texts: Factors that influence the kinetics of an irreversible exothermic reaction

texts:
I'm trying to understand what are the main factors that influence the reaction rate of an irreversible exothermic reaction.

I think these could be the main factors:

chemical nature of the reagents and their concentration;
nature of the solution (homogeneous or heterogeneous)
presence of catalysts
temperature.

(Let me know if I missed some factors or added one or two that had nothing to do with what I'm looking for.)

But I struggle understanding how the temperature influences an exothermic reaction. I can't use Le Chatelier's principle since the reaction is not reversible, so how do I know what is the effect of (for example) an increased temperature on such reaction?

I'm prone to think that an increased temperature will bring more products, but then again I'm not so sure since is an irreversible reaction.


texts:
I did total digestion on a $\pu{0.05 g}$ sample and had a final volume of $\pu{10 mL}$ once it was digested. I then took $\pu{5 mL}$ of this $\pu{10 mL}$ solution and diluted it to $\pu{10 mL}$ with water for ICP analysis.
The ICP gives a concentration of $\pu{1.5E-3 mg L^-1}.$ I haven't accounted for the dilution factor yet. Would it be $\pu{10.00 mL}/(\pu{0.05 g}) = \pu{200 mL g^-1}$ and then   $\pu{10 mL}/(\pu{5 mL}) = 2,$ so the overall dilution factor would be $200\times 2 = 400?$
So the actual concentration would be $400\times\pu{1.5E-3 mg L^-1} = \pu{0.6 mg L^-1}?$


texts:
How is this formula derived? What does it mean; what is the use of this formula?

I know that at infinite dilution, ionization extent should be very high because of Le Chatlier's principle.

But I'm not seeing how this formula is derived and its significance in actual chemistry. I tried rewriting the formula as:

$\mathrm{\frac{K_a}{K_a+\sqrt{K_w}} \cdot 100\%}$

But this isn't elucidating where the formula came from or its significance.

I could also rewrite the formula as this for the hypothetical acid, $\ce{HA}$:

$\mathrm{\frac{K_a}{K_a+\sqrt{K_w}} = \frac{\frac{[H_3O^+][A^-]}{[HA]}}{1.0 \cdot 10^{-7}+\frac{[H_3O^+][A^-]}{[HA]}}}$

I think the trouble I'm having is defining maximum ionization extent. For example, I know that in general ionization extent is defined as (where x is the concentration of the derived species - i.e. $\ce{[A^{-}]}$ for the hypothetical acid $\ce{HA}$ and $\ce{M_{i}}$ the initial molarity of the hypothetical acid.

$\mathrm{\frac{x}{M_{i}}}=\text{ionization extent}$

I have a feeling that the $1.0*10^{-7}$ term refers to the concentration of one of the products of the auto-ionization of pure water at 25 degrees Celsius. This makes sense because at infinite dilution the concentration of solute should be negligible (=0).

Upon further thought ...


texts: Peak Wavelength of Emission Spectrum of a Flame vs. Actual Flame Temperature

texts:
I am looking at a lab test of two variants of mixed hydrocarbon gas (57.8% $H_2$, 16.9% $N_2$, 12.4% $CH_4$, 1.11% water vapor, and 11.8% "unknown" gases)  burning in oxygen which shows a discontinous emission spectra. The authors are claiming that since their graph shows a peak wavelength at 471 nm, the gas therefore has a peak flame temperature at 6132 K / 5859 °C / 10578 °F according to Wien's Displacement Law, which is absurdly higher than the adiabatic flame temperature of any known hydrocarbon gas.

Now, I know that the spikes shown correspond to the $C_2$ and $CH$ Swan Band. Can someone provide a detailed explanation as to why this is not an accurate measurement of flame temperature?

I should also mention the graph only ranges from 200 nm to 1100 nm, and that they fitted the emission spectrum to a blackbody curve. Could the peak wavelength actually be further into the infrared spectrum? Is fitting the emission spectrum to a blackbody curve even appropriate for a non-blackbody emitter such as a flame?


texts: What signal is measured at the detector in atomic absorption spectroscopy?

texts:
I understand that a hollow-cathode lamp (HCL) with a specific target is used to excite the sample. The atoms in the sample absorbs the photons and re-emits at the same wavelength and the signals are measured by the detector.
What about the signal from the source? Let's say only 20% of the energy from the source are being absorbed, wouldn't the other 80% also travel through the flame to the detector?


texts: Difference between HCD and CID collision induced dissociations?

texts:
With the Thermo-Fisher Fusion Orbitrap mass spectrometer I can do both CID (collision-induced dissociation) and HCD (higher energy C trap dissociation) collision-induced dissociation studies.

When I apply HCD on inorganic molecules I observe more fragmentation products than with just CID suggesting multiple fragmentation steps. However I don't get why physically this is possible.

Is HCD design to keep the fragmentation products in the trap so that they collide many times with the inert gas?

EDIT: according to this manual found on the Termo Fisher website:

  HCD tends to produce EI-like fragmentation
  and records ions from multiple steps of collision as seen
  in Figure 3.

https://assets.thermofisher.com/TFS-Assets/CMD/Application-Notes/AN-540-LC-MS-Small-Molecule-Characterization-AN63396-EN.pdf

And according to a post found in research-gate:

  In beam type CID ("HCD") multiple collisions with a collison gas take place under an elevated pressure regime. Ions can be activated multiply, which results in richer spectra compared to resonance type CID ("CID"). In resonance type activation, only the precursor ion is activated - in beam type CID also the fragments (collision gas).

https://www.researchgate.net/post/Why_sometimes_there_are_a-ions_when_you_perform_HCD_fragmentation_for_peptides_on_Q-exactive_plus

From the answer given here the reason of a richer spectra is that:

  The reason HCD gives you more fragment ions is that ions do not have time to equilibrate.

So, do I have more fragments when I apply HCD because:
1) I have multiple collisions(multiple activation)where also the fragments collides?
2) It's a non-equilibrium process, so bonds are broken independently of the strength?
3) both?


texts: Is shielding of electrons really best described as shielding or is it really Coulombic repulsion between electrons?

texts:
For example, take the 2s electron in lithium - is the reason that it's ionisation energy is lower than would be expected if "shielding" didn't occur at all because the 1s electrons shield the attractive coulombic force from the nucleus or because the 2s electron is repelled by the 1s electrons? Is it possibly a mixture of the two?

To me, shielding seems to be a model to help conceptualize what is actually happening; am I wrong about this? What is actually going on?


texts:
I want to know how the following sigma bond strength values are calculated.
Like S-S = 1.0, S-P=1.71 And P-P=3.0.

How these 1.0, 1.71, 3.0 came?


texts: Will cyclopenta-2,4-dienecarbaldehyde undergo aldol condensation or cannizzaro reaction?

texts:
The following question was given in an exam.Which of the following undergo aldol condensation ?

Given answer :  a,b,c

My answer: b,c

My Logic :

Cyclopenta-2,4-dienecarbaldehyde(1) on reaction with a base gives carbanion whose resonance structures are 1a to 1e as shown below.This anion is an aromatic anion .Being stable ,tis aromatic anion now in oresence of base would undergo Cannizaro Reaction to give 3 and 4.

My question is, will cyclopenta-2,4-dienecarbaldehyde  undergo aldol condensation?


texts: Removing unreacted Mg metal in a Grignard reaction

texts:
A Grignard reagant was prepared from an alkyl halide and magnesium chips, then reacted with a ketone. The resulting solution has been stirring for a few days at low temperature (0-5°C). It's now time to transfer the reaction solution slowly to a vessel containing an acid quench. My problem is the unreacted magnesium chips (smaller than when we started, of course) have settled, and are plugging the tubing and stopper valve.

What solvents could I use to flush the magnesium through, breaking it up, and possibly dissolve it? This can't be added to the reaction solution (the Drain-O method), but only through the tubing itself. Obviously water is a bad idea. Any insights?


texts: How to balance a redox equation in molecular form?

texts:
I've spent a while trying to balance this equation in molecular form with no success.

$$\ce{Cu + HNO3 -> Cu(NO3)2 + 2NO + H2O}$$

I need to find the coefficient of HNO3, which is 8. However, this was my attempt:

$$\ce{Cu^0 + H + (NO3)- -> Cu^2 + 2(NO3)- + 2NO-2 + H2O }$$

$$\ce{Cu^0 -> Cu^2 + 2e- }$$
$$\ce{2x (NO3- + 2H^1 + e--> 2NO^0 + H2O)}$$

$$\ce{Cu^0 + 4H+ +2NO3- -> Cu^2+ + 4NO^0 + 2H2O + NO3^-}$$

Image of process: http://imgur.com/LysN7FZ.png

NO3 is the spectator polyatomic ion I left out during my balancing. I have no idea whether I did it right and where to go from here.
Thanks!


texts: Silver "polish" with aluminum foil left a hard yellow coat

texts:
I cleaned my silver teapot with the aluminum foil-baking soda-hot water method.
Usually this works well on my silver plated flatware.
However,  this time it left a hard yellowish coating.  I was only able to remove it by very strenuous manual polishing with a silver polish paste and when desperate, I even used toothpaste. The trade off was that it could scratch very finely,  but that was preferable to the yellow.
Now I'm afraid to use this method on unusual pieces.
--> How can I prevent this from happening again?
Are there kinds of silver and metal combinations that produce this reaction?
Is there an easier way to remove it?
Thanks!


texts: Why are d(xy),d(yz) and d(xz) orbitals involved in d³s hybridisation?

texts:
Shouldn't d(x²-y²) dxy and dz² orbitals participate? Since this corressponds to the best case overlap?

What factors decide the participating orbitals in hybridisation?

P.S I am well versed with the concepts of CFT and VBT but know little to nothing about other theories lik MOT and Group theory.


texts: Knowing that CI is variational for any basis set, why is coupled-cluster variational in the full correlation limit?

texts:
This is the question asked in Martin's comment to my answer to: Why is Coupled Cluster not variational?

In the comment I was also asked to provide a publication as a reference:


texts: What will form when Dihalides or Trihalides or Polyhalides react with Magnesium?

texts:
I know that
"R-X + Mg" gives RMgX.

I want to ask if the Halide is Poly, then How's the formation of Grignard take place?

For example.
If 1,4 - Dibromobutane react with Mg, then what will be the product?


texts: A question on approximate equation for 2 gases and liquefiable nature

texts:
While learning the gaseous state I stumbled upon a question which I don't think has correct answer according to my booklet.
Question:The following equations are occasionally used for approximate calculations on gasses:
Gas(X): $PV_{m}=RT(1+\frac{b}{V_{m}})$
Gas(Y):$P(V_{m}-b)=RT$
Where $V_{m}$ is molar volume, $R$ is universal gas constant, $T$ is temperature, $P$ is pressure, $b$ is van der Waal constant or volume correction term.<
 Assuming that gas(X) and (Y) actually obeyed above equation of state then what we can say about comparision of their liquefiabilities.
My answer: According to me neither of the gases would be liquefiable because they have pressure correction term $'a'$ missing so they wouldn't show any intermolecular force and hence their molecules couldn't come together to form liquid. According to my book it is given that gas(X) is more liquefiable than gas(Y) which seems unusual. Please tell what is the correct answer and thanks in advance!


texts: The source for the N-N bond dissociation energy of 240 kJ/mol in the table

texts:
Authoring an exam question, I made the mistake of taking a bond dissociation energy from a table I found on the internet. It comes in different styles, but is always labeled Table 7.1. It gives a bond dissociation energy of $\pu{240 kJ/mol}$ for the - admittedly uncommon - nitrogen:nitrogen single bond. A student was puzzled that the enthalpy of formation for hydrazine, estimated based on this value, was so far off from the experimental value; the student then found a value for the bond dissociation energy of $\pu{159 kJ/mol}$ in a more rigorous search.

The General Chemistry textbooks available to me from home have values close to $\pu{159 kJ/mol}$ (OpenStax Chemistry: $\pu{160 kJ/mol}$; Kotz 6th ed (2006): $\pu{163 kJ/mol}$; Radel (1994): $\pu{170 kJ/mol}$). I am not worried about the small differences - it depends which set of molecules containing $\ce{N-N}$ bonds was used, and a substructure search of commercially available compounds shows that there is quite a variety, with many having partial double-bond character (the following sample are 3 from the 100 or so just from Sigma Aldrich):

My question is: Where did Table 7.1 originate, and where did the value for $\ce{N-N}$ originate?

Here is a selection of links to variations of table 7.1, with the first example as picture:

https://wps.prenhall.com/wps/media/objects/4678/4790506/ch07_02.htm

https://www.chegg.com/homework-help/questions-and-answers/use-bond-dissociation-energies-table-calculate-approximate-h-kilojoules-reaction-acethylen-q27780023

https://www.chegg.com/homework-help/questions-and-answers/average-bond-dissociation-energies-d-kj-mol-h-h-4362-h-c-410-h-f-570a-h-ci-432a-h-br-3662--q36015212

https://cdn.clutchprep.com/problem_images/65691-36fd337a4e3e837c.png


texts: How does pH change during the electrolysis of water?

texts: How does the pH change during electrolysis of a water and  magnesium sulphate solution? Also, will this pH change happen every time? Does the pH change differently when there is just water in the anode and cathode?


texts: Ground state oxidation potential and Ionization potential from density functional theory (DFT)

texts:
Can someone please tell me how to calculate the ground state oxidation potential (GSOP)?

I understand that according to Koopmans' theorem, the negative of HOMO can be considered as the GSOP. Is there any other way to calculate GSOP?

Also, are GSOP and ionization potential same?


texts: Reaction of carboxylic acid with phosphorus trichloride

texts:
The reaction of carboxylic acid $\ce{RCOOH}$ with $\ce{PCl5}$/ $\ce{SOCl2}$ / $\ce{PCl3}$ yields an acyl chloride $\ce{RCOCl}$. With $\ce{PCl5}$ and $\ce{SOCl2}$ the reaction is quite simple utilizing one mole reactants and yielding products.
But in case of $\ce{PCl3}$ the balanced reaction is as follows:
$$\ce{3RCOOH + PCl3 -> 3RCOCl + H3PO3}$$
First i thought the reaction would proceed with PCl2− attacking the oxygen from which the oxygen-hydrogen bond cleavage happened but then I realized that it would form product OPCl which is not a real compound i suppose so i am stuck how would the reaction proceed
So what is the mechanism for this reaction?


texts: Can you use a photon's torque to change a molecule?

texts:
Can you use the torque of a photon to change bond angles, etc.? 11-Cis-Retinal to the all trans version, in  the eye, is a good illustration [1].

Note: This phenomenon can be observed by closing blinds, allowing the sun to shine through, you get light beams. If you blow a smoky material past it, you can observe this phenomenon of light.

References

Rego, L.; Dorney, K. M.; Brooks, N. J.; Nguyen, Q. L.; Liao, C.-T.; Román, J. S.; Couch, D. E.; Liu, A.; Pisanty, E.; Lewenstein, M.; et al. Generation of Extreme-Ultraviolet Beams with Time-Varying Orbital Angular Momentum. Science 2019, 364 (6447), eaaw9486. https://doi.org/10/gf4f6h.


texts: Mirror planes of symmetry in bicyclo[2.2.2]octane?

texts: One of the questions in my book has answer given as one mirror plane of symmetry perpendicular to the 3-fold rotation axis, but I think it has 3 more, each parallel to the 3-fold rotation axis as I have attempted to show below.


texts: Pourbaix diagram and the order of the species

texts:
Figure 1. Pourbaix diagram of iron (Source)

The line between $\ce{Fe}$ and $\ce{Fe^2+}$ is there because the potential $\ce{Fe/Fe^2+}$ is $\pu{-0.44 V}$. The same applies for $\ce{Fe^2+/Fe^3+}$ with $\pu{0.77 V}$. But $\ce{Fe/Fe^3+}$ is $\pu{-0.03 V}$, but it's not on the graph as a line.

How do I know which species have a line, and which don't? And if I'm drawing a graph, how do I know that I also shouldn't include this line?


texts: Is there a selective wet etch of Bi2O3 Bismuth Oxide?

texts:
I'm looking for a wet etch of Bismuth Oxide that does not etch $\ce{Bi}$ itself.

There are obviously chemicals that etch $\ce{Bi2O3}$, but $\ce{Bi}$ is pretty fragile, so almost everything I've found that can etch $\ce{Bi2O3}$ also etches Bi, and usually more rapidly than the $\ce{Bi2O3}$ itself.

However, someone recently mentioned to me in passing that there was a chemical that could do this, but they didn't remember what it was.

Searching Google, I found this, but that's RIE -- not wet etching.

I've also read about people using $\ce{H2}$ gas to reduce the oxide back to $\ce{Bi}$, but again, not wet etching.

Does anyone have any idea? I know it's a specific and uncommon question.


texts: What are the limitations of the Theorem of Corresponding states?

texts:
I recently came across the theorem of corresponding states, which states that all gases exhibit the same compressibility factor, under same reduced pressure and temperature (and also the critical compressibility factor). Thus:

$$Z=f(P_r,T_r,Zc)$$

where

$$Z=\frac{PV}{RT}$$

$$P_r=\frac{P}{P_c}$$
$$T_r=\frac{T}{T_c}$$

My question is, what are the limitations of this theorem? Can I consider it as an absolute truth, or is it just like any other gas law, being valid only within certain ranges and for certain acccuracies?


texts: What is the correct structure for trans-3,4-dichlorocyclopentene?

texts:
I have to draw the structure for trans-3,4-dichlorocyclopentene.

What position should I draw the double bond at? Should I draw it as molecule 2? Because there's a trans.

Or should I draw it as shown in molecule 1 because it didn't state?

I feel that molecule 2 in the diagram is correct. What do you think? Where are my mistakes?


texts:
I am trying to understand how a phosphate ion looks like using the VSEPR theory.

The phosphorus element has an atomic number of 15, and therefore it has a electron configuration as follow by the Aufbau principle.

$$\pu{1s2 2s2 2p6 3s2 3p3}$$

It needs to have one π-bond with one oxygen atoms and 4 σ-bonds with all of the 4 oxygen atoms, so it is hybridizing 4 orbitals to form some hybridized orbital and leaving one p orbitals around for the pi bond? How does that work?


texts: Understanding Chemical Potential (Li-ion)

texts:
Can anyone help me to understand what the "Chemical Potential" is? I can see that in batteries the electrical energy is stored as "chemical potential", according to this:

Li-ion batteries, Na-ion batteries, and Mg-ion batteries, reversibly
convert between electrical and chemical energy via redox reactions,
thus storing the energy as chemical potential in their electrodes.

So what is chemical potential? According to Wikipedia, it is defined as:

In thermodynamics, chemical potential, also known as partial molar
free energy, is a form of potential energy that can be absorbed or
released during a chemical reaction or phase transition

Which is quite straight forward, in a way. However, it doesn't really make me understanding it entirely, therefore I would like to ask if there is anyone that can help me understand this. I'm always trying to use analogies and therefore I would like to ask the following question:

Can the chemical potential be seen like the latent heat, where the
energy is stored as bonds and, in order to break the bonds, one needs
to add extra energy.

Or is it more complex than this? Please see below a sketch with what I imagine happens inside. Did I understand it right?

It's hard for me to understand what keeps the energy there. Any help counts!
Thank you!


texts: How to find the valence of transition elements?

texts:
Let's take Iron for example

As we can see there are 4 desolate electrons in normal state. Can you tell me which electron moves to make the valence 2 and then 3. We have learnt to find the valence only using the configuration formula.


texts: Why is estimation of sodium hydroxide more accurate with oxalic acid rather than with sulfuric acid or any other strong acid?


texts: Average bond energy of H−F and H−O hydrogen bonds

texts:
Which of the following hydrogen bonds (shown by the dotted line) has the highest average bond energy?
A) $\ce{F-H\bond{...}F}$
B) $\ce{F-H\bond{...}O}$

I am thinking the answer is $A$ since the covalently bonded F atom, being highly electronegative, would induce a high partially positive polarity on the H atom. But on the other side, the more electronegative atom F will form a stronger Hydrogen bond than the comparatively less electronegative O atom.
Any flaw in my reasoning?


texts: Reduction of a ketone in the presence of an aldehyde

texts:
An aldehyde group can easily be reduced to an alcohol using the mild reducing agent $\ce{NaBH4}$ at low temperature in the presence of a ketone group. This chemoselectivity is due to the fact that an aldehyde is less sterically hindered compared to a ketone, which makes it react faster than the ketone.

Is it possible, however, to chemoselectively reduce a ketone in the presence of an aldehyde using $\ce{NaBH4}$ as reducing agent?


texts: Addition reaction of hydroiodic acid to 2-bromo-3-chloro-2-butene

texts:
How can the major product of the addition reaction of 2-bromo-3-chloro-2-butene with hydroiodic acid be predicted, since Markovnikov's rule fails to distinguish it?

$$\ce{H3C-C(Cl)=C(Br)-CH3~+~HI~->~?}$$


texts: To denote standard state like enthalpy of formation in standard state, or change in Gibbs free energy in standard state, we use a degree-like symbol above the $G$ as in $\Delta G^0$. How should I refer to this superscript in spoken language?


texts: How can I solubilize fragrance oil into polyvinyl acetate/clear glue?

texts:
I'm a high school student who makes slime for fun, using polyvinyl acetate (PVA) glue and borax as my main ingredients.
Earlier, I had the idea of adding fragrance oils to clear glue. However, because they aren't soluble, it makes the whole thing cloudy. I tried using a fragrance oil solubilizer, polysorbate 20, however I soon found out that it wasn't soluble in it the clear glue either!
This hit me as odd, since polysorbate 20 is perfectly soluble in water. I'm trying to find out what exactly makes up clear glue, but all I know is that it contains PVA. I read somewhere that since PVA isn't super soluble in water, it's the reason why white glue is white. In addition, I also read that clear glue might be solvent based altogether. I'm not sure if any of this is actually true, but if anyone has insight on this it would be really helpful!
Should I be trying a different solubilizer, or am I missing a crucial step when I mix the two ingredients? Or is the issue not even related to solubility altogether?
Here is a short list of what I have tried and what happened:

Experiment
Observation

Mixing the oil directly with the glue
Glue mixture ends up cloudy

Mixing the oil into the polysorbate 20, and then adding water
Water mixture ends up clear

Mixing the above water mixture into clear glue
Glue mixture ends up cloudy

Mixing polysorbate 20 directly into clear glue
Glue mixture ends up cloudy

Mixing water directly into clear glue
Glue mixture ends up clear

Some other information you might find helpful:

I use Darice clear school glue.
All of the ingredients on their own are already clear.
I have run each of those above trials multiple times and have gotten the same result each time.


texts: How do you calculate enthalpy for a reaction at non-standard conditions?

texts:
I understand how to calculate the change in enthalpy and entropy for a reaction in standard conditions, but is there a way to calculate these values at non-standard conditions?

Also, is there any way that a reaction with positive change in gibbs free energy will occur?


texts: Why are acids and bases are defined as both donors and acceptors of species in the acid-base theories?

texts:
So, a Brønsted-Lowry acid is a proton donor, and a Brønsted-Lowry base is a proton acceptor. On the other hand, a Lewis acid is an electron pair acceptor, and a Lewis base is an electron pair donor.

Why is it that in these acid-base theories, acids and bases are defined as both donors and acceptors of species? Or is there a part of acid-base theory I don't quite understand?


texts: Is benzylamine $\ce{C6H5CH2NH2}$ an aromatic or aliphatic amine? I've tried searching for it however different sources have conflicting information.


texts:
To a $\pu{1L}$ flask, we add $\pu{4.1900 g}$ ($\pu{0.01001 mol}$) of $\ce{Ag3PO4}$, then fill it up with water. Knowing the following constants, we are asked to find the concentration of all species in solution:

  $K_\mathrm{s}(\ce{Ag3PO4})=2.7\cdot 10^{-18}$,
  $K_\mathrm{s}(\ce{AgOH})=4.0\cdot 10^{-16}$,
  $K_\mathrm{a1}=10^{-2}$,
  $K_\mathrm{a2}=10^{-7}$,
  $K_\mathrm{a3}=10^{-12}$

  $\ce{Ag2O}$ does not form.

By analyzing the problem, we notice that the formation of $\ce{AgOH}$ is more favorable:

$$\ce{Ag3PO4 + 3H2O <=> 3AgOH + H3PO4}, \\
K=\frac{K_\mathrm{s}(\ce{Ag3PO4})\cdot K_\mathrm{w}^3}{K_\mathrm{s}(\ce{AgOH})^3\cdot K_\mathrm{a1}\cdot K_\mathrm{a2}\cdot K_\mathrm{a3}} = 4.2\cdot10^7$$

Therefore, we start with $[\ce{H3PO4}]_0 = \pu{0.01001 mol//dm^3}$.

The equilibria we work with are:

\begin{align}
\ce{AgOH &<=> Ag+ + HO-}\\
\ce{H3PO4 + 3HO- &-> PO4^{3-} + 3H2O}\\
\ce{PO4^{3-} + H2O &<=> HPO4^{2-} + HO-}
\end{align}

The $\ce{HO-}$ formed from the insoluble salt is consumed in its entirety towards the formation of $\ce{PO4^{3-}}$, from which a fraction dissociates in water to form $\ce{HPO4^{2-}}$ and $\ce{HO-}$. Therefore, the principal conservation of mass law is:

$$[\ce{Ag+}]=3\ce{[PO4^{3-}]}+3\ce{[HPO4^{2-}]}$$

How do I tackle this problem in a more elegant manner? The equation on the top is solvable; but by looking at their results, we can see they do not fit at all:
$[\ce{Ag+}]=6.5\cdot10^{-14}$, $[\ce{HO-}]=6.2\cdot10^{-3}$, $[\ce{PO4^{3-}}]=3.8\cdot10^{-3}$

I'm thinking that, considering such a small concentration of $\ce{Ag+}$ compared to $\ce{PO4^{3-}}$, we might still have some $\ce{Ag3PO4}$ undissolved.

But this doesn't seem to make sense since the formation of $\ce{AgOH}$ is a lot more favorable, as seen from the value of $K$.


texts: In many sites, I see that they put $\ce{O}$ in the middle, but our teacher said that we should put $\ce{O}$ near the extremity. Which is the best way?


texts: Do sugar alcohols have the potential to get a person drunk?

texts: From what I understand is ingesting high amounts of sugar alcohols can lead to various effects such as abdominal pain and diarrhea, my question is, is there a certain amount of sugar alcohol if ingested cause drunkenness (even if it causes a person to be in a critical state or death) ?


texts: How can melting point equal freezing point?

texts:
I don't understand how the freezing point of a substance is the same temperature as the melting point of the same substance.

For example, if liquid water freezes at 0 °C how can ice also melts at 0 °C?


texts: Le Châtelier’s Principle and Addition of Water

texts: With regards to gas volume, Le Châtelier’s principle predicts that an increase in the volume of the container causes the system to favor the side of the reaction that produces more moles of gas. However, would this principle apply equally well to an aqueous system, at equilibrium, that has now had water added to it? That would be analogous to expanding the volume of a gaseous system, wouldn’t it? Would adding water to an aqueous system at equilibrium affect the position of equilibrium at all?


texts: How is Electrode Potential Developed on Inert Electrode?

texts: How does redox couple develop its potential if electrode isn't the part of the redox system like platinum in SHE or Cl2/Cl- in water solution for example? Usually it is discussed how electrode develops its potential when it isn't inert like Cu/Cu2+ system when copper electrode itself is important for developing potential. What about inert electrodes?


texts: Is it possible to apply reaction progress kinetic analysis on non catalytic reactions?

texts: I was wondering if anyone familiar with reaction progress kinetic analysis knows if it is possible to apply the method on non catalytic reactions, and if so provide a few references with relevant examples.


texts: Why does calcium carbonate decompose into calcium oxide?

texts:
Why does calcium carbonate, when heated strongly, decompose into calcium oxide and carbon dioxide?

What is the mechanism? Can someone illustrate the means by which this happens? What bonds/associations are broken?

I'm guessing that one of the calcium ion has a strong intermolecular association with one of the partially negative oxygens, and this changes the bond character of the carbonate ion. Upon applying heat, this bond remains while carbon dioxide is off-gassed.

In other words, the positive charge on the calcium ion isolates the electron density to the nearest oxygen atom on the carbonate ion. This isolation of electron density away from the carbon and toward the calcium weakens the oxygen-carbon bond while strengthening the calcium ion-oxygen intermolecular association force.


texts: diborane fragment orbitals energy of dihydrogen

texts:
I want to ask a question about the fragment orbitals of the $\ce{B2H6}$ system, specifically when I combine the $\ce{B2H4}$ with the $\ce{H2}$ fragments.

I am halfway through my inorganic chemistry molecular orbitals course and today we were discussing the application of MO theory in figuring out the structure of $\ce{B2H6}$.

So far, I have been able to combine the two $\ce{B2H4}$ FOs but I am struggling to justify the placement of the $\ce{H-H}$ FO to complete the task.

So far, I've been given this diagram.

And the professor said the following:

  the $\ce{b2}$ orbitals are non-bonding FOs so it does has nothing to bond with in the $\ce{B2H6}$ molecule. We assume the H $\ce{1s}$ orbital is the reference and line up the hydrogen $\ce{H-H}$ FO with the $\ce{b2}$ FO, giving the symmetry groups $\ce{ag}$ and $\ce{b_{3u}}$ respectively.

I understand the use of Hydrogen as a reference and the assignment of point groups in this situation, but I can't seem to work out why Hydrogen lines up with the $\ce{b2}$ FOs and not, for instance, with the $\ce{a1}$ FOs.

I've searched across the internet for the past day and failed to find any conclusive answer.

Why is $\ce{H-H}$ given to have the same energy as the $\ce{b2}$ FOs of $\ce{B2H4}$?


texts: Why do you not need sun protection whe the UV index is 3?

texts:
In Australia, they recommend sun protection when the UV index is above 3.
Why is this? Surely whenever it's above 0 there are still UV rays hitting your skin?
Would 10 minutes in the sun with a UV index of 6 be the same as 20 minutes in the sun with a UV index of 3? If so, surely 10 minutes in a UV 6 index would be bad, and therefore 20 minutes in UV index 3 would also be bad?


texts: How to identify cis and trans in conformers of cyclo hexane.i know that there are two positions axial and equatorial but using this data how to identify cis or trans? Also why are functional groups in equatorial positions more stable?


texts: Chemical Kinetics- Net Number of Particles

texts:
I have a box of 5 types of particles, $A$, $B$, $C$, $x$ and $y$. They react in the following way.

$\ce{$A$ + $B$ -> $C$ + $x$}$

and

$\ce{$C$ + $y$ -> $A$ + $B$}$

If only the first reaction was happening then $N(C) = k \cdot N(A)N(B)$. Here $N(I)$ is the number of particles of $I$ in the box.
Can I write the total number of $C$ in the box as $\text{number of $C$ created} - \text{number of $C$ destroyed} = N(C) = k \cdot N(A)N(B) - k' \cdot N(C)N(y)$?


texts: Do species with more unpaired electrons attract magnets more strongly than those with fewer unpaired electrons?

texts:
My lecture notes state that you can distinguish between high spin and low spin complexes by their magnetic properties.

This thought came to me: consider two octahedral crystal fields with a d7 electronic configuration, one in the high spin state and the other in the low spin state. The complex in the high spin state has two unpaired electrons, whereas the complex in the low spin state has 1 unpaired electron. Both complexes are therefore paramagnetic and hence attract magnets. Does the former attract magnets more strongly as it has more unpaired electrons?


texts: Heats of combustion and stability of rings

texts:
Which isomer would have the largest heat of combustion?
A) Propylcyclopropane
B) Ethylcyclobutane
C) Methylcyclopentane
D) Cyclohexane
E) Since they are all isomers, all would have the same heat of combustion.

Can anyone explain why?
If you think about it, without having the data of the heat of combustion of each type of bond, you can't really answer this question. I know that cyclopropane has a higher heat of combustion per bond than cyclobutane. However, that, in my sense of viewing the problem, does not prevent the fact ethylcyclobutane could have a higher heat of combustion as it is a cycloalkane with 4 bonds rather than 3.
It could happen that the three bonds in cyclopropane and the three bonds in the alkyl branch are lower in energy that the four bonds in cyclobutane and the two bonds in the alkyl branch.
For example:
Let's say a cyclopropane C−C bond is 10 J.
A cyclobutane C−C bond is 9.5 J.
A regular alkane bond is 8 J.
For propylcyclopropane:
Total energy is 54 J
For ethylcyclobutane:
Total energy is 54 J
The same! I know this sounds really simplistic and dumb, but I just don't understand how you can assume the answer is A.
How do you analyze this situation? Please help.


texts: Does freezing point depression depend on the charge of the solvated ions?

texts:
Assuming an ideal solution, which of these 0.10 M solutions would have the least freezing point depression?
$\ce{HCl}$
$\ce{NaBr}$
$\ce{KNO3}$
$\ce{MgSO4}$

They all produce solutions with two ions per formula unit, but the correct answer is somehow supposed to be $\ce{MgSO_4}$. How is this? I don't think it can be due to the weak basicity of sulfate; that should in fact increase the ions present and have an even greater freezing point depression.


texts: Is benzyl chloride or allyl chloride more reactive?

texts: What compound is more reactive, benzyl chloride [(chloromethyl)benzene] or allyl chloride (3-chloroprop-1-ene)? I know that both have a higher reactivity than alkyl and aryl chlorides.


texts: Is there a method to selectively cleave the C-C bond between a benzyl group (-CH2Ph) and a linear or cyclic alkane? Can this be done under standard conditions with somewhat widely available reagents? Can the benzyl group be forced out if it is under significant steric clash when it is attached?


texts: Question during radius of gyration calculation from XYZ trajectoris of atoms

texts:
I have molecular dynamic simulation result of 100 polymer molecules (liquid), and I'm trying to calculate the radius of gyration using atomistic mass, molecular mass, and xyz coordinate of atoms. I'm trying to follow what LAMMPS is doing to calculate the radius of gyration $R_\text{g}$:

$$R_\text{g}^2 = \frac{1}{M} \sum_i m_i (r_i - r_\text{cm})^2$$

Here is my step:

1) Calculate distance from each atom to COM of molecule, for X, Y, and Z direction.

2) Square the distances (for each X, Y, and Z)

3) Multiply distances (for each X, Y, and Z) by atomic mass for each atom

4) Repeat 1~3 for all atoms of corresponding molecule and sum up the values.

5) Divide the value from 4) by molecular mass

6) Now we have the square of the radius of gyration, but it has 3 components (X,Y,Z). Sum the three components together (they are already squared) and then square root. This would be a Rg of single molecule.

7) Perform 1~6 for all other molecules. (and average in the future)

My calculation result is different from what I get from LAMMPS calculation result. Which part of my script is wrong? I'm not sure what is wrong with my calculation process. Do I need to exclude mass, only consider Ri-Rcom?


texts: Adsorption and distribution chromatography difference?

texts: Well, yes, that is the question. What is the difference between the absorption chromatography and distribution chromatography?


texts: Will the electrolyte surface become charged if one electrode is raised out of solution?

texts:
What would the potential distribution be if I were to immerse a single inert (graphite) electrode in an aqueous solution with good ionic conductivity and hold it at a high (ca. $\pu{24V}$) potential vs. an electrode that would remain in the air above the solution's surface?

I don't expect anything to happen at the immersed electrode interface because the solution should remain equipotential.

But, what about the air-water interface? Would the electric field induce a surface charge?


texts: Can atomic partial charges be measured in molecules experimentally?

texts:
Can we measure atomic partial charges in molecules experimentally? The charge of isolated ions can be measured, but when atoms are part of a molecule, the case is much more difficult. We do not really know where one atom starts and where another one stops (the atomic radii are diffuse). So I am inclined to say that partial charges must be based on theoretical concepts, such as the Mulliken population analysis (or a range of other methods), or be derived (estimated) from measurables such as dipole moment.

However, is it possible to probe molecules at the atomic level, using STM, TEM, or some other electron probing technique, and get the partial charges that way, perhaps based on electron-electron repulsions? Still, it seems to me, that the border between the atoms need to be properly defined in order to get the partial charges.

According to the Wikipedia page "Partial charge", several experimental techniques can be used to estimate the partial charge, e.g. XPS, NMR, EPR, UV/vis, with more. But do these techniques measure something which is a direct result of the effect of partial charge, or is some other physical observable measured, from which the partial charges are "guessed"? For example, using XPS to get the kinetic energy of the photoelectron seems like a "direct" measurements (although I know that what the detector sees is not really the kinetic energy, but something with which the kinetic energy correlates: calibration is needed). However, the idea of partial charge seems to be somewhat vague. Numerical values of partial charges depend on the definition of where one atom starts and where another ends, which is an abstract concept: this border cannot be observed or measured.

Another issue that comes to mind, is that the partial charge is not necessarily uniformly distributed around each atom, but will depend on bonds, lone pairs, interactions with other molecules, etc.


texts: Are there any sodium salts that are insoluble in water?

texts: Are there any sodium salts (e.g. NaCl) that are insoluble in water? If so, what are their approximate $K_\mathrm{sp}$ values?


texts: Do noble gasses besides Helium form diatomic molecules at low temperatures?

texts: I know that at extremely low temperatures (mK and lower), Helium can form diatomic molecules. Do the other noble gasses also form molecules at extremely low temperatures?


texts: Why do atoms get smaller moving left to right on a periodic table?

texts:
I get that it's because of the increase number of protons, but I still don't understand the concept. When you move left to right on a periodic table, the protons increase at the same rate as the electrons. In fact,  the number of electrons end up being the same as the number of protons, no matter how far you are across a period (unless it's an ion).

So shouldn't the attractive force of the nucleus and the forces of electron-electron repulsion be cancelling out due to the equal number of protons and electrons in an atom? Or is it because protons have a greater force of attraction compared to the repulsion force between electrons?


texts: Is there a bifurcation node in the potential energy as a function of reaction progress equation of chemical reactions?

texts:
I originally posted a similar question on math.stackexchange.com, but I believe I might have a better chance of having my question answered here after giving it some time.

I was thinking about the activation energy of chemical reactions, and I was wondering if there exists a bifurcation node somewhere in the transition state.   I'm wondering about this image:

Here's what's bugging me about it. I don't have an actual equation to the curve, so I can't necessarily do a quantitative analysis. Regardless, I can at least make conjectures about it.

Personally, my instincts are telling me, provided there truly is a bifurcation node, it would be stable at the peak, which sounds odd. From the mathematical definition, stability indicating that any small perturbations from the bifurcation point will "dampen" out in time, rather than flying off into infinity. In context though, that doesn't sound correct. The reaction has to go one way or another. The peak, representing the transition state, is said to be unstable chemically.

Another issue is with the parameter of time. It has to go forward. In order to analyze it, we would more than likely have to nondimensionalize it.

These are just some of my current thoughts on it. My question is regarding the mathematics of it. I'm just debating whether there is a bifurcation point (which I believe there is), and if so whether it is stable, unstable, or halfstable. Basically, I'm not sure if my reasoning is correct right now. Any help would be appreciated.

Edit: Let me also add that instability does not necessarily mean that a phase point will fly off into infinity. Stability and instability can be be local. In other words, an unstable point can fly into another equilibrium point.

Edit 2:

I'm going to add a lot more detail to this post as I've done some more research and thinking on this topic. First off, my assumption was correct - in fact, transition state theory is, in part, based on potential energy surface concepts. Hence, saddle-points (bifurcations), are incorporated into the theory. Second, time is not necessarily the independent variable. Typically, the graph of potential energy vs. I.V. where the I.V. is usually a coordinate of some sorts - for instance, bond lengths. That said, I believe that modifies my question.

To explain, what I am curious about is the stability of the transient point as a function of time. Right now, my graph does not reflect that, and therefore my conclusions are not necessarily correct. The slope would be, in terms of instantaneous slope, $\frac{dV}{dq}$. But that's not what I want. Rather, I'm looking for $\frac{dV}{dt}$. Without showing the derivation, one can come up with an equivalency: $\frac{dV}{dt} = -(\frac{dV}{dx})^2$. What winds up happening, now, is that the local maxima in the picture corresponds to an unstable fixed point. That makes sense. Any thoughts on this?


texts: According to wikipedia, it was published by Krebs&Johnson to the Enzymologia journal in 1937 [source, "citric acid cycle" section]. However, I'm really struggling to find a digital copy. I thought maybe someone has come across it? It's a pity that there's no copy of a paper that won a Nobel prize.


texts: How to calculate a rough estimate for the volume of a nitric oxide molecule?

texts:
I was wondering what would be the best way to calculate a rough estimate for size of a nitric oxide molecule to use in comparison to a box.

I was thinking volume would be the best method, but this gave me an answer in dm3/mol which I can't use for comparing against the volume of a box.


texts: 'Ab initio' couplings for DNA used in charge transport

texts:
I came across a publication by Senthilkumar et al. [1] in order to compute charge transfer through the DNA. Table 3, for instance, gives the coupling between bases along the leading (or retarded) strand of DNA:

Table 3. Charge-Transfer Integrals, $J$ (in eV), Overlap Matrix Elements, S, and Generalized Charge-Transfer Integrals, $J′$ (in eV), for Nucleobases Stacked at a Distance of 3.38 Å with a Twist Angle of 36°

For concreteness I will talk about only on columns 3 and 6 of the aforementioned table. I have two questions:

For instance, is it 5'-A-C-3' physically different from 5'-C-A-3'? If I 'erase' the direction 5' to 3', then A-C or C-A should be coupled by the same number (for instance, 0.042). However, I think that 5'-A-C-3' is different from 5'-C-A-3', because in the first example, a phosphate is "attached" to A from the left and a sugar is attached to C to the right; in the second case, C is attached to the phosphate to the left and A is attached to the sugar to the right. Is this interpretation correct?

5'-A-C-3' the coupling says it is 0.042, for 5'-C-A-3' it is −0.002. If I regard the previous argument as true, then both DNA systems are different, but not too different since they contain the same basis A and C. Does it make sense that by just changing the position of phosphates and sugars, one is approx. 40 times bigger than the other?

Reference

Senthilkumar, K.; Grozema, F. C.; Guerra, C. F.; Bickelhaupt, F. M.; Lewis, F. D.; Berlin, Y. A.; Ratner, M. A.; Siebbeles, L. D. A. Absolute Rates of Hole Transfer in DNA. J. Am. Chem. Soc. 2005, 127 (42), 14894–14903. DOI: 10.1021/ja054257e.


texts:
My teacher asked me this question a few days ago. "How to define hot and cold?" And I said, "The higher the temperature, the hotter you are. The lower the temperature the colder you are." But my teacher said, "That's not 100 percent correct."

So, how do you really define hot and cold?


texts: Greater ligand stabilization of the lower oxidation state increasing redox potential

texts:
According to Atkins, P.W., De Paula, J. and Keeler, J., 2006, Atkins' Physical Chemistry,

$$
\begin{align}
\ce{[Fe(CN)6]^3- + e- &<=> [Fe(CN)6]^4-} &\quad E^\circ &= \pu{+0.36 V} \label{rxn:1}\tag{R1} \\
\ce{Fe^3+ + e- &<=> Fe^2+} &\quad E^\circ &= \pu{+0.77 V} \label{rxn:2}\tag{R2}
\end{align}
$$

According to my lecture notes, if a ligand stabilizes a lower oxidation state more than the higher oxidation state, the redox potential increases i.e. becomes more positive. This makes sense as stabilizing $\ce{Fe^2+}$ in reaction \eqref{rxn:1} would have the position of equilibrium to the right, increasing electron charge transfer and hence the redox potential, meaning a more positive $E^\circ$ and hence more negative $ΔG$ as

$$ΔG = -nFE^\circ$$

Indeed, $\ce{Fe^2+}$ is more stabilised than $\ce{Fe^3+}$ by $\ce{CN-}$ as $\ce{Fe^2+}$ is a borderline soft/hard acid, $\ce{Fe^3+}$ is a hard acid and $\ce{CN^-}$ is a soft base.

I don't understand why $E^\circ$ becomes more positive going from reaction \eqref{rxn:1} to reaction \eqref{rxn:2}. Please help me to understand why!


texts: Are the molar extinction coefficient and cross-section of an absorption related to the probability of absorption?

texts:
I have struggled to find a formal definition of cross-section of absorption; from what I've gathered, its best defined as 'the intensity of absorption'.

Wikipedia's formal definition of the molar extinction coefficient is 'how strongly a species absorbs EMR at a given wavelength, per molar concentration'.

So how are the molar extinction coefficient and cross-section different? I presume that whilst the molar extinction coefficient remains constant for a given wavelength across all concentrations, the cross-section differs for a given wavelength with changing concentration.

Is either the molar extinction coefficient or cross-section of an absorption equal to the probability that a single species absorbs a photon at any one point in time?


texts: Why don't I get the same value of percentage ionic character of a particular molecule from different equations?

texts:
About the ionic character of a polar covalent compound Pauling gave two equations as

[1-$e^{.25(x_a - x_b)}] $%

[18$(x_a-x_b)^{1.4}$]%

Hanary and Smith gave the equation

[$16(x_a-x_b)+3.5(x_a-x_b)^2$]%

Where $x_a$ and $x_b$ stands for the electronegativity of $a$ and $b$ atom in bond $a-b$.

Now if I put $x_a-x_b = 2,$ The 1st, 2nd & 3rd equations respectively give the value as
     -.648%, 47.5% & 46%. What is the reason behind these  different values of percentage ionic character of the same molecule? At where       am I wrong?


texts: Half cell method of voltage calculation in an electrochemical cell

texts:
A cell consists of a copper electrode $\ce{Cu}$, in contact with $1.800\cdot10^{-2}~\mathrm{M}$ cupric ion and a platinum electrode, $\ce{Pt}$, in contact with $1.400\cdot10^{-1}~\mathrm{M}$ ferrous ion and $3.700\cdot10^{-2}~\mathrm{M}$ ferric ion in $1~\mathrm{M}$ $\ce{HCl}$.
  What is the potential of cell?

I would have an idea of what to do with this question if it had a concentration for copper in the cupric half reaction; I would just use the nernst equation, rearranged to solve for $E$:

$$E = E^\circ - \frac{\mathrm{R}T}{n\mathrm{F}}\log Q$$
Then plug in the concentration values for the cupric half-reaction into $Q$ to get the $E$ value for this half reaction. I'm assuming that the half reaction taking place here is:
\begin{align}
\ce{Cu^{2+} + 2e^- &-> Cu^0} &E^\circ &= +0.337~\mathrm{V}
\end{align}

and the other half reaction taking place would be:
\begin{align}
\ce{Fe^{3+} + e^{-} &-> Fe^{2+}} &E^\circ &= +0.771~\mathrm{V}
\end{align}

Then, I would plug the concentration values, along with their standard potentials, into the rearranged nernst equation to get the $E$ values for each half, then subtract the larger value from the smaller. I already did this, assuming that the concentrations of $\ce{Cu^0}$ and $\ce{Cu^{2+}}$ were the same, giving a logarithm of $0$ and making $E = E^\circ$. The other equation remained the same. I got an answer of $0.399~\mathrm{V}$, which is wrong.

Also, I'm not sure how the concentration for $\ce{HCl}$ factors into this question, because the half reaction for $\ce{Fe}$ doesn't have any hydrogens in it.

Can anyone give me a hand with this one?


texts: Modelling planar molecules and their evolutions

texts:
I am trying to simulate a chain of molecules which are planar.

Can anyone please give me an example of the molecular chain which can stay as planar with it's minimum energy state is planar. A published study on the evolution of the geometry of the molecule will be highly helpful.


texts: A rule of thumb in chemistry is that a reaction doubles in rate for every 10 °C increase in temperature. Considering the impact of a 10 °C increase in global temperature, would the same rule apply to kinetic weather processes – for example, would the average wind speed around the world double?


texts: It seems related to the atomic size but hydrogen has a smaller atomic size than fluorine. Why is fluorine the most electronegative atom?


texts: Why does the C–C bond have extremely weak absorptions?

texts:
My book, Pavia's Introduction to Spectroscopy, tells me this about the infrared spectrum of alkanes:

  $\ce{C-C}$ : Stretch not interpretatively useful; many weak peaks.

This is very interesting. What makes the C–C bond so reluctant to absorb infrared wavelengths?

I have been doing a bit of thinking lately. Bonds absorb infrared radiation that match with the harmonic vibrational frequency of the bond. I believe the extent of absorption is based on the tendency of the bond to get vibrated. For some reason, the $\ce{C-C}$ bond is very reluctant to absorb the radiation, and I believe it's because the bond is too "rigid".

If a bond is too rigid, it must show large change in intermolecular force per change in bond distance. In other words, I believe, the value of

$$\frac{\mathrm dF}{\mathrm dr}$$

is quite high. In such a case, the bond wouldn't have a tendency to compress and expand, since the bond has such a high tendency to oppose such changes. Assuming the bond to act as a spring, I have,

$$F=kr$$

where $k$ is the spring constant of the bond-spring. Differentiating this w.r.t $r$, we get:

$$\frac{\mathrm dF}{\mathrm dr}=k$$

So, this makes me conclude that a higher value of $k$, implies a more rigid bond. I also know that

$$U=\frac{1}{2}kr^2$$

Plugging the values of $U$ ($\pu{=346000J}$) and $r$ ($\pu{=1.54 \times 10^{-10}m}$) for the $\ce{C-C}$ bond, I get,

$$k_{\ce{C-C}}\pu{= 2.92Nm^-1}$$

If I compare this with the value of $k$ for the $\ce{C=O}$ bond (one of the most prominent absorptions), I get,

$$k_{\ce{C=O}}\pu{= 1.11Nm^-1}$$

The $k_{\ce{C=O}}$ is just 3 times smaller than $k_{\ce{C-C}}$, but the existence of $\ce{C-C}$ absorption is rather non-existent.

I can conclude one thing for sure, that all that I have thought before is completely wrong.

So here's my question. Why does the C–C bond absorb extremely weakly? And what's wrong with what I have thought about above?


texts: Does the para position on benzene ring-polymers make the structure stronger?

texts:
Aramid fibers are strong synthetic fibers. Kevlar is called a para-aramid, and it's outstandingly strong. Why does the para-position give Kevlar its strength?

When the Kevlar monomers are in the para-position, will this make the chains closer (shorten the length of the bond), and make strong interactions between the chains?


texts: What's wrong with using tin in medicinal chemistry?

texts:
I just read this In the Pipeline post and I was slightly confused by a statement on the use of tin. Lowe reports on this paper, which describes a synthetic route to spiro heterocycles using tin compounds, and caveats the finding with the comment that

  No one's crazy about using tin, but the transformation is too useful to pass up.

Why is the use of tin undesirable in synthetic chemistry?


texts: What free software exists to view molecule pictures within a file explorer?

texts: I am testing my small api library that generates lots of chemical files such as MOL and SDF. I was wondering if there is a software that can show me the pictures of chemical structures inside each file so that I don't have to open each of these separately. would prefer something free for Windows and Mac.


texts: Is Chromium (VI) fluoride be synthesized properly?

texts:
Chromium (VI) fluoride, also known as chromium hexafluoride is a possible chemical compound with a chromium atom attached to 6 fluorine atoms. It has been unsuccessfully synthesized a number of times by heating up chromium to 400 °C in a fluorine atmosphere at 20 megapascals of pressure and freezing it as it was formed but this was still a failure as this instead produces chromium (V) fluoride or chromium pentafluoride.Is the following possible?
The predicted reaction was:
$$\ce{Cr + 3 F2 -> CrF6}$$
Instead, the following reaction was happening:
$$\ce{2 Cr + 5 F2 -> 2 CrF5}$$


texts: Is there a compound that binds with salt (NaCl) in solution?

texts: Is there a non-toxic compound that binds with $\ce{NaCl}$ in a water medium?


texts: Can Oxybuprocaine hydrochloride react with lidocaine hydrochloride?

texts:
To anaesthetise the mucous membrane 2 separate drugs were given topically:

Oxybuprocaine hydrochloride and Lidocaine hydrochloride. The reason to use both of them seem to be beginning of action and its duration (the former starts faster but shorter, the latter starts later but longer acting).

If instead having them in separate bottles they will be mixed in one, would it cause any interactions between them?

oxybuprocaine:


texts:
Why can we not use zinc for extracting copper from a solution containing $\ce{Cu^2+}$ ions even though it is a better reducing agent than $\ce{Fe}$?
I am studying metallurgy and I cannot understand why zinc cannot be used.


texts: Can I damage a biotinylated antibody in solution by vortexing or mixing too vigorously?

texts:
I am running an immunoassay using biotinylated antibodies and have noticed a decreasing trend from duplicate assay runs (completed within minutes of each other) from the same vial.
In between each run:

I switch to a new low protein binding pipette tip.
I vortex the biotinylated antibody in solution in a low protein binding vial.
Then I prewet the pipette tip and deliver the reagent.

Note that degradation seems unlikely.
Any ideas on what may cause this?
Could it be vortexing or shearing during pipette tip mixing?


texts: Will KOH work in place of NaOH as the electolyte in the electrolysis of water?

texts: I am making a hydrogen and oxygen generator by electrolysis water. I found out that using salt as an electrolyte creates a compound of chlorine and oxygen with my electrodes clouding up the water and using all of the oxygen from the reaction. Bubbles are coming off of only one electrode. In my research I found that sodium hydroxide is a better electrolyte because it doesn't create chlorine gas and shouldn't react with my electrodes. Unfortunately I don't have any, but I am making lye ($\ce{KOH}$) from some hardwood ashes, will this work in place of $\ce{NaOH}$? I'm not sure if the potassium ions will conduct electricity in the same way. Thanks!


texts: Is it correct to say that SOME iodine undergoes sublimation at 1 ATM

texts:
The triple point of Iodine occurs at 0.12 atm and at standard temperature it is a solid on the phase diagram.

I understand that therefore, when heating iodine at 1 atm, it (at least some of it) will pass through the liquid phase, and it is also obvious from observing heated Iodine that it yields liquid when heated gradually. Also, just as liquids can evaporate below the boiling point, I understand that some Iodine can escape from a sample in the vapor form when the vapor pressure is lower than the atmospheric pressure.

My question is 2 part:

1) Is it correct to call the change form solid to gas below equilibrium vapor pressure "sublimation".  In other words, is sublimation equivalent to the term "boiling" or is it equivalent to the term evaporation in the change of phase from liquid to vapor, or both?  (Is there a separate term, even if out of use,  for the solid to vapor transition below equilibrium pressure?)

2) At 1 atm, when Iodine molecules in a solid sample escape into the vapor form, either at standard temperature, or as the sample is heated, do they all briefly pass through the liquid phase first, either at a vapor pressure below 1 atm or as vapor pressure is raised above 1 atm.  .

Iodine's crystal vapor pressure will of course be <0.12 atm below the triple point pressure as can be seen on both graphs.  A converse but equivalent question would be whether vaporous Iodine at 1 atm can crystalize and deposit without liquifying.


texts:
picture above describes two ways of forming epoxides from alkene.
(a) peroxy acid
(b) Br2 and H2O / NaOH
it says R groups stay in the same position.

and I want to ask some about (b).

is it possible R groups that were on the same side before reaction occurs can be opposite side of where the double bond used to be after product is formed?
I've drawn this in the picture below.


texts: Why is the strontium ion smaller than the potassium ion?

texts: The ionic radius of the $\ce{Sr^2+}$ ion is $\mathrm{132\,pm}$, while the ionic radius of the $\ce{K^+}$ ion is $\mathrm{152\,pm}$. Why is this the case? I would have thought that since $\ce{K^+}$ has one less shell of electrons than $\ce{Sr^2+}$, its radius would be significantly smaller.


texts: Why is methyl iodide more dense than ethyl iodide, even though the latter has more carbon atoms?

texts:
It is understood that more carbon atoms present in a hydrocarbon, the greater the density of the hydrocarbon.

But then why does $\mathrm{CH_{3}I}$ have a greater density than $\mathrm{C_{2}H_{5}I}$?


texts: Is the activation barrier of a reaction related to the free energy or heat of formation of its reactants?

texts:
The energy barrier for activation appears in the derivation of a bimolecular reaction through collision or transition state theory, but it seems that from looking at diagram such as this one  it seems like the barrier to activation would be related to the energy required to break bonds?

Thanks in advance.


texts: How to figure out which two solutions will emit largest heat when they are mixed in same volumes?

texts:
How can I figure out which two solutions will emit the largest heat, when they are mixed in same volumes?
Then  let's assume that there are five pairs of solutions given:

\begin{align}
  \ce{2NaOH   + H2SO4   &-> Na2SO4    + 2H2O} \tag1\\
  \ce{Ba(OH)2 + H2SO4   &-> BaSO4     + 2H2O} \tag2\\
  \ce{2NH4OH  + H2SO4   &-> (NH4)2SO4 + 2H2O} \tag3\\
  \ce{NaOH    + H3CCOOH &-> H3CCOONa  + H2O}  \tag4\\
 \ce{2NaOH    + H2C2O4  &-> Na2C2O4   + 2H2O} \tag5
\end{align}

Which one emits the most heat, when we mix same volumes of given pairs?

These are the balanced reaction equation, that occur when the above solutions are mixed. All of these reactions are acid base reactions. And I know when there is an acid base reaction a salt is formed. So how can I proceed with it?


texts: Do metals form covalent bonds besides ionic and cordinate bond?

texts:
My chemistry textbook says that metals form ionic or cordinate bonds whereas non metals form covalent bonds. But in another textbook I read that Lithium, Beryllium, Aluminium, Chromium, Manganese etc, which are metals, form covalent compounds like LiCl, BeH2, AlCl3, H2CrO4, H2MnO4 respectively

Now my question is whether metals form covalent bonds or not? And if yes then how to predict which metallic compound contains ionic and which contains covalent bonds?


texts: Clarification of textbook concepts relating to "perfect", "ideal", and "real" gases

texts:
My textbook, Atkins' Physical Chemistry, 11th edition, by Atkins, de Paula, and Keeler, says the following:

  The resulting expression

  $$pV = nRT \tag{1A.4}$$

  is the perfect gas law (or perfect gas equation of state). It is the approximate equation of state of any gas, and becomes increasingly exact as the pressure of the gas approaches zero. A gas that obeys eqn 1A.4 exactly under all conditions is called a perfect gas (or ideal gas). A real gas, an actual gas, behaves more like a perfect gas the lower the pressure, and is described exactly by eqn 1A.4 in the limit of $p \to 0$. The gas constant $R$ can be determined by evaluating $R = pV/nT$ for a gas in the limit of zero pressure (to guarantee that it is behaving perfectly).

  A note on good practice Despite 'ideal gas' being the more common term, 'perfect gas' is preferable. As explained in Topic 5B, in an 'ideal mixture' of A and B, the AA, BB, and AB interactions are all the same but not necessarily zero. In a perfect gas, not only are the interactions all the same, they are also zero.

My questions here relate to this part:

  A note on good practice Despite 'ideal gas' being the more common term, 'perfect gas' is preferable. As explained in Topic 5B, in an 'ideal mixture' of A and B, the AA, BB, and AB interactions are all the same but not necessarily zero. In a perfect gas, not only are the interactions all the same, they are also zero.

It seems that the authors here are implying that a "perfect gas" and an "ideal gas" are synonymous, but my research indicates that they are actually different concepts. Are these two concepts the same, or are they different? How should one think about (distinguish) these two concepts?
What do the authors mean when they say that "in an 'ideal mixture' of A and B, the AA, BB, and AB interactions are all the same but not necessarily zero"? And what is meant by the interactions being "zero" here?
What do the authors mean when they say that "in a perfect gas, not only are the interactions all the same, they are also zero"? And what is meant by the interactions being "zero" here?

I would greatly appreciate it if people would please take the time to clarify these points.


texts: How can one reclaim isotopic cadmium from a solution of acid, i.e. H2SO4 or HCl etc.?

texts:
I have dissolved isotopic cadmium-114 with $\ce{H2SO4}$ and or $\ce{HCl}$.  Now that I have the cadmium-114 in solution, precipitating out $\ce{CdSO4}$ and or $\ce{CdCl2}$, how can I reduce these simply to leave the pure cadmium metal isotope?  I have dissolved $\ce{^{114}Cd}$ with acid in very complex electronic tubes and I wish to reduce the precipitated compound(s) to pure metal for reuse.

$\ce{^{114}Cd}$ or is running about $ 1,500 per gram.  So extremely useful to reclaim it. Can anyone tell me a simple way to do this?


texts: $\ce{SrSO4}$ is insoluble in water. Will it be more soluble in an acid solution? I know that if the anion is the conjugate base of a weak acid, it'll be more soluble. Does $\ce{SO4^2-}$ count as the conjugate base to $\ce{H2SO4}$ (strong acid) or $\ce{HSO4-}$?


texts: What is the lower bound to the temperature at which a fire can burn?

texts:
To have a fire, you need 1) oxygen, 2) fuel and 3) heat. You can have different fuels that burn at different temperatures, but you always need some amount of heat to have a fire.

If you can use any fuel, what is the lowest temperature at which you can have a fire with an open flame? Is it possible to have a fire that's so cold that you can hold your hand in it without burning yourself?


texts: Reliable automatic addition of hydrogens and charge assignment to small molecules at given pH?

texts:
I have some PDB structures of small molecules with missing hydrogens. Is there a software available that places missing hydrogens and assigns a charge to the molecule that is reliable? I am looking for an automatic tool that returns a PDB with added Hydrogens and the overall charge (I can do some programming if I need to combine output from multiple programs to accomplish this or something.)

It is enough for me if you suggest a couple of FREE tools (I don't have resources to buy a commercial license, but I am academic, in case they offer free academic licenses), with associated papers that evaluate their performance that I can cite. For example, a free tool that calculates pKa values of ionizable groups would solve my problem, if you can also suggest a tool that automatically detects ionizable groups in molecules.

I have used Avogadro to add hydrogens (though I don't know how to compute the charge with it), but I've found that some hydrogens aren't well placed. Is there a better tool available for this task?


texts: Identifying covalent character in ionic compounds when varying multiple ions

texts:
By Fajans' rules, we can easily find out which compound shows covalent character.

Example: Among $\ce{NaCl}$, $\ce{MgCl2}$, $\ce{AlCl3}$ which one is more covalent?

Answer: There is a point in Fajans' rules that the compound which has more charge number that compound will show covalent character. In $\ce{AlCl3}$, Al has the highest oxidation state (+3) so it will show more covalent character than $\ce{NaCl}$ and $\ce{MgCl2}$.

The point is that since all three compounds I have mentioned have chlorine in common, it was easy to catch the solution but if the compounds were given as $\ce{NaF}$ and $\ce{LiCl}$, which one shows more covalent character, and how can we apply Fajans' rules?


texts: redox signaling molecules and electrolysis

texts:
There is a product whose presentation screams of snake oil, allegedly consisting of nothing but electrically treated salt water. The product is claimed to be chock full of "redox signaling molecules" that have lots of health benefits.

I am not a chemist, and I certainly don't want to promote this (un-named) product; I just want a different perspective on it.  My understanding is that electrolysis of salt water produces some mix of $\ce{H_2, O_2, Na, Cl, NaOH}$, and $\ce{NaClO, NaClO_3}$ depending on the configuration of the reactor, with possible inclusion of other substances due to decomposition of the electrodes.

A search on PubMed turned up several papers describing positive effects (in mice) of consuming water containing dissolved $\ce{H_2}$. I haven't found anything indicating that there are health benefits from consuming the other electrolysis products of salt water.

My question is this:  Could any of the other substances produced by electrolysis of $\ce{NaCl}$ in water ($\ce{O2, Na,Cl, NaOH,}$ and $\ce{NaClO, NaClO_3}$) act as "redox signaling molecules" as claimed by the manufacturer?


texts: How can I determine the boiling point of a compound using simple distillation?

texts:
I've graphed a distillation curve (temperature against volume of distillate) from the data obtained from a simple distillation experiment. The substance can be any of methanol, ethanol, 1-propanol or a  1-propanol and water azeotrope).

How can I find the boiling point from this curve to determine the identity of the compound?

I should also mention that there was leftover nonvolatile dye in the round bottom flask.


texts: How is the association/ dissociation constant derived?

texts:
I came across the following formula to find the association of a solute in particular solvent. Suppose the concentration of the solute given in water (or in some other solvent in which it does not associates or dissociates) is $C_1$ and that in some other solvent ( like benzene ) is $C_2$ then the association factor $n$ is determined by $$K=\frac{C_1}{{C_2}^\frac{1}{n}},$$
where $K$ remains constant.

On what concept is this formula based on? Can we derive it? Is it an empirical formula ?


texts:
According to the Brønsted Lowry principle, "base" is a proton acceptor. I've tried to apply this idea to every choice as you can see these red circles in each equation below, but they are all loses protons, aren't they? How could it be a base?

However, if I choose water in a blue circle, I will get the underlined substance as a base for both choice B and C instead. Also, if you have a look at other substances involve in equation B and C, they do support the assumption that they act as acids that involved in donating protons. Hence, both B and C are correct. But the solution said the correct answer is C.


texts: How does a water molecule bond to an anhydrous salt to form a hydrate?

texts: Some sites suggest that water molecules bong to anhydrous salt via a "loose bond". What does that even mean? $\ce{H2O}$ is a polar molecule and salts are made up of ionic bonds. Is it a hydrogen bond between the anions and hydrogen atoms?


texts:
I stumbled upon a question, A mixture of 50 mL of Hydrogen gas and 50mL of Oxygen gas is allowed to effuse through an effusimeter. After some time it is observed that the residual gas occupies 90mL. Find the composition of (1) Effused gas and (2) Residual gas.
Since there was no information given about the pressure, I took it to be constant.
Acccording to the Graham's Law of Diffusion, $\frac {R1}{R2} $ = $\frac{P1}{P2} \sqrt{\frac{M2}{M1}} $ , where M1 and M2 are the molar masses of the gases, P1 and P2 are the partial pressures of the gases and R1 and R2 are the rates of diffusion of the gases.
Now, some of my friends took the ratio of the Partial pressures $ \frac{P1}{P2}$ as a constant and calculated the ratio of rates of diffusion of Hydrogen to Oxygen to be 4 and reached the result composition as: Effused gas- H2=8mL, O2=2mL, Residual gas- H2=42mL, O2=48mL.
I personally think that the ratio of partial pressures will change as the gases effuse out, but I'm not sure how to approach the problem and get the answer with the lowest approximation possible. Please help me out. Is there any way we can solve this problem by not taking the difference in partial pressure as zero?


texts:
Please don't say sodium tetraborate decahydrate since that is not the real composition of borax.

Borax contains tetranuclear coordination complexes $\ce{[B4O5(OH)4]^-^2}$. I'm asking about the name of this complex in borax.


texts: Why do amorphous substances have different values of physical properties in different directions?

texts:
Today my teacher taught about amorphous and crystalline substances. Crystalline substances are said to have different values for physical properties (like speed of light, electrical resistance, etc) in different directions. Crystalline substances are said to have orderly arranged constituents, however this orderly arrangement is not said to be same in different directions. Thus, they are said to show different values for physical properties in different directions.
  Amorphous are said to be isotropic in nature, i.e they have same value for all the physical properties in different directions. I was stuck here, amorphous substances have disordered arrangement of constituents. So, they should strictly have different values in different directions. Is it we speak about average values of physical properties in case of amorphous substances? or is it that, they strictly have same values for the physical properties in all directions?


texts:
$$\ce{CH2=CH-CH=O ->[CH3SH][(1,4 addition)] Product (P_1) ->[(i) NaCN][(ii) NH3\\(iii) H3O+] Q_1}$$
Correct statement regarding $\ce{Q_1}?$

$\ce{Q_1}$ is essential amino acid
$\ce{Q_1}$ is acidic amino acid
$\ce{Q_1}$ is nonessential amino acid
$\ce{Q_1}$ on Lassign test gives prussian blue colour with $\ce{FeSO4}$ and $\ce{FeCl3}$ solution

By 1,4 addition (as mentioned in question) carbon-3 (taking carbon as carbon-1 of aldehyde group) will have $\ce{SCH3}$ added to it and oxygen must have $\ce{H}$ added to it.
After $\text{P}_1$ is formed, it can again tautomerize from an alcohol to an aldehyde.
The $\ce{^-CN}$ can now attack the aldehyde. Looking at the answer we can ay that the product must be an amino acid and so the $\ce{NH3}$ group and $\ce{^-CN}$ must be present on same carbon because then the $\ce{^-CN}$ will hydrolyze to give a $\ce{-COOH}$ group.
But how is $\ce{NH3}$ supposed to attack a carbon having $\ce{^-CN}$ and a hydroxyl group. Can we make the alcohol a leaving group somehow?
Or is the number of carbons in chain 1 less than what it should be? What should be the correct answer and approach for this problem?


texts: without using electronegativity, which one of these molecules is polar?

texts:
If we are given 5 molecules without their electronegativity

BrF5

PBr5

CCl4

XeF2

XeF4

How to determine that one of them is polar or not ?

I know by using the difference in electronegativity we can determine the polarity
But again, electronegativity is not given  ?? /:


texts: "Alkanes must be vaporised before they will burn" - what does this mean?

texts:
What does this sentence mean - I assumed that burning vaporised something? If something is vaporised, isn't that turning it into a gas? How can you burn a gas? This is a sentence in my AS Chemistry book and I am obviously missing something.

"Alkanes must be vaporised before they will burn"


texts:
Can we deduce the actual value of $\mathrm{p}K_\mathrm{a}$ of an indicator if the $\mathrm{pH}$ range has been given?

I know that $\mathrm{pH}$ range is physically the range of values over which an indicator changes its colour from its acid form to its base form, but can we judge the $\mathrm{p}K_\mathrm{a}$ value from the data?

For example: if $\mathrm{pH}$ range of $3.4$ to $4.6$ has been provided, then I know for certain that the $\mathrm{p}K_\mathrm{a}$ value of the indicator lies in between, but can we deduce the actual value?


texts: How to quantify the adsorption affinity of gases?

texts: Is there a term/quantity which shows how 'sticky/adsorptive' a molecule is? I am interested in gas adsorption on steel surfaces in our mass spectrometer and would like to estimate which gases have a higher propensity to adsorb.


texts: Comparing magnesium ion sensitivity in ribosomes to sensitivity in double-stranded DNA

texts:
I was doing some reading on this, and $\ce{Mg^2+}$ has a much greater sensitivity to ribosomes than to dsDNA (double-stranded DNA). It seems the best answer I can think of it that $\ce{Mg^2+}$ provides greater stability and complexation to ribosomes, while it is not as crucial to dsDNA.

Does anyone have a better biochemical explanation why?


texts: What is the net ionic equation for rection of liquid bromide with sodium iodide crystals?

texts:
I have this problem,

Liquid bromine is added to a container of sodium iodide crystals

I interpreted it with this molecular formula $\ce{Br_{2(l)} + 2NaI_{(s)} \rightarrow 2NaBr_{(s)} + I_{2(g)}}$.

From my understanding, since none of the products nor any of the reactants is aqueous, there shouldn't be a net ionic equation. However, my friend has proceeded with the problem as follows:

$\ce{Br_2 + 2Na^+ + 2I^- \rightarrow 2Na^+ + 2Br^- + I_2}$

$\ce{Br_2 + 2I^- \rightarrow 2Br^- + I_2}$.

Could somebody explain which one of us is correct and why?


texts: How to find the moles of carbonic acid I need to add to make a solution of KOH acidic

texts:
I wanted to know if it is possible to add enough carbonic acid to a $\ce{KOH}$ solution to make it an acidic solution.

The $\mathrm{pH}$ of my KOH solution was $13.2$. After adding $\pu{50 g}$ of carbon dioxide (and I do not know how much reacted), the $\mathrm{pH}$ decreased to $10.302$.

Is there a way to know how many moles of carbonic acid more to add to the $\ce{KOH}$ solution to make it acidic?

At first, I thought I could take the change in pH to calculate the additional moles of carbonic acid needed.

So I thought going from a $\mathrm{pH}$ of $10.302$ to $7$, I would calculate the moles of carbonic acid needed for a change in $\mathrm{pH}$ of $3.302$ $\mathrm{pH}$ ($10.302 - 7 = 3.302$). Thus, the calculation would be $10^{-3.302} = \pu{4.989 x 10^{-4} M}$ $\ce{H2CO3}$. There are 2 moles of $\ce{H+}$ in 1 mole of $\ce{H2CO3}$; thus, I need:

$4.989 \times 10^{-4}/2 = 2.49 \times 10^{-4}$ moles of $\ce{H2CO3}$

$\ce{H2CO3}$ is a $1$ to $1$ ratio with $\ce{CO2}$; thus, I need $2.49 \times 10^{-4}$ moles of carbonic acid in solution.

But I do not know if it is right to think it this way?

Can someone tell me if what I am doing is right, and if not, what I can do to theoretically calculate moles of carbonic acid needed to make the $\ce{KOH}$ solution as acidic as I could.


texts: What material should I mix with graphite to make a brick?

texts: I want to make flake graphite into a brick but I don't know what material will work best. Would mixing it with clay work?


texts: What is the electronic configuration of Fe(II) ion?

texts:
The electronic configuration of Fe is $\ce{[Ar] 3d^6 4s^2}$.
So after removing two electrons the configuration becomes:
$\ce{[Ar] 3d^6}$

But why can't the electrons rearrange themselves to give a more stable
$\ce{[Ar] 3d^5 4s^1}$ configuration?


texts: How to calculate S² value of a broken-symmetry wave function?

texts:
$S$ represents spin, signifies the number of unpaired electrons in the system. For example, if the number of unpaired electrons is $1$, then $S=1/2$. $S^2$ is calculated as $S(S+1)$.

From what I have read, the $S^2$ value of a broken-symmetry singlet (contaminated by a triplet) is $1.0$, which is calculated to be the average of the singlet and triplet $S^2$. Similarly, the $S^2$ of broken-symmetry doublet (contaminated by the quartet state) turns out to be $1.75$ (average of a doublet and a quartet). I would like to know how these average values are being calculated. I understand that these are weighted averages (as $1.75 \neq 0.5\cdot(0.75+3.75)$, where $0.75$ and $3.75$ are $S^2$ values of doublet and quartet, respectively), but I don't know how that weighting is being done. I would be grateful if someone could provide a detailed explanation (mathematical derivation)  of this.


texts:
In this answer, I don't understand how this step worked.

Using $\mu_i = \mu^\circ_i + RT\ln \frac{P_i}{\pu{1 bar}}$
\begin{align}
\Delta G &= (c\mu^\circ_\ce{C} + d\mu^\circ_\ce{D} - a\mu^\circ_\ce{A} - b\mu^\circ_\ce{B}) + RT \ln\frac{P_\ce{C}^c P_\ce{D}^d}{P_\ce{A}^a P_\ce{B}^b}\\
\Delta G &= \Delta G^\circ + RT\ln Q
\end{align}

How does $P_i=\dfrac{P_\ce{C}^c P_\ce{D}^d}{P_\ce{A}^a P_\ce{B}^b}$? And how does that equal the quotient $Q$?
If this is wrong, then please provide me the correct way to proceed from there.


texts: Grapefruit juice to extract herbs for tincture

texts:
I tried searching my question on google and did not find anything. I am looking to extract herbs with pure 100% grape juice http://www.lakewoodjuices.com/product_detail/id-32/  ( it is pasteurized ) instead of using the old school method of extracting with a 50% alcohol solution.

My theory as of now would be that it would be more beneficial and it would  ferment or extract the same plus the extra beneficial minerals of the juice. I am wonder what your opinion on this is. Do you think it would extract the same and be just as beneficial as a tincture? Would it be more beneficial? How long should I let it sit for? should I let it sit at room temp or in cooler temp say, $45 ^\circ \mathrm{F}$?


texts:
My task was to do an intramolecular Claisen condensation with this molecule.

I already draw the product to the reaction, but I'm not sure, if I did it right. Could anyone help me out or confirm the solution? There should be only one product since there is symmetry.
Here is the way how I got the product in my question:


texts: Why is benzoic acid a stronger acid than acetic acid?

texts: Why is benzoic acid ($\mathrm{p}K_\mathrm{a} = 4.20$) a stronger acid than acetic acid ($\mathrm{p}K_\mathrm{a} = 4.76$), even though the conjugate base in case of benzoic acid is destabilized due to electron donation through resonance. Whereas there is nothing of that sort operating in acetic acid; only inductive and hyperconjugative electron donation.


texts: What's the convention for the symbols of enthalpies of formation, reaction, etc.?

texts:
I frequently encounter two ways of writing enthalpies of some process, e.g. for the enthalpy of formation:

$\Delta_{r} G$ (or $\Delta_{R} G$)
$\Delta G_{r}$ (or $\Delta G_{R}$)

On the IUPAC Gold Book webpage they used the first notation (although the use of upper- and lower-case descriptors varies, see here and here). Is this the accepted way of doing it (and the other one is simply a relic) or might this be a matter of preference. And how about the upper- or lower-case descriptor: Is there any convention for that?


texts: Does oxygenating tap water remove the tap water flavor?

texts:
I know flavor is subjective and not exactly quantifiable, but I think there's merit to this question.

We've all experienced that tap water often tastes a lot worse than bottled water or filtered water. I've always felt, however, that cold water actually tastes much purer than warmer water.

For instance, I was recently in a house where I knew the water was so called "hard water" and I could taste that it had the typical mineral flavor straight from the tap.

So, I took a glass of this tap water and refrigerated it for about a half hour and then drank it and I couldn't taste the typical tap water flavor at all.

I'd encourage people to try this just to make sure I'm not crazy.

Additionally, I have family that lives in Ohio and if anyone has ever tasted Ohio's tap water after living in a place like Washington (where I live) which has extremely fresh water, you know that Ohio's water is disgusting. I have found, however, that it tastes much better after being refrigerated for a while.

So, there are a couple of questions here.

Is it even true that refrigerating water (and thus cooling it) would cause a significant amount of oxygen to be dissolved in the water?

If so, would the amount of time the water is being refrigerated (even at a constant temperature) continue to dissolve more oxygen into the water? In other words, how long might it take for oxygen to reach it's equilibrium level of dissolution?

Those last two are definitely answerable chemistry questions. This next one is a little hairier.

Is there any reason, related to chemistry, that oxygen rich water would taste better than water not saturated with oxygen? Meaning, does the oxygen actually have a well-defined effect on the flavor of water, or is this simply answered by the fact that most people like the feeling of cold water more than luke-warm water and hence I identify cold water as "tasting better"?


texts: Why is the dihedral angle of solid hydrogen peroxide less than that of gaseous?

texts:
Hydrogen peroxide has an "open book" structure:

The dihedral angle in gaseous H$_2$O$_2$ is close to what we might expect in a tetrahedral arrangement. However, in solid H$_2$O$_2$ it's almost a right angle. My book says that this is due to "hydrogen bonding" but doesn't go into further detail.
Note that this question isn't a duplicate of Dihedral angle of gaseous and crystalline HOOH as the accepted answer is clearly incomplete, and the other answer uses a computer simulation that falls short of an intuitive explanation.


texts: homogeneous mixture - Are they truly uniform in composition and proportion?

texts:
If 5ml alcohol is dissolved in 1 L of water ( the purpose is to highlight the low quantity of one of the liquids) , how is it possible for 5 ml to evenly dissolve in 1 L of water ? There is not enough of alcohol to sit between water molecules , isn't it ? So how is the mixture's proportion/composition is uniform ?

Or is there anything that I miss to understand in the term - composition?


texts: What is the relation between molarity and molality?

texts:
Is the following equation correct:

$$m = \frac{1000 \times M}{M \times M_b - 1000 \times d},$$

where $M$ - molarity, $m$ - molality, $d$ -density of solution, $M_b$ - molar mass of solute?


texts:
Sodium hypochlorite is used in bleach, calcium hypochlorite is used in public swimming pools, ammonium perchlorate is used in solid rocket fuel.

Sodium periodate is used in the cleaving of syn-vicinal diols, and is generally useful as an oxidizing agent.

Bromates are water contaminants, and perbromates weren't even successfully synthesized until 1968, but only through radioactive decay. Though alternate methods for their production exist today, what makes bromine oxyanions so unstable when chlorine and iodine oxyanions are widely used in chemistry?


texts:
I know that Lewis' concept of acid base deals in terms of electrons and Brønsted in terms of $\ce{H+}$ and base which can provide electrons or $\ce{OH-}$. If I am wrong (partially or fully) please explain Lewis and Brønsted-Lowry concept along.

According to me it is a Lewis base because of the lone pair on oxygen of the alcohol and a Brønsted acid.


texts:
I wear corrective eyeglasses, and because of this, I frequently experience problems with fogging when I wear safety goggles. How can I prevent or reduce fogging?

The safety goggles I use are the standard-issue goggles supplied by the campus store, but I can use other goggles rated at least Z87+D3 ("+"=impact, "D3"=splash) if I want.

One method of reducing the fogging I have tried is wedging a folded paper towel under the top edge of the goggles. It works, but I don't feel comfortable with it because it compromises the splash protection of the goggles.

I have also tried placing desiccant packets (of the sort found in various packaging) in the goggles. This has helped somewhat but doesn't solve the problem completely.

One possible solution would be to get safety goggle with prescription corrective lenses built-in (making them Z87-2D3 instead of Z87D3), but I have not been able to find a supplier online for such eyewear.

What can I do to reduce or eliminate fogging?


texts:
My textbook states "A system is in thermodynamic equilibrium if it is in Thermal, Mechanical, and chemical equilibrium simultaneously".
The Wikipedia article on "reversible processes" states that the system is thermodynamic equilibrium with the surroundings throughout the process. This means, as per my initial statement, $\ce{Tsys=Tsurr}$ at every instant of the process.
Atkins-Physical Chemistry, page 77 states, while explaining the entropy change of the surroundings: "furthermore, because the temperature of the surroundings is constant whatever the change, for a measurable change,$\ce{\Delta}Ssurr=\dfrac{q_{surr}}{T_{surr}}$".
But then this treatment seems to contradict the fact that the system and surrounding are in thermal equilibrium! Since $\ce{Tsys=Tsurr}$ implies that $\ce{Tsurr}$ is not constant as long as the process isn't isothermal.
I therefore believe that my first statement is incorrect.If it isn't incorrect,then what am I misinterpreting?


texts: Is there any proof of law of mass action?

texts: I was studying chemical equilibrium and my teacher taught me the law of mass action given by Guldberg and Waage. But is there any proof of this law? I did not find the proof anywhere. I searched all over the internet. The proof is not in my textbooks, not did my teacher tell me anything about the proof. It would be of great help if someone could provide the proof. I just want to know from where the law came as I do not feel satisfied just rote learning a formula and not knowing from where it came.


texts: Is it possible to have a dispersion interaction with no inductive interactions?

texts:
In symmetry-adapted perturbation theory, the interaction energy of a non-covalently bound pair of molecules (it could be done to arbitrary order but is usually just pairs) is built up from a perturbative expansion of the interaction potential between two monomers.

The first-order perturbation drops out a term which we call induction. This has components associated with the induction on monomer B by monomer A and vice versa. The second-order perturbation drops out a term which we call dispersion (this is what people usually refer to when they say van der Waal's force (although that's not technically correct...)).

My question is, can that second-order perturbation term--dispersion-- have a non-zero contribution to the total energy while the first-order induction terms do not contribute?

When I imagine this situation physically, it doesn't make much sense because it means that the presence of monomer A near monomer B does not perturb the eigenstates of monomer B (beyond electrostatics, exchange, etc.) and vice versa, but somehow there is a mutual dispersion effect.

So basically what I'm asking is if it is mathematically possible to have a non-zero dispersion term while simultaneously having zero contributions from the first-order induction terms in the interaction potential expansion?

Also, if it is not possible, it seems as if we ought to be able to write the dispersion energy in terms of the induction energies, but clearly we can't because dispersion is a second-order perturbation. If the effects are related, however, can we approximate dispersion using induction? I imagine this to be similar to how in Moller-Plesset perturbation theory you can approximate the fourth-order perturbation using the second-order perturbation.

I don't know too much about the details of what I'm asking about, so if I've said something quite stupid please let me know.


texts: Is vapour pressure of a liquid solution constant at a given temperature, no matter the size of closed container and amount of liquid taken?

texts: Does vapour pressure of a liquid solution depend on the size of closed container, amount of solution taken, given that, temperature is kept constant? Or will it change, if some extra gas is added to the container at constant temperature?


texts: Are all hydrolysis reactions non-redox reactions?

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Are all hydrolysis reactions always non redox reactions? For example:
$$\ce{N2O3 + 2H2O -> 2HNO2}$$
The main reason I say that this statement is correct is because oxygen and hydrogen generally show oxidation states of −2 and +1 respectively when bonded to other atoms.
This means that any change in oxidation state needs to take place between the nitrogen atoms involved in the molecular structure and this is very rarely seen.
Hence most (if not all) hydrolysis reactions are non-redox in nature. Is there a mistake in my understanding?


texts: Would it be correct to say that ozone is an element?

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My level of chemistry knowledge is restricted to that which is given at high school level.

I was tought that an element is a substance that consists of only one type of atoms, meaning the number of protons is the same for every atom. Is this definition sound?

In case it is sound:

Since ozone gas only consists of oxygen atoms, would it be correct to say that ozone gas, as an entity, is an element?

Would it be more correct to say that ozone is an allotrope of the element oxygen?

Why is it called the table of elements, when it seems that we are actually listing the atoms and not the elements themselves?


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Theoretically, if you could could have a positively charged gas say O$^+$ enclosed (by a sufficiently inert material) around a conductor which is grounded, what would the reaction be at the conductor if the conductor was made of;

1) Tungsten, 2) Stainless Steel,  3) Copper.

Would the gas gain electrons from the conductor and form O$_2$, react with the conductor to form a coating, react with each other, react with the container or something else?


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I know that chloroform can be used to make people unconscious, but would that also work with deuterated chloroform, $\ce{CDCl3}$?

My instinct is "yes", but I'm not sure I'm willing to try this experiment on anyone.


texts: Size of target substance in IR and Raman Spectroscopy

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Usually what is the size (in nanometer) of the sample or target substance in IR and Raman Spectroscopy?

Which one has largest size of sample it can scan, how many molecules or atoms are involved? If you can make the size bigger or scan coverage bigger, then the more intense would be the IR or Raman stroke signal? Or no difference in intensity in the case of Raman even if sample size is increased? Please answer separately for IR and Raman since they are different. One uses IR light, the other laser. I guess IR light needs to be focus at a spot just like a laser too.


texts: Convert Concentration (particles/ml) to (mg/ml)

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I am struggling with converting concentration from (particles/ml) to (mg/ml). I have the concentration for latex particle (particles/ml) and I want to convert it to (mg/ml).

I worked  out the number of moles since I know the the pressure and volume. But I am not sure what to do after that.


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If we try to calculate the oxidation state of nitrogen in $\ce{N2O}$ using the familiar algebraic method, we get oxidation state $+1$ for both nitrogen atoms and that's what I found when I looked it up on the internet.
I tried to do it with the structure and that's where I got confused:
$$\ce{\overset{-}{N}=\overset{+}{N}=O}$$
The $\ce{N=N}$ bond is a coordinate bond, so that should give a $-1$ oxidation state for the left $\ce{N}$ and $+1$ for the middle one. Since the middle one has a double bond with oxygen, it gets additional $+2$ for a total of $+3.$
But if I consider this resonance structure:
$$\ce{N#\overset{+}{N}-\overset{-}{O}}$$
The left $\ce{N}$ is getting an oxidation state of $0$ and the middle one gets $+2.$ So I am confused as to what is actually correct.
Is it possible for atoms to exist in superpositions of oxidation states? Or maybe I am overlooking some basic concept?


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I read it from a book but don't know the reason. Please explain...

Boiling point orders are -

Ethanamide > Ethanoic Anhydride > Ethanoic Acid


texts: Synthesis of Benzaldehyde and Aniline Schiff Bases

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I have a problem while synthesize the schiff base. I synthesized using absolute ethanol as solvent and use reflux method for 4 hours generally. The problem occur on TLC where there is still two spot on the product which one of them are very clear (top one) (which I guess the ligand formed) and another one were very light, while on NMR spectra, whereby there is a singlet peak at approximately 10.0 ppm which I assumed that it is from the aldehyde itself which probably not completely reacted. I also tried several derivatives based on benzaldehyde and aniline but some of them have to be recrystallize which I havent found the suitable solvent system yet.

So with all due respect, I really need help especially those who have an experience on synthesizing schiff base and also share to me some ideas to recrystallize my ligands.


texts: Is it possible to have negative bond orders?

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In the MO theory, is it possible to have a molecule with bond order less than 0? The least bond order I have come across as of now is 0 (for di-atomic noble gases), indicating that the molecule cannot exist and the atoms get pulled apart.

Is it possible to create a scenario (at least theoretically) where we deal with a negative bond order by manipulating the system's conditions or any of that sort?


texts: Am I using these spectra to identify the compound correctly?

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What is the structure of the molecule whose data is shown below? Explain your answer [...] EI mass spectrum: The highest peak observed is $m/z$ 210 and its abundance is low. The only other significant peak is observed at 167 Th (base peak). [...]

Full question text: https://imgur.com/a/awLve4z

Based on the IR value, I reasoned that it is a ketone. Nothing else in the IR spectrum really stood out to me, so I stuck to the idea that it must be a ketone. I assumed the mass of the compound is 210 g/mol so I subtracted the mass of oxygen and used the rule of 13:

Oxygen's mass = 16 g/mol

(210-16)/13 = 14 + 12/13

So the molecular formula is $\ce{C14H_{(14+12)}O = C14H26O}$

I noted that there were 7 signals recorded in the carbon NMR spectrum. I assumed that meant there were equivalent carbons in the molecule. The molecule I ended up drawing to match this is 7-tetradecanone.

Do you think this is the correct molecule?


texts: Why does increase in pressure favor formation of water in water-ice equilibrium (at 273K)?

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The question:

Ice and water are placed in a closed container at a pressure of 1 atm and a temperature of 273 K. If the pressure of the system is increased to 2 atm while keeping temperature constant, why does the system's volume decrease?