predicted, because you would have at least 1 electron in the $\ce{2e}$ orbitals (the structure would be $\ce{D_{2d}}$ as indicated in the figure.

I understand based on LFSE, such complexes wouldn't be stable, but the question remains: Wouldn't it drop down to $\ce{C_{2V}}$ to break degeneracy? If so, how?

What is the specific geometric Jahn-Teller distortion for unstable (e.g., $\ce{d^3}$ square planar complexes?


texts:
An excess of copper(II) oxide is added to dilute sulfuric acid to make crystals of hydrated copper(II) sulfate.
The processes listed may be used to obtain crystals of hydrated copper(II) sulfate.

concentrate the resulting solution
filter
heat the crystals
wash the crystals

Which processes are needed and in which order?
A 1, 2, 3 and 4
B 1,2, 4 and 3
C 2, 1, 2 and 3
D 2, 1, 2 and 4

I know the correct answer is D. I understand that the solution is first filtered to remove excess copper(II) oxide. Then copper(II) sulfate is saturated by adding excess of it. Then filtered again to remove excess. The last step is wash the crystal. Isn't it needed to heat the solution to get crystal? Also is my understanding so far correct?


texts: Reactivity of boron nitride BN, reaction with Cl2

texts:
lately I've been interested in chemistry of boron and it's properties.. and I am looking for more information. For example I can't really seem to find lot of information about boron nitride BN other than its possible structures. I know that BN is relatively unreactive, and some stated reations found are with F$_2$ or HF, but are described reations with other halogens? With Cl$_2$? I would appreciate even literature recomandations, to find out more.
Thank you, for your time.


texts:
I searched on internet about rocket fuel and the most common fuel is $\ce{KNO3}$ + sugar (rocket candy), but I think that I could use another fuel methods, like using can with gas or using $\ce{HCl + Al}$.

My question is: Which one ($\ce{KNO3}$ + sugar, can with gas or $\ce{HCl + Al}$) gets more performance? Can I increase the performance by increasing the pressure and the durability?


texts: Is there a connection between M1V1=M2V2 and Boyle’s Law?

texts:
Recently in Chemistry 101 we learned about $M_1V_1=M_2V_2$, where $M$ is the molarity of the two mixtures and $V$ is their respective volumes.

The first thing that popped into my mind when I saw this formula is, “Hey, that reminds me of Boyle’s Law from high school physics - $P_1V_1=P_2V_2$ - the relationship between the volumes of a gas at different pressures.”

Is it just a coincidence that these two formulae look the same, or is there a connection between the pressure variable in Boyle’s Law and the molarity variable in the first equation? Are there other formulae which are structured similarly which are connected?


texts: Is it possible to melt HDPE to a point where it has similar viscosity to engine oil?

texts:
I have a few pieces of HDPE that I want to melt and cast into a cube of around  $\pu{5 cm}$ each side, similar to what one would do with cast resin.

I tried putting it into an oven and heating it to $\pu{250°C}$, where it melted, but never enough to pour it somewhere.

Is there a viable way to melt HDPE scraps to a point where it becomes fluid, with a viscosity similar to engine oil, and retains this state long enough to pour it?


texts: Is [PdCl2(PMe3)2] diamagnetic or paramagnetic?

texts:
Please tell me where I am wrong. The complex will have $\ce{Pd^{2+}}$ ion, which has a $\mathrm{d^8}$ configuration. So, it will have $2$ unpaired electrons. Unpaired electrons will mean that it is paramagnetic.

My reference book has this line:

  $\ce{[PdCl2(PMe3)2]}$ is a diamagnetic complex of Pd(II)

Shouldn't it say "paramagnetic"?


texts: Mechanism of acetylene formation from iodoform and silver

texts:
My book mentions a synthetic route for turning iodoform into propyne.

That conversion was somewhat as follows:

  $$\ce{CHI3->[Ag] HC#CH ->[NaNH2] NaC#CH ->[CH3Br] CH3C#CH}$$

The first step is the conversion of iodoform into acetylene with silver. I am unsure how that reaction works. Could someone provide a mechanism?


texts: Where do I find data on 'molecular membership' sequences?

texts:
Techniques such as isotopic labeling allow for radioactive tracing of an element through a sequence of molecules. Using analytical instruments (such as LC-MS) we can then find out where labelled atoms ended up during an experiment. This is how we can construct models of the origins of atoms such as in the following.

I'm interested in giving this topic an abstract treatment that doesn't consider the laboratory approach. The concept I am aiming for can be posed as a problem: given a particular atom from a given molecule, and a collection of chemical reactions, construct the all sequences of molecules that include that starting atom in which molecules are adjacent in a sequence if there exists a chemical reaction from the aforementioned reference collection of reactions in the pair of molecules paired as (reactant, product).
Because we are following a particular atom, it is not sufficient to just create sequences of reactant-product pairs. I'm not sure what to call such sequences, but in the title this is what I am referring to as 'molecular membership' sequences. Do databases of such sequences of molecules exist, even pairwise for one reaction at a time?


texts: Difference between 'homogeneous mixture of several chemical compounds' & 'non-homogeneous system'

texts:
I just started reading Thermodynamics by Enrico Fermi; he started defining state of a system for homogeneous mixture of several chemical compounds & then non-homogeneous system as:

I thought non-homogeneous system to be a mixture of several homogeneous chemical compounds separated by boundaries. But Fermi seems to have done it otherwise; he has defined the state separately for homogeneous mixture of several chemical compounds & non-homogeneous system that is, mixture of several homogeneous chemical compounds. I am not getting how they are different at all. Can anyone please explain how they are different? What's the difference between  homogeneous mixture of several chemical compounds & non-homogeneous system?


texts:
Do orbitals exist even when they are not occupied?

For example: $\ce{Cr^{+3}}$ has the configuration $\ce{[Ar]}\mathrm{3d^3}$ with the other two $\mathrm{3d}$ orbitals empty. We know the  other two orbitals exist, since the metal "uses its empty $\mathrm{d}$ orbitals" to form complexes.

But, for $\ce{Na+}$ with configuration $\ce{[Ne]}$, do the $\mathrm{3s,3p}$ and $\mathrm{3d}$ orbitals exist  too?


texts: Determining boiling point on a created temperature scale

texts:
1.Assume that you construct a thermometer using gallium as the fluid instead of mercury, and that you define the melting point of gallium as 0 °G and the boiling point of gallium as 1000 °G. What is the melting
  point of sodium chloride (801 °C) on the gallium scale?

First we determine the ratio of $^{\circ}\mathrm G/^{\circ}\mathrm C$ by dividing the melting points. This states that $0.4599\ ^{\circ}\mathrm G=1\ ^{\circ}\mathrm C$.

$$\dfrac{1000\ ^{\circ}\mathrm G-0\ ^{\circ}\mathrm G}{2204\ ^{\circ}\mathrm C-29.78\ ^{\circ}\mathrm C}=\dfrac{1000\ ^{\circ}\mathrm G}{2174.22\ ^{\circ}\mathrm C}=0.4599\ ^{\circ}\mathrm G/^{\circ}\mathrm C$$

To calculate the boiling point, this is done: $$T=0.4599\ ^{\circ}\mathrm G/^{\circ}\mathrm C\times\left(801\ ^{\circ}\mathrm C-29.78\ ^{\circ}\mathrm C\right)=355\ ^{\circ}\mathrm G$$

My question is, why are we subtracting by $29.78\ ^{\circ}\mathrm C$?


texts: To which state of matter does the flame belong to?

texts:
I had this question from the day (9 years old, now 16) that I learned about states of matter. I have asked many of my teachers, some of them told me it's a gas some that it's a plasma. Can anyone answer my question?

Recently I've learned that the plasma state is obtained when all the electrons from the atom are removed. Obviously it's present in the sun due to high temperatures.


texts: Separation of a solution of n-butanol and nitroethane

texts: Theoretically speaking, how could one separate a solution of n-butanol and nitroethane? They have a similar boiling point, so fractional distillation would be not possible. Wikipedia also states that nitroethane is more miscible in water than butanol, but that would probably give a water nitroethane azeotrope (?). Can anyone tell how the separation could be achieved? Also, would it be a difference between a 50:50 solution and a 5:95 (vice versa)?


texts: Oxidation of Unsymmetrical Ketones using Selenium Dioxide

texts:
I have searched the whole internet but I could only see examples where the authors of the article took $\ce{R1}$ and $\ce{R2}$ as the alkyl groups around the carbon. This is regarding the oxidation of carbonyl compounds (I am specifically searching about ketones) using $\ce{SeO2}$. What I understood was $\ce{C=O}$ got introduced on the alpha-carbon and two hydrogens from that carbon were lost. Please tell me the product obtained on reacting pentan-2-one with $\ce{SeO2}$. Will the carbon having 3 alpha-hydrogens become $\ce{C=O}$ or will the other one having 2 alpha hydrogens become $\ce{C=O}$?
References:

Selenium dioxide oxidation of ketones and aldehydes. Evidence for
the intermediacy of .beta.-ketoseleninic, K. Barry Sharpless and
Kenneth M. Gordon Journal of the American Chemical Society,
1976, 98 (1), 300-301 DOI: 10.1021/ja00417a083
https://www.adichemistry.com/organic/organicreagents/seo2/selenium-dioxide-seo2.html


texts: How to calculate Gibbs free energy from pKa?

texts: Is it possible to calculate Gibbs free energy ($ΔG = -RT\ln K_\mathrm{eq}$) of an acid dissociation reaction using the $\mathrm{p}K_\mathrm{a}$? If so, how?


texts: Why does Xe have a higher boiling point than Ne?

texts: I am certain that the reason involves intermolecular forces, but since both $Xe$ and $Ne$ are noble and non-polar gases, shouldn't these forces have a much smaller effect or negligible on boiling point?


texts: Converting units and sig figs (finding molarity)?

texts:
This may seem very basic, but I'm a little confused.

"What is the molarity of a solution 500 mL of which contains 0.500 moles of HCl?"

Being that 500 has one significant figure, would it be 500 mL = 0.5 L as opposed to 500 mL = 0.500 L? In which case the answer would be 1 mol/L instead of 1.00 mol/L?


texts: Chemical potential of mixtures of ideal gases and the Gibbs-Duhem equation

texts:
As is well known for a constant composition system, $\mu$ (symbolizing chemical potential) is equal to the molar Gibbs energy. Using
$$
\mathrm{d}G = V\mathrm{d}p-S\mathrm{d}T,
$$
we can write
$$
\mu = \mu^{0} + RT\ln P.
$$
But for mixtures,
$$
\mathrm{d}G = V\mathrm{d}p - S\mathrm{d}t + \mu_{\ce{A}} \mathrm{d}n_{\ce{A}} + \mu_{\ce{B}} \mathrm{d}n_{\ce{B}}
$$
Can the original formula for chemical potential in the case of mixtures?

Moreover, using the Gibbs-Duhem equation,
$$
n_{\ce{A}} \mathrm{d}\mu_{\ce{A}} + n_{\ce{B}} \mathrm{d}\mu_{\ce{B}} = 0,
$$
which means that $\mu_{\ce{A}}$ changes upon adding B to the mixture, even when the partial pressure of A is constant. This contradicts the formula.


texts: How do you determine the pH of a solution at different volumes?

texts:
For a tube with 1 mL of 0.75 % (w/v) casein in 0.10 M sodium acetate, with 0.05 mL acetic acid, and 6.95 mL H2O, how do you determine the pH?

My original thought was to use the Henderson-Hasselbalch equation with the concentration of base being 1 and the concentration of acid being 0.05, but this does not feel right.

I think my fundamental understanding of the direct correlation between concentration and volume is not correct.


texts: Adulteration of turmeric with Metanil yellow

texts:
I read in the local paper that common food products like turmeric can be adulterated. It continued to specify the adulterant which they called metanil yellow. On searching on the Net, I was able to find that metanil yellow is prepared using some basic raw materials like metanilic acid and diphenylamine. The paper continued to lay out procedures on how to find out whether the turmeric you buy from the local market is adulterated. To do this, one must first dissolve half a spoon full of turmeric powder in 20ml of lukewarm water. It then told to add a few drops of hydrochloric acid. Upon doing this, if the aqueous solution turned pink, violet or purple, it indicated the presence of metanil yellow. It continued to state the risks of consuming turmeric adulterated with metanil yellow. One of these risks was that it is a carcinogen. I'm an Indian, so turmeric is included in nearly all of the dishes I eat in a day, so I became very curious. My question is this:

1.) What is the chemical formula for metanil yellow, how is it prepared (in layman's terms), and how does it react with hydrochloric acid to turn pink, purple or violet (a chemical equation would be helpful)?
2.)What are the risks in consuming metanil yellow?


texts:
I got very basic doubt. Henry law's Give relation between concentration vs Partial pressure.  So here is the Numerical Of my textbook

**Now My question is, why concentration is Considered only in Grams? shouldn't it be in Molarity, Mole fraction or Strength(gm/Vol) etc? **

In Other textbook, They simply used formula to solve it.
mass = Henry's Constant * pressure.


texts: What are these stains on my stainless steel pans?

texts:
I've had enough of the homemaker advice of baking soda or barkeeper's friend products - their advice isn't working.  I need a chemist!

Please see the two photos below.  This pan isn't quite as clean as I could possibly get them if I scrubbed and scrubbed with a Brillo pad, but it's close - and as clean as I can get it would only last for about one use before it needed more intense scrubbing.

The brand of this pan is Cuisinart which is relevant only for the particular variant of stainless steel they might be known to use, but I don't think my experience with this brand is much different than I've had with, say, Calphalon stainless steel pans.

I refer to these blackened areas as stains because they have no significant dimension to them, as opposed to "baked-on-crud" which has a dimension and is more expected/accepted by me than the stains.  The stains are rougher than the shiny parts though, impacting use.

1) Why am I getting these stains?  Am I doing something wrong (heating technique or kinds of food chemicals that adhere to SS)?  Are these pans inferior and really I need to buy very high-end/expensive pans (for a different grade of stainless steel) for them to be indestructible?

2) With knowledge of the chemistry involved that leads to this visual effect on the stainless steel, is there an industrial chemical (like those in carburetor cleaner or something) that could clean this stuff off without damaging the pan and which I could completely remove (to avoid toxicity in my food)?


texts:
I read in a page that ionisation is an irreversible process. But, as equilibrium is always reversible would that mean equilibrium does not involve ionisation process.
And than dissociation is a reversible process therefore only dissociation process is seen in ionic equilibrium.
Now if the above statement is correct would that mean only covalent compounds take part in ionic equilibrium?


texts: How to calculate the amount of citric acid to neutralise the pH within wastewater?

texts:
We have an effluent tank, with a consent to discharge at between 5.5 - 11 pH, the tank holds 100000 liters of dirty water.

When the pH reaches 10.5 we add citric acid to bring the pH down. How many liters of citric acid with a pH of 2.2 should we add to the system to bring the pH down to around 7. We always end up putting too much in then add caustic to bring it back up.


texts:
I see the term "superionic" applied to high pressure water in articles like Giant planets may host superionic water, but I don't understand what the term really means.

How is "superionic" distinguished from simply "ionic"?

Why does the article refer to hydrogen "atoms", which would imply that they are neutral, as opposed to protons or hydronium or some other actual ion?


texts: Determination of pKa by absorbance and pH of buffer solutions

texts:
I've been tasked (as part of a report) to calculate the $\mathrm pK_\mathrm a$ of 4-nitrophenol by measuring the pH and absorbance of six 'buffer solutions' containing the 4-nitrophenol:

$$\begin{array}{cccc}\hline
\text{Solution} & \text{Volume of base / }\pu{cm^3} & \text{Volume of acid / }\pu{cm^3} & \text{Volume of phenol / }\pu{cm^3} \\ \hline
1 & 2.80 & 7.20 & 1.00 \\
2 & 5.00 & 5.00 & 1.00 \\
3 & 6.20 & 3.80 & 1.00 \\
4 & 7.20 & 2.80 & 1.00 \\
5 & 8.70 & 1.30 & 1.00 \\
6 & 10.00 & 0.00 & 1.00 \\ \hline
\end{array}$$

We have to then plot a graph of $\mathrm{pH}$ versus $\log_{10}[A/(A_f-A)]$ and use that graph to calculate $\mathrm pK_\mathrm a$. $\text{A}_{f}$ is the absorbance of Solution 6 - we assume that the weak acid in the buffer is present only as its conjugate base - and A is the absorbance of the buffer solution.

My two questions about this are:
1) Where does the expression $\log_{10}[A/(A_f-A)]$ come from? I thought the derivation would be as follows, which clearly gives a different result ($\text{A}_{f}$ on the numerator rather than $\text{A}$):

  Using the Beer-Lambert Law,

  $$
\begin{align}
A &= \epsilon cl \\
c_\text{base} &= \frac{A_{f}}{\epsilon l} \\
\end{align}
$$

  And substituting into the Henderson–Hasselbalch equation:

  $$
\begin{align}
\mathrm{pH} &= \mathrm pK_\mathrm a + \log_{10}\left(\frac{[\text{conj. base}]}{[\text{acid}]}\right) \\
\mathrm{pH} &= \mathrm pK_\mathrm a + \log_{10}\left(\frac{A_{f}}{A_{f}-A}\right) \\
\end{align}
$$

2) Once I have the graph, how do I calculate $\mathrm pK_\mathrm a$ from it? Assumed it would be using the gradient of the line of best fit, but that won't work since $\mathrm pK_\mathrm a$ is given by the difference of $\mathrm{pH}$ and $\log_{10}[A/(A_f-A)]$ rather than the quotient.


texts: Hofmann rule and deviation from E2 mechanism

texts:
I've learnt that

  The best reaction conditions for synthesis of alkene by dehydrohalogenation are those that promote an E2 mechanism.

(From "Organic Chemistry" by TW Graham Solomons)

But, in the same book it is given that when 2-bromo-2-methylbutane follows Hofmann elimination with tert-BuOK as follows:

Clearly, it isn't following E2 mechanism.

When given such reactions, should I go with E2 mechanism or Hofmann rule, and why?


texts: Reference Books on Electrolysis and Chemical Titration process

texts:
I'm in a General Chemistry course in college. We have laboratory, and then we are supposed to make a report on what we did, etc.

I'm not entirely sure what the last laboratory was about, but it was called Salt and Water Electrolysis

To sum up the procedures -two general procedures-, here's what we did:

1st Procedure:

We prepared 50 mL of a $\ce{NaCl(aq)}$ solution at 0.1 M (molarity) in a 100 mL beaker
We made a DC (direct current) circuit at 5V and 700 mA, with graphite electrodes
We turned the circuit on for roughly 20 minutes
We employed a magnetic stirrer to stir the solution
We added 3 drops of Phenolphthalein in the solution, and took notes of the phenomena. (I guess it kinda turned pink)

And that was that for the 1st procedure.

2nd procedure:

We measured the solution's pH with a pH meter
We measured roughly 15 mL of $\ce{HCl}$ (Hydrochloric Acid) at 0.5 M with a test tube
We poured the solution of $\ce{HCl}$ in a 25 mL burette.
We prepared the titration equipment
We were supposed to add the $\ce{HCl}$ (drop by drop) to the $\ce{NaCl}$ solution and at the same time be measuring the pH until it got to 7

And that was that for the second procedure.

Of course we kind of messed up, as we overshot the end point. The excess $\ce{HCl}$ brought it's pH to 3 point something.

The $\ce{NaCl}$ solution lost its pink color, and then turned yellowish.

So.. I guess I am asking for references to the equipment involved -I kind of have references for the pH and the properties involved, still, if you know of some references, let me know!-, I've looked for electrolysis processes in books but don't find any. Or they're too technical. Also, haven't found titration procedures in books.

Can you help me out, just so I can finish my report?


texts:
I wanted to understand mechanism of the formation of $\ce{F3-}$ anion through the molecular orbital theory.

UPDATE - What I really want to know is that when $\ce{F3-}$ is formed from $\ce{F2-}$ and $\ce{F}$, the unpaired electron of $\ce{F}$ enters the anti-bonding orbital $\sigma^*_{\mathrm{2s}}$ then shouldn't the $\ce{F2-}$ ion break up, as all the bonding and anti-bonding orbitals would be filled up, resulting in a bond order of 0?


texts: O-carboxylation in the Kolbe-Schmitt reaction

texts: In the Kolbe-Schmitt reaction, we know that the pi electrons of the benzene ring attack the carbon in carbon dioxide, but why doesn't the reaction occur on oxygen instead (as shown in the diagram below)?


texts: Would sodium metal react differently with aqueous solutions than with pure water?

texts:
I know sodium metal reacts violently with water, but what about aqueous solutions (like sodium bicarbonate). Also, what would the reaction kinetics be?

I have watched YouTube videos were a small piece of elementary sodium reacts completely with water in a matter of seconds. Would that also be the case of elementary sodium in aqueous solutions (for example sodium bicarbonate)?


texts: What is a simple ratio in which atoms combine?

texts:
According to Modern Atomic Theory:

  The ratio in which the different atoms combine may be fixed and integral but may not always be simple.

The example given is that in sugar molecule the ratio of $\ce{C,H}$ and $\ce{O}$ atoms is $12:22:11$ which is not simple.

Well, what I see here is that 12,22 and 11 are whole numbers, then why is this not a simple ratio?


texts: Is it a "Bary center" or a "Bari center"?

texts:
(Studying Coordination Chemistry, "Crystal Field Theory" at school)

Apparently, different sources spell this differently.

The Wikipedia article on Crystal Field Stabilization Energy, calls it the "Barycenter" (as does my school textbook)

However, the actual Wikipedia article on the "Barycenter" refers to, (as far as I can tell) the center of mass of two mutually orbiting bodies. Whereas the "Bary/Baricenter" I'm talking about is the zero-energy reference level in octahedral complexes.

Another book I have at hand (Concise Inorganic Chemistry Lee, J.D), prominently uses the term "Bari centre".

The center/centre distinction aside, what I've been able to glean from my books (and the internet), is that this term is spelled in four different ways (Wah! Such gross inconsistency in literature!):

Barycenter
Bary center
Baricenter
Bari center

But which one's correct (or at least, a more preferred term in Chemistry-literature)?


texts: Difference between reactions of ring strained cycloalkanes and higher cycloalkanes (n>4)

texts:
Today I read two publications stating that cyclopropane's ring can be opened by reactions of it with $\ce{Cl2/Br2/HCl/HBr}$. Correct me please if I interpreted something wrong.

Here are these publications:

Lee, C. C.; Hahn, B.; Wan, K.; Woodcock, D. J. Reactions of cyclopropane with hydrochloric acid and of bromocyclopropane with hydrobromic acid. J. Org. Chem. 1969, 34 (10), 3210–3211. DOI: 10.1021/jo01262a097.
Lambert, J. B.; Chelius, E. C.; Schulz, W. J.; Carpenter, N. E. Polar bromination and chlorination of cyclopropane. J. Am. Chem. Soc. 1990, 112 (8), 3156–3162. DOI: 10.1021/ja00164a043.

I read as well that cyclopropane has extra reactivity (due to ring strain obviously) so in the light, it behaves like a linear alkane getting substituted but in the absence of light, ring gets opened (as shown in a ChemGuide article.

Here are my questions about ring-strained cycloalkanes:

can be ring-opening agents for cyclopropane used for cyclobutane?
can we open ring-strained cycloalkanes with hydrogen (and catalyst of course)?
can we substitute cyclobutane like a cyclopropane? (in light)

But, still, I got a few questions about higher cycloalkanes' chemistry

does hydrogen with catalyst open higher cycloalkanes' rings?
in the reaction of $\ce{Cl2/Br2}$ with higher cycloalkanes ($n>4$), ring gets opened or compound is substituted?
do higher cycloalkanes ($n>4$) even react with $\ce{HCl/HBr}$?


texts: Where should we place alpha,beta unsaturated carbonyls in the reactivity order list?

texts:
In this question, reasons for this observed trend of reactivity of different types of carbonyl compounds are discussed.

I would like to know where we can place $\alpha,\beta$ unsaturated carbonyls in this list.

Initially I thought we can place them above acyl chlorides because now we have 2 electrophilic carbons but then I think the reactivity of both of the carbons should also be reduced because of conjugation so they should be placed somewhere in the middle, but where exactly?


texts: How to calculate the amount charge transfer from a natural population analysis?

texts:
I am trying to reproduce the quantity referred to as the degree of charge transfer reported in this publication by Zhu et al. [Ref. 1] for the F4-TCNQ molecule. I am interested in section 3.2 in the main text about using the bond length as an estimate for the charge transfer amount.

In figure 3b, the authors show the correlation between the degree of charge transfer, CT$_{pop}$ from their natural population analysis compared to the approximation of the bond lengths of F4-TCNQ from equation 1, shown below.

$$\rho = \frac{\alpha_{CT}-\alpha_{0}}{\alpha_{-1}-\alpha_{0}}$$
with $\alpha_i = l_3 (l_2+l_4)$ where $l$ is the bond length, and subscript $i=0, -1, CT$ denote the netural molecule, the anion, and the compelx, respectively.

It's not clear to me, how the authors determined the values on the y-axis in Figure 3b, and there are no further clarification or references to a methodology for the values within the text or supplement information. Both axes in Figure 3b use the F4-TCNQ anion as an arbitrary reference.

I can calculate $\rho$ from the above equation, but I want to compare $\rho$ to the CT$_{pop}$ at the level of theory I am employing, verifying the accuracy of my calculations.

Through reading and googling, I believe the CT$_{pop}$ refers to a population analysis such as a Mulliken or natural population (AKA Lowdin population), referenced in Mendez et al. [Ref. 2] (bottom of page 9 in the Theory footnote). I do not know how to obtain the degree of charge transfer from the resulting population analysis.

I have one reference from Joo et al. [Ref. 3] who gives more details on a similar method, writing on page 2, left column:

The calculated atomic charges were then used to obtain the degree
of charge transfer between the donor and acceptor molecules,
which may be defined as the sum of all atomic charges on the
donor part of the complex.

The above text leaves me to believe the method of determining the degree of charge transfer is as follows:

Calculate a population analysis of the DA (donor and acceptor) complex to determine the atomic charge
Determine the atomic charge of each of the fragments D and A by summing the atomic charge for the D and A fragments, respectively
Report the atomic charge of fragments as the degree of charge transfer.

The last aspect is Joo et al. [Ref. 3] reports the value for the electron donor while Zhu et al. [Ref. 1] indicates the value for the electron acceptor, which is F4-TCNQ.

Does this procedure sound reasonable? Any thoughts or comments would be appreciated.

TL;DR
How can I reproduce the values shown in Figure 3b on the y-axis, the degree of charge transfer from a natural population analysis?

References

Zhu L; Kim E.-G; Yi Y; Bredas J.-L. Charge Transfer in Molecular Complexes with 2,3,5,6-Tetrafluoro-7,7,8,8- Tetracyanoquinodimethane (f4-Tcnq): A Density Functional Theory Study. Chemistry of Materials 2011, 23 (23), 5149–5159 DOI: 10.1021/cm201798x.
Méndez Henry; Heimel, G.; Winkler, S.; Frisch, J.; Opitz, A.; Sauer, K.; Wegner, B.; Oehzelt, M.; Röthel Christian; Duhm, S.; et al. Charge-Transfer Crystallites As Molecular Electrical Dopants. Nature Communications 2015, 6 (1) DOI: 10.1038/ncomms9560.
Joo B; Kim EG. Model-Independent Determination of the Degree of Charge Transfer in Molecular and Metal Complexes. Chemical Communications (Cambridge, England) 2015, 51 (81), 15071–15074 DOI: 10.1039/c5cc05274b.


texts:
Why do we have an alkyl shift rather than epoxidation in a pinacol reaction?
I don't understand why the hydroxyl group doesn't attack the positive charge.


texts:
Aluminum chlorohydrate is often referred to as basic aluminum chloride.
The pH value of ACH is about 4. How is basicity in this context defined?


texts:
$$\ce{4Fe + 3O2  -> 2Fe2O3(s) + 1625~$\mathrm{kJ}$}$$

This should be endothermic because the energy is in the product. However, if the equation is viewed from the perspective of the reactant, it is endothermic.

Is this endo- or exothermic?


texts: What can be concluded from two different values for the interplanar distance between planes of atoms in an X-Ray diffraction experiment?

texts:
I analyzed an unknown Alkali Halide crystal using x-rays from a copper source. I need to find the d-spacing for this crystal, i.e. the interplanar distance between planes of atoms.

I found my $K_\alpha$ and $K_\beta$ peaks and used Bragg's Law to calculate the d-spacing. However, these values do not match. Is this an experimental error or could the non-matching values be correct somehow?

For $K_\alpha$:

$$d_{hkl}=\frac{λ}{(2 \sin(θ))}=\frac{(1.54184 Å )}{(2 \sin((28.3°)/2) )}=0.771 Å$$

For $K_\beta$:

$$d_{hkl}=\frac{λ}{(2 \sin(θ))}=\frac{(1.39222 Å )}{(2 \sin((25.7°)/2) )}=2.488 Å$$

My attempt: in both cases, I assumed that these were first order peaks. Could it be that the $K_\beta$ peak is actually a third order peak? If so, then $n=3$ and $d_{hkl}=2.313 Å$. This is reasonably close to the other value. But then what would that tell me about the crystal?


texts: Suggest possible structures for the compound PF3(Ph)(NMe2) using the NMR data

texts:
use these data to suggest the possible structure for the compound PF3(Ph)(NMe2):

19F Spectrum, two signals:
a doublet of doublets, J=56 and 819Hz, -39.5ppm, relative intensity 2
a doublet of triplets J=959 and 56Hz, -68.3ppm, relative intensity 1

31P Spectrum, one signal:
a doublet of triplets, J=959 and 819Hz, -53.0ppm

part b,
    suggest an experiment or measurement that might be helpful to discern possible isomers of the compound

My answer so far:
There are two types of structure that a Phosphorus with five bonds could be, trigonal bipyramidal and square based pyramid. I think that because there are two equivalent fluorines that this must be the trigonal bipyramidal structure as it had the two axial positions that would be equivalent.


texts: Which Flocculant/Coagulant is ideal for harvesting Algae?

texts:
While dealing with Algae fit for human consumption (as protein supplements), which is the most suitable coagulant/Flocculant available?

Factors to consider:

1) Cost Effectiveness (for instance poly glu cost is prohibitive for commercial scale)

2) pH range (If growth medium of algae is alkaline, many coagulants don't work)

3) Suitable for Vegans (Since food grade Algae is often marketed as Vegan food, using Chitosan is not an option)

4) Metallic salts are needed in high doses and are not preferred in general

With these factors in mind, which coagulant/flocculant would be best for harvesting Algae?


texts: Are there any molecules with delta bonds in their ground states?

texts:
When looking at excited states of molecules, $\delta$ bonds are relatively common, but I've never come across a molecule with a $\delta$ bond in its ground state.

Are there molecules with $\delta$ bonds in their ground states?

What about even higher angular momentum states ($\phi$ and $\gamma$ bonds)?


texts: What is the reason behind the numbering of nitrogen bases?

texts: I am studying nitrogen bases and their structures and roles in nucleotide, polynucleotides and nucleic acids formation. In the structures of the nitrogen bases like Adenine, Guanine, Cytosine and Thymine, the numbering is baffling me. Why are the atoms in these molecules numbered so? Can someone please specify the rules for numbering these four molecules? I am a biologist and I'm not so good at chemistry.


texts: (P1,T1) -> to (P2,T2) then what will be the change in enthalpy for ideal gas?

texts:
I need to prove that it is equal to the integral of $C_pdT$ from $T_1$ to $T_2$.
But should not be the case only when the pressure is constant?


texts: When to disconnect tubing in vacuum filtration?

texts:
The UCLA site says in step 6 to disconnect the vacuum tubing before turning off the vacuum and the second link from Leeds says in step 11 to turn off the vacuum source first and then disconnect the tubing.

I've been taught both ways and am confused about the difference in methods.

When should one actually disconnect the tubing and what is the rationale for each method?


texts: Why does the C−H bond dissociation energy vary in a homologous series of primary alcohols?

texts:
Specifically, for the primary carbon atom in the alcohol. Here is bond dissociation energy (BDE) data from chapter three of Luo's Comprehensive handbook of chemical bond energies [1] (boldface refers to dissociated atom):
$$
\begin{array}{llc}
\hline
\text{Compound} & \text{The broken bonds} & \mathrm{BDE}/\pu{kJ mol-1} \\
\hline
\text{Methanol} & \ce{\textbf{H}-CH2OH} & 401.92±0.63 \\
\textit{n}\text{-Ethanol} & \ce{\textbf{H}-CH2CH2OH} & 410.0±8.4 \\
\textit{n}\text{-Propanol} & \ce{\textbf{H}-CH2CH2CH2OH} & 406.3±8.4 \\
\hline
\end{array}
$$
Many websites like Chemistry LibreTexts describe how the average C−H BDE is different from the BDEs in specific compounds. Some explain how the hybridisation of the C−H bond has an effect or whether you're considering the primary, secondary, or tertiary carbon makes a difference.
In the case of the homologous series of primary alcohols though, the hybridisation for the C−H bond is always the same. Also, I'm only using values from the primary carbons. I checked the bond lengths for the C−H bond on the primary carbon for all the alcohols on Molview too. They're all the same.
What other factors can influence the variation in the BDEs?
References

Luo, Y.-R. Comprehensive Handbook of Chemical Bond Energies; CRC press, 2007. ISBN 978-0-8493-7366-4.

An idea my chemistry teacher described:
Perhaps, the intermolecular forces could influence the bond enthalpy between C-H bonds?
For example, as the homologous series of alcohols gains more methylene groups, the London
Dispersion Forces (LDF) between each alcohol molecule increase. So let's say you're heating up the alcohols to break the C-H bonds. In the process, some of the heat energy will go towards overcoming the LDF's attraction between molecules. Then, additional energy would be needed to break the C-H bonds after that.
At the same time though, you would have to consider the effect of decreasing polarity of the alcohol molecules and decreasing dipole-dipole forces. Does anyone know what kind of data could be used to quantify the strength of these different effects?


texts: How to control the Friedel–Crafts alkylation reaction to methylbenzene as the major product?

texts:
My question is due to a discrepancy I found in reactivity and organic conversions.
In reactivity of organic compounds it has been established that an alkyl group activates the benzene ring, and, hence for example, methylbenzene is more reactive than benzene.

Then consider the following situation. Suppose that there are two benzene molecules in a sample, and we convert one of them to toluene (methylbenzene) using Friedel–Crafts alkylation. Then we would see the following change in the mixture:

Now, consider we carry out alkylation once more. As toluene is more reactive than benzene, it will react first forming dimethylbenzene. By continuing this logic we would get hexamethylbenzene as the major product regardless of the amounts we add.

So, how is that we carry out conversions with Friedel–Crafts alkylation regarding toluene as the major product?

Feel free to correct me if my logic is incorrect and if so please specify what should be corrected.


texts:
I was just searching whether Uracil is aromatic or not and in this link$^1$ it is said that (from the abstract):

High-level computational methods were tested for the enthalpy of hydrogenation of uracil, but only with G3 was possible to obtain results in agreement with the experimental ones. It was found that uracil possesses 30.0% of aromatic character in the gaseous phase.

What is the meaning of this sentence? I have only basic knowledge on Aromaticity limited to Huckel's rule and the names of a few aromatic compounds. I didn't expect Aromaticity to be expressed in percentages. Can someone explain why?
Reference

Tiago L. P. Galvão, Inês M. Rocha, Maria D. M. C. Ribeiro da Silva*, and Manuel A. V. Ribeiro da Silva. J. Phys. Chem. A 2013, 117, 28, 5826–5836.
https://doi.org/10.1021/jp404938u


texts:
What would happen if I kept two copper plates and one zinc plate in a solution of dilute sulfuric acid, and joined two copper plates with wires?

(The wires would connect to a single wire and be joined from that wire to the single zinc plate.)

What would be the voltage? Will there be something wrong?


texts: How do we know if a compound is amphoteric or not?

texts:
My teacher told me if it reacts with an acid and a base, then the compound is amphoteric.

However, I am not satisfied. Is there any other way of telling? For example we are give a compound say BeO, how can we say if it's amphoteric or not?


texts: What are the components of Machine learning I have to learn to pursue a project related to computational chemistry?

texts: I will be going to pursue a project entitled "machine learning and python in Chemistry problems" for my visting student program this August probably. Please help me.


texts: Hybridization of carbon atoms present in the smallest ester?

texts:
I found this question in the Resonance DLPD Organic Chemistry book on Page 55:

  What is the hybridization of carbon atoms present in the smallest ester?

The smallest ester as far as I know is methyl formate ($\ce{HCOOCH3}$):

The first carbon atom (on left) has 3 σ bonds and the one on the right has 4 σ bonds. Hence, the hybridization is $\mathrm{sp}^2$ and $\mathrm{sp}^3$, respectively.

However, according to the answer given in the book, all carbon atoms in the smallest ester are $\mathrm{sp}^2$ hybridized.

What did I do wrong? Is there a smaller ester? Or the hybridization of the one I have above not correctly determined?


texts: I am wondering if any of you know about glue/adhesives that do not harden over time after they are applied or glue/adhesives that take a really long time to harden after application. I need the glue to temporarily hold polymer sheets before they are sewed together.


texts: Calculate the mass of Mg needed to produce 5 kg of vanadium

texts:
I need to calculate the mass of magnesium needed to produce $\pu{5 kg}$ of vanadium from the following reaction:

$$\ce{3Mg + 2VCl3 -> 2V + 3MgCl2}$$

given relative atomic masses for $\ce{Mg}$ and $\ce{V}$ as $24$ and $51$, respectively.

I multiplied $24 × 3$ and $51 × 2$ to get

$72 : 102 $

I changed $\pu{5 kg}$ into grams, which is $5000$.

I cross-multiplied to find the answer and then divided the answer by $1000$ to turn it back to kilograms because the question stated it. My answer is $\pu{3.5 kg}$. Is this correct?


texts: carbon dioxide and its behaviour in acid base balance

texts: In human body acid base balance, why and how does the dissolved carbon dioxide increases the hydrogen ion concentration with increasing in its partial pressure..? At the same time bicarbonate ion is staying in same concentration while hydrogen ion are increasing?


texts: Difference between Side Chains and Functional Groups

texts:
From what I've read, a functional group seems to be a specific case of a side chain, but this group must be directly responsible for some of the chemical characteristics of the molecule. However, in some cases, methyl groups (such as R-CH3) are listed as functional groups as well. For example, I have the following question:

The correct answer is listed as C - but isn't the methyl a site of reactivity as well?


texts: When was the name cinnamaldehyde officially changed to trans-3-phenylprop-2-enal?


texts: Is glycinate ligand a monoanion or a zwitterion?

texts:
Glycinate as far as I can guess from the structure is a monoanion with negative charge on oxygen atom (though that negative charge is resonating). But when I used this logic in my exam it costed me 4 marks. I don't understand why.
Is it because it is derived from glycine in strongly basic medium which is not a monoanion but a zwitterion? Still, it doesn't seem to be making sense.


texts: Is there an online database of acid and basic dissociation constants?

texts: Is there an online database of acid and basic dissociation constants, all in one place, free to use?


texts: Is HMgX also a Grignard Reagent like RMgX?

texts:
We do know that the Grignard Reagent is $\ce{RMgX}$ where R is some alkyl group & X is any halogen group.
So, my question is that, whether $\ce{HMgX}$ is also a Grignard Reagent like $\ce{RMgBr}$?


texts:
I readily admit to being a pyrophiliac and can generally be found near fire when there is fire. (Fire good, tree bad.)  One of the byproducts of fire, naturally, is charcoal.  I was looking into ways to activate charcoal instead of buying it over the counter - because how cool would it be able to just make your own - but my research so far isn't very promising.

Apparently, I require intense heat and very little oxygen in order to turn the home and garden variety of charcoal into activated charcoal (as one might find in Norit).

Is it possible to activate your own charcoal (preferably in one's backyard), and if so, does anyone have any ideas or suggestions that I can use to turn my meagre amount of (regular) charcoal into activated charcoal?


texts: Is there a simple way to predict the molecular pi orbitals in conjugated pi systems?

texts: Particularly for longer alkyl chains. Or is predicting these molecular orbitals from quantum mechanics too complex to be able to be translated easily as a geometric pattern? If Frost Circles exist, I just figured something could for this as well. The only pattern I've been able to identify is that each molecular orbital is symmetrical, starts with no nodes and goes up by one with each higher energy orbital but for systems with many carbon atoms, this isn't a specific enough set of rules.


texts:
I am constructing an apparatus for high temperature, strong alkaline melts (metal melts), with extremely high oxygen rich environments.

Here what I have so far.

Iridium is a good candidate - is it better as an alloying agent or would it suffice in an almost pure Iridium composition?

Tantalum - has good temp but from what I understand is weak against alkaline reactions.
If nothing else gets answered, could this please.
If I have a tantalum oxide layer coating the tantalum will that protect it from further corrosion in a high temperature, oxygen rich environment?

Tungsten seems to also have potential, I remember reading a paper from the 50's stating that under high alkaline, temperature conditions the product contained an unsuitable level of impurity from the tungsten? with the properties of tungsten would this be the case.

What I am enquiring about here does anyone know what metals or alloys off-hand that are currently used in these conditions?
Basically I am only looking at refractory metals as the temperature range is (1900 deg C - 2900 deg C)
Also there can be no carbon in the composition of the alloy.


texts: I have read that compound with nitrogen and carbon atoms gives Prussian blue color when sodium extract of the compound is added with $\ce{FeSO4}$ . Will the test work even if the compound has oxygen atoms?


texts: Would tin (II) sulfide be considered a covalent network solid?

texts:
Considering that tin has a Pauling electronegativity of 1.96 and sulphur 2.58, and that a bond is considered to be ionic with a Pauling EN difference of approx. 1.7 at the least, would tin (II) sulfide be considered covalent?

This would be astonishing, since you would expect a metal—non-metal bond to be ionic. Indeed, many (non-academic) websites (such as this one) state that SnS is ionic. Evidence for the ionic character of tin (II) sulfide is the fact that it precipitates from solutions containing Sn(II) ions when adding hydrogen sulphide (which forms S(-II) ions) – thus, the two kinds of ions form a ionic compound (right?). Furthermore, SnS dissolves in hydrochloric acid, while typical covalently bonded networks such as silicon dioxide do not.

Finally, this paper states on the first page (which is freely accessible) that evidence for tin(II) salts with typical symmetrical ionic symmetries is completely lacking.

Thanks in advance, and happy holidays!


texts:
My end objective is to compare GC outputs of samples in two groups using PCA. I have bene given the data in Excel format but have saved to CSV.

Whilst I can locate CSV files through OpenChrom, they all appear blank when I do so.

Having spend a lof of time trying to find the information, I cannot find the relevant info about how my CSV (or Excel) file should be formatted for OpenChrome.

I have columns for retention time (labelled "RT") and area (labelled "Area").
I have tried a simple file with two columns (RT and Area) for one sample. I have also tried files with multiple samples and columns, both with and without sample no. headers. (see pictures).

Whatever option I try, the charts in OpenChrom appear completely blank. I don't know if it's the data itself, the headings, the process I'm going through, not a clue what's going on to be frank.

Lastly, I would like to apologise that this may be a basic/naiive question for the forum. I've essentially been dumped with the work of running PCAs comparing GC data sets with little to no experience in doing so.

Thank you.


texts: Nitrobenzene reduction with (tin) Sn catalyst: Why is C-H bond cleavage preferred over O-H bond cleavage?

texts:
I am trying to understand this mechanism for nitrobenzene reduction with $\ce{Sn/HCl}$. I do not understand why it implies that you pull off the $\ce{C-H}$ hydrogen instead of the $\ce{O-H}$ hydrogen in the methanol.  Is it actually suggesting that the resulting $\ce{.CH2-OH}$ radical formed from the methanol eliminates to form formaldehyde or do you get a rearrangement where you form $\ce{(CH3-O)-}$? If the latter is the case, why not just pluck the proton from the alcohol group instead of breaking the $\ce{C-H}$ bond?

Also, it mentions that organic solvents are preferred for this reaction, why exactly is that over water?


texts: Why does sodium bicarbonate taste salty?

texts:
I just made myself sodium bicarbonate solution to treat heartburn. I never did this before, I rarely suffer from this condition.

What surprised me is how salty did the solution taste. I thought there is no similarity between table salt and baking soda. Yet they taste almost the same it seems.

Why is that?


texts: Are heterolytic dissociations barrier-less or do they have an activation energy?

texts:
When a bond is broken into ionic fragments, and I'm specifically thinking about organometallic or coordination chemistry, the two products carry opposite charges and the potential energy curve should, in my humble opinion, be attractive everywhere (at every point where the distance is larger than its equilibrium value).

Does this mean that the dissociation of a compound like ferrocene into $\ce{FeCp+}$ and $\ce{Cp-}$ (in the gas phase) occurs without a barrier?


texts: In vivo, does it take energy to move double bonds from cis to trans long chain unsaturated fatty acids

texts:
In vitro, long chain fatty acids may yield more energy when bonds break, but in vivo, I understood that energy is burned before unsaturated fatty acids can be oxidized because the side groups with double bonds are crowded, and bunched on one side in the cis position, as all unsaturated FA are, and the molecules of oxidation cannot get in between - they cannot access these bonds to oxidize them.

So I thought I read that ATP is used (how much?) to first get those side double bond groups into the trans position so the oxidation enzymes can reach them.  Let me know if this is not true. Or if there is a thread here that really explains this well.


texts: Is a liquid vitamin E supplement possible without additives?

texts:
Looking at E vitamin products sold commercially, all “pure vitamin E oil” products seem to be for skincare rather than consumption as a supplement.

I have read that d-alpha tocopherol is the form of vitamin E with greatest bioavailability, but even liquid supplement products often contain sunflower or other oils in addition, which I understand to be a source of but of course are not entirely vitamin E.

Is a pure liquid supplement possible or practical for consumption as a supplement, and if not, why?


texts: Reagents for synthesis of ethyl 2-(2,3-dihydrobenzofuran-2-yl)acetate from naphthalen-1(4H)-one

texts:
The following conversion can be performed in a few steps. Show key intermediates and reagents (detailed mechanisms are not required).

So I've been looking at this for a while and I can't seem to figure it out. If someone could please help me by telling what kinds of reactions/reagents I should use in this synthesis. The mechanism is not necesarry to show, since I can do that myself, I just need help with which reaction path to follow.


texts: Why doesn't every pure enantiomer racemise?

texts:
After having been acquainted with enantiomerism for nearly six months, I have one standing doubt.

Consider the structure of alanine. Suppose I have a pure mixture of exclusively 'S-alanine'(left in the picture) in a flask.

There are hundreds, if not, thousands of molecular collisions in the flask per second. Why can not a bump to one of the S-alanine change it to R-alanine? This way, the mixture should racemise itself if left standing for some time. But this does not happen. Why? Can someone please explain?


texts: Validity of the equation K_eq = ratio of rate constants of forward and reverse reactions

texts:
If we have a multi-step reaction (which involves more than one step to reach the products; a complex reaction, one may say), then is the following equation valid?

$$K_\mathrm{eq} = \frac{K_\mathrm{fwd}}{K_\mathrm{rev}}$$
$K_\mathrm{eq}$ – equilibrium constant of the reaction; $K_\mathrm{fwd}$ – rate constant of the forward reaction; $K_\mathrm{rev}$ – rate constant of the reverse reaction.

I know that it is valid for an elementary or single step reaction, where the expression for the rate involves raising the concentrations of the reactants to their coefficients in the balanced equation.

But is it so for a multi step reaction too? (Where the law of mass action is no longer valid?)


texts: Will the solubility of a solute increase over the time a solute dissolve?

texts:
would like to ask about a question that I came across in one of my assessment books. Appreciate the help that I can get.

Qns: In an investigation, two substances X and Y of the same mass are dissolved in the same volume of water. It is found that X dissolves faster than Y. Which of the following graphs correctly shows the solubility of the substances against time in this investigation?

The answer given is A.

I would like to ask why is that so. Intuitively, I would think that the solubility would be a constant since solubility is defined as "the maximum amount of solute that will dissolve in a given volume of solvent at a given temperature and pressure", therefore it will not change with time as the solute is dissolving.

Even if we're talking about rate of dissolving here, shouldn't the rate be decreasing, as when a higher concentration of particles are dissociated, there would be more of the dissociated particles in the solvent which will shift the equilibrium to the left?

Thanks for all your help!


texts: Can a Titanium Grade 5 alloy produced by SLM have greater 'surface area' exposed?

texts:
I was doing an electrochemical test (LPR) and Titanium Grade 5 produced by AM respassivated oxide layer faster than the specimen produced with traditional manufacturing under identical experimental conditions. I am wondering if this can be explained with 'porosity' and being exposed to more 'surface area' as a result?

Regardless of the the porosity level, will the SLM sample be air tight? Only then would my guess here be wrong. I am assuming that the layers below get exposed to oxygen as well which is why I see the plateau (a flatter curve) for SLMed specimen.

I am trying to find a reason for the slightly better performance of the same material from a corrosion point of view when submerged in a specific liquid.


texts: Looking for a low boiling point solvent for MAPI precursors (Lead Iodide (II) and Methylammonium Iodide)

texts:
Things I have thought of till now:

Acetonitrile with HI additive
Acetonitrile with DMSO additive

The problem with the first would be that HI is in an around 55% aqueous solution and water doesn't play well with the perovskite. Meanwhile, the second might end up needing enough DMSO to drastically increase the boiling point. I am not sure about the second and intend to try it out and will post updates when I am done.


texts: Why CCl4 does not dissolve in water while SiCl4 does?

texts:
Why $\ce{CCl4}$ does not dissolve in water while $\ce{SiCl4}$ does?
Does it have to do with d-orbitals? If yes, then how are they related?


texts: Why doesn't self condensation occur in acetoacetic ester synthesis

texts:
So, I came across a quite versatile method to synthesize aldehydes and ketones, its called the Acetoacetic ester synthesis.

Suppose I need some 2-pentanone. So to synthesize it via this method I can do this

But I'm more worried about adding a base to Acetoacetic ester. Won't self condensation occur between two molecules of Acetoacetic ester like this?

If it occurs how do we minimize it? If it doesn't then why?

Any help will be appreciated.


texts: Predicting atomic weight and density of calcium

texts:
I have a question from school:

  Assuming that the element Ca had not been discovered, predict using the properties of the known element surrounding Ca its own properties such as its atomic weight and density.

How do I go about this? I don't know how to predict this, it all looks like building blocks in my head. I can't connect the dots yet, please help me solve this. I have done some google searching but to no avail.

What I tried: I understand that

atomic mass increase across the period;
density increase across the period;
density decreases down the group;
atomic mass increases down the group.


texts: How to meausre ion interferences in solution?

texts:
Is there a way to quantitatively measure the interference of different metal ions in solution? I plan to measure concentration of Pb(II), Fe(II), and Cu(II) in solution together using a spectrophotometer.

I know that I can put multiple samples of two ions together to test for the interference trends/effects, but can I do this for all three? e.g. measure interference effects of both iron/copper on lead? Or are there too many variables to measure concentrations?

If not feasible, are there other accessible ways (besides mass-spec) to measure multiple concentrations of all three at once?

EDIT: I already plan to measure concentrations using reagents, specifically Hach TnTplus 850 and 858, and Hach CuVer 1, as they seem easy to get and use. My purpose is to accurately measure concentrations of one ion when in the presence of two other interfering ions.


texts: What does the label of stability: 0 mean on an MSDS sheet?

texts:
I was reading an MSDS sheet on bleach. There is a section named NFPA. Under that is are the words,

  Health Hazard: 3, Flammability:0, Stability:0

Does that mean that Bleach is highly unstable?


texts: What is lowest energy state, how does an atom gain it and what does it have to do with hybridization?

texts: I understand that hybridisation occurs due to the atom wanting to exist in the most stable state possible, and the most stable state has the lowest energy. What I don't understand, however, is say, in CH4, the bond angle is 109°18', so how does this particular value mean that the atoms and bonds in methane are farthest from each other? And if they are indeed farthest from each other, how does that mean the CH4 molecule's in the lowest energy state?


texts: Para effects on substituents in aromatic compounds

texts:
I wanted to know how to compare the following compounds on basis of acidic strength.

I have to find the acidic strength of following compounds with $\mathrm{X}=\ce{CH3, \ OCH3,}$ and $\ce{NO2}$.

For ease of explaining, denote the first compunds as (A), the second as (B), and the third as (C)

Due to steric inhibition of Resonance (SIR) effect, compound (A) will be the most acidic, as its anion will be the least stable.

Now for ordering the other two, I know that there are two things affecting acidic character:

Bond strength; the weaker the bond, the higher its acidic strength
Charge on hydrogen; the more positive charge their is on the hydrogen, the more its acidic strength.

So now if we take $\mathrm{X}=\ce{CH3}$, we should have that $\mathrm{(A)>(C)>(B)}$; as $\ce{CH3}$ is an electron donating group and it would make the hydrogen less positive, and inductive effect is distance dependent. This answer is incorrect as per my textbook, which says $\mathrm{(A)>(B)>(C)}$.

If we take $\mathrm{X}=\ce{OCH3}$ which is an electron withdrawing group, we should have $\mathrm{(A)>(B)>(C)}$. This answer is correct.

If we take $\mathrm{X}=\ce{NO2}$, which is also an electron withdrawing, we should have $\mathrm{(A)>(B)>(C)}$. But my textbook says the answer is $\mathrm{(A)>(C)>(B)}$.

I wanted to know where am I going wrong, and if there is some other effect I am not taking into account.

Note: my earlier question was closed due to the similar question: Ortho-effect in substituted aromatic acids and bases.
But that question only deals with the ortho effects of substituents, not the para.


texts: How do I use the priority list of substituent groups to decide the parent chain for this compound?

texts:
I know that the -OH group has a higher priority than the -Cl group, but does that mean I should favour including it in my parent chain even if there's another chain that has a lower locant on the first substituent group?

My intuition is that the chain with the lower locant should be favoured. Is my reasoning in line with IUPAC rules?


texts: How is the degree of unsaturation derived?

texts:
The formula for degrees of unsaturation is:

$$1+ \frac{1}{2} \sum ( n_i (v_i-2))$$

$v_i$ = valency of atom
$n_i$ = number of atoms with that valency

Could someone explain how the formula works, and why divalent atoms don't contribute to unsaturation (as evident from the formula).


texts: Does mechanotransduction of cells play a role in the biocompatibility of titanium?

texts:
What exactly is mechanotransduction? The definition seems to vary from source to source. Some indicate that mechanotransduction is the underlying principle where cells pull on the surface they grow on to test their stiffness, so they can stretch and facilitate cell growth and differentiation. Others indicate that mechanotransduction is how cells detect mechanical stimuli and turn them into chemical signals like our four senses (touch, hearing, smell, etc).

Also, is this the main reason titanium is biocompatible to replace bones because it has a low surface resistance and cells can stretch on it?


texts: Since PbCl2 is insoluble in water, how is it that lead leached from pipes due to Cl- reaction can become ingested?

texts: I have reviewed a discussion concerning the salt content in the Flint River being directly connected to lead being leached from civic water pipes in Flint, Michigan. Wikipedia has a site dedicated to $\ce{PbCl2}$ and line 1 states that this salt, once formed is insoluble in water, unless that water is heated. Is there a secondary process that results in the lead returning to a form, which can be ingested — after it has been leeched from the wall of a pipe?


texts: How many empty orbitals do elements have?

texts:
A student was contemplating a question regarding elements with "no empty valence orbitals." An argument was made that elements all have infinite number of valence orbitals.

  Every atom basically has an infinite number of shells. The thing is that almost all of those shells are empty (they don’t have electrons in them).

https://van.physics.illinois.edu/qa/listing.php?id=1224

So it is facile to say that, say, the fluoride anion has no empty valence orbitals on the basis of it having 8 valence electrons and the $2n^2$ rule (where n = 2)?


texts: How to measure band gap of powder sample with using diffuse reflectance method

texts: We have UV SHİMADZU 2550 and its diffuse reflectance attachment. I want to measure band gap of single crystal samples. What should I do? Which formulas should I use to calculate band gap? I don't have much sample...


texts: Why is the empirical formula of sodium chloride NaCl?

texts: Since we know in sodium chloride crystal sodium ions are surrounded by $6$ chloride ions and each chloride ions are again bonded to $6$ sodium ions. What I want to know is that on what basis empirical formula of sodium chloride was assigned to be NaCl? does that formula mean sodium ion should atleast bonded to one chloride ion?


texts: What is the correct discharge reaction in nickel-cadmium cell?

texts:
In school textbook

$$\ce{Cd +2Ni(OH)3->CdO + 2Ni(OH)2 + H2O}$$

Wikipedia

$$\ce{2NiO(OH) + Cd + 2H2O->2Ni(OH)2 + Cd(OH)2}$$

Chemwiki

$$\ce{Cd +NiO2 + 2H2O->Cd(OH)2 + 2Ni(OH)2}$$

Which reaction should I follow?

The ChemWiki page got updated on 22nd Jan 2017, an year after this question was posted, and the reaction in question has since been updated. The reaction on the ChemWiki page is now identical with that on the Wikipedia page. This question now has no significance whatsoever but for the sake of the time and effort of the answerer, I am keeping it undeleted


texts: Can one exclude calibration points using a combination of permutation testing and a non-parametric test statistic?

texts:
I work in bioanalytical chemistry. I have used an analytical instrument (LC-MS) to measure the response (peak area) of several compounds spiked in to equivalent samples at known concentrations. Each sample, at each concentration, was analysed three times over three separate days. Spike concentrations, for this example, are: 0 (blank), 1, 2, 5, 10, 50, 125, 250, 500, 1000 ng/L. I now wish to construct sensible calibration curves using linear least squares regression (hence, assuming homoscedacity of data, but still acknowledging the potential for outliers) of the response (peak area) versus spike concentration (i.e. the spike concentration).

From visual inspection of data files, it appears that for some compounds there are samples that were spiked at > 0 ng/L that are indistinguishable from blank samples (i.e. those at 0 ng/L). I’d like to test my suspicions statistically and, if significant at a reasonable threshold, would exclude these samples prior to performing the least squares regression.

Given that, for many compounds, the data are often non-‘normal’ around the lower-end of the calibration curve in such dataset, I thought to use permutation testing to generate a sampling distribution. Here, I’d define a null hypothesis that the median peak area of blank samples (0 ng/L) is equal to that of non-blank samples at a defined concentration (e.g. 1 ng/L), i.e. a statistical test of location. Drawing from the world of parametric tests, I’d hoped to use: [median(peak areas of non-blank samples at single concentration) - median(peak areas of blank)] / median absolute deviation(peak areas of non-blank samples at single concentration).

Here, the sampling distribution would be generated by repeatedly randomising class labels (i.e. concentration labels for 0 ng/L and the calibrant level being tested) and calculating the test statistic. The p-value would be derived as the proportion of the permuted test statistics that were equal-to or greater-than the actual measured statistic, i.e. as calculated before randomising labels. If the p-value turns out to be greater than some pre-determined threshold (probably going to be 0.05 or 0.01), I accept the null hypothesis. Given that I would repeat this test for each concentration level, I’d also plan to apply a Benjamini-Hochberg correction to the final list of p-values and reject then exclude concentration levels with adjusted p-values above the cutoff (I’d aim for either 0.05 or 0.01 – yet to decide).

So, feedback on the following would be great:

Does the proposed test statistic seem reasonable as a non-parametric replacement to the t-statistic?
Is it appropriate to exclude samples from the regression, for which the p-value for the test statistic exceeds the defined threshold?


texts:
What would be the order of electron density in the benzene ring in the following compounds?

Methyl Benzene

Ethyl Benzene

t-butyl benzene

I would say that t-butyl benzene would have the highest electron density as the alkyl group attached to it is bulkier than methyl and ethyl thus it will exert a greater +I effect pushing the electrons into the ring making it electron rich. Using same analogy ethyl benzene would have a greater electron density in the ring compared to methyl benzene.

However that is not the case. Something counter intuitive seems to be happening here. The order is methyl benzene >ethyl benzene >t-butyl benzene.

I think this phenomenon can somehow be explained using hyper conjugation, but i don't get it how?


texts:
Essentially I want to derive the buffer formula: $\ce{pH}$ = $\mathrm{p}K_\mathrm {a}$ + $\log$ $\left(\frac{\alpha}{1-\alpha} \right)$ to $\alpha$ = $\left(\frac{1}{10^{\mathrm{p}K_\mathrm{a}-\ce{pH}}+1} \right)$
I'm going to include everything I had done trying to solve this here (and also show where I got stuck):

$$\ce{pH} = \mathrm{p}K_\mathrm{a} + \log(\alpha) - \log(1-\alpha)$$

$$\ce{pH} - \mathrm{p}K_\mathrm{a} + \log(1-\alpha) = \log(\alpha)$$

$$\alpha = 10^{\ce{pH}-\mathrm{p}K_\mathrm{a}+\log(1-\alpha)}$$

$$\alpha = 10^{\ce{pH}} \times 10^{-\mathrm{p}K_\mathrm{a}} \times 10^{\log(1-\alpha)}$$

$$\alpha = 10^{-\log\ce{[H+]}} \times 10^{\log(K_\mathrm{a})} \times 10^{\log(1-\alpha)}$$

$$\alpha = \ce{[H+]}^{-1} \times K_\mathrm{a} \times (1-\alpha)$$

$$K_\mathrm{a} = \left(\frac{\alpha \times \ce{[H+]}}{(1-\alpha)}\right)$$

So at this point I got stuck and have no clue how to get rid of an $\alpha$ to complete the derivation. Appreciate any help.

Edit: Managed to complete. For those who are interested in how I had done it in the end:
$$\ce{pH}-\ce{pK_\mathrm{a}} = \log\left(\frac{\alpha}{1-\alpha}\right)$$

$$10^{pH-pK_\mathrm{a}} = \left(\frac{\alpha}{1-\alpha}\right)$$

$$10^{pH-pK_\mathrm{a}} - (\alpha 10^{pH-pK_a}) = \alpha$$

$$10^{pH-pK_a} = \alpha + \alpha 10^{pH-pK_\mathrm{a}}$$

$$10^{pH-pK_a} = \alpha(1 + 10^{pH-pk_a})$$

$$\left(\frac{10^{pH-pK_a}}{1 + 10^{pH-pK_a}}\right) = \alpha$$

divide numerator by itself = 1 and thus also divide denominator by the numerator.

$$\left(\frac{10^{pH-pK_a}}{10^{pH-pK_a}}\right)/\left(\frac{1+10^{pH-pK_a}}{10^{pH-pK_a}}\right) =$$

$$\left(\frac{1}{1+10^{pH-pK_a}/10^{pH-pK_a}}\right)$$

working out the denominator:

$$\left(\frac{1}{10^{pH-pK_a}}\right) + \left(\frac{10^{pH-pK_a}}{10^{pH-pK_a}}\right) ->$$

$$\left(\frac{1}{10^{pH-pK_a}}\right) +1$$

now work out the last fraction:

$$\left(\frac{1}{10^{pH-pK_a}}\right) = \left(\frac{1}{10^{pH} \times 10^{-pK_a}}\right) = (10^{pH})^{-1} \times (10^{-pK_a})^{-1}$$
finally gives:

$$\alpha = \left(\frac{1}{10^{pK_a-pH}+1}\right)$$


texts: What does the negative superscript in the term symbol for ground state Oxygen stand for?

texts:
I think that I understand most of the parts of the symbol shown for ground state oxygen $\ce{{}^{16}O2}$, which is ${}^{3}\Sigma^{-}_{g}$.

However, I was hoping that someone could tell me what exactly the negative superscript sign means? And how do you identify between a positive and negative state? I think it has something to do with a mirror plane.


texts: Why is [PdCl4]2- square planar whereas [NiCl4]2- is tetrahedral?

texts:
The molecule $\ce{[PdCl4]^2-}$ is diamagnetic, which indicates a square planar geometry as all eight d electrons are paired in the lower-energy orbitals.

However, $\ce{[NiCl4]^2-}$ is also $\mathrm{d^8}$ but has two unpaired electrons, indicating a tetrahedral geometry.

Why is $\ce{[PdCl4]^2-}$ square planar if $\ce{Cl}$ is not a strong-field ligand?


texts: Is it 'Phenyl' or 'Phenol' that is used as a cleaning agent?

texts:
I often see Phenyl written on cleaning agents in stores. Here are some examples:

One day, a guy standing beside me at a store picked up a bottle of phenyl/phenol and he said, "The big corporation got it wrong. It's phenol, not phenyl."
I looked up the definition of Phenol, and it reads:

A toxic white soluble crystalline acidic derivative of benzene; used in manufacturing and as a disinfectant and antiseptic; poisonous if taken internally

This is what it says for phenyl:

A hydrocarbon radical (C6H5) regarded as the essential residue of benzene, and the basis of an immense number of aromatic derivatives

I am not a student of chemistry, so I don't know what's right or wrong here. But I want to know whether the big corporation got it right or wrong.
It would be nice if anyone here can explain this in the layman's terms.

This is what the pack says:
Ingredients: Coaltar acids and oils, phenolic compounds.
Pesticide/bactericide/fungicide/germicide.
It is a highly concentrated Phenyle, dilute 1 part phenyle with minimum 100 parts of water, resulting in a pinkish white solution.
Black Disinfectant Fluid - Phenolic type
Class Black Type Normal Grade 3


texts: Why don't electrons pair up in an oxygen radical?

texts: In an oxygen radical (produced by the break down of O3 for instance), there are 2 unpaired electrons in the outermost subshell which make the molecule unstable. Why don't these electrons pair up which would make the atom more stable (I think)?


texts: How to predict amine donor in biochemical reactions (whether glutamine or aspartate)?

texts:
In biochemical reactions amine $(\ce{-NH2})$ transfer is done in multiple pathways (e.g. urea cycle, purine biosynthesis etc.).
In many of the situations glutamine donates amine group (e.g. xanthosine monophosphate → guanosine monophosphate). In few instances, however, aspartate donates amine $(\ce{-NH2})$ group (e.g. inosine monophosphate → adenosine monophosphate).
This seems to be very random to me. Is there any pattern in such amine transfer reactions? Can we generalise it in some way?


texts: Why do lipids in a cell hydrolyze into glycerol and fatty acids?

texts:
Most Lipids in a cell have ester bonds (made up of glycerol and fatty acids).

I have learned in my chemistry class that we can hydrolyze an ester by simply adding water to it.

$$\ce{CH3COOCH2CH3 + H2O <=>[H^+ (aq)] CH3COOH + EtOH}$$

Then why do lipids which  have an ester bond don't hydrolyze inside a cell which is 70 percent  water? While searching throught web I have found this link which explains of different ways to hydrolyze an ester. In that it explains about how to hydrolyze esters using dilute acids like HCl. In our stomach HCl is present so logically HCl should destroy the ester in stomach lining (which are made up of cells) instantaneonusly, but this is not happening. Why?

$%edit$


texts: Origin of electrode potential and its connection with electric double layer

texts:
Recently, I was learning about electrode processes and I came across the topic of "electrode potentials".
I understood that at equilibrium, a potential difference was generated at the interface between the electrode and the electrolyte because of the formation of an electric double layer.
I was reading
this
article which says that on dipping metals into their respective salt solutions, positive ions readily form and move into the solution leaving behind electrons in the electrode and a dynamic equilibrium is achieved soon.
Across different metals, only the position of the equilibrium (magnitude of negative charges on the metal electrode) differs due to their differing tendencies to oxidize (or reduce).
(I understood this part)

On the other hand,
I’ve also seen in some other texts that at equilibrium, the charge acquired by the metal might be either positive or negative depending on its tendency to oxidize (or reduce)
(unlike the $1$st source where they say the charge will be always negative).
Examples of
$\ce{Zn}$ ($\ce{Zn}$ has greater tendency to form $\ce{Zn^2+}$ ions hence metal acquires negative charge)
$$\ce{Zn<=>>Zn^2+ + 2e^-}$$
and
$\ce{Cu}$ ($\ce{Cu^2+}$ ions have greater tendency to get reduced hence $\ce{Cu}$ metal acquires positive charge)
$$\ce{Cu^2+ + 2e^-<=>>Cu}$$
are usually given.
(I also understood this explanation)

But what is confusing me is which of the above explanations is correct (or more accurate)?
Because if we go by the $2$nd view,
we have that $\ce{Cu}$ ions are more likely to get reduced so let’s say the $\ce{Cu}$ electrode becomes positively charged when ions from the solution stick to the metal, but at the same time few other $\ce{Cu}$ atoms in the metal will also get oxidized (because there are limited electrons in the $\ce{Cu}$ electrode) and dissolve so there’s no net oxidation or reduction. If this indeed happens then at equilibrium the $\ce{Cu}$ electrode will have no net charge (which isn't possible).

Note-I've seen a few other answers here on this site like this, this and this but none of these seem to address the confusion I'm having.
Any suggestion will be of great importance.


texts: I am working on Enzyme Assay.I assayed the enzyme in different buffers from $pH\ 1-12.5$ However,the enzyme has good activities starting from $pH\ 1-10.5$ Is that possible to have enzyme activity in such broad range ?


texts:
Rank the compounds below in order of increasing C=O absorption frequency in IR spectrum (top - lowest wavenumber, bottom - highest wavenumber):

Question: Would I count compound #1's cyclopentane or all 11 carbons because wavenumber increases with 5C or smaller rings.

If I count #1 as a cyclopentane for this purpose then #3 has the lowest wavenumber and #2 has the highest.


texts:
In a study I have run into some questions asking for "How many atoms are contained in the unit cell" for graphene. I have some trouble understanding the unit cell of graphene which is always depicted as a mono-layer of atoms. What is a unit cell in a mono-layer?

The closest I could find is something like this picture:

The upper right image shows something soon-to-be a hexagonal structure. But when is such structure actually appearing?


texts:
I have a very vague knowledge of thermodynamics, but let's take a reversible reaction:

$$\ce{CaCO3 (s) <=> CaO(s) + CO2(g)}$$

Now if we increase the mass of the calcium carbonate, I understand that it would not increase the concentration by a very large approximation (since it's density does not increase by a very large approximation) so I understand that the equilibrium will not shift to the right, but the thing that confuses me is doesn't more reactant mean more product and a greater yield means a shift to the right? This also applies to a pure liquid reaction:

$$\ce{HCl(g) + H2O(l) <=> H3O+ + Cl-}$$

Let's assume that in the first reaction you have a mole ratio of the respective reactants in the form of 1:0.5  clearly water is a limiting reagent, however let's assume that we increase the mass of the pure liquid so that the mole ratio becomes 1:1 now we have more water available for the reaction to occur hence more product would occur, but according to le Chateliers principle this would not occur since a pure liquid does not cause a shift, rather if the reaction was at equilibrium it would remain as so. Why does this happen?


texts: Flame test: Is the metal atom or the metal ion responsible for the flame colour?

texts:
A sample of $\ce{CaCl2}$ is placed in the flame of a Bunsen burner. The component of the substance which is responsible for the production of the flame colour is:

$\ce{Ca^2+}$
$\ce{Ca}$
$\ce{Cl-}$
$\ce{Cl}$

Why is the textbook answer $\ce{Ca}$ and not $\ce{Ca^2+}$ ?


texts: When did the atom Theory Become indisputable?

texts:
We know that the Greeks were the first scientists (or better, philosophers) to introduce the idea that matter is made up of little “chunks”, and they named these chunks “atoms”. This idea that matter comes in discrete small pieces was termed wrong and right over centuries when John Dalton, in the 19th century, constructed a theoretical framework in which he could explain in an elegant way the work of scientists such as Joseph Priestley and Antoine Lavoisier on qualitative and quantitative properties of matter and its transformations.
The framework which John Dalton used to better understand the work of other scientists had in its core the “language” of atoms, that is, he used the concept of atoms to explain, for example, why reactions only occurs if we have quantities “in proportion”. Note that the work of John Dalton doesn't proof that atoms are real, it only shows that thinking of matter in terms of atoms is a suitable way to understand the results coming out of experiments.
Scientists only proved that atoms are real at the beginning of the 20th century, and that discovery gave birth to Quantum Mechanics.

Now comes my question:
When did scientists prove that molecules “are real”? In other words, what is the history of the discovery of (the shape of) molecules?

Scientists have been playing around with toy models of particles for a long time but only a short time ago IBM researchers managed to “take a picture” of an actual molecule, and its configuration matches exactly the models we've been using for a long time, for example this pentacene molecule:

When did we first learn that molecules have a “geometry”? That is, an exact arrangement in space?


texts: Why is the pH level of carbonation loss decreasing then increases afterwards?

texts:
We have done an experiment of the titration of unsealed sprite soda to find the amount of carbonic acid being loss on various duration (0 to 1 hour), due to decrease pressure.
The calculation was to determine the pH of carbonic acid overtime, thus the number of concentration of flat and unsealed soda are subtracted and is converted to pH level using -log[concentration of flat soda - unsealed soda].This was done multiple times on multiple duration until 1 hour. Now the results has demonstrated that carbonic acid pH level was decreasing in the first 30 minutes but then afterwards it was increasing. This contradicts on what my hypothesis is as it states that due to pressure being decreased (by unsealing the soda) the pH will increase turning more basic. Is this due to the factors of pressure and temperature? Can you please describe this thoroughly? Thank you for your time on reading this.


texts: How to detect nM levels of Copper(I) Oxide in blood?

texts: I'm trying to design an experiment to detect nM quantities of Copper(I) Oxide in fish blood. Are there any specific tests for Copper(I) Oxide that can be used to detect trace quantities(~nM)? Any non-destructive tests such as using optical methods would be preferable.For purposes of designing the experiment, let's assume the particles are nano-sized and dispersed in blood.


texts: Formic acid and carbon monoxide outgassing from latex mattress

texts:
Formic acid is used as a coagulant to turn rubber tree sap into latex, formic acid also decomposes to carbon monoxide. Does this mean things like latex mattresses have the potential to off-gas carbon monoxide? I am assuming they don't, but I have had carbon monoxide poisoning twice, so I would like to buy a latex mattress and I don't need $\ce{CO}$ issues for the third time.

If this isn't an appropriate forum for this question and you can point me in the direction of one that is that would be great.


texts:
I tried to understand how does a battery work. After doing some research, I knew chemical reactions inside are key. But when I came across the reactions inside a zinc carbon battery, almost all websites say "Zinc is oxidized and gives out two electrons".

Why does this reaction happen in the first place? Is it the result of the reaction between the electrolytes and the zinc? And I'm confused what exactly do electrolytes do because I saw they are described as "catalyst". I only understand they allow the flow of ions but prevents the flow of electrons.

Thank you and if what I say above is wrong, please correct me.


texts: What are some popular science books in chemistry?

texts:
I have been reading the books The Elements by Theodore Gray and Stuff Matters by Mark Miodownik, both being very popular chemistry science books. Are there some other easy-to-read, popular but scientifically accurate chemistry books available?

The answer to the question should not be "primarily opinion based", since "popular" can be measured.


texts: Systematic IUPAC names for beta-glucose and lactic acid

texts:
What are the IUPAC systematic name for $\beta$-glucose and lactic acid (as in the monomers used in polymerization for PLA)?

For lactic acid, I found this:

  2-hydroxypropanoic acid

Is this correct?

For $\beta$-glucose, I have not find anything conclusive so far. I did find on this site (Carbohydrates) that "carbohydrates have been given non-systematic names". Is this true, and does that imply that "$\beta$-glucose" is simply $\beta$-glucose?


texts: How can a vacancy defect be a stoichiometry defect?

texts:
NCERT (India) explain stoichiometric defects as those defects which do not disturb the stoichiometry of the solid. Vacancy defects are stated to be under the category of stoichiometric defects. When some lattice sites are vacant, the crystal is said to have a vacancy defect.

My question is: if lattice points are missing in vacancy defects, shouldn't this disturb the stoichiometry of the compound? I think yes but the book states no. Why?


texts: I understand that $k_\text{cat}$ measures the turnover number of an enzyme. This measure is therefore a quantity of molecule conversions per unit of time. I suspect that my problem is more that of a lack of maths but why is the unit expressed in $\mathrm s^{-1}$? Why not just seconds?


texts: The Crisscross method for finding the chemical formula

texts:
I am reading this wikipedia article that I don't understand. What I don't understand is:

  suppose we have two elements $X$ and $Y$ having oxidation numbers $x$ and $y$ respectively. Can we prove that the compound formed will be $X_yY_x$.

I tried to understand this method as: I think this method comes from the fact of charge neutrality. Suppose the compound to be formed has formula $X_{y'}Y_{x'}$. The charge on $y'$ number of $X$ elements is $xy'$. The charge on $x'$ number of $Y$ elements is $x'y$. Now by charge neutrality we should have : $$|x|y'=x'|y|$$
 this implies $\dfrac{|x|}{|y|}=\dfrac{x'}{y'}$.

  But I could not further understand why the we divide $x$ and $y$ with their greatest common factor to find the required solution.

I have also found some contradiction examples to this Crisscross rule. Example is : Solid-state-semiconductor $GaAs$, in this Gallium has valancy $3$ and $As$ has valancy $5$.
 The main points on which I want answers are:

  What is the logic behind this method, how to prove this method?
  Who, how and when developed this method?
  Is this method only applicable to ionic compounds?
  Why compounds like $GaAs$ do not follow this rule, how charge neutrality is preserved in these compounds. I think these don't follow this rule because these are not ionic compounds, if yes then how the chemical formula of compounds like solid state $GaAs$ is known(or decided) and how it is justified, how one atom of $Ga$ balances one atom of $As$ ,their valencies are different, how they are bonded(covalently I guess) together?


texts: Is rearrangement possible in cyclic bromonium ion?

texts:
I wonder what the product of the above reaction is, that is, bromination of the given alkene in non polar solvent carbon tetrachloride (proceeds through cyclic bromonium ion intermediate).

Once the cyclic bromonium ion is formed, can the ring expand as shown or is the usual product formed? Five remembered rings happily expand to six membered ones if possible - so what's going on here?

It'd be great if you could quote sources with your answer - and help me understand whether or not species involving cyclic bromonium ions can rearrange in a reaction, and why?

Thanks!


texts: Why are acids usually depicted in fiction as green?

texts:
In cartoons, etc., acid is generally shown as vividly green, as in this scene from the Simpsons:

We even have the colour "acid green".

But when I used to use acids in chemistry class, they weren't bright poisonous green. They were mostly colourless, as, for example, this picture of sulfuric acid from Wikipedia:

So where does this idea of green acid come from? Are there acids which are actually green? Or perhaps acids are green when highly concentrated?


texts: How dangerous is taking a bath in Coca Cola?

texts:
What can be the effects for the body to be immersed in Coca Cola for a while? A friend commented me that the coke is quite acidic (pH 2.5 if I recall properly), and we were guessing what could be the effects for the body after a time of immersion.

I read 20 Practical Uses for Coca Cola – Proof That Coke Does Not Belong In The Human Body and I see some things like:

  E338 – Orthophosphoric Acid. This can cause irritation of the skin and
  eyes.

But I am guessing: what are the problems of a long contact of coke with the body - not drinking, but being in touch with it.


texts: What is the name of the crinkly plastic used in clear parts of envelopes?

texts: I've always wondered what it is, as it makes a lot of noise on being deformed. No other common plastic that I've come across has quite the same properties.