texts: Why I can't use a single Slater determinant to describe the ground state of open-shell atoms and molecules?

texts:
If we have a closed-shell atom or molecule (in the Born-Oppenheimer aproximation), and adopt the central field aproximation, we can write the ground state wave function of the system using a Slater determinant, constructed using the spin-orbitals that are the solutions of the equations

$$(h_{i} + V_{i}) \varphi_{i} = \varepsilon_{i} \varphi_{i}$$

with the lowests energies, where $h_{i}$ is the sum of the kinect energy and interaction with the nucleo(s) of the electrons, and $V$ is the potential. However, I read that if the system is open-shell, in general we can't write the ground state wave function using only a single Slater determinant, we have to take linear combinations of Slater determinants. Can someone explaim why this happpen, and indicate a reference? I would like to understand it.


texts:
After doing a calculation on $K_{C}$, I was told that solids do not affect the calculation.

This is confusing me. Is there a specific reason why solids do not affect the equilibrium shift?

Thanks.


texts: What is the precise definition of Ramachandran angles?

texts:
The Wikipedia article Ramachandran plot is very schematic and doesn't even say when these angles are considered to be zero. It seems to assume that the peptide chain has no end, and always shows the next carbon atom. What happens when the amino acid is in the terminal position? It also asserts that the $\omega$ angle is always 180°, while in the practical cases this isn't exactly true.

The definitions seem to rely on the adjacent bonds. Two on one side, and one on the other side. They rely on the fact that two bonds on one side are in the same plane as the rotating bond. How are these angles defined when relevant bonds don't form a plane?

What is the precise definition of $\psi-\phi$ angles? Are there formulas for them that take atom positions as arguments with amino acids being in both terminal and non-terminal positions? Are they defined for amino acids in terminal positions?

Additionally, an article by Zhou et al. [1] also talks about the bond angle $\tau$. $\tau$ seems to be a logical addition because it corresponds to an additional degree of freedom, not covered by $\psi-\phi$ angles.

References

Zhou, A. Q.; O’Hern, C. S.; Regan, L. Revisiting the Ramachandran Plot from a New Angle. Protein Science 2011, 20 (7), 1166–1171. https://doi.org/10.1002/pro.644.


texts: Why bond energy of acetone is more though it is more polar than formaldehyde?

texts:
I was going through the general properties of carbonyl compounds and then found this (in the pic) data, where it says that dipole moment of acetone (if we assume $\ce{R = -CH3}$) is more than acetaldehyde which in turn is greater than that of formaldehyde.
But I think, as $\ce{-CH3}$ is a $+I$ effecting group, so it will satiate the residing positive pole on carbon slightly and hence will make the $\ce{C=O}$ bond less polar and hence the sequence should be reversed!

Please anyone make me correct where am I mistaking with the concept?

Picture source

EDIT :- I got my answer of the above confusion. Thanks to Physicsapproval.
But with that I came to face another confusion. In the next part of the text (see the paragraph just below the pic in the Picture source) I found that "the larger the dipole moment the greater the polar character of the carbonyl group". So that means, $\ce{C=O}$ bond in acetone is more polar and least in the case of formaldehyde! Now in the next part it is mentioned that the bond energies of $\ce{C=O}$ bond in the mentioned compounds are: $$ \ce{H2C=O} \, ; 170~\mathrm{kcal/mol}$$ $$\ce{RHC=O} ~ ; 175~\mathrm{kcal/mol}$$ $$\ce{R2C=O}~; 180~\mathrm{kcal/mol}$$
Now I know that the more polar the bond is, the less is its bond energy. So, in this case why the trend is reversed, i.e., $\ce{C=O}$ bond of acetone being more polar has the highest bond energy compared to other two?


texts: Why do lithium enolates add to an electrophile in direct addition manner, while the sodium and potassium enolates tend to add in conjugated additions? The sodium and potassium enolates are well dissociated, making oxygen a hard base (which is why these enolates participate easily in O-acylations), but still, the alpha carbon atom is made softer, to react well in conjugated additions. This seems to me like a contradiction.


texts: Fuel Cell Chart - Anode, Cathode, Electrolyte

texts: Can someone please check my table to make sure I have the correct information. I am especially unsure of the parts highlighted in yellow:


texts: Are there ion combinations which can't be separated using the ion exchange resin method?

texts: I am currently investigating the uses of ion exchange resins (both cation and anion resins). I have not come across any ion combinations that cannot be separated using this method, are there any exceptions or does this method work for all ion combinations? If there are ions that can not be separated using the resin, what methods would work to separate them?


texts: Methods and observations that help you achieve complete decomposition of a compound in decomposition analysis

texts:
Different chemicals decompose in different ways to give different observations, but they usually involve heating the compound to high temperatures.

My question is that what are your lab techniques that help you ensure the compound you're analyzing is fully decomposed? what do you usually look for that signifies that your compound has decomposed fully?


texts: Can aluminum and hydrochloric acid be used to generate hydrogen gas?

texts:
I am looking to produce hydrogen gas in a small amount with supplies I currently have. Most of the methods I have seen involve reacting zinc or magnesium with $\ce{HCl}$ to obtain the gas, but I do not have zinc or magnesium at the moment.

Is there any reason why aluminum cannot be used just as effectively as zinc? According to the reactivity series, aluminum should be even more reactive than zinc.


texts: Expression for Gibb's free energy change for a cell reaction

texts:
According to Chemistry Libretexts, the Gibbs free energy change of a cell reaction is related to the cell voltage as
$$ \Delta G = -nFE,$$
where $n$ is the number of moles of electrons passed and $F$ is the charge on a mole of electrons.
But $E$ decreases in value through the course of the cell reaction, so  shouldn't
$$\Delta G = -\int_{q_\mathrm{i}}^{q_\mathrm{f}} E\,\mathrm dq,$$
where $q_\mathrm{f} - q_\mathrm{i} = nF?$


texts: What happens to the NADH produced by lactate oxidation?

texts:
I first want to note that I'm a layman attempting to gain an understanding of metabolism by reading resources on the internet with only a little understanding of chemistry. I've hit a snag:

Oxidation of lactate into pyruvate reduces NAD+ to NADH. Subsequent glyconeogenesis can then turn two pyruvate into a new glucose molecule at the cost of 6 ATP. However, the NADH is presumably used to generate ATP via oxidative phosphorylation producing ~2.5ATP, making an overall reaction of 2 lactate -> 1 glucose cost only ~1ATP. This clashes with other things I have read - that glyconeogenesis costs 3x the energy glycolysis produces - as this would seem to discount the reduction of NAD+ to NADH in glycolysis. I feel I am clearly misunderstanding something, but I'm not sure where.


texts: In the elementary steps of a reaction, why do we assume that the coefficients of a reactant correspond to its order?

texts:
Recently, I was taught that the coefficients of the reactants in an elementary step of a reaction indicates that reactant's order. Why is this the case? I thought that the order of a reactant was not related to its coefficient.

For example, in the following termolecular reaction mechanism

$$\ce{A + 2B -> C + 2D}$$

the rate law is $k[\ce{A}][\ce{B}]^2$. Why is this the case?

EDIT: Also, for equilibrium reactions, do we always assume the coefficients of the reactants to provide the order for those reactants? What about for equilibrium reactions involving multiple steps?


texts: HPLC Columns For Compounds Not Soluble In Non- Or Low Polar Solvents

texts: Can someone recommend HPLC columns for compounds which are not soluble in no- or low polar solvents (hexane, isopropanol, toluene, and dichloromethane)?


texts:
Most types of desiccation packages use silica gel, but are there any that use calcium oxide instead? Here's my reasoning:

Calcium oxide absorbs water, forming calcium hydroxide.
Adding a (used) package to water produces a slight amount of heat (I may be imagining this).
The solution stays cloudy even after sitting for a while.
The solution almost immediately turns clear upon addition of vinegar.

At this point, I'm pretty sure it is calcium oxide and hydroxide in this package, but I just wanted to make sure first. For point 2, I should note that it is very humid in the place that I live, so it would make sense that most of the calcium oxide is converted into calcium hydroxide, and therefore not much heat is produced.


texts: What is the difference between ΔfH and H-H° in NIST–JANAF tables?

texts: Can someone explain the difference between $Δ_\mathrm{f}H$ and $H-H^\circ$ in NIST–JANAF tables?


texts: Correlation Diagram Doesn't Match Selection Rules?

texts:
From Miessler's Inorganic Chemistry, 5th edition, there is this correlation diagram for $d^{2}$ in a octahedral field.

On the left hand side, if it's not clear, it goes (from lowest to highest):

$^{3}F, ^{1}D, ^{3}P, ^{1}G, ^{1}S$.

But by Hund's rules mentioned even in the same chapter, one would expect the $^{3}P$ to show up right after the $^{3}F$ because of their higher spin multiplicities. And even after that, G should come before D. (the ordering for that being s,p,d,f,g in reverse for same spin multiplicities). I don't know of any reason for why the $^1D$ term is just above the $^3F$ term in this graph though. Is this an error or does anyone have an explanation?


texts: Grignard with nitrile: why is the imine protonated twice?

texts: Steps 2 and 3 in the picture show the imine being protonated twice to form the iminium ion in step 4. I'm a little confused as to why the second protonation occurs; does the imine after step 2 still have basic tendencies?


texts: Calculation correct binding energy for a system?

texts:
I am doing DFT calculations (VASP) to calculate correct binding energy for an amorphous silica surface and silver adatoms. From MD simulation, we found that a binding energy of 0.2 eV gives results which can be matched to experimental ones.

Since this is an amorphous surface, how do I go along to measure the correct binding energy. I have tried 18 runs where I have relaxed the adatom at different positions and at different heights but how many runs to do this as each result has a different value?


texts: Is consumption of chlorine, like fluorine, harmful to bones?

texts:
Is consumption of chlorine harmful to bones ?

I know fluorine consumed with water can cause fluorosis to bones and joints.

Can chlorine,  a similar halogen like fluorine, also cause damage to bones and bone joints?


texts: I am trying to calculate the total energies for a particular organic molecule that undergoes radical decomposition. I was able to calculate the neutral molecule with the exact results of a paper I found. My trouble is obtaining the correctly calculated energies for the radical molecules. I am new to computational chemistry and am looking for a bit of guidance on this.


texts:
While comparing the strengths of o-nitrophenol and p-nitrophenol, p-nitrophenol is found to be more acidic. The reason I studied for this is $\ce{H}$-bonding in o-nitrophenol which makes the acid more stable, making it a weak acid.

But between o-methoxyphenol and p-methoxyphenol, o-methoxyphenol is more acidic because of more -I effect at o-position. Doesn't $\ce{H}$-bonding happen here?

Can someone please clarify the exact reason for opposite orders?


texts: Is honey really a supersaturated solution? Does heating to un-crystalize redissolve it or melt it?

texts:
In the SciShow video Honey: Bacteria's Worst Enemy after about 00:30 the narrator says:

Honey is only about 17% water. Most, but not all of what remains is sugar. The two main types of sugar in honey are glucose and fructose. Like all sugars, glucose and fructose are sticky — they attract water.
Honey is technically a supersaturated solution, meaning it contains more sugar than would normally dissolve at that temperature. That’s why it eventually gets all crystally in the pantry — over time, sugar comes out of the solution.

In my experience when old honey "gets all crystally in the pantry" I've placed the jar in a hot water bath, and eventually the honey's viscous liquidy consistency is restored.
When I do this, am I redissolving the sugar, or melting it?
I'm asking because even hot, with only 17% water it's hard to imagine it can become an unsaturated solution.


texts:
What the possible rate laws are for the decomposition of nitramide by the following process:

  $$
\begin{align}
\ce{O2NNH2(aq) &<=>[$k_1$][$k_{-1}$] O2NNH-(aq) + H+(aq)} &\quad &\text{(fast equilibrium)} \tag{1}\\
\ce{O2NNH-(aq) &<=>[$k_2$] N2O(g) + OH-(aq)} &\quad &\text{(slow)} \tag{2}\\
\ce{H+(aq) + OH-(aq)&<=>[$k_3$] H2O(l)} &\quad &\text{(fast)} \tag{3}\\
\end{align}
$$

  (A) $\text{rate} = k[\ce{O2NNH-}]$
  (B) $\text{rate} = k[\ce{O2NNH2}]/[\ce{H+}]$
  (C) $\text{rate} = k[\ce{O2NNH2}][\ce{H+}]$
  (D) Both A and B

I selected A, but the answer is actually D. The answer key gives the following information:

  At the first glance, you may think that Option A is the best answer due to the information available in the question stem in which details the way a rate of reaction is written. However, option B also deserves some attention. It is important to understand that $K_\mathrm{eq}$ is the equilibrium constant for step 1, as this is the fast equilibrium step

  $$K_\mathrm{eq} = \frac{[\ce{O2NNH-}][\ce{H+}]}{[\ce{O2NNH2}]}$$

  Rearranging for $[\ce{O2NNH-}]$, and substituting it into the rate law gives an equally valid expression which leads to Option B also being correct. The best answer is therefore Option D.

I am confused about how this can be so.

Firstly, why can we just sub the equilibrium equation in like this, and what happens to the Ksp term, it seems to just disappear.

Secondly, doesn't this mean that the overall order of the reaction is inconsistent between option A and B (i.e. in A the overall order is 1, but in B it is 1-1=0).

Thirdly, conceptually I am confused about why the concentration of the product should change the rate of the forward reaction, this does not really make sense to me, why should the reaction proceed less quickly just because there is more product around? Further, if it is the case that the product changes the speed of the forward reaction, then why don't all rate equations feature the product?

I am left very confused, perhaps someone can help me out?


texts:
I am confused about the uncertainty equations calculations.

If I have the equation X1 * Y1 = X2 * Y2 and I want to find the uncertainty of X1 , I convert the equation to X1 = (X2 * Y2)/(Y1) .  Now, I would know how to calculate the uncertainty if it was a straight division or multiplication uncertainty but this equation is both.  How do I go about calculating the uncertainty if the equation contains both multiplication and division? Do I just do the multiplication uncertainty first and then the division uncertainty?

Thanks any advice is appreciated.


texts:
We know that for strong acids with a $1:1$ mole ratio between all particles involved are suitable for use with the aforementioned formula for titration problems. I want to know the limits on this formula, that is:

Consider if we had $$\ce{H2SO4(aq) + 2KOH(aq) -> 2H2O(l) + K2SO4(aq)}$$

Since the moles of $\ce{H+}$ = moles of $\ce{~^{-}OH}$ in order to neutralize, how do we apply $M_aV_a=M_bV_b$ to this situation, if at all possible?

Secondly, does this formula work if we had weak acids? I would think not, because with weak acids we don't have the benefit of complete dissociation and thus not a $1:1 = \text{acid}:\ce{H+}$ ion ratio nor a $1:1 = \text{base}:\ce{~^{-}OH}$ ratio.


texts: I am learning Chemistry now, and I want to take some notes that involve huge amount of organic chemistry on Mac. How can I do that? Pages does not seem support scientific use.


texts: Determining the rate of stratospheric ozone destruction

texts:
I am a sophomore. A friend and I ran across a kinetic chemistry exercise. We solved it in a slightly different way and we can't come to an agreement on who is right. We would appreciate some help:

  Destruction of stratospheric ozone as determined by using the steady-state approximation.

  The balance of ozone in the stratosphere is of critical concern
  because this molecule absorbs ultraviolet light that would be harmful
  to life at Earth's surface. The principal production mechanism for
  ozone is recombination of $\ce O$ atoms with $\ce{O_2}$. The principal
  destruction mechanism is that given below. There is increasing concern
  over alternative destruction mechanisms involving molecules introduced
  into the stratosphere by human activity.

  Determine the destruction rate of ozone in the following mechanism.
  $$\begin{align}\ce{O3 + M &<=>[k_1][k_{-1}] O2 + O  + M}\\
\\
\ce{O3 + O &->[k_2] 2 O2}\end{align}$$

Our answers:

We agree on the beginning, so we have :

$$\begin{align}
-\frac{\mathrm d[\ce{O_3}]}{\mathrm dt} &= k_1[\ce{O_3}][\ce{M}] - k_{-1}[\ce{O_2}][\ce O][\ce M] + k_2[\ce{O_3}][\ce O]\\
-\frac{\mathrm d[\ce{M}]}{\mathrm dt} &= k_1[\ce{O_3}][\ce M] - k_{-1}[\ce{O_2}][\ce O][\ce M]
\\
-\frac{\mathrm d[\ce O]}{\mathrm dt} &= -k_1[\ce{O_3}][\ce M] + k_{-1}[\ce{O_2}][\ce O][\ce M] +k_2[\ce{O_3}][\ce O]
\end{align}$$

Now here comes the disagreement, we need to use the steady-state approximation to say that one of the above speed is null:

My friend argues that $-\frac{\mathrm d[\ce O]}{\mathrm dt}$ should be approximated to null because it is a transient compound.

Even if in most other exercise, it would be correct, I disagree with him because in the proposed mechanism, $\ce{O_3}$ and $\ce O$ play a symmetrical part. So if we approximate $-\frac{\mathrm d[\ce O]}{\mathrm dt}$ to $0$ we should also approximate $-\frac{\mathrm d[\ce{O_3}]}{\mathrm dt}$ to $0$. Since we want to calculate this specific value, we don't want to approximate it.
In my demonstration, I approximate $-\frac{\mathrm d[\ce{M}]}{\mathrm dt}$ to $0$, arguing that the compound $\ce M$ is on both side of the equilibrium equation and therefore it's concentration will remain constant.

We both manage to find a result:
My friend’s calculation:

$$
- \frac{\mathrm d[\ce O]}{\mathrm dt} = -k_1[\ce{O_3}][\ce M] + k_{-1}[\ce{O_2}][\ce O][\ce M] + k_2[\ce{O_3}][\ce O] = 0
$$
$$
k_1[\ce{O_3}][\ce M] - k_{-1}[\ce{O_2}][\ce O][\ce M] = k_2[\ce{O_3}][\ce O]
$$
We substitute the left member in the speed of ozone:
$$
-\frac{\mathrm d[\ce{O_3}]}{\mathrm dt} = 2\times k_2[\ce{O_3}][\ce O]
$$
Because $[\ce O]$ is transient, it is difficult to mesure experimentally, so we expresse it in function of $[\ce{O_3}], [\ce{O_2}]$ and $[\ce M]$ :
$$
k_1[\ce{O_3}][\ce M] = [\ce O] \times ( k_2[\ce{O_3}] + k_{-1}[\ce{O_2}][\ce M] )
$$
$$
[\ce O] = \frac{k_1[\ce{O_3}][\ce M]}{k_2[\ce{O_3}] + k_{-1}[\ce{O_2}][\ce M]}
$$
And finally we have my friend’s result:
$$
-\frac{\mathrm d[\ce{O_3}]}{\mathrm dt} = \frac{2k_1k_2[\ce{O_3}]^2[\ce M]}{k_2[\ce{O_3}] + k_{-1}[\ce{O_2}][\ce M]}
$$

Now my calculations:
$$
-\frac{\mathrm d[\ce M]}{\mathrm dt} = k_1[\ce{O_3}][\ce M] - k_{-1}[\ce{O_2}][\ce O][\ce M] = 0
$$
Which allow us to simplify the destruction rate of ozone:
$$
-\frac{\mathrm d[\ce{O_3}]}{\mathrm dt} = k_2[\ce{O_3}][\ce O]
$$
We already disagree by a factor 2 on the rate. But if we replace $[\ce O]$ like before, we obtain a much simpler result:
$$\begin{align}
k_1[\ce{O_3}][\ce M] &= k_{-1}[\ce{O_2}][\ce{O}][\ce M]
\\
[\ce{O}] &= \frac{k_1[\ce{O_3}][\ce M]}{k_{-1}[\ce{O_2}][\ce M]}
\\
[\ce O] &= \frac{k_1[\ce{O_3}]}{k_{-1}[\ce{O_2}]}
\end{align}$$
Finally I have:
$$
-\frac{\mathrm d[\ce{O_3}]}{\mathrm dt} = \frac{k_1k_2[\ce{O_3}]^2}{k_{-1}[\ce{O_2}]}
$$

Which one of us is wrong and why?


texts:
Google search shows the density of saturated $\ce{KBr}$ is $\mathrm{3.119\ g/ml}$ at $\mathrm{25\ ^\circ C}$.

We have a solution of saturated $\ce{KBr}$ and density is about $\mathrm{1.5\ g/ml}$ when weighed on a calibrated analytical balance.
How do we account for this discrepancy?


texts:
Possible Duplicate:
  Why is methane's molecular formula conventionally “CH4”, while water is “H20” (among others)?

If I have a formula containing 4 hydrogen atoms and 1 carbon

Should it be written $\small\ce{CH4}$ or $\small\ce{H4C}$?

In general, how do I know the order to put elements in, in a chemical formula?


texts: Why is the oxidation of sulfur dioxide not termed as heat of formation of sulfur trioxide?

texts:
According to me, the following reaction's heat should be termed as heat of formation of sulfur trioxide:

$$\ce{SO2 + 1/2 O2 -> SO3}$$

However, in my textbook, they have that given it is not the formation reaction. Why is it so? And which is the formation reaction then?


texts: Why don’t all objects melt and liquefy when heated sufficiently?

texts: Certain objects such as metals, glass, plastic, sugar etc. melt when heated to a certain temperature but other materials such as a piece of wood, paper, a piece of rock etc. do not. Why is that?


texts: Ionic compounds dissolve in nonpolar compounds?

texts:
I think ionic compounds dissolve in just about any compound including nonpolar. My reasoning is this:

Neutral electric charge attracts both positive and negative (This I know from doing things with static electricity and putting it on a neutral surface).

Ionic compounds like strong acids and bases disassociate into individual ions, or if it is not dissolved but melted ionic dimers (like an individual Na+Cl- dimer for example).

Do ionic compounds such as NaCl dissolve in just about every solvent from polar to nonpolar to liquid ionic?


texts: Why does MgCl2 lower the freezing temperature, and how does it do so?

texts: I am working on a project in my chemistry class, and even though we've already finished the lab, I'm still confused as to why and how $\ce{MgCl2}$ melts ice/ lowers the freezing temperature of water. Can anybody tell me why this happens?


texts:
Please correct me if I’m wrong, but I’ve read that the reason why we use significant figures is to avoid making the result of a calculation more accurate than the starting values prior to the calculation. For example, if we were seeking the ratio of two weights, lets call them A and B, using a cheap scale and an expensive scale we could get the following varied results:

Cheap Scale
$$A = 34 \space oz$$
$$B = 23 \space oz$$

Expensive Scale
$$A =  34.0000 \space oz$$
$$B = 23.0000 \space oz$$

Computing the ratio $\frac{A}{B}$ using a calculator we get the following value:
$$\frac{34}{23} = 1.47826$$
Now this is a correct ratio depending on the scale used (ie the cheap scale could not have produced such an accurate measurement given the starting values)
This leads to the following question:

  Why are the zeros behind a decimal point ignored if they are just place holders?

For example, the value 0.000023 oz only has two significant figures, but isn’t that value something only a very fine tuned scale could measure (keeping in line with the previous weight example). So why are these zeros ignored?


texts: CuSO4 in SO2/SO3 gas sampling in Sulphuric Acid Production

texts:
What role does $\ce{CuSO4}$ has in the gas sampling of an $\ce{SO2/SO3}$ gas mix in a catalytic converter for sulphuric acid production?

To give you a little context: We take gas samples from the beds of the catalytic converter to determine the efficiency of the catalyst. We use "cartridges" that we make with glass tubes filled with $\ce{CuSO4}$. The $\ce{CuSO4}$ (lab grade) comes in crystal version as a pentahydrate. We heat it for around $\pu{30 minutes}$ at $\pu{105 ^\circ C}$ and then we use it to make the cartridges. The cartridges are placed between the sampling point and the sampling bag (made of Teflon). This is a process that has been made since many  years but nobody here is able to tell me why. The answer they give me is that the cartridges are used to "remove" the $\ce{SO3}$ from the sample but I can't see how that could happen. My theory is that because anhydrous $\ce{CuSO4}$ is hygroscopic (I've read it's been used as a desiccant) it may be used to avoid the formation of $\ce{H2SO4}$ that could damage the gas analyzer (a SICK S700). I've really googled it but can´t find the answer. Hope someone could enlighten me in the subject.


texts:
I find it difficult to understand why the Atomic radius of $\ce{Ar}$ is lower than the ionic radius of $\ce{Mg^2+}$ and $\ce{F-}$, and higher than $\ce{Al^3+}$. According to the tables I've seen:

$$\ce{F- = 119 pm > Mg^2+ = 86 pm > Ar = 71 pm > Al^3+ = 68 pm}$$

Shouldn't Ar be larger than all three since it has a third electron shell, and they only have two? From what I was taught, the number of electron shells is more important then the number of protons in the atom. What differs so much between $\ce{Mg^2+}$ and $\ce{Al^3+}$ that $\ce{Ar}$ atomic radius is right between them?

Is there a way to predict this order, just by looking at the periodic table?


texts: Kinetic Energy Evaluation Integral Evaluation Program

texts:
I'm reading Ostlund's Modern Quantum Chemistry. In Appendix A, the kinetic energy integral is evaluated using the Gaussian Basis functions to be

  $$
\left(A\left| -\frac{1}{2}\nabla^2 \right| B\right) =
\alpha\beta/(\alpha + \beta)[3 - 2\alpha\beta/(\alpha + \beta) |\mathbf{R}_A - \mathbf{R}_B|^2][\pi/(\alpha + \beta)]^{3/2} \\
\times \exp [-\alpha\beta/(\alpha + \beta)|\mathbf{R}_A - \mathbf{R}_B|^2]
\tag{A.11}\label{kin-en.int}
$$

So, in the integral evaluation the Gaussian functions themselves are not used, but in the computer program  he is evaluating the integral using

T11=T11+T(A1(I),A1(J),0.0D0)*D1(I)*D1(J)

The function T() is calculating the equation above \eqref{kin-en.int}.

I can't understand why he is multiplying by D1 and D2 which are the Gaussian functions themselves.
$$g_\mathrm{1s}(\alpha) = (2\alpha/\pi)^{3/4}\mathrm{e}^{-\alpha\mathbf{r}^2}$$


texts: Calculation of equilibrium constant for dissolution of iron(II) fluoride in acid

texts:
I am reviewing for the AP Chemistry test, and the question is this

$$
\ce{FeF2(s)  <=> Fe^2+(aq) + 2F^- (aq) } \quad  K_1 = 2\times 10^{-6}
$$

$$
\ce{F- (aq) + H+ (aq) <=> HF(aq)} \quad K_2 = 1 \times 10^3
$$
$$
 \ce{FeF2 (s) + 2 H+ <=> Fe^2+ (aq) + 2 HF (aq)} \quad K_3 = ?
$$

I solved for $K_3$ by multiplying $K_1$ and $K_2$, and then dividing by 2. I got $K_3 = 1 \times 10^{-3}$.  I would think that this would be not thermodynamically favorable since $K_3 < 1$, but the answer was the opposite: $K_3$ is thermodynamically favorable, because $K_3 > 1$.  Why is this the answer?


texts: Gold nanoparticles in a water/oil environment

texts:
I am currently investigating the assembly of gold nanoparticles in a mixture of water and oil. The thing is the following: If we have gold nanoparticles (35nm diameter) dispersed in water and we put some oil on it. After that we shake it, then the gold will be kept between the layer between water and oil and now I was wondering why this happens.

So why is it not possible that the gold nanoparticles stay solely in the water or go over in the oil completely? Or it could be possible that the gold particles agglomerate, why does this not happen? Or maybe it does happen and I do not know this.

Does somebody have some background information on this topic?


texts: Is there a way to liquefy a super absorbent polymer without using salt?

texts: I understand that once a SAP absorbs a liquid it becomes a type of gel and that this gel can be liquefied by applying salt, are there other methods to liquefy this gel without using salt?


texts: Why is enthalpy and not heat released by system used while calculating entropy of surroundings?

texts:
While finding the sum of change in entropy of the universe and thus defining Gibbs free energy, why is the change in entropy of surrounding the negative of enthalpy of the system divided by the temperature?
I mean why are we considering the pressure to be constant ( thus considering enthalpy) in all systems while calculating Gibbs free energy ? Shouldn’t a more general form of entropy of surroundings be negative of heat released by system divided by the temperature?
I was thinking that maybe it is because all closed and open systems are constant pressure systems and change in entropy of surroundings is zero for isolated system but I don’t know, I am just guessing.
So, could someone please help me in understanding why enthalpy and not just heat in general is considered for any system while calculating Gibbs free energy?
Any help will be greatly appreciated!


texts: How much yeast is necessary to produce the same amount of carbon dioxide that I exhale?

texts:
I think I might have bed bugs. I read that bed bugs are attracted to $\ce{CO2}$ and heat, I also know that yeast produces $\ce{CO2}$ as a waste product. Knowing that, I did some research and found this article on intructables.com which creates a "trap".

My gut instinct is that a 1/2 teaspoon of yeast will not produce anything close to the amount that a person exhales, but I don't know My question is, how much yeast would I need to create the same amount of $\ce{CO2}$ that I exhale on average in a day, per day?

What I know so far:

We exhale $\pu{0.02 m^3/h}$ while resting or low activity (Oscar W. Richards and Florence W. Haynes, Plant Physiol. 1932, 7 (1), 139–144.)
This graph (Figure 3 and 4 of above citation) shows the average $\ce{CO2}$ production per minute by yeast, but I don't know enough about chemistry to know what the units are or how to convert them to something useful (in my case, "useful" would be I need to buy x grams of yeast).

The trap definitely works as I've caught 2 in 24 hours. However, catching them isn't my interest (I wouldn't be able to get rid of them all with a trap).

However, please don't be distracted by the bugs. The bugs themselves aren't the problem of this question; I'm trying to determine the quantities. I'm fairly naive when it comes to chemistry, but in my mind this shouldn't be a hard problem to solve. Unfortunately, I don't know how do the conversions or read the paper's to arrive at the answer but I'm still actively trying to figure this out.


texts: Converting sulfate ion to sulfur trioxide?

texts:
I have a solution of only sulfate ions (no other positive ions belonging to the sulfate ions, because the positive ions are attached to the intermediate in a catalytic reaction).

I want to convert the sulfate ions to sulfur trioxide by using $\ce{V^5+}$ ions...

So what if $\ce{V^5+}$ ions could be present and could gain 2 electrons from one sulfate ion to produce $\ce{V^3+}$ and $\ce{SO3}$ (however I'm not even sure if $\ce{SO3}$ would be formed)? Here the two negatively charged oxygen atoms will each lose 1 electron to the $\ce{V^5+}$ ion, so the oxidation state of the central sulfur atom is still $+6$, but the oxidation states of the 2 oxygen atoms are $0$.

Could this be possible? And if so, would it be $\ce{SO3}$ that is formed, or other sulfur oxides?


texts: Nucleophilic acyl substitution leaving group

texts:
From Wade's "Organic Chemistry" [1, p. 1001]:

  MECHANISM 21-3 Conversion of an Acid Chloride to an Ester

What I don't understand is the elimination of $\ce{Cl}$, even though a much better leaving group with a positive charge on it is present (which results in the backwards reaction).

Why doesn't the alcohol or acid chloride deprotonate the tetrahedral intermediate before step 2 and after step 2 $\ce{Cl-}$ can attack the protonated alcohol/acid chloride to turn into $\ce{HCl}$?

Reference

Wade, L. G. Organic Chemistry; Pearson Education, 2012,. ISBN 978-0-321-81139-4.


texts:
I completed a practice (not for marks) assignment for an organic chemistry course, and one of the questions asked for the pKa of methylamine.

I looked on PubChem, and it gave a result of $10.6$. Marking myself, I found that the answer key states the $\mathrm{p}K_\mathrm{a}$ of methylamine is $33$! Especially on a log scale, that is not a trivial difference.

I talked to my professor about it; he was confident the true $\mathrm{p}K_\mathrm{a}$ is in the low thirties and stated that I need to be skeptical of material online. His point in part was that there was no way methylamine was more acidic than water.

I am not personally convinced on either number yet.

What is the $\mathrm{p}K_\mathrm{a}$ of methylamine, and what evidence supports that number?


texts:
Consider the following reaction:

  $$\ce{2 H2 (g) + 2 NO (g) -> N2 (g) + 2 H2O (g)}$$

  The elementary steps of this reaction are:

  $$
\begin{align}
&1^\text{st}~\text{step:} &\ce{H2 (g) + 2 NO (g) &-> N2O (g) + H2O (g)} &&\text{(slow)} \\
&2^\text{nd}~\text{step:} &\ce{N2O (g) + H2 (g) &-> N2 (g) + H2O (g)} &&\text{(fast)} \\
\end{align}
$$

  The reaction is exothermic overall.

  (a) What is the rate law for this reaction? Justify your answer.

  $$\text{rate} = k[\ce{NO}]^2[\ce{H2}]$$

  The 1st step of the reaction is the rate limiting step.

How did they know the order of the reaction with respect to $\ce{NO}$ was $2$, and $1$ for $\ce{H2}$? With other questions the orders are something they state in the question and are unrelated to the coefficients.


texts:
A qualitative test for the iodide ion involves reacting the salt solution with copper sulphate. This is said to yield the triiodide ion and the white precipitate of $\ce{Cu2I2}$.
I haven't been able to find a proper name for, or any data on this copper iodide... dimer? Wikipedia mentions that it exists in several crystalline forms, so is it something that arises in that context? Or is it just an obscure dimer of copper iodide?


texts: Why are so many wave functions associated with hydrogen?

texts:
According to Wikipedia, there's an infinite set of possible wavefunctions (orbitals) for the hydrogen atom:
$$\psi_{n\ell m}(r,\theta,\phi) = \sqrt {{\left (  \frac{2}{n a_0} \right )}^3\frac{(n-\ell-1)!}{2n[(n+\ell)!]} } e^{- r/na_0} \left(\frac{2r}{na_0}\right)^{\ell} L_{n-\ell-1}^{2\ell+1}\left(\frac{2r}{na_0}\right) \cdot Y_{\ell}^{m}(\theta, \phi )$$

Would an unperturbed electron ever go outside the lowest orbital?
At some point the perturbation (excitation) energy would exceed the ionization energy, so above that certain energy, no orbitals could ever be populated, so what's the point of having all these solutions?

"Probability densities for the first few hydrogen atom orbitals" (source)


texts: The mechanism of the reaction between 2-chloroethanol and hydroxyl ions in aqueous solution

texts:
The mechanism of the reaction between 2-chloroethanol ($\ce{CH2ClCH2OH}$) and hydroxyl ions in aqueous solution forming ethylene oxide ($\ce{CH2CH2)O}$ probably contemplates two steps:

$\ce{CH2ClCH2OH + OH- <=> CH2ClCH2O- + H2O}$
$\ce{CH2ClCH2O- <=> (CH2CH2)O + H2O + Cl-}$

Is the mechanism valid for the following experimental reaction rate?

$\frac{-d[\ce{CH2ClCH2OH}]}{dt} = K_{exp}[\ce{CH2ClCH2OH}][\ce{OH-}]$


texts: Looking for a toxic substance that cannot exist at room temperature

texts:
I am writing a short story, and am trying to find a gas with the following properties:

It must have a very distinctive odor
It must be impossible for it to exist at room temperature under normal conditions
It must be toxic to humans

How large a pool of possible substances are there that meet these requirements? Is there a particular family or class of gases where I should be focusing my attention?

Some additional clarification (apologies for not including this when I first wrote the question):

The scenario I am writing is Cthulhu-based. The idea is that this substance is discovered where it shouldn't be able to exist. This is where the second criteria comes from. They will collect a sample of this stuff, analyse it and realise that its mere existence is impossible in the circumstances they found it. A completely hypothetical example might be a substance that spontaneously combusts in earth's atmosphere, or that immediately reacts in some other way with a gas present in air. This would mean that it cannot exist where the protagonists discover it, yet it does.

The toxicity is just intended to add some jeopardy to the situation


texts: Why is sulphuric acid added in the ripper titration?

texts:
Ripper titration can be used to determine free $\ce{SO2}$ in wine by titration with iodine.

The method requires sulphuric acid to be added to wine before titration. Why is this the case?


texts: Why does activation energy depend on temperature?

texts:
To me it makes sense that the activation energy $E_\mathrm a$, as given by the Arrhenius equation, doesn't depend on the temperature as the needed energy (potential energy) to start a reaction has nothing to do with the temperature (kinetic energy) of the molecules. And a higher temperature simply means that more molecules have sufficient energy to proceed in the reaction $E\gt E_\mathrm a$.
So I don't understand why activation energy would depend on temperature, but this equation shows that it does $E_\mathrm a=\Delta H^{\ddagger}+RT$.
Can someone explain why?


texts: Transesterification of propylene carbonate and methanol

texts:
I'm going to try out the transesterification of propylene carbonate and methanol. I know that the mechanism is as follows :

-What are the products yielded after the reaction?

-And which catalyst should I use? (reaction is happening at normal air pressure and at room temperature)


texts: Why the boiling point decreases with increase in branching in alkyl groups?

texts:
I found out the answer is that

with increase in branching, the molecules attain a spherical shape with less surface area. As a result, interparticle forces become weaker resulting in lower boiling point.

My problem is that if it attains a spherical shape then how is its surface area less because sphere has the largest surface area?
So please anyone can help me by answering in simple language?


texts: Spontaneous inequilibrium in a gas in an isolated system?

texts:
Can an isolated system(of several phases) in equilibrium by itself move out of equilibrium?
if a system contains for example an inflammable gas dispersed with another combustible gas such that the molecular speed are insufficient to cause the reaction. but as the molecular speeds keep fluctuating, at some point, it may cross the energy barrier and may start the reaction which will eventually spread evenly but till then the temperature there would be high and thus the system in inequilibrium.
isn't this also an example that although the free energy is minimum and entropy maximum, some useful work would've been done if the temperature gradient had been utilised?


texts:
So I've been trying to understand what exactly aromaticity means, and I've come to know that compounds possessing benzene rings are aromatic, like toluene and phenol. It thus made sense to me that the benzylic carbocation should be aromatic, as it fulfills all conditions of Huckel's rule. However, I found no mention of it being aromatic anywhere. Can anyone tell me if it is indeed aromatic or is only resonance stabilised, and if it is not aromatic, why so? What criteria is it violating?

Sorry if this is an elementary question, I really want to know what aromaticity actually means and am stuck on this.


texts: Why do spectra of elements never overlap?

texts:
I understand the concept behind how spectra is formed, through exciting the electron beyond it's ground state, however my question is why do the spectra of the elements never overlap?

From my understanding, the wavelengths of light produced are decided by the distance the electron travels when falling back down.

However, what is the factor that guarantees that all of these spectra will be unique? I think part of my confusion also stems from the fact I do not know which electrons "jump" - is it just the valence ones or also the ones in the middle? I thought that perhaps different energy levels have different distances but this sounded a bit funny to me.


texts: What happened to the Klopman - Salem equation?

texts:
I am relatively new and interested in the field of theoretical chemistry.
I just stumpled across the Klopman - Salem equation (https://en.wikipedia.org/wiki/Klopman-Salem_equation).

In daily life, I only use DFT for bonding energies and I also do not find too many papers about the Klopman - Salem equation, why? (There is not even a pre-defined tag for this equation on stackexchange.)

What are the advantages and disadvanatges of this theory? Are there any theories, that improved this concept ?


texts: Does it change the compound if the element letters in its molecular formula are switched?

texts: Does it change the compound if the element letters are switched? ex. $\ce{HO}$ or $\ce{OH}$. Are those two different compounds or are they one in the same?


texts:
Consider a combustion reaction like the complete combustion of ethane. Here is what I have for the complete combustion as well as the oxidation and reduction:
$$\ce{\overset{-3}{C}_2\overset{+1}{H}_6 + \frac{7}{2} \overset{0}{O}_2 -> 2 \overset{+4}{C}\overset{-2}{O}_2 + 3 \overset{+1}{H}_2\overset{-2}{O}}$$
$$
\begin{align}
\ce{2 H2O + C2H6 &-> 2 CO2 + 10 H+ + 10 e-}\tag{ox}\\
\ce{\frac{1}{2} O2 + 10 H+ + 10 e- &-> 5 H2O}\tag{red}
\end{align}
$$

Why is it that when writing the reduction half equation for the reduction of oxygen that we don't consider oxygen being reduced into carbon dioxide? i.e. why isn't the reduction equation something of the form $\ce{O2 -> H2O + CO2}~?$

Also the oxidation reaction suggests that water is required initially for the reaction to proceed, is this true?

Edit
I realise my reduction half equation is not balanced and so I now have this equation:
$$\ce{\overset{-3}{C}_2\overset{+1}{H}_6 + \frac{7}{2} \overset{0}{O}_2 -> 2 \overset{+4}{C}\overset{-2}{O}_2 + 3 \overset{+1}{H}_2\overset{-2}{O}}$$
$$
\begin{align}
\ce{2 H2O + C2H6 &-> 2 CO2 + 10 H+ + 10 e-}\tag{ox}\\
\ce{\frac{7}{2} O2 + 14 H+ + 14 e- &-> 7 H2O}\tag{red}
\end{align}
$$
which is clearly not correct as the reduction and oxidation half equations do not add together to give the combustion reaction and the reduction equation does not have the $\ce{CO2}$ product as well. I guess my question now stands as how might I write (or begin to write) the half equations for a combustion reaction?
Edit 2
I realise I wrote my equations wrong above
$$
\begin{align}
\ce{4 H2O + C2H6 &-> 2 CO2 + 14 H+ + 14 e-}\tag{ox}\\
\ce{\frac{7}{2} O2 + 14 H+ + 14 e- &-> 7 H2O}\tag{red}
\end{align}
$$
But my question still remains. Why do we not consider the reduction of $\ce{O2}$ into $\ce{CO2}$ as well?


texts: Electrochemistry - Understanding Diffusion Potential

texts:
I have a big problem trying to wrap my head around this for several hours and I cannot seem to make sense of it.
I have to link this scheme with the 3 colored potential profiles on the bottom of the picture. Considering the electrolyte AK, which splits into A- and K+, that it is 10x more concentrated in compartment I (left) and that the 3 different cases are the assumed:

1) Mobility of A- >>> than mobility of K+
2) Mobility of K+ >>> than mobility of A-
3) Both ions have an equal mobility

Now, I know that in the 1) case, anions will diffuse through the membrane and work toward balancing their concentration. However, this will generate a potential difference because K+ cannot move and compartiment I will be left with a higher potential. Now, I can imagine that if we set our reference (left electrode) at an arbitrary number, let's say 0, then we can assume compartiment II being negative potential in respect to I. This leads to the constant value of the Nernst eq. for same metal electrodes and electrolyte with 10x concentration difference of 59 mV. Since II is considered lower potential VS I in case n°1, should I assume that the potential difference at the membrane's level is -59 mV (green profile)? And another +59 mV between the electrodes because of Nernst equation, which would bring to a final measured potential of 0V. Is this a legit reasoning?

Thank you in advance.


texts: What is p defined as for the expansion and compression of an ideal gas system in the equation ΔU = ΔH - pΔV?

texts:
$$\Delta U = \Delta H - p\,\Delta V$$

Consider a gaseous system in a container with a frictionless piston, and a pressure outside the container.

Is the pressure outside the container assumed to always be constant?
Is the pressure inside the container assumed to always be constant? I assume no looking at the graph of Boyle's Law.
For expansion of the gas, work is done by the system (i.e. the gas in the container) on the surroundings, so is $p$ the pressure of the surroundings as work is done against the pressure of the surroundings?

This doesn't seem to be the case in several examples in my lecture notes:
e.g. calculate the work done against pressure of 1 bar at 298 K when 1 mol of zinc is dissolved in aq. HCl.

Here, work is being done against the pressure of the surroundings, so I'd expect $p$ = pressure of surroundings. However, the notes say 'consider $p(\Delta V) = (\Delta n)RT$' and proceeds to input the number of moles of hydrogen gas. So here $p$ is taken as pressure of the hydrogen gas produced.

For compression of the gas, work is done by the surroundings on the system, so is $p$ the pressure of the gas in the container as work is done against this pressure?


texts: What is the stereochemistry resulting from hydroboration of 1-methylcyclopentene?

texts:
What is the major product of the following reaction sequence?

I'm supposed to work out the structures of both 2 and 3, but I already know 2 to be 1-methylcyclopentene (as the most substituted alkene is formed during elimination).

For the hydroboration step, boron should add to the less substituted carbon (in an anti-Markovnikov fashion). However, I'm not sure which of the two choices B and C is correct. Why should one diastereomer be formed preferentially over the other?


texts:
There are claims that the bamboo fiber has inherent antibacterial properties due to "bamboo kun".
However I could not find anywhere what is the chemical composition of this "bamboo kun" and also no evidence to substantiate the antibacterial claims.

Does anybody know if bamboo kun is a myth or it really has a known chemical structure?

Edit1:

check out wikipedia: https://en.wikipedia.org/wiki/Bamboo_textile

  Bamboo also contains a substance called bamboo-kun – an antimicrobial agent that gives the plant a natural resistance to pest and fungi infestation

google books: https://www.google.com/search?tbm=bks&q=bamboo+kun

Edit2:

Also I could not find this Japan Textile Inspection Association which lots of sites making the antibacterial claim above are citing as the source of antibacterial validation (although there is a Japan Textile Federation that has nothing to do with the above claims):

http://www.bambrotex.com/second/bc_nab.htm
https://www.textilemates.com/bamboo-fibre/
https://highlineorganix.com/pages/why-bamboo
https://www.weber-textilien.ch/bademantel/50-210-bambou-bademantel-mit-schallkragen.html
https://web.archive.org/web/20111005122758/http://www.fashionandearth.com/us/bamboo-clothing-facts.html


texts: IS DMSO-o a σ-donor, a π-donor, or both?

texts:
DMSO is an ambidentate ligand that can bind in a κO fashion via the oxygen lone pair and in a κS fashion via the sulfur lone pair.

I know that DMSO can behave as a π-acceptor when it bonds a metal at the sulfur, but what is the symmetry of the $\ce{O\bond{->}M}$ MO when DMSO binds at the oxygen? I have some diagrams of DMSO's HOMO and LUMO MOs, and it seems clear that DMSO-κS is a π-acceptor due to the LUMO's potential to overlap with a $\mathrm{t_{2g}}$-type d orbital, but the HOMO looks like it would do a π interaction. This confuses me because I know from IR that the $\ce{S-O}$ bond is weakened when DMSO binds at the oxygen, and there are some lower energy occupied MOs that would have σ symmetry overlapping with $\mathrm{d}_{z^2}$, for instance.

Is DMSO-κO a σ-donor, a π-donor, or both?

(keep in mind that there are some more σ-donor-looking MOs at energy levels below the HOMO)

Also; The reference below (1) says that DMSO's tendency to bind as DMSO-κS is dependent on the metal having a high enough "electron charge density" to have a sufficient back donation contribution to the $\ce{M\bond{->}S}$ π bond. What does this mean? The paper also says that ruthenium and rhodium prefers to bind as DMSO-κS. Based on Pearson's HSAB concept, I would expect that ruthenium would prefer DMSO-κS because it is a soft acid as a result of its larger second-row ionic radius giving it lower charge density (and S is softer than O), but the paper seems to be saying the opposite. What do they mean by "electron charge density"?

(1) Panina, N. S; Calligaris, M. Inorg. Chim. Acta 2002, 334, 165-171.


texts: Is it correct to write a state symbol of "g" or "l" for an electron? In the textbook I am currently reading, the state symbol "g" was used for the electron when it described the electron gain by a proton in the gas phase. However, I recall that my chemistry teacher mentioned that electrons should not be given any state symbols, which I agree with. Just like how we do not assign a a physical state to an atom. E.g. We do not say an atom of gold is in the liquid state. I would like to know what is the purpose of assigning state symbols to electrons, if there is one? And would that be chemically accurate?


texts: Why is it that when you consume something that is sugary-sticky (like candy, chocolate, fruit juice, etc.) and get it on your skin, when you try to clean it off with saliva (particularly, licking/sucking it off) it doesn't work?  What is it about the makeup of saliva that doesn't dissolve the sugar?


texts: Does lower activation energy definitely mean higher rate? For example the decomposition of $\ce{H2O2}$. Can we say it has the highest rate with the catalyst making the reaction's activation energy the lowest?


texts: Nucleophile substitution in nonclassical carbocation

texts:
In nucleophilic substitution of exo-2-norbornyl brosylate, carbocation formation is the rate determining step and the carbocation formed is: (in equilibrium)

After forming carbocation, the nucleophile will fill its electron on newly formed the vacant orbitals:

But this is not the product given in the book by FA Carey.
The given product is:


texts:
While comparing the stability, as the $\ce{CH3}$ group is electron donating, the first structure should be more stable due to this reason.
But apparently the second one is more stable. Is there another phenomenon taking place here?


texts: How to determine whether paper was dipped in acetone?

texts: I was wondering if there was a solution of some sort that would cause a reaction to paper that was previously dipped into acetone much like in a counterfeit pen the iodine causes a reaction when written on standard paper .


texts:
Why is the combination of hydrated aluminium oxide and magnesium hydroxide used to treat heartburn?

I get why $\ce{Mg(OH)2}$ would be used since its a strong base and is badly soluble in water. Thus it won't do harm to the oesophagus in comparison to something like $\ce{NaOH}$. Aluminium oxide is also poorly soluble, however it is a weak base so what is the point of combining this substance with magnesium hydroxide instead of just increasing the dose of magnesium hydroxide?


texts: Does electrostatic polarity in aluminum or alcohol based dye affect adhesion. If so, what would encourage the best adhesion?

texts:
I am trying to find the best method to encourage adhesion of a wood alcohol based dye to 6061 aluminum. The results I have gotten have generally been a somewhat blotchy appearance, and a uniform appearance is desired. Current Method:

Place about 2K parts in a rotating tumbler with a spherical vessel of 2 gallons that has a 3.25" throated opening.
Tumbler rotates a 40 rpms
inject 1 tsp dye. parts are usually coated within 15 seconds
once coated blow compressed air (50 psi) to dry parts.
Parts are usually dry within 30 seconds.
See results in picture

Would polarity affect adhesion? If so, how would one go about providing the correct polarity?
Would heating the parts affect adhesion?
Would hot air drying affect adhesion?


texts: Synthesizing 2-bromoaniline from bromobenzene

texts:
I am trying to synthesize 2-bromoaniline from bromobenzene. I came up with a reaction path, but I want your thoughts on whether this is feasible and can produce a decent yield.

Sulfonation of bromobenzene (to block the para position)
Nitration of the product from (1). This should produce 4-bromo-3-nitrobenzenesolfanic acid.
Reduction of the nitro group via Zn(Hg) and HCl (to turn the NO2 group into NH2).
Reverse sulfonation (to get rid of the sulfonic acid group).

And the final product from this should give 2-bromoaniline. Should this theoretically produce a decent yield even if bromobenzene is slightly deactivated?


texts: Why is acetone less acidic than cyclohexanol?

texts:
The $\mathrm{p}K_\mathrm{a}$ of acetone is 19, whereas the $\mathrm{p}K_\mathrm{a}$ of cyclohexanol is 16.

However, acetone is resonance stabilized and its major resonance structure displays the negative charge on an oxygen atom, like cyclohexanol. Is there any qualitative reason to explain why acetone is less acidic than cyclohexanol?

Thank you very much.


texts:
What are the products A and B in the following reaction?

According to me, the $\ce{NH2^-}$ anion being a strong base would form an alkoxide ion. But since there are 3 $\ce{OH}$ groups it will form the most stable alkoxide ion and since a primary alkoxide ion is most stable the alkoxide ion will be formed at the $\ce{-CH2OH}$ site. This ion will undergo a nucleophilic substitution reaction forming an ether. But this is not the correct answer. If anyone could point out where I am wrong, please?
According to the textbook the correct structure of compound B is


texts: Heat transfer dependence on temperature gradient?

texts:
Is the rate of heat transfer between two bodies brought into thermal contact dependent upon the different in temperature between them, assuming they each have the same mass?
Imagine two bodies of water connected to each other by an impermeable glass barrier. If the difference between the temperatures is 10 degrees, will the system reach its equilibrium state faster per degree than if the difference is one degree?


texts: What causes spray cans to get cooler when shaken?

texts:
I've been searching the web for this phenomenon and surprisingly I found only one post about it. And the reply to this question about canned air begins with words:

  I don't know about the shaking part (it is hard for me to see how that would make a difference)

This beginning has strongly shaken my faith, so for sure I picked up a can with deodorant and shaken it. And it does become cooler. Significantly! After standing still, the can doesn't seem to become warmer, so this reaction doesn't revert itself and maybe is irreversible.

As I imagine it, when being shaken the average pressure in the can as a whole can't possibly change. Also it's interesting how you add energy by shaking only to have more energy drained by cooling.

So please, can you explain this strange behavior? Could you also cover the energy flow? When does the energy return back out of the can?


texts: Reaction of nitro compounds with strong alkali?

texts:
Why does a primary and a secondary nitro compound behave as an acid in the presence of strong alkali whereas tertiary nitro compounds do not?
Can anyone explain it with reactions?


texts: Is there a convention for breaking chemical formulae across lines?

texts:
I found a chat where a user asked for chemical formulae to be broken across lines (with LaTeX/mhchem). I could imagine offering a switch to allow this. But only, if line-breaking within formulae is not completely uncommon.

According to him/her, possible breaking points in $\ce{[nBu4N]2[(UO2)2(\mu-\eta^2:\eta^2-O2)(NO3)2(\mu-Au(CN)2)2]}$ would be
$\ce{[nBu4N]2~\color{red}{|}~[(UO2)2~\color{red}{|}~(\mu-\eta^2:\eta^2-O2)~\color{red}{|}~(NO3)2~\color{red}{|}~(\mu-Au(CN)2)2]}$.
So a rule could be "allow a line-break before (, [ or \{ (which would introduce another possible breakpoint into the example).

Is it common to break long formulae across lines and is doing so sensible?


texts: Oxidative chlorination mechanism (sulfide to sulfonyl chloride)

texts: I cannot find much guidance in the literature. Any ideas as to what the mechanism of this reaction might be?


texts: Functional variation in derivation of the Hartree-Fock equations

texts:
In Szabo and Ostlund's Modern Quantum Chemistry, the procedure of single determinant energy minimization is presented. Omitting the whole procedure, I have a question about functional variation during the derivation of the Hartree-Fock equations.

Given the single determinant $| \Psi_0 \rangle = | \chi_1 \chi_2 \ldots \chi_a \chi_b \ldots \chi_N \rangle$, the energy $E_0 = \langle \Psi_0 | \mathscr{H} | \Psi_0 \rangle$ is a functional of the spin orbitals $\{ \chi_a \}$. $E_0$ is the expectation value of the single determinant $\vert \Psi_0 \rangle$,

$$
E_0[\{ \chi_a \} ] = \sum\limits_{a=1}^N [a\vert h \vert a] + \frac{1}{2} \sum\limits_{a=1}^N \sum\limits_{b=1}^N [aa \vert bb] - [ab \vert ba].
$$

This equation can be varied:

$$
\begin{align*}
\delta E_0 &= \sum \limits_{a=1}^N [\delta \chi_a | h | \chi_a] + [\chi_a | h | \delta \chi_a] \\
&+ \frac{1}{2} \sum \limits_{a=1}^N \sum \limits_{b=1}^N [\delta \chi_a \chi_a | \chi_b \chi_b] + [ \chi_a \delta \chi_a | \chi_b \chi_b] + [ \chi_a \chi_a | \delta \chi_b \chi_b] + [\chi_a \chi_a | \chi_b \delta \chi_b] \\
&-\frac{1}{2} \sum \limits_{a=1}^N \sum \limits_{b=1}^N [\delta \chi_a \chi_b | \chi_b \chi_a] + [ \chi_a \delta \chi_b | \chi_b \chi_a] + [ \chi_a \chi_b | \delta \chi_b \chi_a] + [\chi_a \chi_b | \chi_b \delta \chi_a] \label{1}\tag{1}
\end{align*}
$$

Authors suggest to the reader as an exercise to manipulate this equation for $\delta E_0$ to show that

$$
\delta E_0 = \sum \limits_{a=1}^N [\delta \chi_a | h |\chi_a] + \sum \limits_{a=1}^N \sum \limits_{b=1}^N [\delta \chi_a \chi_a | \chi_b \chi_b] - [\delta \chi_a \chi_b | \chi_b \chi_a] + \text{c.c.} \label{2}\tag{2}
$$

It is clear that the first sum in $\eqref{1}$ can be easily converted to that in $\eqref{2}$ because

$$
[\delta \chi_a | h | \chi_a]^* = [\chi_a | h | \delta \chi_a]
$$

Analogously, for the second sum in $\eqref{1}$ one can show that

$$
[\delta \chi_a \chi_a | \chi_b \chi_b]^* = [\chi_a \delta \chi_a | \chi_b \chi_b]
$$

and

$$
[\chi_a \chi_a | \delta \chi_b \chi_b]^* = [\chi_a \chi_a | \chi_b \delta\chi_b].
$$

I did the same manipulations with the third sum in $\eqref{1}$ and obtained

$$
\begin{align*}
\delta E_0 &= \sum \limits_{a=1}^N [\delta \chi_a | h | \chi_a] \\
&+ \frac{1}{2} \sum \limits_{a=1}^N \sum \limits_{b=1}^N [\delta \chi_a \chi_a | \chi_b \chi_b] + [ \chi_a \chi_a | \delta \chi_b \chi_b] \\
&- \frac{1}{2} \sum \limits_{a=1}^N \sum \limits_{b=1}^N [\delta \chi_a \chi_b | \chi_b \chi_a] + [ \chi_a \delta \chi_b | \chi_b \chi_a] + \text{c.c.} \label{3}\tag{3}
\end{align*}
$$

So, comparing $\eqref{3}$ and $\eqref{2}$ I suppose that one should show that both terms in each sum are equal, i.e.

$$
[\delta \chi_a \chi_a | \chi_b \chi_b] = [ \chi_a \chi_a | \delta \chi_b \chi_b]
$$

and

$$
[\delta \chi_a \chi_b | \chi_b \chi_a] = [ \chi_a \delta \chi_b | \chi_b \chi_a].
$$

So, how to do that?


texts: How to assign priority groups of tartaric acid?

texts: How do we assign priority groups of tartaric acid? Counting outwards from any of the chiral carbons we get the same atom.


texts: Metering Device decreases pressure yet produces saturated liquid?

texts:
This question pertains to the change of state of liquid using a Metering Device as the refrigerant enters an Evaporator Coil of an HVAC system:

The Metering Device takes liquid and then reduces the pressure and then spits out 75 percent liquid and 25 percent vapor. I don't understand why decreasing pressure, thus decreasing temperature will create a saturation point where liquid is both water and vapor. Shouldn't it be the other way around? Decreasing pressure should change saturation point so the liquid is both water and ice.

This is my rationale behind what I say:

In terms of changing of state of a liquid, as you add more heat content (molecules in motion or BTU), such as 340 BTU all the way up to 1310 BTU, all the liquid is converting into gas. This is latent heat. So adding heat changes liquid to gas. Conversely, when we remove heat it changes state of liquid to ice. At 0 degrees F and 0 BTU, you have ice.

In terms of gas laws, if you compress a gas to reduce its volume, both the temperature and pressure will increase. If you expand a gas to increase its volume, both the temperature and pressure will decrease.

We can use PSI or PSIA (absolute) to measure pressure per square inch of area. If you look at a Pressure Temperature Chart for Water, 212 Degrees F and 14.7 PSIA is at saturation where there is both liquid and vapor. If we add any heat, it will change state from liquid to vapor.

If we reduce the atmospheric pressure (e.g. from 14.7 PSIA to 0.33 PSIA) and if we put the water into a vacuum (e.g. from 29.6 inHg to 0.68 inHg), then we can change the state of the water at 70 degrees F. Why? Because decrease in pressure means decrease in temperature.

Consequently, how is reducing pressure creating vapor in the case of the Metering Device?


texts: How to convert micromolar concentrations into molar quantities, when the volume is also known

texts:
\begin{array}{c|cccccc}
\text{Sample} & \text{Ammonia} & \text{Phosphate} & \text{Silicate} &\text{Nitrate + nitrite} & \text{Nitrite} & \text{Mn} \\
 & (\pu{\mu M}) & (\pu{\mu M}) & (\pu{\mu M}) & (\pu{\mu M}) & (\pu{\mu M}) & (\pu{\mu g L-1}) \\
\hline
\text{Water} & 0.02 & 0.51 & 9.92 & 9.93 & 0.00 & 0.2 \\
\text{Core 1} & 189.74 & 6.13 & 24.56 & 0.73 & 0.73 & 320.2
\end{array}

The samples are from sediment cores. Different cores have different volume; I need to work in quantities rather than concentrations. I need to calculate the mole (actually micromole) quantities of the $\ce{Mn}$, $\ce{NH3}$, $\ce{NO3-}$ and $\ce{NO2-}$ from their concentrations. The volume for core 1 that is provided here is $\pu{6.86 L}$.

Perhaps I'm being silly, but I am not sure how to do this and how to present this data that is to plotted as follows: molar quantities of the nutrients and metals ($y$-axis) against the oxygen molar concentration ($\pu{\mu M}$) of the water ($x$-axis).

I am also supposed to explain the results in terms of redox chemistry and try to determine approximately at what oxygen concentration in the overlying water these redox reactions in the underlying sediment are initiated.


texts:
What is the correct IUPAC name (or least incorrect one, if the current rules can't precisely describe that) of the interesting species $\ce{[C6(CH3)6]^{2+}}$ (which is extensively discussed here), containing exotic hexacoordinate pyramidal carbocation* ?

The structure can be drawn as

or

My guess is methyl(pentamethyl-η5-cyclopentadienyl)carbon(2+).

*) Some structures in the Wikipedia article have the two positive charges placed into the cyclopentadienyl (aromatic) ring, which I think is incorrect.


texts: Why does fluorine stabilise a carbocation?

texts:
I have read that halogens have a stonger -I (inductive effect) than +M (mesomeric effect),then why do they stabilise a carbocation instead of destabilising it?

I asked this doubt to my teacher and he said that halogens like fluorine do not exert -I on a carbocation and hence they stabilise a carbocation through +M,is this true?


texts: How can I avoid crystallisation of sugars in vinegar at low temperatures?

texts:
I produce high density balsamic vinegar, when it's winter and the temperatures are very low, high density products tends to crystallize. think this is a problem of over saturation of the glucose. The main sugars are glucose and fructose the ratio is 1:0.95.

I try to make products that are lower than 70 brix, or 1,35 density and 6% acidity, composed by $\ce{CH3COOH}$ and tartaric acid.

How can I exactly calculate the solubility threshold of this mixture? How can I measure it?

How can I prevent the crystallization to happen?

Thank you very much
I can't sleep at night because of this problem !!!


texts:
I managed to solve the question till D but I'm stuck at the last reaction.
I tried to find its solution and the source suggest it as


texts: When water boils at its boiling point how do we call it as an equilibrium?

texts: On boiling, water becomes a vapor, liquid volume decreases and vapour volume increases.  Since volumes are not constant, how do we call it as equilibrium?


texts: Is ion activity in a salt solution pH-dependent?

texts:
:) Without being a chemist myself, I need some basic understanding of the ion activities in my buffer solutions.

Now I am wondering whether the ion activity of the K$^+$ and Cl$^-$ ions is different for the buffers with different pH-values.

When I google for that, all I get is ion activity for the hydrogen ion, which -I think- does not interest me at all.

If the ion activity actually IS different, could you point me to some table to look up the correction values?

Thank you!

.

edit: tl&dr:

The buffer solutions contain:
Buffer A: 250mM KCl, 10mM MOPS
Buffer B: 020mM KCl, 10mM MOPS

pH is set to 5,6,7 resp., using unknown amounts of Tris.

Is the ion activity of K$^+$ and Cl$^-$ affected by the pH?


texts: What is the difference between reversible and irreversible work done in adiabatic process?

texts:
The work done in an adiabatic reversible process is given by:
$$W = R\frac{\Delta T}{1-\gamma}$$

The work done in an irreversible process is given by:

$$W = P_{ext}\Delta V$$

By the 1st law of thermodynamics, the change in internal energy must be equal to the work done. The change in internal energy is given by:

$$\Delta U = nC_v\Delta T$$

where $C_v$ is the molar heat capacity at constant volume.

Can't this equation be applied to both the processes? Why are there different formulae for the two types of adiabatic processes?


texts:
I understand the principle behind an eraseable pencil. Graphite is highly slippery, you rub it onto the paper, and an eraser can rub it off again.

I've had friends at school with 'eraseable ink pens'. The ink was 'special' and the eraser was 'special' and it could erase the pen in the same way a regular eraser could erase pencil.

My question is - how do eraseable pens work? (Ie what substances are involved and what are their properties?)


texts:
Can anyone explain this trend (the amines are listed in order of increasing basicity)?

Actually, I thought of understanding this by thinking of inductive effect of the alkyl groups attached to the amine group but since they are cyclic I am confused how to apply the inductive effect here or I want to know whether there are other ways of dealing with this problem.


texts: I have a problem given as :-  I thought of a sn1 type mechanism in acidic medium and a sn2 pathway in basic medium .  Am I correct or not . Please also check the mechanism according to which I formed the answer for acidic conditions...... help would be appreciated and thanks in advance


texts: How ethylbenzene and 1,2‐xylene are chain isomers?

texts:
How the following two structures are chain isomers?

According to what I have studied in nomenclature when a compound has both cyclic and straight chain, we consider that the chain as parent chain according to the following order:

functional group;
multiple bonds;
maximum number of carbons.

Following the above order, I came to the conclusion that both structures have benzene as their parent chain. Since both have benzene, then how they come to be chain isomers?

Please explain to me in simple terms because I am just a beginner.


texts: Where will the oxygen atom be inserted on the Baeyer-Villiger esterification?

texts:
On our exam in organic chemistry, there was a question that I failed to answer correctly. The question is about the Baeyer-Villiger esterification of propiophenone or ethyl phenyl ketone:

On the exam, I answered with this structure:

But when the exam paper came back, I learned that the answer was where the oxygen is inserted adjacent to the aromatic ring:

How can I resolve this dilemma of mine so I can prevent this mistake from happening?


texts:
Find the heat of combustion for 1 mol of $\ce {C21H44}$ in the reaction where some wax is oxidized to elemental C (soot) and water vapor. The Heat of Formation of $\ce {C21H44}$ is -476 kJ/mol.

When it says some, does that necessarily change the molar ratio?
I thought the balanced equation would be:

$\ce {C21H44 + 11O2 -> 21C (graphite) + 22H2O}$

$\ce {O2}$ and elemental carbon are zero for heat of formation

22(-241.818 kJ/mol) - (-476 kJ/mol) = -4843.996 kJ/mol

Is this right?

Thanks


texts: Why is the effect of ring activators more dominant than ring deactivators?

texts:
In 3-nitroaniline, if it were subjected to an electrophilic substitution reaction, the electrophile will most likely attack at (b) or (d) as mentioned in my textbook.

To me, it seems that the only role of the nitro group is that the electrophile will not attack at (a) due to steric hindrance. So my question is, why is the -M effect of the nitro group ($\ce{-NO2}$) discarded and only the +M effect of $\ce{-NH2}$ plays a role? Nitro group is meta directing, so why wouldn't the product form at (c) as well? It is as if the nitro group doesn't even exist. In better words, why is the effect of the ring activator, $\ce{-NH2}$, more dominant than the effect of the ring deactivator, $\ce{-NO2}$?


texts:
I read something recently that said "BN has been observed in the gas phase, is paramagnetic, and has a vibrational frequency lower than N2. These properties can be explained by the molecular orbital diagram of BN".

However, when I drew such a diagram, I failed to see how it described any of these properties, particularly paramagnetism, because there were no lone pairs of electrons. Any ideas?


texts: Reaction mechanism for reduction of alkyl halide to alkane

texts:
Alkyl halides are reduced by zinc and dil.  $\ce{HCl}$ into alkanes
   $$\ce{ CH3Cl + H2 ->[Zn][dil\text{.} HCl]CH4 + HCl}$$

What I don't understand is the underlying mechanism behind this reaction,  is it free radical or nucleophilic substitution.  If it is the latter, then why isn't $\ce{CH3-CH3}$ a product?
I would appreciate if someone could explain the entire mechanism behind this reaction.


texts: Why can't an electrochemical cell be a single cell?

texts: If I put two electrodes of two different metals in 1 solution containing ions for both of the metals and connect these electrodes with a wire, do I still have an electrochemical cell ? Or does it have to be made of two half cells in 2 different solutions joined by a salt bridge? If so,why ?


texts: Why is Maleic Acid more soluble in water than its trans isomer Fumaric Acid?

texts:
My teacher taught me that compounds having intramolecular H-Bonding are relatively less soluble in water as they will not involve in H-Bonding with water appreciably while those able to do intermolecular H-Bonding will appreciably form H-Bonding with water, and thus the latter ones will be relatively more soluble in water.
Applying this logic will make maleic acid less soluble than fumaric, but that's not the case. Wikipedia shows 478.8g/L for maleic, while just 4.9g/L for fumaric. Can someone help me with where I am going wrong?


texts: Why do raisins bob up and down in carbonated water?

texts:
Yesterday I preformed a fun little experiment where I poured a glass of seltzer water into a glass, then dropped a few raisins into it.

I observed that the raisins would float at the top of the glass for a few seconds, then sink all the way to the bottom, then float back up, and repeat seemingly without end.

Why does this happen?


texts: How to find the pH of acetic acid after adding sodium hydroxide?

texts:
$3\cdot 10^{-2}\ \mathrm{mol}$ of $\ce{NaOH}$ are added to a $1\,\mathrm{l}$ solution of $2\cdot10^{-2}~\mathrm{M}\ \ce{CH3COOH}$. Find the $\mathrm{pH}$ of the solution.

I don't understand why my solution is wrong:

I said this, $\ce{NaOH + CH3COOH -> H2O + CH3COONa}$, so I'm left with $2\cdot10^{-2}~\mathrm{mol}$ of $\ce{CH3COONa}$ and $1\cdot10^{-2}\ \mathrm{mol}$ of $\ce{NaOH}$.

Now, from those $1\cdot10^{-2}\ \mathrm{mol}$ of $\ce{NaOH}$ I get the same moles of $\ce{OH-}$ (from dissociation).

Then, $\ce{CH3COONa -> Na+ + CH3COO-}$, and $\ce{CH3COO- + H2O <=> CH3COOH + OH-}$

Setting up the equilibrium equation: $K_h = \frac {\text{Products}}{\text{Reactants}}$, I get (where $K_h= K_\mathrm{w}/K_\mathrm{a}, K_\mathrm{a} = 1.8\cdot 10^{-5}$):

$$K_h=\frac {(x)(1\cdot 10^{-2}+x)}{x-1\cdot10^{-2} }=5.55\cdot 10^{-10}$$

Which yields $[\ce{OH-}]= x= 1.11\cdot 10^{-9}$ and so $\mathrm{pH}=5.04$ which is wrong. I know the answer should be around 12 from the answer sheet.

What am I doing wrong?


texts: Why is the formation of slacked lime accompanied by a hissing sound and the formation of bubbles?

texts:
My teacher made me write that that the formation of calcium hydroxide (slacked lime) from calcium oxide (qucklime) is described as

  $\ce{CaO + H2O -> Ca(OH)2}$

and that the process

  forms bubbles
  is an exothermic reactions
  makes a hissing sound

Why does it make a hissing sound and form bubbles?

There is no gas evolved in the reaction, then why does formation of bubbls take place?

And what is the reason of the hissing sound being produced?


texts: Why are enthalpies of reaction or Gibbs FE change given in kJ/mol

texts:
It makes no sense to me that these thermodynamic changes are given in kJ/mol. Reactions can have several compounds on both sides and its not clear what exactly the molar variable refers to…

I've been given a homework where this is the convention followed. My temptation is to just ignore the /mol as senseless, and proceed just considering the energy change. But I'm sure I'm wrong.

Can anyone help me?

Thanks.


texts: Strength identification in conjugate acid-base pairing

texts:
I'm a student in highschool AP chemistry. I'm confused about a certain problem in my chem textbook. In summary, I am given a species and asked to identify its basicity as strong, weak, or negligible. I must then give its conjugate acid and identify likewise for its acidity. (in the context of Brønsted-Lowry theory)

I understood all parts of the problem except for $\mbox{O}^{2-}$, to which I assigned the conjugate acid as $\mbox{OH}^{-}$. It was correct thus far. My guess that they were both weak was wrong, however. According to the solutions page, they're both strong!

How is $\mbox{O}^{2-}$ a strong base? How is $\mbox{OH}^{-}$ a strong acid? To my knowledge, neither are found in the canonical strong acid/base lists, and neither seem to satisfy the "completely ionize in water" definition.


texts: Is there any difference between negative electron gain enthalpy and electron affinity?

texts:
Electron affinity is the amount of energy "released" during the addition of an electron in the valence shell of an isolated gaseous atom. The sign convention is opposite to that of thermodynamics convention i.e. positive means release of energy.

For many non-metals, the first electron affinity is exothermic, i.e. positive while all second electron affinities are endothermic, i.e. negative.

As we already know that electron affinity is energy released (the term "affinity" implies an attraction for the electron), then why we consider endothermic cases using this term?


texts: How to calculate air tank capacity from tank displacement, tank fill (gauge) pressure, and specific type of gas?

texts:
I am trying to calculate the amount of a specific compressed gas that will fit in an air tank of specific displacement, at a specific pressure. This is in reference to compressed air guns.

The inputs are:

Tank Displacement (units: cubic inches or cubic centimeters)
Tank Fill (Gauge) Pressure (units: psi or bar)
Type of Gas:

Dry Air
Carbon Dioxide
Nitrogen
Helium

*For this scenario, Temperature is assumed to be constant @ 20C / 68F / 293.15K.

The output is:

Tank Capacity (units: cubic feet or cubic meters)

In other words... an example of a possible question that could be asked pertaining to this would be: "How many cubic feet of helium will fit in a 122cc tank when filled at 3000psi?"

My question is: What amount of specific gas will fit in an air tank of specific displacement when filled at a specific pressure? (Please provide equation along with an explanation)

I am having trouble coming up with the proper equation to use with the given inputs. I have tried the Ideal Gas Law, Boyle's Law, and the Combined Gas Law. I have no way to verify if the answer I am getting is correct because I'm not sure if I'm using the correct equation.

Note: this is not homework. I am a PHP developer. This is functionality I am implementing for a client's website.

Thanks!


texts: Is p-bromophenol more acidic than p-chlorophenol?

texts: p-chlorophenol is more acidic than p-fluorophenol due to presence of vacant d orbitals. But then is p-bromophenol more acidic than p-chlorophenol since it has vacant f orbitals also? But I guess that’s wrong, isn’t it? Please give your suggestions.


texts: How to explain (non-/anti-) aromaticity in fulvene with the help of resonance structures?

texts:
Can someone please explain why the resonance structures of fulvene 1 is non-aromatic and 2 is anti-aromatic?

Why is fulvene non-aromatic, even though it has $4\pi$-electrons and no $\mathrm{sp^3}$ carbons?


texts: Does mixing calcium dichloride and magnesium sulfate induce a reaction, and how does it affect the hygroscopy of the sample?

texts:
I have a problem with a sample made from $\ce{CaCl2*2H2O}$ and $\ce{MgSO4*7H2O}$ in about equal amounts. I took the two salts, pressed them together, and the result was a weird brine that was very wet and almost seemed to turn into water before my eyes.

I am wondering what happened here, and was hoping that someone could walk me through it. As you can tell by the title, I believe that a reaction might be involved that I did not consider when making the sample.

As far as I know, the two salts are both very hygroscopic, so it could be that they simply adsorbed water and that is why the sample became wet. However, the effect seemed more severe after mixing them together, so I am thinking that a reaction might have been involved.

Could it be that the two salts reacted this way?
$$
\ce{CaCl2*2H2O + MgSO4*7H2O -> CaSO4*2H2O + MgCl2*6H2O + H2O}
$$
And if so, what happens with the leftover water that is not bound? Especially since $\ce{MgCl2*6H2O}$ is even more hygroscopic than any of the other salts, could it be that the water was attracted by the $\ce{MgCl2*6H2O}$, which then turned the sample into a brine?

I'm just trying to understand what happened, I did not add any heat, but I did add a lot of pressure.


texts: Nomenclature of benzene derivatives with two functional groups

texts:
In several places, I have seen that while naming benzene derivatives, no priority for substituents is followed. For example, I've seen both 2-hydroxyaniline and 2-aminophenol being used.

Is there an order? Or is the order different from aliphatic compounds?


texts: Should data tables be made in pen or pencil?

texts: For a chemistry lab, I have to make a data table. Should data tables be written in pen or pencil? What is done in the real world of Chemists and why is it done in such a way?


texts: Weighted Drilling Fluid Comparison with CaCl₂

texts:
I asked a question previously, and the answer was quite illuminating. The answer ushered me forth in a direction that finally made sense. I ended up finding this website, chem.latech.edu/~ramu/cmen522/homework/hw06_04a.pdf, that further explained the dynamic as well. I gathered what was necessary to be done, but wasn't quite sure how to apply it. I am currently a chemist for the oil field and am trying to find an accurate representation of percent water and CaCl2*subscript*, as well as the correct specific gravity of the complete solution. Given a 10.5 Mud weight (10.5 lb/gal), I have struggled to find volumes necessary to add and partial volume actually present.

Further explained - I applied the formula designated $V /cm^3 = 1001.97 + 30.2207(m^.5) − 36.7889m + 37.0838(m^1.5) − 5.7447(m^2)$ for the corrected solution volume and was really close to the correct "loss" of volume from the packing that the answer described. The two following formulas for partial volumes$ −36.7889 + 15.1104(m^−.5) + 55.6257(m^.5) − 11.4894m $(for CaCl2*subscript*) and $18.048 + 0.2722(m^.5) − 0.3341(m^1.5) + 0.1035(m^2) $(for water), don't add up to the total solution loss. I am a bit baffled as to why this is the case. Granted my physical chemistry knowledge is a bit dated, I would assume my excel document is correct. At the 10.5 weighted mud, my molality was 3.586. This resulted in a volume of 1105 with fluid loss and a 1183 of theoretical volume. The excess volume then should be 78.27. The formula for the solute given that molality gave me a volume of 17.63 and the solution was 35.33. The volume together is 52.95. This doesn't equal the excess volume which would suggest there was an error in one of the formulas, or that I have made a significant error on my part.


texts: 2-Bromo-1-chloro-4-nitrobenzene reacts with sodium ethoxide

texts:
What are the major products?

I assumed that their is only one that is possible, which would be replacing the chloro group because the resonance structure supports that one. The bromo group doesn't seem to be able to be replaced. Would adding the ethoxide group, allow for the bromo group to replaced?


texts:
Here is a series of related questions that I want to ask.
Background
The activity of acid phosphatase is measured by an enzymatic reaction that converts para-nitrophenyl phosphate (pNPP) to para-nitrophenol (pNP), liberating phosphate. The product, pNP, absorbs light whose wavelength is $\pu{400 nm}$ with an absorption coefficient ($\pu{400 nm}$) of $\pu{19000 M-1 cm-1}$ at extremely alkaline pH. Reaction mixture for an acid phosphatase is slightly acidic. Thus, it must be alkalinized for quantification of pNP.
Two enzyme concentrations are to be examined - They are $\ce{1X}$ and $\ce{0.1X}$ (The $\ce{0.1X}$ enzyme is made by mixing $\pu{1 ml}$ of $\ce{1X}$ enzyme in $\pu{9 ml}$ of $\ce{NaCl}$.) Reaction times for each enzyme is $1$, $10$ and $20$ minutes.
Procedure

Protocol for measurement of acid phosphatase activity:

Mix $\pu{0.12 ml}$ of $\pu{0.5 M}$ $\ce{Na}$ acetate buffer (pH $5.6$) and $\pu{0.24 ml}$ of $\pu{5 mM}$ pNPP in a test tube. Start the reaction by adding $\pu{0.24 ml}$ of an enzyme solution.
After the reaction times of $1$, $10$, and $\pu{20 min}$, respectively, stop the reaction by adding $\pu{0.6 ml}$ of $\pu{0.5 M}$ $\ce{NaOH}$. $\ce{NaOH}$ stops the reaction and converts the pNP produced into a yellow-colored (A400-absorbing) form.
After all reactions are stopped, measure A400 of the samples.

Assay of potato acid phosphatase:
\begin{array}{ll}
\pu{0.5 M} \text{Na acetate buffer (pH 5.6)} & \pu{0.12 ml}\\
\pu{5 mM} \ce{pNPP} & \pu{0.24 ml}\\
\text{Enzyme} & \pu{0.24 ml}\\
\pu{0.m M} \ce{NaOH} & \pu{0.5 ml}\\\hline
\text{Sum} & \pu{1.2 ml}
\end{array}

There are some things I am supposed to calculate after I obtain the results.
First I am going to plot a graph of absorbance versus time and find the slope for each of the lines ($\ce{1X}$ and $\ce{0.1X}$).

I have been asked to find the absorbance change/min/1ml of $\ce{1X}$ enzyme.

My answer: Divide the slope obtained by $0.24$ (the amount of enzyme).

I have to convert the absorbance change to concentration change when
$L$ is $\pu{1 cm}$ and e400 of pNP is $\pu{19000 M-1 cm-1}$.

My answer: This can be found out by $A = eCL$.

The next question is to convert the concentration change to a change in the amount of substance of pNP.

I have no clue how to do this.

Finally, I have to calculate total activity (in moles per minute) in $\pu{4 ml}$ of $\ce{1X}$ enzyme solution.

My answer: Multiply the answer I obtain in the above question by $4$.


texts: Confusion regarding dehydration of 1° alcohols

texts:
My lecturer told me that 2° and 3° alcohols prefer to dehydrate through E-1 mechanism. On the other hand, 1° alcohols tend to prefer the E-2 mechanism, which does not involve the formation of a carbocation intermediate, and thus rues out scope for rearrangement.
This is backed by online sources:

Primary alcohols undergo bimolecular elimination (E2 mechanism) while secondary and tertiary alcohols undergo unimolecular elimination (E1 mechanism). Source

Another site tells me:

You will find two versions of the mechanism for the dehydration of primary alcohols on the web and in various textbooks. One of these is exactly the same as the mechanism for the reaction involving propan-2-ol and other secondary or tertiary alcohols (known technically as an E1 mechanism), but the other is different (known as an E2 mechanism).The more reliable sources give the E2 mechanism for the dehydration of primary alcohols including ethanol. I am going to treat this as the "correct" version, and have added a note as to why I think is better following the mechanism. Sourced from chemguide.

The note goes on to read:

[...]you would get a primary carbocation formed, CH3CH2+, but this is much less stable than a secondary or tertiary carbocation. That would lead to a very high activation energy for the reaction.
The alternative mechanism avoids the formation of the carbocation, and so avoids the high activation energy.

Hence my first question:

What should be the preferred mechanism?

But wait a minute. That wasn't my original question.
My original question is derived from this other post: Benzene from cyclopropane-1,2,3-triyltrimethanol in acidic medium. The comments seem to suggest that this reaction is not known, while another writes that "I strongly doubt it is real".
The top voted answer suggests the formation of a carbocation intermediate leading to ring expansion. And here's where my questions coalesce. The above mentioned compound consists of three $1° OH^-$ groups. This seems to suggest that an E-2 elimination reaction should occur, which rules out the possibility of rearrangement, or for that matter, ring expansion.
TL, DR;

What should be the preferred mechanism for 1°, 2° and 3° alcohols?
If the mechanism for 1° is E-2, why should carbocation induced ring expansion occur in the dehydration of cyclopropane-1,2,3-triyltrimethanol?


texts: Does electron mass decrease when it changes its orbit?

texts:
I have studied  this in my chapter atomic structure that when an electron changes its orbit from lower energy to higher energy state , it does not state in my book that it moves there but that it disappears.It just kind of reaches that orbit without crossing the path.We don’t know whether it moves there or not.
So , I also read about the fundamental properties
of electron in which it said that when an electron moves or is in motion , it’s mass changes.
If we see , We know that electron only absorbs certain wavelength of light. If we can find that when it changes its orbit , if it’s mass decreased or not during that interval.Is it that we can find that whether  electron moves and changes orbit or it just disappears kind of.
Yes , I am only talking electron in an hydrogen atom here.
Please do give your answer in reference to other atoms if it is helpful.


texts: How much energy is there in 1 mol of diamond and how can you get it?

texts: Diamond is made of carbon which is during maybe 3 billion years under pressure is formed in the earth. Imagine you found a big source of diamonds such as coal...how much is the energy of the diamond compared to the coal, and how should you get the energy out of it?


texts:
I'm wondering why an E1cb reaction needs a poor leaving group like -OH attached to one of the carbons.

I thought the conjugate base of the leaving group must be stable enough not to de-protonate one of the newly formed alkene's H's. But if this is the case, why can't a good leaving group like Br be used in E1cb which would neither de-protonate the alkene's H's.


texts: What is the black slag formed when sterling silver is melted with borax?

texts:
What is the black graphite looking slag that is formed when sterling silver is melted with borax?  Is there a way to remove it from the surface of the sterling silver?  It appears to be indestructible!

The melting is related to jewelry casting.  All melting was done in an electric Ney muffle furnace.  Here is a melting dish with some half-melted buttons of sterling silver.

I can't remember why I didn't completely melt this.  I assume the green is salts of copper from the sterling silver.  Notice how the black slag erodes the walls of the melting dish.

Here is a closeup of the erosion.

This erosion property ate through the bottom of my furnace! UGGG! It'll be $600 to replace the muffle.  I heated to 1,900 Fahrenheit for about one hour and this is what I saw when I opened the furnace to get the crucible with the molten sterling silver, but with glowing white-orange light.

Here I have the crucible laying on its side next to the hole.

Here is a close up of the hole and in one of the images I'm lighting it up with a flashlight.  I'd say it's about 1.5 inches in diameter and 1.5 inches deep.  There are 2.25 Ozt of sterling silver down in the hole somewhere because the eroding black slag ate holes through the wall of my crucible.

A closeup of the erosion in front of the main hole.  These two erosion spots were from the previous melt cycle with the same crucible.  I saw that the black slag was penetrating the crucible but I figure it was just minute capillary action and it'd be ok.  Notice that the black slag seems to be working like a catalytic reaction because the amount of borax in the crucible is only about the volume of one grain of white rice.  These two depressions were not depressions at the end of the previous melt cycle they were just flat black areas of the same size and shape.

Here is a view on the outside of the crucible.  I assume one of those holes is where the silver leaked out.

A view inside the crucible.  In person, the black slag has a metallic sheen to it.  It is very similar to the dark grey metallic sheen of graphite.

What is this black slag?


texts:
General Chemistry perspective: Looking at the molecular orbitals of water, we can see that the oxygen is $sp^3$ hybridized. Oxygen forms two sigma bonds with hydrogens, and there are two lone pair orbitals in the molecule. There are five occupied molecular orbitals: The core $1s$ of oxygen, and the four $sp^3$ orbitals, out of which two are lone pair orbitals.

Group Theory and Quantum Chemistry perspective: Water belongs to $C_{2v}$ point group. There are four irreducible representations, and the atomic orbitals belong to these irreducible representations (or linear combinations of these irreducible representations). Hence, we get five occupied molecular orbitals of symmetries $a_1, b_1,$ and $b_2$.

There is only one non-bonding orbital ($1b_1$) in which the AOs of hydrogens do not participate. Where is the second lone pair orbital of water?


texts: Does Dow's process follow Benzyne mechanism or ArSn2 mechanism?In some books I have seen that Dow's process to convert halobenzene to phenol follows ArSn2 mechanism.But nucleophilic substitution in benzene ring mostly follows benzyne mechanism.


texts: Boiling points of ethylene, formaldehyde and oxygen

texts:
The boiling points of ethylene, formaldehyde and dioxygen are $\pu{-103.7 ^\circ C}$, $\pu{-19 ^\circ C}$, and $\pu{−183 ^\circ C}$, respectively. I expect formaldehyde to have the highest boiling point of the three because of dipole moment mostly due to the carbon-oxgyen bond. However, I don't know why ethylene has a higher boiling point than dioxygen.

Different from this similar question, where the atoms involved are of very different size, molar mass, and polarizability, the structure and electronic structure of ethylene and dioxygen are more similar. They both have a single conformation, but they have different symmetry, which might have same bearing on the entropy change during phase transition. I know that both the $\ce{C-C}$ bond in ethylene and the $\ce{O-O}$ bond in dioxygen have a bond order of 2, but dioxygen is paramagnetic while ethylene is not.

The latent heat of vaporization is 6.8 kJ/mol for dioxygen and 13.7 kJ/mol for ethylene, so enthalpy seems a major contribution to the difference in boiling point.

What are the differences in intermolecular interactions in liquid $\ce{O2}$ compared to liquid $\ce{H2C=CH2}$ underlying the difference in normal boiling point?


texts: Is menthol an especially volatile molecule?

texts:
I have been studying a bit about odors and plant essential oils. Several sources claim that the fragrant terpenes found in these oils, such as menthol, eugenol, limonene, linalool, etc. are volatile compounds.

I understand that all molecules are technically volatile, but since these molecules all have boiling points of over $170~\mathrm{^\circ C}$, and their vapor pressures are not particularly high, I don't see why they are considered 'volatile compounds'.

I have two guesses:

a) There is some fundamental aspect of chemistry that I am ignoring, and these compounds do have a set of properties that makes them especially volatile. This to me sounds very interesting, and I would really like to learn what is that makes these compounds especially well-made for being vaporized.

b) The compounds are not especially volatile. They are synthesized in large amounts, concentrated to high concentrations in the plant, and our nose is very sensitive to them. They are called 'volatile' compounds because we happen to notice their smell when they are in the air.

For my question I've chosen to focus on menthol. Is there anything about menthol that makes it especially volatile?


texts: How can x-rays show how many protons are in a nucleus?

texts:
My textbook states that: Henry Moseley found using x-rays that the atomic number of each element has a characteristic positive charge.
I don't know much about x-rays and can't find an answer online or elsewhere. How does this technique work ?
My thoughts are that maybe all protons emit x-ray photons at the same frequency and rate. If this is true then some kind of x-ray detector could be used to detect the energy at that x-ray frequency that a nucleus emits. The number of protons could then be calculated.
I could be way off here.
Can someone explain how x-rays can be used to count the number of protons in a nucleus?


texts: What conditions would make SN1 products the major products over E1 products, and vice versa?

texts:
It seems that if a carbocation intermediate is formed through solvolysis, then the product(s) are going to always be a pretty even mix of SN1 and E1 products.

Are there any conditions that greatly favor one mechanism? I thought that a very bulky solvent - like t-$\ce{BuOH}$ - would favor E1. However, the carbocation is $\ce{sp^2}$ hybridized, so there still wouldn't be a lot of steric hindrance to prevent SN1, right?


texts: What is the simplest way to purify 65% nitric acid (HNO3) to white fuming nitric acid (WFNA which is 98% pure)? Is it  dehydration with concentrated sulfuric acid (H2SO4)? Is distillation needed to be done?


texts:
When there are $2$ hydroxy groups on same carbon, they tend to undergo dehydration ( of course with exceptions like chloral where $\ce H$ bonding prevails).

Why does this happen? We are breaking a sigma bond in order to get a pi bond between $\ce C$ and $\ce O$ ?


texts: Understanding mzML, specifically precursor mass

texts:
I'm a Biotechnologist and computer scientist, migrating into the field of Mass Spec. for my new position. Some things I know well, and others not at all. Please be patient :)

I'm working with OpenMS, Python, MGF and mzML files.

Q1: Is there a better resource for understanding the format of mzML files than PeptideAtlas specifications?

Q2: In the MGF specification you get a listing of the precursor protein mass (PEPMASS) followed by a list of ions in m/z format.

Is the precursor (protein) mass listed similarly in the mzML file? Is it the BPI in (for example)

      <cvParam cvRef="MS" accession="MS:1000796" name="spectrum title" value="runID:160812_29,index:2120,ID:controllerType=0 controllerNumber=1 scan=2121,path:160812_29.raw,scan:2121,activation:HCD,isolation:745.306640625,selectedIon:745.306640625,z:2,precursorScan:controllerType=0 controllerNumber=1 scan=2118,spectrum:MSn spectrum,MSlevel:2,scanstartmin:7.4891189999999996,scanstartsec:449.34713999999997,BPmz:745.4205487,BPI:15730.942999999999,TIC:54362.472999999998"/>

EDIT:
This is what I have so far:

In the  tag, we have...

<cvParam cvRef="MS" accession="MS:1000796" name="spectrum title" value="runID:160812_29,index:2060,ID:controllerType=0 controllerNumber=1 scan=2061,path:160812_29.raw,scan:2061,activation:HCD,isolation:555.730041503906,selectedIon:555.730059736802,z:2,precursorScan:controllerType=0 controllerNumber=1 scan=2060,spectrum:MSn spectrum,MSlevel:2,scanstartmin:7.3208402000000001,scanstartsec:439.25041199999998,BPmz:129.1023507,BPI:17504.615000000002,TIC:1.8637816e05"/>

We have ...

selectedIon:555.730059736802,z:2,precursorScan:controllerType=0 controllerNumber=1 scan=2060,

...followed by...

<cvParam cvRef="MS" accession="MS:1000500" name="scan window upper limit" value="1155.0" unitCvRef="MS" unitAccession="MS:1000040" unitName="m/z"/>

...implying the upper limit is roughly the Precurser mass.

Later we find, in the (of course) precursorList count="1" tag, subtag selectedIonList count="1"  the double the above mass, with a charge count of 2...

<cvParam cvRef="MS" accession="MS:1000744" name="selected ion m/z" value="555.730059736802" unitCvRef="MS" unitAccession="MS:1000040" unitName="m/z"/>
<cvParam cvRef="MS" accession="MS:1000041" name="charge state" value="2"/>

All of this together indicates that precursor mass is ~550 x 2 = 1110.

I can't find any more direct route to this discovery than the deduction.

Is this correct and is it the best route?


texts: Why does butter get soft with heat, but not ice?

texts:
Sometimes a recipe asks me to soften the butter before I use it. This can be accomplished with a few seconds in the microwave, or just by leaving it out at room temperature for a while.

Ice, on the other hand, does not get soft with heat. It just immediately starts melting.

What chemical differences between the two would account for this?