texts: GAMESS(US) Polarizable Continuum Model frequency calculations are giving me what seems to be garbage

texts:
I'm trying to run Polarizable Continuum Model (PCM) calculations using the GAMESS(US) software. I'm not that well versed in what exactly these calculations are doing (beyond the whole, 'gas within a solvent cavity' explanation). So I will preface and say the calculations might be working and I am simply not understanding the results.

I am running a simple calculation just to start understanding PCM calculations, so I'm using this input:

! AutoGAMESS Version 1.1.8
!  by Brian C. Ferrari
!
 $CONTRL SCFTYP=RHF MULT=1 NPRINT=0 COORD=UNIQUE
 RUNTYP=HESSIAN ICUT=12 ITOL=25 DFTTYP=B3LYP
 MAXIT=200 QMTTOL=1E-7 ICHARG=0 ISPHER=1 $END
 $SYSTEM MWORDS=800 MEMDDI=800 $END
 $STATPT OPTTOL=1E-6 NSTEP=200 $END
 $PCM SOLVNT=CH3OH $END
 $FORCE METHOD=SEMINUM NVIB=2 PROJCT=.TRUE. $END
 $SCF DIRSCF=.TRUE. FDIFF=.FALSE. CONV=1d-7 $END
 $DFT JANS=2 $END
 $BASIS GBASIS=CCT $END
 $DATA
AutoGAMESS COx Energetics
Cnv 4,

 C           6.0   0.0000000000   0.0000000000   0.5267400687
 O           8.0   0.0000000000   0.0000000000  -0.5996000687
$END

The calculation terminates normally but the results it prints out are the following:

  MODE FREQ(CM**-1)  SYMMETRY  RED. MASS  IR INTENS.
     1       0.000    A       12.000000    0.001636
     2       0.000    A       12.000000    0.001636
     3       0.000    A       12.000000    1.444876
     4       0.000    A       15.994910    0.001228
     5       0.000    A       15.994910    0.001227
     6       0.000    A       15.994910    1.084002

This seems like garbage to me, since the frequencies are all 0 but there are some IR intensities. Which leaves me wondering what is going wrong to cause this error in the calculation? What should I change in the input file?


texts: protecting contact between aluminium and copper wires

texts:
The quarters in which I live has both aluminum and copper household wiring. This results in corrosion of the contacts and can lead to sparking, overheating, and even fire.

Is there any way to inhibit the corrosion (if not stopping it completely), except for changing the whole wiring?


texts: Is there a way to export detailed data about atom connectivity, dihedral angle, etc from GaussView?

texts: As far as I know, opening the .com files as .txt files (with a text editor like simple notepad) yields a nicely formatted table of (atom) (x) (y) (z) values that can then be worked with. The problem is that this data has no information about what atom is connected to what. But within the actual Gaussview software, there seems to be a data set with more detailed information. Is there any way to easily extract that data via code?


texts:
I am doing a science fair experiment about Microbial Fuel Cells and was wondering how exactly do they work?

I know the basics, that they work similarly to a normal Fuel Cell through oxidation and reduction but am still a little unclear on the full details.


texts: Why does my rainwater turn yellow if I increase the pH to 7?

texts:
My rainwater is colourless when collected, but if I add a small amount of sodium hydroxide to increase the pH to about 7, after a few days it goes yellow.
The colour change happens more quickly if I increase the temperature.
This change to yellow is accompanied by the disappearance of any dinoflagellates or cryptophytes which were living in the water (determined by 300X microscope.)
The rainwater appears to contain a significant amount of dissolved organic carbon.
The rainwater is collected from the PVC roof of my shed in a covered plastic container which I have recently cleaned.
The pH of the rainwater is between 5.4 and 6 when collected (the best I can do with bromothymol blue indicator solution and narrow-range indicator paper.)
I am located in the south-west of England about one mile from the sea.


texts:
I have been reading some literature on molecular energy prediction using machine learning techniques and I have noticed that one of the input parameters in many of the available models is "chirality". In these works "chirality" is defined as an atom feature. Meaning that for every atom in the molecule, a one-hot or null vector is used to assign R/S to the atom. As far as I understand, chirality is a molecular property and only the atom which is the chiral center can be assigned R/S.

I was wondering if my understanding is correct and if not, what am I missing. Thanks!

PS: One such a paper is this.


texts: Calcium carbonate and hydrogen phosphate producing calcium phosphate, carbon dioxide, and water

texts: How does the balanced reaction look for these compounds? I found that phosphoric acid instead of hydrogen phosphate creates a much easier problem, but the teacher said hydrogen phosphate and I can't seem to balance it.


texts: What is the most complex molecule we can manufacture without the help of proteins? (soft queston)

texts:
What is the most complex molecule we can manufacture without the help of proteins?

This isn't motivated by anything but curiosity about the state of chemical engineering. I realize “complexity” is a loaded term, so I'll defer to the judgment of the respondent: number of molecules, complex arrangement of bonds, or whatever other measure might be appropriate.


texts: It seems to me that CO2, since it can be linearly rotated around the z-axis without change of shape, ought to be in the C∞v point group.  However, in all the character tables I can find, it's listed as a D∞h.  What's the difference between these two, and why does CO2 fall in the D∞h and not the C∞v?


texts:
By just freezing water and using an optical microscope, can I observe water crystals?

Or do I have to use a special light to see?


texts:
I have the following problem:

The following reversible system is at equilibrium:
$$\ce{P_{4(s)} + 6Cl_{2(g)} <=> 4PCl_{3(l)}} $$
What happens with the equilibrium if $\ce{P_4}$ is added.

Normally, by applying Le Chatelier's principle the equilibrium should be shifted to the right, however, for some reason this does not apply to the above equation.
Why does increasing or decreasing the quantities does not change the equilibrium in the above system?


texts:
So I was checking the structure of nitric acid in Wikipedia, however I couldn't quite fathom why it looked like that because it seemed to contradict the following statement:

  A Lewis structure with small or no formal charges is preferred over a Lewis structure with large formal charges.

If we draw it like the one on the right, we get rid of formal charges and the structure is said to be more "stable". Why does this concept not work in this case?


texts: Predicting Ka/Kb values using values for solubility in water

texts:
Given that $K_\mathrm{a}$ values are determined by the position of equilibrium for a species such as $\ce{HCl}$ where $K_\mathrm{a} = \ce{\frac{{[H^{+}]}{[Cl^{-}]}}{[HCl]}}$, I was wondering whether it would be possible to work out $K_\mathrm{a}$ values using 'Solubility in Water' values.

For example: $\ce{HCl}$ has a solubility of $\pu{720g/L}$ in water at 20 degrees Celsius. Is this possible or is there no direct correlation between solubility in water and $K_\mathrm{a}$?


texts: Why does water favour nucleophilic substitution over elimination?

texts:
The two broad ways a halogen can leave a haloalkane are nucleophilic substitution and elimination reactions.

I was told that elimination reactions (that form a double bond as a $H^+$ is also removed) do not occur when the haloalkane is dissolved in water; here nucleophilic substitution (anion replaces halogen only) is favoured.

Why is this? I guess it's not just water - what are the general conditions (including type of solvent) that prefer nucleophilic substitution over elimination, and vice-versa?

I understand there are different variants of both elimination and substitution ($S_N1, S_N2, E1,E2$); are any of them more prone to occur than others of the same type in water?


texts: Is there a way to faciliate remembering which are alpha/beta hemiacetals of sugars?

texts:
I understood the concept of hemiacetals quite well, but have considerable trouble remembering which are called $\alpha$ or $\beta$ respectively.
Is there some concept/mnemonic/common reaction/something else to faciliate remembering this convention?


texts: Why is the Haber process carried out at such high temperatures?

texts:
On a large scale, ammonia is prepared via the Haber process:

$$\ce{N2(g) + 3H2(g)->2NH3(g)} \qquad \Delta _\mathrm{f}H^\circ = -46.1~\mathrm{kJ \cdot mol^{-1}}$$

The optimum conditions for the productions of ammonia are a pressure of $200~\mathrm{atm}$ and a temperature of about $700~\mathrm{K}$.

The process obviously is exothermic and $700~\mathrm{K}$ is, by no means, a low temperature. Shouldn't the temperature be much lower for optimum production of ammonia?


texts: Calculating change in state function following different paths

texts:
in thermodynamics, we learn that change in state function is independent of the path/process, and thus we can conveniently pick any arbitrary path that allows easier calculation. I'm TA'ing a class and found that it would be great to actually show students an example where that a simpler path can indeed be constructed to calculate the change of state function. However, I feel that there must be some blind spot that I myself am struggling with. And would like to get everyone's feedback.
Example and detail
We are asked to calculate $\Delta H$ for an isochoric process where a known amount of energy is transferred into the system (of a monatomic ideal gas) as heat. Assuming only P-V work is allowed in the system.
I can first calculate change of internal energy ($\Delta U$) using the first law, and subsequently $\Delta T$ with the known heat capacity (over constant volume) $c_V = \frac{3R}{2}$. Then to calcuate $\Delta H$, I'll follow an isobaric process instead (with $c_P = \frac{5R}{2}$), but it will give the same result. Here's the detail:

$w = -\int_i^f P_\text{ext} dV = 0$ (no work is done at constant volume)

$\Delta U = w + q = 0 + q = q$

$\Delta U (= q_V) = n c_V \Delta T \implies \Delta T = \frac{\Delta U}{n c_V} = \frac{q}{n c_V}$

$\Delta H = q_P = n c_P \Delta T = n c_P \frac{q}{n c_V} = \frac{c_P}{c_V} q$

Question
My question - under the context of this example - is how to make up a path connecting the same endpoints (the initial and final states) that is under constant pressure?
Without loss of generality, assume that $q > 0$, and thus the temperature at the end increases as the internal energy increases (no work is done due to the constant volume constraint). This suggests that the pressure also increases. But I just said that I'd like to construct an isobaric path that connects the initial and final state..., which now seems to be contradicting the fact.
My thought is - that instead of a single isobaric path (which connects the initial state and potentially an intermediate state), maybe I need another segment that connects the intermediate state and the final state? Such that overall the volume stays the same? If this is the approach, what would the strategy be for picking the intermediate state and the two segments making up the simpler path?
Would the following work?

1st segment: isobaric expansion to an intermediate state whose temperature is the same as the final state. The relevant heat is $q_P$ which will contribute to the overall change in enthalpy with its contribution $\Delta H_1 = q_P$.

2nd segment: isothermal compression to the final state (i.e., need to volume to go back to its initial/final state volume). For this part - there is going to be additional heat and work involved, but internal energy and enthalpy should remain unchanged (as same as the intermediate state), resulting in $\Delta H_2 = 0$.

Overall, $\Delta H = \Delta H_1 + \Delta H_2 = \Delta H_1 = q_P$.

I'm not very sure about this as it invokes that enthalpy change is zero for an isothermal process -- which I don't know if it will hold for non-ideal gas? And if not - this suggests my proposal doesn't work universally...
[Edits for fixing typo]


texts: Completely chemically inert metal alloy?

texts:
Background:
I was a chemistry major and have recently started watching this series of videos by NurdRage.
I learned that Platinum dissolves in Aqua Regia but Ruthenium is only attacked by high temperature halogens and some alkalis.
Question:
Would a Ruthenium and Platinum alloy be resistant to both acid and alkali?
But more importantly, is there any alloy or pure metal that is completely chemically inert to every strong oxidizing reagent? Is there any research about the most chemically inert metal alloys?


texts:
This link has a short paragraph on the very first page, which says: "There are two useful criteria to evaluate the presence and the strength of a H-bond. The first is to look at the distance between the H and the A atom, which should be shorter than the sum of their Van der Waals radii. A second method suggests to evaluate the angle formed by X-H∙∙∙A, centered on the H atom: the closer this angle is to 180°, the stronger the H-bond is"

I wish to understand why the part in bold is true, that is, what is the angle dependence (qualitative or quantitative) of the strength of hydrogen bonds.

To add to the above discussion, in an introductory biology course at university, we were also given the following example -

Well, once again, why is it so?

I did some research, didn't really find much, but came across an interesting paper that may be worth a read if anyone's really interested. Attaching it here!

Thanks in advance!


texts: Differences in AChE inhibition kinetics between paraoxon and methyl paraoxon

texts:
According to literature, dimethyl paraoxon has a reaction rate constant for the aging (spontaneous dealkylation) of acetylcholinesterase of $\pu{0.186 h-1}$, a spontaneous reactivation rate constant of $\pu{1.01 h-1}$, and an inhibition reaction rate constant of $\pu{1.2 \times 10^6 M-1 min-1}$, compared to $\pu{0.022 h-1}$, $\pu{0.022 h-1}$, and $\pu{2.2 \times 10^6 M-1 min-1}$, respectively for paraoxon.[1] It has been shown that the process of aging, at least for the nerve agent tabun, proceeds through cleavage of the $\ce{O-C}$ bond [2], which would presumably mean that a carbocation is generated as an intermediate, and thus, ethyl breakage, rather than methyl, should be more favorable. However, as the referenced paper shows, this is not the case, and methyl paraoxon, rather than paraoxon (with ethyl groups), ages more rapidly, and is also more susceptible to spontaneous reactivation. Furthermore, paraoxon (with ethyl groups) also has a higher inhibition rate constant. Why is this so?
References:
[1] Franz Worek, Horst Thiermann, Ladislaus Szinicz, Peter Eyer, "Kinetic analysis of interactions between human acetylcholinesterase, structurally different organophosphorus compounds and oximes," Biochemical Pharmacology 2004, 68(11), 2237–2248 (doi: https://doi.org/10.1016/j.bcp.2004.07.038).
[2] Eugénie Carletti, He Li, Bin Li, Fredrik Ekström, Yvain Nicolet, Mélanie Loiodice, Emilie Gillon, Marie T. Froment, Oksana Lockridge, Lawrence M. Schopfer, Patrick Masson, Florian Nachon, "Aging of Cholinesterases Phosphylated by Tabun Proceeds through O-Dealkylation," Journal of the American Chemical Society 2008, 130(47), 16011–16020 (doi: https://doi.org/10.1021/ja804941z)


texts: What type of polyester is most commonly used for clothing?

texts:
Many polymers have the name of the monomer in their names, e.g. polyethylene, polyvinyl chloride, polypropylene, polystyrene etc. But the ester in polyester refers to a group of chemicals (having an hydroxyl group replaced by an alkoxy group1) rather than a single chemical compound.

This article from Wikipedia states that polyethylene terephthalate (PET or PETE) is the most common type of polyester. PET is the plastic from which almost all plastic soda and beverage bottles are made. This leads me to wonder if the polyester from which clothes are commonly made are PET, and if not, what types of other polyesters (e.g. polyglycolide, polycaprolactone, polyethylene adipate, polybutylene succinate, etc.) clothes may be made from.I'm aware that most plastics can be stretched into long thin filaments/strands and wound into threads in a process similar to how natural-fiber threads are made. My question is specifically whether or not PET is commonly used as the polyester in clothes, and if not, what is? I've done some Google searches but can't find any references; maybe I just haven't gotten the search string right. Thanks.

https://en.wikipedia.org/wiki/Ester


texts:
I am an electrician apprentice in charge of a large number of pH-sensors/transmitters at a power plant and chemical plant.
I do all the pH-instrumentation related maintenance, calibration, adjustments etc.
By studying pH measurements I have learned about the Nernst equation. The transmitter is able to (via an inbuild Pt1000 sensor) automatically keep the temperature variable in the Nernst equation constantly updated.
However, I have also learned that pH bear no meaning unless a temperature of the measured medium is specified. The transmitter is ALSO able to compensate for this variability, however. This is done by heating up a sample of the process medium and noting down the pH difference at various temperatures. This information can be plotted into a matrix in the transmitter.
HOWEVER, since the process medium composition is ever changing at the plant I work at (waste incineration) this matrix can't be made.
Seeing that many of the proces temperatures at the plant are anywhere between 40 and 80 degree celcius, how large of a discrepancy am I looking at? I know that both chemical composition and temperatures dertermine how much, but realistically, what are we talking about? 0,1 difference in pH? 0,5 difference? More? Worst case? Best case?
Thanks in advance.


texts:
The title says it all.

I had this question when helping someone with their high-school chemistry homework. What are the reasons that someone would use an (from my point of view) obfuscated notation?


texts: Slope ≠ 1 in Henderson-Hasselbalch graph for determination of pKa

texts:
The $\mathrm{p}K_\mathrm{a}$ of indicators can be determined via plotting a graph of $\log \left(\frac{\ce{In-}}{\ce{HIn}}\right)$  vs $\mathrm{pH}$ with the help of a spectrophotometer, from the equation $\log \left(\frac{\ce{In-}}{\ce{HIn}}\right) = \mathrm{pH} - \mathrm{p}K_\mathrm{a}$.
From this, the graph should have a gradient of 1, and $x$-intercept = -($y$-intercept) = $\mathrm{p}K_\mathrm{a}$. However, my graph has a slope of ~0.8 which means my $x$-intercept ≠ -($y$-intercept) so which value do I use as my calculated $\mathrm{p}K_\mathrm{a}$?
From the papers I've read, most if not all of them use the intercept with the $\mathrm{pH}$ axis instead of the $\log \left(\frac{\ce{In-}}{\ce{HIn}}\right)$  axis in this situation, why is this?


texts: Is there a formula to determine the total number of constitutional isomers?

texts:
Is there a trick or a formula that given a molecular formula, allows you to know exactly how many constitutional isomers can be formed with that many atoms? Or is it more of a trial-and-error technique?

I'm looking for something along the lines of $2^n$ of maximum number of possible stereo-isomers, where n is the number of stereogenic centers present in a compound.


texts:
How to balance the following disproportionation reaction
 $$\ce {XeF2 + H2O → Xe + XeO3 + HF + O2} $$
 My attempt: I tried by making total number of reductions equal to total number of oxidation but I couldn't do because Xe is both oxidised and reduced also the solvent is water so what should I do to balance  protons and oxygen on both sides?.  Please help by solving it on the basis of same procedure that is making oxidation equal to reduction


texts: Does the acid strength of hydrochloric and hydrofluoric acid correlate with the electronegativity of the halides?

texts:
Is this statement true or false?

  HCl is a stronger acid than HF because fluorine is more electronegative than chlorine.

I'm thinking this is true, because since fluorine is more electronegative than chlorine, it has  a higher ionic energy and therefore a stronger bond between hydrogen than chlorine does with hydrogen. In result, leading HCl to dissociate  more easily. Can you please clarify.


texts: A 1.00 L gas at 100 °C and 500 Torr contains 70.0 % He and 30.0 % Ne by mass. What is the partial pressure of He?

texts:
A $1.00~\mathrm{L}$ gas at $100~^\circ\mathrm{C}$ and $500~\mathrm{Torr}$ contains $70.0\ \%~\ce{He}$ and $30.0\ \%~\ce{Ne}$ by mass. What is the partial pressure of $\ce{He}$?

My answer is $350~\mathrm{Torr}$ whereas the correct answer is $421~\mathrm{Torr}$.

Here is my solution (source; commas , should be points .; I used to write it this way.)

$$\begin{aligned}
  n_\mathrm{total} &= \frac{pV}{RT} = \frac{(1\ \mathrm l)(0.652\ \mathrm{atm})}{(0.082\ \mathrm{l\ atm\ K^{-1}\ mol^{-1}})(373\ \mathrm K)}=0.0215~\mathrm{mol}\\
  70\ \%~\ce{He} &\implies (70\ \%)(0.0215\ \mathrm{mol}) = 0.0151~\mathrm{mol}~\ce{He}\\
  p_\ce{He} &= \frac{nRT}{V}\\
            &= \frac{(0.0151\ \mathrm{mol})(0.082\ \mathrm{l\ atm\ K^{-1}\ mol^{-1}})(373\ \mathrm K)}{1\ \mathrm l} = 0.460~\mathrm{atm}\end{aligned}$$

$$0.460~\mathrm{atm}\cdot\frac{101325~\mathrm{Pa}}{1~\mathrm{atm}}\cdot\frac{1~\mathrm{Torr}}{133.322~\mathrm{Pa}}\approx 350~\mathrm{Torr}$$


texts: Shortcuts for finding geometrical isomers

texts:
Our teacher provides us extra questions for pratice, so one of the questions was :-

Find number of products if following are reacted with excess $\ce{NH2OH}$ (hydroxyl amine):
Cyclohex -
(i) 1,4-dione
(ii) 1,3-dione
(iii) 1,2-dione
(iv) 1,2,3 trione
(v) 1,2,4-trione
(vi) 1,3,5-trione  and
(vii) cyclobut-1,2,3,4-tetraone

To solve this, our teacher told us replace each $\ce{=O}$ group by 1 $\ce{-CH3}$ and 1 $\ce{-H}$ , then find the number of stereoisomers (including enantiomers) of the resultant compound, which is the answer.(if you actually count it's tough to visualize the lone pair and $\ce{-OH}$ bond and it gets long).
I have cross-checked , the answers pretty much match. So my doubt is, is this trick always right and if yes then please prove it. I would also be content if you can provide any links, if the question has already been answered.

I had another doubt, about another trick my teacher told us about. Let's say there's a compound with $n$ carbon atoms forming a closed ring of all $n$ carbons. At each carbon, out of 2 $\ce{-H}$ , 1 $\ce{-H}$ is replaced by $\ce{-Cl}$ (chlorine). The trick if $n$ is odd ,the number of geometrical isomers of the compound is $2^{(\frac{n-1}{2})}$ and if $n$ is even then the number of geometrical isomers is $2^{(\frac{n}{2})}$. Please prove this also.
Thank you in advance.


texts: Why does bonding in T.M complexes get stronger down the group but bonding in p-block elements gets weaker?

texts:
In the p-block, it’s a well-known general trend that down the group, the homonuclear diatomic bond dissociation energies decrease (generally). E.g in group 14:
C-C —> 607 kJ/mol
Si-Si —> 327 kJ/mol
Ge-Ge —> 274 kJ/mol
(Source: https://labs.chem.ucsb.edu/zakarian/armen/11---bonddissociationenergy.pdf)
The common explanation of this trend is that as the orbitals increase in size, 2p —> 3p —> 4p, they become more diffuse and worse orbital overlap is achieved, leading to a weaker bond.
However in T.M complexes it seems like the reverse is true. Complexes of the 4d and 5d metals are more likely to be low-spin, owing to the large splitting parameter achieved by stronger bonding to the ligands. This would suggest more effective overlap of 4d and 5d orbitals with the ligands than 3d, even if the ligands themselves are 2p atoms.
So my question is, why does orbital overlap seem to be more effective down the group in d-block elements, than in p-block elements, where orbital overlap clearly worsens?


texts: Searching for a solvent with a low carbon dioxide solubility

texts:
I would like to use a liquid solvent for some experimentation with a carbon dioxide solubility as low as possible under usual pressure and temperature conditions (say, $\pu{1 atm}$ and $\pu{293 K}$).

Until then, I was unable to find much information on the topic:

A study of $\ce{CO2}$ solubility in water and seawater by Weiss [1], indicating that $\ce{CO2}$ is less soluble in saline water than in pure water.
Publications concerning several organic solvent (acetone, cyclohexane, ethanol, methanol, etc.), a sum-up in IUPAC SDS Vol 50 [2]. To the naked eye, it seems that all of them can dissolve much more $\ce{CO2}$ than water, being poor candidates to answer my needs.
Publications concerning olive, linseed or other origin oils (see Simon and Gutknecht [3] for instance). However such fats seems to also have a higher solubility coefficient than water.

I do not know if such liquid does exist, but it would be great. Up to now, my best candidate is salty water.

References

Weiss, R. F. Carbon Dioxide in Water and Seawater: The Solubility of a Non-Ideal Gas. Marine Chemistry 1974, 2 (3), 203–215. https://doi.org/10/cb6n2j.
Carbon Dioxide in Non-Aqueous Solvents at Pressures Less than 200 kPa; Fogg, P. G., Clever, H. L., Eds.; Solubility data series; Pergamon Press: Oxford, 1992. ISBN 978-0-08-040495-0. PDF
Simon, S. A.; Gutknecht, J. Solubility of Carbon Dioxide in Lipid Bilayer Membranes and Organic Solvents. Biochimica et Biophysica Acta (BBA) - Biomembranes 1980, 596 (3), 352–358. https://doi.org/10/bj647m.

Update

I understand the "like dissolves the like"[1] rule of thumb so that a highly polar solvent would be the worst for a non-polar molecule such as $\ce{CO2}$. Water as a solvent would then be the best choice (possibly salted to further reduce its $\ce{CO2}$ solubility) for my needs.

But as Rolf pointed out, the dissociation of $\ce{CO2}$ into carbonate ions also happens and might increase its solubility. For such reasons an aprotic solvent could be useful.

However, when comparing between water (molar fraction 0.00061) which is a strongly polar (dielectric constant: 80 and dipole moment 1.85$~$D) but protic solvent and dimethyl sulfoxide (molar fraction 0.0091[2]) which is also polar (dielectric constant: 47 and dipole moment 3.96$~$D) but aprotic solvent, dimethyl sulfoxide as a higher solubility for carbon dioxide than water.

What can be the reasons for such unexpected outcome? Are my reasonings and assumptions correct or am I flawed in my thinkings?

References

Polar Protic? Polar Aprotic? Nonpolar? All About Solvents. - Master Organic Chemistry. https://www.masterorganicchemistry.com/2012/04/27/polar-protic-polar-aprotic-nonpolar-all-about-solvents/
Li Hua & Chen Wanren, 2005, Solubility of dilute SO2 and CO2 in dimethyl sulfoxide, Physics and Chemistry of Liquids, 43:3, 289-298, DOI: 10.1080/00319100500083583


texts:
I have been searching for the mechanism of the Mozingo reduction on Google but I haven't found anything relevant.

Is the mechanism known? If so, what is it; if not, what hypothetical mechanisms can we consider?


texts: How to use anodic and cathodic overpotentials to calculate electrolytic energy efficiency?

texts:
I am trying to calculate the energy efficiency for $\ce{CO2}$ reduction to formate, coupled to water oxidation based on literature data.
$$\ce{CO2 + 2e- + 2H+ -> HCOOH}$$
$$\ce{H2O -> 2H+ + 1/2O2 + 2e-}$$
I hope someone can help me to understand how to combine the information that is presented in the papers so I can calculate an overall energy efficiency of the reaction.
E.g. things that are given:

cathodic overpotential
anodic overpotential

The energy efficiency should eventually be equivalent to
$\mathrm{EE = \frac{Combustion\;energy\;of\;Formate}{Invested\;electrical\;energy}}$


texts:
Is this bond cleavage of cyclopentadienone correct?

The ring becomes aromatic and stability "should" increase. But my book and data from experiments suggest that the molecule isn't that polar as it would have been from this cleavage. Why isn't this cleavage favorable?
Doesn't aromaticity counter the appearance of a positive charge on oxygen?


texts: Which is More Stable with Boranes: Amines or Phosphines?

texts:
Given borane's ($\ce{BH3}$) LUMO, which of these Lewis bases would have a more stabilizing interaction?  In acid bases that means the higher HOMO and lower LUMO equals a stronger dative bond I believe.

So which would have a stronger interaction (greater net stabilization) with borane, trimethylphosphine or trimethylamine:

$$\ce{P(CH3)3 ~vs~ N(CH3)3}$$

Phosphorus is less EN and it's electrons reside in a higher energy 3p orbital, but doesn't it compensate for this by placing the electron pair an orbital with more "s" character? Also carbon is more EN than phosphorous drawing some strain.

I would say trimethylphosphine has the HOMO just because of it's higher orbitals and lower overall EN making donating a pair of electrons more favorable.

Am I right?


texts: Realistic chemical spill accident in high school chemistry class

texts:
In a story I'm writing, a teenager spills chemicals on herself in a high school chemistry class, causing her to be put under the safety shower. The spill destroys her clothes and causes minor burns. I would like this to be realistic and since I know nothing about chemistry, I have two questions:

Is there a chemical used in high school chemistry that when spilled could cause this situation to occur?
If so, do you know of an experiment that would use that chemical?


texts: Aqueous magnesium bicarbonate when evaporated decomposes into magnesium carbonate. Is that reaction reversible by dissolving the carbonate in soda water?


texts: Why does the water dissociation constant Kw remains constant?

texts:
At $\pu{25 ^\circ C}$ at equilibrium the value of $K_\mathrm{w}$ is $\pu{1\times 10^{-14} M}$ and the concentration of $\ce{H+}$ and $\ce{OH-}$ is equal i.e. $\pu{1\times 10^{-7} M}$.
Now if we add $\ce{HCl}$ to it the $\ce{HCl}$ will form $\ce{H3O+}$ and so the concentration of $\ce{H+}$ increases and so the equilibrium shifts towards the left to counteract the changes. As a result the concentration of $\ce{OH-}$ decreases but why does still the $K_\mathrm{w}$ stays the same. If we add too much $\ce{HCl}$ such as 1 mole then we know it will completely dissociate and would form $\ce{H3O+}$ whose concentration would be $\pu{1 M}$.
So now what will happen to $K_\mathrm{w}$? Does it still remains constant but why? Does still the concentration of $\ce{H+}$ can not rise above $1\times 10^{-14}$ but why?


texts: How to Find the Mass of an Individual Element in a Compound/Molecule

texts: What is the procedure/math for finding the mass of a specific element in a substance? For instance, how many grams of Oxygen are in 6.8 grams of Epinephrine (Adrenaline)?


texts: What is the reason behind choosing the specific elements used for the synthesis of heavier elements?

texts:
The following has been derived from the wiki page "Extended periodic table" and is one of the many examples d or f block elements being used in synthesizing new heavier elements (or at least this is the pattern I figured out by searching many other examples of the nuclear reactants in the way to synthesize heavy elements):

  Attempts to synthesize still undiscovered elements:

  \begin{align}
\ce{^254_99Es + ^48_20Ca &-> ^302_119Uue^*} \\
\ce{^249_97Bk + ^50_22Ti &-> ^295_119Uue + 4 ^1_0n} \\
\ce{^{nat}_68Er + ^136_54Xe &-> ^{298,300,302,303,304,306}Ubb^* -> no atoms} \\
\ce{^238_92U + ^66_30Zn &-> ^304_122Ubb^* -> no atoms}
\end{align}

The question is, why is it like this? How did the scientists reached an agreement on which elements to collide? Was it anything especial about those atoms?

P. S. If you are sure that there is an exception (exceptions omit rules; at least in this case), your answer will be accepted.


texts: What is the bonding type in hydrides of group 2 elements?

texts: In one of my MCQ questions, there was a statement saying all group 2 elements form covalent hydroxides. I know it is incorrect. I know that $\ce{BeH2}$ is a covalent hydride. What about the rest? Are all of them metallic hydrides? Is it true that metallic hydrides produce the hydroxide and give off $\ce{H2}$ with water?


texts: Does increasing the concentration of the anode electrolyte in a galvanic cell increase or decrease the voltage produced

texts:
Im in kind of a pickle here. I am using nernst equations to calculate the theoretical voltage produced for different concentrations of $\ce{Al(NO3)3}$.

Reaction: $$\ce{2Al(s) + 3Pb^{2+}(aq)⟶2Al^{3+}(aq) + 3Pb(s)}$$

Electrolytes are $\ce{Al(NO3)3}$ and $\ce{Pb(NO3)2}$.

I am using the Nernst equation $$E_{cell}=E^0-\frac{RT}{nF}\mathrm{ln}(Q)$$  and have the following calculation: $$E_{cell}=1.53-\frac{(8.314×293.7)}{(6×96500)}×\mathrm{ln}\left(\frac{(.01)^2}{(0.1)^3} \right)$$

where $Q=[Al^{3+}]^2/[Pb^{2+}]^3$   is the ratio (products)/(reactants).

I am finding that using the Nernst equation, an increase in the concentration of $\ce{Al(NO3)3}$ leads to a decrease in voltage whereas according to my practical data im finding an increase in voltage.

Also, according to this an increase in concentration should lead to an increase in voltage.

Can anybody tell me what im doing wrong here.

Any help would be appreciated!


texts: i have a solution of silver nitrate at 1M. the aim of my experiment is to determine in 40 mins, how much Ag will be deposited. Should i use copper or graphite electrodes.


texts:
I've read that the oxygen atom in water is $\mathrm{sp^2}$ hybridized, such that one of the oxygen lone pairs should be in an $\mathrm{sp^2}$ orbital and the other should be in a pure p atomic orbital.

First, am I correct about the lone pairs being non-equivalent?

Second, if so, does this have any significance in actual physical systems (i.e. is it a measurable phenomenon), and what is the approximate energy difference between the pairs of electrons?

Lastly, if it turns out the lone pairs are actually inequivalent, can this be reconciled with the traditional explanation (due to VSEPR theory) that oxygen is $\mathrm{sp^3}$ and the lone pairs are equivalent?


texts: What exactly is the use of photographic films in cameras? How are the pictures generated?

texts:
By definition:

  Photographic film is a strip or sheet of transparent plastic film
  base coated on one side with a gelatin emulsion containing microscopically small light-sensitive silver halide crystals. The
  sizes and other characteristics of the crystals determine the
  sensitivity, contrast and resolution of the film.

But how exactly is a photographic film utilized in a camera?

I know that it has a sort of a silver coating. But how does it work? I read the Wikipedia article but found it a bit difficult to understand.


texts: What has old Potassium metabisulfite turned into?

texts:
I found a glass jar labeled potassium metabisulfite in my abandoned photo lab.
The jar has been standing with a loosely fitting lid for thirty years in a cool and dry place.

The jar contains a dry substance now like matte flakes. The substance does not react visibly to hydrochloric acid and it does not smell of sulfur dioxide.

What substance has the potassium metabisulfite turned into? Just curious.

EDIT. The substance does not dissolve visibly in cold or boiling water. A few flakes poured in water remain on the bottom seemingly unaltered.

MORE EDIT. When heated to red heat in a test tube, it does not melt, the coarse powder is not sintered. No water is given off. Some sulfur is sublimated, a yellow deposit in the cold part of the test tube and a smell of sulfur. Not much sulfur is given off, the volume of the original substance is not visibly altered.


texts:
I tried to make a cannabis infused e-liquid. I made a tincture with marijuana and vegetable glycerin, but it became to thick so a mixed in more propylene glycol than I'd originally planned. Now the e-liquid is to weak, not enough THC per milliliter.

My question is: can I just heat up the e-liquid to 115-123 degrees celsius and let the glycol evaporate over a long time, or is that temperature too low? I don't want to destroy the psychoactive chemicals in the e-liquid.

Best wishes.


texts: Taking Glycine and aspartic acid. As both the amino acids are fully protonated at pH 0 ad pH 1, how does the peptide bond form? Is it a two step mechanism where the OH from an alpha carboxyl group bonds with a hydrogen from the alpha amino group of the other amino acid to form water then the H+ from the amino group being released to form a peptide bond?


texts: Why aren't all the fluorescence transitions the same wavelength?

texts: If all the excited molecules at higher S1 vibrational states rapidly relax to the lowest S1 vibrational state, why do the fluorescence transitions from v' = 1, v' = 2, v' = 3, and other states to v" = 0 have different wavelengths? Why don't they all relax to v' = 0 first and then all transition to the same vibrational level of v", releasing the same wavelength?


texts: Desilylation with potassium fluoride and methanol

texts:
Recently, I have done following reaction with KF adn methanol:

I don't understand why the sp-carbon silicon bond breaks and why no other sp3 carbon silicon bond breaks.

Thanks in advance.


texts: Migratory aptitude in pinacol pinacolon rearrangement

texts: Out of ortho-methoxyphenyl and para-methoxyphenyl which one has more migratory aptitude in pinacol-pinacolon rearrangement?


texts: How does the membrane potential change so drastically during an action potential?

texts:
I understand that the Nernst potentials
$$V = \frac{k_\mathrm{B}T}{e} \ln\left(\frac{c_\mathrm{out}}{c_\mathrm{in}}\right)$$
for all ions inside and outside a cell barely change when an action potential travels along the cell, because barely any ions transverse the membrane compared to the amount of ions present. However, the membrane potential has an enormous change of 100 mV.
Can someone provide an intuition for that behaviour?


texts: What would be the reaction if melting iron is put in normal water? Will water be chemically changed?


texts: Is the Lowdin Orthogonalization used in diagonalizing the atomic orbitals really a basis change?

texts:
This is kind of more on the mathematics side of quantum chemistry, but I can't quite figure out why the Lowdin Orthogonalization is called a basis set change. I get how it works from the perspective of matrices, and that it creates an orthonormal set as long as you have linearly independent input, but I don't get why it works as a change of basis.

Typically to change the basis set of a matrix $M$ you use a non-singular linear transformation $A$, which need not be unitary, as such: $$M'=A^{-1}MA.$$ Quantum mechanics, we are dealing with Hilbert Spaces, which produce an isometry between the Hilbert space and the dual (I think?), and then for post HF methods most methods often use unitary transformations, so that $A^\dagger=A^{-1}$, and so it becomes trivial.

The Lowdin transformation between nonorthogonal AO $|\phi\rangle$ and orthogonal AO $|\phi\rangle_\perp$ involves the overlap matrix $S$ as:
$$ |\phi \rangle_\perp = S^{-\frac{1}{2}}|\phi\rangle  $$
Then, the corresponding bra just has the adjoint, which is also $S^{\frac{-1}{2}}$ because the matrix is self-adjoint: $$ \langle \phi|_\perp = \langle \phi|(S^{-\frac{1}{2}})^\dagger = \langle \phi|S^{-\frac{1}{2}}$$

But, considering the matrix analog, why don't we use the inverse?

For instance, we have the identity: $$ D^{AO} = C  D^{MO}C^T $$ where $D$ is the 1-electron reduced density matrix. In my thinking this has to be a transformation from the MO to the AO on the right of $D^{MO}$, and from the AO to the MO on the left, which gives you $D^{AO}$. However, $C$ is not unitary obviously, because it comes from the Lowdin procedure, and so while $C$ on the left is from the AO to the MO, $C^{-1}$ is not equivalent to $C^T$.

Furthermore to get $D^{MO}$ matrix in terms of the $D^{AO}$ you DO have to apply the inverse relationship with $C^{-1}$. $$D^{MO} = C^{-1}D^{AO}(C^T)^{-1},$$ because $C^{-1}$ and $C$ and related non-trivially through $S$.

Hopefully this is appropriate to ask here. I think the answer involves Hilbert spaces but I can't find a lot on non-orthogonal transformations. Thanks!


texts: Reaction of alkenes with bromine in presence of sodium chloride

texts:
Consider the following reaction
           $$\ce{CH3\bond{-}CH\bond{=}CH2 ->T[$\ce{Br2}$/$\ce{NaCl}$]?}$$

What would be the product(s) for this reaction? I am confused because there are two nucleophiles here, $\ce{Br-}$ and $\ce{Cl-}$. So, there are two alternatives for the second step. Let me explain what I am saying.

First of all, the $\pi$-electrons will attack an electrophile which in this case is a $\ce{Br+}$ which is obtained form polarisation of the $\ce{Br\bond{-}Br}$ and it is added to the less substituted carbon, which complies with Markovnikov's rule, forming the carbocation below:
 $$\ce{CH3\bond{-}CH+\bond{-}CH2\bond{-}Br}$$

Now the carbocation will be attacked by a nucleophile. There are 2 nucleophiles in this problem, as I have stated earlier.
So, my question is which one of them will attack the carbocation and subsequently what will be the product? Will it be only 1,2-dibromopropane or only 1-bromo-2-chloropropane or a mixture of both? Please give the reasons.


texts:
So today we performed an experiment, where we mixed cyclohexene with Bromine water. The equation was

which seems to make sense. The Bromine water we were using was decoloured as evidence that this equation took place, whereas when we mixed cyclohexane with Bromine water nothing happened (to show how double bonds are more 'reactive'). But what I don't understand is why the double bond was broken. I mean, wasn't it happy just being the way it was? Doesn't it still take energy to break the double bond, even if it is less than the energy required to break a single bond? It isn't like it WANTS to take the bromine? (or is it?) The only place where this energy could have come from in my mind is either the vibrational energy due to temperature, or else the kinetic energy from pouring it in? (may be taking too much of a physics approach). If so, doesn't that mean that if I got the cyclohexane, and poured it in from a great height, will it react with the Bromine water? Or is the energy difference between double bonds and single bonds so great that it can only perform under special circumstances? (i.e. under UV light)


texts: Benzyl Carbocation Stability: Would electron-withdrawing group on the ring destabilize the carbocation?

texts:
In the following question I need to decide whether the reaction would undergo SN1 reaction or SN2 reaction.

I initially thought it would be SN1 since the resulting benzyl carbocation can be stabilized by resonance. Would the strongly electron withdrawing NO2 group destabilize it though? What kind of effect would this NO2 group have on the reactivity?


texts:
In kinetics, we use the steady state approximation to relate the concentration of intermediates to the concentration of reactants. For example, given the mechanism
$$\ce{A->[k_1]B}$$
$$\ce{B->[k_2]C}$$
using the steady state approximation for B gives $k_1[A]=k_2[B]$, so $[B]=\frac{k_1}{k_2}[A]$. Since B is at steady state, $[B]$ should be a constant through time. But the equation says that $[B]$ is a function of $[A]$ (and $[A]$ changes with time), so how can $[B]$ be constant? Am I misunderstanding the meaning of steady state here?


texts:
Disclaimer: I am not a chemist by any means, and I only have knowledge limited to what I learned in my university's Chemistry III course. Basic understanding of everything up to valence electron orbitals.
Why is there no set of rules to follow which can predict the product of chemical reactions? To me, it seems that every other STEM field has models to predict results (physics, thermodynamics, fluid mechanics, probability, etc) but chemistry is the outlier.
Refer to this previous question: How can I predict if a reaction will occur between any two (or more) substances? The answers given state that empirical tests are the best way we've gotten to predict reactions, because we can discern patterns or "families" of reactions to predict outcomes. Are we only limited to guessing at "family" reactions?
In other words, why am I limited to knowing my reactants and products, then figuring out the process? Can I know the reactants, hypothesize the process, and predict the product?
If the answer is "It's complicated", I would enjoy a push in the right direciton - like if valence orbitals actually do help us predict, or any laws of energy conservations etc, please give me something which I can go research.


texts: Explaining the photoelecton spectrum of krypton

texts:
The photoelectron spectrum of krypton is shown below.

(where the x-axis is in electron volts (eV))\

Since both the $3p$ and $3d$ shells are more than half full, based on Hund's rules the lowest-energy level is the one with the largest J, i.e. the $2\mathrm{P}_{3/2}$ and  $2\mathrm{D}_{5/2}$ states should be lowest in energy (higher value in eV). However, based on the peak intensities, this is not the ordering observed (see labeling in diagram). Why is this the case here?


texts: How is pumping "Air" into a bicycle make dW (delta work )negative , when in fact there is a increase in pressure and a slight increase in volume?

texts:
Considering that it's an adiabatic process hence $\mathrm dQ=0$, and $\mathrm dU=\mathrm dW$. And since the work is done on the system then $\mathrm dW$ must be positive.
(The answer which is in the textbook is that $\mathrm dU$ is positive, while $\mathrm dW$ is negative.)


texts:
I don't understand why this molecule is achiral:

I've circled what I think is the sole chiral center in red. I thought that any molecule with exactly one chiral center is chiral without exception. I built the molecule and its mirror image with my kit and can't find any superimposability.


texts: Why does a larger DNA gel box require a higher voltage to move DNA at the same speed?

texts:
If I run a small agarose DNA gel and use a voltage of 90V, the DNA migrates the length of the gel in about an hour. If I use a medium size gel I have to use a voltage of 140V to move the same DNA the same distance (the equivalent of the small gel) in the same amount of time. For a large gel it takes about 170V. What is it exactly that requires a higher voltage to maintain the same speed of DNA movement?

I think this is more of an electrochemistry question than a biology questions so I put it here.


texts: Why is acetic acid stronger than p-nitrophenol?

texts:
I know that acetic acid is a stronger acid than phenol because in acetic acid, the charge is delocalized on two oxygen atoms which is better than 1 oxygen and 3 carbon.

But in case of para-nitrophenol, $\ce{NO2}$ reduces the negative charge in the ring, thereby stabilizing the intermediate formed.

So does this mean that the stabilization caused by the presence of $\ce{NO2}$ is less than the delocalization caused by 2 oxygen atoms?

Kindly correct me if I am going in the wrong direction.


texts: Do hybrid orbitals exist in unbonded molecules? What would they look like?

texts:
For example, the ground state of a neutral carbon atom could be notated as:

$$ [\ce{He}] \underset{\ce{2s}}{[\uparrow \downarrow]} \underset{\ce{2p}}{[\uparrow \vert \uparrow \vert \; \;]} $$

I know $\ce{s}$ orbitals are shaped like spheres so the two electrons in the $\ce{s}$ orbital should probably form a spherical shape.

But how should the electrons in the $\ce{p}$ orbitals be distributed?

I think in the end result a neutral carbon atom is either shaped in a trigonal-planar arrangement or a linear arrangement.

So do hybrid orbitals exist in unbonded molecules? What would they look like?

I think this would have interesting results for collisions between atoms and how probable certain reactions are.


texts:
I came across a naming convention which I haven't seen before. I let ChemDraw name the following compound for me and got a name containing lowercase "r" and "s" configurations.

Can someone tell me what this means and something about the actual convention behind it? I think it must have something to do with rings and maybe with some kind of "pseudo-chirality" due to a certain conformation of the ethyl group which is attached to the ring, but I'm only guessing.


texts: Which rate is faster: one step with Ea or two steps each with Ea/2?

texts:
I have been struggling with the following problem posed at a prior lab meeting. The answer seems trivial to me, so can you tell me if I'm doing this wrong? Thanks!

Consider the following two scenarios. They represent a small portion of the same catalytic cycle.

There is a reaction step of that cycle wherein $A\rightarrow P$ with an activation energy $E_{a}$.
Upon further inspection, the above reaction is actually $A\rightarrow I\rightarrow P$, where each of the two steps has an activation barrier of $E_{a}/2$ such that their sum is equal to the barrier height in the first scenario. Refer to the schematic here for a depiction if needed.

The question is: which scenario is faster? My thought process is as follows.

First, we need to define which rate we are talking about. I am going to assume the rate of production of product, $dP/dt$, is compared. I need information about pre-factors, but I'll have them all equal an arbitrary value of 1 for the time being. I have set $[A]_{t=0}=1$, $[P]_{t=0}=0$, and $[I]_{t=0}=0$. I now write out my ODEs and solve them. I've assumed $E_{a}=RT$ for demonstration purposes.

Case 1:

Case 2:

Comparison of Rates:

My Issue:

Can the question not be definitively answered? It seems like the answer (whether case 1 is faster than case 2) is that it depends on what conversion you're running to since the answer changes at a certain point. However, this was asked in the context of catalysis. I've posed this problem to multiple people and they all brought up the point that they don't usually think about time or conversion in this regard. They just want to know which one of these two cases will be faster when looking at two potential energy profiles. Isn't that too naive, or am I thinking about this all wrong? At full disclosure, this is mildly related to a prior question I posed in the comments located here.

Edit: To emphasize, if I change the pre-factors or the value of $E_{a}$, the order of which case is faster will also change. So, the answer to the question in the title is that "it depends".


texts: Do metal ions of 4d and 5d series always form low spin complex?

texts:
I've recently come across a source where it stated that all 4d and 5d metals form low spin complexes irrespective of the strength of ligand.

I'm not sure of the authenticity of the source and couldn't figure out the reason for this phenomenon, thereby enquiring about it.

I feel that the splitting energy is higher than pairing energy in this case, but I am not able to justify it properly.


texts: Which is the better leaving group in the following Cannizzaro reaction?

texts:
In the given mechanism, is it correct to prefer hydrogen as a better leaving group than the formyl group?

The negative charge on an sp2 hybridized carbon, with the carbonyl group attached to it, seems to be more stabilized than a negative charge on hydrogen. (I have starred the step I am referring to)


texts: Does the magnesium 2+ ion prefer an octet or more?

texts:
In organic chemistry I was told that the magnesium ion which is part of Grignards is coordinated to several ether molecules. The overall structure around the magnesium is tetrahedral, which implies that two ether molecules have coordinated to the magnesium center. The professor said something about fulfilling magnesium ion's octet with this configuration.

In inorganic chemistry and biochemistry however I learned about hexacoordinated magnesium - i.e. $\ce{Mg(H2O)6}$. Magnesium ion tends to form octahedral complexes; this implies a coordination number of 6.

So -

1) Does magnesium ion adopt both these configurations? Can it be found as part of tetrahedral and octahedral complexes?

2) Which is preferred? I suspect this answer depends on a variety of factors.


texts: Where to find good worksheets for balancing chemical equations

texts: I am preparing for the Chemistry SAT in a couple of weeks. I am looking for worksheets like this that will give me practice balancing complex chemical equations with lots of compounds. Is there any website where I can find such questions in bulk? (And also, check my answers?) Thanks.


texts: In helium-2, would each electron experience a single positive charge from the nucleus?

texts: If we have an atom of hydrogen-1, we know that there exists one proton with one electron and in helium-2 two protons with two electrons. My question is that do protons get shared equally with electrons? For example, is it true that each electron in helium experiences the same force from the nucleus as each electron in hydrogen, due to the proton to electron ratio being 1:1 in both atoms?


texts:
My teacher told me we can convert benzene to phenol within a single step using $\ce{V2O5}$/ $\ce{O2}$ at 300 ⁰C (not 500 ⁰C). Later I searched for that reaction but I couldn't find it in all over Google except in Allen's Chemistry handbook.

Does that reaction really occur and if it occurs then what is the mechanism of that reaction?


texts: Covalency of metal oxides in high oxidation states

texts:
So, metal oxides are generally basic, right? But in higher oxidation states their covalent character is predominant. For example in
Mn2O7 the Mn - O bond is covalent. Why is that?


texts: Do buffers only work for species of the opposite variety? (I.e. weak acids buffer strong bases and vice versa)

texts:
I have looked at several sources including Khan Academy, ChemCollective and the answer to a similar question:
Can someone please explain buffers to me?

However, it is not clear whether buffers can only protect against the opposite species. I.e. a weak acid can only protect against the pH change caused by strong bases, or if it can also protect against the pH change caused by strong acids.

This is my thought:

If we have $\ce {H_2CO_3_{(aq)} + H_2O_{(l)}<=>H_CO^{-}_3_{(aq)} +  H_3O^+_{(aq)}}$

Then we add a strong acid $\ce{HCl + H_2O-> H_3O^+ + Cl^-}$

Then we have $x$ amount of protons in the solution and for every one of the weak acid's conjugate base, there is a proton. So, to me it appears that there is no way for the weak acid to act as a buffer for a strong acid. Is this correct or am I missing something?


texts: Why is the Kelvin Temperature Scale Based on the Triple Point of Water?

texts: Why would the Kelvin temperature scale not just be based on the freezing point of water, which is only .01 degrees Celsius off from it? Is this just a more accurate way of measuring and quantifying the value?


texts: Is the rate of desorption dependent on pressure?

texts:
While I was learning about Langmuir's adsorption isotherm in my chemistry class, my teacher talked about the situation when the rate of adsorption and desorption will become equal. However, he mentioned that the rate of adsorption is dependent on pressure but the rate of desorption is not and when he gave an explanation I wasn't satisfied with it.
I would imagine that greater the external pressure on the adsorbent lesser will be the tendency of the adsorbate particles to leave the surface. But that isn't what my teacher said. Please explain.


texts: How can I generally determine which bonds are longest/shortest in a molecule?

texts: My task is to arrange the bonds from longest to shortest. Although I have the answer (C,D,B,A), I'm having a very hard time understanding how to derive this answer. Any clues would be helpful, especially those that help me in other related problems.


texts: Why did they provide the value for the enthalpy change of fusion?

texts:
The metal gallium melts when held in the hand; its melting point is $\pu{29.76 ^\circ C}$. How much energy as heat is removed from the hand when $\pu{5.00 grams}$ of gallium initially at $\pu{20.0^\circ C}$ melts? The value of $\Delta H_{fusion}$ is $5.576~\mathrm{kJ~mol^{-1}}$ and the specific heat of gallium is $0.374~\mathrm{J~g^{-1}K^{-1}}$. Take the final temperature to be $\pu{29.76 ^\circ C}$.

I got:

$$q = (\pu{5.00 g})(0.374~\mathrm{J~g^{-1}K^{-1}}) (\pu{9.76^\circ C})$$

$$q=\pu{18.3 J}$$

So I reason that since $\pu{18.3 J}$ of energy in the form of heat is required to melt gallium from at an initial temperature of $\pu{20.0 ^\circ C}$ to a final of $\pu{29.76 ^\circ C}$ then this is all the energy required to do this but why did they give $\Delta H_\text{fusion}$?


texts: If all chemical processes are equilibria at least to some extent, where does the activation energy come from?

texts:
If all chemical processes are equilibria at least to some extent, then where does the energy to overcome the activation energy come from?

Is a process with a very high activation energy (i.e. the ionization of sodium vapor into sodium ion) still considered an equilibrium process at least to some extent?

If so, where might the energy to furnish the forward reaction come from naturally - i.e. with no human input of energy?


texts: In the Carnot cycle the overall work done on the piston is positive. I am having trouble with the real meaning of that. Does positive work mean the piston is moved up and has, over the course of the cycle, gained potential energy?


texts: Is it possible to make a concentration cell without ion-permeable membrane?

texts:
I struggle to understand the use of ion-permeable membrane (or salt bridge). https://en.wikipedia.org/wiki/Concentration_cell

If i pour two solutions with different concentration, why do you need the junction between solutions ?
Like this :

According to my readings on Galvani's potential the electrode should be polarised with the potential of the solution their in. Hence you can calculate the concentration of unkown solution C2 without junction ?
In this page https://en.wikipedia.org/wiki/Salt_bridge it is said that the salt bridge is needed to avoid having one solution depleted of electrons and another full. Why the connection of electrode isn't creating equilibrium between solutions ?


texts: In this picture, there is a $1s$ and a $2s$ orbital. Are the orbitals only the dark gray circles ? Or are the light gray circles (which are surrounding the dark gray ones on both sides) also included in the orbitals? Other than these two types of circles , there are the nodes which never include any electrons. And since people define an orbital as a region where electrons are most likely to be found, this must mean that the orbitals are only the gray circles because if they included the light gray circles too, then the probability of finding electrons in an orbital would be 100%.


texts: Has the half-life of an isotope ever been accurately predicted before it could be measured?

texts:
The half lives of many radioactive isotopes have been measured directly. But are their half-lives known to be a function of their composition?

In other words, can someone say "given an atom with this many protons, neutrons and electrons, and given the known strengths and ranges of the various forces at play inside an atom, we can quantify how unstable such an atom would be by saying that a collection of them would have a half-life of X"?

Has such a prediction ever been made about an isotope before people had encountered it, then later borne out by experiment?


texts: What simple formal systems are there that have behavior similar to actual chemistry?

texts:
I've been doing reading about formal/axiomatic chemistry and am wondering: are there attempts at making formal systems (well defined rules that can be simulated on a computer) that have similar emergent behavior to real world chemistry in some way?

Clearly this would be very difficult for reproducing all of the physics of matter but I haven't been able to find any papers about attempts to make simple systems that have meaningful 3D interactions besides cellular automata which are very different.


texts: Are there any actual uses of isodiaphers?

texts:
While studying atomic structure, I came across the terms isotopes, isobars, isoelectronic species, isotones and isodiaphers. While I can accept that the classification of isotopes, isobars, isoelectronic species and isotones may be useful, I do not understand what could be the use of species with the same difference between number of neutrons and protons (isodiaphers).
Is there any place in chemistry where they have a practical use (like in experiments, theories or laws), or is it just a useless classification term?


texts: Bond lengths: 1-D particle-in-a-box for 1,3-butadiene

texts: When estimating the length for a one-dimensional particle-in-a-box model for a hydrocarbon (such as 1,3-butadiene), do we include the bond lengths between the (terminal) carbon and hydrogen atoms at the ends of the chain?


texts: Does Suncream have any affect or help protect against radiation

texts:
So I was just watching the HBO series Chenoybl and saw that people suffered various degreesvof burns from radiation form Uranium 235 and some were very minor and looked like a normal sun burn.

My question is, does Suncream protect against radiation burns?


texts: What is the balanced ionic redox reaction of nitrite ions with manganate(VII) ions in acidic solution?

texts:
What is the balanced ionic redox reaction of nitrite ions with manganate(VII) ions in an acidic solution?

My suggestion is:

$\ce{5NO2-   +   2MnO4-   +   6H+   ->   5NO3-   +  2Mn^{+2}  +  3H2O}$

Is that right?


texts: Why does Stokes raman not relax to the ground state while anti-Stokes does?

texts:
I'm just wondering why stoke-Raman doesn't go to the ground state. Where does the rest of energy from exciting laser leave?
On the other hand, why does anti-stoke go back to ground state? I know that the overall energy of anti-stoke is higher but why it has to go back to the ground state?
My question is based on this diagram.

As I understand, the anti-stoke has higher energy as it is excited from v1 due to an enhancement. I'm just confused with the last process of anti-stoke when it comes down to the ground state. Why doesn't it come down to the v2 or higher vibrational state like stoke?


texts: What would be the mechanism for this condensation reaction?

texts:
Below is the reaction in question. Will it go like an aldol consensation would, where the base would deprotonate the methyl group of the benzoxazole moiety, the negative charge would be transferred over to the nitrogen and this anion would then bond with the aldehyde?
In any way, a drawing of the mechanism would be really helpful.
A bonus question: is this a specific type of condensation? (i.e. like aldol)


texts:
$$\begin{align}
p &= kT\left(\frac{\partial \ln Q}{\partial V}\right)_T \\
&= \frac{kT}{Q}\left(\frac{\partial Q}{\partial V}\right)_T \\
&= \frac{NkT}{q}\left(\frac{\partial q}{\partial V}\right)_T \\
&= \frac{NkT\Lambda^3}{V}\cdot\frac{1}{\Lambda^3} \\
&= \frac{NkT}{V} \\
&= \frac{nRT}{V}
\end{align}$$

Looking at the first equation in this series I'm really confused how the $\partial \ln Q/\partial V$ has been simplified to $\partial Q / \partial V$.

My hunch is that it's something to do with the derivative of $\ln Q$ being $1/Q$ however I'm not sure how this ties in.


texts:
I would like to taste Pepsi-cola without acid. I like it's flavor but don't like acidic taste. It's acidity comes from carbon dioxide, phosphoric and citric acids (see ingredients list in wiki and answers to this question). Carbon dioxide can be evaporated easily. How can I get rid of phosphoric and citric acids? Preferably without expensive lab equipment and hard-to-get reagents.

Edit: Found one recipe by Josh Velson on quora site. He advises adding limewater until the pH reaches about 12.32. Are there any other methods?


texts: How can I choose an indicator for determining the concentration of a base using its pKb values?

texts:
I have a base $\ce{M(OH)_{3}}$ having 3 $\mathrm{p}K_{\mathrm{b}}$ values as,
$$
\mathrm{p}K_{\mathrm{b}_{1}} = 0.5\\
\mathrm{p}K_{\mathrm{b}_{2}} = 3.7\\
\mathrm{p}K_{\mathrm{b}_{3}} = 7.7\\
$$

If a strong acid is given as the titrant and phenolphthalein and methyl orange are given as possible indicators, how can I choose an indicator using above $\mathrm{p}K_{\mathrm{b}}$ values ?


texts: Are aromatic amines or amides less basic?

texts: When the lone pair of an amino group $\ce{R-NH2}$ is involved in resonance, its basicity decreases. But, between conjugation with carbonyl group $\ce{R}=\ce{R'CO}$ or resonance with benzene $\ce{R} = \ce{Ph}$, which one will reduce the basicity of amino group to a greater extent?


texts: Water electrolysis - what is happening to an iron anode?

texts:
So I made an experiment to find a good electrolyte for a water electrolysis.

I tried citric acid, which turned out to not produce any gases at the anode, I tried sodium hydroxide, which turned out to be the very best, and I tried sodium carbonate.

The $\ce{Na2CO3}$ solution was about 2 g/l.

As my electrodes I decided to try some nails, very likely made of iron or some iron alloy.

So I hooked up my power source, just two nine-volt-batteries in series, and started the electrolysis.

The kathode (negative terminal) bubbled vigorously, indicating the production of hydrogen gas.

The anode (positive terminal) however bubbled very little and started decomposing, gray-green flakes started falling off and sinking to the bottom. This decomposition started as soon as the power was supplied.

This struck me, because I was expecting oxygen to be liberated at the anode!

When I took my anode out, it was at first a dirty green or green-gray, but it quickly turned a rusty brown.

So in conclusion, the kathode produced hydrogen with no sign of wear when on the other hand the anode made little gas and decomposed into probably some iron compound, which turned into probably iron oxide (I'm judging by the color here) on prolonged contact with air.

So, what could it be? I thought it might be iron hydroxide, but that'd be brown. This however was green.


texts: What do graphene "armchair(5,5)" and "zigzag(5,0)" refer to?

texts:
I am reading some articles about the electronic properties of graphene and while reading it I came across graphene armchair and zigzag structures, which have different bond structures.

The two different orientations (armchair and zigzag) are due to the arrangement of carbon atoms in the periphery (wiki), but I am unable to understand what armchair(5,5) and zigzag(5,0) mean.


texts:
I remember my teacher saying that during E2 (elimination bimolecular) reactions of alkanes, if the strong base that is used as a reagent is a bulky one, it has higher probability of giving a Hofmann (less stable) product as the major product even if there are possibilities for a Saytzeff (or Zaitsev) product to form.
How should I find if a base is bulky or not?
Some bases like t-butoxide ion are pretty obvious. I usually just guess it is based on how much steric-clouded it seems when I draw a representation on a paper. Is there any better way to figure this out?


texts: Why do hydroxyl groups only produce a singlet in proton NMR?

texts: Take, for example, methanol ($\ce{CH3OH}$). The hydroxyl proton ($\ce{-O$\color{red}{\ce{H}}$}$) is three bonds away from three more protons ($\ce{-C$\color{blue}{\ce{H}}$_3}$), which aren't equivalent to it, so why would this not produce a quartet using the $n+1$ rule?


texts:
I am trying to identify a compound that could be used to soften a Rubic’s Cube’s plastic to make it turn faster and smoother.

I have read that a number of cubers have used a Boron treatment to accomplish this.  Unfortunately Boron is hazardous and I am looking for a safer alternative that would accomplish the same thing.

Thanks!


texts: What would be SMILES notation for a compound with delocalized bonding?

texts:
For example, the cyclopentadienyl rings in ferrocene $\ce{Fe(}\eta^5 \ce{-C5H5)2}$ are often drawn with delocalized electron circles in them instead of explicit pi bonds.

The Wikipedia article for ferrocene provides the following SMILES string: [cH-]1cccc1.[cH-]1cccc1.[Fe+2]. In this SMILES string, the charge on the cyclopentadienyl ligands are explicitly attached to carbon atoms in the ring.

Can explicit or implicit delocalization be stored in a SMILES string? For example, would c1cccc1.c1cccc1.Fe also be an acceptable SMILES string for ferrocene that can be parsed and understood?
Does the localized version of the SMILES string provide enough information for the delocalization to be reconstructed when the string is parsed back into a structure? If not, how can this be done?


texts: chemically inert molecule with piezoelectric properties

texts:
For a research project, I'm looking into existing  chemical molecules that have the following properties:

It is mostly chemically inert, safe for animals and children
It exhibits piezoelectricity -  production of high electric oscillating potentials under pressure
paramagnetic moment a plus, but not required

Are there known candidates for this?


texts: Questions about combustion and isotopic abundance

texts:
the combustion of 0.214g of sulfur provided exactly 0.428g of sulfur dioxide. After a second try, 0.782g of SO2 was obtained. What mass of sulfur was used?
The combustion of lithium forms lithium oxide. Combustion involving a 1.451g sample of oxygen results in obtaining 2.710g of Li2O. What mass of lithium was involved in this reaction?
Natural argon has three isotopes: Ar-36 (35.967u), Ar-38 (37.962u), and Ar-40 (39.962u). if the isotopic abundance of Ar-36 is 0.006%, find the isotopic abundance of the other two

After pulling my hair out:

I still have no idea how to do this question.
I balanced the equation $4Li + O_{2} -> 2Li_{2}O$ then found the moles of both oxygen and lithium oxide, which was 0.090688 mols and 0.090333 mols. Used the smaller number of moles, set up the ratios $\frac{4Li}{2Li_{2}O} = \frac{x}{0.090333mols}$
x = 0.1807 mols, which equals to 1.2647g of Li
Is this correct?
35.967(0.00006) + 37.962(x) + 39.962(1-x) = 39.948
0.00215802 + 37.962x + 39.962 - 39.962x = 39.948
-2x = -0.01615802
x = 0.00807901
which mean Ar-38 is 0.8%, but the answer clearly says it is 0.588%


texts:
In my AP Chem class we are working on testing Hess's Law and conducted three reactions. Then enthalpy changes of the 1) $\ce{NaOH + HCl}$ and 2) $\ce{NaOH + NH4Cl}$ to predict the enthalpy change of 3) $\ce{HCl + NH3}$.

I used the equation $q = C_pm\Delta T$. We determined the $q$-values using a method given to us by our teacher. She told us to assume a denisty of $1.03\ \mathrm{g/mL}$ for all solutions, we then multiplied the density by $50\ \mathrm{mL}$ to determine the grams of each reactant present. That value is the $m$ term. We used $4.18\ \mathrm{J/(g\ ^\circ C)}$ for the specific heat of water. The temperature change for the first reaction was $14.7\ \mathrm{^\circ C}$, the second was $1.2\ \mathrm{^\circ C}$, and the third was $9.8\ \mathrm{^\circ C}$.

The first reaction yielded a q value of $6328.938\ \mathrm J$, the second yielded $516.648\ \mathrm J$, and the third yielded $4219.292\ \mathrm J$.

The next step would be to convert this $q$ values into $\mathrm{kJ/mol}$. I consulted my lab partner who did the following operation:

$$\mathrm{kJ/mol} = 6328.938\ \mathrm J \times 1\ \mathrm{kJ}/1000\ \mathrm J \times x/0.2\ \mathrm{mol}$$

In his math, there was no numerator on the $0.2\ \mathrm{mol}$ term. The mol value he used came from there being 0.2 moles of the reactants present. I believe his math to be incorrect, but as my teacher is out sick and there are no other chemistry teachers present, I cannot determine the correct conversion. I believe it to be:

$$\mathrm{kJ/mol} = 6328.938\ \mathrm J \times 1\ \mathrm{kJ}/1000\ \mathrm J \times 6.022^{23}/0.2\ \mathrm{mol}$$

Both of the conversions yield values with significant % error. Any assistance is appreciated.


texts:
I was wondering why all of the percentages like mass percent composition, percentage yield and percentage purity are calculated using masses.

Wouldn't it make more sense to use number of moles of the substance since we're counting the number of atoms in the molecules?


texts: Making Ferric Chloride using HCl and Ferrum

texts:
I am not chemist: I live in the part of the world that you can't find many things, but I have HCl and bunch of nails. I there way to make ferric chloride from these things?
If this doesn't work what else can I do to make ferric chloride?


texts: Which is more stable in gas phase, free radicals or ions?

texts:
Answering some kinetics questions I came across this statement:

  Free radicals are more stable in the gas phase than ions.

Is this correct or not? Why? Is there a different trend in liquid or solid phase?


texts: Why is hydrogen sulfate put together as it is?

texts:
I recently looked up hydrogen sulfate ($\ce{HSO4-}$) to see how it's put together, and found this image of methyl hydrogen sulfate:

I'd assume that hydrogen sulfate looks the same, but without the methyl group attached. However I'm confused, how can it be constructed like that? This shows the sulfur having a total of 12 valence electrons, but shouldn't the maximum be 8?

I might be asking something that'll be obvious to me later on in chemistry, but this (and other groups that act as atoms) appear early on. I probably don't need to know it yet but I'd prefer to know how it works if I can as opposed to just accepting it.


texts:
We know that sulfur can form sulfides $\ce{R2S}$, with two substituents bonded to it. The simplest example of this would be hydrogen sulfide.

However, sulfur can also form sulfonium ions $\ce{R3S+}$, where 3 substituents are attached to the sulfur atom and a negatively-charged counteranion is present.

What I am asking is whether there is such a thing as sulfur bonded to 4 substituents, with each bond being a single bond, with 2 counteranions (either $\ce{(R4S^2+)(X^2-)}$ or $\ce{(R4S^2+)(X^-)2}$). Is there such a thing as that or something similar?


texts: Hydrogenation side product: potential mechanisms for C-C bond making

texts:
In the analysis of the product mixture of a new catalytic hydrogenation  reaction I'm trying out I am getting this side product molecule (in low quantities; less than 1% w/w).

Is this a likely / explainable side product? What would be a potential mechanism?

I'm skeptical because the C8 increases to a C9. I assumed C-C bond making wasn't a very common occurrence in this sort of reaction? Or is it?

The reaction conditions are fairly mild: 10 barg & 80 C. Somehow I associated this sort of hydrogenation with functional group identity changes & not Carbon-backbone changes.

Or am I wrong?

More info. Solvent is Methanol. pH is alkaline by small qty. of NaHCO3 initially added. Catalyst is Pd on C.

Edit: Supposing the MeOH solvent reacts with the starting material, would this be the reaction to expect?

Any mechanism to go from this alcohol-ether to the impurity I'm seeing?


texts:
I recently studied carbohydrates. I was taught that fructose on oxidation with strong oxidizing agents like concentrated $\ce{HNO3}$ yields glycolic acid and tartaric acid along with trihydroxy glutaric acid. Though I am confused why glycolic acid is formed instead of oxalic acid (since the terminal $\ce{-OH}$ should also have been oxidized) I am also satisfied that oxidation of the keto group in fructose breaks it off into 2 carboxylic acids and yields a 2 carbon(glycolic) and a 4 carbon(tartaric) containing acid.
But I am very much unable to figure out the formation of trihydroxy glutaric acid by oxidizing fructose since its a 5 membered carboxylic acid and in no reaction I know did I ever come across such breakage of ketones in 6=5+1. Some sources even cited the formation of trihydroxy butyric acid along with oxalic acid where I couldn't understand why tartaric acid wasn't formed by oxidation of the terminal $\ce{-OH}$ group.


texts: Enthalpy and Internal Energy in Constant Volume Calorimeter

texts:
It is my understanding that enthalpy differs from internal energy only in that the change in enthalpy takes into account any pressure-volume work done on the system (or by the system) in a reaction, and thus it is equal to the heat transferred to the system, at least in constant pressure.

Many sources say that in a constant pressure, "coffee cup" calorimeter, $q_p = \Delta H$. I understand that. However, they also say that the $q_v$ in a constant-volume calorimeter is equal to the change in internal energy, and not necessarily the change in enthalpy. My thought is that since $\Delta H = \Delta U + P\Delta V$, with $\Delta V$ being zero (it is by definition constant volume), is not $\Delta H = \Delta U = q_v$?


texts: Langmuir parameters for fixed bed continous column

texts: I have prepared a model of fixed bed adsorption column in MATLAB. I have to insert Langmuir parameter value there, so how can I calculate them in case of continuous fixed bed column. I have calculated them in previous batch study. How to calculate them for continuous column, what data should I get?


texts: Why are elements on the right side of the periodic table nonmetallic and gas at room temperature?

texts: Elements on the left side of the periodic table tend to be solid and metallic, elements on the right side of the periodic table are nonmetal and tend to be gases at room temperature, and the semi-metals are in between.  Why is that?  Why are the elements on the right side nonmetallic and in a gas phase?


texts: Normally octane percentage is mentioned on petrol (95% octane). How is this defined? Is it percentage of chemical or some other parameters?


texts: Can I use the mono ammonium phosphate found in fire extinguishers to make crystals?

texts: I recently opened up a old decompressed fire extinguisher out of curiosity. After some research I discovered that the dry powder inside, mono ammonium phosphate, can be used to make beautiful crystals. However, I found this powder to be extremely hydrophobic and could never get its dissolve in water at all. I mean this stuff is amazingly hydrophobic. Its fun to see how it reacts in water. But why cant it dissolve and what kind of preparation of mono ammonium phosphate will dissolve and become crystals?


texts:
In Allenes, the $\ce{C=C=C}$ structure makes sure that the $p$-orbital of central carbon overlaps with 2 other carbons and the $p$-orbital of central carbon spreads out over the 3 carbons.

In Alkynes, the $\ce{C#C-C}$ structure makes sure that the energy released during formation of alkynes.
I also read that more the number of non-delocalized $\pi$-electrons on an atoms, the lesser its stability, though I do not know why.

When, it comes to comparing Allenes and their isomeric Alkynes,it has always been stated that  "Allenes are more stable than Alkynes".

One reason I found was that $\pi$-electrons in Allenes are less strongly bound than those in Alkynes.

Why are $\pi$-electrons less strongly bound?  If the reason in incorrect, what is the actual reason?
Why is it that as the number of non-delocalized $\pi$-electrons increases on a carbon, the smaller its stability?


texts: In vibrational spectroscopy, what affect do overtones have on the spectra?

texts: I've been in a lecture about vibrational overtones in anharmonic oscillators. How would these affect an IR spectrum?


texts: How do point mutations affect complementary base-pairing and widths of the nucleotide pairs?

texts:
Point mutations are divided into two categories: transitions and transversions. Since point mutations only occur during DNA replication (an integral process of both mitosis and meiosis), the mutated nitrogenous bases only appear on the newly synthesized DNA strands, rather than on the parental strands that serve as templates during DNA replication.
A transition occurs when a would-be purine is replaced by another purine, or a would-be pyrimidine is replaced by another pyrimidine. In contrast, a transversion occurs when a would-be purine is replaced by a pyrimidine, or vice versa. Because the two strands of a DNA molecule always follow the strict rule of complementary base-pairing, there must be some impact on chemical structures of the DNA molecule when either a transition or a transversion occurs.
Specifically, under normal circumstances, an adenine forms two hydrogen bonds with its complementary thymine, and a cytosine forms three hydrogen bonds with its complementary guanine. When a transition occurs, such as when a would-be thymine is replaced by a cytosine, would hydrogen bonds still form between the two bases? And how many hydrogen bonds will there be? Same questions for when a transversion occurs, such as when a would-be thymine is replaced by a guanine.
Another relevant point to ask is the distance between the two DNA strands that constitute a DNA molecule. The rule of complementary base-pairing helps to maintain equal widths for each complementary base pair. Thus, an A-T pair and a C-G pair are of the same width. But when a transition occurs, would the new A-C combination have a different width? Same question for when a tranversion occurs.
Thanks to anyone who answers my questions.


texts: Why put zinc solution in a galvanic cell?

texts: In a galvanic cell with Cu and Zn electrodes, I was taught that each electrode is immersed in a solution containing it's own positive ions. I understand why you need copper ions, so they can gain electrons, but why do you need zinc ions - the reaction is going to produce zinc ions anyway, and the negative ions from the salt bridge will migrate to neutralize them, so I don't see why you need zinc ions at the first place. Is there anything I'm missing in how the cell works?


texts: How to apply Faraday's law to calculate the charge of metal ions?

texts:
Electrolysis of a molten ionic compound with a current of $\pu{0.50 A}$ for $\pu{30 min}$ yielded $\pu{0.700 g}$ of a metallic element at the cathode. If the element has a relative atomic mass of $150.0$, calculate the charge on the metal ions.

My attempt at solving:
$$n = \frac{m}{M} = \frac{0.7}{150} = \pu{4.67e-3}\\
Q = Ft = 0.5 \times (30 \times 60) = \pu{900 C}$$

The main problem I'm having here is that, how do I relate this unknown metallic ionic compound to the amount of electrons gained in this reaction?

After I obtain that can I just use $$Q = n\ce{e-} \times F?$$

I then solved for $$F = Q/n = \pu{1.92E5 F}$$. I was experimenting with some stuff and divided this by $\pu{96500 C}$ which got me $1.99$. The correct answer was $\pu{2 F}$.

Is this just coincidence because I don't see the connection between dividing by $\pu{1 F} = \pu{96500 C}$ when I already solved for $F$?


texts:
Please help me. We just did an experiment wherein we used Fe, Al, Zn, Sn, Cu and HCl to see their reaction (e.g. Fe + HCl, Al + HCl...). The result of the experiment:

1.) $\ce{Fe + HCl}$ = formed bubbles (56 min)

2.) $\ce{Al + HCl}$ = formed bubbles (more than 1 hour)

3.) $\ce{Zn + HCl}$ = formed bubbles (42 min)

4.) $\ce{Sn + HCl}$ = No reaction

5.) $\ce{Cu + HCl}$ = No reaction

Now with the result, how can I distinguish metals from non-metals?


texts: Explaining why s and p orbitals do not interact

texts:
While going through molecular orbital theory, my chemistry teacher mentioned that the reason why there is no significant interaction between $\ce {s}$ orbitals on one atom and $\ce {p_x}$ and $\ce {p_y}$ orbitals on another atom is that the $\ce {s}$ orbitals interact with both lobes of the $\ce {p}$ orbitals, having both in phase and anti phase interactions with these $\ce {p}$ orbitals, taking the z axis to be the internuclear axis.

However, I read that orbitals which do not have the right symmetry simply cannot interact, i.e. their overlap integral is necessarily $\ce {0}$. Thus, is the reasoning given by my chemistry teacher actually valid?


texts:
Wikipedia says the formula of aluminum oxynitride is this $\ce{(AlN)_x·(Al2O3)_{1−x}}$,
$0.30 \leq x \leq 0.37$ . What does this formula mean?


texts: Kinetics of interstellar chemistry: Applying steady state to formation of H₂

texts:
I am trying to solve problem 2 from the 2009 International Chemistry Olympiad (IChO), which is as follows:

  If two atoms collide in interstellar space the energy of the resulting molecule is so great that it rapidly dissociates. Hydrogen atoms only react to give stable $\ce{H2}$ molecules on the surface of dust particles. The dust particles absorb most of the excess energy and the newly formed $\ce{H2}$ rapidly desorbs. This question examines two kinetic models for $\ce{H2}$ formation on the surface of a dust particle.

  In both models, the rate constant for adsorption of $\ce{H}$ atoms onto the surface of dust particles is $k_\mathrm a = \pu{1.4*10^-5 cm3 s-1}$. The typical number density of $\ce{H}$ atoms (number of H atoms per unit volume) in interstellar space is $[\ce{H}] = \pu{10 cm-3}$. (You may treat numbers of surface adsorbed atoms and number densities of gas-phase atoms in the same way as you would normally use concentrations in the rate equations).

  Desorption of $\ce{H}$ atoms is first order with respect to the number of adsorbed atoms. The rate constant for the desorption step is $k_\mathrm d = \pu{1.9 * 10^-3 s-1}$. Assuming that only adsorption and desorption take place, calculate the steady-state number, $N$, of $\ce{H}$ atoms on the surface of a dust particle.

First off, what do they mean by steady-state number here? I tried searching online but I could not find anything. The solution they give has the equation:

$$k_\mathrm d N − k_\mathrm a[\ce{H}] = 0$$

from which they solve for $N$. I know this has something to do with steady state, but in this case why must the rate of absorption be equal to the rate of desorption? Is it because you are considering a single $\ce{H}$ atom which is considered to be an intermediate? Also, why is it $k_\mathrm dN$?

Further, why is the rate of desorption not simply the reverse of the absorption reaction and thus the same rate but with a negative sign?

In the above, how did they come up with those rates? Why does absorption have $\ce{[H]}x_m$ but desorption have $\ce{m}x_m$? Finally, for the reaction rate, where did they get $m(m-1)$? I think the $\frac{1}{2}$ comes from the fact that the rate of production of $\ce{H2}$ is half the rate of absorption/desorption, is that right?

From these, they calculate the rate of change of $x_0$, $x_1$, and $x_2$ as follows:

  $$\begin{align}
\frac{\mathrm dx_0}{\mathrm dt} &= -k_\mathrm a[\ce{H}]x_0 + k_\mathrm d x_1 + k_\mathrm r x_2 \\
\frac{\mathrm dx_1}{\mathrm dt} &= k_\mathrm a[\ce{H}]x_0 - (k_\mathrm a [\ce{H}] + k_\mathrm d) x_1 + 2k_\mathrm dx_2 \\
\frac{\mathrm dx_2}{\mathrm dt} &= k_\mathrm a[\ce{H}]x_1 - (2k_\mathrm d + k_\mathrm r)x_2
\end{align}$$

I sort of understand how they got the value for rate of change of $x_0$ as it is the rate of production minus the rate of consumption, and desorption from state 1 and reaction produce state 0, while absorption consumes it. However, why does the $k_\mathrm a$ term come with $[\ce{H}]$ while the other terms do not? What happened to the $m x_m$ that was mentioned above?

Further, how did they get the rate of change for $x_1$ and $x_2$?


texts: Magnetic work and the first law of thermodynamics

texts:
We commonly encounter the first law of thermodynamics in the form $\mathrm{d}E = T\mathrm{d}S - p\mathrm{d}V + \mu\mathrm{d}N$, which notes the contribution of thermal, pressure-volume, and chemical work to the total energy respectively. More generally, we can write $$\mathrm{d}E = \sum_i f_i\mathrm{d}X_i,$$ where $f_i$ denotes a generalized force and $X_i$ a generalized displacement.

The pattern for all these types of work seems to be rather obvious---the generalized force is intensive, whereas the generalized displacement is extensive---but this fails when we try to take into account magnetic work, which contributes the term $-\mathbf{m}\cdot\mathrm{d}\mathbf{B}$, with $\mathbf{m}$ the magnetic moment and $\mathbf{B}$ the magnetic field (see Hill, Chandler, Blundell, etc.). Here the pattern is reversed: the magnetic moment $\mathbf{m}$ is extensive, whereas the magnetic field $\mathbf{B}$ is intensive!

How can we rationalize the unusual form of the magnetic work term?

Blundell makes an argument for this for the case of electric dipoles; I summarize it here. The relevant work term here is the electrical work $-\mathbf{p}_\text{E}\cdot\mathrm{d}\mathbf{E}$, with $\mathbf{p}_\text{E}$ the electric dipole moment and $\mathbf{E}$ the electric field.

  The potential energy of the dipole in the electric field is $-\mathbf{p}_\text{E}\cdot\mathbf{E}$. If the electric field changes, the potential energy changes by $\mathrm{d}(-\mathbf{p}_\text{E}\cdot\mathbf{E}) = -\mathbf{p}_\text{E}\cdot\mathrm{d}\mathbf{E}-\mathbf{E}\cdot\mathrm{d}\mathbf{p}_\text{E}$. However, the change in the electric field will also stretch the dipole, increasing its dipole moment and doing work $q\mathbf{E}\cdot\mathrm{d}\mathbf{l} = \mathbf{E}\cdot\mathrm{d}\mathbf{p}_\text{E}$, so the net work supplied to the system is $-\mathbf{p}_\text{E}\cdot\mathrm{d}\mathbf{E}$.

I am somewhat skeptical of this argument. It seems that I could repeat the argument for other types of work---say, $PV$ work---and conclude that I should also have a $V\mathrm{d}P$ term in my energy expression.

Is this argument correct? If it is, why isn't there a $V\mathrm{d}P$ work term in the first law?
What are the conditions under which this argument holds? Do the generalized force and generalized displacement have to interact with each other in a particular manner?

It also seems to me to be of limited applicability, because the convenient cancellation of magnetic-dipole and electric-dipole terms are not replicable for other, more complicated interactions.

Is there a general, methodical approach for identifying the form of the terms in the first law for arbitrary types of work?


texts: Strength of weak acids and bases: Is methane better base than ammonia?

texts:
$\mathrm{p}K_\mathrm{a}$ of methane is $\sim 50$ and that of ammonia is $\sim 37,$ thus ammonia is a better acid than methane, which implies methane is a better base than ammonia.

But I don't see how: methane doesn't have any lone pair of electron, neither it has any $\ce{OH-}.$ How is it possible?


texts: Second electron affinity of sulfur and oxygen

texts:
Why is the second electron affinity of oxygen greater than that of sulfur?
I think it should be like- second electron gain enthalpy of oxygen should be greater than the sulfur but electron affinity should be less than sulfur.


texts: Is it possible to predict the color of the flame test result based on the element's structure?

texts: The flame test is quite simple to do and very useful on the chemistry world, but to understand what your results mean you need to know previously a range variety of element-color relations. So, since the wavelength of the photon emitted reliess on the quantum jump done, I was wondering if, somehow, is it possible to make a fairly certain prediction of the results, based on the compound's structure. If someone knows a relation, it would be very useful.


texts: Can benzene undergo Diels–Alder reactions?

texts: I was reading about the Diels–Alder reaction and wondered that since benzene also consists of two conjugated double bonds, then should it also undergo Diels–Alder reactions? If not, then why not?


texts: What is the oxidation state of aluminium in NaAlO₂?

texts: I guess that sodium loses an electron so has an oxidation state of +1 and that oxygen has an oxidation state of −2. But what oxidation state does the aluminium atom have in sodium aluminate ($\ce{NaAlO2}$)?


texts: Copper Chloride: neutralizing and disposal

texts:
I plan on etching some PCBs with hydrochloric acid and hydrogen peroxide, which will therefore produce some kind of copper chloride (green color) which is highly toxic if released into the environnement (it may be useful as an herbicide, but I don't have any garden right now).

While cupric acid (obtained from hydrochloric acid, hydrogen peroxide and some PCBs etching) may be bubbled with air/oxygen to re-activate it to etch again other PCBs I'm not sure this may what I want and I seek suggestions in case I need to dispose of this solution.

Basically I heard (though none were actually on chemistry sites, except the 1st one):

Acid/Base neutralization: pour some baking soda to take care of the chloride
Pour some alluminium balls to get back some of the copper (didn't really understand how this works)
Copper electrolysis: basically get solid copper at the cathode, creating gaz at the anode and leaving (?) some residues that can be neutralized with baking soda (?)

Any insights on this? I think once the copper and chloride are taken care of, it shouldn't pose a huge problem to pour it down the drain or leave it outside to evaporate.

Specifically:

Which metal should I choose for the anode / cathode ? In the first source it speaks about reactivity (and since copper is less reactive than hydrogen, copper is produced at the cathode). No idea about the metal I should use though.
Would adding alluminium balls into the solution help make it more "eco-friendly" ?
Any other suggestion is welcome

Sources:

Electrolysis
How to etch PCBS - see comments
Recovery of copper using electrolysis


texts: Did the finding of the electron from cathode rays/ oil drop experiment at least temporarily throw Dalton's Atomic theory "out the window"?

texts: Because chemists learned that the atom was divisible, did Dalton's theory get any criticism or did they just adjust the theory to fit the new idea?


texts: Why is p-toluidine more basic than m-toluidine?

texts:
https://en.wikipedia.org/wiki/Toluidine

In m-toluidine the $\ce{CH3}$ group is closer to $\ce{N}$ so shouldn't that increase the electron density on $\ce{N}$ and make it a stronger base?


texts: I've been looking at the MO:s of different molecules in Avogadro, fascinated by their magnificent geometries. But how is one supposed to interpret them, so as to understand their reactivity? What are the first interesting things one should note when looking at the MO:s of different molecules? Interesting patterns to recognize? There is a lot of technical information on MO theory but not much info on how to interpret them intuitively. Any other sources or books I should read?


texts: Why is vulcanization called "vulcanization"?

texts: I know it might sound a dumb question but whenever I come across a note on importance of vulcanization I get stuck as to the meaning of the term and why it was adopted.


texts: Ionic compounds and van der Waals forces

texts:
I'm having trouble understanding exactly what intermolecular forces occur in ionic compounds.

What I understand is that ionic compounds are held together by electrostatic interactions between opposite charged ions and that they aren't "finite" in the way covalent molecules are, and therefore they do not have intermolecular forces.

However, while my textbook says that only covalent molecules have van der Waals forces, my professor said that all compounds, even ionic compounds have London dispersion interactions.

Isn't London dispersion a van der Waals force? How does that work?


texts: What happens at the inert anode in an electrolytic cell?

texts:
Recently I did an experiment using graphite as the anode and iron as the cathode for an electrolytic cell. I tried plating different metals such as copper, nickel, and zinc with CuSO4, NiSO4, and ZnSO4 respectively. I know that normally when the anode is made from the same material as the metal being used for plating, the anode is decomposed. What I am wondering is what happens at the anode when it is made of an inert material like graphite? Is the SO4 ion oxidized there, what does it become?
During the experiment, I have also observed bubbles forming at the anode, and I hypothesized that it may be oxygen from the electrolysis of water, but I had no way to be sure.


texts: Compare reactivity of carbocations and stability of carbanions, radicals, and carbocations

texts:
For ranking the carbocations in the image above,
I thought of taking the approach that the 1st molecule, the secondary carbocation was the most reactive because it has no electron donating group, then the carbocation with a terminal NH2 because nitrogen has an electron donating group, then the tertiary carbocation, and lastly the last carbocation has resonance making it very stable and less reactive. Is this the correct train of thought?


texts: What causes the anti-siccative effect of soot (amorphous carbon) as a pigment in oil paints?

texts:
Oil paint containing carbon black (soot, charcoal) pigment is known to polymerize ("dry") a lot slower than if it has other pigments. I understand this is not just due to the absence of pigments which are themselves siccatives (drying agents), but is also a direct "slowing" effect of the carbon black in the paint. The pigment supplier Kremer Pigmente confirms that it is a "slow drier", and the book "Artists' pigments, c. 1600-1835" by Rosamond D. Harley indicates:

  They [authors on the matter] invariably state that a drier should be added to it to accelerate its exceptionally slow drying time.

What is the nature of this effect? Why does carbon black slow the drying of oil paints?


texts:
Question:

Balance the following redox reaction:

  $$\ce{FeS2 + O2 -> Fe2O3 + SO2}$$

My Efforts:

I tried balancing with oxidation number method.

First of all i determined the oxidation state as follows:
$$\ce{Fe^{(2)}S2^{(-1)} + O2^{(0)} -> Fe2^{(3)}O3^{(-2)} + S^{(4)}O2^{(-2)} }$$

Here, all the element are either oxidized or reduced, so how to move ahead?

I tried balancing with Half reaction method.

$$\ce{Fe^{(2)} -> Fe2^{(3)}} \text Oxidation$$
$$\ce{S2^{(-1)} -> 2S^{(4)} } \text Oxidation$$
$$\ce{O2^{(0)} -> 2O^{(-2)}} \text Reduction$$

Same here, how to move ahead?

P.S. Oxidation state are mentioned in the brackets. Correct me if i am wrong anywhere.


texts:
What will be the cost efficient and high yielding method of synthesis for 1-bromobutane?

I can react butanol with $\ce{HBr}$ but I am worried butanol is not present at the moment in lab. But I need to hurry and make bromobutane.


texts: Extraction of hydrogen and oxygen from water

texts:
The apparatus that I am using is a glass container, with two electrodes,two glass cylinders, water, and a battery. In the glass container will be filled with water and two electrodes kept inside the glass cylinder and then dipped in water.

The two electrodes are then connected with the positive and negative terminals of the battery and the container is sealed.  As the current is started the water will be separated into hydrogen and oxygen. After extraction of the gas, the two gases are passed separately.

In this process, will the hydrogen gas start burning immediately as soon as produced? If yes, then what to do to make it pass without burning?  The separated gas is passed through glass pipes, will the extraction work properly?