texts: What would superionic water ice look like?

texts:
Phys.org's Giant lasers crystallize water with shockwaves, revealing the atomic structure of superionic ice links to

Nature Physics: Experimental evidence for superionic water ice using shock compression
Nature: Nanosecond X-ray diffraction of shock-compressed superionic water ice

Question: What would superionic water ice look like if it could be maintained at ultra-high pressure long enough? Would it be fairly transparent and have a low index of refraction like glass or "normal" water ice? Or would it be opaque or shiny, or perhaps transparent but high index of refraction like diamond?
With a description like "solid lattice of oxygen and liquid-like hydrogen superionic ice" it certainly sounds "shiny/metallic" to me!

The Phys.org article says:

In 1988, scientists first predicted that water would transition to an exotic state of matter characterized by the coexistence of a solid lattice of oxygen and liquid-like hydrogen—superionic ice—when subjected to the extreme pressures and temperatures that exist in the interior of water-rich giant planets like Uranus and Neptune. These predictions remained in place until 2018, when a team led by scientists from LLNL presented the first experimental evidence for this strange state of water. (emphasis added)
[...]
The researchers performed a series of experiments at the Omega Laser Facility at the University of Rochester's Laboratory for Laser Energetics (LLE). They used six giant laser beams to generate a sequence of shockwaves of progressively increasing intensity to compress a thin layer of initially liquid water to extreme pressures (100-400 gigapascals (GPa), or 1-4 million times Earth's atmospheric pressure) and temperatures (3,000-5,000 degrees Fahrenheit).
"We designed the experiments to compress the water so that it would freeze into solid ice, but it was not certain that the ice crystals would actually form and grow in the few billionths of a second that we can hold the pressure-temperature conditions," said LLNL physicist and co-lead author Marius Millot.
[...]
"Water is known to have many different crystalline structures known as ice Ih, II, III, up to XVII," Coppari said. "So, we propose to call the new f.c.c. solid form 'ice XVIII.' Computer simulations have proposed a number of different possible crystalline structures for superionic ice. Our study provides a critical test to numerical methods."


texts: Determining the concentration after half-life period

texts:
I was given the reaction

In diluted solution and with neutral pH, the reaction reacts according to a reaction velocity law of pseudo-1. order:

$$-\frac{dc_{DNPA}}{dt}=k_{obs},\quad k_{obs}=k\cdot c_{H_2O}$$

At $t=0$ we have $96\mu M$ DNPA.

How big is the concentration of DNPA and DNP after three half-time periods ($3\cdot t_{1/2}$)?

Of course, for DNPA we would just have $1/8$th of $96\mu M$ which is $12\mu M$. But what about DNP?

For me it's clear that it correlates directly with the concentration of DNPA since we have a heavy diluted solution, so the concentration of the water can be assumed as constant.

Further I know that $v_c(t)=\frac{1}{\nu_i}\frac{dd_i(t)}{dt}$ whereas $\nu_i$ are the stoichiometric coefficients. So basically, the concentration od DNPA, DNP and HOAc are the same since all have a stoichiometric coefficient of 1. Right? So they all change the same. Meaning: if DNPA changes to $1/8$-th, so does DNP and HOAc.

I am still a bit unsure, but can I now conclude, that $c_{DNP}(3t_{1/2})=12\mu M$?


texts: Reaction of electromagnetic radiations with the air pollutants

texts:
My friends, who are working on an IoT based technology project, explained their idea to me which is roughly like reducing air pollution by converting pollutants to oxygen ($\ce{O2}$) in any reaction, using waves and in particular microwaves. I have two questions in mind:

How do waves such as infrared, ultraviolet, microwave and others react with pollutants or in general with a gaseous mixture?
Which electromagnetic waves would be better in terms of factors such as time, temperature, rate of reaction and cost?

The pollutant mixture may contain all the pollutants described here, but the project is much more concerned with those that are more harmful than others to humans and life on earth.


texts: Discrepancy in Standard Hydrogen Electrode energy

texts:
From Absolute Electrode Potential on Wikipedia:

$$\ce{\frac12H2(gas) -> H+(aq) + e-(g)\quad(-(4.44\pm0.02)eV)}$$

The bond-dissociation energy of hydrogen is $\ce{4.52 eV}$:

$$\ce{\frac12H2 -> H\quad(-2.26 eV)}$$

The ionization energy of hydrogen is $\ce{13.6 eV}$:

$$\ce{H -> H+ + e- (-13.6 eV)}$$

How to address the discrepancy that the equations cannot add up in terms of energy?

Edit: of course I know that hydrogen ion in gas is different from hydrogen ion in aqueous solution... it is in my very essence. However, how come the enthalpy of formation of $\ce{H+(aq)}$ is zero?


texts: Is there a generic graphical language to represent chemical reactions?

texts:
I want to show a schematic representation of chemical reactions from start to finish in a way that will include more detailed preparation instructions than a plain chemical formula: volumes, concentrations, waiting time, temperature, etc.

Is there a graphical language for this kind of thing? I'm looking for something more sophisticated than a typical flow chart, and more targeted towards chemical reactions.


texts: Mass of iron from the reduction of iron(III) oxide

texts:
Given the equation
  $$\ce{Fe2O3 + 3H2 -> 2Fe + 3H2O},$$
  determine how many grams of $\ce{Fe}$ can be produced from $\pu{16.5 g}$ of $\ce{Fe2O3}$.

I've already determined the masses of each component. I believe the next step is convert the masses into moles, but after that, I'm not sure what formula to use.

Any help is greatly appreciated.


texts: What would be the product of this reaction?

texts: A 3 membered carbon ring with a double bond to oxygen from one carbon and a double bond between the remaining carbon with a methyl group attached to one of the carbon is made to undergo acid catalyzed hydrolysis. What will be the product?


texts: Solution to Raoult's Law for a volatile binary solution (no pun intended)

texts:
Raoult's Law

In a closed container, $$P_A=P_A^\circ x_A$$ where $P_A$ is the pressure of compound in gaseous phase, and $x_A$ is the mole fraction of the liquid component A in the liquid mixture. If the liquid is alone in the container, $x_A=1$.

Problem I'm trying to solve

  $A$ moles of compound $A$ and $B$ moles of compound $B$ are stored in
  container closed with a piston. External pressure on the piston is
  maintained as $P_e$. Find moles of $A$ and $B$ that will be found in
  the gaseous phase at equilibrium. ($P_A^\circ$ and $P_B^\circ$ are
  known values)

Attempt at solving

Let $a$ moles of A and $b$ moles of B exist in gaseous phase. This means $A-a$ and $B-b$ moles of respective compounds are leftover in the liquid phase.

Now Raoult's Law gives us

$$a \frac{RT}V = P_A^\circ \left(\frac{A-a}{A+B-a-b}\right)$$
$$b \frac{RT}V = P_B^\circ \left(\frac{B-a}{A+B-a-b}\right)$$

(Ideal gas equation used implicitly)

Also total pressure of gases inside should equal $P_e$

$$(a+b) \frac{RT}V = P_e$$

These are not ordinary linear equations, so I'm not totally sure my calculations are correct, but I'm getting the solution as

$$P_A^\circ \left(\frac Aa -1\right) = P_B^\circ \left(\frac Bb -1\right) = \frac{AP_B^\circ (P_e-P_A^\circ)+BP_A^\circ(P_e-P_B^\circ)}{(A+B)(P_A^\circ+P_B^\circ-P_e)}$$

So far so good, but it turns out that on plugging in specific values for $A,B,P_A^\circ,P_B^\circ,P_e$, $a$ and $b$ attain negative values.

Mathematically it can be proved that this happens when the rightmost expression is negative. The rightmost expression can be rewritten as

$$P_e \left[\frac {\frac{\frac{A}{A+B}}{P_A^\circ}+\frac{\frac{B}{A+B}}{P_B^\circ}-\frac{1}{P_e}} {\frac{1}{P_A^\circ}+\frac{1}{P_B^\circ}-\frac{1}{P_e}} \right]$$

Let $N$ mean numerator and $D$ mean denominator of this expression. We can prove that $N<D$. This means that $\frac ND >0$ if and only if $N>0$ or $D<0$ holds.

Question 1

Assuming all the calculations are correct, this seems to be a rather arbitrary mathematical condition. Can someone explain the physical significance of this? Like a more intuitive way to understand why we must check such an arbitrary condition rather than something as simple as $P_e>P_A^\circ+P_B^\circ$?

Question 2

If $\frac ND <0$, is the solution always $a=A$, $b=B$ (which means no liquid evaporates)?


texts: Reaction of acyl chlorides with diazomethane and silver(I) oxide

texts:
$$\ce{R-COOH ->[SOCl2,CH2N2][Ag2O/CH3OH] X}$$

While solving Carboxylic derivatives recently, I came across this.
so following the reagents one by one-
$\ce{SOCl2}$ will form acid chloride.
$\ce{CH2N2}$ (diazomethane) on the other hand reacts with carboxylic acid to give a methyl ester. but we are currently on acid chloride, this part is a little confusing to me.
$\ce{Ag2O}$ in aqueous/alcoholic medium should give ($\ce{CH3O-}$) ions.
How to proceed? What is wrong with my reaction mechanism?


texts:
Could stabilized aqueous ozone be bottled to prevent half life/sanitization window?

Typically upon creating stabilized aqueous ozone, it has a shelf life and a sanitization window of 24 hours from the time of production. Is this timeline due to oxidation, or would proper bottling prevent the degradation from occurring as fast? If not, is the process of it converting back to oxygen and water something that is inevitable due to time?


texts:
Which of the following samples contains the largest number of atoms?
a.    2.0 moles of $\ce{H3PO4}$
b.    3.0 moles of $\ce{H2SO3}$
c.    4.0 moles of $\ce{HNO3}$
d.    6.0 moles of $\ce{HClO}$
e.    8.0 moles of $\ce{HBr}$

My logic would tell me that every mole has $6.022\times10^{23}$ atoms in it. Then you divide the amount of grams of each compound by the number of moles?
so for A I'd  use the following:
(Avg # *2) / 98 grams/per mole of $\ce{H3PO4}$   = $1.22\times10^{22}$ atoms
and so on, but I don't get the right answer :/
$(2\times(6.022\times10^{23})$ = number of atoms = $1.20\times10^{23}$
$\ce{H3PO4}$ = 98 grams/mole
The answer is C btw, I just don't know to set up the equation right to get to this answer.


texts: Lack of elaboration in IR spectra of compounds

texts:
I've recently started learning about IR spectroscopy, and a common trend I'm seeing in my textbook and other sources is that not all the features in the IR spectrum are explained in detail. The focus is primarily on features whose results are known, and there is quite a bit of backward reasoning in deriving the structures of compounds from their IR spectra.
Consider the IR spectrum for Decane:

Here, what are the features causing absorption in the $\pu{720 cm^{-1}}$ range? Morrison Boyd states that C-C stretching causes absorption in the $\pu{1500-1600 cm^{-1}}$ range, and the absorption in the $\pu{3000 cm^{-1}}$ is explained in the figure, but I am unable to explain the other absorption.
Another example is the IR spectrum for Butanamine:

Here, what is causing the large absorption in the sub-$\pu{1000 cm^{-1}}$ region? Wouldn't such a large absorption at this frequency indicate unsaturation? How are we deducing then that it is an alkane?
The lack of explanation is a common feature for a lot of IR spectra presented in the text. Is this normal for someone learning IR spectra at this level? Also, any suggestions for other references for learning about IR/NMR spectra in more detail are appreciated.


texts:
In refining copper, an aqueous solution of copper(II) sulphate is electrolyzed, using impure copper as the anode and pure copper as the cathode.

At the anode, metal impurities higher than copper in the electrochemical series such as zinc, iron and lead are oxidized first, then copper loses its electrons to form copper(II) ions. Metal impurities lower than copper in the electrochemical series are hardly oxidized and deposit at the bottom of the tank as sludge. So, I have two questions:

If ions from metals more reactive than copper exist in the solution, why aren't they preferentially discharged first to form zinc or iron metal on the other copper electrode first rather than copper?
Why can the pure copper cathode be thickened with pure copper only?


texts: Nucleophilic Substitution with ethyl bromide and NaOH

texts:
Given is following nucleophilic reaction with product A. Draw the mechanism of the reaction and give the structure formula of A.

Here is my solution, I am sure it is not right. Could you help me, step by step to understand this reaction.


texts: Spatial form of an atom and type of chemical bond

texts:
As we know, the first excited states of Hydrogen atoms is $2p$.
The wave functions in cartesian basis we can represent as
$$
p_x          = \frac{1}{\sqrt{2}} \left( Y_{1, +1} + Y_{1, -1}\right)  =\sqrt{\frac{3}{16\pi}} \frac{x}{r}          \\
p_y          = \frac{i}{\sqrt{2}} \left( Y_{1, +1} - Y_{1, -1}\right)  = \sqrt{\frac{3}{16\pi}} \frac{y}{r}          \\
p_z          = Y_{1,0}                                                 = \sqrt{\frac{3}{4\pi}} \frac{z}{r}
$$
which is visulize in forms of dumbells:

My question as follows:

An H-atom in an excited state has the same shape?
How does an atom determines the axis along which to orient? Assuming that the directions equiprobable, the shape should be spherical. Or I'm wrong?
Type of chemical bond ($\sigma$, $\pi$, ...) is determined by the form of the type of atomic orbital ($s$, $p$, $d$, ..., or by their hybrides), but how it is possible if an atom is spherical yet?


texts:
Smaller particles in a colloidal dispersion are less stable than larger ones due to their higher surface to volume ratio.

Therefore Ostwald ripening occurs, a process which promotes growth of larger particles at the expense of smaller ones (alternatively aggregation of smaller particles can occur).

In principle, this process goes on until one single particle is obtained.

Then, why are colloidal dispersions with lots of small particles stable? Or rather metastable? What makes the processes promoting further growth stop (ie dissolution of smaller particles in Ostwald ripening)? And do these processes really stop or just slow down tremendously?


texts: Spectrometer vs Spectrometry vs Spectroscopy

texts:
How do you differentiate between the three?

I read that "Spectrometry deals with the measurement of a specific spectrum. There are four primary types of spectrometers:

Mass spectrometry  2. Neutron triple axis spectrometry 3. Ion-mobility spectrometry 4. Rutherford backscattering spectrometry"

How about Raman Spectrometers and Infrared Spectrometers. Don't they belong to spectrometry?

Some believe that the main difference is that spectroscopy typically deals with light, mass spectrometry does not.

So do you called it Raman spectroscopy or it is not right to refer it as Raman spectrometry?

It's confusing.


texts: What happens when salt water is electrolyzed with a copper anode and a copper cathode?

texts:
I heard that copper oxide is formed on the cathode and copper chloride is formed on the anode, is this correct?
I don't have much knowledge of chemistry, so I can't find out much by searching on Google.


texts: Formation of zwitterion from amino acids

texts:
Why it is easier for the carbonyl group to lose a proton to become negatively charged and the amino group to accept a proton to become positively charged?

I know it has to do with the very polar bond due to the oxygen. And the $\ce{H+}$ ions attracted to the lone pair of electrons on $\ce{N}$ in the amino group.

But I don't understand why would an electronegative atom such as oxygen wants to lose a proton.

I was told that they will attract more electrons towards towards them. But that does not help in my understanding of why protons will leave.


texts: Oxidation of Sodium Hydroxide in Ethanol?

texts:
So I read recently that:

  Alcoholic solutions of sodium hydroxide will oxidize in air, turning brown.

First is this true?

And if so what is oxidizing?

I can't think of what sodium hydroxide would oxidize to, and ethanol well wouldn't that oxidize to water and CO2!


texts:
I should point out first that I'm not a chemist, but I'm currently doing a little bit of chemistry; this should clarify that I don't have formal training in a chemistry lab (other than some basic chem classes in my BS).
So the question is this: what is standard practice for keeping salts moisture free if you can't afford a nitrogen generator system (or afford to swap nitrogen tanks out continuously with a desiccator chamber)?
I currently use iridium tetrachloride and I find that a few months after receipt, I have sludge (it's highly hygroscopic). I've tried storing in a tightly sealed bag with desiccant packs (the sealed kind) to no avail. I tried storing in a vacuum chamber but I can't hold vacuum for more than a few hours unless I have it on vacuum continuously (or hook it back up regularly).
I've been told by a local chemist that a simple vacuum desiccator chamber with a bunch of consumable silica gel at the bottom is about the best I can do, I just have to regularly pull vacuum again and swap the silica gel as soon as I see color change.
Thoughts?


texts: Electron configuration of iron(I) cation

texts:
What is the electron configuration of $\ce{Fe+}$ cation?
\begin{align}
\ce{Fe+} &\!:~ [\ce{Ar}]\mathrm{(3d)^6(4s)^1}\label{chm:1}\tag{1}\\
\ce{Fe+} &\!:~ [\ce{Ar}]\mathrm{(3d)^7(4s)^0}\label{chm:2}\tag{2}
\end{align}
What I've been told is that \eqref{chm:2} is correct since the $\mathrm{4s}$ electron jumps to $\mathrm{3d}.$
Which representation is correct?


texts: Does dissociation of molecules into atoms change the volume of mixture?

texts:
For example, if $\ce{H2}$ is converted to two $\ce{H},$ does the volume of the mixture change?

If it doesn't, does it imply that the work done is $0$ because work is $P\,\mathrm dV?$


texts: Increase in equilibrium concentration of the reactant via decrease in container volume

texts:
Consider the hypothetical reaction $\ce{3A(g) -> B(g) + C(g)}$; how to increase the equilibrium concentration of $\ce{A}$, given that the reaction is endothermic?

  increasing the volume of the container
  decreasing the temperature
  decreasing the volume of the container
  adding $\ce{B(g)}$ at equilibrium

Answer given - 2, 3, and 4. I have trouble with the option 3.

I know according to the Le Chatelier's principle, equilibrium will shift forward on reducing the container volume, but the solution says it still manages to have an increase in the overall equilibrium molar concentration of $\ce{A(g)}$; and that's what I'm not understanding.


texts: Is reverse osmosis a fancy term for filtration?

texts:
In Reverse Osmosis (RO) systems, the water to be purified is pushed against a semipermeable membrane and comes cleaner the other side, the path of water is the reverse of regular osmosis, hence the name.
However, it seems to me that this process is pretty similar to a regular filtration.
So, is RO just a fancy term for a fancy filtration?
What is it that justifies it not being called filtration, ultrafiltration or some variation of that?


texts:
In the treatment of HCl with acrolein 3-chloroprop-1-en-1-ol is the first product which is (my textbook says) unstable and turns into 3-chloropropanal.

Why is this 3-chloroprop-1-en-1-ol unstable? is −I effect of chlorine responsible?


texts: How do α,β-unsaturated acids undergo decarboxylation?

texts:
I know the concerted mechanism for β-keto acids, but neither could I figure out, nor was I able to find out the mechanism for α,β-unsaturated acids.
Any help is appreciated.


texts: Does H2SO or H2CO have a higher dipole moment?

texts:
Given these two molecules, I realize that the molecules are pretty identical in terms of the individual atoms' electronegativities (with Sulfur only being a small bit higher than Carbon). So then, the only factors that I can think of contributing to differences in dipole moment would be shape (tetrahedral vs trigonal planar), the lone pair, and the double bond. However, I don't know how to look at these three factors collectively to determine the net dipole moment.

How would I go about finding which one has a higher dipole moment?


texts:
Which of the following statements correctly interprets the relationship between ionization energy, atomic radius  Electron affinity when comparing two atoms.

The correct choice as per my instructor is that when atomic radius increase ionization energy decrease and electron affinity becomes less positive.

I do understand that as the atomic radius increase it becomes easier to remove and an electron due to shielding from multiple orbitals. Hence Ionization energy is decreased as the atomic radius increase. Additionally, electron affinity is an exothermic process.I am not sure how  electron affinity (addition of an electron) related to ionization energy and atomic radius. Please clarify. Thank you.


texts: By using the magnetic susceptibility, calculate the number of unpaired elections in the complex

texts:
I'm having trouble making sense of this answer. I believe I am doing all the steps right, but my main concern is that I am not arriving at a whole number. If my answer is correct, should I just round up or down?

Question

  By using the known values of $\chi$ for $\ce{HgCo(NCS)4}$ calculate the number of unpaired electrons in each of these complexes, and interpret the results in terms of the electronic structures of the complexes.

My Attempt

$$\ce{HgCo(NCS)4}\ 's \   \chi = 16.44 x10^{-6}\  \mathrm{CGS (g^{-1}\cdot cm^3) \ at \ 20°C}$$

$$\mathrm{\chi_M =16.44 \cdot 10^{-6}g^{-1}\cdot cm^3 * \frac{491.8528 g}{1 mol} =8.09\cdot 10^{-3} mol^{-1}cm^3}$$
$$\chi ' _M= \chi_M (\text{metal core electrons}) + \chi_M (\text{ligands}) + \chi_M (\text{other}) - \chi_M$$

Diamagnetic corrections include:

$$\begin{align} \ce{Hg^{2+}}&=40.0\cdot 10^{-6}\\ \ce{Co^{2+}}&=12.8\cdot 10^{-6} \\ \ce{NCS^-} &=26.2\cdot 10^{-6}\end{align}$$
Source

$$\chi ' _M=  (40\cdot 10^{-6})+(12.8\cdot 10^{-6})+(26.2\cdot 10^{-6})(3)-(16.44\cdot 10^{-6}) =-0.02418$$

then using the equation

$$\mathrm{\chi '_MT=\frac{1}{8}n(n+2)}$$
Assuming 298K and setting to zero
$$\mathrm{n^2 +2n-57.6722=0}$$

quadradic formula and i get
$$\mathrm{n=6.65}$$

I figure with all of that arithmetic it would be difficult to arrive at a whole number. So, my intuition is to round up to 7.

Is this approach correct? Which way should I round if so?

And I don't know how I would determine the electronic structure because there's two metal ions in the complex?


texts: A metal, M, forms two fluorides containing 40.43% F and 50.44% F by mass. Identify the metal

texts:
A metal, $\ce{M}$, forms two fluorides containing 40.43 % $\ce{F}$ and 50.44 % $\ce{F}$ by mass. Identify the metal.

I get that you can find out how much of the metal reacts with 1 mole of fluorine atoms in the 40.43 % one. This can be calculated to be 27.99 g.

Then from that you can work out that 28.49 g of fluorine reacts with the metal in the 50.44 % one and that that is about 1.5 moles of $\ce{F}$.

I'm a bit lost after that. How might you continue from here?

So the law of multiple proportions conveys that the fluorides contain fluorine in a 1.5:1 or 3:2 ratio. This means the possibilities are

$\ce{MF2}$ and $\ce{MF3}$, or
$\ce{MF4}$ and $\ce{MF6}$

Since there is twice as much fluorine, the mass of $\ce{M}$ in $\ce{MF2}$ must be 56 g. The next one is 112 g. If there are no errors in what was said, the metal must be iron or cadmium. What makes one a better candidate over the other?


texts:
My textbook says that for a chemical reaction with two reactants, $\ce{A}$ and $\ce{B}$ with equation $\ce{aA + bB -> Products}$, where $a$ and $b$ are coefficients, the general rate law is:

$\text{Rate} = k[\ce{A}]^m[\ce{B}]^n$

where $m$ and $n$ are the reaction orders for $\ce{A}$ and $\ce{B}$ respectively. Then it says that $m=a$ and $n=b$ if  the reaction between $\ce{A}$ and $\ce{B}$ occurs in a single step and with a single activated complex. Why is this true?


texts: How do atomic radius and nuclear charge influence ionisation energies?

texts:
This is actually a multiple choice question.

Why is the first ionisation energy of neon higher than that of fluorine?

A: Fluorine is more electronegative than neon
B: Neon has a complete octet, but fluorine does not
C: The atomic radius of fluorine is less than that of neon
D: The nuclear charge in neon is greater than that in fluorine

I understand why A is incorrect and why B is correct. But I am confused about C and D. I did try to search online but my questions just increased.
Firstly, why is the atomic radius of fluorine less than that of neon? Both fluorine and neon are in the same period which means that they have the same amount of shells. Since the nuclear charge of neon is more, shouldn't the nucleus attract the electrons in the outer shells closer? Which would result in neon having a smaller atomic radius than fluorine.
Secondly, according to a source, the largest factor is that the 2p sub shell in neon is full whereas in the fluorine it is not. They said that a full sub shell means that the atom is more stable which is the way neon has a higher first I.E. but since the 2p sub shell is full, wouldn't there be mutual repulsion?
I'm sorry if this is a lot, I'm trying to get a head start for my next education level and I cannot find any textbooks for that level's chemistry. I've been reading a summarized guide book and trying to do assessments whilst trying to find guides online as well.


texts: Reaction of chlorine with hot/cold solution of hydroxide

texts:
When chlorine reacts with cold solution of say potasium hydroxide, the disproportionation goes to lower oxidation states:

$\ce{Cl2 + 2 KOH -> KCl + KClO + H2O} $

Whilst with hot solution the oxidation state of chlorine goes up to $+V$:

$\ce{3 Cl2 + 6 KOH -> KClO3 + 5 KCl + 3 H2O} $

Why is that? Does the heat make the oxidation to higher ox. states easier?


texts: Inductive effect in cyclic compounds vs open-chained compounds

texts: Consider the two carbocations. Which one is more stable? I think it should be the open-chained one as it has 2 more H atoms than the cyclic one, so polarity will be greater; but I suspect that there might be some other factors at play  here due to the ring that I might have missed.


texts: What happen to the Salt in Water Electrolysis

texts:
I haven't found yet what happen to the Salt Ions in Water during Electrolysis and is there an Electron Flow or Ion Flow.
I have expierienced strong magnetic Forces between the Electrodes but couldnt measure an outside Magnetic Field.


texts: How can I set up and process my excitation-emission matrices properly?

texts:
I'm running EEMS on some water samples on a Horiba Fluoromax 4 spectrofluorometer. Method below.

$\pu{240-580nm}$ emission, $\pu{5nm}$ interval, $\pu{1nm}$ width.

$\pu{240-480nm}$ excitation, $\pu{5nm}$ interval, $\pu{1nm}$ width.

$\pu{0.01 mg/L}$ quinine sulfate standard in $\pu{0.5M}~\ce{H2SO4}$ + water.

Raman EEMS to use as references for my unknowns.

I use factory correction files for both detectors and then use the 3D profile button on my output charts. My data is only letting me export it as ASCII, and my quinine sulfate EEMS looks like the water Raman EEMS.
My questions are:

Is it possible my quinine sulfate is expired? I don't know how old it is (at least 2+ years, but it's been in the fridge in amber plastic). There's also a chance I set it up wrong which is why the signal just looks like water showing some Rayleigh scatter.

How can I export the images of my EEMs intensity profiles? I get an error saying I need to convert my matrix to a worksheet first, but I don't know how to do that.

Finally, how do I get an intensity map of my EEMs (heat map)? Does that happen in Matlab/R? There's a button in FluorEscence to get a 2D intensity map, but it doesn't seem to do anything. Maybe I'm only supposed to export ASCII and the Matlab/R package makes an intensity map. I'm not sure, but the manuals and help for the Horiba software aren't helpful in the least.


texts: Can hydronium function as a ligand? For instance could there exist $\ce{[Al(H3O)4]^{+7}}$ or $\ce{[Fe(H3O)6]^{+9}}$ cations? I asked my chemistry teacher and he said that he's never encountered a coordination compound with cationic ligands (however I know that there are because $\ce{NO+}$ can act as a ligand). What are the properties of these cations, if they exist? How are they synthesized? And finally, how would you name these complexes?


texts: Ionisation Energy vs First Ionisation Energy

texts:
It was stated in a textbook that the first ionisation energy is

  the minimum energy needed to remove one mole of electrons from one mole of gaseous atoms in their ground state

Is there a difference between ionisation energy and first ionisation energy?


texts: Why would the effect of fluoride ions Protecting egg shells from acid erosion vary with different acids?

texts:
I did an experiment reacting egg shells and acid. The egg shells were soaked in varying concentrations of fluoride and it is seen the rate of reaction between egg shells and acid decreases with higher concentrations of fluoride ions.

I performed this with hydrochloric acid, citric acid and ethanoic acid.  However the percentage decrease in the rate of reaction from the egg shells soaked in distilled water to the egg shells soaked in the highest concentration of fluoride ions Is calculated, it is largest for HCl, then citric and ethanoic with a 10-20% difference each time

This showed that fluoride had a greater effect for HCl than citric.

Why would this happen?


texts: What software can calculate aqueous solution equilibria?

texts:
What software is available out there to calculate the equilibrium in a set of reactions in aqueous solution? In particular, I'm interested in software general enough to simulate things like titration curves involving acido-basicity, complex formation, precipitation…

A web search turns up plenty of academic papers giving algorithms to find the equilibrium of such systems, but I'd like to find software that actually performs it. In particular, it would be really helpful if there existed such software that included a decent database of reaction constants for some well-known reactions (pKa for common acide-base couples, complexation and precipitation constants, etc.).

Edit: Apparently I was unclear: I'm not looking for molecular simulation codes, but for software that can calculate chemical equilibrium in solution from initial concentrations and a database of equilibrium constants for each possible reaction. The kind of thing teachers can use to predict titration curve and demonstrate the effect of various initial concentrations to students.


texts: How does a catalytic poison reduce a catalyst's activity?

texts: How does a catalytic poison reduce a catalyst's activity, such as palladium used in the hydrogenation of alkenes or any other such catalyst?


texts: What is meant by equal chemical environment in NMR?

texts: I am studying NMR and the concept of chemical equivalence is confusing. What does it mean exactly? Does it involve having different atoms to the left, right, up and down of a particular hydrogen in question? Please explain. Also I don't understand diastereotopic hydrogen give two shift? Like wouldn't rotating the bonds give same chemical environment to the two hydrogen giving them one signal. I am confused.


texts: How exactly can an increase temperature be used to break the chemical bonds of a gas [SO2, for example]?

texts:
So I understand the ideal gas law at a basic level, and that a rise in temperature can break bonds, however, I am unclear of how this works in a practical sense.

Say I have a container full of $\ce{SO2(g)}$ and I would like to break $\ce{SO2}$ into Sulfur ($\ce{S}$) and molecular oxygen ($\ce{O2}$). Would simply increasing the heat of the container to $n~\pu{K}$ be sufficient to break the bonds to get $\ce{S}$ and $\ce{O2}$ by themselves?


texts: How is 1-bromo-3-chloropropa-1,2-diene ($\ce{BrHC=C=CHCl}$) chiral? It doesn't have any carbon that is connected to four different groups.


texts: Are polar bond stronger than non-polar bonds?

texts:
I came across Pauling's electronegativity scale in which he noticed that the experimental bond enthalpy of X-Y is always greater than the average of X-X & Y-Y and proposed that the difference, D, between the experimental bond enthalpy and the average of X-X & Y-Y gave a measure of the ionic character/polarity of the bond/ electronegativity difference
This seems to imply that the greater the electronegativity difference, the higher the bond dissociation enthalpy (as compared to the average of X-X & Y-Y).
I can't think of any explanation for this though. I came across one explanation stating that the partial charges result in an extra electrostatic attraction, but I can't find any reliable source for verification


texts: Generating geometries for substituted molecules

texts:
I would like to automate some of my calculations, and I am looking for a tool to generate reasonable good initial geometries.

The details: I have already optimized molecular geometries, and I would like to perform calculations of several different substituted version of the molecule. Because of the size of the system, it would make sense to keep the already optimized geometry and exchange e.g. selected -H atoms to some R1, R2 groups. Is there any library that can manipulate 3D geometries this way?

I am aware I can do similar things with much graphical software (GausView etc).  However, the point would be automation: a command line tool or a library or something similar that I can call from Python scripts, instead of me clicking things on a screen one by one.

I am also aware that I can generate 3D geometry from 2D or such. However, I would like to keep the already optimized main part of the molecule (it can be pretty big), for more efficient calculations, and insert new groups. I appreaciate any help, thanks.


texts:
In a closed system (think of a typical AC system) why does refrigerant tend to condense and settle in oil?
I’ve heard that the vapor pressure of the oil is very low so that causes a pressure difference which draws the refrigerant into the oil and causes it to condense. The refrigerant is more dense than oil so it will tend to settle below the oil. Once enough refrigerant condenses in the oil the vapor pressure will be equal to the vapor pressure in the system so there will no longer be any flow.
I work in HVAC and I’m not satisfied with just knowing the practical side of this effect (refrigerant migration), I’d like to know how exactly this works. Maybe I lack a deep enough understanding of vapor pressure.
I understand that refrigerant and oil have different vapor pressures but I have trouble understanding how this causes flow since the entire system is under the same amount of pressure. Also why does it tend to condense into a liquid? How much refrigerant must condense and settle below the refrigerant before pressures are equalized?
Formulas are appreciated.


texts: How does benzene react with $\ce{NaNO2/HCl}$? Will $\ce{PhNO}$ be obtained? I read that pyridine can be produced under special conditions, but what will happen in some less exotic conditions?


texts:
How do you know if a polymer is a thermoset or a thermoplastic? For example:

hydroxybutanoic acid
2-amino-3- hydroxybutanoic acid

(I am not sure if these are correct in English)

I know what thermosets and thermoplastics are, and their properties, but I don't know how to see if polymers of a certain molecule is a thermoset or a thermoplastic by looking at the structural formula.


texts: Inductive vs conjugation effects in ester hydrolysis

texts:
I just came across the following problem about alkaline ester hydrolysis:

Since all of the substituents are in the para position, I immediately thought about the ability of those substituents to contribute electron density (through conjugation) to the ring and, therefore, the carbonyl group. Thus, I ruled out the p-methoxy and the p-toluene compounds since their conjugation effects lowers the electrophilicty of the carbonyl group.

Since I knew that chloro groups are ortho-para directors in electrophilic aromatic substitution, I also concluded that the chloro group also donates electron density (as shown below) and should also be less reactive at the carbonyl group than the non-substituted benzene ester, which I concluded to be the most reactive compound.

However, the answer key says that the p-chloro compound is the most reactive due to its electron-withdrawing abilities (which should be through induction only).

However, wouldn't those effects be minimal in comparision to the conjugation effects, or does the large nature of chlorine's 3p orbital vs carbon's 2p orbital make conjugation mininmal?


texts: What is the activation energy of a Daniell cell?

texts:
I'm having trouble finding a posted literature value for the activation energy for the Daniell cell redox reaction:

$$\ce{Cu^2+ + Zn -> Cu + Zn^2+}$$

Where might I be able to find this information?


texts: How is the selective titration testing equation simplified?

texts:
When there is $\ce{N^m+}$ and $\ce{M^n+}$  metal ions in a solution with respective m and n charge,
$\ce{N^{m+}, M^{n+}}$ reacts with EDTA($\ce{Y}$) as follows:
$$\ce{N^m+ + Y^4- <=>  NY^{m-4}}$$
$$\ce{M^n+ + Y^4- <=>  MY^{n-4}}$$
Formation constant for each chemical reaction,
$$\ce{K_{NY^{m-4}}} = \frac{\ce{[NY^{m-4}]}}{\ce{[N^{m+}][Y^{4-}]}}$$
$$\ce{K_{MY^{n-4}}} = \frac{\ce{[MY^{n-4}]}}{\ce{[M^{n+}][Y^{4-}]}}$$
where as $\ce{N^m+}$ has the higher value for formation constent KNYm-4 > KMYn-4
Fraction of each ion exsists ${α}$, $\ce{[N_{total}][M_{total}][Y_{total}]}$ are the total concentraion of the ion in any form.
$\ce{α_{Y^{4-}}}$ = $\frac{\ce{[Y^4-]}}{\ce{[Y_{total}]}}$
$\ce{α_{N^{m+}}}$ = $\frac{\ce{[N^m+]}}{\ce{[N_{total}]}}$
$\ce{α_{M^{n+}}}$ = $\frac{\ce{[M^n+]}}{\ce{[M_{total}]}}$
After $\ce{N^m+}$ has reacted with EDTA,the remaining amount EDTA is used for $\ce{M^n+}$
$$\ce{[Y^{'}_{total}] = [Y_{total}] + [NY^{m-4}]}$$
Where as $\ce{α_Y^{'}}$ is,
$$\ce{α_{Y^{'}}} = \frac{\ce{[Y_{total}]}}{\ce{[Y^{'}_{total}]}}$$
These are all the definition constants but I have no clue how this equation came
$$\ce{K''_{MY^{n-4}} = K_{MY^{n-4}}α_{M^{n+}}α_{Y^{4-}} - α_Y^{'}}$$
To perform a selective complexometric titration this condition need to be satisfied,
$$\ce{K''_{MY^{n-4}} = K_{MY^{n-4}}α_{M^{n+}}α_{Y^{4-}} - α_Y^{'} \geq 10^7}$$
where αY' is given below,
$$\ce{α_{Y'}} = \frac{1}{\ce{(1 + K_{NY^{m-4}}α_{N^{m+}}α_{Y^{4-}}[N_{total}])}}$$
Using EDTA as for an example Y4-
How did this equation came with the assumptions (The simplified equation)
$$\ce{K''_{MY^{n-4}}} = \frac{K_{MY^{n-4}}α_{M^{n+}}α_{Y^{4-}}}{K_{NY^{m-4}}α_{N^{m+}}α_{Y^{4-}}[N_{total}]}$$
One of the assumptions would be
$$\ce{ K_{NY^{m-4}}α_{N^{m+}}α_{Y^{4-}}[N_{total}] \gg 1}$$
Addition of one can be neglected.
What are the assumption do need to use to get the simplified expression
Can someone help me just using basic mathematics did not help I tried it by myself but no luck I am pretty sure I have missed some assumptions


texts: What happens when chemical equilibrium is restored after being disturbed?

texts:
I'm aware that, according to Le Chatelier's principle, a reaction will shift its equilibrium position in order to counteract the disturbance at equilibrium. However, I don't know what that means after equilibrium is re-established.

For example, take the generic reaction

$$\ce{a A + b B <=> cC}$$

At some point, equilibrium is disturbed, causing the forward reaction to be favored. Once equilibrium is re-established, how do the concentrations of the species compare to before equilibrium was disturbed?


texts:
Write balanced equations for each step, and an overall equation, for the preparation of sodium peroxoborate hexahydrate from the reagents borax, $\ce{NaOH}$, and $\ce{H2O2}$.

Borax was added to a solution of $\ce{NaOH}$, then it was treated with $\ce{H2O2}$, then cooled to form a precipitate. Please help.

(No structures are necessary, simply the chemical formulas will suffice)


texts: What is the point of introducing virtual orbitals in Hartree-Fock calculations?

texts:
Let us for simplicity discuss RHF formalism. For $2n$-electron system we have $n$ Hartree-Fock equations written for $n$ spatial orbitals $\{ \phi_{k} \}_{k=1}^{n}$
$$
\newcommand{\mat}[1]{\boldsymbol{\mathbf{#1}}}
$$
\begin{equation}
    \hat{F}(1) \phi_{k}(1) = \varepsilon_{k} \phi_{k}(1) \, , \quad k = 1, 2, \dotsc, n \, .
\end{equation}
Once we introduce finite basis $\{ \chi_{q} \}_{q=1}^{m}$ and express spatial orbitals as a linear combination of basis functions $\chi_{q}$
\begin{equation}
    \phi_{k}(1) = \sum\limits_{q=1}^{m} c_{qk} \chi_{q}(1) \, , \quad k = 1, 2, \dotsc, n \, .
\end{equation}
we end up with $n$ Roothaan–Hall equations
\begin{equation}
    \sum\limits_{q=1}^{m} F_{pq} c_{qk} =
    \varepsilon_{k} \sum\limits_{q=1}^{m} S_{pq} c_{qk} \, ,
    \quad k = 1, 2, \dotsc, n \, ,
\end{equation}
which can be rewritten in the following matrix form
\begin{equation}
    \mat{F} \mat{c}_{k} = \varepsilon_{k} \mat{S} \mat{c}_{k} \quad k = 1, 2, \dotsc, n \, .
\end{equation}
The Fock matrix $\mat{F}$ and the overlap matrix $\mat{S}$ are both $m \times m$ square matrices, $\mat{c}_{k}$ is a column $m \times 1$ matrix, $\varepsilon_{k}$ is just a scalar value.

We can then collecl all $n$ $\mat{c}_{k}$ column $m \times 1$ matrices into one $m \times n$ matrix $\mat{C}$ and all $n$ values $\varepsilon_{k}$ into $n \times n$ square matrix $\mat{\varepsilon}$
\begin{equation}
    \mat{F} \mat{C} = \mat{S} \mat{C} \mat{\varepsilon} \, .
\end{equation}

In practice, however, we extend both $\mat{C}$ and $\mat{\varepsilon}$ to $m \times m$ matrices from $m \times n$ and $n \times n$ respectively, which results in having $m-n$ virtual (unoccupied) orbitals.

Taking into account that virtual orbitals are even more unphysical than their occupied counterparts the question is what is the point of such extension of $\mat{C}$ and $\mat{\varepsilon}$? Why do not we just leave them of $m \times n$ and $n \times n$ sizes respectively?


texts: Do isotopes have the same ionization energy?

texts: When learning about isotopes and IE in High School this question have come to my mind recently. I have asked the teacher, she told me that she read articles about it however could not come to a conclusion, given that she doesn't know English, I think her research may be shallow. Nevertheless to put it another words does the neutrons have any effect of the IE particularly the first one?


texts: Comparison between van der Waals radius and metallic radius

texts:
I was reading about different types of atomic radius. It was written that if any atom can possess all the three types of radius, then van der Waals radius will be greater than metallic radius. However from the above diagram, it appears that the van der Waals radius and metallic radius are equal.

Then how can the van der Waals radius be greater than metallic radius?


texts:
I would like to setup something up my office to accurately measure the amount of Carbon Dioxide (CO2) being released from beans.

I looked at the site http://examples.yourdictionary.com/examples-of-ways-to-measure-volume.html which suggests several methods, the first of which, fluid displacement, I was going to employ. I know that CO2 is slightly soluble in water so I was going to use a saline solution/brine to reduce solubility. Can anyone help me here in explaining additional things that I should be doing to reduce errors in measurement with this fluid displacement method, other than of course reducing the possibility of air leaks and CO2 solubility? For example I have been reading about the risk of water evaporation in the measuring cylinder so I wonder how this can be minimised? I've also heard about the vander waals methodology for accuracy in calculation.

What other methods should I be considering? I'm not asking for better methods as I realise that's subjective, but other methods that you believe I should be investigating as possible alternatives. I have looked at a gas syringe and a balloon as alternatives.


texts: Why does the PH3 geometry deviate more from the trigonal planar one, than does NH3?

texts:
$\ce{PH3}$ has a more bent structure than $\ce{NH3}$. The HOMO-LUMO gap for $\ce{PH3}$ is smaller than for $\ce{NH3}$, and so the distortion from the trigonal planar geometry is said to be larger. However, why is the HOMO-LUMO gap smaller for $\ce{PH3}$?

It should be possible, I suppose, to argue for why this is so by using qualitative molecular orbital theory, and from looking at the construction of the molecular orbital diagrams, but I am not sure how to construct accurate MO diagrams for $\ce{PH3}$ and $\ce{NH3}$.

In the answer to the possible duplicate question, it seems to be taken for granted that some distortion from the planar structure is stabilizing. In my question, the starting point is the planar structure, and then looking at why $\ce{PH3}$ is in a more distorted geometry than $\ce{NH3}$, relative to the planar structures.

This distortion is often explained in terms of the "HOMO-LUMO gap", but I fail to see how the HOMO-LUMO gap can be assessed qualitatively in order to predict which of $\ce{NH3}$ and $\ce{PH3}$ is in a more distorted geometry. So what factor ultimately leads to the smaller HOMO-LUMO gap in $\ce{PH3}$? $\ce{BH3}$ exists in a trigonal planar geometry - why is not this molecule pyramidalized?


texts: Importance of higher order exchange terms?

texts:
The MP2 ground state energy of a molecule or solid can be written as

$$E^{(2)} = \frac{1}{2}\sum^{\text{occ.}}_{ij}\sum^{\text{virt.}}_{ab} \frac{\langle ij | ab \rangle [\langle ab|ij \rangle - \langle ab|ji\rangle]}{\varepsilon_i + \varepsilon_j - \varepsilon_a - \varepsilon_b}$$

where the first part of the numerator is commonly called "direct MP2" and the second part "exchange MP2", since i and j are exchanged.

However, for energy differences, it is often sufficient to calculate only the direct MP2 energy, since the contribution of the exchange part is mostly negligible. For the same reason the random phase approximation, which consists of these "direct terms" up to infinite order, works so well for many materials.

But are there good examples (materials or molecules) where the exchange term is important? I guess magnetic systems or situations where Pauli repulsion is important... but does someone know particular examples?


texts: Wondering how I should have graded this question (freshman lab, about buffer capacity)

texts:
I TA the intro freshman lab course. In a lab about buffers and buffer capacity, the students were instructed to make 50 mL of a 0.1 total molar pH 6.70 buffer by dissolving solid $ KH_2PO_4 $ and $ K_2HPO_4 $. The students then had to add a drop or two of NaOH and HCl to the buffer and see if/how much the pH changes. Next, they are supposed to dilute the buffer to double volume with DI water, and repeat. Then respond to the following questions:

1: How did diluting the buffer effect the change in pH when a few drops of NaOH or HCl were added?

2: Did adding water to the buffer change its pH? Explain why or why not.

For #1, obviously, diluting the buffer lowers its buffer capacity, so the pH change in the diluted buffer will be more drastic. I was a bit unsure about how to grade #2, however.  Some of the answers I got were:

"The pH raised slightly but was small enough that it was probably random  fluctuations in the pH meter"

"We didn't measure a pH change"

"The pH went up as DI water has a pH of 7 which is above the buffer, so even though the buffer resists change, it'll change a little"

If you look at the Henderson-Hasslebalch equation:

$ pH = pKa + \log(\frac{[A^-]}{[HA]}) $

Since both pH of the buffer was 6.7, and the pKa of the system is also 6.7, $[A^-]$ and $[HA]$ must be equal, and since the total concentration was 0.1M, then $[A^-]$ and $[HA]$ are 0.05 M each. So if we dilute it to double volume with water, the concentrations become 0.02 M each; the ratio remains unchanged and the pH would still be 6.7.

In reality, when you dilute the solution, the Ka and therefore pKa of the $ KH_2PO_4 \leftharpoonup\rightharpoondown K_2HPO_4 $ equilibrium will change slightly, so the pH would be expected to change. For clarification, see this question: Does dilution of a buffer affect pH?

The issue is that this is an early lab in a freshman course and they certainly aren't expected to know about activity vs concentration or anything that complex yet. There is no answer key and I am not TA for the lectures, so I am not expected to go to them, so I don't know what they were told there, or in their textbook. My supervisor seemed to give a non-answer when I asked about this. So I was a bit unsure what kind of thing I should be expecting the students to write. The lab will be the same next semester and I want to know what sort of answers to accept.


texts: What is the shiny structure under a metal coating?

texts: I performed a hot dip aluminizing on steel for 15 seconds. Then, after I bent the steel to remove the coating easier, the steel under was rough, shiny, and metallic, and was different from the original steel.The layer seems to be random and has bumpy structures. I can't mechanically removed the layer. I couldn't have analyze it chemically. Could I conclude that it is an intermetallic layer of Al and steel?


texts: Calculating concentration of dissolved gas from its mole fraction

texts:
I came across the following (solved) problem in my textbook:

  The Henry's law constant for $\ce{O2}$ dissolved in water is $\pu{4.34 \times 10^4 atm}$ at $\pu{25 ^\circ C}$. If the partial pressure of oxygen in air is $\pu{0.4 atm}$, calculate the concentration (in terms of molarity, $\pu M$) of dissolved oxygen in water, in equilibrium with air at $\pu{25 ^\circ C}$.

The following is my attempt at a solution to the above problem:

From Henry's law, we have that

$$p{\ce{O2}} = K_\mathrm H \cdot x_\ce{O2}$$

where $x_\ce{O2}$ is the mole fraction of oxygen dissolved in the solution, $K_\mathrm H$ is the Henry's law constant, and $p_{\ce{O2}}$ is the partial pressure of oxygen over the liquid.

Given that the Henry's law constant for a mixture of water and some amount of dissolved oxygen is $\pu{4.34 \times 10^4 atm}$, this gives us

$$x_\ce{O2} = p_{\ce{O2}}/K_\mathrm H = 0.4/(4.34 \times 10^4) = 9.2 \times 10^{-6}$$

To calculate the concentration of oxygen in this mixture in terms of its molarity, I need to know the number of moles of oxygen present in the solution and also the number liters of water in which the oxygen is dissolved.

To calculate the number of moles of dissolved oxygen, I can use the following equation:

$$x_\ce{O2} = \frac{n_\ce{O2}}{n_\ce{O2} + n_\ce{H2O}}$$

However, no information regarding the number of moles of the solvent, water, has been provided.

Hence, I checked the solutions provided by my textbook and found that they have arbitrarily assumed that we are dealing with $\pu{1 L}$ of water.

My question is this: are we allowed to arbitrarily take the volume of water as $\pu{1 L}$ even when absolutely nothing has been mentioned about this in the problem?


texts: Reaction Mechanism with a Rate Determining Step

texts:
Just a quick question on how to deal with multiple intermediaries in a proposed reaction mechanism.

Here is the overall reaction:

$$\ce{I-(aq) + OCl-(aq) -> IO-(aq) + Cl-(aq)}$$

Here is the proposed mechanism:

$$
\begin{align}
\ce{OCl- + H2O &<=>[$k_1$][$k_{-1}$] HOCl + OH-} & &\text{(Fast equilibrium)} \\
\ce{I- + HOCl &->[$k_2$] HOI + Cl-} & &\text{(Slow/RDS, non-reversible)} \\
\ce{HOI + OH- &->[$k_1$] H2O + IO-} & &\text{(Fast)}
\end{align}
$$

A few things to note, the question does indeed label both the first reaction going forwards and the third reaction going forwards as $k_1$. It also mentions that we should treat the concentration of water as being constant.

Here is my question:
I know how to write the rate law for the Rate Determining Step as $k_2[\ce{I-}][\ce{HOCl}]$ and then I know I need to use the equilibrium expression in the first reaction to isolate concentration of $[\ce{HOCl}]$ as

$$[\ce{HOCl}] = \frac{k_1[\ce{OCl-}]}{k_{-1}[\ce{OH-}]}$$

but then I am confused about how to isolate the second intermediary $(\ce{OH-})$ so I can get the proper rate law. Should I use the third reaction?


texts: Standard Half-Cell Reduction Potential for Periodate to Iodine

texts: I'm looking for standard half-cell reduction potential $\ce{IO4-}$/$\ce{I2}$ in acid medium. Unfortunately I was unable to find the value in all comprehensible reference books. Hard to believe this values have not been measured or calculated so far.


texts: Identifying unknown compound using mass spectrum

texts:
I am currently studying the textbook Mass Spectrometry - A Textbook, third edition, by Jürgen Gross. In chapter  1.4.5 Statistical Nature of Mass Spectra, there's a following example:

It is important to be aware that a single molecule can only yield one ion of one $m/z$ value. This ion may either reflect the intact molecule or any of its fragment ions. Statistics on thousands of ion formations and dissociations are needed to generate a useful mass spectrum exhibiting signals at different $m/z$ where each of them can be assigned a relevant relative intensity. To understand this, simply imagine a single methane molecule that gets ionized and detected as a molecular ion: this would lead to a spectrum showing a single line at $m/z$ $16$, the intensity of which would have no meaning beyond ‘yes’ and ‘no’ (Fig. 1.7a). Alternatively, the molecular ion might fragment to yield a single $\ce{CH3+}$ ion at $m/z$ $15$; again, the spectrum would show only one line. In fact, such a spectrum could not tell us whether the peak is caused by a molecular or a fragment ion. Eight ions might lead to a spectrum where each ion corresponds to $33.3 \%$ relative intensity (as in Fig. 1.7c) even though other distributions would be possible. Eleven ions could scale the intensity in $20\%$ steps, while 23 ions could lead to a spectrum with $10\%$ steps. It is evident that a spectrum with intensity levels as accurate as $0.1\%$ has to be based on thousands of ions (Fig. 1.7f).

Reading this, I do not understand how the author used this mass spectrum to infer that the molecule in question is $\ce{CH3+}$. The author seems to imply that, given this mass spectrum ($m/z$ values of $16$, $15$, etc.), we are able to infer that the molecule is $\ce{CH3+}$, but he doesn't really explain how this is done.
I would greatly appreciate it if people would please take the time to explain how the author identified $\ce{CH3+}$.


texts: Volume of dibasic acid required to neutralise 0.04 mole of OH-

texts:
The volume of 0.1 N dibasic acid sufficient to neutralize 1 g of a base that furnishes 0.04  mole of OH− in aqueous solution is:

  200 mL
  400 mL
  600 mL
  800 mL

Since it is a dibasic acid, it has two ionisable hydrogen atoms and hence its n-factor is 2. I simply used $$V\cdot 0.1\cdot 2=0.04$$ and got volume as 200 mL. But however according to the answer key it is given as 400 mL. Now the answer key is not of the highest quality and often has errors, so it can be challenged (but you need to pay a decent sum of money for the chance that they may look into it). Am I right to challenge this question or am I missing something?


texts: In the chapter 'Chemical Equilibrium', I studied that chemical reactions tend to attain equilibrium. But my question is why? Why do chemical reactions attain equilibrium? Is there any reason why they do so? Please explain. I am really confused. Why rate of forward reaction ultimately becomes equal to the rate of backward reaction?


texts: Rietveld refinement "fronting" of peak signal

texts:
I was trying to refine a crystal structure using Rietveld refinement yesterday. The crystal structure is already known for a related compound and the powder pattern seems to show a phase pure compound. An automatic peak indexing and refinement gave a possible cell that matches the literature values. Using the Pseudo-Voigt function however did not lead to any good results as the function did not match the asymetric peak profile.

The profile itself shows something I'd call 'fronting', so there is a slope at the front of the peak but then the measured curve just falls off directly after the peak. I was looking for that in literature but I could not find the term 'fronting' here. There was something similar called 'transparent' or 'transparency' but I wasn't sure whether this is referring to the profile or thr setup.

Does somebody know what this effect is called and what type of refinement is used here instead of Pseudo-Voigt?


texts: Which salt is a surfactant and lowers the surface tension of the water?

texts: I am doing my experiment on the surface tension of the water. How to show the decrease of surface tension of water with the increase in the concentration of salt? Is there any salt that lowers the surface tension of the water?


texts:
At breakfast someone asked if the eggs were boiling. While obviously they meant the water for the eggs, but it lead to a discussion regarding if you can make an egg boil without it coagulating or even if you can heat a coagulated egg to the point that it starts boiling under special circumstances such as in an oxygen free environment to prevent combustion.

So would it be possible to make an egg boil without coagulation or otherwise destroying it? The shell would break either way so we can remove that for the experiment.


texts: Is there an explanation to the atomisation energy trend of transition metals?

texts:
I am familiar with the double hump trend for atomisation of transition metals, and I can explain the unusually low atomisation of $\ce{Mn}$ with the exchange principle, specifically that in the solid state the spins are more localised whereas for the gas/vapour the spins are able to match and hence there is a gain in exchange energy (stabilising).

However, what I am struggling to understand is (ignoring the middle drop due to exchange):

  Why there is a hump in the first place?

I have come across a few ideas, some suggesting that it is a bonding/antibonding situation, whereby, first you fill a d-band gap up to $\ce{Mn}$ and then an antibonding contribution comes in.

Is there a more eloquent way of explaining this trend?


texts: My teacher often recommends the usage of a smaller/more narrow measuring cylinder over a larger one while performing experiments but why is that? Does it help in accuracy in any way?


texts: How does the oxidation of NaI by sodium hypochlorite to give I+ work?

texts:
I'm in trouble with the oxidation of NaI by $\ce{NaClO}$, the reaction should give $\ce{I+}$ which then reacts by electrophilic substitution with an aromatic complex. As of now I've come to:

$$\ce{ ClO- (aq) + 2I- (aq) + 2H+(aq) -> I2 (s) + Cl- (aq) + H2O (l)}$$

But I can't then find a way to obtain then the electrophilic $\ce{I+}$ that should react.


texts: Where do the percents in empirical formula questions come from?

texts:
A typical empirical formula problem reads something like this:

  Determine the empirical formula for a compound that contains 35.98% aluminum and 64.02% sulfur. source

How would those percentages be determined in real life? Spectroscopy?

A percent composition problem would obviously yield percentages, but those start with compound formulas--there'd be no need to determine the empirical formula from the percentages.


texts:
$$r_n = \left(\frac{h^2}{4\pi^2me^2}\right)\times\frac{n^2}{Z} $$

Would I be able to calculate the radius of sodium ion ($\ce{Na+}$) with the help of the above Bohr atomic model formula?


texts: How to interpret TD-DFT results for finding λmax and amplitude

texts:
I am trying to understand how to interpret the TDDFT results ( I know there is another post for this but it does not answer my question ).   Here is part of the result from GAMESS:

I downloaded Chemissian and this is its result for this state:

I have two related questions:

1-How did it calculate this 1.41 from the amplitude of this state ?
2-Does it have anything to do with λmax ?


texts: What is the relation between chemical thermodynamics and chemical kinetics?

texts:
Can one be understood on the basis of the other or are they not interrelated at all?

The first thing my kinetics textbook demonstrated was how thermodynamics ignores time taken for a process whereas kinetics considers the time and rate of the process and hence kinetics is a more effective way to view change.

Also, I saw examples of highly thermodynamically feasible reactions which were not kinetically favourable in the sense that they were so slow that the entire process could be neglected as not happening.

Can one understand the thermodynamics of a reaction by studying it kinetics?

Or can one figure out the kinetics of a reaction by thermodynamical consideration?

Also, would it be a wise observation to say that thermodynamics is a largely theoretical subject while kinetics is a more experimental field?


texts: How can nucleophilicity be estimated accurately?

texts:
Given the following: $\ce{CN-,OH-,SH-,I-}$. Determine  the relative order of nucleophilicity in a protic solvent.

I know that, more the nucleophile is solvated by hydrogen bonding in a protic solvent, the lesser will be its nucleophilicity. Also, solvation depends upon the size of the anionic nucleophile or its charge density (smaller the size greater the solvation).

Again larger the size, greater will be the polarizability of the anionic nucleophile and thus stronger will be its nucleophilicity.

All these indicate that the larger the size, the greater the nucleophilicity will be, and so the relative order of nucleophilicity should be $\ce{I-}>\ce{SH-}>\ce{CN-}>\ce{OH-}$. But the answer is $\ce{SH-}>\ce{CN-}>\ce{I-}>\ce{OH-}$. So where have I gone wrong? How can I determine nucleophilicity accurately? Is there any other factor on which nucleophilicity depends?


texts: Is electron density a good measure of similarity between molecules?

texts:
I am looking for a good similarity measure between molecules in order to use it with machine learning algorithms. I found a paper, Carbó, R., Leyda, L. and Arnau, M. (1980), How similar is a molecule to another? An electron density measure of similarity between two molecular structures. Int. J. Quantum Chem., 17: 1185-1189. doi:10.1002/qua.560170612 where they propose a similarity measure based on the electron density $\rho$:
$$\varepsilon_{AB} = \int_V|\rho_A-\rho_B|^2\,dV$$
This can be expressed as the sum
$$\varepsilon_{AB} = \int_V\rho^2_A\,dV+\int_V\rho^2_B\,dV-2\int_V\rho_A\rho_B\,dV$$
The authors then retain only the third term of this sum because only this term refers to the difference between the molecules A and B, and then they normalize it arriving to their final similarity measure
$$r_{AB} = \frac{\int_V\rho_A\rho_B\,dV}{\left(\int_V\rho^2_A\,dV \right)^{1/2} \left( \int_V\rho^2_B\,dV \right)^{1/2}}$$
which is zero for completely different molecules, and one if A = B.

My question is: why the electron density $\rho$ is appropriate here? A large portion of the electron density is due to the core electrons that don't participate in chemical bonding. They spend most of the time near the nuclei, and don't influence the rest of the molecule very much.

Instead of using the total electron density $\rho$, wouldn't it be better to use the density of only valence electrons: $\rho_{val} = \rho-\rho_{core}$?

Elements along the same group of the periodic table have similar chemical properties but have very different $\rho$ because they have different number of core electrons. However, their $\rho_{val}$ will be similar.

Is my thinking valid or I am missing something? What is the influence of the core electrons besides screening a part of the nuclear charge and preventing the valence electrons to come closer to the nuclei? Are there any papers where the density of the valence electrons is used as a descriptor of the molecular structure?


texts: I have a product, which according to the MSDS is mostly D-Limonene. I don't have the means to chemically test it, but I did try dissolving polystyrene with it. Before I come check it again, should I expect how polystyrene "dissolves" in acetone? As a goop at the bottom, even as I add much excess acetone? Or, should I see it truly dissolved, a translucent, thick liquid, as with using MEK, or xylene?


texts: Which one is the healthiest to operate a lantern with: kerosene, diesel or sunflower oil?

texts:
Given a lantern (originally made for kerosene) however, I'm looking for the fuel which is the safest for indoor use.

I've already tried different kinds, and found three of them that burn just as nicely: kerosene, diesel and sunflower oil, which means, all of these seem to produce nearly the same light, the same heat, and none of them becomes smoky on a medium flame.

The only differences I experience:

Kerosene stinks quiet badly, and costs 5-6 times as much as the other two.
Diesel stinks just a little bit and is pretty cheap.
Sunflower oil doesn't stink at all and is the cheapest.

So from my experiences, I'd go with sunflower oil.

But the most important question is, based on which I will decide: Which one produces the least poisoning stuff when burnt? So what might be in the air I can't see and should be afraid of.

(once again: The lantern is always set to a flame that doesn't produce any visible smoke at all.)


texts: Stereochemistry of the product of crotonic acid with bromine

texts:
Is there a a simple rule for determining the stereochemistry for the product of a reaction between an unsymmetrical alkene like (2E)-but-2-enoic acid and bromine (anti reaction)?

If it's an anti reaction, does that mean that I just need to put each bromine atom on a carbon, which makes the two carbons of the double bond different configurations, like carbon 2 R and carbon 3 S, or the other way around?
And if it's a syn reaction, does that mean that the two carbons in the product need to be same configuration? If that's the case, I get it. But if it's not, how would you decide how would the bromines go in without models?
Last but not least, in the second part I need to do an elimination (I made this question by the way to understand this concept), how would I know if the product is E/Z?


texts: What is the liquid coming out of these Duracell batteries?

texts:
I picked up a remote control to a DVD player that I had not used in a couple months.  The remote control was stored in a clean plastic bag.

The bottom of the remote control is covered with a liquid.  Upon further inspection, I discovered that the liquid is coming out of the Duracell Coppertop (non-rechargeable) batteries in the remote.

The amount of liquid is substantial.  It almost completely covers the bottom of the remote control.

Typically, when batteries have problems, you see crystals forming.  But not so much in this case.  In this case, it is almost all liquid that has been discharged.

I did not initially notice the liquid, and so I picked up the remote, and then set it down on the furniture.

What is this liquid?  What chemical process took place that resulted in the liquid being discharged from the batteries?

(And, as a bonus, how to I get the liquid off the furniture?)


texts:
I just found a random example so I could highlight my inquiry:

  A chemist wants to make .5L of a 20M solutionusing $\ce{NaOH}$. The solution will be made from solid $\ce{NaOH}$ and water. How many grams of
  $\ce{NaOH}$ are needed to make this solution?"

In this case, I am finding the moles of $\ce{NaOH}$ that would equate to the number of moles in 0.5L of a 20M solution. But, is it saying that (x grams of $\ce{NaOH}$ + x volume of $\ce{H2O}$) make up the total 0.5L ? or am I adding x grams of $\ce{NaOH}$ to .5L of $\ce{H2O}$ and not considering the changes in volume?


texts:
According to the $2n^2$ rule, the fifth shell should accommodate 50 electrons.

However, my chemistry book says that the $2n^2$ rule does not apply to the fifth shell.

Could you explain why this happens?

P.S. I have studied quantum numbers, Heisenberg uncertainty principle, Pauli exclusion principle, and the quantum mechanical model of an atom; please answer accordingly.

Thank You


texts: Dielectric constant for gases possessing van der Waals forces

texts:
I've learnt that water can dissolve ionic bonds because it possesses a high dielectric constant.
In the cases of covalent compounds (especially the non-polar covalent compounds), where the molecules are held together by mainly van der Waals forces of attraction. They are said to possess a higher dielectric constant.
In the case of inoic compounds where they are held together by electrostatic force of attracrion, water is a solvent that can dissolve almost all the ionic compounds ,the reason stating  it to have "high dielectric constant".
Then why is that covalent compounds cannot be dissolved by an ionic solvent such as water? And is there any connection to this topic as to  how most of the non-polar covalent compounds are immiscible in ionic solvents?


texts: If we start heating a substance, does it melt when we break its intermolecular bonds?

texts:
I was reading the 2 following posts:

Do substances melt when we break their intermolecular bonds?
Is melting/boiling point of ionically bonded substance higher than of covalently bound?

Altough they both contain wonderful answers, I did not understand if melting can be caused just by the break of the intermolecular weak bonds, while we're heating the substance.


texts: Is it possible to have a fully opaque 'switch glass'?

texts:
Current switch glass (smart glass) technology permits for a transparent glass to become semi-transparent, i.e., translucent.

For my application, I was wondering if it was possible to make a 'smart glass' opaque on removing or applying electric current.

Opaque, as I'm using it now, refers to being able to block out most light that gets to it.


texts: Are the various forms of polyethylene polymorphs?

texts: Polyethylene (PE) plastics comprise high density PE, low density PE, cross-linked PE (PEX), linear PE, low density and high density linear PE, etc. Are these all considered polymorphs, or is there another name for them? (Polymorphism refers to crystal structure, so I'm thinking the various forms of polyethylene probably aren't polymorphs.)I guess a more general form of this question is: what is the name for the same basic chemical (polyethylene, in this case) that can form different compounds with different properties based on how the basic molecule branches (isomer doesn't quite seem to fit, either)?


texts: Why doesn't the carbon dioxide produced by a fire put out said fire?

texts:
Carbon dioxide ($\ce{CO2}$) is used in some fire extinguishers to put out fire, but a combustion reaction itself produces $\ce{CO2}$. Why do we get fire then?

$$\ce{CH4 + O2 -> CO2 + H2O}$$

Why doesn't this $\ce{CO2}$ put out the fire?


texts:
The equilibrium constant for the dissociation of dinitrogen tetraoxide is $K_c=5.9 \times 10^{-3}$.

If $\mathrm{1.00\ mol}$ of $\ce{N2O4}$ and $\mathrm{0.500\ mol}$ of $\ce{NO2}$ are initially placed in a container with a volume of $\mathrm{4.00\ L}$, calculate the concentrations of $\ce{N2O4(g)}$ and $\ce{NO2(g)}$ present when equilibrium is achieved at $\mathrm{25\ ^\circ C}$.

I created an ICE Table for $\ce{N2O4 <=> 2NO2}$:
$$\begin{array}{|c|c|c|} \hline
\ & \ce{N2O4} & \ce{NO2} \\ \hline
I & \dfrac{1.00}{4.00} & \dfrac{0.500}{4}\\ \hline
C & \dfrac{-x}{4.00} & \dfrac{+2x}{4.00} \\ \hline
E & \dfrac{1.00-x}{4.00} & \dfrac{0.500+2x}{4}\\ \hline
\end{array}$$

So then I let
$$5.9\times 10^{-3}=\dfrac{\left(\dfrac{0.5.00+2x}{4.00}\right)^2}{\dfrac{1.00-x}{4.00}}$$
So products over reactants, and I divided by 4 since to get the concentration, the number of moles needs to be divided by the volume which is 4dm^3.
After doing that I got $x=-0.167$ and $-0.339$, which is clearly wrong.

Correct answers: $\ce{[N2O4]}=0.292$ and $\ce{[NO2]}=0.0418$.


texts: What are typical runtimes for CASSCF calculations?

texts: I'm doing single point energy calculations of FeS using ORCA. I originally used DFT with a variety of functionals, and these calculations all took less than a minute. Now I'm attempting to run CASSCF calculations using 8 active orbitals, 12 active electrons, and the aug-cc-pVTZ basis set. It's been running for 3 days. Is this typical, or should I be attempting to change tolerances and other settings? How long would one anticipate something like this to run? In addition, how can I (generally speaking) evaluate how close a given calculation is to finishing?


texts: Question about calculating enthalpy change

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

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

Both $\Delta H$'s given by the above formulas should be equivalent.
However, I found one special case that the above 2 formulas give 2 different results.
$$\ce{2 H+ + 2 e- → H2}$$
$$\Delta H = \sum \Delta H_\mathrm{F} \left( \text{products}\right)-\Delta H_\mathrm{F} \left( \text{reactants}\right)= 0-0=0$$
$$\Delta H = \left( \begin{array}{c} \text{total enthalpy of}\\ \text{bonds broken}\end{array}\right)-\left( \begin{array}{c} \text{total enthalpy of}\\ \text{bonds made}\end{array}\right)<0$$ because there is only bond formation, no bond break.
How to explain this difference? Can I say the heat is released during this process, because $$ \Delta H $$ is smaller than 0?


texts: Nomenclature of organic molecules with more than one functional group

texts:
I need some help naming compounds with more than one functional group based on their priority order. Here are some examples:

A 4-membered carbon chain with an aldehyde at one end and a ketone right next to the aldehyde
A 4-membered carbon chain with an aldehyde at one end, and the ketone and aldehyde having 1 carbon in between.
A 5-membered carbon chain with a $\ce{C=C}$ double bond at carbon number 2  and a $\ce{C#C}$ triple bond at $\ce{C}_4$ (maybe it is the reverse)

I think that for the one with a double bond and a triple bond, the triple bond gets higher priority and so it would be pent-4-en-2-yne but I am not sure about it.


texts: Which commonly available UV light source to use with fluorescein

texts: I want to start experimenting with fluorescein.  I have a 353 nm UV light source, but am thinking that it might be too short since it looks like peak excitation occurs at 494 nm.  So am I correct in assuming that I should buy light sources that emit light at around 494 nm (480 nm for example)?


texts: Volume required to dilute solution for a pH change

texts:
A $\pu{100 mL}$ solution of $\ce{NaOH}$ has a $\mathrm{pH}$ of $13$. What volume of water in $\pu{mL}$ must be added to change the $\mathrm{pH}$ to $11$?

My steps:

Begin by calculating conc. of $[\ce{OH-}]$ for $\mathrm{pH}~13$.
Find the moles by multiplying concentration and volume ($\pu{0.1 L}$)
Determine new concentration of $[\ce{OH-}]$ for $\mathrm{pH}~11$.
Use $\text{amount}/\text{new concentration}$ to find the total volume.
Use total volume ($\pu{100 mL}$) to find volume needed to be added.

The above doesn't produce the right answer, which is $\pu{9.900 mL}$. Can someone please fix my working out, or provide alternative steps to calculate this?


texts: Free rotation of sigma bonds; diastereomer formation; thermodynamic and kinetic products

texts:
For the reaction of 1,3-butadiene with DBr (D = heavy hydrogen), I found that several possible products could be formed.

Kinetic products

A pair of enantiomers is formed. One of the pi bonds attacks the heavy proton and the leaving group, bromide anion, comes back around to take care of the allylic carbocation. Because the bromide can attack from both above and below the plane of the carbocation, both enantiomers are formed.

Thermodynamic products

2) Now, because there is resonance, the carbocation possesses partial primary allylic carbocation character. As a result, bromide anion may also attack at a different position. This results in an internal alkene - the more stable alkene (the Zaitsev alkene).

Diastereomers are formed as well because single bonds can rotate, and the partial, terminal double bond can be "flipped" upward in the resonance depiction (I know that resonance depictions do not exist independently; hence "partial"). This allows the Z alkene to be formed in addition to the E alkene, as illustrated by my mechanism.

Questions

1) Are the products all valid and correctly categorized?

2) Is the E and Z isomer each produced, and in the way I think both are produced?


texts: How to make foggy and cloudy plastic fully transparent?

texts: I used sandpaper of different grits to sand the surface of plastic. The surface is smooth but it looks dull after sanding. I read that one could use toothpaste to remove the foggy look but it did not work. I also tried vinegar with baking soda. When the plastic was inside the vinegar+baking soda bath, it looked transparent and shinny. However, when I took it out to wash it with water to clean the smell, it looked shinny and transparent when being washed but it became foggy and cloudy again after washing. I put it back to vinegar+baking soda bath. It became transparent again but when I used a clean microfiber cloth to clean it, it became foggy again. Looks like some kind of thin film on it. Putting it in vinegar+backing soda bath for about 8 hours did not help. What caused the foggy/cloudy look? Would you please tell how to I make the plastic fully transparent?


texts: Is adsorption exothermic, and if so, why?

texts:
Why is adsorption exothermic?

The explanation given in my textbook is:

  For a process to be spontaneous, the thermodynamic requirement is that, at constant temperature and pressure, $\Delta G < 0$.
  As the entropy change of adsorption is negative ($\Delta S < 0$), the enthalpy change must therefore be negative ($\Delta H < 0$).
  If $\Delta H$ were to be positive, then $\Delta G = \Delta H - T\Delta S$ would always be positive.

It basically says adsorption is exothermic because $\Delta G$ has to be negative. Isn't there any other reason?


texts: Finding the pH of a mixture of weak acid and strong base

texts:
What are the steps we go about in finding the pH of a solution of strong base and weak acid?
Here is the question that I've been given

What is the pH of a solution made by mixing $\pu{50 ml}$ of $\pu{0.2 M}$ $\ce{NH4Cl}$ and $\pu{75 ml}$ of $\pu{0.1 M}$ $\ce{NaOH}$, when $\mathrm pK_\mathrm b(\ce{NH3}) = 4.74$?
A. 7.02
B. 13.0
C. 9.73
D. 6.31

What I did to solve it was to use the Henderson equation for buffers,
$$\begin{align}
\mathrm{pOH} &= \mathrm pK_\mathrm b + \log{\frac{[\text{salt}]}{[\text{base}]}} \\
&= 4.74 + \log{\left(\frac{0.2 \cdot 50}{0.1 \cdot 75}\right)} \\
&= 4.74 + \log{\frac{4}{3}} \\
&= 4.86
\end{align}$$
and thus $\mathrm{pH} = 14 - \mathrm{pOH} = 9.14.$
The correct answer is C. But on putting values I'm getting the wrong answer. Can you help me figure out why? Also, shouldn't the buffer solution have a common ion?


texts: If salt crystals make a cube shape, what is this 'X' marking?

texts:
I am an amateur, with very little professional chemistry knowledge. I was doing a demonstration / experiment with my 6 year old child.

We took very warm normal tap water, and dissolved into it a large pile of normal table salt. I didn't measure anything particularly, because I was just showing the basic concept of 'dissolving'. That's all. My kid was amazed to see the white pile of salt disappear visibly, but upon tasting the water understood what had happened.

Next we left the bowl up on a high shelf for 2 weeks, to let the water evaporate. This morning we took a look, and were rewarded by a dry bowl full of beautiful perfectly square salt crystals, many of them between 4-6mm in width.

That the crystals were perfect squares did not surprise me, as I have read that sodium and chlorine atoms form a cube shape at an atomic level.

But I could not answer the question about what the 'X' pattern marking was on each square. I have tried to attach photographs to show what I mean. The 'normal' picture is blurry, but if you look you can faintly see an 'X' on each crystal.

The other 2 pictures are each at 20x, using the Natural History Museum Pocket Microscope.

My question is, what explains those 'X' shapes? If possible I need to translate the explanation into 6-year-old talk :-)


texts: Does single-layered Aluminium Phosphide exist?

texts:
I'm currently working with the band structure of graphene and graphene-like compounds.

α-Boron Nitride (hexagonal, single layer) has many interesting properties. I was wondering if the next period analogue, a hexagonal single-layered Aluminium Phosphide existed. Wikipedia lists this compound, but it seems to only be found with a multilayered sphalerite structure.

Does an allotrope of AlP exist (in a stable state at normal conditions) where the structure is similar to graphene or silicene? If not, why?


texts: My textbook tells me the following structure is 2,2,5-trimethylpentane. I try to change the parent group in different ways so as to maximize the number of substituent groups, but I think the maximum number of substituent groups for any arrangement is 3 - so my answer is 2,2,4-trimethylpentane. Am I wrong in thinking this?


texts: Are any commercial plastics made from biomass/plant matter?

texts: Are any commercial plastics made from plant matter currently. I expect it can be done in a lab but I am wondering about cost competitive tonnage quantities.


texts: What the balanced chemical equation for the conversion of starch to dextrin by dry heating?

texts: This question is related to the toasting of bread. When we toast a slice of bread, the starch in it breaks down into dextrin. I want to know the balanced chemical equation for the process.


texts: Can molten aluminium be used to reduce iron oxide (rust) into iron?

texts:
Will surface rust on an iron crucible be converted if used to melt aluminium?

Can one convert bog/lake iron ore into iron using molten aluminium similar to the Thermite reaction?

Or perhaps the real question is what temperature would this occur at?

EDIT: I'm hoping one could use the molten aluminium instead of aluminium dust to achieve the same reaction as occurs in the Thermite process.  I know about Thermite steel rail and copper earth connection welding. My goal is to reduce rust to iron by sprinkling it (with attendant sparks) onto a molten aluminium surface. Will the temperature be too low in practice or will the iron oxidise or blow off before consolidating?  Trials today were inconclusive due to low temperature and small sample size.


texts: Excited helium gas from the colision of alpha particles with beta particles?

texts: As alpha particles are made out of 2 protons and 2 neutrons, they are the same as the helium atom with a +2 charge, but with a certain speed. The beta particles are made out of 1 electron at a certain speed. So, theoretically, "mixing" alpha particles with beta particles would create an excited helium atom, which then, would decay to a normal helium atom releasing the kinetic energy through gamma radiation, or simply light. Is this correct? If not, why?


texts: Can aged acetylcholinesterase be reactivated?

texts: it is a well-known fact that certain phosphorus compounds can inhibit the enzyme acetylcholinesterase, and that the treatment of poisoning with such compounds is administration of atropine and some kind of oxime-containing compound. This needs to be done quickly, since another reaction, called "Aging" usually takes place, whereby a part of the phosphorus compound that does not act as the initial leaving group is hydrolyzed off, leaving a negatively-charged phosphonate or phosphate, which forms a salt bridge with the protonated, positively-charged histidine residue at the active site of the enzyme. Aging renders AChE resistant to reactivation by oximes. Is it possible to somehow reactivate AChE that has aged?


texts: Calculating weight of soluble salt in a solution

texts:
I got a solution which density is $\pu{1.035 g mL-1}$ and it contains soluble salt $\ce{Ba(NO3)2}$ at concentration of $\pu{0.250 M}$. The teacher is asking from me to "clear" the solution from the $\ce{Ba^2+}$ ions by using a sedimentation with $\ce{PO4^3-}$ ions that the concentration of $\ce{Ba^2+}$ would be less than $\pu{7.00 ppb}$.

Then she is asking if its possible (well yes it is, but I don't know how to explain this though)? And, if it is possible, what would be the weight of the soluble salt $\ce{Na3PO4}$ that we need to put into a $\pu{50.0 mL}$ of the solution?

And I got the $K_\mathrm{sp}(\ce{Ba3(PO4)2}) = \pu{4.03e-25}$.

Now I probably started by making the right ions equation, which is:

$$\ce{2 Na3PO4 + 3 Ba(NO3)2 -> 6 NaNO3 + Ba3(PO4)2}$$

Then, I calculated the net mass of the solution by multiplying the given density  $\pu{1035 g L-1}$ by given Volume $\pu{0.05 L}$.

And finally I calculated the amount of $\ce{Ba(NO3)2}$ and of $\ce{Na3PO4}$ which are $\pu{0.0125 mol}$ and $\pu{0.0083 mol}$, respectively.

That is the point where I don't know how to mix all this information and to get the right answer.

The final answer: It's possible. If we will put more than $\pu{1.80 g}$ of $\ce{Na3PO4}$ to $\pu{50.0 mL}$ of the solution, the ion concentration of $\ce{Ba^2+}$ will be less than $\pu{7.0 ppb}$.


texts: How can I perform structure alignment on an inorganic species?

texts:
I'm attempting to perform atomistic optimal structure alignment on an inorganic species. Can anyone point me in the right direction to software or a technique for performing this?

There exists a wide range of structural alignment software, but this really appears to be geared towards aligning protein backbones, whereas I'm interested in aligning unlabelled Cartesian coordinates of small molecules.


texts: How does acetone help to make a liquid cleaner stronger?

texts:
Acetone, as a solvent, seems to behave somewhat different than other solvents. It seems to solve things other unpolar solvents do not.

For example, I have two cleaner sprays from the same brand, and the one with acetone seems to be "stronger" in some way. I think I have noticed that difference before elsewhere, so I assume at least part of what makes it stronger is the acetone.


texts: Predicting the vapor pressure of water ammonia solution

texts:
I am working on a project that involves the compressors for a vapor compression refrigeration cycle of R717 (ammonia) and came across something that has been boggling my mind a little bit for no good reason. I suspect there is water entering the system and making the compressor work harder than it needs to and thus causing higher energy costs. I was reading an article that stated

  For example, pure
  ammonia at -4°F (-20°C) has a saturation pressure of 12.9 psig (0.90 barg). An
  ammonia-water solution of 10% water and 90% ammonia by weight, at the same
  -4°F (-20°C) has a saturation pressure of 10.2 psig (0.72 barg). Therefore to
  maintain an evaporator temperature of -4°F (-20°C) in a system with 10% water
  contamination, the suction pressure would have to be run at 12.9 – 10.2 = 2.7 psi
  (0.18 bar) lower than if the water were not present.

Now I remember from thermodynamics that I can use Antoine's equation to determine the vapor pressure of a substance at a given temperature. I have gone to the NIST and obtained coefficients for water and ammonia. Problem is, at -4F, ammonia is a liquid, but water would be a solid. My issue is, how do I calculate the vapor pressure when, at the given temperature, one of the species is a solid?  Or is that not a concern, because according to the phase diagram, , the solution is a fluid assuming at most 20% water in the solution. If that is the case, the how would vapor pressure be calculated as the antoine's coefficients at only valid for liquid water about 0C? I think I am having a brain fart honestly, but maybe you all could help me out.


texts: How to calculate the bond energy of C-Cl?

texts:
$$\ce{C(s) + 2 Cl2 (g)  -> CCl4 (g)}$$
\begin{align}
\Delta H^\circ_\mathrm{f} (\ce{C(g)}) &= 121~\mathrm{kJ/mol}\\
\Delta H^\circ_\mathrm{f} (\ce{Cl(g)}) &= 716~\mathrm{kJ/mol}\\
\Delta H^\circ_\mathrm{f} (\ce{CCl4(g)}) &= -106.48~\mathrm{kJ/mol}\\
\end{align}

Basically I already answered this, but I was a bit confused about the result, cause I don't know if there is a bond that is negative, cause am familiar with the energy given to "dissociation" of a bond or the "formation" of it , but here it's given the energy to the formation of chlorine and carbon, I don't know if that's the same as the formation of the bond or not!

\begin{align}
\Delta H^\circ_\mathrm{f}(\ce{C-Cl}) &= \frac{\Delta H^\circ_\mathrm{f}(\ce{C(g)}) + 4 \Delta H^\circ_\mathrm{f}(\ce{Cl(g)}) - \Delta H^\circ_\mathrm{f}(\ce{CCl_4(g))}}{4} \\
\Delta H^\circ_\mathrm{f}(\ce{C-Cl}) &= \frac{121 + 4 \cdot 716 + 106.48}{4} \\
\Delta H^\circ_\mathrm{f}(\ce{C-Cl}) &= 772.87~\mathrm{kJ/mol}
\end{align}

Should I take the $\triangle H^\circ_\mathrm{f}(\ce{Cl(g)})$ same as $\triangle H^\circ_f(\ce{Cl-Cl})$? In that case I'm going to multiply it by $2$, not $4$.
Should the  $\Delta H^\circ_\mathrm{f}(\ce{C-Cl})$ be prefixed by a minus $-$ or a plus $+$, cause I don't know if it's an energy that is needed to formulate $\ce{CCl4}$? I'm not saying that the enthalpy of the bond should be negative, but the direction.


texts: Are salt substitutes good alternatives to sodium chloride?

texts: I bought a low salt Ketchup from Heinz and it says it uses ‘ALSOSALT’ substitute (potassium chloride). It says it does have 5 mg of sodium. Is potassium chloride (with possible additives) a good alternative to sodium chloride and does it not cause problems for the heart or general health?


texts: Do all chiral objects rotate the plane of polarization of EM waves? For example my hand is chiral, will it rotate the plane of polarization of EM waves of suitable wavelength?


texts: Do orbital models derive from the solution of the stationary Schrödinger equation?

texts: I know that hydrogen-like atomic orbitals can be seen as a solution of the stationary Schrödinger equation - but what about atoms with more electrons? As I am a pupil and quite uneducated about this subject, I would be very grateful for an answer that is easy to understand.


texts: Redox and acid-base reactions in planetary atmospheres

texts:
I'm a chemistry layperson looking for chemistry expertise regarding atmosphere composition.

Earth's atmosphere is oxidizing, but it was somewhat reducing in the distant past before photosynthetic life developed. Venus has an acidic atmosphere primarily composed of carbon dioxide which includes clouds of sulfuric acid. Some planetary bodies have reducing atmospheres containing hydrogen sulfide or carbon monoxide.

How do redox and acid-base reactions interact in the context of planetary atmosphere compositions? Specifically, what combinations of reducing/oxidizing and acidic/basic atmospheres are possible? Are there other planetary atmosphere types that should be considered when categorizing them?

Quick terminology question: Does it even make sense to refer to an atmosphere as acidic or basic?


texts: The relationships between n , T , P , V for a gas?

texts:
The symbols :

T : temperature //
V : volume //
P : pressure //
n : number of mole

what it is clearly known about the relationship between one another is :

P is inversely proportional to V ( from Boyle's law : PV=constant )

V is directly proportional to T ( from Charles's law : V/T=constant )

but the other ones I am not sure about them, So i might say :

P is inversely proportional to T

T is inversely proportional to n

p is directly proportional to n

What do you think?


texts: Unknown notation relating to stoichiometry

texts: I have never seen the highlighted symbol before. What is the name of the symbol itself, and what does it mean in this context?


texts: Rationalising the trend of standard electrode potentials between the +II and +III oxidation state of first-row transition metals

texts:
Trends in standard electrode potentials of d block elements:

  An examination ofthe $E^0 (\ce{M^3+}/\ce{M^2+})$ values (Table 8.2) shows the varying trends. The low value for Sc reflects the stability of $\ce{Sc^3+}$ which has a noble gas configuration. The highest value for Zn is due to the removal of an electron from the stable $\mathrm d^{10}$ configuration of $\ce{Zn^2+}$. The comparatively high value for Mn shows that $\ce{Mn^2+}\ (\mathrm d^5)$ is particularly stable, whereas comparatively low value for Fe shows the extra stability of $\ce{Fe^3+}\ (\mathrm d^5)$.The comparatively low value for V is related to the stability of $\ce{V^2+}$ half-filled $\mathrm{t_{2g}}$ level, Unit 9).

It says that low value of Sc is due to stability of $\ce{Sc^3+}$. At the same time, low value of V is due to stability of $\ce{V^2+}$.
Don't these statements contradict each other? If not, could someone please explain this paragraph in an easier way?
I m not able to understand it.


texts: What reaction occurs when etching copper to create circuit boards?

texts:
The components used for etching copper are acetic acid, hydrogen peroxide and sodium chloride. I think the equation may be similar to this:

$$\ce{2H3C2O2H + H2O2 + 2NaCl + Cu -> CuCl2 + 2H3C2O2Na + 2H2O}$$

Is this equation correct? There are a lot of bubbles created. What is the gas that is given off?


texts: Energy level of hybrid orbitals in the molecular orbital energy diagram

texts:
I would like to know what is the level of energy of a hybrid orbital?

For instance, lets consider the $\ce{N2}$ molecule. According to its geometry, we know that there is an orbital 2p and 2s that are going to form 2 sp orbitals.
 In the molecular orbital energy diagram, where should we place the these 2 sp orbitals? Would they be in the middle of a 2p and a 2s? And which p orbital do we take to take the middle ($p_x$,$p_y$,$p_z$, $\pi$ or $\sigma$?) Will the sp* be higher or lower that the $2p_x$ and $2p_y$?


texts: Why is oxygen oxidized with lead instead of being reduced?

texts:
Oxygen is more electro negative yet in the redox reaction

$$\ce{2PbO(s) -> 2Pb(s) + O2(g)}$$

my text book says lead is reduced and oxygen is oxidized. How can this be? It doesn't make sense to me. Oxygen is usually $2-$ while lead is usually $2+$.


texts: In a galvanic cell, why does an electrode with a higher potential "pull" the electrons from the electrode with a lower potential?

texts:
I'm doing Grade 12 Chemistry and I'm unsure of this, taking the hydrogen electorde as having a potential of 0 volts.

I'll use the copper-zinc cell as an example. Just let me know if I've got the full logic right:

Zinc has higher electronegativity, so due to the equilibrium $\ce{Zn <=> Zn^{2+} + 2e-}$, we have more charge building up in the Zinc electrode than in the Copper electrode. (Given both half-cells are of same concentration and in same temp)
We have a potential difference between the two electrodes. This means some charge from the Zinc electrode will move to the Copper electrode in such a way that both electrodes will momentarily have equal charges.
Since the charge in the Copper electrode has gone up, we have added electrons to the equilibrium reaction $\ce{Cu^{2+} + 2e- <=> Cu}$. We therefore create more copper.

Is this why an electrode with a higher potential will "pull" the electrons from the electrode with a lower potential?


texts: Magnesium shows an oxidation state of $+2$ and bismuth shows an oxidation state of $+3$. Both do not show a negative oxidation state. Then how is magnesium bismuthide ($\ce{Mg_{3}Bi_{2}}$) formed?


texts: Alloys/metallurgy : promising elements for for Sn-based solders

texts:
I am trying to research potential modifications to lead-free solders (intended to be used in electronics). Base alloy is eutectic $\ce{Bi_{58}Sn_{42}}$, and I am going to add various combinations of a bit of copper, silver, gold, platinum, gallium, lithium, and indium.

Is there something there which is known to not work? I am wondering this because I see that gold, platinum, gallium, and lithium are not typically used as dopants for electronic soldering alloys. Should I expect a lot of problems attributed to intermetallic compounds? (I know there are issues due to a Sn-Cu reaction, but nothing about the rest).

Is it theoretically possible to find a combination with significantly high copper content (> 10-20%) while still having low melting temperature (< 250 $^{\circ}\mathrm{C}$)?


texts: Why does the colour of gold sol change with particle size?

texts:
Regarding the colour of gold sol, my book says

Finest gold sol is red in colour; as the size of particles increases, it appears purple, then blue and finally golden.

This is the image I found on Wikipedia which portrays the same phenomenon.

The same page also discusses the effect of size etc. on the colour, but I don't understand exactly what's happening.
Why shouldn't the colour be the same for all sizes? Isn't it characteristic of the molecules which make the sol as the light absorbed and reflected depends on them?
Does this mean that when we break down any other thing to very small particles, it's sol will change in colour?


texts: Will an E2 reaction that has 2 potential products go faster than one that has 3 potential products? The specific question involves both molecules below reacting with methanol. I figured it's an E2 reaction (I hope I'm right) and the question is, which one will go faster?