texts:
I suppose that my problem is not one of great profundity, but it is an annoying one. The problem is related to the measurement units involved in rate equations of different order. Not being a chemist myself, I have in my work encountered equations of the type: $$\frac{-\mathrm{d}[A]}{\mathrm{d}t} = k [B]^b [A]^a$$ representing the decay of some species $A$. The brackets denote concentration and $k$ is the rate constant. $B$ is some other chemical species (cooking chemical) and then there are the exponents $a$, $b$. For a first order reaction with $b = 0$ and $a = 1$ everything is still under some kind of control; if time is measured in minutes the unit of the rate constant is $\mathrm{min^{-1}}$.

However, if we have a pseudo first order reaction where the species $B$ is present albeit constant during an experimental run, problems arise. In my line of work the species $B$ is typically hydroxide ions and their concentration is traditionally given in molar, $\mathrm{mol/L}$. Even if the concentration of $B$ does not change, the initial concentration plays a role, hence the power of $[B]$ usually appears as a separate factor in the rate equation. Unfortunately, this complicates the unit balance in the equation as frequently the exponent $b$ is a non-integer number. One workaround would be to rescale the concentration to a dimensionless number, but the choice of scaling parameter would be rather arbitrary. Another, perhaps more elegant solution would be to work with molar fractions, but this would be discordant with most of the literature in the field, where the question of unit consistency mostly is disregarded.

A second order rate equation ($b = 0$, $a = 2$, or $b = 1$, $a = 1$) leads to the unit $\mathrm{L\,mol^{-1}\,min^{-1}}$ for the rate constant. I suppose this is still somehow acceptable, even if I would prefer to work with scaled concentrations (divided by the initial concentrations) with unit $\mathrm{min^{-1}}$ for the rate constant, but for fractional order rate equations there is the same problem as in the earlier described pseudo first order case.

Is there any prescribed remedy to this dilemma?


texts: What are the products formed when nitrogen dioxide reacts with water?

texts:
I've seen two different equations for the reaction of nitrogen dioxide with water:

$$\ce{2NO2 + H2O -> H+ + NO3- + HNO2}$$

and

$$\ce{3NO2 + H2O -> 2H+ + 2NO3- + NO}$$

Are both of these correct to some degree, and is one more prominent over the other?


texts: Calculating time needed to coat an object using the process of electrolysis

texts:
Suppose we have an object with a surface area of $S=\pu{1.5 dm2}$, and we need to coat it with hard chrome. The thickness of the coat should be $d=\pu{80 \mu m}$. The mixture used for coating is of the following mixture: $\ce{CrO3}$  $\pu{290 g/L}$, $\ce{H2SO4}$ $\pu{2.5 g/L}$. The current density is $J = \pu{50 A dm-2}$. The current utilization factor is $\mu = 15\%$. Using Faraday's law of electrolysis:
$$\frac{m}{M}=\frac{q}{F}$$
and the fact that
$$J_{\mathrm{actual}}=0.15\cdot\frac{q}{S\Delta t}$$ where $S$ represents the surface through which the constant current passes through, I got $\Delta t = \pu{1425 s}$, however the answer is $\Delta t = \pu{2 h 22 min}$.


texts: How does absence of nd orbital in Oxygen affect its valency?

texts:
The original question was 'Oxygen exhibits Oxidation state -2 to +2 but other elements of grp 16 exhibit only +2,+4,+6. Explain Why'. In the solution given i can't understand meaning of this line 'It doesn't have nd-orbitals due to which its valency doesn't increase'. Please explain how?
PS:I am a chemistry noob. So please provide as much details as possible :)


texts: Why do Gas Laws only use Kelvin Temperature?

texts: I didn't see this in any other question, although it seems to be a fundamental question of the gas laws. I understand that Charles' Law practically has to use Kelvin temperature, because you would end up with a negative number in some cases, but can someone explain clearly what Charles did with the three gases and why the volume can only be proportional to the Kelvin temp and not the Celsius temp? thanks.


texts: Peculiar behaviour of tea boiling as milk+Water

texts:
While making tea last night I forgot all about it and left the kitchen. When I did remember about it, I ran back and I was surprised to see that it was still in the vessel (though it formed a peculiar foam-like mass on the top).

This pushed me to do the same with water and milk (as these were constituents this tea).
I was not so lucky in case of milk, When I boiled the milk it rose too much and overflowed.

Boiling water alone didn't help either. The level of water in the vessel rose a little but it was far from overflowing (I provided the highest temperature as I could provide to vessel).

So I observed three different phenomena for three different liquids:

Tea (having water and milk in proportion of 3 and 1) rose till the height of container.

Milk overflows.

Water doesn't even remotely show anything that would indicate it was responsible for this peculiar behaviour of tea.

I can't seem to figure out why this happens. Would anyone know why?Thanks for any help
EDIT
After listning to people saying that they need more experimental data I decided to go further.
I boiled the milk along with water in a proportion of 1 by 1 (without tea leaves and sugar to it) and did the same with different proportions of milk and water.
After doing so I got that As I increased the amount of water (in combo of milk and water) the level of solution started decreasing and ultimately at the ratio of 1 and 5 (for milk and water) the solution didn't overflow.
The results were as expected but I thought these can be helpful for you guys in answering the question.


texts: I have heard that Avogadro's number, $N_\mathrm A=6.022 \times 10^{23}$, is the number of atoms contained in $12$ grams of $\ce{^{12}C}$. I think it should be an integer, but I couldn't find the exact number. Is it an integer?


texts: Applying Huckel's rule to non-planar compounds

texts:
Which of the following compounds is aromatic?

From the 4n+2 rule, it must be either option 2 or 4. The answer given in my book is option 4. Why? I think It might be due to one being planar and the other not, but to me both seem to be planar. Is there a way to check if one is planar or not?


texts: How does intramolecular hydrogen bonding cause the molecules to be separated from each other?

texts:
I learnt about intramolecular hydrogen bonding today, which occurs between molecules such as ortho-nitrophenol. What I was told is that in case of intramolecular bonding, the molecules separate from each other, opposite of what happens during intermolecular hydrogen bonding.

I don't understand why is this. Why would attraction within a molecule cause separation of the molecules? There is obviously some intermolecular hydrogen bonding present in this case, but I understand that this might be negligible. Still, why should the molecules spread away from each other?


texts: Why is the tetraamminecopper(II) ion square planar?

texts:
The tetraamminecopper(II) ion is square planar in shape. But why? How can I rationalise this?

Can I rationalise this without the concept of hybridization? And even if I take hybridization into account, which hybridization takes place here and why?


texts: Why is the melting point of propane lower than that of both methane and ethane?

texts: I've seen their properties in my textbook and multiple online sources, but I can't seem to find a straight answer as to why. Excluding propane, the trend is increased melting point as the molecule gets bigger, but propane is the weird exception here.


texts: How do I calculate the pH of this buffered solution?

texts:
Calculate the $\mathrm{pH}$ of a buffered solution containing $\pu{0.5 M}$ ammonia and $\pu{0.5 M}$ ammonium chloride when $\pu{0.15 M}$ $\ce{HCl}$ is added into it. The $\mathrm{p}K_\mathrm{b}$ of ammonia is $4.75$.

This is what I think shoud be going on in the buffer solution:

\begin{align}
\ce{NH3(aq) +H2O(l) &<=> NH4+(aq) +OH-(aq)} \\
\ce{NH4Cl(aq) &-> NH4+(aq) +Cl-(aq)}
\end{align}

This is where I get stuck thinking that the question told me that I have a buffered solution containing $\pu{0.5 M}$ $\ce{NH3}$ and $\pu{0.5 M}$ $\ce{NH4Cl}$ solution, but is that even possible? How can you make a $\pu{0.5 M}$ ammonia solution? Would not that ammonia exist as ammonium $\ce{NH4+}$ and whether the equations I wrote are correct. I am just so confused!

Sorry for the delay but I'm having exams. Okay, I'll try to do this now by not using the Henderson equation.

Firstly, ammonia will refer to ammonium hydroxide, i.e. $\ce{NH3 -> NH4OH}$:

\begin{array}{cccc}
&\ce{&NH4OH &<=> &NH4+ &+ &OH-} \\
&\mathrm{I}: &\pu{0.5 M} & &\pu{0 M} & & \pu{0 M} \\
&\mathrm{E}: &(0.5 - x)\,\pu{M} & &x\,\pu{M} & &x\,\pu{M}
\end{array}

Now for the salt:

\begin{array}{cccc}
&\ce{&NH4Cl &<=> &NH4+ &+ &Cl-} \\
&\mathrm{I}: &\pu{0.5 M} & &x\,\pu{M} & &\pu{0 M} \\
&\mathrm{E}: &\pu{0 M} & &(0.5 + x)\,\pu{M} & &\pu{0.5 M}
\end{array}

$$K_\mathrm{b} = \frac{[\ce{NH4+}][\ce{OH-}]}{[\ce{NH4OH}]} = \frac{(x + 0.5)x}{(0.5 - x)}$$

and since $K_\mathrm{b} = 1.778 \times 10^{-5}$, I can find the value of $x$ to be $1.7778 \times 10^{-5}$.

$$[\ce{H+}][\ce{OH-}] = 10^{-14} \to [\ce{H+}] = \frac{10^{-14}}{[\ce{OH-}]}$$
and $x = [\ce{OH-}]$. So

$$[\ce{H+}] = 5.624 \times 10^{-10}$$

Now I add the $\ce{HCl}$:

\begin{array}{cccc}
&\ce{&HCl &<=> &H+ &+ &Cl-} \\
&\mathrm{E}: &\pu{0 M} & &\pu{0.15 M} & &\pu{0.15 M}
\end{array}

I will ignore any common ion effect since it will be negligible (I think).
The pH will be the total $\ce{H+}$ concentration, so $[\ce{H+}] = 5.624 \times 10^{-10} + 0.15$. This is a pH of about 0.823 which is totally wrong. What am I doing wrong? Also, the volumes of the buffer solution or of the acid solution have not been given.

Okay, so I now know what I was doing wrong (thanks to someone pointing it out). I was adding in $\ce{HCl}$ without thinking that it would actually react with the ammonia in equilibrium in solution (which is just me being either dumb or ignorant).

So I have the situation that:

\begin{array}{cccc}
&\ce{&NH4OH &<=> &NH4+ &+ &OH-} \\
&\mathrm{E_\text{(no HCl)}}: &(0.5 - 1.778 \times 10^{-5})\,\pu{M} & &(1.778 \times 10^{-5})\,\pu{M} & &(1.778 \times 10^{-5})\,\pu{M} \\
&\mathrm{E_\text{(HCl)}}: &()\,\pu{M} & &()\,\pu{M} & &()\,\pu{M}
\end{array}


texts: Why does it not matter what mass of NaOH is used to solve for q?

texts:
So we recently did a lab in Chem to prove Hess's law. The reactions we performed were

$$\begin{align}
\ce{NaOH + HCl &-> NaCl + H2O}\tag1\\
\ce{NaOH(s) + HCl &-> NaCl + H2O}\tag2\\
\ce{NaOH(s) &-> Na+ + OH- }\tag3
\end{align}$$

One of our post lab questions asks us to describe what would happen to the $q$ and $\Delta H$ of reaction $\text{(3)}$ if twice the mass of $\ce{NaOH(s)}$ were used.

For the third reaction, 4.1 degrees was the temperature change, 2 grams of $\ce{NaOH(s)}$ were used, and $50\ \mathrm{mL}$ of water were used. This gave me

$$q = (52~\mathrm g \times 4.18 \times 4.1) = -891.176 ~\mathrm J$$

and

$$\Delta H = (-891.176~\mathrm J/0.05~\mathrm{mol}) = -17824 ~\mathrm{J/mol}$$

When I used twice the mass of $\ce{NaOH(s)}$ like the problem asked, my results were

$$q = (54~\mathrm g \times 4.18 \times 4.1) = -925.452 ~\mathrm J$$

and

$$\Delta H = (-925.452/0.1~\mathrm{mol}) = -9225.908 ~\mathrm{J/mol}$$

Considering my results, why does the very next problem say that in reaction $\text{(3)}$, it doesn't really matter what mass of $\ce{NaOH}$ is used? Why would it not matter? My $\Delta H$ and $q$ values were different. I'm convinced that I made an error in my calculations, so I'd greatly appreciate some clarification here.

Also, it asks why is it important that $2\ \mathrm g$ of $\ce{NaOH}$ be used in reaction $\text{(2)}$? Is it because it's reacting with $\ce{HCl}$ instead of water like in reaction $\text{(3)}$?


texts:
I am currently trying to make a magic potion with chemistry.

I want to turn black liquid clear to reveal a hidden message.

I am currently using water, blue and red food colour and bleach. This works but I want something more dramatic and safe for kids.

Any Ideas :)?

regards Daniel


texts: Simple and cheap anti-graffiti layer based non-paint solvent

texts:
I have this issue with a group of people intentionally damaging a bench. So far, they would paint curses over the bench with permanent marker. However after I removed the curses with ethanol, they damaged the bench physically and threw the trash all around (we used to have a trash can there, with sign "Please do not throw trash around" - they threw this trash can away too).

I would like to keep this question non-personal though, so my question is:

How can I protect a nitro-based paint layer from other paints?

The professional solutions are way too expensive, while the thing I want to do is simple: I'm looking for non-nitro based material and solvent that will form transparent layer over the original paint. In case of damage by nitro-based paints, I could wash the layer under them and then apply it again.

The theory is following: you apply the protective layer over your paint. When somebody applies any paint over it, you've got 3 layers.

It does not matter what the top layer is, as long as it does not dissolve our protection. After this, we apply solvent for the protective layer. Assuming there are microscopic holes in the top paint, the protective layer will dissolve and the top layer will go off with it.

The layer must not be obvious.

I was considering these:

Ethanol-based transparent paint (too expensive, suprisingly)
Wax (parafin) based layer (I don't know how to dissolve wax, it's crystalic so not transparent)


texts: Validity of Maxwell-Boltzmann distribution for solids

texts:
Suppose there is a solid made of avogadro number of, say, aluminium atoms. This solid is kept at 273 K. According to Maxwell-Boltzmann distribution, all the particles or atoms will not have the same thermal energy. Some atoms are cooler than 273 K, some are much warmer than that etc. But is this true?

I mean, according to thermodynamics, heat must flow from warmer to cooler places (or particles) and must arrive at thermal equilibrium so that both places or particles will have same thermal energy or temperature.

So, atleast after some time, all the particles or atoms in a solid as I mentioned above must exchange energy with each other and must arrive at thermal equilibrium so that all the particles will have the same temperature (in the case I mentioned, 273 K), isn't it? But according to Maxwell-Boltzmann distribution, this will not happen.

-Why is this so?

-Or is Maxwell-Boltzmann distribution not valid for solids, so that the atoms will infact have same thermal energy or temperature atleast after some time?

-If it is valid for solids, why don't the atoms all arrive at a state where all of them have same temperature (which should happen from the point of view of thermodynamics)?

Edits:

I could clarify most of my questions from the link of another similar question provided. But, I couldn't find an answer to my last question:

-What might be the approximate value of the thermal energy or the temperature of the particle having maximum energy in the solid I mentioned as predicted by Maxwell-Boltzmann distribution?


texts: when is a system of mass-action reactions guaranteed to satisfy detailed balance?

texts:
when does a system of mass-action reactions satisfy detailed balance for any non-zero choice of the rate constants?
consider a trivial example:
$X + Y \ce{<-->[k1][k2]} XY$
satisfies detailed balance for any $k_1, k_2 > 0$. Here is a less trivial example:
$A + X \ce{<-->[k1][k2]} AX$
$B + X \ce{<-->[k3][k4]} BX$
we can ask if this system satisfies detailed balance, ie whether for any cycle the product of the rates going clockwise must equal the product of the rates going counter-clockwise (Wegscheider condition)?
It appears that any positive non-zero values of $k_1,k_2,k_3,k_4$ this system satisfies Wegscheider. Is that right and if so is there a simple property of the structure of such reactions that we can check to tell if it will satisfy Wegscheider?


texts:
I am having difficulties to count the number of free rotating bonds for the Lipinski and Veber rules. What are the rules in doing so?

In Vemurafenib (shown above), which bonds are considered rotatable? Do the sulfonamide N-S bond, or the single bond linking two aryl groups, rotate?

Many thanks


texts:
Why is sulthiam base even hough sulfur can accept the electron by resonance from nitrogen
like carbonyl group do?


texts: Wilkinson's catalyst: why this structure?

texts:
I wonder how the structure of Wilkinson's catalyst contributes to its catalytic properties. For example, what role do the phosphine ligands play? What properties make Rh the best TM centre?

Thank you!


texts: How to obtain hydrophobic Doxorubicin from its hydrochloride salt?

texts:
I have read literatures on dissolving Dox hydrochloride in DMSO and adding Triethylamine to the resulting solution. The purification is done using dialysis (incase of polymers). But I cannot do dialysis.
Another method I tried was neutralizing the salt solution of Doxorubicin with PBS (pH 8.04), and centrifugation of the resulting mixture. But centrifugation yielded no pellet.


texts: What is the grey film/black sludge from mercury? How to remove it?

texts:
How to remove it? Any other simple method apart from distillation.

I have a small container of mercury that I’ve collected over the past decade. I opened the container after a few years now and I noticed that there is a grey coating on the surface of mercury. Also there is a black powdery deposit at the bottom. It sticks to the bottom and sides of the plastic container.


texts: How does the surface to volume ratio of ions and their distribution in solution compare to that of suspended nanoparticles in nanofluids?

texts:
I am interested in understanding the heat transfer capabilities of fluids.
Nano-fluids are suspensions of nanoparticles (1-100nm sized particles) in a base fluid, often water, oil or glycol. These provide anomalously enhanced heat transfer capabilities on account of the surface area to volume ratio of the particles. The percentage of atoms present on the surface of nanoparticles far exceeds that of the percentage of atoms in bulk materials.
Smaller particle sizes (with larger surface areas) have been shown to correlate with higher specific heat capacities (see Ref. 1).
What I would like to understand is how ions are distributed in a solution, and its impact on heat transfer. Are ions in solution smaller than nano-particles? What is the surface area of an ion in solution, and what volume does it occupy?
If I were to dissolve silver nitrate in water, I would get $\ce{Ag+}$ and $\ce{NO3-}$ ions distributed in the solution. Will they be distributed as aggregates of positively charged silver and negatively charged nitrate ions or as uniformly distributed individual ions?
If the latter, would not these ions have very large surface area to volume ratios, more so than that of nanoparticles? I do not know. Intuitively it seems so. If so, specific heat capacities of solutions should reflect this.
However, this does not appear to be the case. Experimental data and theoretical calculations and models for calculating heat capacities for solutions reflect bulk properties. A common and simple method of estimating specific heat capacity of solutions was proposed by Dimoplon as the sum of the component fractions of individual specific heat capacities:
$$           C_p(\textrm{soln}) = w_\textrm{solid} C_p(\textrm{solid}) + w_\textrm{water} C_p(\textrm{water})   $$
where
$C_p(\textrm{soln})$= Heat capacity of the solution,
$C_p(\textrm{solid})$= Heat capacity of the dissolved solid,
$C_p(\textrm{water})$ = Heat capacity of water,
$w_\textrm{solid}$ = Weight percent of dissolved solid,
$w_\textrm{water}$ = Weight percent of water.
This calculation (which agrees closely enough with experimental data) makes use of specific heat capacities of bulk material, so obviously it appears that the surface area to volume ratio of ions is not very high with respect to nanoparticles.
How then are ions distributed in solution?
I would appreciate if anyone could explain the theory/mechanism behind this or point me to a place where I can obtain a better understanding.
References

Madan Singh, Sekhants o'Lara, Spirit Tlali. Effects of size and shape on the specific heat, melting entropy and enthalpy of nanomaterials. Journal of Taibah University for Science. Volume 11, Issue 6, November 2017, Pages 922-929. https://doi.org/10.1016/j.jtusci.2016.09.011


texts: Constitutional Isomers or Stereoisomers?

texts:
With regard to a trigonal bipyramidal molecule, such as $\ce{PIBrClF_2}$, can there be any constituional isomers? I'm thinking no, because constitutional isomers differ in the connectivity of their atoms. The molecule only has single bonds. All are bound to a single central atom. There is no way for the connectivity of the atoms to change versus something such as ethanol, $\ce{C_2H_6O}$. I can think of two constitutional isomers off the bat:

$\ce{H_3CCH_2OH}$ and $\ce{H_3COCH_3}$ in which the connectivity of the atoms differ; in the former, we have a hydroxyl group; in the latter, we are missing the hydroxyl group.

Therefore, $\ce{PIBrClF_2}$ should not have any constitutional isomers but does have stereoisomers, correct?


texts: Can I completely dry air with calcium chloride?

texts:
I'm trying to dry air by leading it through calcium chloride.

I'm measuring the resulting humidity with a simple capacitive humidity sensor. I do not see measurements below 10% relative humidity, but it is quite possible that it is a result of a calibration error (The sensor is not actually calibrated.)

But how dry can I get air by exposing it sufficiently long to calcium chloride dihydrate?


texts:
Calculate concentration of $\ce{OH-}$ ions in $\pu{0.66 mol L^-1}$ solution of $\ce{NH4+}.$

I think that there might be something missing, as the only law I have for this kind of problems is

$$[\ce{OH-}]^2 = K_\mathrm{b} × C_\mathrm{b},$$

but is there a way to calculate $[\ce{OH-}]$ by using concentration of base only $(C_\mathrm{b} = \pu{0.66 mol L^-1}).$


texts: Justify the value of the product of the uncertainty in position and momentum

texts:
The Heisenberg uncertainty principle states that:
$$\Delta x\Delta p_x\ge\frac12\hbar$$
But more generally for operators $A$ and $B$:
$$\Delta A\Delta B=\frac12|\langle[A,B]\rangle|$$
However, $[x,p_x]=i\hbar$. With this information, I don't see how to get from the second equation to the first.


texts: How many moles of aspartame are present in 4.00mg of aspartame? (3 sig figs)

texts:
This is a part of my online chemistry homework (mastering chemistry)

I know how to do it but when I enter $\pu{1.36E-5}$ into the program, it says that it's incorrect and that the correct answer does not depend on $\times10$. I'm not sure what it wants from me. The answer should be given in moles with $3$ sig figs.


texts: When talking about conductivity in combination with lattice defects you can often see that AgX is taken as an example for a Frenkel defect where the $\ce{Ag^+}$ moves to intersticial voids. I remember that my professor once called this a property of silver, that silver likes itself so much that it can be close to other silver cations. And I think we see trends like this in for example $\ce{Hg2}$-dimers. Is this some sort of relativistic effect or can I explain it with certain orbitals overlapping that I can get a quite close contact for two $\ce{Ag^+}$ ions?


texts: Decomposition of potassium permanganate under prolonged heating

texts:
When we heat potassium permanganate, the equation of the decomposition of it is:
$$\ce{2KMnO4 ->[\Delta] K2MnO4 + MnO2 + O2}$$

So  what will happen to potassium manganate ($\ce{K2MnO4}$) when we continue heating?


texts: Material that changes solubility when electric potential is applied

texts:
I am looking for a material witch is easy to deposit in thin films and which changes its solubility if a electric potential is applied.

Do you know of any such materials ?

EDIT: This is for what I need it.
I have a Si Substrate on which there is sputtered SiO2.
Then I have the material (to be found) and then a Si on top. Some parts of the Si are connected electronically to the bottom Si and create a electric potential. The orange material underneath the top "electrodes" should be removed. The aim is to remove the "orange" material underneath the top "electrodes" but keep it where the Si is not connected to the bottom electrode.

How could you do this ?

EDIT2: please Igore the spelling error in the bottom electrode. It should be "connected"

EDIT3: based on Alchimista's answer:


texts: How to create the total reaction out of the two steps behind denitrification?

texts:
I can see that denitrification consists of processes involving mainly two steps:
Step 1 (nitrate to nitrite):
$$ \ce{3NO3- + CH3OH -> 3NO2- + CO2 + 2H2O} $$
Step 2 (nitrite to molecular nitrogen):
$ \ce{2NO2- + CH3OH -> N2 + CO2 + H2O + 2OH-} $$
Total reaction is supposed to be:

$$ \ce{6NO3- + 5CH3OH -> 3N2 + 5CO2 + 7H2O + 6 OH-} $$

Now I'm a bit rusty.
As far as I can remember, the right hand side on the first step of the reaction will be the starting point for the left hand side of step 2 in the overall reaction process.
In other words, what is present on the right hand side of step 1 and on the left hand side of step 2 can be subtracted from each other (which is logical). Also, the start of the total reaction would be represented by the left hand side of step 1 and the end of the total reaction would be represented by the right hand side of step 2.
The coefficients 5 and 7 seem very strange, but they balance everything so that makes sense. However the balancing of the Os seem to be the challenging part.

The attempt yields:
$$ \ce{3 NO3- + CH3OH -> N2 + CO2 + H2O + 2OH-} $$
Balancing N:
$$ \ce{6NO3- + CH3OH -> 3N2 + CO2 + H2O + 2OH-} $$
C and H atoms are already balanced.
However balancing O is more complicated because changing any of the Os affects the balance of the others (like C, H). Are there any recommendations for easing out that process or methods that can be applied in general?


texts: Can a solid be both crystalline and amorphous?

texts:
The first line in the Wikipedia article for "Glass" reads:

Glass is a non-crystalline amorphous solid that is often transparent and has widespread practical, technological, and decorative usage in, for example, window panes, tableware, and optoelectronics.
 Emphasis, mine.

From what I've been taught at school, if a solid is amorphous then it is necessarily non-crystalline and vice versa. (Of course, you could convert a given sample of an amorphous solid to some crystalline form...but it would no longer be amorphous now would it?).
The "non-crystalline amorphous" pleonasm adopted by Wikipedia seems to suggest the existence of (yes, I know this sounds stupid) crystalline amorphous solids.
Can something (I'm using glass as an example) be both "crystalline" and "amorphous?"
If not (as I suspect is the case), then why does Wikipedia use the pleonasm "non-crystalline amorphous" when describing glass? Is it purely for emphasis?

Yes, I've already seen this question here, and no, my question's not a dupe of that.
Sure, it's possible to convert an amorphous solid to a crystalline solid (proper melting and cooling should do it), I'm not questioning that.
What I am questioning, is whether a crystalline amorphous solid can exist. For example, glass has both (non-crystalline) amorphous  and crystalline (non-amorphous) phases.... but does it have crystalline amorphous phases? Yes? No? Why?


texts: How to properly denote imaginary magnitudes of vibrational frequencies

texts:
Vibrational frequency computations provide the magnitudes of vibrational frequencies for each vibrational mode of a molecule ($3N-6$ degrees of freedom for non-linear molecules and $3N-5$ for linear molecules).  Sometimes these magnitudes can be non-real (i.e. imaginary).  This is common when characterizing a transition state which contain one, and exactly one, imaginary mode of vibration.

Some popular software packages will print these magnitudes as a negative number.  This syntax has unfortunately propagated itself into common, everyday practice even if technically incorrect.

My question is, what is the best way to denote these imaginary magnitudes, especially in the context of a peer-reviewed journal?  Should we stick to using the minus sign convention (e.g. -15) with a note explicitly defining the meaning of the $-$ sign,  or should they simply be listed with an $i$  (e.g. 15$i$)?

(I've just been told to NEVER use the minus sign convention as this will incur the wrath of the reviewers.  Please feel free to verify.)


texts: Identifying probable compound using its colour & reactants

texts:
This is quote from OxyChem document on Hypochlorites:

  Steel tanks in caustic soda service become passivated with a
  gray-black film forming on the metal. Thereafter, caustic soda at less
  than 130° F will dissolve very little iron from the tank. The
  protective film should be preserved whenever practical. Therefore,
  when sediment is rinsed from a tank, only the bottom should be washed.
  Caustic Soda solution should then be put into the tank as soon as the
  washing is finished. Otherwise a soft rust will form and contaminate
  any future storage.

I cannot understand what can be this gray-black film chemical formula. Plus is he referring soft rust to common Iron (II) Oxide when it comes to O2 rich atmosphere. May be thats why he instructs to refill cleansed container as soon as possible?


texts: Is Potassium Silicate better than Sodium Silicate (water glass) in a refractory?

texts:
I would like to know whether Potassium Silicate is a better binder than Sodium Silicate in making refractory bricks.

A search on the internet on a 'vs' question relating to the two says that Potassium Silicate is more soluble, has lower efflorescence, lower tack, something about atmospheric dissolvers, none of which makes any sense to me. The only thing of interest was apparently Potassium Silicate can be used at marginally higher temperatures ($\rm50\, ^{\circ} C$).

Can I substitute Potassium Silicate for Sodium Silicate?


texts: Why would ethanol or water give poor yields in a peptide deprotection hydrogenolysis?

texts:
A homework question asks:

  The following reaction was carried out using ethanol or
  water as solvents, but gave poor yields in both cases.
  Suggest why this might be the case and how these
  problems could be overcome.

I've gathered that this is the deprotection step of a dipeptide synthesis reaction (Phe-Ser). The palladium catalyst and hydrogen gas remove the Cbz group from the n-terminal and the benzyl ester from the c-terminal, with a carbamic acid intermediate that spontaneously decarboxylates to the product.

I don't really understand why ethanol or water would give poor yields as a solvent, since I've seen multiple references where they use exactly those as solvents for this reaction (or methanol, or THF). The only hint I could find was a suggestion that using acetic acid may be necessary when deprotecting a Cbz group from an amine, since protonating the nitrogen facilitates the reaction. A couple of references said that an aliphatic amine could poison the catalyst and require the addition of dilute acid to protonate the amine...I'm lost on why or how the poisoning occurs.

A nudge in the right direction would be greatly appreciated.


texts: What is the connection between vapor pressure and intermolecular force explanations of boiling?

texts:
I've had boiling explained to me in two ways, and I'm having trouble understanding how they connect.

The first way is that a liquid is held together by the intermolecular forces, and boiling involves breaking those bonds/interactions. This explains why, for instance, the boiling point of water is higher than that of methane, but not why boiling point is pressure dependent.

The second way is in terms of vapor pressure. Boiling occurs when bubbles form, and in order for a bubble to form and not be crushed, its internal pressure must be equal to the atmospheric pressure. From this view, the boiling point is the temperature at which the vapor pressure equals the atmospheric pressure. This explains why boiling point drops as pressure drops.

My issue is understanding how these coexist. The way I think of it, the strength of the intermolecular interaction should be the same no matter the pressure, so the temperature to break those interactions should be constant. Also, you can boil a liquid just by lowering the pressure, but I don't see how this affects the intermolecular interactions in any way.


texts: What caused the flashes in the video footage of Chernobyl?

texts:
There is video footage of nearby villages in Pripyat, in the first week after the Chernobyl disaster. When I watch it there are villagers leading normal lives in normal clothing. Some Russian nuclear scientists pass by in full radioactive suits. Then there these clearly visible "flashes" in the air; I have looked on youtube but haven't found the video that I watched a long time ago. My layperson understanding is that these flashes are caused by an extreme amount of radiation.

Here's footage that shows the flashes in the air. They are subtle orangish flashes that are quick. But there's one for instance just after 3 minutes.
This isn't the original one that showed the flashes better. Anyway:
Chernobyl

From Wikipedia "Ionized-air glow":

  Within minutes after the steam explosion that caused the Chernobyl
  accident at 01:23 local time, a number of employees at the power
  station went outside to get a clearer view of the extent of the
  damage. One such survivor, Alexander Yuvchenko, recounts that once he
  stopped outside and looked up towards the reactor hall he saw a "very
  beautiful" LASER-like beam of light bluish light, caused by the
  ionization of air, that appeared to flood up into infinity.

My questions are:

What amount of radioactive material is needed to make those flashes in the air happen?
Is radiation alone enough?
Are other factors such as weather, temperature or other prior chemical elements in the air needed to allow this flashing to happen?


texts: Relaxed scan of Cp-M torsion angles of piano stool compounds

texts:
As part of a conformation analysis of a library of piano stool complexes to find global minima and TS, a relaxed scan where the legs of the piano stool complex rotated about the Cp-M bond need to be performed (Here a $\ce{[(Me-Cp)RuClH(CO)]}$ is given here to illustrate the task in question) :

However it was found that Gaussian 09 or 16 does not allow dummy atoms in redundant coordinates and cannot build dihedrals where one of the atoms is a dummy atom as far as Generalised Internal Coordinates (GIC) goes, because atoms are not considered an internal coordinate. Also unlike this question, since the rotation has to be done about the Cp-M bond,the workaround in that question will not work.
In addition, none of the existing dihedrals can be added together to give a dihedral where the middle bond will be aligned to the Cp-M axis. This means, the dummy atom for the centre of the Cp is necessary.

What are the possible workarounds that can achieve an outcome equivalent to the relaxed scan of the Cp-M dihedral?

Are there other chemistry packages that allow relaxed scan using dummy atoms or (better) user defined rotation axes?


texts:
Negative of the $\Delta G$ for a process is the maximum useful work that can be obtained from it (at constant pressure and temperature). I understood this in this way:  $\Delta H$ is the heat absorbed by the system (since the process is at constant temperature and pressure), so equivalently $-\Delta H$ energy is obtained from the system after doing expansion work. Since $\Delta S$ is the entropy created in the process, at the very least $-\Delta S$ entropy must be created in the surroundings - that is, at least $-T\Delta S$ energy must be lost as heat. This comes from the $-\Delta H$, and thus leaves $-\Delta H + T\Delta S$ to do useful work. No more work can be done than this. $-\Delta H + T\Delta S$ is $-\Delta G$, so $-\Delta G$ is the maximum possible useful work. First of all, I wanted to know if this is correct, and if this is actually why $-\Delta G$ is the maximum possible useful work.

Now if $|\Delta H|$ is more than $|T\Delta S|$, with both being negative, then one can think of the $W_{max}$ or $-\Delta G$ as a part of the $|\Delta H|$; since $|\Delta G|< |\Delta H|$. Some part of $|\Delta H|$ goes as $|T\Delta S|$ to increase the surroundings' entropy, and the other part in doing useful work. But if both are positive, with $|T\Delta S|$ being more than $|\Delta H|$, again $\Delta G$ is negative, allowing useful work to be extracted. But now it seems as though $|T\Delta S|$ heat will be extracted from the surroundings, $|\Delta H|$ used up in the process, while the rest can be converted to work - in other words, useful work is a part of $|T\Delta S|$ - with the other part used by the process as $|\Delta H|$. Is this correct? Is $|T\Delta S|$ extracted from the surroundings actually?


texts: Issue: removing through dissolution a thin (2-4 mm) iron carbonate crust covering fossilized bone without damaging the bone.  Microblasting with conventional baking soda ineffective; removal of iron carbonate with mini-pneumatic air chisel also removes top layer of bone with the iron carbonate crust. Any solutions would be appreciated.


texts:
Find the product of the reaction of dimethyl ketone i.e. $\ce{CH3C(O)CH3}$ with $\ce{NaNH2}.$

Should I do nucleophilic addition and form the product in the picture?


texts: Determine heat flux from temperature profile

texts:
The heating
  element and the insulator are of equal thickness L. Heat transfer in
  the air film adjacent to the heater is assumed negligible.

I've noticed that I find these type of problem the hardest to understand, so before I ask my question, does anyone know a good video or website which explains in detail how you should interpret temperature/concentration profiles?

My answer to (a) would be that both of the points should have the same heat flux. I know that one of the relationships used for layered wall is that q=constant, meaning that it is the same through every layer, however is that the correct way of thinking for this problem? I don't think so and don't understand how I should interpret the profile.

Another way I thought about it was that the heat flux for the layers should be:

$$q_1=(k_1/L)\cdot(T_\text{rear} - T_{12})$$
$$q_3=(k_3/L)\cdot(T_{23} - T_\text{front})$$

and that:

$$k_3>k_1$$

$$(T_\text{rear} - T_{12})\gt(T_{23} - T_\text{front})$$

If I just for simplicity assume that $L=1\ \mathrm m$. Then I would get that

$$q_1=(\text{something small})\cdot(\text{something big})$$
$$q_3=(\text{something big})\cdot(\text{something small})$$

Hence another reason why I think that the heat fluxes are the same.


texts: Is there no irreversible way of moving between two equilibrium states at constant T and P?

texts:
There's a reaction occurring at constant $T$ and $P$, and it is in chemical equilibrium. Now by adding infinitesimal quantities of reactants, it is taken to another equilibrium state in a reversible way. During this process, if entropy change is $\Delta S$ and volume change $\Delta V$, $$\Delta U = T \Delta S - P \Delta V.$$
If the same process is carried out irreversibly, by suddenly adding a large quantity of the reactants and disturbing the chemical equilibrium, then the work still remains $P \Delta V$ ($ \Delta V$, a state function, has the same value). In that case, the heat $q=T \Delta S$, which is only true for reversible processes. Even though the process is irreversible, there has been no entropy change in the universe? Where am I going wrong? It can only be that the work is not $P \Delta V$, but since the process is at constant pressure, the work should have this value.


texts: Differential equation for the rate of unimolecular reaction

texts:
Given in my book is the following reaction mechanism for the unimolecular $\ce{A -> B + C}$,

$$\ce{A + M ->[k_1] A^* + M} \\ \ce{A^* + M ->[k_2] A + M} \\ \ce{A^* ->[k_3]  B + C}$$
Here $A^*$ is an $A$ molecule with enough vibrational energy to isomerize or decompose. In other words, part of kinetic energy of a bimolecular collision (between $A$ and $M$) has been used to raise an  $A$ molecule to higher vibrational energy.
Since $A^*$ is never present at very high concentration we can use steady state appoximination to obtain an expression for rate of reaction in terms of $[A]$ and $[M]$.
$$\dfrac{d[A^*]}{dt} = k_1[A][M] - [A^*](k_2[M] + k_3) = 0\tag{1}$$
$$-\dfrac{d[A]}{dt} = k_3[A^*]\tag{2}$$

I don't understand how the $(2)$ equation is obtained, in my opinion it should be $$-\dfrac{d[A]}{dt} = k_1 [A][M]- k_2[A^*][M].$$
I did not understand how we get $k_3$ instead of $k_1$ and why not $[M]$ in the rate law ?


texts: Attempting to balance a redox reaction using half reactions leaves an unbalanced component

texts:
I have this redox reaction that I can't balance using half reaction method.

$$\ce{Mg + HNO3 -> Mg(NO3)2 + N2O + H2O}$$

What I get at the end is

$$\ce{2Mg + 6HNO3 -> 2Mg(NO3)2 + 3N2O +3H2O}$$

I can't get the $\ce{N}$ balanced.


texts: Where is the probability of finding an electron in 1s orbital maximum?

texts:
So the way I understand the question is that it asks us at what r (distance from nucleus) and at what angles is the probability going to be maximum. The way I see probability of finding at a point in a meaningful sense is, just like in 1D probability of finding particle at a point is taken as probability it is in dx region beside it, we find probability of finding it in a small volume near the point of interest.
Now the probability density of 1s orbital times dV in polar coordinates will end up containing a sine term (since small volume in polar cooditnates contains sine of angle with z axis). Thus the probability is dependent on not just r but also angle with z axis, which isn't expected for such a spherically symmetric orbital. I am confused here.

Of course one could say that since this is spherically symmetric, probability depends only on r and thus use only radial probability distribution and maximise it. But why is the above way which seems more general giving an apparently different answer.

Sorry if the above part isn't clear or is messy. Just to clarify things, I am not asking a "how to find" question. One way to look at my question is that if instead of maximising radial probability distribution, if I evaluate probabilities in small volume around points and maximise it, my answer should match with the one I get from maximising radial probability distribution. Consequently, I should get all points on sphere with Bohr radius but on maximising probability in small volume around a point, I get points at Bohr radius and on XY plane only (since for maxima, sine must be 1 meaning perpendicular to z axis).


texts: Can polyatomic ions (CO₃, PO₄, SO₄, NO₃) be considered conjugated systems?

texts:
From my perspective these resonance structures allow these specific polyatomic ions to act as donor-acceptor molecules. Many donor-acceptor molecules also tend to be conjugated systems because they have chains of alternating conjugated π orbitals.

So does this imply that these ions (due to their resonance structures) can act as though they had a conjugated system or am I making too big of an assumption?

Curious on others perspectives/if I'm totally of my rocker.


texts: Turning of a paddle wheel when exposed to light

texts:
So, we observe that in the discharge tube experiment when a very light paddle wheel is placed in the path of cathode rays, it starts turning due to the particle nature of the rays.

My question is if the same paddle wheel is placed in light, why does it not start turning ?
Light is also of particulate nature (in some cases- made up of photons).
Is it due to the less mass of photons?
Thanks.

Edit:-

Thank you, particularly @Poutnik for giving me such great answers.

I just read an article while researching that the paddle wheel didn't turn because of the transfer of momentum by the cathode rays but due to changes in pressure of the gas around the paddles due to heating, which is much same as that to Crookes radiometer.
This fact was discovered later, much later after the experiment.
This solves my problem that even in the cathode ray experiment, it wasn't the trasfer of momentum that moved the paddles, because the actual pressure of the rays is quite weak (again as suggested by @Poutnik). And since the ray can't turn the paddles, the light no way can.
And yes, I calculated the momentum of sunlight and that transferred by cathode rays to see for myself that movement of the paddle by each of these is not possible.

Thanks everyone once again.


texts: What are the ways to make radioactive water drinkable again?

texts: Let's say survivors in the area contaminated by radioactive fallout need to somehow process the water from rivers, rain or pipes. How could they go about it? Is it even possible to 'remove radioactivity' from the water?


texts: Which chiral carbon do L and D in L- or D-glucose refer to?

texts:
I see and D- and L- glucose are mirror images of each other. and I understand D and L are for chirality. But it is not clear which carbon do D and L refer to. Could anybody let me know? Thanks.
What are the differences between D and L glucopyranose?


texts: hypo residual chlorine testing using a 10ml reagent pack

texts:
Why when testing a sample for chlorine residual do I get the same results for 5 ml sample of water as I do with a 10 ml sample, and a 15 ml sample of water using a reagent pack that asks for a 10 ml. The reagent container does not give the weight of the reagent in the packet (it is powder), but I think it might weigh 0.1 grams. I am just using a Hach DR 900 to test the free chlorine residual.

My thinking is if the reagent packet is asking for 10 ml sample of water shouldn't my results differ when using different sample sizes. For the three different volumes of samples, I got a free chlorine residual of 1.00 mg/L for all three sample sizes.

Sorry, the packet is a DPD free chlorine reagent for 10 ml sample. The packet contains Sodium Phosphate, Dibasic, EDTA Disodium Salt, DPD Salt, and Carboxylate Salt.


texts: Why are Buckminsterfullerene (C60) solutions pink/purple?

texts:
A solution of Buckminsterfullerene $\ce{(C60)}$ is shown below:

According to the April 8th Wikipedia page on Buckminsterfullerene $\ce{(C60)}$:

  Solutions of pure C60 have a deep purple color which leaves a brown residue upon evaporation. The
    reason for this color change is the relatively narrow energy width of the band of molecular levels
    responsible for green light absorption by individual C60 molecules. Thus individual molecules
    transmit some blue and red light resulting in a purple color. Upon drying, intermolecular
    interaction results in the overlap and broadening of the energy bands, thereby eliminating the blue
    light transmittance and causing the purple to brown color change.[36]

Now, I'm not too bright in the field of quantum chemistry/electrochemistry, so this doesn't click with me very well. Does anyone have a good way to explain in layman's terms why the $\ce{C60}$ solutions appear pink/purple? I'm very curious why they experience such a definite color absorption when they are made solely of carbon atoms, while most organic dyes have a host of other heteroatoms and functional groups. Also, why do they exhibit a very specific absorption only when in solution? Any and all contributions are greatly appreciated.


texts: Determine the order of the reaction, and the value of the rate constant. Predict the concentration of AB at 25s

texts:
I've never posted a question about chemistry before so I'm not really sure how this community works but here is the question.

I do have the answer to this question but I have no idea on going about solving it.

I do know:

that second order is equal to all of the exponents added up
Rate is equal to $k[A]^{p1} [B]^{p2} $
Rate is also equal to $([A_2]-[A_1])/([t_2]-[t_1])$

And I believe $M$ stands for molarity.

I have little to no idea how I am to solve this other than those 4 things.

Here are the answers the book gives me:

Second Order
$k = 2.25\times 10^{-2}$
$[AB]$ at $25s = 0.619 M$


texts: Can nuclear shielding affect relaxation time?

texts: Can nuclear shielding affect the transverse relaxation time, i.e extend the relaxation time the more the nuclei is shielded?


texts: Probability of finding a molecule in the ground vibrational level

texts:
I wanted to estimate the probability of finding a molecule in the ground vibrational level using the Boltzmann distribution:

$$
p_i = \frac{e^{-\epsilon_i/kT}}{\sum_{i=0}^{N}e^{-\epsilon_i/kT}}
$$

Using the quantum harmonic oscillator as a model for the energy

$$
\epsilon_i = h\nu (i+1/2) =/i=0/=\frac{h\nu}{2}
$$

In the Boltzmann distribution, we have the state of interest divided by the sum of all possible states. But how should I treat the denominator?

Searching a bit I found that the analytical expression for this geometric series is ($i$ not imaginary number)

$$
\sum_{i=0}^{N}e^{-i h\nu/kT} = \frac{1}{1 - e^{h\nu/kT}}
$$

However, is this using a shifted energy scale for the harmonic potential? In that the vibrational energies are $0$, $h\nu$, $2h\nu$, ..., and not $\frac{1}{2}h\nu$, $\frac{3}{2}h\nu$, $\frac{5}{2}h\nu$, ...? Should I make sure I use the same energy scale for the nominator and denominator in the Boltzmann distribution?

Doing what porphyrin suggested, I get

$$
\sum_{i=0}^{\infty} e^{-h\nu(i+\frac{1}{2})/kT} = e^{-h\nu/kT} \sum_{i=0}^{\infty} e^{- ih\nu/kT}
$$

Expanding the four first terms

$$
e^{-h\nu/kT} \sum_{i=0}^{\infty} e^{- ih\nu/kT} = (e^{-h\nu/kT} \cdot 1) + (e^{-h\nu/kT} \cdot e^{-h\nu/kT}) + (e^{-h\nu/kT} \cdot e^{-2h\nu/kT}) + (e^{-h\nu/kT} \cdot e^{-3h\nu/kT}) \\
= e^{-h\nu/kT} + e^{-2h\nu/kT} + e^{-3h\nu/kT} + e^{-4h\nu/kT} = \sum_{1}^{\infty}e^{-n\cdot h\nu/kT}
$$

which has an analytical expression for the converged value, right?


texts: What is the meaning of "equivalent weight" and its formula?

texts: What is meant by "equivalent weight" and how does its formula E=M/V support the definition?


texts: How many atoms are represented in this equation?

texts:
$\ce{Pb(NO3)2 + 2KI -> PbI2 + 2KNO3}$

The answer says 26, but shouldn't it be 13? Because actually, the number of atoms involved in the reaction are 13, and once the reaction is completed, again, number of atoms is 13.
Please explain.


texts: Finding the sensitivity of zero-order ultra sensitivity and its parameter dependence

texts:
I am provided a one-dimensional reaction system showing zero-order ultra sensitivity.
$$\ce{X_1 ->[f_1] X_2}, \quad \quad \quad \ce{X_2 ->[f_2] X_1}$$
The reaction rate function is the reduced enzyme reaction according to Michaelis-Menten's law.
$$f_1(x) = E\left(\frac{x_1}{K_1+x_1}\right)$$
$$f_2(x) = \left(\frac{x_2}{K_2+x_2}\right)$$
$$K_1=K_2=K$$
$$x_1(t) + x_2(t) = x_0$$
where $x_0$ is a constant. Let the steady state of $x_2$ be denoted by $x_2^{\text{st}}$. I need to find the value of $E$ that satisfies
$$x_2^{\text{st}}(E) = \frac{x_0}{2}$$
and the logarithmic sensitivity. I tried to look into some published papers/textbooks but could not find similar problems. Can anyone give some suggestions on directions to look into?


texts:
My book says:

  In a solution consisting camphor and nitrogen gas, camphor (solid) is solute whereas nitrogen gas is solvent.

Doesn't this contradict the statements that:
(1) Generally the component present in large proportion is the solvent.  I mean camphor will be in larger proportion as it is a solid. We can diffuse much nitrogen gas.
(2) Solvent determines the physical state in which solution exists. If nitrogen is solvent, then how can the solution be in gaseous state? Or if the statement is true, does that mean that the solution exists in gaseous state with camphor particles of collidial size?


texts: Why do halogens have odd numbers as oxidation number?

texts:
Halogens like $\ce{Cl}$ always exhibit $+7,+5,+3,+1,-1$ as their oxidation numbers. I found the following answer after checking several sources:

  Halogen atoms have $7$ electrons in their valence shell, so $1$ of those electrons is spin unpaired, which is an unstable situation. If an even number oxidation occurs, said even number of electrons are taken away, leaving still an odd number of electrons with at least $1$ unpaired. Taking away an odd number of electrons leaves an even number of electrons with the opportunity of them to be all paired.

These oxidation numbers are observed in compounds like $\ce{HClO4}$ and $\ce{HClO3}$. We know that, before forming these compounds, the valence electrons of $\ce{Cl}$ are excited into the d orbitals. Thus now, they are not in ground state, but in the excited state instead.

The quoted explanation is giving the reason for my question on the basis of the ground state of halogens. (I especially consider $\ce{Cl}$). But we know that, before formation of compounds, the halogen atoms are in their excited state instead.

So is the quoted explanation correctly justifying why $\ce{Cl}$ exhibits odd oxidation states only?


texts: What is the correct IUPAC nomenclature for the coordination compound $\ce{[CoSO4(NH3)4]NO3}$?


texts: How can I emulsify Beeswax with Aloe Vera Gel?

texts:
I was looking thru ingredients for non-silicone based makeup primers and two ingredients always seem to be used: aloe vera gel and some type of wax, like jojoba wax, plus some type of oil to thin out the consistency like sweet almond oil or apricot kernel oil.

I thought it'd be interesting to see if it'd be possible to see if I could make my own, not least the companies that make them charge an arm and a leg for them.

My question is: what procedure and chemicals would you use to emulsify aloe gel with beeswax to make a cosmetic?

I vaguely remember that borax is used to make cold cream, maybe that'd come in useful?


texts: When nitric acid is protonated by sulfuric acid, why is the hydroxyl group protonated? There are two other possible oxygens with partial negative charge that would seem to be better proton acceptors.


texts: Why does the reduction of Dichromate to Chromium 2 need an acid?

texts:
The Ecell shows that Zn is enough. Then why, are both of them required?
Also, can I use any acid ? Or only HCl + H2SO4


texts: Where I went wrong and got an unwanted reaction

texts:
I want to apologize for my bad English - but there was no one to turn to.

I had begun to etch a printed circuit board and used 100ml. 3% H2O2, 2 tablespoons of citric acid, 2 tablespoons  NaCl.
After insertion of the printed circuit board - start reaction and the liquid turned blue, but in the middle saw that is less quantity and add hot water and the reaction stopped.
I noticed there was dirty on the circuit board and I removed it with a carpet knife. It immediately became red in contact with the liquid.
I poured the liquid into a plastic box and dipped a washed carpet knife and go to the pharmacy to buy H2O2

But I made a mistake because I bought 30% H2O2. I made a new liquid with 200ml. H2O2 and citric acid and NaCl. The PCB reaction was much faster. After I finished and pulled out the PCB , I wanted to see if more honey would be deposited, and I took the same knife I had dipped into the front solution and immediately got wet and the knife became black. A reddish froth floated on top of the surface. I went to wash the printed circuit board with water and heard some noise. I came back and some smell terrible and my eyes were red, I was breathing hard while I was throwing the liquid out and blowing.

The first day my eyes were watered and my sun was irritating, and in the shade everything was fine. The second day the sunlight did not irritate me, but when I looked at the light, I see something about the lamps that comes out when there is evening fog and looks at the lamp. On the third day I'm better and the vision returns.

What chemical reaction has occurred when:
H2O2 + citric acid + NaCl + Cu + Fe (I guess there are other substances in the mock knife)


texts: Why does Nitrogen form N₂ (and not N₄) while but Phosphorus forms P₄ (and not P₂)?

texts:
$\ce{N2}$ is a gas
$\ce{P4}$ is a solid
$\ce{N}$ and $\ce{P}$ are in the same group in the periodic table

The bond enthalpies are:
$\ce{N#N}$ triple bond is $949~ \mathrm{kJ/mol}$

$\ce{P#P}$ triple bond is $490~ \mathrm{kJ/mol}$

$\ce{P-P}$ single bond is $200 ~ \mathrm{kJ/mol}$

$\ce{N-N}$ single bond is $159-296 ~ \mathrm{kJ/mol}$

So why does $\ce{P}$ go to $\ce{P4}$ not $\ce{P2}$ and why does $\ce{N}$ go to $\ce{N2}$ and not $\ce{N4}$?


texts: Cross-conjugation and aromaticity in pyrene

texts:
I have read about non-huckel double bonds and clar's rule, but what made me confuse is that huckel's perception gives me the feeling that central bonds in polycyclic aromatic hydrocarbons (ex: pyrene) is simply minimally affecting  aromaticity or even dropped off, while clar's rule shows different resonance forms which in total makes a complete sextet formed in each ring of pyrene.

So how could i resolve this issue?

what would happen to aromaticity if simply the central double bond was not in the pyrene?

is there any cross-conjugation involved? and how would cross-conjugation affect aromaticity?


texts: Is there any reason to fear personal exposure to rain with a pH of 3.1?

texts:
Where I live now there can be significantly acidic rain. The government posts measurements for many cities and there can be stretches for days or longer with reported pH of 3.2 or 3.1. I even saw 2.9 reported once.

While this can have quite serious environmental effects depending on a number of factors including total rainfall, geology, geography, soil composition just to name a few, my question is about the direct effect of rainfall this acidic on people and their possessions.

Just how dangerous or deleterious to people and their immediate possessions (e.g. clothing, other objects) would getting a bit of pH 3.1 rain on oneself actually be? Would it sting at all if it got in the eye? Discolor hair? Is there any basis at all to being collectively phobic of being touched by this rain specifically because of its pH?

I've tried searching the internet but there is a jumble of information there. As far as I can tell, pH 3.1 seems to be somewhere between a soft drink, and tomato juice, but this is from unreliable sources.

So I thought I would ask in Chemistry SE for a solid, scientific answer. I'm not looking for an opinion, or a reasoned answer (e.g. "if it was that dangerous, then..."). I'd prefer factual data, or references related to safety and effects of topical exposure to (mildly) acidic water.


texts: Is a combustion necessarily a redox-reaction or can there be exceptions?

texts: I have a feeling that I have heard of an exception - either based on the material or the oxidizer.


texts: Help understanding the following conversion

texts: I am given the substrate and reagents in steps (1,2,3). I am asked to figure out the product! I am not sure how the reagents in 2 (aq. Na2CO3) and 3 (NaH, MeI/DMF) work to give that answer. Why is the answer what it is?


texts: What substances are typically used to produce cyan, magenta, and yellow ink?

texts:
Early in grade-school you learn blue, red, and yellow are the primary colors that can be used to produce any other color. If you're curious enough, you later learn the primary colors are actually cyan, magenta, yellow and -- for practical purposes -- key (black).

My question is, what substances are used for each of these pigments and where are they found? Are they synthesized?

To be concrete, what substances are inside the in CMYK inks found in desktop inkjet printers?


texts: What is viscosity in terms of chemistry?

texts:
In physics, viscosity is the force applied in a unit area times time or basically Pascal times second. We could say that it is a measure of its resistance to gradual deformation by shear stress or tensile stress.

But what does it mean in the chemistry world?
I believe it is related to the distance between molecules in a solution. When molecules are farther apart then viscosity is lower than when molecules are closer.

Could you tell me if my mature concept about viscosity is on the right track or far too off? Could you also define viscosity in terms of chemistry?


texts: Absence of π–π* transitions with presence of CT transitions

texts: An aromatic compound with a large number of delocalised electrons gives several distinct UV-vis absorption peaks, due to the many π–π* transitions that can occur. However, when complexed to transition metals, a CT peak appears, and all the π–π* peaks disappear. If the system still has a large number of conjugated π-bonds, why do these peaks disappear?


texts:
I'm looking for a way to take 3 separate liquids (liquids which function as paint -- they will all be different colors), put them together into a container, and then rapidly separate them back to distinct colors.

I can handle all the electrical engineering aspects of my project, but this portion is beyond me. Does anyone have any ideas?

When I say "a quick method", I mean something that can be done easily without an excess of time or equipment. Ideally an way to make the paints intrinsically immiscible, but I need to be able to separate them entirely, so that when they are poured together into a container, I can then separate and reuse them.


texts: Experimental calculation of solubility product constant

texts:
In order to calculate the $K_\mathrm{sp}$ of lead(II) iodide, I mixed $\pu{6.0 mL}$ of $\pu{0.01 M}$ $\ce{Pb(NO3)2}$, $\pu{6.0 mL}$ of $\pu{0.02 M}$ $\ce{KI}$, and $\pu{8.0 mL}$ of water, and a precipitate (barely) formed.

From this, I calculated $[\ce{Pb^2+}]$ to be $\pu{0.0036 M}$ and $[\ce{I-}]$ to be $\pu{0.0060 M}$, giving

$$K_\mathrm{sp} = [\ce{Pb^2+}][\ce{I-}]^2 = 1.1 \times 10^{-7}.$$

However, the actual value (at $\pu{25 ^\circ C}$) is $7.9\times 10^{-9}$ (Skoog et al. Fundamentals of Analytical Chemistry), so my result is off by a factor of $\sim 10$.

I'm pretty sure I had clean equipment and measured carefully and accurately. Why is there a discrepancy? Is my maths wrong, or are there some inaccuracies in my experiment?


texts: Can an element have variable oxidation states in a compound?

texts:
Take propanoic acid for example. If I assign oxidation states to the 3 carbons in it using the idea that the more electronegative element gets all the electrons in the bonds it makes, the 3 carbons get -3( the one in the CH3), -2( the one in the middle), and +3( the one in the acid group).

Is this conclusion correct? The reason I doubt is that all the examples we've ever been given in class, we've assumed all the atoms of the same element to have the same oxidation state.


texts: I was reading a book on organic chemistry by David Klein and I came across this question, but I wasn't able to understand why one amine is more acidic than the other.


texts: Is there a preferred way of naming the resonance hybrid in keto-enol tautomerism?

texts:
While answering a question about keto-enol tautomerism the question arose, how can I refer to the resonance hybrid instead of on of the resonance forms. In the case of the deprotonated butane-2-one, I can name 1 3-oxobutan-2-ide and 2 but-2-en-olate (ignoring stereochemistry). I cannot come up with a name for the hybrid 3.

While this might be quite a simple case, there are many resonance stabilised structures out there, which have contributions from more than one form. It gets especially complicated for ionic substructures. I wondered if there is either already an official recommendation (preferred IUPAC name), or any other suggestion at all handling those cases. After all, we are treating the same bonding situation with two different names, there should be something that covers both (multiple) cases.


texts: How can I obtain crystal-clear glycerin?

texts: I'm trying to get perfect crystal clear glycerin for my experiments with decorative soap. Is there a special way to get it or should I buy a special formula of it? I have not succeeded in purifying the glycerin I have to more than a milky-translucent, semi-transparent soap.


texts: Is there a free online resource where I can get the solubility of a solute in a solvent?

texts: I'm looking for a online resource that lets me find the solubility at of any solute (e.g Choline Chloride, Sodium Hydroxide, Dextrose) in any solvent (e.g. Ethylene Glycol, Oleic Acid, Isopropanol, Water). Preferably, I'd like a webpage that lets me enter solute and solvent, then gives the answer, but even just lookup tables would be helpful.


texts: Splitting across a double bond in ¹H NMR

texts: Why do the Hs in (E)-1-bromo-2-chloroethene split into doublets instead of staying as a singlet. Wouldn't they be isolated from each other since the double bond does not rotate?


texts: Do aprotic solvents "slow down" SN1 reactions?

texts:
SOLVENT EFFECTS. Predict if using the polar, non-protic, solvent N,N-dimethylformamide (DMF, $\ce{Me2NC(=O)H})$ will speed up or slow down the following reactions and BRIEFLY justify your answers.
a)

b)

I have no doubt that b) takes $\mathrm{S_N1}$ pathway, but would DMF actually "slow down" this reaction? I want to be meticulous; I wonder if aprotic solvents "slow down" $\mathrm{S_N1}$ reactions or just regarded as not so ideal solvents for $\mathrm{S_N1}$ reactions. The wording of the question made me wonder.


texts: What type of reaction is the reaction between an acid and a carbonate?

texts:
Consider the following reaction:

$$\ce{2HCl + Na2CO3 -> 2NaCl + H2O + CO2}$$

Is this a double displacement reaction or a decomposition reaction?


texts: Are modern newspaper inks a health risk?

texts:
It's very common in India to see newspapers being used to absorb oils from oily snacks, or simply for temporary food packaging. Some articles say that covering food items in newspaper is a health risk. They also mention that using newspapers for these purposes are strictly disallowed. For example:

Eating food wrapped in newspapers can cause cancer!

  Newspapers and cardboard boxes used for packaged foods are made of recycled paper that may be contaminated with harmful chemicals like diisobutyl phthalate and di-n-butyl phthalate which can cause digestive problems and also lead to severe toxicity.
  Recycled paper also has printing ink residues trapped from previous prints. These trapped residues have found to contain hormone disruptors like benzophenones and mineral oils.

Dangers of eating newsprint

  Canned food and drinks, newspapers used for packing food, cosmetics like eye makeup, hair dye, sindhoor, lead-based paints, ceramic glazes, industrial emissions, exposure at battery units, diety-making units, and tea are all potent media for lead poisoning.

Healthy eating : Watch out for poisonous packaging

  Exposure to a class of organic chemicals called arylamines, such as benzidine, 2-Naphthylamine and 4-Aminobiphenyl, is associated with high risks of bladder and lung cancer. Apart from these, printing inks also contain colorants, pigments, binders, additives and photo-initiators (used for speeding up the drying process of the ink), which have harmful effects.

I am highly inclined to believe these articles and therefore I strongly advise against using newspapers as absorbent paper and packaging paper.

But I read some articles that say that the West has now implemented strict regulations and therefore modern newspaper inks are safe.

So I've come here to clear my confusion. Are they safe now?

What chemicals do modern newsprint and the ink contain exactly?
Are they still toxic?


texts: Using Nanodrop for UV/Vis analysis of compounds at limited amounts

texts:
I am no chemist, but a biologist who knows some biochemistry. I have some natural extracts at limited quantity, which I have been evaluating using mainly GC-MS. These extracts are rich in liquid alkaloids.

I was wondering whether a trivial "Nanodrop" could help me in some analyses  -- e.g. estimating concentration of some main compound --, via UV/Vis absorbance scans. A typical nanodrop can scan for absorbance within the range 200-800 nm.

Usually molecular biologists are the only ones routinely making use of Nanodrop, strictly for DNA/RNA purity and quantitative estimations.

Has anyone here ever tried making use of a Nanodrop micro-spectrophotometre for general analytical purposes with other compounds?

[UPDATE]

I cannot add an answer as others for some reason closed it as "too broad". It isn't, see below.

After completing my tests, I have decided to come back to answer my own question.

A Nanodrop machine has served my purpose quite efficiently, as far as I can judge. I used have used it to evaluate the degree of purity of a natural alkaloid extract from insects, using synthetic alkaloid analogues as controls. See our published paper discussing the method here, along with raw data.

We have noticed no alterations nor cross-contaminations to other DNA/RNA samples running in parallel, highlighting on the fact that the equipment was properly cleaned between each use (with 100% ethanol & distilled water).

Therefore, yes: I recommend using the Nanodrop as a cheap & quick method to scan alternative biological/chemical samples, provided the chemicals and solvents involved are compatible with the pedestal according with the manual.

Hope this discussion encourage others to dare into multidisciplinary research!


texts: What happens in an exothermic reaction at the atomic level?

texts:
Exothermic Reactions are those chemical reactions in which heat is released.

How does this happen?

What I mean is where does  the heat energy come from? Which form of energy is converted to heat energy? What makes some reactions release heat? What affects the amount of heat energy released?

Thanks!


texts:
There is a poor quality photo in the diagram of a manometer below:

The picture is too poor for me to understand what they mean by "glass pointer marks calibrated volume".  I would be interested if anyone (a) knows what this is - preferably with a manufacturer's number so I can inquire further or (b) has a higher quality image of the part.


texts: Why do hairs (rubbed with plastic comb) fallen on water seems to be sticking?

texts:
I was observing from many days, how hairs seems to be sticking to water, when made to fall on it. I made an attempt to know what really was going on. I kept a jug of stationary water under the light, and kept my dry hairs combing, to make hairs fell on it. I observed once again that hairs appeared to be sticking to water.

I started thinking about the cause for this observation. At first, what went to my mind was about hairs being rubbed with comb. Usually hairs get positively charged (I don't know exactly. I thought it because plastic becomes negatively charged when rubbed with most of  other suitable surface) when rubbed with plastic comb. We also know that water has more negative charge because of oxygen atom (I came to know about this from the diagram of wiki encyclopedia-electronegativity). So, I thought positively charged hairs might be attracted by negative charge nature of water molecules, which might be making hairs to stick with water.

Is it really because of positively charged hairs and negatively charged water molecules, which is making hairs to be sticking to water?


texts: What is exactly the pH value of distilled water?

texts: This was asked by one of my students in my class. I know it is the pH of 7, but others say it can be 6.55 pH


texts: What's the best way to interconvert between molarity and percentage?

texts:
Let's say that I want to convert concentration of an acid from % to molarity.
One way I found to do this is by using the following formula:
percentage = (molarity * molar mass) / 10.

Another way is to use an equivalency chart like this one (see bottom of page): http://www.ochemonline.com/Acid_and_Base_Concentrations

For example, to convert 38% HCl to molarity I calculated:
38% = (molarity * 36.46) / 10 and molarity = 10.42 = 10 M.
However, the equivalency chart says that 38% is actually 12.4 M.

The same discrepancy happened when I tried to convert 68% nitric acid molarity. Using the equation, I got molarity to equal 11 M, however, according to another source 68% nitric acid is closer to 15 M.

So my questions are:

1) Is there something I'm doing wrong that I get such a huge discrepancy?

2) What's the best way to figure out molarity from % and vice versa?


texts: Difference between lab-grade and food-grade purity?

texts:
What is the difference in purity betwen lab-grade and food-grade when talking about potentially consumable compounds?

As an example let's take ascorbic acid powder: if it's marked as lab-grade, does that mean it is also fit for consumption?

In particular, I'm wondering whether lab-grade supersedes (and/or improves) a food-grade labeling, or if they are two totally different criteria? Can I say lab-grade > food-grade?

If I can't say lab-grade > food-grade, then what is the actual difference between the two?


texts: How do I determine the amount of Calcium in a substance using EDTA titration?

texts:
I need to determine the amount of calcium in a substance (that also contains Magnesium) using EDTA titration. From what I understand, this can be done by adding Eriochrome T indicator to the solution, then titrating it with EDTA. The solution will start out Red then turn blue as the Ca ions bond with the EDTA. Many of the labs I search up online seem to follow these procedures. However, doesn't Magnesium also bond with EDTA? Wouldn't that affect my calculations since I'd be measuring Ca AND Mg as they both bind with both Eri T and EDTA?

Thanks


texts: What is the difference between an industrial and a laboratory production method?

texts:
I'm not sure if this is the correct SE in order to ask this, if that is true just said me that in comments and I will delete my question, there is no need of downvote or ban.

I was answering a question of World Building SE about how to make an atmosphere and I found that nitrous oxide can be used to make one. But then, I started reading how can I produce nitrous oxide (to post that information also) and I found with this on Wikipedia.

It talks about an industrial method and a laboratory method. Which is the difference?

I have the theory that a laboratory method can't be used at big scale. Is that true? But, How much is "big"? Maybe for a fabric it's too little the laboratory production (a few kilograms per minute per square meter of laboratoy???) but for me that is a lot, 1kg per minute is arround a cubic meter of air per minute (60 minutes per hour, 24 hours per day...)

P.S: Sorry for the bad tag. I don't have no idea of what to write.


texts: Conventional heating compared to microwave heating of chemical reactions

texts:
In order to try to increase yield of my cross-metathesis, it was suggested to carry out the reaction in the microwave (a lab microwave, not a kitchen microwave).

The rationale for this was that microwaves accelerate the reaction, but thinking on how a microwave actually works, it's basically just heating in the same way as I could achieve with a PEG bath.

When I searched the internet, there are lots of reviews and even books published about microwaves in organic synthesis, but I can't find a coherent argument for what microwaves are doing that makes reactions 'magically work'.

The radiation in theory simply causes the molecules to move creating heat, as far as I know, it isn't like photochemistry where something mechanistically different can occur.


texts: What is the relation between pressure and chemical potential?

texts:
I know that in a two-component gas-liquid system (for simplicity) the chemical potential $\mu_i$ ($i=1,2$) and total pressure $p$ can be defined by

$$\mu_i=\left(\frac{\partial U}{\partial N_i}\right)_{S,V,N_j}$$ and
$$p=-\left(\frac{\partial U}{\partial V}\right)_{S,N_1,N_2}.$$
where $U$ and $V$ are the internal energy and volume of the system, $N_i$ is the mole number of each component, and $p=p_1+p_2$ with $p_i$ being the partial pressure.
But how the partial pressure and chemical potential are related? Intuitively, I think $\mu_i\propto p_i$. Thank you!


texts:
I don't quite understand the categorization of middle distillate petroleum products.

Is heating oil the same thing as fuel oil which is the same thing as diesel, or not? Can someone explain the differences (if any) between the common middle distillates?


texts: Reasons for weakness of London dispersion force in graphite?

texts:
The layers of graphite are held together via London dispersion force. This force is weak. I know carbon having a smaller atomic radius and few electrons is one factor for this force's weakness.

But, the free electron is weakly bound with the adjacent three atoms. Does this constrains the free electron's ability to disperse, making the London force weaker?

P.S. This might be a duplicate question. Inform me if you find similar one(I haven't found any)


texts: How does the equipartition theorem apply to vibrational modes?

texts:
Specifically, how, based on the idea that energy will be shared equally among all degrees of freedom, does one come to the conclusion that each vibrational mode of a molecule will occupy $kT$ units of energy?

When learning statistical thermodynamics, classes often spend a lot of time talking about the Maxwell-Boltzmann distribution and even deriving that the expectation value for the energy of a monoatomic ideal gas is $\frac{3}{2}kT$ where $\frac12 kT$ comes from energy distributed to each cartesian coordinate plane.

Now, I find that I learn a whole lot from mathematical derivations of these types of things, and from simply working through the math and understanding its physical meaning.

So, I want to know, both on a conceptual level and through some sort of mathematical explanation, why does each vibrational mode of a molecule contribute $kT$ to the overall energy of the molecule when those modes are occupied?

My only guess is that one degree of freedom is kinetic energy (associated with the moving atoms) and the other is potential energy (analogy with a spring works here) but, if that is true, much clarity would be gained from a mathematical demonstration of this.


texts: Conc. vs Time Graph for Second Order Reaction

texts: From my understanding plotting the conc. over time for a 0-order reaction yield a negative linear slope. Plotting conc vs time for a first order reaction intuitively yields an exponential type slope. however, my teacher never covered the looks of a conc vs time graph for a second order reaction. What may this look like. In conjunction, what does it look like when we graph its rate over concentration?


texts: Regioselectivity in coupling reactions of α-naphthol

texts:
I have seen in the following reaction of azo coupling where coupling takes place at position 4 of $\alpha$-naphthol.

Now the electron density accumulation is similar at both position $4$ as well as $5$.

However, there are more resonance structures that can be drawn for position 5. It should also be sterically easier to attack position 5.
The only reason I can think of for position 4 over 5 is that $\ce{=OH+}$ has a -I effect, which may somewhat stabilize the carbanion. But at the same time due to large distance this may be very weak and may not efficiently stabilize the negative charge. Then why is it in the para and not the peri position that coupling preferentially occurs?


texts: XRD: Can stacking faults cause pseudo-centring?

texts:
Consider a cP lattice with a = 10 Å and an octahedron residing on each of the unit cell's vertices as shown below:

The maximum symmetry will be Pm-3 m.

Now, let's consider there are stacking defects along half of the diagonal of the unit cell's faces. Let's look at displacement by a translation of [0 0.5 0.5]:

If we look onto the bc plane, this will look like an A-centred cell:

If the stacking fault energy is low, random displacement along [0.5 0.5 0], [0.5 0 0.5], and [0 0.5 0.5] is to be expected. Will the situation described cause the powder X-ray diffraction pattern to resemble space group symmetry Fm-3 m, e.g. by integral extinctions of reflections where h + k, h + l or k + l is odd? From my perspective, the average structure the X-ray beam will 'see' is the following:


texts: What is the purpose of CaO in Oakwood reaction

texts:
In the Oakwood reaction, i.e.
$$\ce{RCOOH ->[NaOH + CaO] RH + Na2CO3},$$
is there any role or importance of $\ce{CaO}$, because it doesn't appear to be anywhere in the product.


texts: How to find the plane of symmetry in biphenyls and substituted cyclohexanes?

texts:
I was going through my text book, (Solomon&Frhyle)
I came across a couple of of examples which I didn't understand.

1.

How is the molecule symmetrical? Upon folding the molecule over its plane of symmetry  the cooh group will be placed over fluorine.

2.

Similarly in this in structures 3,4,5,6 a chlorine atom out of the plane and below the plane coincide.

3.
It's written that for biphenyls to be chiral a can be the same as a'. (Same for b and b')
           But
If a a' and b b' are the same them won't a plane of symmetry lie in the middle perpendicular to the plane of molecule.


texts: Is there a difference between Close Cubic Packing and Face Centered Packing?

texts: I see some places use close cubic packing (ccp) and face centered packing (fcp) interchangeably. Are they the same thing? Does one provide more information than the other?


texts: How to calculate the rotational constants for different states from a stick spectrum?

texts:
Given a stick spectrum for an unknown diatomic molecule, how do you determine the rotational constants $B_\nu$ for both the excited and ground states given that

$$E_{j}=B_{\nu}j(j+1)$$

\begin{array}{cc}
\text{Line position}\, \mathrm{(cm^{-1})} & \text{relative intensity} \\
\hline
27128.20 & 1.47 \\
27171.74 & 2.35 \\
27211.40 & 3.13 \\
27247.18 & 3.34 \\
27279.08 & 2.62 \\
27331.24 & 1.00 \\
27351.50 & 2.62 \\
27367.88 & 3.34 \\
27380.38 & 3.13 \\
27389.00 & 2.35 \\
\hline
\end{array}


texts: Interaction between soy milk and coffee producing bubbles

texts: I noticed when I poured my soy milk (which I shook as per the directions on the carton) into my coffee, a large number of very fine bubbles rose to the surface. What causes this? Is there a chemical reaction involved, or is it just a physical effect?


texts:
In an ester hydrolysis reaction using a dilute base what is the pH change before and after the reaction occurs. In this reaction I want to react methyl ethanoate with dilute sodium hydroxide. I want to know if the pH of the solution will change after I add the ester to the base.
If it doesn't, is there a reaction I can do with esters that will result in a pH change?


texts: How is the number of successful collisions in a time-step distributed?

texts:
In a spatial homogeneous reaction system with two different molecules, how is the number of collisions which will lead to a reaction in a fixed time-step distributed?

My guess: Poisson distribution, as collisions are Bernoulli-experiments, usually have a low probability for success and the number of trials are huge.


texts: Why the transition of diamond to graphite is so slow? Do I have to worry that one day I'll wake up and see graphite instead of my diamond?


texts: When diluting a mixture of two reactants with lets say a 100ml of H2O, how do you add this to the uncertainties of the concentrations of the reactants? Should the relative uncertainty of the added H2O be added to the relative uncertainty of the volume in both reactants?


texts: Volatility comparison for isomers of phthalic acid

texts:
All the atoms of these compounds are in a plane.

o-phthalic acid can show extensive intra-molecular hydrogen bonding as well as inter-molecular hydrogen bonding.

m-phthalic acid can show intra-molecular hydrogen bonding (though, in lesser extent) as well as inter-molecular hydrogen bonding.

p-phthalic acid can not show intra-molecular hydrogen bonding but can show extensive (more than ortho & meta isomers, due to no steric hindrance) inter-molecular hydrogen bonding.

Now, intra-molecular hydrogen bonding increases volatility whereas, inter-molecular hydrogen bonding decreases volatility (I am not comparing boiling points because these molecules decompose at temperature below their melting point).

What can we say about the order of volatility of these compounds?


texts: Is melting/boiling point of ionically bonded substance higher than of covalently bound?

texts:
Is the melting and boiling point of ionic bond usually higher than covalent bond?

I know that compounds with ionic bonds are usually solid at room temperature, so I want other answers than this. (and this question can also be about why compounds with ionic bonds are usually solid in room temperature.)


texts:
I am trying to find the standard entropy and enthalpy of methanol as functions of temperature, but they are not available on the NIST-JANAF tables: http://kinetics.nist.gov/janaf/

Does anyone know where I could possibly find the data?

Thank you in advance!


texts: Is it possible to make metal fulminates?

texts:
Is it possible to make fulminates such as: magnesium fulminate, copper fulminate, etc.
by the metal + $\ce{HNO3}$ + $\ce{EtOH}$ reaction?


texts: How do I make a ZMAT or XYZ file from scratch?

texts:
From a structure representation like the one below for Bacteriochlorophyll A, how do I make the ZMAT or XYZ file?
The closest similar question asked here was about converting a PDB entry into XYZ, but what I have here is not in PDB format, it is just the image of the molecular structure, reported in a paper.


texts: What's the bonding in the diborane(6)- hydrogen chloride dimer?

texts:
I was researching and Googling and researching again, about this very interesting molecule: Diborane.

Then I faced a very interesting structure, something that I have never seen before. Something that turns up lesser than 50 results in Google, most of which are behind paywalls, and thus leave me in pain of not understanding this species. I'm talking about diborane - hydrogen chloride.

Source

So, I'd like to understand this species better.

The bonding certainly doesn't seem ionic. What is the attraction force between $\ce{HCl}$ and $\ce{B2H6}$? There must be one or they wouldn't have written these two compounds together.

Edit: I'm specifically looking for the hydrogen chloride - diborane(6) dimer you can see in the image. And the Cl is pointing towards the H in diborane, so this isn't about dipole/induced dipole interactions. You can find more info about it in here. Interestingly, in calculating molar mass, both the $M$s of $\ce{HCl}$ and $\ce{B2H6}$ are taken into account.


texts:
I wonder if the  words on my T-shirt are removable? If yes, what kind of (chemical or physical) ways are there?

They look like paints on the cloth, as the letter "C" has become blurred in the way shown in the picture over the time when I was wearing it. But I admit that I don't know anything about how words are printed on clothes generally.


texts: How do P-H bonds in phosphorus acids impart reducing properties?

texts:
My textbook states:

The oxoacids of Phosphorous which contain $\ce{P-H}$ bond have strong reducing properties. Thus, hypophosphorous acid is a good reducing agent as it contains two $\ce{P-H}$ bonds and reduces, for example, $\ce{AgNO3}$ to metallic silver.
These $\ce{P-H}$ bonds do not ionize to give $\ce{H+}$ and do not play any role in basicity.

On the basis of what's given in the text; how do these $\ce{P-H}$ bonds account for the reducing properties of phosphorus acids?


texts: Why is the ester bond stable under Reformatsky reaction conditions?

texts:
The following reaction is a Reformatsky reaction.

Why is the ester bond not attacked in the last step? Couldn’t $\ce{OR3}$ be replaced by $\ce{OH}$ or $\ce{O(molecule)}$?


texts: Is there a way to get hot water without altering plumbing or electrical wiring too much?

texts:
Is there a way (other than collecting water and heating it on the stove ) to get hot/warm water from the tap without having to alter existing plumbing or electrical wiring ?

Perhaps use a chemical reaction to provide the heat to warm the water ?


texts: Why does branching leads to lower surface area?

texts: I know that lower surface area means lower interactive forces between molecules and hence lower boiling point. But the statement that branching leads to more compact molecules with lower surface area, I just cannot understand it. Can someone help me with a visual or any otehr kind of explanation?


texts: How did the atomic number and atomic mass of elements discovered?

texts: Elements are small for our naked eyes.so,how did the discovery of its atomic number and mass number took place?


texts:
Under what circumstances can the stereochemistry at nitrogen atom be faithfully retained and identified?

Because in most cases nitrogen atoms tend to undergo stereorandomisation by flipping due to its lone pair. I know of one example which has a three membered ring where nitrogen flips very slowly due to the high s character in the lone pair which requires significant activation energy to flip. But I wanted to know of the other cases where this is possible (probably in a stereo locked system inhibiting flipping).


texts: What is the justification behind the principle of corresponding states?

texts:
Two fluids with same reduced volume and temperature have the same reduced pressure.

Two fluids with same reduced pressure and temperature have the same compression factor.

What justifies these two statements and why exactly are both saying the same thing?


texts: What physical/chemical reasons could have caused Dorian Gray's picture to degrade?

texts: In the novel 'The Picture of Dorian Gray' by Oscar Wilde, Gray locks away a portrait of his in the attic for 18 years and over that time the picture degrades to an almost unrecognisable version of its former self. The novel explains this as the fulfilment of a wish by Gray to have the portrait age instead of himself but I have been wondering recently, are there be any natural reasons that could explain this transformation if a painting is locked away for a large period of time?


texts: Mechanism of a cyclization reaction - why does an enol ether form?

texts:
I was asked to predict compound A from the follwing organic scheme:

Looking at the formation of A, my prediction was that since TsOH is a strong acid, it would dehydrate the alcohols (like sulfuric acid does). However, looking at the next reaction of A, it seems to me that what happened was that the ketone formed its enol and did an aldol condensation with the aldehyde. But then, if this was the case, why do we have to add TsOH to get to A, then add $\ce{H3O+}$ to get to the final product when we could've gotten to the final product from the start with an aldol condensation?

I was told that the structure for A is actually:

I was not expecting this at all, and I'm not sure how this was formed. I can see that the enol ether in A is hydrolyzed in acid to get the final product, but the formation of A seems strange. What is the mechanism for the formation of A and why were my predictions wrong?


texts: Which chlorine species can act as an oxidizing agent but not as a reducing agent?

texts:
Which species can act as an oxidizing agent but not as a
  reducing agent?

  (A) $\ce{Cl2}$
  (B) $\ce{Cl-}$
  (C) $\ce{ClO2-}$
  (D) $\ce{ClO4-}$

I thought the answer was A because if $\ce{Cl}$ is reduced, it becomes very stable with a full octet and therefore cannot be the reducing agent; however, according to the 2007 Chemistry Olympiad answer key, the answer is D. Why is that?


texts: What happens when acetone reacts with hydrogen cyanide?

texts:
Which of the following is the major organic product when acetone is allowed to react with hydrogen cyanide in the presence of a catalytic amount of sodium cyanide?

The correct answer is (B).

However, I got this answer without using the catalytic sodium cyanide.  In my proposed mechanism, the dissociated proton from $\ce{HCN}$ activates the carbonyl, which facilitates the nucleophilic attack of $\ce{CN-}$.

What role does the $\ce{NaCN}$ play?


texts: I am refluxing $\ce{HBr}$ with 1,6-hexanediol for 16 hours at $80\ ^\circ\mathrm{C}$ in toluene. How can I be sure that more than $90\,\%$ of the product is brominated only at one terminal? If the amount of double brominated product is in more than $10\,\%$ of the total yield, then the product mixture will be useless for me.


texts: How can we determine if zinc hydride is a ionic compound? If it is a ionic compound then why doesn't it dissociate when put in water?


texts: Gibbs Free energy of a reversible reaction

texts: From what I understand, it sounds like the Gibbs Free Energy change of a reversible reaction at equilibrium is zero. However, since I know that Gibbs Free energy change depends on temperature, does this not imply that equilibrium can only ever be reached at one very specific temperature? This doesn't sound right, as I know that equilibrium can be established at lots of different reaction temperatures, although the position of equilibrium changes with temperature of course. I asked three chemistry teachers at my school, who all seem just as baffled as I am about this.


texts: Can soap make an liposome around virsuses?

texts:
I have read that soap does not kill bacteria and viruses, but it rather removes them, that is, it strips them off the skin sort of speak by forming micelles around them, which are then rinsed off.
But isn't it more logical that soap forms liposomes for viruses instead of micelles to remove them.


texts: How to calculate the number of moles present in a litre of saturated solution?

texts:
The solubility product of a salt having same molecular formula as $\ce{Ca_3(PO_4)_2}$ is $1.08\cdot10^{-28}$. Then find the number of moles of ions present in the saturated solution.

My approach: I found out the solubility of the salt i.e.: $x=10^{-6}M$

This means $x$ moles of salt are present in a litre. As 1 mole of the salt yields 5 moles of ions I thought the answer would be $5x$.

Help required.


texts: I want to make extracts of Black seeds. I do not posses any professional equipment, I just want to ask if it's possible to make extracts by soaking the seeds in ethanol for a long time and then evaporating it. Will the dissolved extracts evaporate with the solvent?


texts:
Why does silicon not react with dioxygen?

I'm doing an organic lab experiment. I'm heating up silicon, carbon, and sulfur individually then placing them in pure $\ce{O2}$. I don't really know about carbon chemistry but I thought the reaction might be related to the electronegativity of silicon being lower than that of sulfur/carbon causing the bond to be more polar or something?


texts: Rate determining step in oxidation of alcohols using chromium-related compounds

texts:
I wanted to ask a question about the kinetics of an oxidation reaction using chromium reagents.

I was given a lecture today on the mechanism of alcohol oxidations using Chromate (VI) reagents:

My previous knowledge of Rate-Determining steps (RDS) were that on an energy profile diagram, the step with the largest "activation energy" is the RDS as it takes the most energy to go over the steps, so relative the other steps are faster.

For today's lecture, the professor mentioned the following:

  If our $\ce{R}$ groups are bulky, which means that you have a bulky alcohol, the alcohol oxidises faster. This means that our Rate Determining step here is the second step and the first step is fast and reversible.

Unfortnuately, this point was not further explained.

I've tried to come up with a simple explanation to myself for two following points:

  The R groups being bulky means the second step is the RDS
  The rate determining step is the non-reversible step

but I can't seem to find any intuition for this. I only found the logic that there can be slow and fast steps in a reaction. My thought was that all reactions can be reversible, but maybe the second step has such a high activation energy and the reverse process involves so many unlikely species in the mechanism that it seems unlikely to happen.

Why does having a bulky R group prove the second step is the RDS?
Why is the non-reversible step the RDS, and not (say) the reversible step?


texts: Is there a general / simple formula for Slater's rules?

texts:
I just learned how Slater's rules work on Wikipedia. These rules really are very simple. But the presentation of the rules seemed not very efficient. I would think there would be someway to set up and equation of some sort such that all you have to do is plug in the relevant quantum numbers and the element number and use some sort of formula to just compute Slater's rules more easily.

Is there such an equation / formula? If so, I'd like to see it. It would be more convenient than memorizing the rules in verbal form.