texts: Is order defined for a reaction which does not follow power law dependence?

texts:
As per my knowledge , order of a reaction is the sum of exponents of all the terms in rate law of the reaction
But reaction which do not follow power law dependence , for example , formation of HBr , is order defined for such reactions also ? If yes , how is determined ?
Thanks !


texts: How can a decomposition reaction be exothermic?

texts:
Decomposition reactions involve breaking of bonds which requires energy. Therefore, they are generally endothermic.

But how can decomposition reactions release energy? Examples are the respiration reaction or the decomposition of vegetable matter.


texts: How to find the ionization constant of an unknown weak acid?

texts:
A $\pu{0.45 M}$ solution of a weak acid, $\ce{HX}$, has a $\pu{pH}$ of $4.5$.  What is the ionization constant, $K_a$, of the acid?

$\ce{[HX]}$ is already given as $\pu{0.45 M}$.
$\ce{[H+]}$ is given by $10^{-4.5}$.

Since $\ce{pH}$ is $4.5$, $\ce{pOH} = 14 - 4.5 = 9.5$. Then we can get $\ce{[OH^-]}$ by computing $10^{-9.5}$.

Then computing $K_a$, I get
$$\frac{10^{-4.5} \cdot 10^{-9.5}}{0.45} = 2.22 \times 10^{-14}.$$
But that is apparently not the right answer. What did I do wrong?


texts: Difference in mechanisms between formation of acetal and enamine

texts:
When forming acetal from a C=O group with alcohol, the alcohol will act as a nucleophile and attack twice as the carbon is made very electrophilic twice.
I wonder in the last intermediate before forming the enamine, is it able for the 2' amine to act as a nucleophile and attack the carbon bonded to a highly electronegative N with a positive formal charge? (like the attack from the alcohol when forming acetal) Then with the help with 1 proton transfer, forming a product that has 2 RR'N?
My thought is that it may be too sterically hindered compared to the alcohol when attacking. But is it valid?


texts: Correlation between electron counting and structure for metal borides

texts:
When it comes to metal borides, the electron counting and its correspondence to structure seems weird. For instance, $\ce{MgB2}$ and $\ce{AlB2}$ are isostructural, which is surprising.

Further consider the example of metal hexaborides. $\ce{MB6}$ structures are isostructural for  $\ce{M}= \{\ce{Ca}, \ce{La}, \ce{Th}, \ce{Ce}, \ce{K}\}$. How does the bonding in in these metal diborides, hexaborides, and so on occur?


texts: Hydrogen atom transfer between enantiomers of rac-1-phenylethanol

texts:
(Taken from Dalton Trans., 2012, 41, 13423–13428. DOI:10.1039/c2dt31781h)

I have difficulties understanding the hydrogen transfer in the image above. I always thought that hydrogen transfers followed the following formula:

$$\ce{X^. + H-Y -> X-H + Y^.}$$

I can't really see the connection between the picture and the formula. Is it the whole ethanol group that is transferred?


texts:
What is the most logical and easy to remember step by step method for drawing Lewis dot structures?
I'm having trouble drawing a simple one for $\ce{CO2}$.


texts: How to calculate the final temperature of a gas when it undergoes adiabatic expansion?

texts:
The question is as follows:

  A sample of $\pu{4.0 moles}$ of a gas ($C_{v,m} = \pu{21 J mol-1 K-1}$) has an initial pressure of $\pu{304.4 kPa}$ and an initial volume of $\pu{20 dm3}$ at $\pu{270 K}$. It undergoes an adiabatic expansion against a constant external pressure of $\pu{79.8 kPa}$, until the volume has increased by a factor of $3$. Calculate the final temperature.

I have calculated:  $Q = 0$  and $w = \pu{-3192 J}$ and change in internal energy $=\Delta U = \pu{-31922 J}$.

The next question is to calculate the final temperature of the gas. However, I am unsure on how to calculate this. Originally I thought as $Q=0$, then the final temperature would be the same as the initial temperature. However, I have realized this is incorrect.


texts: What reaction takes place when potassium iodide is added to a tetraammine copper(II) complex?

texts: I am given a blue solid W and it contains a tetraamine copper(II) complex and a $\ce{SO_4^{2-}}$. I added dilute sulfuric acid until the solution is pale blue; then added potassium iodide solution. A white precipitate forms ($\ce{CuI}$) in a brown solution ($\ce{I_2}$). However, I am confused about what reaction is actually going on.


texts: Can an atom bond with more than 8 other atoms?

texts:
Is it possible for an atom to bond with 8 other elements (same or other type)? If yes, then please give some examples. If no, then what could be the possible reason for it?

My question is not about valence shell electrons. My question is about whether an element could combine with more than 8 other same or different elements? It could be rather covalent bonds or any bond.


texts: Why has no one ever been able to synthesise cyclopentyne as a stable molecule? I've been thinking about this for quite some time and I can't seem to figure it out. Something to do with angular strain in the molecule?


texts: Can gaseous hydrogen and gaseous oxygen be compressed without reaction?

texts:
I'm looking into building a clean Bunsen-style burner (or rocket engine - I haven't decided yet). I will be using electrolysis to extract hydrogen and oxygen from water, but the apparatus I am thinking about building will render gaseous hydrogen and gaseous oxygen, but in a mixture. Preferably I would store them compressed, and not have spontaneous combustion.

My question is this:
Will gaseous hydrogen and gaseous oxygen react with each other if compressed in the same chamber?If so, how much pressure is required before it blows up?


texts: What volume does one mole of an ideal gas occupy?

texts:
This has been bugging me for a while now...

Obviously, to calculate the volume/space occupied by a mole of (an ideal) gas, you'll have to specify temperature ($T$) and pressure ($P$), find the gas constant ($R$) value with the right units and plug them all in the ideal gas equation $$PV = nRT.$$

The problem? It seems to be some sort of common "wisdom" all over the Internet, that one mole of gas occupies $22.4$ liters of space. But the standard conditions (STP, NTP, or SATP) mentioned lack consistency over multiple sites/books. Common claims: A mole of gas occupies,

$\pu{22.4 L}$ at STP
$\pu{22.4 L}$ at NTP
$\pu{22.4 L}$ at SATP
$\pu{22.4 L}$ at both STP and NTP

Even Chem.SE is rife with the "fact" that a mole of ideal gas occupies $\pu{22.4 L}$, or some extension thereof.

Being so utterly frustrated with this situation, I decided to calculate the volumes occupied by a mole of ideal gas (based on the ideal gas equation) for each of the three standard conditions; namely: Standard Temperature and Pressure (STP), Normal Temperature and Pressure (NTP) and Standard Ambient Temperature and Pressure (SATP).

Knowing that,

STP: $\pu{0 ^\circ C}$ and $\pu{1 bar}$
NTP: $\pu{20 ^\circ C}$ and $\pu{1 atm}$
SATP: $\pu{25 ^\circ C}$ and $\pu{1 bar}$

And using the equation, $$V = \frac {nRT}{P},$$
where $n = \pu{1 mol}$, by default (since we're talking about one mole of gas).

I'll draw appropriate values of the gas constant $R$ from this Wikipedia table:

The volume occupied by a mole of gas should be:

At STP
\begin{align}
T &= \pu{273.0 K},&
P &= \pu{1 bar},&
R &= \pu{8.3144598 \times 10^-2 L bar K^-1 mol^-1}.
\end{align}
Plugging in all the values, I got
$$V = \pu{22.698475 L},$$
which to a reasonable approximation, gives
$$V = \pu{22.7 L}.$$
At NTP
\begin{align}
T &= \pu{293.0 K},&
P &= \pu{1 atm},&
R &= \pu{8.2057338 \times 10^-2 L atm K^-1 mol^-1}.
\end{align}
Plugging in all the values, I got
$$V = \pu{24.04280003 L},$$
which to a reasonable approximation, gives
$$V = \pu{24 L}.$$
At SATP
\begin{align}
T &= \pu{298.0 K},&
P &= \pu{1 bar},&
R &= \pu{8.3144598 \times 10^-2 L bar K^-1 mol^-1}.
\end{align}
Plugging in all the values, I got
$$V = \pu{24.7770902 L},$$
which to a reasonable approximation, gives
$$V = \pu{24.8 L}.$$

Nowhere does the magical "$\pu{22.4 L}$" figure in the three cases I've analyzed appear. Since I've seen the "one mole occupies $\pu{22.4 L}$ at STP/NTP" dictum so many times, I'm wondering if I've missed something.

My question(s):

Did I screw up with my calculations?
(If I didn't screw up) Why is it that the "one mole occupies $\pu{22.4 L}$" idea is so widespread, in spite of not being close (enough) to the values that I obtained?


texts: 3-ethyl-2-methylpentane-2,3-diol with sulfuric acid

texts: I was studying pinacol pinacolone reaction when I came across this. I believe the hydrogen cation will attack the hydroxyl group of carbon attached to two ethyl groups (since this carbocation is more stable due to the inductive effect), then methyl group will migrate and hence we get 3-ethyl-3-methylpentan-2-one, but the book says the answer is 2-ethyl-2-methylpentan-3-one. Is the answer in the book wrong or I am making a conceptual mistake?


texts: What is the reason for an increase of back-pressure of HPLC column?

texts:
Recently i have observed that the back pressure in my HPLC reverse phase column increased almost twice, and sometimes after sample injection the pressure increased so high that removed the connector of column.
What is the reason for that, even though I am using HPLC grade solvents, In my point of view may be some impurities stuck inside. I have washed my column with methanol for long but it's seems useless.
Is there anything which can i do to solve this problem, because the column is expensive and don't have funds in lab to buy another one.


texts: Why neglecting OH Ions from charge balance?

texts:
I have a problem, in which the concentration of $\ce{Ca^{2+}}$ ions in water should be related to the partial pressure of $\ce{CO2}$ (assuming the water is an open system and in equilibrium with atmosphere).

All the approaches I saw so far, started by looking at the charge ballance of this system:

$$\ce{2 [Ca^{2+}] + [H+]} =\ce{2[CO3^{2-}] + [HCO3-] + [HO-]}$$

This is totally logical. But they continue with the assumption that the terms $\ce{[CO3^{2-}]}$,$\ce{[HO-]}$, $\ce{[H+]}$ are insignificantly small so that you can work with:

$$\ce{2 [Ca^{2+}]} =\ce{[HCO3-]}$$

That's the point I don't get.

Assuming at the beginning there is only $\ce{CaCO3}$ and Water. Both dissociate and let's say $\ce{CO3^{2-}}$ immediatly combines with $\ce{H+}$ to $\ce{HCO3-}$, then it is reasonable that the contribution of $\ce{H+}$ and $\ce{CO3^{2-}}$ can be ignored. But what about the remaining $\ce{OH-}$? Stupidly written, I would get something like:

$$\ce{H2O + CaCO3 } =\ce{ HCO3- + Ca^{2+} + OH-}$$

So why can I also neglect the charge caused by $\ce{OH-}$ Ions? For each bicarbonate/calcium-ion produced I would also get a hydronium ion. why can this still be ignored?


texts: Will the bond order of CO be greater in its existence as carbon monoxide or in metal carbonyl?

texts:
$$\text{Bond order} = \frac{N(b) - N(a)}{2}$$
Where $N(b)$ is the number of electrons in bonding orbitals and $N(a)$ is the number of electrons in antibonding orbitals.
As in metal carbonyls, there is synergic effect during formation of the π back bond from metal to $\ce{CO}$, so $\ce{CO}$ accepts electrons in its π* anti bonding orbital. As $N(a)$ increases, Bond order decreases. So, $\ce{CO}$ in its free state has greater bond order in comparison and hence is more stable.
Would the above concept be correct?


texts: Derivation of the Orgel diagram for octahedral d2 complexes

texts:
The Orgel diagram for a typical octahedral $\mathrm{d^2}$ complex is shown below:

(source: Kettle, Physical Inorganic Chemistry, p 146)

I understand that the right-hand half of the graph shows how the energies of electronic states of a $\mathrm{d^2}$ complex vary with the ligand field splitting $\Delta$.

However, neither the Wikipedia page nor the LibreTexts (formerly UC Davis ChemWiki) page are helpful in describing how this diagram is constructed. In particular, I have a few questions:

What are the "weak-field" and "strong-field" limits?
How are the symmetry labels for the electronic states constructed?
How are their relative energies determined?
Why are some of the lines straight, but others curved?
Why is the diagram also used for $\mathrm{d^3}$, $\mathrm{d^7}$, and $\mathrm{d^8}$ complexes (both octahedral and tetrahedral)?


texts: Can an ant etch a hole in a tent with formic acid?

texts:
Given a polymer foil tent, could ant's formic acid help to etch a hole in it? I thought of a polyester or polyamid foil. If one ant's acid is not enough, they come as team.

This is not a theoretical question beacause I have observed it on a camping in South France. I am not just sure whether they just bite through, or indeed use their acid.

https://ibb.co/m5u5B8


texts: Side products during the electrolysis of Copper Sulfate?

texts:
Using good quality reagents, during the electrolysis of $\ce{CuSO4}$ (at $\mathrm{15V ~ \& ~ 2A}$), I have noticed a significant amount of Hydrogen generated at the negative electrode in addition to copper deposition.

This generation occurred at all voltages, which surprised me. I expected a only the reduction of copper in the reaction. The solution was blue, so I know that copper sulfate was still in solution. At first, I thought that the copper might be reacting to the sulfuric acid being generated, but the copper that has fallen off the electrode is not bubbling.

I am using a platinum and copper electrodes.

Is $\ce{H2}$ generation happening as a result of the weak sulfuric acid in solution?

Can you calculate the products of simultaneous electrochemistry reactions?


texts: Self tan mousse cannot contain UV, right?

texts:
So, I bought this self tanner specificly to avoid UV radiation. Back home I noticed that the bottle says it contains ultra violet: "The inclusion of Ultra Violet fluorescence in the base colour" . I guess they meant it contains something fluorescent but what could it be and is it dangerous? (sorry about my bad English)

The product is Sunkissed Ultra Dark Selfie Ready Tan.


texts: Why does a liquids height in a Barometer depend linearly on pressure?

texts:
Here is a derivation I found relating the pressure P, gravity g, height h, and density $\rho$, of a liquid in a barometer

$$
P=\frac{mg}{A}\\
V=Ah \\
P = \frac{mgh}{V}\\
\rho=\frac{m}{V}\\
P = \rho g h
$$

However, this derivation seems misguided, since $P = \frac{F}{A}$, and P is the pressure of the gas, not of the liquid, as the derivation later relates it to.

Furthermore, it doesn't make sense to me that the height of the liquid and the pressure are necessarily linearly related. Wouldn't this depend on the compressibility of the liquid? Or rather, it seems like depending upon the properties of the liquid, it may be very difficult to change the height past a certain point, for example. In this sense the added energy from increasing the pressure goes into bonds or is stored in electrical interactions.


texts: Equilibrium for very small amounts of reactants

texts:
Is there any difference in the concept of equilibrium when it comes down to dealing with extremely small amounts of reactants?

Say we have $$\ce{A + B <=> C + D}$$
 and $K_c$ is $100,000$. If we only have $10$ atoms of each $\ce{A}$ and $\ce{B}$ in a beaker, we would expect the container to be totally full of $\ce{C}$ and $\ce{D}$. But $K_c$ is not infinite, so there must be some unreacted $\ce{A}$ and $\ce{B}$. However, if there was even one atom of reactants, the reaction would quickly shift back to satisfy the equilibrium.

Does the concept of equilibrium only apply to macro-sized reactions? Is there an extendable concept for the micro scale?


texts: Is there any food-safe way to break down capsaicin (chilli) so food is less spicy?

texts:
That is, is there a chemical or enzymatic reaction with capsaicin that break it down into other food-safe chemicals? Or alternatively, bind to capsaicin such that it doesn't trigger the same spicy receptors in our mouths.

I know about how casein can be used to wash capsaicin away, but it doesn't actually change it into another form or deactivate it.


texts: Does sulfur and phosphorus expand their octet?

texts:
There are many compounds in which the stability of a molecule is not governed by the presence of octet configuration in central atom. In most of the cases the central atom is generally sulfur or phosphorus. In these cases either the central atom has 6 electrons, or sometimes the electron count exceeds 8 and 10 or 12 electrons in its valence electron shell.

This makes the concept of octet somewhat incorrect. My question is how can they increase their octet to such an extent?

Could someone explain this in relation with sulfur trioxide?


texts: What is the difference between X-ray photoelectron spectroscopy and X-ray absorption spectroscopy?

texts:
XPS is used for surface chemical state identification.
But other than that, is XAS just an inverse of XPS?


texts:
I have two questions regarding this solution:

I can't see how the structure drawn is the enantiomer.
How do I rotate the ring inversion chair form to obtain the enantiomer?


texts: My question is: what is the best way to extract micro RNA (miRNA) from humans plasma? Whether trizol is suitable, or should I use commercial kits? Thanks


texts: Confusion about the relation between gibbs free energy and electromotive force

texts:
$$\Delta G = -nFE$$

My textbook says that we can measure that this $\Delta G$  is measured when the work is done reversibly. But my confusion is how will we work reversibly when we have an electrochemical cell? And what guarantee do we have that while measuring $\Delta G$, E will remain constant? Isn't it possible that after 0.25 moles of electrons have reacted, E would change because it depends on concentration.


texts:
Does E-factor include all of the reagents including catalysts, solvents, and reactants that go into making the product? Further, in the E-factor calculation should all the solvents used in work-up (such as water and ammonia solution) also be included?

$$\text{E-factor} = \frac{\text{total waste}~(\pu{kg})}{\text{product}~(\pu{kg})} = \frac{(\text{total reagents} - \text{product})~(\pu{kg})}{\text{product}~(\pu{kg})}$$


texts: Schrödinger equation and degeneracy of atomic orbitals

texts: How does the application of the Schrödinger equation to model a system, such as a particle in a box, help us understand the origin of the degeneracy of atomic orbitals?


texts: On heating will gold hydroxide $\ce{Au(OH)3}$ decompose to form pure gold or will a gold oxide (e.g. $\ce{Au2O3}$) be stable? Does anyone know the temperature of these reactions?


texts: Why note the solvent level on chromatography paper when it is removed from the chamber?

texts: Why is it important to mark solvent level on chromatography paper when you remove it from the chamber?


texts: How to figure out if the reaction proceeds via SN1 or SN2 mechanism?

texts:
I have been assigned with the task of figuring out whether a reaction is $\ce{S_{N}1}$ or $\ce{S_{N}2}$. The information that I have is, that the yield is dependent on solvent polarity. More specifically, the higher the solvent polarity, the higher the yield.
The problem is that both $\ce{S_{N}1}$ or $\ce{S_{N}2}$ products are the same. Both result in charge separation (therefore both are favored by polar solvents).

I proposed to repeat the experiment. I proposed to make the site of substitution chiral. That way it is possible to check for $\ce{S_{N}2}$ inversion.
Another proposal was to use the fact that the rates of $\ce{S_{N}2}$ and $\ce{S_{N}1}$ were different. However, I am not sure how to use this fact and perform an experiment.

What should I do in this situation? The people that I am working for do not want to repeat the experiment at all. Using the rates approach seems to be the best option since there won't be a need to obtain new materials. But I have no idea on how to do this. What are your suggestions? How can I figure out whether the reaction proceeded through $\ce{S_{N}1}$ or $\ce{S_{N}2}$ by using rates approach?


texts:
While learning about Carbon and its Compounds in a class 10 coaching, I suggested a structure for some isomers.
It contained a connection of two consecutive carbons connected by double bonds. The teacher said that it can be counted as one, but is not a stable compound.
A recent research on C18 carbon carbon chain allotrope involved alternating triple bonds.
My question is, why is consecutive connection of carbon atoms via double bonds not stable, whereas an alternating triple Bond chain is found to be existing? Also explain some physics behind it


texts: Analytical solution for kinetics of bimolecular reaction

texts:
Consider two chemicals, $\ce{A}$ and $\ce{B}$ that react with each other to make $\ce{C}$ with a reaction rate $k$. The reaction can be expressed as $$\ce{A + B->C}$$ The equation expressing the rate of the reactions can be expressed as $$\frac{d[\ce{A}]}{dt}=\frac{d[\ce{B}]}{dt}=-\frac{d[\ce{C}]}{dt}=-k[\ce{A}][\ce{B}]$$

I can separate this equation to make a system of differential equations.$$\frac{d[\ce{A}]}{dt}=-k[\ce{A}][\ce{B}]$$ $$\frac{d[\ce{B}]}{dt}=-k[\ce{A}][\ce{B}]$$

With these two equations, I note that they are similar and will only work with one of these equations for the time being. Therefore, we can write one of these equations as $$\frac{d\ln([\ce{A}])}{dt}=-k[\ce{B}]$$ and by taking another derivative $$\frac{d^2 \ln([\ce{A}])}{dt}=-k\frac{[d\ce{B}]}{dt}=-k\frac{[d\ce{A}]}{dt}$$

I solved this equation using Wolfram Alpha (QED) $$[\ce{A}](t)=\frac{c_1 \exp[c_1(t+c_2)]}{k \exp[c_1(t+c_2)]-1}$$ Therefore the rate of reaction can is $$[\ce{A}]'(t)=\frac{c_1^2 \exp[c_1(t+c_2)]}{k \exp[c_1(t+c_2)]-1}-\frac{k c_1^2 \exp^2[c_1(t+c_2)]}{(k \exp[c_1(t+c_2)]-1)^2}$$

I observed that the rate of change can be written as $$[\ce{A}]'(t)= c_1 [\ce{A}](t)-k [\ce{A}](t)^2$$ so that $c_1$ may be solved, given the initial conditions of $[\ce{A}](0)$ and $[\ce{A}]'(0)$ such that $$c_1=\frac{[\ce{A}]'(0)+k[\ce{A}](0)^2}{[\ce{A}](0)}$$

Substituting the definition of $c_1$ into the equation of $[A](t)$ and $[A]'(t)$ an equation for $c_2$ can be found.

$$c_2=\frac{1}{c_1} \ln(1-\frac{c_1 k}{[\ce{A}](0)}) $$$$
c_2= \frac{[\ce{A}](0)}{[\ce{A}]'(0)+k[\ce{A}](0)^2}  \ln(1-\frac{[\ce{A}]'(0)+k[\ce{A}](0)^2 }{[\ce{A}](0)^2}k) $$

Using the equations for $c_1$ and $c_2$ an explicit equation for $[\ce{A}](t)$ can be found.

$$ [\ce{A}](t)=\frac{\frac{[\ce{A}]'(0)+k[\ce{A}](0)^2}{[\ce{A}](0)} \exp[\frac{[\ce{A}]'(0)+k[\ce{A}](0)^2}{[\ce{A}](0)}(t+\frac{[\ce{A}](0)}{[\ce{A}]'(0)+k[\ce{A}](0)^2}  \ln(1-\frac{[\ce{A}]'(0)+k[\ce{A}](0)^2 }{[\ce{A}](0)^2}k))]}{k \exp[\frac{[\ce{A}]'(0)+k[\ce{A}](0)^2}{[\ce{A}](0)}(t+\frac{[\ce{A}](0)}{[\ce{A}]'(0)+k[\ce{A}](0)^2}  \ln(1-\frac{[\ce{A}]'(0)+k[\ce{A}](0)^2 }{[\ce{A}](0)^2}k))]-1} $$

Side note: since $[\ce{A}]'(0)=[\ce{B}]'(0)= -k[\ce{A}](0)[\ce{B}](0)$ then $c_1$ can be rewritten as $$c_1=\frac{-k[\ce{A}](0)[\ce{B}](0)+k[\ce{A}](0)^2}{[\ce{A}](0)}=k([\ce{A}](0)-[\ce{B}](0))$$

this simplifies $c_2$ to

$$c_2=\frac{k^{-1}}{[\ce{A}](0)-[\ce{B}](0)} \ln(\frac{[k^2 \ce{B}](0) }{[\ce{A}](0)})$$

which simplifes the equation for $[\ce{A}](t)$ to

$$[\ce{A}](t)=\frac{k([\ce{A}](0)-[\ce{B}](0)) \exp[k([\ce{A}](0)-[\ce{B}](0))(t+\frac{k^{-1}}{[\ce{A}](0)-[\ce{B}](0)} \ln(\frac{[k^2 \ce{B}](0) }{[\ce{A}](0)}))]}{k \exp[k([\ce{A}](0)-[\ce{B}](0))(t+\frac{k^{-1}}{[\ce{A}](0)-[\ce{B}](0)} \ln(\frac{[k^2 \ce{B}](0) }{[\ce{A}](0)}))]-1}$$

with a similar equation for $[\ce{B}](t)$

My quesion is: Is this a valid mathematical model for a bimolecular reaction? If not, what is commonly used?


texts: Does anyone know what program was used to make this molecular structure picture?

texts: I am a quantum chemistry beginer, and this picture color scheme is classic. I wonder how to make such pictures by myself.


texts:
If an element valency corresponds to the group number in the periodic table, oxygen would be 6 right?

The question states; Species: Li, O
I assume Li is 1 and O is 6, so my chemical formula is $\ce{Li6O}$ but the correct answer is $\ce{Li2O}$
Why is the valency of Oxygen 2?

similarly Pb(II) and Iodine, which iodine is in group 7 but just like the answer it said the valency is 1.

 If I drew the electron shells for oxygen I realize there are 2 electron spaces, if I did the same for Iodine there are 7 spaces. so this did not answer my question

then I saw number of bonds = (full valence shell) - (n. of valence electron)
for oxygen it returned 2, through: $8 - 6$
then it was the same for Iodine: $8- 7 $

This did not answer my question either, as Lithium and Sodium correspond with the group number. Am I missing something OR doing something wrong OR is there some sort of principle among this periodic table?

Then it asked, $\ce{Ag}$, $\ce{OH-}$. because Ag is a transition metal, so how do I find its valency? OH is a polyatomic ion, is there a way to find out the valency for polyatomic ion or am I suppose to memorize it for exams?

 The question in my book mostly gives 2 species then asked for the chemical formulas. I'm just very confused at the valency part.


texts: Is it dangerous to inhale the steam coming from electrolysis of salt-water solution

texts: Is chlorine in there that accumulates (at the anode) and emerge out as chlorine gas? I was worried since I added a pinch of salt to the steamer in order to hasten the heating of tap water when I caught a cold (I should've just boiled a pot of water on the stove). I'm worried since chlorine gas is bad for the respiratory system. Also I'm curious to know what is this brown precipitate under the solution - hydroxides or cupric-oxides from the electrode?


texts: Regioselectivity in Diels–Alder reaction between 2-nitrobuta-1,3-diene and acrylonitrile

texts:
Since $\ce{-CN}$ shows strong −I effect, there will be δ+ charge on the carbon adjacent to it. Similarly, $\ce{-NO2}$ shows strong −I and –M effects. So, I proposed that π-electrons are being donated to the electron-deficient parts:

But the answer given in my book has $\ce{-CN}$ group at the third position to $\ce{-NO2}$ group. Can someone please tell me where I have got my concepts wrong?


texts: Why isn't the chemistry of a zinc-air battery (meaningfully) hindered by an activation energy barrier?

texts:
Virtually every source I've read pertaining to zinc-air batteries explain the chemistry of it either using these formulae or a simplified version of them:
$$
\begin{align}
&\text{Anode:} &\quad \ce{Zn + 4 K(OH) &-> [Zn(OH)4]^{2-} + 4 K+ + 2 e-} \\
&\text{Electrolyte:} &\quad \ce{[Zn(OH)4]^{2-} + 2 K+ &-> ZnO + 2 K(OH) + H2O} \\
&\text{Cathode:} &\quad \ce{1/2 O2 + 2 K+ + H2O + 2 e- &-> 2 K(OH)}
\end{align}
$$
For all intents and purposes, I believe it is acceptable to simplify the formulae (correct me if I'm wrong).
How does the anode reaction occur in the first place without some sort of catalyst? It momentarily pushes the system out of equilibrium, at least until the cathode reaction can occur, so I would think that the activation barrier would be some significant obstacle. What am I missing?
Apologies if this is a secretly a simple question, I'm not very adept in chemistry.


texts: In the following reaction is E2 or Sn2 favorable?

texts:
Question

Doubt

It is quite obvious that carbonyl compound is going to convert into alkane, but what confuses me is whether Sn2 or E2 will occur at bromide position

Although there is heating( which I believe favour E2) and a strong base, the carbon is 1° which would favor SN2 more than E2.
Please help.


texts: Comparing formula for enthalpy change with bond dissociation energy and formation enthalpy

texts:
I learnt that given a reaction: $$\ce{A -> B}$$ the enthalpy change is given by:

$$\Delta H = \left( \begin{array}{c} \text{total enthalpy of}\\ \text{bonds broken}\end{array}\right)-\left( \begin{array}{c} \text{total enthalpy of}\\ \text{bonds made}\end{array}\right)$$

By convention, we keep the minus sign in the equation, and keep all bond enthalpies positive, regardless of whether bonds are made or broken. In this case, the bonds in the reactants are broken, and the bonds in the products are formed. I was also given the equation,

$$\Delta H = \sum \Delta H_\mathrm{F} \left( \text{products}\right)-\Delta H_\mathrm{F} \left( \text{reactants}\right)$$

Are both $\Delta H$'s given by the above formulas equivalent?


texts: How does chelation control result in rate acceleration?

texts:
In the chapter on diastereoselectivity in Clayden, Warren & Greeves (2012), the Cram-Chelate model is discussed. Most significantly, under chelation control, the diastereoselectivity of the addition to the carbonyl group is reversed. Additionally, chelation control achieves high levels of diastereoslectivity, often greater than $\ce {95:5}$. Lastly, it also mentions that chelation control leads to rate acceleration. The above are discussed on p. 864.

It is not surprising that Felkin-Ahn control leads to rate acceleration, especially when both the steric and orbital factors are both satisfied. More details of the model are explained in this post. However, chelation control does not seem to provide any cause for rate acceleration. In fact, as chelation control goes against the steric and orbital considerations, we may even expect it to slow down the addition reaction, rather than speeding it up.

Reference

Clayden, J., Greeves, N., & Warren, S. (2012). Organic Chemistry (2nd ed.). New York : Oxford University Press Inc.


texts: How to calculate the electrical potential and mols of electrons transferred from combined half cell equations?

texts:
Given 2 half-cell rxn's and their potentials, balance the full cell and solve for ECell:

$$\ce{Fe^{3+} + e^{-} ->Fe^{2+}}; E=0.68V$$

$$\ce{Cr_2O_7^{2-}+14H^+ +6e^- -> 2Cr^{3-} + 7H_2O};E=1.33V$$

So I know that both these half-cells are Gaining electrons (Reduction), and in order to solve for the full cell I need to flip one. I flip Fe Cell to oxidation b/c it has a lower potential and adjust for number of electrons moving. To Calculate ECell: $E(Cr)-E(Fe)$ despite adjustment of mols.

So my full Cell is
$$\ce{6Fe^{2+}-> 6Fe^{3+} + 6e^{-}}$$
$$+$$
$$\ce{Cr_2O_7^{2-} +14H^+ +6e^- -> 2Cr^{3-} +7H_2O}$$

My question is, why is the formula to solve ECell:  $E(Cr)-E(Fe)$ and NOT $E(Cr)-6*E(Fe)$?

I'm pretty sure that more electrons generally = more electricity, so why is it when I multiply the amount of electrons, I don't multiply my half cell E?


texts: Why is the reaction of calcium oxide with sulfur dioxide to form calcium sulfite not a combination redox reaction?

texts:
I understand that a combination reaction is one where two substances combine to form a third substance, like with
$$\ce{2Na + Cl2 -> 2NaCl}.$$
I do not understand why $$\ce{CaO + SO2 -> CaSO3}$$ is not a combination redox reaction. After all, it is creating a third substance, so why is it not a combination redox reaction?


texts: Does the number of bonding MOs always equal the number of antibonding MOs

texts:
In (I think all) of the molecular orbital (MO) diagrams I have seen, I have observed that the number of antibonding molecular orbitals is the same as the number of bonding molecular orbitals.

Here are some for example:

I know that the number of atomic orbitals equals the number of molecular orbitals, but I have not heard of an explicit rule stating that the number of bonding molecular orbitals is equal to the number of antibonding molecular orbitals. Is this always true? If not, can someone please give a counter example?


texts: What accounts for the high spin state of the complex Tris(acetylacetonato)iron(III)?

texts:
I understand that there's 5 d-electrons for $\ce{Fe^3+}$ ion, but why it doesn't fill up the lower energy orbitals first to form one unpaired electron, but rather, filling up all the orbitals to form 5 unpaired electrons?

I am unsure how the ligands in this complex affects the crystal field splitting. Do we consider [acac] to be a weak field ligand?
Could it be the geometry of this complex that give rise to high spin state?


texts: Is it possible to create weaker version of guncotton by replacing cotton wool with wood chips or linen cloth?

texts:
If the cotton wool was replaced by wood chips or linen (flax) cloth, would the mixture of nitric and sulfuric acids still react with the cellulose in it to produce nitrocellulose?

If it would, would it be reasonable to assume that the power of such explosive would be (very approximately) proportional to the content of cellulose in your substitute for cotton wool?

Would such explosive produce smoke (as besides nitrocellulose it would contain other flammable substances and no oxygen source)?

Would hemicellulose go through a similar reaction with the acid mixture as cellulose?


texts: How does the solubility of hydrated ions differ from unhydrated ions?

texts: So the hydrated compound I am thinking about specifically is pentahydrate copper sulphate. I know when you put ionic compounds in water, the ions because hydrated by the water molecules. However, what happens when you are already putting a hydrated ion into the water? I think the solubility is supposed to be lower, but I am not exactly sure why. Thanks for any help :)


texts:
I am not sure whether this question is even reasonable, but here it goes. We are taught about the different types of basis sets (extended, minimal, double-zeta, plane wave), but I do not think it is clear as to why they are needed. After all, it is possible to do computational chemistry without a basis set (see James R. Chelikowsky, N. Troullier, and Y. Saad, Phys. Rev. Lett. 1994, 72, 1240).

From what I understand basis sets are needed because we use LCAO. We find a set of functions (a basis set) that resembles atomic orbitals. Is this true? Or is the picture more complicated?


texts: Is the effectiveness of chemical catalysts affected by temperature the same way enzymes are?

texts:
Enzymes do not need high temperatures to function while metal catalysts tend to need a bit of an energy kick to get going.

Enzymes will denature, or break, if heated up too far beyond their optimum temperature (for most around 40 degrees, although some bacterial enzymes can work at 100 degrees).

Do chemical catalysts also have an ideal operating temperature?
I am not asking if the rate of the reaction itself speeds up when a chemical catalyst is used. Rather, if the chemical catalyst becomes more effective at certain temperatures.


texts: Why does sugar make dough turn to liquid

texts:
While making dango with a friend we decided to try to make the dough a bit sweeter.  We already had a large firm lump of dough (rice flour, glutinous rice flour and water) so we sprinkled a bit of sugar on top.  While kneading the dough in my hand I started to feel it run through my fingers.  The entire lump had turned into a goopy drippy mess.

Our best guess was that the sugar soaked up all the water, turning it into a bunch of flour particles in free flowing sugar water, but I cannot find any sources on the internet to explain what exactly happened.  Can anyone explain the reaction that causes this?


texts:
So I have a nail repair kit, consisting of nail glue(ethyl cyanoacrylate), powder and a nail buffer. I'm almost of out glue yet stick have a bunch of powder. One of the crazy glue tiny bottles has almost the same name(ethyl 2-cyanoacrylate). Can I refill the nail glue with the crazy glue?

Short version -
Nail glue - ethyl cyanoacrylate VS ethyl 2-cyanoacrylate - super glue
Are these the same?


texts: Can nitrogen dioxide react with plastics of any kind?

texts: I have searched a lot on the internet but couldn't find any helpful thing. My question is that can nitrogen dioxide react with plastics of any kind?


texts: How are non-carbon stereogenic centers named (S/R)?

texts:
The R/S naming system for stereocenters relies on the Cahn–Ingold–Prelog priority rules to rank the four substituents of a stereocenter; the R or S name is then attributed depending on the spatial orientation of the ranked substituents. While this is mostly used for asymmetric carbon atoms, it holds true of other stereocenters with four substituents.

However, nitrogen and phosphorus atoms can also act as stereocenters if the inversion of their configuration is blocked (e.g. because they're in a cyclic molecule) or slowed enough (e.g. because of bulky substituents). Apparently, these stereocenters are also labelled in R/S fashion. Examples I found include Tröger's base:

(above is the (5S,11S)-enantiomer, below is the (5R,11R)-enantiomer),
and DIPAMP:

Having said that, I can't find any reference as to how the R/S naming scheme is applied to these tetrahedral stereocenters which don't have four substituents, but a lone electron pair and three substituents instead. I assume that the same scheme can be followed if one considers the lone pair as the lowest-ranked substituent, but I can't find any canonical reference as to that.

So, how are such stereocenters named? What authoritative reference can I find on this topic?


texts:
I was actually inspired to ask this question in certain circumstances. In the outskirts of my city, there happened to be a styrene gas leak early morning today which killed thirteen and hospitalized many people.

Since styrene is an aromatic compound, it is suspected to be carcinogenic in nature but I think it is inert towards other atmospheric gases as well as many compounds in non-laboratory conditions. The temperature here is 31 °C, so it can stay for a large time unaffected at the same area without much spreading. I think so because it has a high molecular weight(104 g/mol).

My question is: "is there a way to treat this styrene in the atmosphere without causing much more toxicity in that area?" (For information regarding its toxicity, refer to this safety data sheet). Of course, I understand that styrene is broken down within 1-2 days in the atmosphere naturally but is there any other way to do it quicker?


texts: Single Point Energy in Gaussian software

texts:
I used Gaussian software to determine the single point energy (SPE) of 3 molecules namely ethane, ethene and phenol.

The SPE for the molecules are -79.83, -78.59 and for phenol it is quite large at -307. However, I am not able to explain the trend.

I am thinking does SPE have anything to do with the molecular weight of the molecule for example, larger mass = more negative SPE?? I cant think of a better explanation. Can someone please help me out?

thank you


texts: Is diamond an allotrope or polymorph of carbon? When is something considered an allotrope vs a polymorph?


texts: What is the meaning of the '2' on some Compressed Gas Hazard signs in the lab?

texts:
The main chemistry prep room at my institution (and also at the ambulance station) is labelled with the standard green compressed gas sign.  However, there is a small '2' included within the diamond.  None of the chemistry technicians, tutors or ambulance staff seem to know what it is referring to and I can't find any reference of it on the internet.  Would anyone here happen to know?

The related products of this online provider show that other hazards have different numbers but some also have two (e.g. flammable).  Is there a standard that is being referred to here?


texts:
Why is the chemical shift for hydrides in TM complexes so strongly shielded, to the point where it's negative?

Initially, I thought it was because hydrides are $\ce{H-}$, but isn't the charge meaningless once it coordinates to a metal centre?


texts:
Would these be valid conformations of butane? I tried matching these up with the group but my drawings all seem rotated versus the book.
I'm fairly sure my anti conformer is correct, along with my gauche conformer. I'm not too sure about the two eclipsed conformers; from what I understand, there are two eclipsed conformations - one with strong torsional strain resulting from the methyl group interacting with the other methyl group, and the other resulting from the methyl groups interacting with the hydrogens, right?
Also, can we consider the dihedral angle to be the angle between the methyl groups?

Another problem is that what I've drawn doesn't seem to match with the book's energy diagram too. I'd expect the anti-conformer to be the lowest in energy, but I'd also expect a difference in E for the two eclipsed conformations. One should have more torsional strain from placing the two methyl groups next to each other and the other, less, because the methyl groups are eclipsing the comparatively small hydrogen.


texts: Pulsed NMR change in magnetisation vector

texts:
When a second, radio frequency magnetic field $\ce{B1}$ is applied perpendicularly to $\ce{B0}$, why does the magnetisation vector M rotate in a direction perpendicular to both $\ce{B1}$ and $\ce{B0}$?

I understand how electric charges move in magnetic fields, and I understand the classical electromagnetism magnetic moment, but I can't figure out how $\ce{B1}$ move M in this direction.

Any help would be appreciated.

Image from http://chemistry.mit.edu/sites/default/files/DCIF-IntroNMRpart1-theory-o07.pdf


texts: when using glass to glass stoppers, is it best to have them dry or use lubricant?

texts:
I have some glass flasks that have glass stoppers. It’s basically the typical glass stopper with the frosted tip which fits into a glass opening. Basically think of a typical glass volumetric flask. i attached a pic of my flasks with the stopper. they are not threaded connections. i believe they slight self lock. like i put the stopper in and push down and turn to get it tight.
So my question is, if I am travelling/moving theses flasks around in a situation where they may tip over or be upside down for some time with fluid inside them , is it better to have the glass to glass contact between the glass stopper and the glass opening fully dry? Or is it better to add some oil to the glass stopper?
If I do glass to glass and they both are dry, it’s usually pretty sealed however I believe I have always been told to use some type of oil as it helps it seal better but I tbink I am against using oil becusse I feel like the stopper has a higher chance of coming off or slightly moving causing a leak becusse of the slipperiness of the oil.
*the connection is not threaded, it is just flat like a typical glass volumetric flask”
I of course will be using parafilm/tape on top so I am just wondering which method is best so no liquid leaks out. There will be no gas build up, its just liquid like water or alcohol sometimes but i dont care if they slightly evaporate. i just dont want leaks
Basically I am looking for the best method to reduce leaks
Thanks


texts: intuitive explanation of Wegscheider condition and its violation

texts: The Wegscheider condition restricts the values that rate constants in a set of chemical reactions can take on. can someone please explain intuitively why the condition has to be true, and give a simple example of a set of reactions and rate constants that violate it? why could such a system not exist physically?


texts: Why is the reaction between potassium permanganate and hydrogen peroxide spontaneous?

texts:
When hydrogen peroxide is mixed with potassium permanganate, oxygen gas and water vapour are formed, according to the reaction (source):

$$\ce{2MnO4- + 3H2O2 -> 2MnO2 + 2H2O + 3O2 + 2OH-}$$

This reaction is spontaneous, and exothermic. It is an example of a redox reaction, with the following half reactions occurring (data from Vanýsek):

$$
\begin{align}
\ce{MnO4- + 2 H2O + 3 e- &-> MnO2 + 4 OH-} &\quad E^\circ_\mathrm{red} &= 0.595~\mathrm{V} \\
\ce{H2O2 &-> O2 + 2 H+ + 2 e-} &\quad E^\circ_\mathrm{ox} &= -0.695~\mathrm{V}
\end{align}
$$

$E^\circ_\mathrm{cell}$ is equal to the sum of the oxidation potential and the reduction potential of the two half reactions; in this case, it would be $-0.1~\mathrm{V}$. A redox reaction is spontaneous if $E^\circ_\mathrm{cell}$ is positive — how can it be, then, that hydrogen peroxide spontaneously reacts with permanganate ions?

Using thermodynamical data (from NIST), I have calculated that the $\Delta G^\circ_\mathrm{m}$ of the reaction is $-463.576~\mathrm{kJ}$. The reaction should indeed be spontaneous. How can it be, then, that the results of the thermodynamical approach and the electrochemical one differ drastically?


texts:
Recently in my chemistry classes, the teacher spoke about SPDF configuration and then said that we'll be taught about it in higher classes.

But I'm sorta curious to know that what is SPDF configuration and is there something like - obtaining electronic configuration in SPDF format?


texts: in which way calcium promotes cell division

texts: I have read in bio chemistry that calcium plays an important role in the cell division but the in depth information is'nt available in the textbook and I cannot memorize any fact without a supporting fact I just want to know what is its role in the process of cell division


texts: Is the E in Arrhenius equation the change of enthalpy?

texts: I'd like to know whether the activation energy in Arrhenius equation is the enthalpy difference between the transition state and the reactant. If it's not enthalpy, is it Gibbs energy or something else?


texts: Reason for the stronger acidic property of phenol than alcohol

texts:
In phenol, pulling the $\mathrm{p}_z$ electrons from the oxygen atom into the ring causes the hydrogen atom to be more partially positive than it is in aliphatic alcohols. This means it is much more easily lost from phenol than it is from aliphatic alcohols, so phenol has a stronger acidic property than ethanol.

Could someone please explain the link between the $\mathrm{p}_z$ electrons of oxygen overlapping with the cloud of delocalised electrons of the phenol ring and the increase in positivity of the bonded hydrogen … which in turns allows phenol to lose a proton more easily?


texts: Can green vehicle antifreeze (Ethylene Glycol) be diluted in a glass container?

texts:
I picked up a container of undiluted green antifreeze, and oops, I don't have anything to mix it in! I do have a glass container though at the top of my recycling bin that is about a half gallon. I've heard some plastic containers (soda bottles, plastic milk jugs) can't be used for anti-freeze, but what about glass? Two questions arise from this

As Long as I rinse the previous contents (milk) out, can I safely use this glass container for diluting antifreeze and putting it into my vehicle?
Once I'm done can this go back into the recycle bin, or will trace amounts of antifreeze spoil it for recycling?


texts: Which of the following is an appropriate set of reactants for the preparation of 1-methoxy-4-nitrobenzene and why?

texts:
Is it (a) para-bromonitrobenzene and sodium methoxide or (b) sodium para-nitrophenoxide and bromomethane?

Or are they both appropriate? (And is one more appropriate than the other?)

One book (NCERT Chemistry Class 12 [India]) and at least one source Free NCERT solution of this question mention the latter as the appropriate. [However, I doubt the credibility of this source, as most likely, it is made to show how the NCERT book is correct (for CBSE Boards' exam) which, though is credible, is still a human-made book, which may have mistakes/errors.] NCERT only gives the answer as (b) without explanation. Another book (abc of Chemistry [India]) mentions "chemically, both are equally probable" as -nitro group activates the bromine site on benzene for substitution. And IMO, this book is more credible.

Any expert opinion?


texts: Preparing a 0.030 M solution of potassium ferrocyanide trihydrate?

texts: I am a little bit confused on what I am supposed to do. The instructions say to prepare 250 mL of this solution by measuring out in grams the amount of PFT using a 250 mL volumetric flask. Then it says I have to add dI water until te meniscus hits the full mark on the flask, then it says to calculate the actual molarity of the solution. Am I supposed to multiply the molarity by the liters given to me to find the grams of PFT I am supposed to use? How would you go about this?


texts: Can our chemical elements be differents on other universes?

texts:
Let's pretend that in other universe we have an element with atomic number 6, like our carbon, but in this other universe the element is completely different from our carbon, like a new element with other properties.

Is this a possible scenario?


texts: What color would be produced by the burning of the listed chemicals of the projectile weapon the carcass?

texts:
The carcass was a projectile weapon developed by the French in the second half of the 17th Century. It was "named carcass because the circles which pass from one ring, or plate, to the other, were thought to resemble the ribs of a human carcass."

illustration from the article "The British Fire Bombing of Quebec City in 1759"
The internal chemical constituents are described as
"10 parts of pounded gunpowder, 2 of nitre (potassium nitrate, KNO₃), 1 of sulfur, and 1 of colophony (rosin)"
OR
"6 of gunpowder, 4 of nitre, 4 of sulfur, 1 of beaten glass, 0.5 of antimony 0.5 of camphor, 1 of sal armoniac, and 0.25 of common salt"
and the exterior was covered in
"4 parts of melted pitch, 20 of rosin, 1 of oil of turpentine, and as much ground gunpowder as was needed to reduce it to the consistency of a paste. After immersion, the shell was to be covered with tow, and immersed again"
Is there any way to determine or estimate what color the exterior would burn during flight, or what would be the color when the interior ignited? What color would be the smoke either during the flight or during the burning of the interior?


texts:
It is known that the specific heat of a gas is process dependent. So it must be theoretically possible to have a negative value for a gas according to the following equation (for polytropic process, $PV^n = \mathrm{const}$):

$$C = \frac R{γ - 1} + \frac R{1 - n}$$

where $C$ is molar specific heat and $γ$ is adiabatic exponent.

Supposing $γ$ is $\frac{5}{3}$ and $n$ is $\frac{4}{3}$, $C$ comes out to be negative. Is it practically possible and if so what would it signify? As you provide more heat to a gas in such a process, would it lose temperature?
Please clarify.


texts: How to know if a reaction forms H3O+ ions or OH- ions?

texts: How would you know when an acid or base is paired with $\ce{H2O}$ that it will form an $\ce{OH-}$ ion or a $\ce{H3O+}$ ion? I just started the acid and base equilibrium unit, and I'm just confused on what conditions $\ce{OH-}$ or $\ce{H3O+}$ ions form.


texts: Why Na/C2H5OH not preferred in the reduction of carboxylic acid, despite being used for the reduction of esters

texts: why is Na/C2H5OH  not preferred in the reduction of carboxylic acid to alcohols, despite being used for esters?


texts: Why is the gradient of the curve of a strong base titrated with strong acid small up until equivalence?

texts:
I understand the cause of the sharp decrease in pH upon reaching the equivalence point, but I don't understand why addition of relatively large amounts of the strong acid would be accompanied with small changes in pH before that.
When looking at how pH changes when adding a strong acid to water there is a very fast drop in pH, as to be expected due to the logarithmic nature of the pH scale. The pH scale (I believe) also explains the flat region at the start of the curve for titrating a strong acid with a strong base.

But I don't understand it for the titration in question. I presume it must be something to do with the neutralisation but I'm not sure.


texts:
There has been a lot of news about Graphene since its discovery in 2004. And as we are all told it is a revolutionary material which is very strong, conductive and transparent; even in some cases it has revolutionized especial laws of physics (see this page).

But what is it about the structure of Graphene which makes it so strong?


texts: I was wondering if anyone has some experience regarding my question. The geochemical simulation of mixing a mole of pyrite with a kilogram of acidic solution (pH=1) shows that Pyrite almost remains intact (PHREEQC). Do lab observations confirm this?


texts: Where can I access raw values for near infra red absorbance of liquid water?

texts:
I have encountered several sites where water's near-infra-red absorption spectra has been plotted as a figure (for e.g, here). Is there a site where I can access these raw absorbance/transmittance values? Eyeballing is prone to errors and inaccuracies.

What I have found: NIST has a nice plot of the IR absorption spectra of liquid water, and I can potentially access the raw data by looking at the plotting functions, but as you can see it has no near-IR data.


texts: Which process would separate the mixture of toluene, cyclohexane and water?

texts:
toluene: $\ce{C6H5-CH3}$
cyclohexane: $\ce{C6H12}$

I think that answer would be:

Toluene and cyclohexane do not dissolve in water (since they are nonpolar), so I would first separate the water from the mixture with a separator funnel.

A mixture of cyclohexane and toluene would be separated by fractional distillation. Cyclohexane, which has a lower boiling point than toluene, would be eliminated from the mixture.

Is there anything wrong in my answer? Would there also be anything to add?


texts: Solubility Product, and it's relation to solubility

texts:
In order to remove temporary hardness of water, it is boiled.
On boiling, while Ca(HCO3)2 gives CaCo3(ppt.) , Mg(HCO3)2 gives Mg(OH)2(ppt.).
According to my book precipitation of Mg(OH)2 occurs due to it's high solubility product.
But doesn't a higher solubility product mean a higher solubility? (Since solubility product is the product of solubilities of each component)


texts: Tap water leaving white residue after drying

texts:
There is no heating or cooling in this process.

We recently move to a new house and something strange is happening with the water in every tap of the house.

First thing I noticed is when you fill a bucket with the garden hose the bubbles in the water lingered around longer than they should have, ie. normal senario fill bucket with water and bubbles pop immediately, this senario the bubbles take a few good long seconds befor they pop.

Second thing I noticed was after waking away from the garden hose and returning after everything was dry there was white residue all over anything that the water had been on, so I wipe it down and did it again and same thing happened, so I went and tested all the taps in the house with the cold water and the same thing happened for all the taps, so all the taps are using the same water source.

I have heard of white residue being left behind after heating from a source like a kettle but never heard of white residue being left behind from a non heated source.

Is there any way I can find out what this is and should I be worried about this (more than I already am)?
Or alternatively does anyone here know what this is?


texts: Does my data show quadratic regression in a calibration curve?

texts:
This data was taken for my science fair project, and I would like to know the relationship between spectrophotometer absorbance and cell density (taken manually) of algae after a toxicity test. The different levels of toxicity are IC 0 (no chemical), IC 25, IC 50, IC 100 (the most chemical). The IC value is basically the estimated about of the chemical needed to destroy a certain amount of the population. I took the manual density and absorbancy of four samples of different levels of toxicity.

IC value/Cell densities(cells/ml)/absorbancy:

IC 100/28000/0.408

IC 50/42600/0.302

IC 25/70000/0.01

IC 0/138000/0.79

Based off of these points, I would like to make a calibration curve. But when I do this, the highest r^2 is quadratic. Is this an acceptable calibration curve for finding other densities based off of known absorbances? Or would it have to be linear with a very low r^2?


texts: $\ce{CaF2}$ is insoluble in water, but $\ce{CaCl2}$, $\ce{CaBr2}$, $\ce{CaI2}$ are soluble. Why is this so?


texts: Inferring bond breakage in a reaction from InChI strings of reactans?

texts:
I'm currently confronting a problem:

I would need to enumerate all chemical bond breakages that occur during a given chemical reaction, including the type of bond and the atoms participating in the bond. This is straightforward to do by visual inspection if one has, say, the 2-D structures of the reactants and products of a given reaction.

My problem is that I have a list of several thousand reactions, and I need a computer to do the job for me. To this end, I got the InChI (and SMILES) representations of all molecules participating in each reaction. At first, I thought that it would be rather easy to write a program that identifies and enumerates the broken bonds in the reactants (given the InChI strings), but by now I'm starting to become desperate.

Perhaps someone knows any software able to do this?


texts: Can heat capacity at constant volume for a gas decrease as temperature increases?

texts: I found a function for the $C_V$ of a gas which is being heated under constant volume,but the function shows that the $C_V$ is decreasing. I was wondering if this is possible for any gas since I know the $C_V$ is supposed to increase with temperature. Is there any reason why this would happen?


texts: Can there be an aqueous solution with a convex meniscus?

texts:
This question is motivated by a quote from a TV show:
A detective is looking at a small vial (really a glass tube) that supposedly contains poison. Then the detective says:

You don't have to take AP Chem to know that, in a glass container, the meniscus of a liquid containing poison, like baneberry, curves downward, but this meniscus curves upward because it's just water, right?

The detective proceeds to drink the content of the vial to convince everyone that it contains water and not poison.
The "vial" in question really was a tube.
Surely the "poison" itself was an aqueous solution. So the detective is implying that there exist some aqueous solutions with a convex meniscus. I've searched the internet looking for examples of convex menisci, and the only example I could find was mercury. Mercury in thermometers is such a well-known example of convex meniscus that every written material I could find used it as the example of convex meniscus.
Hence the question:
Does there exist an aqueous solution with a convex meniscus?


texts: In QSAR, what is the simplest (but most powerful) way to create an applicability domain model?

texts:
QSAR means Quantitative Structure Activity Relationship.

An applicability domain model is a model that tells you how far you are from the domain where your model was trained. I.e. it is a kind of map where you can place molecules. And on this map, there is some delimited territory that you have explored while you were training your model.

Let's say I have created a QSAR model on some training dataset, and validated it on a test set.

Next, I'd like to create a model that gives me a 1.0 (or nearby) if the molecule I present to the QSAR model looks similar to the training set, but a 0.0 (or nearby) if it looks dissimilar.

Currently, I was thinking about training a one class Support Vector Machine on the training set.

Broad picture: I'd like to get a warning in case the QSAR model is presented with something that looks too far from anything it was trained on. The warning would mean: "be careful with this prediction".


texts:
My book gives the IUPAC name of $\ce{KAl(SO4)2.12H2O}$ which is nothing but emperical formula of potash alum as

"Potassium aluminium (III) sulphate -12 water"

But Wikipedia gives it as "Aluminium potassium sulfate dodecahydrate" , though there could be change in name because of number of water molecules but there is significant difference between the two names

So, my question is how to give IUPAC name to a double salt (potash alum is a double salt), and why is there difference between two iupac names I.e the one which is given in my book and the one in wikipidea.


texts: Converting a CIF file to a .com or .gjf file

texts:
I would like to perform DFT calculations and extract atom coordinates for calculations in Gaussian.
I am using Mercury and have been able to isolate the atoms that I am interested in simulating. However, when I save the CIF files and open them again i see something very strange.
Atoms that have fractional occupancy from the XRD are shown to be fully occupied, this gives me nonphysical molecules that contain to many atoms. How can I get rid of these fractional occupied atom positions?
I am attaching an image to illustrate what I mean.

When i retrieve the data from CCDC's webpage, the fractional occupied positions are marked with crosses, is there a way to clean the file?:


texts: How do you solve a net ionic equation without a balanced equation?

texts:
In class, my professor went over a method for finding the net ionic equation without determining the balanced equation (e.g., if finding the balanced equation was too difficult for us students). It involved writing the ions of each of the solutions being mixed and determining which ions would be spectator ions.

For example, finding the net ionic equation for the following mixture of solutions:

$\ce{NaC_2H_3O_3 + BaCl_2 +NH_4NO_3 + K_2CrO_4}$

Unfortunately, I don't quite grasp the process. How does one determine which ions and compounds will remain in the net ionic equation?


texts: Unit derivation concerning Nernst equation

texts:
We know that Nernst equation is given by:

$E=E^{\circ}+\frac{RT}{nF} \ln[\ce{M^{n+}}]$.

Now, A question asks me to derive the unit of  $\frac{RT}{nF}$.

Which I think can easily be derived this way:

$\frac{RT}{nF}=\frac{E-E^{\circ}}{\ln[\ce{M^{n+}}]}$,

Now, the unit of $E-E^{\circ}$ is volts (since it is emf), and $\ln[\ce{M^{n+}}]$ is just a constant numerical value.

Hence, I think the unit of $\frac{RT}{nF}$ is Volts.

This was my approach. Can anyone tell me if it is a correct approach?


texts: Investigating the effect of solvents (protic vs aprotic) on the alkaline hydrolysis of ethyl acetate using a conductivity meter

texts:
What different areas about solvents can be explored with the conductivities collected of the alkaline hydrolysis of ethyl acetate in propanone and ethanol?
$$\ce{CH3COOC2H5 + NaOH -> CH3COONa + C2H5OH}$$

Currently, I am looking at the effect on activation energy, rates, and rate constants and the overall conversion of ethyl acetate to sodium acetate at the end of the ten minutes of the reaction in the two solvents (to see which is more favorable).

Will I be able to integrate transition state theory and Gibbs equations in any way possible?


texts: What is the priority of a phenyl group in a compound such as this?

texts:
I assumed this:
http://www.chemspider.com/Chemical-Structure.12491.html?rid=222625d4-811c-4b07-b263-8930fafa831a

to be 1-phenylbut-4-ene
Where is the priority here? No source I know of tells me of where the priority of the phenyl  group lies.

It is wrong. The book states it is 4-PhenylBut-1ene.

What is the priority of the phenyl group?


texts: Advanced Quantum Chemistry Reference for Reactivity Phenomena

texts:
I'm currently in organic synthesis seeking to develop quantitative "physical" (that of a physicist), rather than "chemical", intuition for areas where traditional VSEPR/ MO models cannot fully describe the reactivity of atoms. Even if these problems are ultimately computational, I'm looking for a first-principles basis of reactivity to aid my intuition.

Searching for answers has led me to questions like:

How exactly do orbitals hybridize? E.g., if I put OH- and H+ in a room together, will applying TDSE to both their independent wave functions eventually give me the desired linear combination of wave functions?

At short distances between two reactive partners, through what quantum mechanism do atoms' electrons influence their reactive partner's electronic structure. That is to say, undergraduate QM does not really discuss how wavefunctions exert EM forces and how EM forces in turn influence other wavefunctions.

And so on.

Using the search function, I've found several suggestions for quantum chemistry texts that discuss electronic structure, but have yet to find one that satisfactorily provides a step-by-step walkthrough of the various quantum phenomena involved in the kinetics of reactivity. I suspect these questions dabble into QFT areas, which I'm comfortable with.

Such a text, ideally, would discuss the mathematical origin of anti-bonding orbitals and other phenomena undergrad QM/ QChem courses do not generally cover.

Thanks!


texts: How long will it takes two miscible liquids to fully mix (homogenize) through diffusion?

texts:
This question occurred to me while I was pouring milk into my coffee and was too lazy to stir.
Assume you have some volume $V_a$ of liquid A directly on top of another volume $V_b$ of liquid B. The two liquids are fully miscible. With no stirring, how long until the solution becomes fully homogenous solely by diffusion?


texts:
I was wondering how to answer  a question I got from my students about the possible recovery of gold from solution. We just finished the reaction between silver ions and copper metal and they wondered why copper wouldn't displace gold from solution in an electrochemical reaction. The redox potentials suggest that it can be done but there is no documentation of this reaction anywhere. I can't try the reaction because we have no gold compounds. If it could be done you would think that gold recovery but companies would use the technique since copper is a lot cheaper.
Please advise.


texts: Alkyl shift vs Hydride shift in hydroboration-oxidation reaction

texts:
A part of the hydroboration oxidation reaction in alkenes is as follows:

but in the 4th step, why is alkyl shift happening instead of hydride shift (from Boron atom)?


texts:
I am told that all anomers are diastereomers. I think this is BS. If there is a carbohydrate with only one chiral center, then changing the configuration of the anomeric carbon gives us enantiomers.

Or is it impossible to have carbohydrates with only one chiral center?


texts:
How do color pigments colour the plastics? Is there any chemical reaction, molecular association, or physical reaction?
What kind of bonding mechanism is there between pigment molecules and plastics?

How could Polypropylen and liquid organic pigments or granular organic pigments join each other? Pigments dont have oil or any solvent.

What would happen in molecular level?


texts: Why is ATP an inhibitor? I mean, if there are high levels of ATP, it means that the cell has adequate amounts of energy. Therefore, if it doesn't need the energy, then glucose needs not go through glycolysis to produce that energy and is more practical to be stored as glycogen. So why is ATP an inhibitor of glycogen synthase?


texts: Balancing a chemical equation, but with an incorrect mole ratio

texts: I'm wondering if it's possible to balance a chemical equation with an incorrect mole ratio.  I have the unbalanced equation $\ce{AgNO3 + Cu -> Ag + Cu(NO3)2}$, I have a $2:3$ ratio of $\ce{Cu}$ and $\ce{Ag}$ that I must plug in.  Is this possible, because it doesn't look like it.


texts: Is it possible to electroplate from a gallium anode?

texts:
I have been looking at some papers on electro-deposition of iron gallium alloys and these all use solutions made up of Fe and Ga sulphates.

I am just curious as to why perhaps an anode made of one of the materials might not have been used as part of the process? I mention gallium specifically because the cost of the Ga sulphates is quite high, while the Ga metal is relatively cheap.

My impression is that it is typically difficult to electro-deposit gallium, but I think this was in specific reference to plating from solutions of the Ga salts, I have not yet come across plating from a Ga anode, and I'm curious about this.


texts: Reaction of Iron(III) with hydroxide ion

texts:
The observations:

1) Treatment of 1 mL of 0.05 M $\ce{Fe(NH4)SO4}$ solution with excess 1 M $\ce{NaOH}$ results in the formation of a rust-colored red-brown iron-based solution with many suspended particles in the solution. These particles match the description of $\ce{Fe(OH2)3(OH)3}$. This is the vial on the right in the picture.

2) Treatment of 1 mL of 0.05 M $\ce{Fe(NH4)SO4}$ solution with excess 6 M $\ce{NaOH}$ results in the formation of a clear but colored solution with no suspended particles in the solution or any sort of precipitate. The yellow-brown colored solution matches the description $\ce{Fe(OH2)4(OH)2+}$. This is the vial on the left.

Why is it that treatment with more concentrated base results only two apparent deprotonations rather than three?

More observations (after about 10 minutes):

1) The 1 mL of 0.05 M $\ce{Fe(NH4)SO4}$ solution treated with excess 6 M $\ce{NaOH}$ has developed suspended particles. This is the vial on the left.

2) The 1 mL of 0.05 M $\ce{Fe(NH4)SO4}$ solution treated with excess 1 M $\ce{NaOH}$ has started to become clear (the suspended particles are disappearing). It seems like much of the particles have settled on the bottom. This is the vial on the right.

It seems that the 6 M $\ce{NaOH}$ is eventually "getting the job done" by going through with the third deprotonation of $\ce{Fe(OH2)6^{3+}}$. I don't think that the 1 M $\ce{NaOH}$ is deprotonating $\ce{Fe(OH2)3(OH)3}$.

Still, why is it that treatment of iron(III) ions with concentrated base does not result in the formation of $\ce{Fe(OH2)3(OH)3}$ immediately but treatment with less concentrated base does?

Even more observations:

1) Treatment of 10 mL of 0.05 M $\ce{Fe(NH4)SO4}$ with excess 6 M NaOH results in immediate and obvious $\ce{Fe(OH2)3(OH)3}$ formation. This seems to support the nucleation explanation; the higher solution volume means lower concentration and lower supersaturation and therefore fewer and larger crystals of $\ce{Fe(OH2)3(OH)3}$ being formed.

Possible explanations I came up with:

1) I ran the results past a grad student and he said his best guess is that the excess $\ce{HO-}$ present stabilizes $\ce{Fe(OH2)4(OH)2+}$. He suggested a conductivity test to make sure that there are $\ce{Fe(OH2)4(OH)2+}$ ions in the clear solution. However, I did not have a conductivity meter handy.

2) A problem in the lab manual from an unrelated section notes that strongly electrolytic solutions, such as saturated $\ce{H4NCl}$ solution, can cause dispersion rather than dissolution of $\ce{Al(OH2)3(OH)3}$ in solution. A 6 M $\ce{NaOH}$ solution is strongly electrolytic, and as a result, the ions may be keeping the $\ce{Fe(OH2)3(OH)3}$ from clumping together.

What are your thoughts?


texts: Reason Behind Decrease In Potential Energy

texts:
Atoms combine to gain stability. They gain stability when they lose energy. In my book, it's given that the potential energy of the system is reduced during chemical combination. But I am eager to know: how is the potential energy of the system reduced?

I want the theoretical reason.


texts: Can aromatic rings be cyanated using cyanide as a nucleophile?

texts: For example, can I convert chlorobenzene into benzonitrile by using potassium cyanide as the reagent?


texts: Acidic KMnO4 oxidizes H2S to S. Why doesn't the oxidation proceed further to sulfur oxide, sulfur dioxide or sulfur trioxide?

texts: I have some idea about the question. I think it has to do with oxidation/reduction potentials but I am not able to find any resource for the exact values or how to make sense of them in this context. Any reference would be appreciated.


texts: Can a solution of FeCl2 go bad over time?

texts: My lab has been using solution of FeCl2 for an assay that was mixed about three years ago. Recently the assay has failed twice. I was wondering if it is possible that the iron ions in the solutions have changed oxidation over time?


texts: What is the active ingredient in this "stimulant?"

texts:
It is an easily defensible argument that this is a medical question rather than a chemistry one, however, I feel that it leans ever so slightly towards chemistry, and so I posted it here.

There is a "new" OTC stimulant being pushed around that shall remain unnamed so that this isn't flagged as an advertisement or anything.  In looking at the list of ingredients, I don't see anything that would act as a stimulant anywhere in that list.  Having said that, I'm not an expert.

So, I came to the experts.  ;)

Here are the ingredients according to the bottle:

Just to clarify, the heart of this question is "Which ingredient is the stimulant?"


texts: How do I know that an acid and conjugate base are present in equimolar amounts?

texts:
Acetylsalicylic acid is a molecule in several popular drugs such as Magnyl and aspirin. It has a $\mathrm{p}K_\mathrm{a}$ of 3.5.

I'm about to calculate the $\mathrm{pH}$ of a $\pu{0.010 M}$ solution of acetylsalicylic acid.

I've read up on how to do this and in one video the author talks about "equimolar amounts".
He says that now that we have equimolar amounts, we can write: $$\ce{\frac{[H+][A-]}{[HA]}} = \ce{\frac{[H+]^2}{[HA]}}$$

Which makes sense as there are equally many $\ce{H}$ and $\ce{A}$ ions. However when can I assume that an acid disassociated equally? Also, I thought that when it did this then it was called a strong acid? Why would I be using this formula at all for a strong acid?

If I can assume that acetylsalicylic acid disassociates into equal acid and base ions, then I can calculate my problem, but I'm skeptical as to assuming this is true.


texts: Is it possible to form an alloy of gold and zinc?

texts: I know you can dissolve gold in mercury, but i do not have access to any. Would it be possible to dissolve it in molten zinc instead mercury.


texts: Textbook problem with molar mass of carbon dioxide

texts:
$\ce{K2CO3}$ and $\ce{HCl}$ react to produce $\ce{CO2}$. In an empty flask ( m = $\pu{85.431 g}$ ) we put in the produced gas and the mass of the flask is now $\pu{85.510 g}$. After that we fill the flask with water. Volume of the flask filled with water is $\pu{122 ml}$. Pressure is $\pu{101325 Pa}$, temperature of air is $\pu{300 K}$. Density of water is $\pu{0.99893 g cm-3}$, and the molar mass of air is $\pu{28.8 g mol-1}$. Find the molar mass of carbon dioxide.

I have calculated the mass of $\ce{CO2}$, using the mass of the flask filled with gas and subtracting the mass of the empty flask. I have figured out that somehow through $pV = nRT$ I am supposed to get to $n$ and take into consideration that $n$ is not only the number of moles of $\ce{CO2}$ but also of $\ce{H2O}$ and air.
What I don't understand is the volume of water used to fill the flask. In that volume do we only have $\ce{H2O}$ or is that volume of 122 mL also the volume of air + $\ce{CO2}$ + $\ce{H2O}$?
Any hint is appreciated.


texts:
I am doing an experiment with pentacene molecule ($\ce{C22H14}$). I want to clean my sample reservoir after using it.
But I show in some literature that it is slightly soluble in organic solvent. Could you please suggest me a solvent for pentacene ?


texts: How does functionalized activated charcoal work?

texts:
If I understand correctly it is possible to trap stuff inside activated charcoal pores to give it specific retention properties (by exposing it to functionalizing compounds while heated to open up the pores?).
When a solution for instance is passed through activated AC, what happens inside the pores with the functionalizing compound to trap stuff that otherwise wouldn't be trapped? Can it be said that the functionalizing compound precipitates stuff inside the pore by producing low solubility products?


texts: Concept of enthalpy at a given temperature

texts:
In thermodynamics, we always quote a fixed temperature, whenever we mention enthalpy of a reaction. For instance, one can determine the enthalpy of combustion of methane at 25 °C. Now almost all reactions involve a change in temperature, i.e. they are either endothermic or exothermic.

How should we physically interpret the meaning of enthalpy change at a fixed temperature? I recall from one textbook on experimental physical chemistry (perhaps it was Shoemaker's Experiments in Physical Chemistry stating that these state functions; still how can physically interpret enthalpy change at a given arbitrary temperature? I have not seen any textbook explicitly addressing this point.


texts: Acidic and alkaline salt solutions: why do some salt form acid/bases while others don't

texts: I have a question regarding salts and their solutions. How come some salts, like sodium carbonate and ammonium chloride, produce acids/bases when dissolved in water? Moreover, how can you predict whether these solutions will act as an acid or as a base just by looking at the salt?


texts: Crystal structures of heaviest nuclides' compounds

texts: What is the heaviest element of the periodic table for which there is a compound whose crystal structure has been completely resolved by X-ray diffraction?


texts:
According to Keesom, Debye and London effect, the non-covalent reactions should be stronger, the bigger are electric charge differences between two interacting particles. E.g. Ion-induced dipole are stronger than dipole-induced dipole interactions.

So shouldn't be Van der Waals forces stronger than hydrophobic interactions? It is said that if we count with greater amounts of a substance, the hydrophobic interactions can be even stronger than hydrogen bonds. But aren't hydrophobic powers actually composed of the above mentioned effects? If two particles were absolutely neutral, they would not react since only opposite characteristics are attracted towards each other. These weak opposite charges can be caused also in non-polar substances by London effect. But that effect should be weaker than Keesom effect between permanent dipoles which contribute to VDW forces, for example in water.

Is it true that Van der Waals forces are stronger than hydrophobic interactions?


texts: How can hydrogen and oxygen coexist in high temperature? Where did the oxygen come from?

texts: A gasification worked with the combustion of bio pallets with production of syn gases. Pure oxygen and $\ce{H2O}$ were fed into the combustion reactor to combust the pallets with no opening of any syn gas outlets. Once the pallets got ignited enough, then there was no more oxygen input. A kind of gas reformer (catalyst) was equipped in the reformer. The temperature in the reactor reached more than $\pu{1000 ^{\circ}C}$. Then all the syn gases were collected and analyzed. What I found was that the composition of the gases were methane (43%), hydrogen (23%), oxygen (20%), and other gases (carbon dioxide and monoxide). I don’t understand how such a high volume of oxygen coexisted with hydrogen together in that high temperature reactor. Is it possible that those gases stay together without an oxidation reaction occurring? Where did the oxygen come from?


texts:
I need to increase the wetting of an $\ce{H2O2}$ solution on ceramic surfaces. Does anyone know of a common chemical I can use for this?

The properties it would ideally have are:

Increases wetting of $\ce{H2O2}$ - water mixture on ceramics (particularly glazed tiles and tile grout).
Does not react or reacts very slowly with $\ce{H2O2}$ (and water).
Non-toxic / low toxicity. Food safe would be ideal.
Reaction products are non-toxic / low toxicity.
Reaction products are all either soluble in water or evaporate under atmospheric conditions.
Commonly available and reasonably cheap.
Non-foaming or anti-foaming.

Thank you so much to anyone who has a suggestion.


texts: Which of the following compounds would result in the reaction being more active in the reverse direction?

texts:
$\ce{Fe(OH)2 (s) <=> Fe^{2+} + 2OH-}$
The reaction will be more active in the reverse direction if .......... is added
a) $\ce{KOH}$
b) $\ce{Na2S}$
c) $\ce{Fe(OH)2}$
d) $\ce{Fe(NO3)2}$

My thoughts:
Well, adding more $\ce{KOH}$ will increase the $\ce{OH-}$ ions so the reaction will go in the reverse direction to get back to equilibrium. Adding $\ce{Fe(NO3)2}$ Will increase $\ce{Fe^{2+}}$ ions and the reaction will go in the reverse direction too.
However, the book answers states that only (d) $\ce{Fe(NO3)2}$. I searched google but all the examples involved having only choice which works.
Note: Refer me to sites if necessary. I am ready to read.


texts: Which would have higher priority according to CIP rule (Cyclic Substituents)?

texts:
So if we were to assign E-Z nomenclature to this compound :

then the Ethyl group would obviously have more priority than methyl group, but I am confused whether out of Cyclopropane and Cyclobutane which would have higher priority, my teacher said it's cyclopropane which would have higher priority but according to this question , I guess it should have been cyclobutane having higher priority using hierarchical digraphs.
So can anybody confirm whether it has E or Z configuration  ?


texts: Why is the spin quantum number of an electron +1\2 or -1\2 in an atom? Is this an experimental value or theoretical value?


texts:
I figured out that KCl + NaOH may result in KOH but I think this reaction can not happen in an aqueous medium. So there I have a couple of questions.

Is there a way to make the reaction I stated above to happen?
Is there a way to turn KCl into KOH?


texts: Off taste of over-boiled soup, what is the chemistry?

texts:
I had a tin of Asian soup where the label explicitly states "don't boil". It happens, it did boil, and afterwards had a taste that reminded me clearly of the smell I remember from stale soap water, such as from washing clothes without a washing machine.

What is it that caused that? Asking for the substances as well as how they are produced.


texts: What determines how favorable (exothermic) the electron affinity of a certain element is?

texts:
(Favorable means how exothermic a reaction is, more favorable= more exothermic)

There are some abnormalities in the trends of how favorable the electron affinity is.

From Al to Cl, the
Electronegativity is increasing, but the energy releasing from the electron affinity of P is smaller than that of Si. Why? Is it because of how the electrons are arranged?

There are many determinants of how favorable electron affinity is. For example, oxygen and sulfur. Generally, we will think oxygen to have a more favorable electron affinity, due to its stronger electronegativity. Both have the same electrons config, except for the number of shells. But sulfur appears to have a more favorable electron affinity because of its larger size. The smaller size of oxygen atom produces more electron-electron repulsion when one or more electrons are added.

All I ask for is a list of determinants. I tried to find one but couldn't.


texts: What does it mean in a Ni(II)complex if the HNMR spectrum appears unbroadened and unshifted & what does this tell you about the coordination geometry?

texts: I am trying to work out the an unknown Ni(II) complex. I don't known the geometry and I have read that broad lines on the nmr spectrum indicate large compounds with symmetric environments. Does this mean that the complex would have tetrahedral geometry as square planner would be symmetrical and octahedral too large?


texts: Why benzenediazonium bromide and iodide are not important?

texts:
When we think of aryldiazonium compounds, the first compound that comes to mind is benzenediazonium chloride. Sure thing, the compound is versatile and has been used to make a vast array of organic compounds and thus serves its purpose as a useful reagent. But what about other halides like benzendiazonium fluoride, bromide and iodide? Chemists and scientist do not take them noteworthy as there is little to no literature evidence of their synthesis. Are the compounds so unstable that chemists neglect them? Nobody has attempted to make the compounds in the way benzenediazonium chloride is made. Why is it so? Is it because of unfavourable reaction conditions? Can't we use hydrogen bromide or hydrogen iodide to make benzenediazonium bromide/iodide respectively? Like the following reaction:

$$\ce{C6H5NH2 + HNO2 + HX -> C6H5N2+X- + 2H2O  ~~~~~~~~ X = F, Br, I}$$

What are the reasons for the non-existance of/not preparing other benzenediazonium halides? Is it just because of their instability or feasibility or any other reasons? Or is there is any (other) way to (theoretically) make these compounds (if they exist)?


texts: How does the screening effect work for orbital in the same shell?

texts: Energy of an orbital in a single electron system depends solely on n, while energy of orbital in multi electron system depends on n and l, why is that? I understand that the screening effect is at work between two different shells, but how does it work in the same shell, is there any other reason?


texts: Why does 2-chloropropane's mass spectrum have a peak at 27?

texts:
I have noticed that all halogenoalkanes of the form 2-Xpropane seem to have a mass spec peak at 27, implying that a $\ce{C2H3+}$ ion is being formed.

Forming a $\ce{C2H3+}$ ion, however, would mean breaking three bonds and, given its abundance, that wouldn't make sense - especially in the case of 2-chloropropane where it has an abundance of 25.36 according to this
 website.

Why exactly does the $\ce{C2H3+}$ ion form?

EDIT: You can also see this peak in the mass spectrum of 2-bromopropane, 2-iodopropane and 2-fluoropropane, but it is less pronounced.

EDIT 2: as pointed out by @PLD, it appears that other molecules of this form have peaks at 27 for a different reason to that of 2-chloropropane, so my previous edit is irrelevant.


texts: What happens to promoters or poisons during a catalyzed reaction?

texts:
Catalysts are substances that influence reaction rates without undergoing changes in their mass and chemical composition, but may undergo physical changes.

Promoters, poison etc. affect the activity of the catalyst. What are some examples of promoters or poison undergoing a change (physical or chemical) during a chemical reaction?


texts: Can 25mL of 10% phosphoric acid substitute for 10mL of 25% solution?

texts:
Could I substitute $25~\mathrm{mL}$ of $10\%$ for $10~\mathrm{mL}$ of $25\%$ phosphoric acid solution?

This is for a measurement of free $\ce{SO2}$ in a sample of wine. The phosphoric acid is added to the wine sample and then more steps take it through a color change as it goes from acid to base. Finally a reagent is added dropwise to measure the amount of free $\ce{SO2}$ in the wine.

The full test is set out at More Wine.com as "Test for free SO2 in wine".


texts: Calculating Heat Release from Bomb calorimeter

texts:
When $0.400\ \mathrm g$ $\ce{CH4}$ is burned in excess oxygen in a bomb calorimeter that has a heat capacity of $3245\ \mathrm{J/^\circ C}$ a temperature increase of $6.795\ \mathrm{^\circ C}$ is observed. What is the value of $Q_V$?

I thought it was the regular $Q=mc\Delta T$ problem but it isn't and not only that I did the equation but it didn't work.

I am not sure what to do right here at the moment

  Using the data determine standard enthalpy change for the combustion of methane

Also I would like the definition of the standard enthalpy change and what it tells you and the purpose of it.


texts: Proportion of gases filled in cylinder of sea-divers

texts:
In my book it is given that earlier cylinder were filled with 2% oxygen and 98% helium. Nowadays it is filled with 11.7% helium, 56.2% nitrogen and 32.1% oxygen.

There are few questions which come up in my mind

Earlier 2% oxygen is changed to 32%. So was 2% oxygen enough for huaman?
98% helium is reduced to 11.7% why it is so?
I don't get reason why helium and nitrogen are filled?


texts: Is 6-ethenyl-4-(prop-2'-enyl) octa-6-en-3-ol a valid name?

texts:
I recently study organic chemistry and I read a book by Sana Jamshaid. I came across this compound and I cannot understand why it named 6-ethenyl-4-(prop-2'-enyl) octa-6-en-3-ol:

I understand that the longest chain is 8, hence octa (but if we go up on the 4th longest can be 9) but I don't understand the 4-(prop-2’-enyl). Are there any explanations to why the compound named in such way? The double bond also sits on the 7th and not the 6th.


texts: What causes the yellowing of the linear alkylbenzene (LAB) cocktail?

texts: In our lab, we use the liquid linear alkylbenzene (LAB) cocktail mixed with 2g/L 2,5 diphe-nyloxazole (PPO) as the organic scintillator for radiation detection. The new LAB cocktails are stored in the transparent glass bottles provided by the company. Although they are exposed to the daylight lamp in the lab, they are always very clear(see picture 1, the sample was put in a small glass vial). However, when we put some liquids into a transfer system, they turned to be very yellow after about two weeks (see picture 2). In the system, the LAB liquid was first stored in a large Acrylic vessel (acrylic is proved to be compatible with the LAB) and then went through the stainless steel tubes and valves (from Swagelok company), finally went into a small acrylic container or a glass jar for preventing spilling. There is no heating during the experiment, just some pressure changes created by a pump to make the LAB transfer from the large vessel to the small container. The LAB liquid may also contact with the rubber from O-ring for vacuum sealing, the Teflon tape, the plastic(PTFE) gas tube, copper lid, etc. So in our case, what may cause the yellowing for the LAB?


texts:
Can someone explain the appearance of the resonances at $\pu{4.6 ppm}$ (spectrum taken from here)?

Is it due to long range coupling? But the coupling constants are too high for such long range coupling. I assumed, according to the shift, that this is coming from the two protons nearest to the benzene ring?


texts: Chiral products from achiral reactants and 'principle of racemic mixture formation'

texts:
I have studied that if in a reaction system chiral reactants are absent but chiral products are produced; then all enantiomers of respective diastereomers are produced in equal concentration or a racemic mixture is produced.

But what is the reason behind this 'principle of racemic mixture formation'? Is it simply because as the enantiomers of respective diastereomers have no difference in physical or chemical properties, the reaction system shows no preference to any of them?


texts: Molarity to Percent, Mole Fraction, Molality

texts:
I have a series of questions similar to the following. I want to make sure I do this correct before I do the others. I am in need of a hint.

Given molarity of 6M NaOH with d=1.4g/mL, calculate, percent, mole fraction, and molality.

So in the above question, I have the molarity, but how am I supposed to get liters of solution?

I figured it was 6M per 1L of water, but then what am I supposed to do with the density? Is that the density of the water with the NaOH?

Then in a sub part it gives me the mole fraction as 0.1 with a density of 1.3g/mL. Why does the question give me that number? Is it possible to figure out percent, molality, and molarity based on mole fraction?

Thanks for you help.


texts: What happens at a molecular level when you cook meat?

texts:
When we cook food how does good smell produces? and which thing converts into taste.
Please ignore my English grammar mistakes.


texts:
I hope this is the right place to ask. I'm not a chemist so my question may seem obvious but it's not for me.

I work in the egg industry and we produce every hour 60 tons of dried egg shells as waste.
Those shells come in small grains (few millimeters) but can be further reduced to powder (like talco or marble powder).

This powder is $97~\%\ \ce{CaCO3}$ and $3~\%$ proteins.

What I'm interested in is an idea to recycle this product in a cost-effective way. At the moment a small part is used in cultivations but the rest is just stored in abandoned mines and I don't like the environmental impact that this solution has.


texts:
I've come across a statement in a paper* that's poorly explained, and I can't work out the reasoning behind it. I suspect this is embarrassingly basic, but could anyone please explain the theory behind the following (from the bottom of the second paragraph of the discussion)?

  For a reaction involving B(OH)4- and CO32-, a B(OH)4- can balance the charge of only 1/2 a CO32-, thus a dependence [of the B/Ca ratio in synthetic aragonite] on [B(OH)4-]/[CO32-]0.5 would be expected.

I'm unsure why a power law applies here.

* Holcomb, M.; DeCarlo, T. M.; Gaetani, G. A.; McCulloch, M. Factors affecting B/Ca ratios in synthetic aragonite. Chem. Geol. 2016, 437, 67–76. DOI: 10.1016/j.chemgeo.2016.05.007.


texts: Molecular visualization software for Raspberry Pi?

texts: I've been using our lab's code MCMD on my Raspberry Pi for fun and exploratory purposes. I'm trying to find a VMD, Avogadro, Ovito, or other equivalent that is usable on Raspberry Pi, e.g. to view .xyz or .pdb molecular dynamics trajectories, or simply single-state structures. I have found none so far; I'm using Raspbian OS.


texts: Dissolution of hydrogen sulphide gas in water, and its reaction with cement

texts:
INChO 2016 problem 1.8

Each Problem in this question paper is like a comprehension, whose each subpart picks up where the previous left. This makes reading the previous subparts nearly mandatory for solving Problem 1.8, in order to gain proper context, sorry for that! I've copied the most relevant parts here for this subpart though

Problem 1 in question paper, Answer key

Subpart 8 of Problem 1:

  Water vapour in this air condenses on the tank walls. H2S in the air then slowly dissolves in
  these droplets. Since oxygen is available in immediate vicinity of the droplets (because of
  high surface area to volume ratio as compared to sewage below), sulphur oxidizing bacteria
  (SOB) start accumulating in these droplets. In this new aqueous system, SOB oxidize
  sulphide species and produce sulphuric acid. The cement part in concrete walls can be
  represented as $\ce{(CaO)3(Al2O3)}$, which is attacked by sulphuric acid. Write the balanced
  reaction(s) responsible for sulphuric acid production in the water droplets and its possible
  reaction/s with the cement in concrete.

My attempt:

For the formation of sulphuric acid, I thought this:

$$\ce{H2S}+\ce{2O2->}\ce{H2SO4}$$

which seems a good enough redox reaction for me. (Sulphide oxidised to sulphate, whereas the oxygen got reduced).

This acid then formed should react with both $\ce{CaO}$ and $\ce{Al2O3}$ in the cement, because the former's a good base, while the latter's weakly basic and amphoteric anyway. Thus the second reaction should be:

$$\ce{6H2SO4\+(CaO)3(Al2O3)->3CaSO4\+Al2(SO4)3\+6H2O}$$

My query:

Neither of my answer's matches with the given answer, which is:

$$\ce{HS-(aq) + 2O2 + H2O -> SO4^{-2}
(aq) + H3O+}$$

and

$$\ce{CaO(s) + H2SO4(aq) -> CaSO4(s) + H2O}$$

I hope I've been clear enough, please help me understand where I went wrong. Thank you!


texts: Addition of inert gas at "constant volume"?

texts:
My textbook states that

  "The addition of inert gases at constant volume does not affect the equilibrium state of the reactants and products contained in that volume."

Although I am not questioning the truth behind this statement, I am very confused by it.

Let us consider a homogeneous gaseous equilibrium system contained within a closed cylinder. The cylinder has a very small hole on its side, through which an inert gas can be pumped in. This is how I visualize the addition of an inert gas to the system. Now, upon introducing a given amount of inert gas into the system, how does the volume remain constant in any way?

While deriving Van der Waals equation for real gases, I learned that the term $V$ in the ideal gas equation stands for the empty space that is available to the gas molecules for movement. Therefore, when we introduce an inert gas into the system, aren't we essentially decreasing this amount of space that is available to the reactant and product molecules for movement?

I am very confused. Please share your insights for it would be tremendously helpful for me. Thanks ever so much in advance :) Regards.


texts: Is it possible to prevent methane combining with oxygen?

texts:
The output from an anerobic kitchen waste digester is mostly $\ce{CH4}$, and $\ce{CO2}$.
If the methane is collected over water; algae/moss may use the $\ce{CO2}$ to grow. Yet oxygen is released ... which, together with methane, is a potent environment.

Will the oxygen, in this closed jar filled with water+algae+moss, recombine to form $\ce{CO2}$ and $\ce{H2O}$? Is there a means to prevent methane combining with oxygen released by the algae?


texts:
I'm doing an assignment where I have to research a radioisotope of my choice. I decided to do phosphorus-32 and my assignment requires me to explain how the isotope is made. There is very minimal information on the production of phosphorus-32 so I'm in a little trouble.

A brief explanation would be much appreciated!


texts: Why does density increases when adding nanoparticles in a mixture of water and some clay?

texts: I want to know that why density of drilling fluid which is a mixture of water, barrite, bentonite and carboxymethyl cellulose increases when i am adding silica nanoparticles. My ain of adding these nanoparticles is to improve the viscosity.


texts: Is it true that when hydrogen reacts with oxygen to form water, that if first forms an hydroxyl radical?

texts: When I took chemistry in high school, the inevitable question as to whether or not water has a chemical name came up. Our instructor said no, but if it did it ought to be called hydrogen hydroxide. His reasoning was that when hydrogen reacts with oxygen, it first form an hydroxyl radical that then reacts with another hydrogen molecule to finally form water; since the reaction that converts hydrogen and oxygen into water is so chaotic, that hydrogen molecule will almost certainly be a different molecule than the one that contributed the first hydrogen atom. Was our chemistry instructor correct? Is this actually how hydrogen and oxygen react to form water?


texts: Why does the second electron affinity has an opposite sign of the first one?

texts: Many first electron affinities are positive, indicating a favourable process, but the corresponding second electron affinities are negative. For example, the first and second electron affinities of oxygen are $+141$ and $-780~\mathrm{kJ~mol^{-1}}$ respectively. Why is this so?


texts:
I am under the impression that elements from the third period onwards can promote electrons into d orbitals to form hybridised orbitals. Why would an element in the third period promote an electron to the 3d orbital when we learn that 4s orbitals are filled first because they are lower in energy (is it to do with orbital penetration?)
Why also can a 2nd period p block element not promote to 3s?