texts: Potential energy surface in transition state theory

texts:
I would like to study the typical reaction from the transition state theory:
$$\ce{AB + C <=> ABC^‡ -> A + BC}$$
Assuming $\ce{ABC^‡}$ is a colinear molecule, the potential energy surface of the system is pictured as in Fig 5.4 on University of Bristol — Potential Energy Surfaces for Triatomic Molecules:

Figure 5.4 - Contour plot PES for a triatomic system. Ligher colours represent greater energies

My questions are:

If I project the potential energy from the figure onto the axis $r(\ce{A-B}),$ I would actually plot the potential energy of the triatomic molecule against $r(\ce{A-B}),$ but not the potential energy of the diatomic molecule $\ce{AB}.$ Is that correct?
Is there a way to obtain potential curve of molecule $\ce{AB}$ and $\ce{BC}$ as well as the atomic energy level of $\ce{A}$ and $\ce{C}$ from Fig 5.4? (I was given the hint that WavePacket program package is able to do this, but I'm not sure how)


texts: What are the rules for constructing Kohn-Sham orbitals?

texts:
I just recently began to study quantum chemistry and need some clarification for the construction of Kohn-Sham orbitals.
Consider a system of several atoms.  Let there be $N$ electrons in this system.
We can reduce the description of such a system to the $\psi_i$ single-electron wave functions describing the orbital, where the index $i$ takes a value from $1$ to $N$.
Now consider the same system in the framework of the  density functional theory.
The description converts to molecular wave-functions $\varphi_j$. Molecular orbitals are obtained from the Kohn-Sham equation:
\begin{align}
  \left(
    - \frac{\hbar^2}{2m} \nabla_j^2
    + \nu_\mathrm{eff}(\mathbf{r})
  \right) \varphi_j(\mathbf{r})
  &= \varepsilon_j\varphi_j(\mathbf{r}), &
  j &= 1,\dots, K.
\end{align}

How is it determined how many molecular orbitals are now? $K=N$?
How do the new molecular orbitals make up the overall wave function of the system?

I am a little confused by the fact that atomic orbitals form molecular ones according to very complex principles and it is unclear how this is taken into account.


texts: What is the difference between the Bohr model and the quantum model?

texts: Specifically, Bohrs atom model gives the radius of an atom as 0.53Å, while a quantum description offers a similar value. What is the difference between these?


texts: How does dimethyl sulfate react with water to produce methanol?

texts:
I came across the reaction of dimethyl sulfate with water to yield methanol. I was curious how that works as $\ce{H2O}$ isn't a strong nucleophile.

From my understanding the $\ce{H2O}$ should pop off a $\ce{-CH3}$ and you have $\ce{[CH3OH2]+}$ which has a $\mathrm{p}K_\mathrm{a}$ of -2.5 so a relatively strong base. Does the $\ce{[CH3OH2]+}$ protonate the $\ce{H2O}$ to form $\ce{H3O+}$ and $\ce{CH3OH}$?


texts: How to dissolve salicylic acid into a solution with humic acid

texts:
I'm not a chemist but I am trying to make a product to be used as a foliar spray on turfgrass for my own use. The product I'm trying to make is:

12% Humic acid ($\mathrm{pH =}$ 3.5-4.0)
2% Fulvic acid ($\mathrm{pH =}$ 9.6)
6% Kelp extract
0.5% Salicylic acid
79.5% Water (local sourced water $\mathrm{pH }$ is 6.8-7.5)

I'd like to make this in $\pu{19L ( 5 gal.)}$ batches.

The humic, fulvic acids and the kelp extract are all soluble in the solution already, so that's the easy part. What I'm looking for is how to dissolve the salicylic acid so that it can be combined with the other ingredients.

The advice I've been given for dissolving the salicylic acid is to first dissolve in ethanol. Add $\ce{KOH}$ to water until I get a $\mathrm{pH}$ of 12, then add the dissolved salicylic acid to the water.

What I'd like to know is:

Is this the right process?
What quantities of salicylic acid/ethanol/$\ce{KOH}$/water should I be using?
Will adding this mixture to my mixture of humic/fulvic/kelp have any negative effect on any of the ingredients?
Any safety concerns beyond the exothermic reaction of $\ce{KOH}$?


texts:
I think all the liquids are viscous. So I was wondering what is meant by a viscous liquid as it is written in the first line of page on Oil at Wikipedia.

  An oil is any neutral, nonpolar chemical substance that is a viscous liquid at ambient temperatures and is both hydrophobic (immiscible with water, literally "water fearing") and lipophilic (miscible with other oils, literally "fat loving"). ...


texts: Is the subtrahend in the Nernst equation related to ohmic drop?

texts:
Let us consider the Nernst equation $$E= E^\circ -\frac{2.303RT}{nF} \log Q$$ which once at $\pu{298.15 K}$, is the equivalent  of $$E= E^\circ - \frac{0.059}{n} \log Q .$$

Does the part of the Nernst equation $-\frac{0.059}{n} \log Q$ address Ohmic drop? In other words, is $-\frac{0.059}{n} \log Q$ related to solution (electrolyte) resistance of an electrochemical cell?


texts: What is the best way to measure ppm of copper in colloidal solution.  My TDS meter only shows at 2ppm which cannot be correct.


texts: What is the difference between an amorphous solid and glass?

texts: They are both formed when a liquid is supercooled rapidly, no free energy, and they both have irregular structures. What defines a glass other than how it is amorphous, transparent, and has a glass transition state?


texts: Clarification in a particular application of Le Chatelier principle

texts: There is something I don't understand about a particular application of the Le Chatelier principle. The following system is in equilibrium: $$\ce{CH3COOH + H2O <=> H3O+ + CH3COO-}$$ If I add some $\ce{H3O+}$ the reaction will shift left. Now if I keep adding $\ce{H3O+}$, it will keep shifting left until the $\ce{CH3COO-}$ would deplete? And would the $\ce{H3O+}$ will remain at its initial concentration? So I can't understand how a buffer work, because if you have a reaction like above and you are adding acid, the added $\ce{H3O+}$ and the $\ce{CH3COO-}$ will bind together to form $\ce{CH3COOH}$ and water thus keeping the $\ce{H3O+}$ exactly the same. Where am I wrong?


texts: Nucleophilic addition of grignard reagent

texts: Here why isn't the phenyl group attacking the carbonyl carbon? Isn't the first step in addition of grignard reagent the attack by the carbanion on the carbonyl carbon ?


texts: Dissolving copper in nitric acid and heating it

texts:
A sample of copper metal is dissolved in 6 M nitric acid contained in a round bottom flask. This reaction yields a blue solution and emits a colorless gas. The water is evaporated form the blue solution to leave a blue solid. When the blue solid is heated further, nitrogen dioxide gas, oxygen gas, and a black copper oxide is left. If all of the blue solid were not decomposed into the black oxide during the final heating, what would be the effect on the calculated percentage of copper in the oxide?

I know that there is a redox reaction of $\ce{Cu + H+ + NO3- -> Cu^2+ + NO2 + O2}$, and the black oxide is $\ce{CuO}$.

I have spent a long time thinking about this question, and my reasoning is that since less copper oxide is formed, the calculated ratio between the original mass of copper and the final mass of copper oxide would be too high.

However, the answer says that the calculated ratio would be too low. Why is this?


texts: How does temperature affect buffer capacity?

texts: I am currently leaning towards an experiment on how certain factors affect the capacity of a phosphate buffer, and am wondering if temperature in any way affects the capacity of the buffer. I know changing the temp will change the Ka of the acid, but am not sure if that changes capacity (how much it resists pH change) or just changes the pH range in which the buffer effective e.g. from 5-8 pH to 4-7 pH.


texts:
*Not sure whether to put this on Phy or chem.. *

What exactly happens when you light an incense stick?

How is this different from a candle, or embers for that matter?

From what I understand, a candle-flame is..... well.... basically a flame and embers are pieces of glowing hot coal or wood, but then where does the lit portion of an incense stick fit in?


texts: Writing a organic reaction in different form

texts:
Can I write this reaction
$$\ce{A + B ->[\ce{X}] C + D ->[\ce{Y}] E + F}$$

as
$$\ce{A + B ->[\ce{(1) X}][\ce{(2) Y}] E + F}$$

Can I write any organic reaction in this way or are there any conditions/rules?

Textbooks sometimes mention this form and sometimes they do not. What I have seen is that they mention mostly oxidation or reduction reactions this way but other reactions like addition are always presented in long form only.
This answer describes a little bit but my question is a little different.


texts: Why is the degree of dissociation for a weak acid α, but for a weak base, it's 1−α?

texts:
From the equation used in this answer: Calculating charge on amino acid from pKa

$$\alpha=\frac{1}{10^{\mathrm pK_\mathrm a-\mathrm{pH}}+1}$$

Degree of dissociation of weak acid is $\alpha$. However, when it comes to weak base, degree of dissociation is $1-\alpha$. What is the explanation behind this?


texts: Inverse problems in Computational Chemistry: The case of Inverse eigenvalue Problems for molecule structures

texts:
Mathematics Background

An inverse eigenvalue problem (IEP) is the problem of reconstructing a matrix
with a special structure from prescribed spectral data. By structure we mean
the pattern of entries that are either zero or nonzero. There are many different types of IEPs with different level of difficulty which depends on the structure of the matrices which are to be reconstructed and the available eigen information. For example consider the following real Jacobi matrix:

$$
A_n = \begin{bmatrix}
a_1&b_1&0&0&0&0& \cdots & 0\\
b_1&a_2&b_2&0&0&0&\cdots&0\\
0&b_2&a_3&b_3&0&0&\cdots&0\\
0&0&b_3&a_4&b_4&0&\cdots&0\\
0&0&0&b_4&a_5&b_5&\cdots&0\\
0&0&0&0&\ddots&\ddots&\ddots&0\\
0&0&0&0&\cdots&b_{n-2}&a_{n-1}&b_{n-1}\\
0&0&0&0&\cdots&0&b_{n-1}&a_n
\end{bmatrix}
$$

Such that $b_i$s are nonzero and $a_i$s may or may not be zero. An IEP about this matrix is this:

  Let $A_i$ be $i$th leading principle submatrix of $A_n$ and let $n$ be an even number, for a given Jacobi matrix $J$ of size $n/2 \times n/2$ and list of numbers $\Lambda = \{\lambda_1, \cdots, \lambda_n\}$, find an $n \times n$ Jacobi matrix $A_n$ such that $J$ is its minor principle submatrix and $\Lambda$ is its eigenvalues.

or

  For a given list of real numbers $\Lambda = \{\lambda_1, \cdots, \lambda_n \}$ and $\mu =\{ \mu_1, \cdots, \mu_{n-1} \}$, find a Jacobi matrix $A_n$ such that $\Lambda$ is its eigenvalues and $\mu$ is eigenvalues of $A_{n-1}$.

Many different problems are considered by researchers in many papers.

Because graphs are appropriate tools for presenting a matrix structure, many papers concern IEP of graphs. For a given symmetric matrix $A_{n \times n}$, graph of $A$ is a graph $G=(V,E)$ such that $V = \{v_1, \cdots,v_n\}$ and edge $\{v_i,v_j\} \in E$ if entry $[A]_{ij} \neq 0$. In many papers IEP of matrix of graphs (path and broom graph (path graph is actually a symmetric Jacobi matrix), star graph, four different IEPs for paw graph and etc.) are investigated by researchers. Please note that it is also possible to consider IEP of a directed graph, in this case its matrix will not be symmetric anymore.

What I am looking for ...

After a few years of studying IEPs in pure mathematics, I am looking for inverse eigenvalue problems with real practical application. many times, problems are modeled as a matrix and the limits on the problem are moved to the matrix entries or its spectral information and then researchers study the matrix. For example IEP of mass spring system is investigated which is a topic in physics.

IEP of problems in Computational Chemistry are rarely (or even never) investigated and because many entities and molecules in chemistry are look like some graphs (path or cycle), and graphs can also be modeled as a matrix, hence different types of IEPs may happen there. I ask for any help to introduce some field of studies or references or even cooperation to help me in doing this.

Thanks in advance.


texts: Why are oxime geometrical isomers stable?

texts:
231st page of Clayden OC 2nd edition:

  Unlike the geometrical isomers of alkenes, however, those of an imine
  usually interconvert quite rapidly at room temperature. The
  geometrical isomers of oximes on the other hand are stable and can
  even be separated.

Why are oxime geometrical isomers much more stable than the geometrical isomers of immines?


texts: Covalency in bonding across the periodic table

texts:
Bonding between main group elements is obviously almost entirely covalent and it is often easy to see these covalent bonds as 2c-2e bonds localised between two atoms. The bonding in borane, boron clusters and hypervalent compounds like SF6 introduce a more delocalised view of covalency as the bonding can be rationalised in an MO diagram. Nevertheless, covalent bonding can still be thought of as electrons occupying a molecular orbital which forms when orbitals from two or more atoms overlap (this orbital mixing requires good energy, size and symmetry match).
However, I find it hard to rationalise covalency and trends in it when considering other compounds and I was wondering if there is a good, simple(ish) way of rationalising (even if not predicting) the presence of covalency in other compounds.
People say if you have a polarising cation and a polarisable anion like in AgCl for example, you get covalency. I suppose this also makes sense because that's essentially saying that the atomic orbitals need to be of a similar energy to mix. However I am going to run through three examples that I struggle to rationalise or have questions regarding it.
MeLi
Li is clearly quite polarising (high charge density) and must therefore polarise C and there is some overlap of orbitals = COVALENCY. However, it is tetrameric in solution. Now compare it to MeMgBr; this is monomeric in solution (and in organic chemistry is softer) indicating more covalency - makes sense because of the increased polarisability of Mg relative to Li. However, is the tetramer vs monomer as a result of the difference in covalency, if so why? Is it fair to say that moving towards a more monomeric molecular structure is indicative of covalency (eg BeCl2 - chain vs MgCl2 - layered lattice vs CaCl2 - rutile)?
Suboxide
Group 1 suboxides are possible (eg Rb9O2) when Rb is exposed to limited oxygen. This forms a cluster with delocalised electrons. It seems bizarre to me because this is one of the least polarising cations going - there are no suboxides higher up the group despite it being easier to oxidise these metals lower down the group. The only vaguely analogous example is the FeS clusters seen in biology with highly delocalised electrons but the electronegativities make more sense here.
Zn
Zn is a soft Lewis acid. Why? It easily loses two electrons and then is left with a filled 3d shell. Surely that would mean it is disinclined to covalently bond and should be relatively similar to Ca?


texts: Why is sodium acetate a good nucleophile?

texts:
As $\ce{CH3COONa}$ is bulky, I thought that $\ce{CH3COONa}$ is a weak nucleophile.
But I found out that it's a nucleophile good enough to perform $\mathrm{S_N2}$ reaction on a secondary carbon.

Why is it so?


texts:
What are weak acids? My chemistry and biology classes skimmed over them briefly but nothing in depth. I understand that an acid is weak if it partially dissociates and breaks down into ionic compounds, but they never stated why.

So my question is why do weak acids break down in water? Do strong acids dissociate at all? What if they were in a different solution (or do they just stay themselves all the time?)


texts: I have found Wurtz reaction for primary alkyl halide in my textbook. My textbook also says that only primary and secondary alkyl halide shows Wurtz reaction and tertiary alkyl halides doesn't show Wurtz reaction. I tried to write the Wurtz reaction for secondary alkyl halide which is not included in my textbook. I think the product is quaternary alkane. But I faced a problem. It is: Which type of quaternary alkane is produced in this reaction? Vicinal or Geminal? Please help me in this context.


texts: Why does Vapor Pressure decrease on addition of solute?

texts:
Consider a vessel with a volatile liquid in it. Let's say it has a vapor pressure $P^0$ when it is pure.
Now a non-volatile solute is added to it. Its vapor pressure decreases as $P^0\chi_{solvent}$.
Why does this happen at a molecular level?

The reason that I have come across says that less surface area is available for evaporation and hence this effect. But this does not make sense to me as we can have liquid in container of all shapes and sizes and will still get the same Vapor Pressure.

Some users have suggested me a link to a similar question. The answers in the link are remarkable but the explanation I was hoping for was more likely to involve forces (as in Physics) and maybe a sort of "free body diagram" explaining how these forces are acting(words rather than actual diagram will be fine too) rather than thermodynamic picture.


texts:
In the calculation for equilibrium constant, we take the active mass of solids and liquids as unity. Intuition tells that more amount of a solid reactant should result in more product being formed, but according to the formula for the equilibrium constant it has no role in determining that.
Is it unity in all possible cases? How can we assume it to be one and have it not affect the equilibrium calculation?


texts: I have heard of how zinc is used to prevent corrosion of iron. So why not use aluminium coat instead? After all Aluminum oxide forms a stable coat over the surface.


texts: A theoretical framework for the formalization of chemical interaction and configuration based properties

texts:
Is there an attempt in any area of chemistry to formalize the way a molecule's properties change based on its configuration and the resulting changes in interaction with other molecules. For example, exchanging an ethyl for methyl group and vice versa.

What I am thinking of is analogous to the pursuit of a ToE(theory of everything) in theoretical physics. If any research like this is occurring or even being conjectured on, what is its current state?


texts: Mixing a Tagged Sample of Lead Iodide with another Iodide Salt

texts:
A sample of sparingly soluble $\ce{PbI_2{(s)}}$ containing radioactive $\ce{^{133}I}$ is added to 0.10 M $\ce{KI_{(aq)}}$ and stirred overnight, what happens?

I The radioactivity of the liquid phase increases  significantly.

II The concentration of the $\ce{I^{–}}$  ion in solution increases significantly.

The answer is I. I thought II would be true because some of the water evaporates, but I guess not to a "significant" extent. So that marks II off, and leaves II. I'm fairly new to nuclear chem so I don't know much about how/why radioactivity increases, could someone please explain this to me? How could radioactivity "increase?"


texts: Why are Andrews' isotherms divided into three fragments at low temperature and low pressure?

texts:
In college, I studied that for an ideal gas $PV = nRT$ , that is, at constant temperature and constant number of moles, $P \propto \frac {1}{V}$. Thus, graph between $P$ and $V$ is a rectangular hyperbola when $dT =0$ and $dn=0$. But in my textbook there is this topic called 'Andrews' isotherms' wherein they have given some $P$ vs $V$ curves for gases and at low temperatures and low pressures the graphs seem to be divided into three fragments. How is this possible? Shouldn't the curve be a rectangular hyperbola? How is it possible? Shouldn't ideal gases obey $PV = constant $ at all temperatures and pressure. That is literally the definition of ideal gas : A gas that obeys ideal gas equation at all temperatures and pressure.
I also studied that real gases show deviation from ideal gases. But when we draw $P$ vs $V$ curves of a real gas, they deviate from the $P$ vs $V$ curves of ideal gases slightly at high pressures and low temperatures. They almost remain rectagular hyperbolas. But the $P$ vs $V$ curves of real gases don't literally break into three fragements like Andrews' isotherms. The curves in Andrews' isotherms don't even come close to rectangular hyperbolas. What type of curve is being shown in Andrews' isotherms? How are these curves disobeying Boyle's law to such a great extent, not even coming close to a rectangular hyperbola?


texts: Pressure Cooker at High Altitudes and Low Altitudes

texts:
I just have a doubt if I'm right or wrong about this. Please explain more if possible.
Also, I have some questions regarding boiling point and vapour pressure.

 High Altitude Cooking
At high altitudes, the atmospheric pressure is lower than that at sea level, so the boiling point at high altitudes is quite low, which means water boils very fast and at low temperatures. The food inside it does not get enough heat to get cooked and thus food is difficult to cook at high altitudes.
Using a pressure cooker at such conditions helps increase the boiling time as the pressure inside the pressure cooker increases due to the vapour produced inside it. The boiling point increases and thus the time taken to reach the temperature increase and the cooking is better because the food is getting heat for a long period of time.

At Low Altitudes
The boiling point of liquid at low altitudes is more than that at high altitudes, so we do not have to worry much about less time being available for cooking the food. In fact, we try to decrease the cooking time in order to get food cooked faster. Even less amount of water can produce a good vapour pressure and get equal to the pressure produced inside the cooker. But less amount of water takes a lesser time to reach a particular temperature than more amount of water ( as $Q=mc{\delta}t$ ) and thus lesser the mass, lesser the time  to get the required heat, hence faster the cooking.

Questions
1. Have I understood this perfectly or is there something more to it?
2. Does the vapour pressure of the water inside the cooker have to become       equal to the vapour pressure produced due to itself in order to boil?
3. How does pressure cooker increase time for cooking at high altitudes and decrease time for cooking at low altitudes being basically the same thing?
4. The Critical temperature is the temperature at which gas just becomes liquid. The boiling point is the temperature at which all the bulk of the liquid starts turning into gas. How are Critical and Boiling Points different? How are they similar?Is there any mathematical relation between them?


texts:
I found somewhere in this site that question The reason behind the steep rise in pH in the acid base titration curve

when I tried to follow accepted answer, at some point I got stuck.

Answer says, that steep rise in PH must happen when d/dV([H+])( V is volume of added base in this case) is maximum. I disagree. It also depends on current [H+] concentration; maybe at some point d[H+]=1, and at another d[H+]=2, but if [H+]=0.1 in first case and [H+]=3 in second, then d/dV(pH) will be maximum in first case.
He differentiates this :

and gets this :

I tried to solve, but got different results.So, if I'm correct, can you give me mathematical proof why d/dV(pH) is maximum at equivalence point ?


texts: Why does [Co(NO2)6]4- ion have 3 unpaired electron as opposed to 1?

texts:
Why does $\ce{[Co(NO2)6]^4-}$ ion have 3 unpaired electron as opposed to 1?

The book says that it has 3 unpaired electrons. I thought $\ce{NO2-}$ was a strong field ligand, making $\ce{Co^2+}$ a $\ce{d^7}$ low spin ion. Six electrons go in the $\mathrm{t_{2g}}$ orbital and 1 in the $\mathrm{e_g}$ orbital.

Please explain the bonding in this compound (preferably with a suitable MO diagram to go with it).


texts: Can some one please explain alkyl shifts for me

texts:
Provide a mechanism for the following reaction. Include all intermediates, resonance structures, charges, and electron pushing arrows to obtain full credit.

I’m stuck with this problem. I got as far as step 2 of the mechanism. I know the double bond acts as a nucleophile and attacks one of the hydrogen on sulfuric acid thus creating its conjugated base $\ce{HSO4-}$ leaving a carbocation on carbon 1.
In previous problems I have done the carbocation will rearrange to form a more stable cation. I’m told it’s done by either a hydride shift (which I understand) or an alkyl shift. I’m having a hard time grasping the concept of a six-membered ring going into a five-membered ring. And essentially understanding why there is a shift.


texts:
In my class notes regarding the rigid rotor model, J is described as simply the angular momentum (replacing roe or p) and is also referred to as the angular momentum quantum number.

Are these two thing synonymous? If so in what way? If not, what do each mean and when is it appropriate to use which one?


texts:
I'm curious as to the role of molecular oxygen in Suzuki homocoupling reactions, as discussed here.

In a standard Suzuki cross-coupling reaction, molecular oxygen is not required. However, this paper claims that the homocoupling reaction will not proceed in an Argon environment. Is there a (relatively) straight forward justification for this that I am missing?

This is the reaction mechanism from the paper:


texts:
Suppose I have an aqueous solution (1) of $\ce{CH3COOH}$. The chemical species in the solution will be $\ce{H2O, H3O+, CH3COO-}$ and, since it's a weak acid, some $\ce{CH3COOH}$ will remain.

Suppose I have another solution (2) containing initially water and $\ce{HCl}$. The chemical species in the solution will be $\ce{H2O, H3O+}$ and $\ce{Cl-}$ since it's a strong acid. Suppose the initial quantity of $\ce{HCl}$ was calculated so that the obtained concentration of $\ce{H3O+}$ in solution (2) is the same than in solution (1). But in solution (1), in addition to the $\ce{H3O+}$ ions, we have some molecules of another acid, the remaining $\ce{CH3COOH}$. Then the $\mathrm{pH} = - \log [\ce{H3O+}]$ is the same for (1) and (2), while (1) contains more "acidic" molecules.

How is pH a measure of acidity then ? It seems to me that if for practical purposes I had to use one of these solutions and wanted to avoid protons being exchanged, I would not consider these two solutions equally.


texts: How to test for presence of Tobacco/nicotine in a product?

texts:
I found this paper that says nicotine was found in major toothpaste brands in India. Rather than playing blame game, wouldn't it be easier to test ourselves ?

How to test for presence of Tobacco/nicotine in a product ?


texts: How many hydrogen atoms are in a sample of NH3?

texts:
How many hydrogen atoms are contained in 8.66 moles of $\ce{NH3}$?
The answer is given after the log has been taken, so the final answer is 25.19.

What I have been doing is multiplying $8.66\text{ by }6.02\times10^{23}=5.21332\times10^{24}$ and when I take the log of that I get 24.71. I'm not sure what to do to get the correct answer.


texts: How would you know if ... is H-bond or permanent dipole or induced dipole?

texts: For example like HCl, why isn't it a hydrogen bond?


texts: Coupling constant in 1H NMR with phosphorus

texts: I observed a doublet with peaks at 5.6336 and 5.5886 ppm with the NMR instrument running at 300 MHz, and got a $J_\ce{PH}= \pu{13.5 Hz}$. Is this correct for this molecule (ethoxycarbonylmethyl(triphenyl)phosphonium bromide)? This value is larger than the hydrogen coupling constants for the C-C bonds. Is this larger coupling constant a consequence of the phosphorous?


texts: What is the magnetic moment of potassium hexacyanochromate(II)?

texts:
I calculated the magnetic moment of $\ce{K4[Cr(CN)6]}$? in the following way:

$\ce{Cr^{+2}}$ has $4$ d electrons. And since $\ce{CN-}$ is a strong field ligand, the electrons will pair up in the $\mathrm{t_{2g}}$. The electronic configuration would be $\mathrm{t_{2g}^4}\;\mathrm{e_g^0}$. Or more specifically, $\mathrm{d}_x^2\; \mathrm{d}_y^1\; \mathrm{d}_z^1\; \mathrm{d}_{z^2}^0\; \mathrm{d}_{x^2-y^2}^0$.
The magnetic moment will be a contribution of both orbital and spin magnetic moments.
$$\mu = \root\of {n(n+2)+L(L+1)},$$
where $n$ will be $2$ as the unpaired electrons are $2$.
$L$ will be $2\times 2 + 1\times 1 +0\times 1 = 5$ corresponding to $\Sigma m_l$.

Solving I get $\mu = 3.74$. But the experimental value is $3.2$.

Why is there this deviation?


texts: Products of the o-Toluidine oxidation with glucose oxidase and peroxidase

texts:
Could anybody describe which product is formed in the following reaction (o-Toluidine oxidation)?

$$\ce{H2O2 + o-Toluidine_{uncolored} - Peroxidase -> H2O + 1/2 O2 + o-Toluidine\; Oxidate_{colored}} $$

Note: Hydrogen peroxide is one of the products of glucose oxidation to glucolactone by glucose oxydase.


texts:
I am considering labware options to handle NaOH solutions at ~150 °C. One appealing idea would be to coat my current glassware with gold. I've read different sources mentioning the possibility without further detail.
The most detailed description of a process for this is INSTRUCTIONS FOR GOLD PLATING ON GLASS by Peacock Laboratories, Inc who sells (or used to sell) products for doing so. Unfortunately, this says little as to the chemical mechanisms involved.
Would anyone guess what chemicals are being used in this process and know how to explain the mechanisms at hand, and perhaps describe properties to expect from the result?
Can I expect impermeability from the coating or at least a significantly reduced glass surface exposure to hydroxides? What is the best resistance to expect vs routine cleaning of glassware that would be coated with such a method? Can I expect it to not dissociate upon heat shocks that borosilicate glass can handle? Would there be any chemicals to avoid with such a coating, other than the few that would be expected to react with / dissolve gold metal?


texts: Why was the Deville process of Alumina production given up in favor of the Bayer process?

texts: I guess this is a sort of historical question. The DeVille process seems fairly simple. Does anybody know the history or practical reasons for the switch?


texts: I'm a layman, but I'd like to know to to use GAMESS for some specific tasks

texts:
I have Avogadro and GAMESS. I modeled the sulfuric acid molecule using Avogadro, then I asked it to generate an input for GAMMES to calculate the transitional state (I'm hoping this will get me somehow closer to my computational modeling of real chemistry). But GAMESS says the job finished with an error, and I don't know why.

It's worth noticing Avogadro seems to spell one of the commands wrong, and I have to manually correct it. Avogadro issues the command \$STATTP but GAMESS does not recognize this command, so I change it to \$STSTEP, and it ends with an error, and I try the other keyword possible \$STPT and I also get an error. Here's my 2 inputs and outputs:

http://pastebin.com/TabWC9wr

This is what happens when I do what you told me, @Mitradip Das:

INPUT

!   File created by the GAMESS Input Deck Generator Plugin for Avogadro
 $BASIS GBASIS=STO NGAUSS=3 $END
 $CONTRL SCFTYP=RHF RUNTYP=SADPOINT $END
 $STATPT OPTTOL=0,0001 NSTEP=20 $END

 $DATA
Title
C1
S    16.0    -3.61564     3.32108     0.04978
O     8.0    -4.51377     4.03518    -0.82228
O     8.0    -2.75016     3.96121     1.00661
O     8.0    -2.67033     2.39549    -0.85711
O     8.0    -4.49699     2.21900     0.81326
H     1.0    -5.20320     1.93219     0.19859
H     1.0    -1.81232     2.32072    -0.38885
 $END

OUTPUT (showing only the error part, full output can be viewed here (http://pastebin.com/HRh1fS4d)

 CONSTANT LIST TOO LONG
 **** ERROR READING INPUT GROUP $STATPT   *****
 THE PROBLEM IS WITH THIS INPUT LINE, NEAR THE X MARKER
 $STATPT OPTTOL=0,0001 NSTEP=20 $END
                       X
 THE ONLY KEYWORDS ACCEPTED IN THIS GROUP ARE:
  METHOD    UPHESS    NSTEP     NNEG      IFOLOW    DXMAX
  RMIN      RMAX      RLIM      RESTAR    HESS      OPTTOL
  IHREP     HSSEND    IFREEZ    NPRT      NPUN      PURIFY
  ITBMAT    MOVIE     TRUPD     TRMAX     TRMIN     STPT
  STSTEP    PROJCT    IFCART    NPRTHS    KDIAGH    IACTAT
  IHMCON    FHMCON    SHMCON
 TROUBLE INTERPRETING $STATPT
 OBTAINING INITIAL HESSIAN, HESS=READ
 ***** ERROR, YOU DID NOT SUPPLY A $HESS GROUP.
 EXECUTION OF GAMESS TERMINATED -ABNORMALLY- AT Wed Jul 27 12:23:49 2016
                   580000  WORDS OF DYNAMIC MEMORY USED
 STEP CPU TIME =     0.00 TOTAL CPU TIME =        0.0 (    0.0 MIN)
 TOTAL WALL CLOCK TIME=        0.0 SECONDS, CPU UTILIZATION IS 100.01%

job aborted:


texts: What is the substance in the new water cooler filter that give bubbles and taste a bit like soap

texts:
Recently the water cooler was replace with a new filter.

However, when I refill my water kettle with the water from the water cooler, there are many bubbles and the taste was a bit like soap.

What chemical cause such effects? (Is it related to the new filter?)


texts: Are there any poisons with an activation threshold?

texts: Are there any poisons that lay dormant unless a significant quantity of one has been added, i.e. poison X might as well be water in concentrations less than 5M, but at 6M, all of a sudden a threshold has been reached and the poison has activated.


texts: I read somewhere that the temperature of an atom is not defined. The definition of temperature is only for larger systems. Why is this so?


texts: Are primitive GTOs normalised before contraction, or is the resultant basis function normalised afterwards?

texts:
I'm quite curious about this:

In a basis set (I'll just use minimal-basis STO-nG basis sets for convenience), the basis functions are written as a linear combination of primitive GTOs. Are the GTOs normalised first, like this:

$$\Psi^\mathrm{STO} = \sum_i N_i c_i \phi_i^\mathrm{GTO}$$

where $\phi_i^\mathrm{GTO}$ are un-normalised GTO functions, and $N_i^{2} \left<\phi_i\left|\phi_i\right.\right> = 1$

or are they normalised like this (GTOs are not normalised):

$$\Psi^\mathrm{STO} = N_\mathrm{STO} \sum_i c_i \phi_i^\mathrm{GTO}$$

where $N_\mathrm{STO}^{2} \left<\Psi^\mathrm{STO}\left|\Psi^\mathrm{STO}\right.\right> = 1$?

I thought it was the former and not the latter, but after poking around the internet I'm not so sure anymore.


texts: Does the electron in a neutral hydrogen atom ever exist in the p, d or f sublevels?

texts:
I learned that the electron in a neutral hydrogen atom can be excited to higher levels. But there are different sublevels in the levels. For example s, p, d and f.
Does the electron only jump from s sublevel to s sublevel or can it jump to a p sublevel ?
I also learned that an electron always fills the sublevels in order. Does this mean that an electron in a neutral hydrogen atom can only exists in s sublevels ?


texts:
A stability model premised on Lewis acid-base covalent bonding can be proposed to rationalize the stability shown by sulfides such as CuS and Ag2S. For instance, although the oxide anion is a stronger Bronsted base than sulfide anion, sulfide anion can be (and usually is) a stronger Lewis base than oxide anion since S has a lower EN than O. Furthermore, recall that Lewis base strength depends on the Lewis acid with which the Lewis base interacts. For the sulfide anion, since sulfide anion possess empty valence 3d orbitals, Lewis acid-base interactions are often very strong if the Lewis acid is a low oxidation state metal ion with a fairly large number of valence d electrons. for such cases, sulfide-to-cation sigma coordinate covalent bond formation couples with pi-type coordinate covalent bond formation because metal ion d-electron density "drifts" back to empty valence 3d orbitals on sulfide anion. This results in covalent bond interactions that have substantial, strong multiple ond character and formation of a metal-sulfide lattice which is rather macromolecular in character. In sum, such as lattice must be very stable ...

1) Is the above excerpt describing pi-backbonding?

2) Is pi-backbonding more favorable for metals in a low rather than a high oxidation state because such metals still have substantial electron density that needs to be stabilized - and preferably stabilized by something more electronegative than a metal?

3) Metal d-orbitals overlap with p or d-orbitals of the non-metal. How does this work? I always see diagrams such as these:

Is the overlap between the metal d-orbital and non-metal p-orbital as poor as depicted? Are the d-orbitals really at a 45 degree angle relative to the p-orbital?

4) How well is the above excerpt written? I feel that two improvements could be made:

A) The passage seems to imply that Bronsted acidity and basicity do not depend on the corresponding base or acid. Wrong implication. HCl in HBr solvent won't be a strong acid.

B) Why electron density might just "drift" to the non-metal could be explained explicitly. I.e. electronegativity.


texts: How does the atomic structure of crystals determines its shapes?

texts: for example, table salt has an a cubic structure in the atomic level, and they are often cube like in the visible level. I don't see any reason that the atomic crystal structure should reflect the crystal's shape. Can someone explain this to me.


texts: Is Octet Expansion appropriate when regular Octet bonding is possible (such as using dative bonds)?

texts: I was taught to use Occam's razor whenever in doubt over an octet expansion, being told it never happened when, for example, dative bonds could resolve the issue with a regular octet. This seems to fit what users here say about the recent paradigm shift on "hypervalent" molecules that "it is now known, that for almost all molecules that were described this way the contribution of d orbitals is negligible (<1%).", but could anyone explain exactly why an element wouldn't expand it's octet unless it absolutely has to? What advantage is there to not involving 'd' orbitals over involving them in bonding? Or is it just Occam's razor and I'm misunderstanding this maxim.


texts: Why do octahedral metal ligand complexes have greater splitting than tetrahedral complexes?

texts: Octahedral complexes have greater splitting in the d orbitals. Is it because octahedral complexes have more atoms and thus more interactions?


texts: Where will a H+ attack on 6-hydroxyhexan-2-one? Protonation can take place either on the ketone or the alcohol. So where will it attack? In short, on which of the two oxygen atoms is electron density higher?


texts: What is change in internal energy of a system in which combustion occurs at constant temperature?

texts:
We got a question in a test, in which we were asked which system has zero change in internal energy and it had an option which was combustion of methane at constant temperature. I imagined this to be a situation in which the combustion is carried out in a system, where the change in internal energy of system due to heat released, is cancelled by the work done by the system. The reason why I thought of this is because of the formula,
∆U=nCv∆T,
But this was wrong. When I asked my sir how this was wrong, he was not able to say why the ans using above stated formula is wrong. He tried giving me a logical explanation in which he said that a small part of the system releases heat which is used by the remaining part for it's combustion, thus the total temperature remains constant. but I am unable to understand why we choose to only study a part of the system while we have the entire system. It makes no sense to me. Could someone please explain how my sir's explanation is valid here and why the formula is wrong to use here?


texts: Amplitudes and phases of transform of an image

texts:
I have recorded an image of a large macromolecule and after several types of image analysis, have obtained a rotationally averaged image, that is not quite perfect, but appears to show 6-fold symmetry. With the origin on the axis of rotation, I compute a transform and unlike most of my colleagues, if I actually look at the amplitudes and phases of the transform. I have only one image of this molecule and no more specimen left. So my questions are:

What feature(s) I should see in the transform’s amplitudes and phases?
If the amplitudes and phases do not conform exactly to my expectations, what would that mean?
What are the factors that degrade my image?
What should I do to make the transform conform to my expectations?

Any ideas are welcome. Thanks in advance!


texts: Radiofrequency transmitter in an NMR experiment: Is there an involvement of (electromagnetic) radio wave?

texts:
A student in Chemistry StackExchange asked the effect of radio waves on matter, which led to an interesting set of arguments by some users. It was pointed out that in a proton nuclear magnetic resonance (or any other nuclei for that matter), there is no absorption of the photon corresponding to the radio waves. The following reference was cited NMR signal reception: Virtual photons and coherent spontaneous emission which says (in the abstract)

  In portions of the magnetic resonance community, there is a misunderstanding of the process of nuclear magnetic resonance (NMR) signal generation and reception, and even in accepted texts, it is frequently described in terms of absorption and emission of radio waves, or radiation, by a two‐level quantum system. While this explanation can be refuted, for those who do understand that the NMR free induction decay signal is easily explained by Faraday's law of induction, reconciling the presence of an induced electromotive force with an apparent absence of transitions between nuclear energy levels causes conceptual problems.

I had never heard of emission of (electromagnetic radio waves) by the precessing nuclei in an NMR experiment, but a Google search of NMR + "absorption of radio waves" shows the concept of radio wave absorption is very common.

This leads to my main question: What does the RF transmitter do in the NMR experiment and what is practically happening in the RF coil?

(a) My understanding was that the RF transmitter, emits (electromagnetic) radio waves. If the RF coil is being energized with AC current of MHz frequencies, isn't the coil emitting electromagnetic radiation in MHz range? The magnetic field component of the radio waves interacts with the nuclei magnetic dipole.

(b) Another user stated "The "transmitter" powers the pulsed radio frequency B1 field. It never decouples from the probe coil to become electromagnetic radiation, i.e. actual photons. " Although this word "decouple" is more of a play of words, can an isolated oscillating B exist without a corresponding oscillating electric field?

I thought to learn from physical chemists and engineers who will have a better picture of the RF transmitters used in the NMR than us analytical chemists. My key question is related the Rf transmitter, not FID.

Thanks.


texts: Why are hydrocarbon flames yellow or blue?

texts:
A candle gives a yellow flame while kerosene gives a blue flame on burning.
Now, saturated hydrocarbons give a blue flame but unsaturated ones give a yellow flame. I want to know why the colour of the flame is yellow and blue respectively?


texts: Radioactive Isotopes form Compounds? The Hershey-Chase Experiment

texts:
Our chemistry teacher taught us last year, that radioactive isotopes of elements don't form compounds with other elements "because they're unstable" and since we're high-schoolers (I'm assuming that's why) she didn't go into details.

But today in our Biology class, we were taught about the Hershey-Chase experiment (https://en.wikipedia.org/wiki/Hershey%E2%80%93Chase_experiment) , where we come across radioactive P-32 being incorporated into the phosphate group of nucleic acids and radioactive S-35 being incorporated into amino acids in proteins.

When we reached that bit, what our Chem. teacher said came back to me and it conflicted with the idea being propounded in class. Naturally I raised that issue with our Bio teacher, but she said she wasn't sure about' radioactive isotopes not forming chemical bonds', because that was precisely what was happening in the Hershey-Chase experiment.

So can anyone tell me whether:

a) My Chem. teacher was correct (perhaps within limits), and that the incorporation of radioactive isotopes in nucleic acids and proteins is a phenomenon that occurs outside of the limiting case she mentioned.

b) My Bio. teacher was right. Radioactive isotopes do form compounds.

c) None of the above (could you specify why?)


texts: Does lowering temperature of a gas make it easier to compress?

texts:
My teacher said that for ideal gases,

  the lower the temperature, the lower the kinetic energy of a gas will be, and it will be easier to compress the gas.

Using the ideal gas equation $PV=nRT$, if the volume is constant, a decrease in temperature will cause a decrease in the pressure of the gas. That will make it easier to compress. Will the volume remain constant, or will it change?


texts: How or Why does diesel/kerosene have a much higher 'flash point' but lower auto/self-ignition point than gasoline/petrol?

texts: This is a very common question, but I have yet to find a good theoretical answer to both questions (diesel has higher flash point BUT lower spontaneous ignition temp.)


texts:
Which of the following is the most basic compound?

$\ce{HS-}$
$\ce{H3Si-}$
$\ce{H2P-}$
$\ce{Br-}$

I can't figure out which of these is the strongest base. Would it be $\ce{H3Si-}$, since $\ce{Si}$ is the least electronegative of all these central elements?


texts:
I am well aware that the following compound is non-planar and hence, will not be anti-aromatic but non-aromatic.
But I wonder whether resonance will occur to some extent i.e. whether any three consecutive parallel p orbitals will lie in the same plane or not?


texts: Decomposition of phosphine solution in water when exposed to sunlight

texts:
Quoting from my chemistry textbook:

  The solution of phosphine in water decomposes in presence of light giving red phosphorus and hydrogen gas.

I could not find any relevant details on the Internet. I wish to know the reactions behind it, and some similar examples, if any.


texts: Is +6 really the most stable form of sulfur?

texts:
I think everyone might be aware that +6 is considered the most stable form of sulfur. But I think why this reaction happens very slowly and at such a high temperature and even the help of a catalyst is required, but in almost all redox reactions sulfur goes to +6:

(controversial where +6 is forms very forcefully):
$$\ce{SO2 +O2->[\ce{Pt/V2O5}][\text{high temp.}]SO3}$$
And also does it reduces easily (controversial where +6 is reduced easily):
$$\ce{P +SO3->P4O10 +SO2}$$
The reactions in my favour are(where stable +6 is formed):
$$\ce{SO2 +Cr2O7^2- ->SO4^2- +Cr^3+}$$
$$\ce{BaSO3- ->[\text{warming/$\ce{Br2-}$water}][\ce{/HNO3/H2O2/$\text{dil.}$HCl}]BaSO4 }$$
$$\ce{[AgSO3]- ->[\text{boil}]Ag + SO4^2- +SO2}$$
$$\ce{Ag2SO3+H2O ->Ag + SO4^2- +H+}$$
$$\ce{SO3^2- +MnO4- ->Mn^2+ +SO4^2- }$$
$$\ce{PbSO3->[\text{boil}]PbSO4}$$
$$\ce{S +HNO3->[\text{boil}]SO4^2-}$$
etc.


texts: Why do only certain acids disassociate in water?

texts:
I understand that most acids are weak acids, i.e. they do not fully disassociate in solution. However, certain acids, such as $\ce{H2SO4}$, do. I have been unable to find out what the defining characteristic is that differentiates strong acids from weak ones.

For example, HCl is strong, yet both HF and HBr are weak (even though they're based on halogens as well). Shouldn't HF be even stronger?

What characteristic makes only a select few acids fully disassociate (and hence belong to the strong acid group)?


texts: Influence of vapor pressure on surface tension

texts:
How does a liquid's vapour pressure affect its surface tension?

i.e. to say, if a liquid's vapour pressure increases, will the surface tension increase or decrease?

The SERP for this question yields only research papers to which I don't have access. This theory isn't given in my textbook either.


texts: A useful way to reuse non-recyclable plastics: Turn them to petrochemicals, shall we?

texts:
I read here (https://chemistry.stackexchange.com/a/34016/101483) that strongly acidic catalysts can facilitate dimerization of alkene. With catalysts on zeolite to allow only the isooctane (octane rating 100) to come out as the only product, can non-recyclable plastics be turned into useful petrochemicals.
In this particular case of isooctane, polystyrene (C8H8)n is broken down into styrene (C8H8) the monomer. Styrene is hydrogenated into octenes (C8H16). The hydrogenation on octenes at the crucial third stage with strongly acidic catalysts on zeolite only yields isooctane.
Is the whole process feasible?


texts: Does cellulase catalyze the hydrolysis (or break down) of soluble starch?

texts:
I’m attempting to perform an Iodometric redox titration to evaluate the vitamin c concentration in a particular solution. These solution have dissolved within them up to 2% cellulase enzyme.
In an iodometric redox titration, a 0.5% starch indicator solution would be used to inform when endpoint occurs via it’s reaction with excess, un-neutralized iodine indicator solution.
Will the cellulase in solution interfere with this titration process by perhaps hydrolyzing the starch indicator solution?
If so, should I try and denature the cellulase in solution before performing the redox titration?


texts:
I have a challenge. I recently bought a cotton/polyester coat with the intention of bleaching it to near-white. To my surprise, normal bleach with sodium hypochlorite had very little effect. It changed the color from light brown to mustard-yellow-ish, even after two soakings in a 30% mixture using water and 5% sodium hypochlorite for about 10 hours each.

My second attempt was better. I put a test piece of fabric in a solution and boiled it in the microwave. It made it even lighter, but still far away from my desired near-white (white-yellow or offwhite is what I hope to achieve).

I also tried to soak it in white spirit, with a small added extra bleaching effect.

Now, using common household chemicals, how can I achieve the desired bleaching? Can I increase the effect of the chlorine? Can I use peroxide, ammonia, or any other chemical to strip the fabric of its color? I'm willing to risk to have the fabric destroyed in the process.


texts:
A homework question I was given asked me to identify the most stable carbocation between these 4. I was able to narrow it down to either the trifluoromethylcyclohexane carbocation or the methoxycyclohexane carbocation, but I’m not sure which between the two of them.

My gut feeling is that the methoxycyclohexane is more stable because of its contributing resonance structures, but I’m not sure if that trumps the hyperconjugation that the fluorine atoms provide. Any insight would be appreciated!


texts: When a piston cylinder system that evolves isothermally and quasistatically is irreversible?

texts:
Suppose we have two states: $\ce{A}$ and $\ce{B}$.
Considering a quasi-static isothermal process of an ideal gas, (and another condition, that is $T = T_\mathrm{surr}$) that join those states.

Then the Poisson's relation $P_\ce{A}V_\ce{A} = P_\ce{B}V_\ce{B}$ is fulfilled.
that means after integrating

$$W = nRT\ln\left(\frac{V_\ce{B}}{V_\ce{A}}\right)$$

$$\mathrm{d}S_\mathrm{s} = -\mathrm{d}S_\mathrm{surr}$$

because $T = T_\mathrm{surr}$. Then

$$\mathrm{d}S_\mathrm{u} = 0.$$

So my guess is that no, that irreversibilities on those conditions come only on finite temperature difference with surroundings.

But then I remember friction. If piston with friction has $x$ joules lost by friction, how does that change everything?

I need someone to "shed light" on this issue. There is always a lot of confusion when we consider a quasi-static but irreversible process.


texts: Aromaticity of two rings connected by double bond

texts:
I want to know how to decide aromaticity of two rings connected by a double bond.
For example consider the ring in which when double bond is broken generates tropylium cation and cyclopentadienyl anion. I know that is aromatic because the ions generated are themselves aromatic.
How will the aromaticity be affected when we get an antiaromatic one?
For example consider the ring in which when we break the double bond cyclopropenyl anion is generated.
What will be the overall aromaticity of the molecule in this case.
And in general what is the rule to decide the aromaticity of the rings connected by a double bond?


texts: Effect of intramolecular hydrogen bonding on the stability of a molecule

texts:
What will be the effects of intramolecular hydrogen bonding on the stability of a molecule? Will it increase or decrease the overall stability of a molecule? Or will it not have any impact on the stability?

Why do I think intramolecular hydrogen bonding increases the stability?
I've learn that formation of a bond lowers the energy or increases the stability of a molecule. Thus, formation of intramolecular hydrogen bond makes the molecule more stable.

Why do I think intramolecular hydrogen bonding decreases the stability?
Let us consider the following molecule:

Intramolecular hydrogen bonding exists between oxygen atom of the carbonyl group and hydrogen atom of the hydroxyl group. Due to the hydrogen bond, these oxygen and hydrogen atoms are under attractive forces. I think this causes strain in the molecule, thereby increasing the energy or decreasing the stability of the molecule.

However, I don't know which of the above two arguments is correct. It would be helpful if you could explain the effects of intramolecular hydrogen bonding on the stability and the appropriate reason behind it.


texts: Bonding metal pieces using electroplating - what's the process called?

texts: So I think the title all most says it all - given say two pieces of copper can we make solid 'weld' using electroplating chemistry? If so whats the accepted terminology for this process so I can do some literature research - also am I correct in my assumption that the join would be as strong as the raw metal?


texts: mechanism in formulation of mesylates and tosylates

texts:
in these reaction(Ts and Ms), why do they proceed in different mechanism/?

more specifically,

(Ts) e- pair from O attacks S, (Ms)but not in latter reaction. why?

it makes no sense. because TsCl is more sterically hindered by benzene ring.

in Ms, e- from hydroxyl group attack H attached to methyl group instead. I'm not famillar with H that was attached to C taken by other things.
strong base can do this?

help me~


texts: How to calculate resulting pH of mixing 2 fruit juices

texts:
I want to make jelly from a mixture of 50% fresh apple juice and 50% juice of another fruit. The resulting pH must be less than 4.6, otherwise the jelly will not be safe from C. botulinum.

Based on my research, apple juice generally has a pH between 3.3 and 4.0 (Let's say 4.0 to be conservative), so it's safe for home canning. The other juice is less acidic (a pH of ~ 6.0).

I plan on mixing equal parts (by volume) of the two solutions (pH 4.0 and 6.0); I need to know if the resulting pH will be less than 4.6.

I found a claim that if you mix equal parts of 2 acids, the resulting pH will always be the lower pH plus 0.3. So if that's true, the answer to my question is 4.3 (safe from botulism, but I need to know if this claim (and my subsequent result of pH 4.3) is correct!


texts: Reactivity of Benzaldehyde between aldehydes

texts: Are Benzaldehydes less reactive than aldehydes due to the -R Effect of the -CHO group present on the benzene ring?


texts: Why is Kw the same in acid, water, and alkali? Given that Kw equals to [H+][OH-], doesn't concentration of these 2 differ in acids, water and alkali? Why is Kw only affected by temperature?


texts:
Cathodic protection prevents the removal of positive form the metal surface by applying a negative charge to the metal.

Is is possible to prevent the reaction of an active metal (i.e. sodium) with water by aggressively forcing current into the metal using a DC source? We allow the "water" to be a dilute solution (~1%) of the metal hydroxide. There is also an anode that completes the circuit but its OK if the anode disintegrates.

Edit: I will let the answer stand but it begs one question: If the power supply forces the sodium metal to be at a strongly positive potential, it may end up coated in layer(s) of hydroxide (or even oxide?), which may prevent the water from reaching it. But if the metal is liquid (NaK) then it may cause the metal to have "negative surface tension" making it impossible to maintain a high potential as the capacitance runs away to "infinity". So it's not completely settled.


texts: This isn't much of a "chemistry" question, but this is the only category where I can get answer based on science. I already tried soaking it in cooking oil, which did not work (it only made the tracing paper even more slippery.)


texts: In biochemistry, when do rate constant units matter in calculating free energy changes?

texts: In my experience, it is always been the ratio of products to reactants that mattered, so as long as your units are consistent; what they are doesn't matter. However, an in-class problem today required that the units be changed to molar (M) from millimolar (mM). Can you summarize when/why this matters in some cases, but not in others?


texts: Alternative Program for Orbital Population Analysis

texts:
Gaussian has Orbital-by-Orbital Population Analysis.

From the manual:

# UHF/6-311+G(d) Pop=Orbitals=3
Here is the resulting output from a calculation on FeO+ quartet:

Atomic contributions to Alpha molecular orbitals:
Alpha occ 16 OE=-0.923 is Fe1-d=1.00
Alpha occ 17 OE=-0.699 is O2-p=0.88
Alpha occ 18 OE=-0.690 is O2-p=0.68 Fe1-s=0.21
Alpha vir 19 OE=-0.253 is Fe1-s=0.70 Fe1-p=0.27
Alpha vir 20 OE=-0.188 is Fe1-p=0.71 O2-p=0.29
Alpha vir 21 OE=-0.133 is Fe1-p=1.04

Atomic contributions to Beta  molecular orbitals:
Beta  occ 13 OE=-0.801 is O2-p=0.79
Beta  occ 14 OE=-0.783 is Fe1-d=1.00
Beta  occ 15 OE=-0.758 is O2-p=0.89
Beta  vir 16 OE=-0.241 is Fe1-s=0.81 Fe1-p=0.17
Beta  vir 17 OE=-0.139 is Fe1-p=0.91 Fe1-d=0.14

This can be used to provide a more quantitative characterization of the nature of canonical molecular orbitals.

Due to certain restrictions on the use of Gaussian (http://www.bannedbygaussian.org/), I am unable to use Gaussian. Are there other programs that can perform such a calculation? NBO only seems to provide such a breakdown in terms of NBOs, and I can't find the feature available in any other quantum chemistry program. I realize that I can do this myself by extracting the C matrix, figuring which coefficients go with which orbital, and summing up myself. However, this would probably take me a day to program.

Note: My calculations use B3LYP, ECPs, and the COSMO solvent model. So the program would need to be able to at least produce single points with such a method.


texts: Reaction of NaOH with methanol and ethanol?

texts:
Methanol ($\ce{CH3OH}$) and ethanol ($\ce{CH3CH2OH}$) react with sodium metal ($\ce{Na}$) to form sodium methoxide ($\ce{CH3O^-Na+}$) and sodium ethoxide ($\ce{CH3CH2O^-Na+}$):

$$\ce{2CH3OH + 2Na -> 2CH3O^-Na+ + H2}$$
$$\ce{2CH3CH2OH + 2Na -> 2CH3CH2O^-Na+ + H2}$$

Do methanol and ethanol react with sodium hydroxide ($\ce{NaOH}$) in the same way as sodium do to form sodium methoxide and sodium ethoxide respectively?


texts:
I'm just wondering, if one were to run a $\ce{^{11}B}$ NMR on a boron containing sample in a borosilicate tube, how could we separate the spectra of the tube and the sample?

Apart from using a different tube - Perhaps through a pulse sequence like BIRD for $\ce{^1H/^13C}$?

Or decoupling - which I've only just started to learn about and don't really understand?


texts: When 2-pentene reacts with HBr, what will be the major product?

texts:
If we consider the first step (formation of carbocation by the attack of the proton).

A couple of textbooks I referred say that when the substituents on the $\ce{C=C}$ are different, the direction of shift of the electron is decided by the inductive effect of the substituents. For example, in this image:

$$
\begin{align}
\ce{\underset{1}{C}H3-\underset{2}{C}H=\underset{3}{C}H-\underset{4}{C}H2-\underset{5}{C}H3 &-> \underset{1}{C}H3-\underset{2}{\overset{\large\ominus}{C}}H-\underset{3}{\overset{\large\oplus}{C}}H-\underset{4}{C}H2-\underset{5}{C}H3} \label{rxn:a}\tag{a} \\
\ce{\underset{1}{C}H3-\underset{2}{C}H=\underset{3}{C}H-\underset{4}{C}H2-\underset{5}{C}H3 &-> \underset{1}{C}H3-\underset{2}{\overset{\large\oplus}{C}}H-\underset{3}{\overset{\large\ominus}{C}}H-\underset{4}{C}H2-\underset{5}{C}H3} \label{rxn:b}\tag{b}
\end{align}
$$

Assuming that a proton $\ce{H+}$ is approaching, both the textbooks say that the electronic shift happens as in the case \eqref{rxn:a} because \eqref{rxn:a} has 2 ethyl groups to stabilize the carbocation by inductive effect. But isn't hyperconjugation more important than inductive effect in determining the stability?

By hyperconjugation, case \eqref{rxn:b} should be the preferred pathway as there are 5 alpha-hydrogens (including the $\ce{H}$ that is attacking and will join at the $\ce{C-}$) and case \eqref{rxn:a} has only 4? By this logic 2-bromopentane should dominate. Am I missing anything?


texts: Rearrangements of α-aminoketones in Clemmensen reduction

texts:
What is the possible mechanism for this reaction? Activated zinc in presence of concentrated hydrochloric acid is used for Clemmensen reduction, that is conversion of ketone group to methylene group. I'd expect the product to be 1-methyl-2-propylpyrrolidine:

However, ring expansion occurs leading to a piperidine derivative. Could anyone please explain or provide a mechanism for the conversion? Thanks!


texts: How do orbitals fill, what is the difference between them, and why is this stable?

texts: I know about the Aufbau principle and the order in which electrons fill orbitals, but how is it that atoms are more stable when they have a full valence shell? It seems that any shell can be comprised of many different energy levels(3s,3p,3d,etc) and that it would be kind of arbitrary to say that "since all the orbitals that start with three are full, the atom is stable". Are all the "3" energy levels linked in a special way that differentiates them from 2 or 4? Also, why would an electron even be inclined to join a specific orbital, and do electrons change their spin in order to fit with the pre-existing particle in the orbital.


texts:
1) With $n,V$ constant, increasing $T$ results in an increase in $P$ :
$$P = k_1T$$

2) With $n,V$ constant, increasing $P$ results in an increase in $T$ :
$$T = k_2P$$

We can do the first process by simply heating the confined gas.

However I'm not able to think of a way to do the second process.
How can I make  "increasing $P$" the cause of "increasing $T$" ? (with out changing volume or adding more matter)


texts: Why is 1,3-pentadiene favored in the reaction of pent-3-en-2-ol with sulfuric acid?

texts:
Let's say we have the following reaction, a simple dehydration reaction.

Why do we get 1,3-pentadiene and not 2,3-pentadiene?


texts:
There is a statement on page 60 of this dissertation:

  the "physicist's water molecule" ($\ce{O-H = 1.1 \mathrm{\mathring{A}}, \angle HOH = 104^\circ}$)

I understand it to be a model similar to the "spherical cow in a vacuum,", in that it's meant to be an easy-to-remember approximation, but

What is the etymology of this phrase or definition?
Why this specific choice of parameters? It could just as easily be $\pu{1.0 \mathrm{\mathring{A}}}$, according to Wikipedia, and the angle could vary as well.


texts:
I'm trying to make an etching solution for copper (PCB) with easy to access materials. I'm using hydrochloric acid (9%), peroxide (common "oxygene" that contains many more ingredients), table vinegar, table sea salt, and bicarbonate soda. Now the recipe mentioned only hydrochloric acid and the peroxide, but it mentioned a hydrochloric acid with high concetrantion (31%). My solution with (the easily accessible) 9% hydrochloric acid didn't worked so I added the other elements and it worked fine. The problem is that I don't know what I'm doing, and what elements causes the reaction. I start with the hydrochloric acid, I put some peroxide inside. Alone it does nothing to the copper. I then add some vinegar, salt, and soda (I suppose soda helps to get oxygen inside the solution) and after a while the reaction starts and it works really quick. (the 5x5 cm copper piece gets dissolved as I like in around 5 minutes. (and whatever I have painted on it with my permanent marker remains).

So can someone explain me what reactions take place, and perhaps which is the crucial material and which I may omit?

Also when I work with that stuff my nose gets irritated, how harmful is this solution and how I may dispose it safely?


texts: Dihaloalkane reaction with sodamide/ammonia

texts:
In the following sequence of reactions:
$$\ce{CH3-CH2-CH2-I ->[\text{Alc.}~KOH] \textbf{A} ->[Br2] \textbf{B} ->[NaNH2/NH3] \textbf{C}}$$
the product C is:

alkene
alkanol
alkyne
alkylamine

I haven't really came across a reagent $\ce{NaNH2}/\ce{NH3}$ in my whole session. Well, I have got B which is $\ce{CH3-CH(Br)-CH2-Br}.$
Then, how do I proceed next? How will my substrate  react with that reagent and what product will I achieve?


texts: Estimation of change in enthalpy of a gas phase reaction using bond enthalpies

texts:
Estimate ∆H for the following gas phase reaction:
$$\ce{C2H4 + 3 O2 ⟶ 2 CO2 + 2H2O}$$

I have been having trouble on this problem for a long time, and I was hoping someone would help me with it. I tried using the average bond enthalpies, but that always got me the wrong answer. Below is a table of average bond enthalpies in kJ/mol.


texts: Sodium bicarbonate, varying acetic acid, measuring carbon dioxide volume, understanding results

texts:
With my 6yo daughter, I have conducted a simple experiment. We used 1/4 tsp (we don't have sub-gram scales) of bicarbonate of soda for each test. In each test, we used a different amount of vinegar (5% w/w acetic acid), topped to 120ml with water. In each test we left the reaction to (for the purposes of measurement) complete and measured the $CO_2$ volume produced. (the reaction took place in an upturned measuring cylinder).

our first hypothesis was that we would get a linear relationship up to the point that the bicarbonate of soda became the limiting reactant.
we then modified this thinking that a certain amount of $CO_2$ might get dissolved in the water so the graph line might pass below the origin.

The results we got were surprising. With each increase in vinegar, the volume of gas increased by more. See below

vinegar  |  CO2
  (ml)   |  (ml)
--------------------
   5     |  8.5
   10    |  22
   15    |  34
   20    |  110

We have repeated the measurements a few times. We have a fair amount of variability but the same pattern. (I appreciate the woolliness of this statement, more statistic next time).

I guess that the increased rate of reaction which came with increased concentration meant the $CO_2$ had less chance to dissolve. Can someone tell me what the correct explanation is?

As a bonus - is there a way to conduct this experiment in such a way that we will be better able to observe the relationships between the reactants and the product? One thought that I had was saturating the vinegar with NaCl so that it won't allow any carbon dioxide. Could this work?  Is there a better way


texts: Carbon Free energy vs Temperature Diagram

texts: I've recently read that the Carbon takes a unique position as a reducing agent , and i think it has to do with the very special form of its Ellingham diagram  , but i am still not able to make a connection , So what makes exaclty the carbon a good reducing agent ?


texts: Are all stable Xenes (graphene-like 2D honeycomb sheets) buckled?

texts:
background: Per this abstract

  Silicene, germanene and stanene are part of a monoelemental class of two-dimensional (2D) crystals termed 2D-Xenes (X = Si, Ge, Sn and so on) which, together with their ligand-functionalized derivatives referred to as Xanes, are comprised of group IVA atoms arranged in a honeycomb lattice — similar to graphene but with varying degrees of buckling.

question: This comment notes

  Graphene is not flat, either. Cannot be, because only 3D crystallites have perfect long-range order. Landau-Peierls instability this is called.

How general is this? Can we expect all stable 2D crystals to be buckled, and any that would be flat and not buckled to "self-destruct" due to instabilities related to long-range order?


texts: What is the oxidation state of carbon atoms in Ethanoic acid?

texts: The oxidation states of $sp^2$ and $sp^3$ carbon in ethanoic acid  are $-3$ if we do not consider the electronegativity difference of these two carbons due to their different  hybridisation  but this is not the case with the thiosulphuric acid ($\ce{H2S2O3}$); here the oxidation states of sulphur here are +6 and -2. So why are we considering the electronegativity difference of two $sp^3$ and $sp^2$ sulphurs here?


texts: Why is the principle of separation in GFC opposite to electrophoresis despite using same material for the gel?

texts: In GFC, larger proteins get eluted out first while in electrophoresis the larger proteins move slower. Why is this?


texts: Molar heat of combustion with different fuels

texts:
I'm not sure exactly how to attack this question, I'm sure that you have to use equations such as

$$Q=mc\,\Delta T$$
$$n=\frac{M}{m}$$

But I don't know where to use them. Any help would be appreciated

I just attempted the question, I'm not sure if this is the correct working.

Assuming 1 mol of each substance

Ethyne:
$$\begin{align}n&=\frac{M}{m}\\[6pt]
1&=\frac{26.038\ \mathrm{g/mol}}{m}\\[6pt]
m&=26.038\ \mathrm g\end{align}$$
producing 1630 kJ

Hexane:
Same working as above so:
$$m=86.178\ \mathrm g$$
producing 1300 kJ

Ethane:
$$m=30.07\ \mathrm g$$
producing 1560 kJ

Simplifying each of the mass and energy relationships for each substance gives:

Ethyne: 1 gram for 62.6 kJ

Hexane: 1 gram for 15.09 kJ

Ethane: 1 gram for 51.89 kJ

This would imply that ethyne would be the best fuel, as it uses the least amount of mass and the greatest amount of energy is produced.

Not sure if this is correct. Any tips would be great.


texts:
I was doing some practice problems when I came across this one

The answer key says the answer is B but I don't know why. Isn't the difference in the molar masses of the two substances in D greater than that in B? Or am I supposed to look for how many times greater the molar mass of one is than the other?
Thanks.


texts: Which has a higher lattice energy CaO or NaCl?

texts: I know that as charge increase the lattice energy increases as well. However when the size increases, the lattice energy decreases. Can you please explain this to me? I think it is CaO but i'm not sure. Thanks!


texts: Finding the mass of NaNO3 in original mixture from preciptate

texts:
A 1.61-g sample of a mixture of $\ce{AgNO3}$ and $\ce{NaNO3}$ is treated with excess $\ce{Na2S}\:(\mathrm{aq})$. The precipitate is filtered off, dried and weighed. The dried precipitate weighs 0.44 g. What is the percentage by mass of $\ce{NaNO3}$ in the original mixture?

I attempted this problem by using two equations: one with $\ce{AgNO3}$ and $\ce{Na2S}$, and the other with the other reactant and $\ce{Na2S}$. Then I wrote an equation in moles, using m and 1.61-m as the mass of the reactants. My answer was 2.34 g, which is greater than the original so I know I did something wrong.


texts:
I recently decided to make my own ferrofluid toy to play with.  I built a sealed enclosure at my local fablab, and the end result was perfect.  It worked just like in the videos you see online, and I couldn't have been more pleased.

But then, after a week or so, I noticed that the fluid was moving a bit more sluggishly, and not long after that, it would barely react to the magnet at all.  Now when I try to play with it, I have to press a big magnet right against the surface, and then the "fluid" moves completely uniformly -- less like a fluid and more like a big black rock.

The only thing I can think is that maybe the suspension fluid I used had a gradual drying-out effect on the ferrofluid.  When I was originally building the thing, I did some googling to find out how best to do it all, and I found an old post on this very forum, suggesting the use of isopropyl alcohol, so that's what I used.  I also used the same type of ferrofluid as the OP in that thread.

So would a different type of suspension fluid keep it from hardening like this? Or am I wrong about the cause?  The only other thing I can think of is that maybe it's because there's a little air bubble in my enclosure.  It can't be any external factors, because it's sealed completely airtight.

Any ideas?  Thanks!


texts: Radical addition and radical cleavage of cyclohexene and cyclohexane

texts:
Using reaction mechanism, why radical bromination of cyclohexene is faster than cyclohexane? Draw the stereochemistry of most stable product(s) of both cyclohexene and cyclohexane.

Here are what I get so far

I'm not sure about the kinetics of the reaction but I worry the kinetics vs thermodynamics factor (and I can't find any reaction coordinate that can show energy of possible radical position in cyclohexene and cyclohexane in one diagram).
Radical bromination of cyclohexene can undergo two competing reactions, radical addition and radical cleavage then followed by SN2 mechanism. I'm not sure if cyclohexane-bromonium ion can be formed in radical addition.
Drawing stereochemistry, should I prove it using chair conformation for both cyclohexene or cyclohexane to show the most stable product? I really don't know how to show the bromonium ion on that chair conformation and how SN2 attacks the ion (I thought it should be attack on backside but I can't prove why backside). Maybe some people will just throw "check this reference" but how I even can connect the conformation to resonance-stabilized cyclohexene product.

Can someone help me to connect the dots and what I miss from interpreting the question? Thank you.


texts:
A sample of copper(II) sulfate pentahydrate (CuSO4·5H2O) contains 0.360 g of water.
What is the total number of atoms in the compound

what's the idea of this question?

what i know is that atoms number is found by multiplying the Avogadro number by the mol's number

??


texts: Comparison between groups with -I effects

texts:
So I have a few questions in my book that require me to compare between two different groups on the basis of their -I effects. I have a few questions on this that have been bugging me for quite a while. I am preparing for an exam, and please not we will not be given any energy data or charts so we wont be able to reference them while giving the exam, so all I can do I understand.

What happens if I have to compare between a compound that has a single group with a stronger -I effect (like $\ce{NO2}$) and a compound that has more than one group with a comparatively weaker -I effect (like $\ce{Cl}$)? In which case is the -I effect stronger, and how to understand that?
What is the actual order of -I effect? Wikipedia and my books sometimes are conflicting in their orders. For example, Wikipedia states it as:

$\ce{–NH3+} > \ce{–NO2} > \ce{–SO2R} > \ce{–CN} > \ce{–SO3H} > \ce{–CHO} > \ce{–CO} > \ce{–COOH} > \ce{–COCl} > \ce{-CONH2} >\ce{-F} > \ce{–Cl} > \ce{–Br} > \ce{–I} > \ce{–OR} > \ce{-OH} > \ce{-NR2} > \ce{–NH2} > \ce{–C6H5} > \ce{–CH=CH2} > \ce{–H}$

One of my books states this as:

$\ce{-NMe3+}>\ce{-NH3+}>\ce{-NO2}>\ce{-CN}>\ce{-F}>\ce{-Cl}>\ce{-Br}>\ce{-I}>\ce{-OAr}>\ce{-COOR}>\ce{-OR}>\ce{-OH}>\ce{-C6H5}>\ce{-CH=CH2}>\ce{-H}$

And another states this as:

$\ce{-NF3+}>\ce{-NH3+}>\ce{-CF3}>\ce{-NO2}>\ce{-CN}>\ce{-SOO-OH}>\ce{-COOH}>\ce{-COCl}>\ce{-COH}>\ce{-COR}>\ce{-F}>\ce{-Cl}>\ce{-Br}>\ce{-I}>\ce{-OH}>\ce{-OC6H5}>\ce{-OR}>\ce{-NH2}>\ce{-CH=CH2}>\ce{-C6H5}>\ce{-H}$

Clearly some do not contain some compounds while in some cases the orders are a tiny bit switched up. Which one should I use? I know that some of this is really close comparisons but a definitive order if possible would reall help me out. Thanks.


texts: What is the correct IUPAC name of this compund?

texts: I thought C=C is the "functional group" here and Br is a substituent so the numbering should start from the top left C, making the name 4-Bromo-3-methylbut-2-ene, but my book says 1-Bromo-2-methylbut-2-ene. Which is correct?


texts: For example, silk is made of fibroin. But what's wool made of?


texts: Why does fulminate not minimize formal charge in its structure?

texts:
The official structure of fulminate looks like this:

from wikipedia: https://en.wikipedia.org/wiki/Fulminate

However, this structure does not minimize formal charge, since nitrogen has a formal charge of +1, while carbon has a formal charge of -1.

Instead, it would make more sense for fulminate to look like this:

In this structure, the nitrogen and carbon now both have formal charges of zero, and the number of electrons is the same as the official structure.

Carbon seems like it can exist with six electrons, as shown in https://en.wikipedia.org/wiki/Dichlorocarbene.  However, the article says that it is an intermediate.

My question is, why is the first structure of fulminate the official one and not the second one? Does the octet rule take precedence in this case?


texts:
I am curious if there is a way to dissolve or break down solidified aluminum powder. I have tried to break it apart but it is a solid chunk and I need to figure out how I can break it down to 150 pound pieces.

Can a block of hardened aluminum powder be physically or chemically broken down back to a soft form.


texts:
Although in 2020 there is a big movement of bankers marketers to lean the public towards cashless society, cash in the form of banknotes is still used in many if not most countries.

Cash banknotes can be very dirty in some occasions, especially old banknotes in humid countries and furthermore in humid storage areas.

Is the concept of a "self cleaning" banknote plausible?


texts: Why do we see complementary colors in UV/Vis Spectroscopy?

texts: From what I read, a compound that absorbs visible light will produce a complementary color (using the color wheel), that can be seen. Why is this the case? Is it because, for example, if a molecule absorbs red, for instance, all the other colors will reflect and combine (?) to give off the color green that we see? I thought if we excite an electron to its excited state, with it absorbing a certain wavelength, when it drops back down to its ground state, it will give off a photon of that same wavelength (and same color). Also, when a molecule absorbs UV radiation and reflects all of the visible wavelengths, I read that it will appear white or colorless (isn't black the absence of all colors?), is this just two ways of saying the substance appears white or does that mean that it can be white or clear?


texts:
The oxydation-reduction reaction during the discharge of a galvanic battery is: Zn + Cu2+ = Zn2+ + Cu. During the charging phase, the reaction will be in the opposite way. An external source provides electrons and energy for recharging the battery. If we consider the battery completly discharged, emf is zero. During the recharging phase, the emf will increase gradually. My question is:
Does the emf increase because the reactants of the charging phase are reappearing again during the phase of recharge? When the reactants reappear, Does the reaction during discharge happens at the same time of the recharging one? How about the charge separation on the electrodes? Do they reappear again thus creating electric field inside the battery? How about the ions inside the salt bridge, do they move in the opposite direction of the charging phase?


texts:
A somewhat infamous law (to me at least), that states:

$$a.A_{eq}=b.B_{eq}=c.C_{eq}=d.D_{eq}$$

for any and every balanced chemical equation -

$$a.A+b.B = c.C+d.D$$

where $i$ denotes the stoichiometric coefficient(/no. of moles) of the chemical species $I$ and $I_{eq}$ denotes the number of equivalents in 1 mole(/formula mass...?) of the chemical species $I$.

Am I wrong about any of the facts I've presented above? Please mention any errors you spot.

Assuming that I did fine, my simple question is,

  What's the mathematical proof for this law?

I tried surfing online, but all I came across (with my not-so-deep searches) were verbal explanations of the law.

Is there no mathematical proof to this law whatsoever? I'll be satisfied to just find a proof, even if I don't understand the complicated math going into it (for I'm an eleventh grader).

Edit to provide an example:

$$\ce{2NaOH + H2SO4  -> Na2SO4 + 2H2O}$$

For A, $a \cdot A_{eq} = 2 \ (moles) × 1 \ (equiv.\ per\ mole) = 2$

For B, $b \cdot B_{eq} = 1 \ (moles) × 2 \ (equiv.\ per\ mole) = 2$

And this follows for other species, hence showing $a.A_{eq}=b.B_{eq}=c.C_{eq}=d.D_{eq}$


texts: The acid in soft drinks dissolves your teeth. Which type of chemical could you use to stop the acid?


texts: Do all zero order reactions occur as combination of multiple elementary reactions?

texts: In a  reaction, the rate determining step (RDS) gives the order of reaction. There might be 2 or 3 molecules colliding to give a product (2nd or 3rd order) or a molecule breaks for order 1. But for zero order reactions, how do they occur? Are all zero order reactions complex (i.e. are there no simple 1 step zero order reactions )


texts: Conversion of acetaldehyde to butane-1,4-diol

texts: How to convert acetaldehyde (ethanal) to butane-1,4-diol. I just tried doing aldol, but it leaves an alkyl group at the end. Also it cannot be done by oxidizing ethane with basic permanganate.


texts: Concentration of gas above aqueous ammonia

texts:
I am a physicist who has run into some chemistry in the lab (and unfortunately, I've completely evaded any formal training in chemistry). I have exposed some samples (I think details of the sample are not important here, but would be happy to provide further information if necessary) to a solution of 30% ammonia and 70% water, and am trying to calculate approximately how much ammonia (in ppm, for example) reached my sample.

My samples are placed in an 3″×3″×1″ (L×W×H) container with the top exposed to the air. Until now, I've just been marking down the volume of the solution that I've placed (about 15 mm) directly below my samples in the container (e.g., 5 μL, 10 μL, …, 200 μL). I think it's good enough to assume room temperature and standard atmospheric pressure for my labs. I've looked into Henry's law and related relationships, but am not sure that these are the appropriate tools. I would greatly appreciate any help or guidance!

Maybe these tables will help (I've stumbled upon them trying to figure this out in the context of Henry's law):

https://www.tannerind.com/PDF/green-aqua-amm.pdf
https://www.atmos-chem-phys.net/15/4399/2015/acp-15-4399-2015.pdf

P.S.
If a closed container is a more tractable problem, I also collected some data with a closed container (same dimensions), and would very much appreciate insight into that problem too (if it is very different, or the only solvable problem). I should also mention that the solution was removed from the container in about 10 seconds in all cases (if that makes a difference).


texts: Ranking gases by value of the van der Waals equation-of-state constant 'a'?

texts:
How can I find out which gas has the highest value of the van der Waals constant $a$?

Example set of gases in ascending order of $a$: $\ce{NO2}$, $\ce{CO2}$, $\ce{H2}$, $\ce{H2O}$ and $\ce{CCl4}$.


texts: Describe the bonding in a tribromide anion, what is its structure?

texts: I'm thinking it will be linear with a negative charge on the middle bromine. Someone told me it is trigonal bipyramidal geometry with 3 lone pairs around the central bromine and the two other bromines above and below making it linear. Is this correct? Also is it just covalent bonding in the molecule?


texts: Why does this flame travel (in a circular path, multiple times)

texts:
We filled a graduated cylinder with Ever Clear and let it overflow. Then we lit the liquid on fire. To our surprise the flame started running around the base of the cylinder. Why does this happen?

http://webmshare.com/m7vb8


texts: Breaking degeneracy in phosphorus pentachloride

texts:
Recently, in a class discussion, the following point was brought up:

  Although the axial and equatorial bond lengths in $\ce {PCl5}$ are inequivalent, when we consider the time-averaged $\ce {P-Cl}$ bond length, there should only be one value sincethe molecule is symmetric and thus, all the chlorine atoms interact with the phosphorus atom to the same extent.

The idea of "time-averaged" means that we are considering the $\ce {P-Cl}$ bond over a long duration. This bond length varies over time since the atoms are constantly in motion. When this bond length is "time-averaged", it means that we are taking the average of the bond lengths measured at infinitely many instants in time.

The argument is that although at any particular instant, the molecule would adopt a configuration with axial bonds being longer than equatorial bonds, when the bonds are time-averaged, they should all be the same length.

This has caused much dispute among members of the class and it has also led me to consult a professor who is well-versed with quantum chemistry. The professor mentioned that the argument put forward is not valid because in $\ce {PCl5}$, there is a breaking of degeneracy due to perturbation. He cited the Jahn-Teller distortion as a situation similar to that in $\ce {PCl5}$, where degeneracy is broken.

I am very confused by this. What exactly is this perturbation? Why does it exist for $\ce {PCl5}$ and not for similar molecules, such as $\ce {SF6}$ (as seen in the comments for this question)?


texts: Dinitrophenyl (DNP) derivatives of amino acids (specifically epsilon-DNP-lysine)

texts:
I have a pretty basic biochemistry question but am having trouble finding the answer to it:

Normally, DNFB (dinitrofluorobenzene, or 1-fluoro-2,4-dinitrobenzene to be exact) reacts with just the amino terminus of amino acids, creating dinitrophenyl (DNP) derivatives.  However, with lysine, DNFB can react in two places (at the amino terminus and to the epsilon amino group).  The DNP derivative of lysine is referred to as "epsilon-DNP-lysine".

Does "epsilon-DNP-lysine" refer to a product where the DNP is bound only to the epsilon amino group (but not to the amino terminus), or does it refer to a product where DNP is bound simultaneously to the epsilon amino group and to the amino terminus?

Also, can the same thing happen with other amino acids that have an amino group in the side chain?  i.e. can there be epsilon-DNP-arginine, for instance, or is this behavior unique to lysine?


texts:
I don't really get the concept of index of hydrogen deficiency (IHD). Can someone please use an example to explain what $\mathrm{H_{reference}}$ and $\mathrm{H_{molecule}}$ are? I know the formula:

$$\mathrm{IHD} = \frac{\mathrm{H_{reference}} - \mathrm{H_{molecule}}}{2}$$


texts: Entropy change and heat transfer in non-ideal heat engines

texts:
Please help me, a mathematician, to make sense of entropy. I know it's a topic with about a million questions already, so I understand if this gets ignored. Yet for the life of me, I cannot make sense of the previous answers.
So apparently the definition of entropy change in a system is $\Delta S = \int_\mathrm{rev} \frac{\mathrm d Q}{T}$ and this is a state variable. I also know that for irreversible paths, you have to find a reversible one that links the same thermodynamic states to calculate the entropy. Yet in my professor's notes it says
$$ \mathrm dS = \oint \frac{\mathrm dQ}{T} < 0 \text{ for irreversible processes }$$
(is this even still an entropy difference? The notation $dS$ instead of $\Delta S$ confuses me) and elsewhere, talking about the Sterling process, it also says
$$ \oint_{irrev} \frac{\mathrm dQ}{T} < 0 \text{ , so the entropy of the machine (not the total entropy) decreases } $$
so it really must be talking about the entropy change in the system (the machine) and not about the total entropy change of system + surroundings. But how can this be when for a system in a circular process the difference in any state variable is 0?


texts: What is the correct way to notate conformation preferences of polysaccharides?

texts:
In some webpages (1 or 2) are found the way to notate the conformational preferences of monosaccharides such as furanose and pyranose.

But, it lacks to give a brief description on how to do it with polysaccharides.

For a given example:

Would it be: $^4C_1\ \phi\ \psi\ \omega\ ^4C_1$ ?

Or

Would it be mixed with Newman projections (3, 4 or 5): $^4C_1\ [a,s,t,g],\ [a,s,t,g],\ [a,s,t,g]\ ^4C_1$ ?

Or

What is the proper way to notate?


texts: Can you theoretically hold more of a volume of water the colder it is?

texts:
I have basic knowledge of chemistry and how it all works (will be taking the class next year) but I understand density and mass. Since the hotter a liquid, in this case, the molecules are more everywhere and not contained so to say. In a way, a $\ce{200 cm^3}$ cup will hold less water if say brought up to a temp of 90°C (194°F) and will hold more water if brought to a temp of 2°C(35.6°F) due to the molecules being more contained and not bouncing everywhere. Does this make sense or did I underestimate my understanding of this whole thing?

*I am talking about mass not volume.


texts: Why does the water in a Powerade bottle tastes a little like Powerade after many refills?

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I have a bottle of Powerade and after probably around 20+ refills of water, the new water I put in still tastes/smells a little like Powerade.

How does that happen?


texts: How do you know when the first compound is completely distilled and how do you know when the next compound starts

texts: Did a distillation between two solvents. Would the answer have to do with temperature?


texts: Is it possible to freeze water by dissolving a salt?

texts:
Theoretically, by dissolving a salt in water the melting point lowers, approximately 1.86 K kg/mol, making it more difficult to freeze water. However, the process of dissolution of certain salts is endothermic, lowing the temperature of the water. Is it possible that the water freezes due to that change of temperature although the melting point also lowers, or is it impossible?

For instance, consider the next case. In 1 kg of liquid water at 0 °C, we put a mol of KI. The melting point of water should be now about −1.86 °C. However, the enthalpy of dissolution of the KI is about 20 kJ/mol, meaning that the temperature of water should lower till −4.8 °C. So, theoretically, it should  freeze, but does this happen in reality?


texts: How do I achieve same crystallinity when cooling polymers?

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I am trying to make "films" of polyethylene glycol by melting them, pouring them into a mold and then cooling the mold down. The plan is to do this with different molecular weights. The problem is that depending on the molecular weight, the crystallinity will be different. Is there a way of ensuring that the crystallinity of the polymer is the same for all of them?
Thanks


texts: how to modify a transport device with an internal combustion engine with different atmospheres

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How to modify a transport device with an internal combustion engine with:

the methane-nitrogen atmosphere
carbon dioxide atmosphere
the atmosphere of argon and chlorine.

Which substances will react? How will they feed? How effective will it be?


texts: Regioselectivity in Friedel–Crafts acylation of thiophene

texts:
In the above reaction, I  understand that $\ce{AlCl3}$ is acting as a Lewis acid to generate an acylium ion, which is a strong electrophile.

Would this electrophile attack at carbon 2 or 3?

I think it would attack at C-3, as the resulting positive charge at C-2 would be stabilized by resonance using the lone pair on sulfur.


texts: How can a potential energy function be used to sketch different levels of the wavefunction?

texts: If the potential energy function is provided, say $V(x) = 5x^{2}$, how am I then able to use this function to visualize, graphically, the wavefunction where $V \neq \infty$?


texts: Notation for specific/volumetric entropy

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I'm working on a problem related to entropy, and for this particular use case it's advantageous to write down properties in 'specific' units. In the case of entropy (with units Joules over Kelvin, I think is commonly referred to as: $[S] = \pu{J K-1}$), I want to know how to communicate volumetric entropy, i.e. Joules per cubic meter Kelvin: $[\color{red}{?}] = \pu{J K-1 m-3 }$.

Is it something like $\bar{S}$?


texts:
This site states:

  It turned out that Upsalite had the highest surface area measured for an alkali earth metal carbonate; 800 square meters per gram.

Assuming that a sphere may enclose the maximum volume for a given surface area, the radius for a sphere enclosed by $\pu{800 m^2}$ is $\pu{7.9788 m}$. It's corresponding volume is $\pu{2127.656 m^3}$ - which leads to the incredible figure of something in excess of 2000 litres of water ... per gram of dessicant.

How much water vapour can a gram of Uppsalite absorb at NTP?


texts: Calculating volumes of acid/base required to make buffer using pH and pKa

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How would we use our $\mathrm{p}K_{\mathrm{a}}$ of the acid component of the buffer to calculate $\large \frac{[\ce{A-}]}{[\ce{HA}]}$?

I know $$\mathrm{pH} = \mathrm{p}K_{\mathrm{a}} + \log\left(\frac{[\ce{A-}]}{[\ce{HA}]}\right)$$ rearranging gives me $$\log\left(\frac{[\ce{A-}]}{[\ce{HA}]}\right)=\mathrm{pH} - \mathrm{p}K_{\mathrm{a}}$$
if for example the $\mathrm{pH}=4.5$, $\mathrm{p}K_{\mathrm{a}}=3.74$,

Is it correct to say
$$\dfrac{[\ce{A-}]}{[\ce{HA}]}=\dfrac{19}{250}$$
since
$$
\begin{align}
\log\left(\frac{[\ce{A-}]}{[\ce{HA}]}\right)&=\mathrm{pH} - \mathrm{p}K_{\mathrm{a}}F\\
\implies\log\left(\frac{[\ce{A-}]}{[\ce{HA}]}\right)&=4.5- 3.74\\
\implies\frac{[\ce{A-}]}{[\ce{HA}]}&=\frac{\operatorname{e}^{0.76}}{10}
\end{align}
$$
if $\dfrac{[\ce{A-}]}{[\ce{HA}]}=\dfrac{V_\text{b}}{V_\text{a}}= \dfrac{19}{250}$
how would I use this to find the volumes of acid and base needed to make my buffer?


texts: Assigning carbon-13 NMR for ethyl 2-oxo-2H-chromen3-carboxylate

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I have a molecule and an NMR spectrum, and I need to assign the NMR peaks to each of the carbons to the molecule:

I know that the 14.19 ppm and the 61.94 ppm correspond respectively to the carbon 12 and 11. However, I struggle for the other peaks especially between 116.76 and 148.51 ppm. I just know that it corresponds to the aromatic ring. Finally, I think that the 156.65 ppm and 155.15 ppm are respectively the carbon 9 and 10.
I also have the 1H NMR for this molecule:


texts: What does it mean to say "the 222 space group"?

texts:
I know there are supposed to be a few rotation axes, that it is non-centrosymmetric, it belongs to the orthorhombic crystal system, and it has four equivalent positions.

What do the 2s mean?


texts: Extraction of spilled methylamine from mud

texts:
I was reading this question about Breaking Bad on the Movies & TV Stack Exchange site and I'm wondering:

If you spill dirt in methylamine, can you extract the methylamine back out?

My very basic level of understanding leads me to believe that if you heat the resulting mud, you should be able to dry out the dirt and return it to its normal state, and likely create some type of vapor.  But, I'm probably completely wrong.

So, is this possible?


texts: If a sugar is nonreducing, does that mean it doesn't ionize in water?

texts: I'm thinking of sucrose, which I learned is nonreducing, what I take to mean it doesn't accept/take electrons from the surrounding solution. Does this also mean that it doesn't ionize and thus has a Van't Hoff factor ( i ) of 1?


texts: In rings in general, how do I determine how many unique carbons there are? In this example, I am thinking that there are 2 unique carbons (one on top and one with a double bond) since this molecule is symmetrical. Any feedback is appreciated.


texts:
In the Caffeine molecule, is aromaticity confined only to the 5 membered ring? The entire molecule is planar and the 6 membered ring also seems to have 6π electrons.
The entire molecule has 10π electrons.(inside)


texts: Why is the molecular geometry of a molecule with 5 bonds not uniform?

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I'll note that I'm a student in a rather introductory course, and today we learned about molecular geometries.

I'm curious as to why certain geometries (say, $\ce{CH4}$, tetrahedral) are uniform (evenly distributed in a sphere) while other geometries, say "$\ce{SbCl5}$," (5 bonds to the central atom) are less-uniformly distributed - two of the atoms are linear and 3 of them of trigonal planar.

Is this just a simplification for teaching introductory students, or is this how the molecule actually behaves?  I would think that to achieve "equilibrium" from the $\ce{Cl}$ atoms repelling each other, the distribution of the $\ce{Cl}$ atoms would be perfectly normal around the sphere.


texts: Dependence of mass transfer coefficient on solubility

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Does solubility of the solute affect the value of the mass transfer coefficient?

The book I am following mentions that the mass transfer coefficient is a characteristic of the constituent and its environment, and solubility is a property of the environment.


texts:
On a test question, my organic chemistry professor gave us a really big molecule and told us to give list the formal charges on each atom. There was a $\ce{Br}$ with 3 lone pairs and a double bond to carbon (which then had a single bond to a $
\ce{H}$ and a $\ce{N}$). On the key, he labeled it with a + charge and I was wondering how is that possible (or if it is a mistake)? Shouldn't a $\ce{Br}$ with that many electrons be highly negative or does it go onto the next orbital allowing it to accommodate for this?


texts: Naming a given organic compound according to IUPAC naming rules

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Would the given organic compound be called "3,4-diethyl-3,7,7-trimethylnonane" with IUPAC naming rules?

I don't really know if this should be called 3,4-diethyl-3,7,7-trimethylnonane, because it could also be called 6,7-diethyl-3,3,7-trimethyl something.
I am trying to do this by IUPAC rules.