texts: Perturbation theory for molecules, chromophore group, dipole approximation,

texts:
I am interesting in chromophore group and dipole approximation.

For example, i have a molecule (acetone or any other ketone/enol) which is belongs to some symmetry group. Because of the symmetry this molecule has degenerate energy levels. Now, i need to know the way how to destroy degeneracy.

The first and simple idea is to use perturbation theory and a dipole approximation, where perturbation caused by the light. This approximation let as to treat the interaction between light and molecule as dipole in  spatially-uniform electric field. Perturbation theory is common way to calculate absorption coefficients for systems that smaller than absorbed light (atom, diatomic molecule etc.) But the size of a molecule in example long compared with the size of a wavelength, so we  can't ignore the spatial variation of the electric field.

Solution of this situation is chromophore, part of a molecule where the energy difference between two  orbitals fits within the range of the UV or visible spectrum and responsible for the absorption of light. So now we can treat interaction between light and a molecule as an interaction between light and a part of that molecule which is responsible for the absorption. For example the C=O bond is a chromophore. So we treat absorption of light by a molecule as an absorption of light by a chromophore and save ourselves from complex calculations related to the size of the molecule.  The distance of a C=O bond is 1.22 Å while absorbance maximum at about 275 nm. Now the wavelength is long compared with the size of an chromophore, we  can ignore the spatial variation of the field.

My questions is:

Is this approximation correct? Can we approximate small perturbation by light applied to WHOLE molecule as a chromophore in spatially-uniform electric field? How rough is this approximation?
If this assumption is not right what else Way we can use/apply dipole approximation to a Whole molecule?
What else approximations is possible when we a dealing with a perturbation theory applied to a molecule?


texts: Ability to produce hydrogen gas on reaction with Na/K

texts:
Out of a given set of compounds, I was asked to identify which would produce hydrogen gas on reaction with Na/K. One of the given compounds was:

I could not detect any acidic hydrogen in it, so concluded that it won't produce hydrogen. But the answer says the opposite.

So my questions are:

Why does the above compound produce hydrogen gas?
What can be the general set of rules to decide which hydrogen shall be acidic enough so that hydrogen gas is produced on reaction with an alkali metal?


texts: My book says work can be converted into heat but I want to know how work affects kinetic energy of molecules which, when transferred, is called heat?


texts: Why did my iron nails not dissolve in hydrochloric acid?

texts:
I was trying to dissolve iron metal in HCl to make iron chloride, but ran into some problems. I'll give a brief background of my experiment. I took iron nails and put them in a container filled with muriatic acid (chemicals for my pool). The acid contains an equivalent of concentrated HCl since it is composed of HCl by 37.5%. The other 62.5% is listed simply as "other ingredients".

The faint yellow acid began to turn a more solid green yellow. Gas immediately began to bubble on the nails' surface. I left it for two days to dissolve and when I checked back the iron nails were not dissolved. They look shiny like the rust was cleaned off. The solution is black/dark green and there is a white/green precipitate at the bottom. The nails have small green crystals growing on them

I did this experiment once previously (with the same type of nail and HCl) with just a single nail inside of a hollow plastic pen tube and it seemed to have worked very well; it formed a dark brown solution at the bottom and the rest of the nail looked very rusted to a point where I could not remove it because the rust had stuck it to the inside of the pen.

Is there any explanation for the two different results and the iron nails not dissolving in my other trial? Also is there any guess as to what my solution and precipitate contains? Let me know if any more information is needed.


texts: What is the relationship between dipole moment and solubility?

texts: I thought a large dipole moment meant the substance was polar, so I'm confused by the following statement (from Wikipedia) that "With a dipole moment of 3.92 D, acetonitrile dissolves a wide range of ionic and nonpolar compounds...." Why would it dissolve many nonpolar compounds?


texts: Why does Zinc not have magnetic properties despite it being a transition element?

texts: I know Zinc has a full d-orbital which might contribute to the effect. But it is not ferromagnetic or paramagnetic like other transition element complexes. Why is that?


texts: Does the tetrahedral structure of the alkanes contribute to their lower reactivity? I thought that because a tetrahedral structure suggests ${sp^3}$ hybridization, it should contribute to its lower reactivity. Is this right?


texts: Why does exchange integral 1s2p not vanish for Helium excited state?

texts:
I am studying first-order perturbation theory applied to the first excited state of Helium. I am facing the following problem:

I understand that the Coulomb integral for all 2p functions will not be $0$, but for me, all the exchange integrals involving the 2p functions will be $0$. For example, look at this two integrals for the 1s2pz state:

1s function:
$$1s=\sqrt{\frac{Z^3}{a_0^3 π}}e^{\frac{-Z}{a_0}r}$$
2pz function:
$$2p_z=\frac{1}4\sqrt{\frac{Z^5}{2a_0^5 π}}re^{\frac{-Z}{2a_0}r}cosθ$$

Coulomb integral:
$$J_{p_z}=H_{(1s2pz;1s2pz)} =∫∫\frac{1s(1)2p_z(2)e^21s(1)2p_z (2)}{4πε_0r_{12}}dr_1 dr_2$$
$$J_{p_z}=\frac{Z^8 e^2}{128a_0^8 π^3ε_0} ∫_0^∞e^{{\frac{-2Z}{a_0}}r_1} r_1^2 dr_1 ∫_0^∞e^{{\frac{-2Z}{a_0}}r_2} r_2^4 dr_2 ∫_0^π\frac{senθ_1 dθ_1}{\sqrt{r_1^2+r_2^2-2r_1 r_2 cosθ_1}} ∫_0^{2π}dϕ_1 ∫_0^πcos^2 θ_2 senθ_2 dθ_2 ∫_0^{2π}dϕ_2$$
Exchange integral:

$$K_{p_z}=H_{(1s2pz;1s2pz)} =∫∫\frac{1s(1)2p_z(2)e^22p_z(1)1s(2)}{4πε_0r_{12}}dr_1 dr_2$$
$$K_{p_z}=\frac{Z^8 e^2}{128a_0^8 π^3ε_0} ∫_0^∞e^{{\frac{-3Z}{2a_0}}r_1} r_1^3 dr_1 ∫_0^∞e^{{\frac{-3Z}{2a_0}}r_2} r_2^3 dr_2 ∫_0^π\frac{cosθsenθ_1 dθ_1}{\sqrt{r_1^2+r_2^2-2r_1 r_2 cosθ_1}} ∫_0^{2π}dϕ_1 ∫_0^πcos θ_2 senθ_2 dθ_2 ∫_0^{2π}dϕ_2$$

In all cases, the electron 1 was placed along the z-axis for its $θ$ angle to be equal to the angle between the two electrons.
So, the exchange integral (K) will be zero because the integral:
$$∫_0^πcos θ_2 senθ_2 dθ_2=-\frac{(cos^2π-cos^20)}2=0$$
And the Coulomb Integral will not vanish because:
$$∫_0^πcos^2 θ_2 senθ_2 dθ_2=-\frac{(cos^3π-cos^30)}3=\frac{2}3$$
But in all the materials I have read, both Coulomb and exchange integrals are not zero, but they do not show the calculations. I have searched a lot on the internet, and I still have not found where my mistake is.


texts:
Work done under a constant pressure.

I know $$\Delta U = \Delta V \times \pi_T + C_V\Delta T $$

I thought I can give a try to find work done from above equation under constant pressure for an ideal gas.

$$q_p + w_p = C_V\Delta T$$
$$\implies C_p\Delta T + w_p = C_V \Delta T$$

$$\implies w_p = -\Delta T (C_p - C_V)$$
$$\implies w_p = - R\Delta T $$

Adiabatic work is $w_\mathrm{ad} = C_V \Delta T$

For a adiabatic work under constant pressure $w_\mathrm{ad} = w_{q} \implies C_V = -R \implies C_p = 2R$

Constant $C_p, C_V$ and negative $\gamma$ does not look correct to me.

Which of my steps are incorrect ?


texts:
The quantum theory of atoms in molecules is based on the topology of the electron density. This mathematical analysis allows to find critical points and hence has a unambiguous way of separating a molecule into atoms. Each atom can be assigned a basin, and integrating the electron density in it yields a partial charge of that atom (taking the charge of the nucleus into consideration).

In principle this analysis can be carried out from observed electron densities. It is also a more and more common tool to analyse calculated electron densities. Since it is only possible to solve the Schrödinger equation approximately, I also expect a dependency of the calculated charges on the level of theory. It is well known, that the Hartree-Fock method only accounts for Pauli correlation, while other methods also account for coulomb correlation. I would expect, that the higher the level of theory the more accurate the calculated charges are. Hence the following questions:

How dependent are computed charges using the quantum theory of atoms in molecules on the used level of theory?
Do calculated charges converge to a specific value with higher level of theory?
Are charges from calculated electron densities comparable to charges from measured electron densities?
(Optional) Are there more reliable methods to obtain partial charges?


texts:
I am told that $\ce{HCN}$ is a Lewis acid.

From what I understand a Lewis acid possesses (an) empty orbital that is accessible to attacking nucleophiles.

Does $\ce{HCN}$ have any empty orbital(s)? So how can it behave as a Lewis acid? I know prototypical Lewis acids are for example boron trifluoride, and these have an empty p-orbital.


texts: Van't Hoff Equation with changing Enthalpy

texts:
Is there a way to derive a modified van 't Hoff equation if we can't make the assumption that $\Delta H_\mathrm{r}$ doesn't change?

We know that $\mathrm{d} \ln K/\mathrm{d}T = \Delta H_\mathrm{r}/(RT^2)$ and $\Delta H_\mathrm{r} = \Delta H_\mathrm{r}^\circ + \int C_p\,\mathrm dT$

Is there a way to integrate the $C_p$ term along with the $T^2$?


texts: Help understanding external magnetic field sensitivity of radical pair reaction rate

texts:
Two recent papers have been published on magnetoreception in birds. In this case it is the ability of the birds to sense the direction of the Earth's magnetic field potentially for navigation.

Expression patterns of cryptochrome genes in avian retina suggest involvement of Cry4 in light-dependent magnetoreception Atticus Pinzon-Rodriguez, Staffan Bensch, Rachel Muheim J. R. Soc. Interface 2018 15 20180058; DOI: 10.1098/rsif.2018.0058. Published 28 March 2018
Double-Cone Localization and Seasonal Expression Pattern Suggest a Role in Magnetoreception for European Robin Cryptochrome 4 Günther, Anja et al.
Current Biology , Volume 28 , Issue 2 , 211 - 223.e4

The idea has been around a long time; cf A Biomagnetic Sensory Mechanism Based on Magnetic Field Modulated Coherent Electron Spin Motions Zeitschrift fur Physikalishe Chemie Neue Folge, Bd. 111, S. 1-5, (1978)

The two new papers address the role of something called "radical pairs", two molecules, each with an unpaired electron. The large molecules are in the retina and tend to have a preferred orientation with respect to the curved retina, and they also appear to affect the perceived intensity of blue light. This causes a modulation of light sensitivity across the retina dependent on the direction of the magnetic field with respect to the direction of the local normal vector of the retina.

The modulation of the reaction rate by the magnetic field direction has to do with singlet vs triplet states and quantum coherence, but I only say that because I've tried to read Cryptochrome and Magnetic Sensing by the Theoretical and Computational Biophysics Group at U. Illinois, Urbana-Champagne, as well as this Science Alert.

Are there simpler examples of the sensitivity of the reaction rate of "radical pairs" to the orientation of a magnetic field? Perhaps two atoms or two small molecules? Or does this phenomenon generally occur only in large, complex molecules?

below: "This is how a bird might see magnetic fields. (Theoretical and Computational Biophysics/UofI)" From ScienceAlert.


texts: Why did I get these inconsistent experimental results in silanization?

texts:
I used a 50% wt mixture of Tetraethylorthosilicate + Kerosene for silanization of some glass plates with different treatment times (from 1 sec to 35 sec). However, the contact angle(CA) that I got does not seem consistent as it does not always increase as I increase the treatment time (when treatment time increases, the CA fluctuates).

What might be the reason? and whether I should change the method or the solution(s)?

P.S. I cleaned the glass with acetone in a sonicator. Then I put the glass into solution and after specific time put it into water to clean the solution from surface and then clean the remaining oil (from kerosene) by rubbing a napkin to the glass plate. Then I measured the CA.


texts:
I have a molecule with a SMILES string as given below.
smi='c1ccccc1OCCOC(=O)CC'

I want to obtain BRICS based fragments which I did as follows.
frag=BRICS.BRICSDecompose(Chem.MolFromSmiles('c1ccccc1OCCOC(=O)CC'))

I obtain the following fragments.
{'[1*]C(=O)CC', '[16*]c1ccccc1', '[3*]O[3*]', '[4*]CC[4*]'}

How to interpret [1*], [16*], [3*] ,[4*] ? What does these number with brackets and stars means with each fragment?


texts:
Can anyone tell me what this $\ce{C17H28}$ molecule is? Has it been synthesized?  Does it have a name?

I was just interested in the molecule because it looks interesting.


texts: Is the flint used in disposable lighters toxic?

texts: Especially the sparks that result when using them. I heard this from a friend and can't seem to find an answer on Google.


texts:
What is it, that makes the Zinin Reduction a selective reduction, and not a complete reduction, in the case of dinitrobenzenes? Also, is the reaction a selective one even when it is done for aliphatic dinitro compounds, or is it, in that case,  a complete reduction to diamine? What about polynitro-aromatic compounds?

Do the relative positions of the two nitro groups in dinitrobenzene affect the reaction and its selectivity?


texts: Difference between equivalent conductance and equivalent conductivity

texts: I find questions in my book which ask for the equivalent conductivity and sometimes for the equivalent conductance. And then when I look at the solution, they've used the same formula for both. This has confused me a lot.


texts: How much CO2 is produced by plant litter?

texts: I made measurements of CO2 formed during decomposition of dead plant material using gas spectrometer. It gives the results of CO2 in ppm. How do I convert it to $\large \rm \frac{mg~CO2}{\text{1 g plant matter}}$ per day? I know that it has something to do with volume of my jar and and mass of plant litter, but that's all.


texts: What is the compound called when it is in solution?

texts:
When a compound precipitates out of solution, for example Calcium Carbonate from a water solution, it is called the precipitate.

What is the same compound called before it precipitates out - once it has dissolved? I found the word "electrolyte", but I'm unsure this applies to all solutions - only ionic, and I'm not sure a CaCO3 solution is ionic.


texts: Can we equate nucleophilicity and Lewis basicity?

texts:
Please note that it is specifically Lewis basicity, not any other definition of basicity.

Consider the interesting trend in nucleophilicity and basicity of the fluoride and iodide anions. The reason claimed for the weak nucleophilicity of the fluoride ion in polar protic solvents is due to the hydration effects which it experiences as it interacts with solvent molecules. This hydration effect effectively prevents it from reacting with electrophiles. In a sense, the hydration effect severely decreases the availability of the electron pair for donation.

Now, although it is claimed to be a weak nucleophile in aqueous solution, the fluoride ion still behaves as a strong Lewis base. This is logical because the interacting species are different in the two different situations. In the case of nucleophilicty, we are considering its nucleophilicity of the species towards another electrophile (e.g. a haloalkane) placed in solution.

In the case of basicity, we are considering it, in terms of its hydrolysis reactions with the water molecules in the hydration shell, producing the hydroxide ions. Thus, the solution becomes an alkaline one and we say that it is basic.

Now, if we use the same perspective to view nucleophilicity, we can thus say that the water molecule is the electrophile and that the fluoride ion is indeed a strong nucleophile because it has managed to attack the electron-deficient hydrogen atoms on the water molecule.

Consider this: What if I remove all the hydroxide ions produce from the hydrolysis of water from an aqueous solution of fluoride ions and add in an acidic species? Would we still observe a reaction between the fluoride ions and the acid species?

My point is that when we consider Lewis basicity and nucleophilicity of reacting species we are not making a fair comparison and thus, we say that fluoride ions are strong bases but weak nucleophiles in polar protic solvents. This may be true based on the Arrhenius definition of acids and bases. But if we were to look purely at Lewis basicity, it would be certainly be inaccurate.

From the perspective of interactions with water molecules, the fluoride ions are definitely good Lewis bases and also good nucleophiles. From the perspective of interactions with other reacting electrophiles placed into solution, the fluoride ions would be both weak Lewis bases and weak nucleophiles, neglecting the hydroxide ions (because even though the acidic species may react with the hydroxide ions, it is not reacting with the fluoride ions, thus we would see those reactions of the acids with the hydroxide ions as a side reaction).

Therefore, is it appropriate to equate these two terms because they both refer to the electron-donating ability of a chemical species?

If I have overlooked something (i.e. some other differences between the two terms), please inform me via the comments.


texts: Determining whether a compound is ionic or molecular in nature

texts:
$\ce{HCl}$ is a molecular compound because there is a covalent bond between $\ce{H+}$(a proton) and $\ce{Cl-}$ (a chloride ion)
$\ce{NH4NO3}$ is an ionic compound because there is an ionic bond between $\ce{NH4+}$ (an ammonium ion) and $\ce{NO3-}$ (a nitrate ion) even though all the atoms comprising the molecule are non-metal.
Then, which of the following is true?
$\ce{H3C-COOH}$ is an ionic compound because there is an ionic bond between $\ce{C2H3O-}$ (an acetate ion) and $\ce{H+}$ (a proton)? OR
$\ce{H3C-COOH}$ is a molecular compound because there is a covalent bond between $\ce{C2H3O2-}$ (an acetate ion) and $\ce{H+}$ (a proton)?

How do you tell if a bond between the two ions are molecular or ionic? (regardless of whether they are polyatomic or monoatomic ions)


texts: I understand that $$R_\mathrm{f} = \frac{\text{distance traveled by center of analyte spot } (b)}{\text{ distance travelled by solvent front } (a)}$$ What I do not understand is why this is called retardation factor; an analyte that travels further in the mobile phase seems to me to be less retarded by the stationary phase, while one that doesn't travel as far seems more retarded. If we're using this terminology why doesn't $R_\mathrm{f} = 1- \frac ba$?


texts: Do L-sugars (enantiomers of natural sugars) have a sweet taste?

texts: I'm wondering about how L-sugars taste. They are obviously not digestible by humans, but what do they taste like? If they are sweet, too, why isn't sucrose with the unnatural chirality used as a zero-calorie table sugar substitute?


texts: How to make something solid that dissolves faster than bar soap in water

texts: What is a soap-like material that holds a solid shape, but dissolves completely in water over 10-15 minutes. Think disappearing Rubber Ducky.


texts: Nomenclature of the following aromatic compound

texts:
What is the name of the compound $\ce{(C_6H_5)-CH=N-CH_3}$  ?

I doubt,  it is  n-methyl benzalamine . Is it correct ? Besides , what could be other names of it?


texts: I'm a writer. I have a scenario in which a sizable amount of gold needs to be rendered unusable, preferably completely destroyed. I know an acid like aqua regia is able to dissolve gold, but would there be a way to make it impossible (or at least not worth the cost) to chemically salvage the gold from the acid, or another way to permanently destroy gold?


texts: Equilibrium constant for the neutralization of weak acid by strong base

texts:
Acetic acid has a $K_\mathrm{a}$ of $\pu{1.8e-5}$. What is the equilibrium constant for the neutralization of this acid with $\ce{NaOH}$?

Given acetic acid

$$\ce{HC2H3O2 + H2O <=> C2H3O2- + H3O+} \qquad K_\mathrm{a} = \pu{1.8e-5}$$

$$\ce{HC2H3O2 + OH- <=> C2H3O2- + H2O}$$

So, if we do $K_\mathrm{w} = K_\mathrm{a}K_\mathrm{b}$, then we get $K_\mathrm{b} = \pu{5.55e-10}$. How do I use this to find $K_\mathrm{eq}$?

I know how to find $K_\mathrm{eq}$ using concentration, but I am unsure how to approach this further. The hint says consider the ion product of water, but what does this mean?


texts: Do I use the Nernst equation when the concentrations of electrolyte in both half cells are equal?

texts:
I'm doing a chemistry report, and for my experiment I investigated the amount of voltage produced by different half cells in a voltaic cell.

However, I tested them under nonstandard conditions as the temperature at the time was $\pu{18^\circ C}$, and the concentration of the electrolytic solution in the half cells was $\pu{0.1 M}$.

I tried the Nernst equation, but since the concentration of both my electrolytes were $\pu{0.1 M}$, calculating the reaction quotient gave me an answer of $1$, and $\log 1 = 0$, therefore I'm left with the same cell potential I started with (cell potential at standard conditions) and I'm stuck there.

Here is an example for a magnesium-zinc voltaic cell at $\pu{291 K}$ ($\pu{18^\circ C}$):

$$E_\text{cell} = 1.593 - \frac{0.05778}{2} \log_{10} \frac{0.1}{0.1} = \pu{1.593 V}$$

Could you please explain the solution to me?


texts: Trouble to predict the effect of pressure and temperature for a reaction in equilibrium

texts: I have trouble to predict the effect of decreasing pressure and increasing temperature on the reaction $\ce{N2 + 2O2 <=> 2NO2}$. Increasing temperature caused this reaction to shift in the forward direction and decreasing pressure brought no change. I know increasing temperature favour endothermic reaction and decreasing temperature favour exothermic reaction. I also know on increasing pressure the system will shift to the direction where less moles are present. Please tell me how to use this information to predict the effect for increasing temperature and decreasing pressure.


texts: Normalization of the wavefunction φ(x) = A

texts:
I was trying to normalize the wave function

$$
\psi (x) = \begin{cases} 0  & x<-b \\ A & -b \leq x \leq 3b \\ 0 & x>3b
\end{cases}
$$

This is done simply by evaluating

$$
\int\limits_{-b}^{3b} | \psi (x) |^2 dx = 1
$$

I found that

$$
A = \pm \frac{\sqrt{b}}{2}
$$

This gives the normalized wave function

$$
\psi (x) = \begin{cases} 0  & x<-b \\ \pm \frac{\sqrt{b}}{2} & -b \leq x \leq 3b \\ 0 & x>3b
\end{cases}
$$

This was quite straight forward... too straight forward for my liking. My question is twofold:

1) Is my derivation above correct? And
2) How shall I deal with the ``$\pm$'' sign in front of the fraction? Should that be included in the expression for $\psi (x)$? Do I then have two different wave functions for the same particle, one negative and one positive? Maybe one of them do not carry any "physical significance", and can be dropped?


texts:
An oxidizing agent pulls the electron cloud of the substance being oxidized towards itself, for example:
$$\ce{F2 + 2 X- -> 2F- + X2}\qquad (\ce{X} = \ce{Cl}, \ce{Br}, \ce{I})$$
We also know that fluorine has very high charge/mass ratio as it is very small in size and its electron gain enthalpy is know to be very high, i.e gain of electron is favourable thermodynamically.
Also, many sources state that:

Fluorine has low bond dissociation enthalpy and high hydration enthalpy due to which fluorine is a good oxidizing agent.
Fluorine is achieving octet, so electron gain is favorable.
I found another source stating that bond dissociation enthalpy is the major driving factor.

My questions(along with reasons why fluorine shouldn't be oxidising agent)

What has hydration enthalpy and bond dissociation enthalpy got to do with oxidizing power?
(As we know that lithium is the best reducing agent, and it also has high hydration enthalpy but we can’t say it is an oxidising agent.)
What am I missing here? What is the reason for such high standard electrode potential for fluorine?
Why wouldn't the electron cloud of fluorine atom repel the electron cloud of substance being oxidized? It seems paradoxical that the fluorine pulls electron cloud towards itself so easily.

Even in the post Why does chlorine have a higher electron affinity than fluorine? it is mentioned that electron cloud is repelled.
Is there any better explanation other than "octet is being achieved", such that it resolves the repulsion issue, to explain why fluorine is a good oxidising agent?


texts: How can I calculate the standard reaction enthalpy if I lack one formation enthalpy?

texts:
I have this reaction, for which I need the standard enthalpy of reaction:

$$\ce{CuO (s) + H2S (g) \rightarrow CuS (s) + H2O (g)}$$

This is the data from the NIST web book (standard formation enthalpies, $\mathrm{kJ}\cdot\mathrm{mol}^{-1}$):

$\ce{CuO (s)}$: -156.60
$\ce{H2S (g)}$: -20.5
$\ce{H2O (g)}$ -241.83

There are no data tabulated for $\ce{CuS (s)}$, so how can I compute the standard reaction enthalpy lacking this data?


texts: What happens when (+) 2-iodobutane is treated with NaI in acetone?

texts:
After treating the compound with NaI, we should follow SN2 mechanism and the product will follow an optical inversion, giving us (-)2-iodobutane, but the answer is (±)2-iodobutane.

After going through various articles, I am getting reasons, such as there will be an equilibrium created between the reactants and the products, hence we will get both the products (±)2-iodobutane.

And there is the same question where we are treating (R)-2-bromobutane with NaI in acetone, but the answer is (S)-2-iodobutane.

What could be the reason?

I believe we should simply get one product in the question, and there will be no equilibrium be created, as there shouldn't be enough NaI left to form another compound.


texts: What is the dimension of Avogadro's constant?

texts:
What is the dimension of Avogadro's constant ($N_\mathrm{A}$).
On Wikipedia it says it is dimensionless, but in Nigel Wheatley's article (pdf) On the dimensionality of the Avogadro constant and the definition of the mole it says it is $\mathsf{N}^{-1}$.
\begin{align}
\text{Number of particles} &= N_\mathrm{A}\times \text{Amount of substance}\\
[\text{Amount of substance}] &= \mathsf{N}\\
[\text{Number of particles}] &= \mathsf{1}
\end{align}
If $[N_\mathrm{A}] = \mathsf{N}^{-1}$ then the above equation follows, otherwise it doesn't. Is this the right value?


texts:
Assume that $\ce{pKa}$ is 4.76

  Mix $\pu{50 mL}$ of $\pu{0.1M}$ $\ce{HA}$ and $\pu{50 mL}$ $\pu{0.1M}$ $\ce{NaA}$. This is solution (i). Calculate concentrations of $\ce{HA}$ and $\ce{A-}$, measure the $\ce{pH}$.

  Then, mix $\ce{10 mL}$ of solution (i) and $\ce{90 mL}$ of water. Calculate $\ce{[HA]}$ and $\ce{[A-]}$, and measure the $\ce{pH}$.

How do I approach these calculations? I have 13 of these to do, these are the first two.

Equation is:
$$\ce{pH} = \ce{pKa}+\log{\left(\frac{\ce{[A-]}}
 {\ce{[HA]}}\right)}$$

For the first one, I got,
$$4.76 + \log{\left(\frac{0.1}{0.1}\right) = 4.76}$$
But I don't know if that's correct. How would I approach the subsequent problem when water is added?


texts: Why does elemental Iodine form a brown solution with Ethanol but not with Isopropyl alcohol?

texts:
Although it is not the standard procedure for making iodine solution, I have dissolves pure Iodine granules in Ethanol to produce a brown solution which will produce a positive test for starch by creating a purple color.

I tried to create the same solution with isopropyl alcohol but it doesn't work.  The Iodine does not dissolve noticeably, and whatever small amount may be dissolved does not complex with starch.

How does Ethanol dissolve elemental Iodine so well especially compared to Isopropyl alcohol?


texts:
I found out there are two definitions of relative atomic mass $A_\mathrm r$.
First definition is $A_\mathrm r$ is the mass of 1 atom of an element relative to 1/12 the mass of carbon-12 atom. It can be found in any chemistry school textbook.
Second definition is what I just found and dont understand. It states $A_\mathrm r$ is the mass of 1 mole of atoms relative to 1 mole of carbon-12 atoms.
Can you kindly explain second definition with examples?


texts:
The following is the equation I have:

$$\ce{Ca(s) + 2H2O(l) -> Ca(OH)2 v  + H2 ^}$$

I am tasked to write the half-reaction equations for both the oxidation and/or reduction process. So, currently I have:
$$\ce{ Ca(s) -> Ca^{2+}(aq) + 2e-}\quad\text{(oxidation)}$$

but I'm not sure how do you write the reduction equation for the water and hydroxide.

Any help is appreciated :)

P.S.: I have no idea how to superscript or subscript in the forum.


texts: What are the dangers of handling 0.12N sulfuric acid?

texts:
I'm handling 0.12N of sulfuric acid for a science experiment that I am carrying out for a school project. I hear about all these terrible effects if it's ingested, inhaled, or gets in contact in skin. But how dangerous is it?

My safety equipment that I'm using currently are a pair of polyvinyl gloves, goggles, long sleeve shirt, apron, jeans, and closed toe shoes. However, I do not have a respirator and wondering if I should get one.

Would it be safe to handle this without a respirator? I will not be spraying the sulfuric acid directly in the air. However, I will be adding approximately 0.5mL of the 0.12N sulfuric acid into 500mL of water, putting it in a spray bottle, and be watering some plants with it. Will it still be dangerous even spraying a low concentration in the air?

Would the 0.12N concentration still be enough to cause chemical burns on my skin? To what extent and severity? Also, just to confirm, it is safe to add drops of the acid to water, but not vice versa? I would really appreciate the advice that you can provide me.


texts: Can an enol acetate be formed through Fischer esterification?

texts: Since acetone is converted into its enol form under acidic conditions, could it participate in Fischer esterification to form an enol acetate? For example, would refluxing acetone, p-TSA, and acetic acid form the unsaturated ester?


texts:
While reading Pauli's Exclusion principal from here, they said that

  The Pauli Exclusion Principle states that, in an atom or molecule, no two electrons can have the same four electronic quantum numbers." Now again in we know that the The orbital angular momentum quantum number $l= 0,1,2... (n-1)$ – Source

So from here we can say that $l\neq n$. So here automatically no two electrons can have the same four quantum numbers.  So what's new in Pauli's principle?


texts: How to calculate pH of solution made of H3PO4 and Na3PO4?

texts:
I am unable to calculate the $\mathrm{pH}$ of a solution made of $\pu{0.1 M}$ $\ce{H3PO4}$ and $\pu{0.05 M}$ $\ce{Na3PO4}$.

How to set the approximation and which ions are present at the equilibrium?


texts:
What is the difference between diatomic molecules and elements?

Also, If oxygen is element of a single atom, then what makes it a diatomic element? But, then I read that a single oxygen atom can bind with another element to form a compound, but it's a diatomic element with two atoms.

Please can someone enlighten some clarity on this subject. Also, it would help to see some examples to see the differences and context of how these diatomic molecules and elements interact.


texts: What is the purpose of the electrolyte in the half-cell where oxidation is taking place?

texts:
In an electrochemical cell that consists of two half-cells, there is an electrolyte and an electrode in each half-cell.

Example:
$$
\begin{align}
\ce{CuSO4(aq) + 2e- &-> Cu(s) + SO4^2-(aq)} \\
\ce{Zn(s) + SO4^2-(aq) &-> ZnSO4(aq) + 2e-}
\end{align}
$$

In the half-cell where the reduction takes place, $\ce{Cu^2+}$ gains two electrons. Here the electrode and the electrolyte serve a purpose, as it is the $\ce{Cu^2+}$ ion from $\ce{CuSO4}$ that goes through a reduction reaction.

However, in the half-cell where the oxidation takes place, it is $\ce{Zn(s)}$ that loses two electrons and forms $\ce{Zn^2+(aq)}$. Thus, the $\ce{ZnSO4}$ does not seem to play any role in the oxidation. Why is it included in the electrolyte in the zinc oxidation half-cell


texts: In orbital hybridisation, what determines the number of orbitals that hybridise to be at the same energy level?

texts:
For example, in phosphorus pentachloride five orbitals hybridize, but why not 6, as in the hydrated Al ion? I have read that the reason six orbitals hybridize is that a maximum of six oxygens can stably fit around it. Why is it not the same case for phosphorus?
Secondly, why does water $sp^3$ hybridize even though it has enough lone pairs in its p orbital to bond with 2 oxygens. Surely it would take more energy to pull up the lower $s$ orbital to bond than to allow the $p$'s, already elevated to that energy, to do the bonding?


texts: Will ground glass joints relieve pressure non-catastrophically?

texts:
I need to heat a fluid for seven days at a time. The fluid goes in round bottom flask that is suspended in a water bath. The test fluid will decompose and generate a small amount of gas over time.

Gas generation is variable and dependent on what material I am testing in this material compatibility experiment.

I have experience in plumbing and fluid systems but not chemistry. In a plumbing system I would add a relief valve to relieve the pressure generated over time, without allowing potentially dirty air to contaminate the experiment.

I have a ground glass joint. I found a source that says the ground glass plug will lift to relieve pressure, even if I put a plastic clip on it, and the plastic clip would ensure the plug would not go flying.

I still have concern since this is an environment I am not familiar with, and I am not keen on exploding glassware in the facility. Past experimenters have placed small beakers upside down on top of the flask, and have also used aluminum foil as a cover (I will not do this so the vapor contact with foil does not affect the experiment results). I tried it with a beaker but a moderate amount of fluid condensed on the surface, which was not ideal.

Will I be fine securing a ground glass joint with a plastic clip, should I use an upside down beaker, or is there a more obvious solution?


texts: Why doesn't curie temperature follow a periodic trend in ferromagnetic materials

texts:
I was writing up an answer to a question which was asking why the Curie Temperature's of $\ce{Fe, Co, Ni}$ don't follow a periodic trend. The OP voluntarily deleted his question before I could finish and post my answer.

The OP has reasoned as follows: Since Iron, Cobal and Nickel have electron configurations $\ce{[Ar] 3d^6 4s^2, [Ar] 3d^7 4s^2\ \text{and}\ [Ar] 3d^8 4s^2}$, giving them 4 , 3, and 2 unpaired electrons respectively. This according to the OP should suggest a periodicity in Curie Temperature's which isn't observed.

Clearly this isn't the case. For your reference, the Curie temperatures for the three metals are (iron, cobalt, nickel):    $1043\ \mathrm{K},  1400\ \mathrm{K},  627\ \mathrm{K}$

Since this did indicate some ignorance about the origins of magnetism, I decided to to write up a short answer, describing the salient features and at the same time correcting OP's misconception. The answer was kept relatively simple, and was nearly done but OP chose to delete his question.

Not wanting to let a answer I put some effort in go to waste, I am posting it here. Additionally, since the goal of this site is to build a Q&A, it would be great if others could chime in with their views, derivations etcetera.


texts: What happens when a body of water and a pice of ice are placed in a pricessly controlled zero degree environment

texts: My understanding is, if you put ice into a >0 degrees environment, it will be 0 degrees as it melts and if you put water into a <0 degree environment, it will 0 degrees as it freezes. but what happens if you put water and ice in to an environment maintained exactly at 0 degrees. I'm inclined to think it should be said water freezes below 0 and ice melts above 0, I'd go so far, pending a satisfactory answer of course, is to suggest, what happens to water and ice at 0 degrees is nothing at all. Please put me out of my misery on this :-D


texts: Reverse Image Searching a ChemDraw Figure

texts: Is there any image-recognition software out there that can read in a high-resolution image of a ChemDraw-generated figure and back out the structure (such as the SMILES or INChI)? I have a bunch of review papers where there are tables upon tables of ChemDraw images of molecules and would really like to put them into some useable database.


texts: How does the use of inert gas in fluorination of saturated aliphatic hydrocarbons make it less violent?

texts:
While studying alkanes, I found this written in my book:

Fluoridation can be achieved without violence when alkane is treated with fluorine diluted with an inert gas, or by the action of inorganic fluorides like $\ce{AsF3}$, $\ce{SbF3}$, $\ce{AgF}$, $\ce{HgF2}$, $\ce{Hg2F2}$, etc., or by use of bromo or iodo derivatives.
The picture is given below for clarification:

Inert gases are chemically inactive, except xenon and radon, which are radioactive and may form some compounds.
How do the non-radioactive inert gases help in reducing the violence of fluorination? If I put a certain volume of fluorine and an alkane in a jar for reaction, then even if inert gases are present, they won't react. What is their role?


texts: In the presence of an electron-rich species, why is Br2 the stronger electrophile than water?

texts:
In the electrophilic addition of aqueous bromine to ethene, the first slow step involves the electron rich (pi bond) of ethene attacking the bromine molecule to form a carbocation and Br-:

And, then water will react with the carbocation to form 2-bromoethanol. But, why does bromine react with ethene first and not water(which is of higher concentration)?

I think it's because Br2 is the stronger electrophile than water. But why is that? Oxygen is much more electronegative which makes H more electron deficient than Br and thus a stronger electrophile?


texts: Why must polymers have a repeating unit?

texts:
In organic chemistry, we learned that small molecules can form a polymer via a process called polymerization. For example, $\ce{CH2=CH-Br}$ molecules can form the polymer

\begin{align}
\ce{nCH2=CH-Br-> -[-CH2 -}&\ce{CH -]_n -}.\\
&\;\ce{|}\\
&\ce{Br}
\end{align}

So the polymer is a periodic chain $\ce{-CH2-CHBr-CH2-CHBr-\cdots}$. But since every monomer can have two orientations ($\ce{-CH2-CHBr -}$ or $\ce{-CHBr-CH2 -}\!$), there is no requirement that all monomers must be in the same orientation, does the polymer have to be a peroidic chain? Can it be a random chain with a structure that looks like

$$\ce{-CH2-CHBr-CHBr-CH2-CHBr-CH2-CH2-CHBr-CH2-\cdots}\,?$$

Most textbooks emphasize that $n$ is random, but still assume that the unit repeats.


texts: How can sodium be reduced in the Castner–Kellner process?

texts:
In the Castner–Kellner process, why is sodium amalgam formed instead of hydrogen gas at the cathode?

If we electrolyse brine solution, then it will liberate hydrogen at cathode, not sodium, because $\ce{Na+}$ has a negative reduction potential while that of $\ce{H+}$ is (by definition) 0. What factor here causes the sodium to get reduced to form an amalgam in spite of the reduction potentials?


texts: Why is Quinine more soluble in an acidic aqueous solution than an basic aqueous solution?

texts:
How do I find out if Quinine or in general if a compound is more more soluble in an acidic aqueous solution than an basic aqueous solution?

Here is the structural formula for quinine:


texts: Does 3‐ethyl‐1,1‐dimethylcyclohexane have a stereocenter?

texts:
I knew that we have a stereocenter if the carbon is bonded to four different groups.
According to the stereocenter rules, I should have $\ce{CH2}$ bonded to the carbon of the stereocenter (marked with asterisk), an ethyl and a hydrogen. How is it possible to have two equal groups? What did I do wrong?


texts: How can I formulate a rate equation using a solid catalyst?

texts:
When formulating a rate a equation two experiments must take place: one in which the reactant concentrations are varied, and one in which the catalyst concentrations are varied.

If I am given a sample of a solid catalyst, such as $MnO_2$, how can I change its concentration? Because I can't dilute a solid and increase the volume, which is how I'd do it for a catalyst in solution.


texts: Do bond lengths change upon protonation of a molecule such as an H2O molecule?

texts: Wouldn't the hydrogen atom in a hydronium cation feel a greater proton repulsion force (nucleus-nucleus repulsions) from the oxygen atom and orient away from the oxygen atom to maximize the attractive force it has for the shared pair of electrons by minimizing proton repulsions?


texts: Does tolerance to alcohol affect blood/breath alcohol levels?

texts:
When blood / breath alcohol levels are taken to determine how intoxicated a person is, does it depend on their tolerance ?

i.e. If you had two people of identical age, weight, fitness, etc.

person A, a non drinker, drank 1 measure of alcohol over a period and felt quite "drunk"

while person B, a frequent drinker drank the same measure of alcohol over the same period, but because of their built up tolerance felt and acted considerably more sober.

would they give the same blood, or breath alcohol readings, despite the effects on the person being different ?

Sorry if this is a very poorly formatted question from a chemistry point of view, i know absolutely nothing, nor have interacted with any of the sciences since school.

I was also not sure whether this comes under chemistry or biology, if it needs changing to the biology stack exchange site please advise


texts: CO2 conversion to a harmless gas like oxygen

texts: I am doing some research about indoor purifiers and I was wondering if there is any approach to purify co2 or convert it to harmless gases like oxygen just like what plants do.


texts: How to determine electrolyte concentration in solutions?

texts:
The original question is here

  We've been given the sports drink vs orange juice challenge. To find out which has more electrolytes. I could test for conductivity but that alone wouldn't tell me which has more actual electrolytes in it. So I'm wondering if there's a way I could separate each ion from each other and measure them that way?

I'm posting it here because I'm very curious as to the answer.

Several people have suggested evaporation.

  You can try evaporating the liquids and seeing what's left behind. The electrolytes will be left behind as solids.

However, the issue with evaporation is that it leaves behind all solids - electrolyte or not.

Some people have suggested conductivity measurements.

  Wouldn't conductivity simply be proportional to the concentration of substances that promote conductivity?

However, this objection was raised:

  Well my understanding was that different ions produce different voltages, therefore, there could be a lot of one type of electrolyte producing a large voltage but there could be more electrolytes in the other solution producing a smaller voltage. I'm not sure though as I am in first year and haven't had this completely covered yet. My professor said that conductivity might not give enough information so I may need a second approach as well, I'm not sure what he means exactly.

Is this a valid point? I guess we could empirically test out this assertion that "different ions produce different voltages" by comparing the conductivities of two otherwise identical NaCl and, say, MgBr2 solutions. Wouldn't the MgBr2 have a conductivity measurement that is roughly 1.5 times that of the NaCl solution? Or is it true that the ion's charge affects the conductivity?


texts: Difference between white sugar, brown sugar and red sugar

texts:
I always get confusing why the appearance of normal sugar (the white one), brown sugar and red sugar are different although they are sugar. Is it because they each have different molecular formulae or different number of bond or maybe the brown and red sugar have some transition metal inside?

I really don't. So, I wish someone will help on this question.


texts: What are the other ways (if they exist) that atoms can gain or lose electrons that aren't bonding?

texts: I know that electrons can be isolated through human intervention from their atoms. My question rather concerns if electrons are ever lost or gained naturally. I recognize that this is a stupid question but I couldn't find the answer on the Internet.


texts:
Background (pointform for readability):

I prepack oral medication for a hospital.
Our work area consists of a long stainless steel countertop.
We use plastic bins to transport the medication around the pharmacy. To clean the bins, we use cloths premoistened in a 0.3-0.5% solution of Hydrogen Peroxide (can't remember the exact concentration).
While the bins are drying, they're stacked on top of the counter. The bins at the bottom are often left facedown, which prevents then from drying properly.
We noticed bin-shaped stains appearing on the counter where we let the bins dry. I figured the Peroxide was oxidizing the counter.
70% alcohol, water and goo-b-gone had no effect on the stain.

Today, something was allowed to dry on the counter. It dried to a white powder. I'm almost certain it was a 4 mmol/ml solution of NaCl, but I don't know for sure. When I cleaned the counter off, the part underneath the power was completely clean! It looked brand new. We tried applying more NaCl to it, but we didn't have time to let it dry, and there was no noticeable change when we cleaned it off.

What I know/don't know:

I'm pretty sure the counter is stainless steel. We have signs up in the area with directions for cleaning stainless steel countertops.
The solution was almost definitely sodium chloride. If not, the only other thing I can think that it could have been is Sodium Phosphate; but I've never seen it dried, so I don't know for sure.

What could have happened here? I know rust can't be "undone". The only thing I could think of is somehow the top layer was removed; but I can't see saline doing that.

Can anyone think of what may have happened?


texts: London Forces and Liquifying Noble Gases

texts:
From my book, it says that 'without van der Waals (London Dispersion) forces, it would be impossible to liquefy noble gases.'

Why is this the case?


texts: Can you discriminate a monooxygenase from other enzymatic mechanisms by the requirement of NADPH?

texts:
I am working on a project about CYPs 450. It seems that most of them function as monooxygenases but there are other categories as well.

Assuming that the question makes sense, is it correct to say that CYP 450 monooxygenases always require the presence of a regenerating system (NADPH) as opposed to other CYPs 450 which are NOT functioning as monooxygenases?


texts: How to switch Mercury-vapor lamp between UVA and UVC bands?

texts:
I have Mercury-vapor lamp emitting UV light. I am looking for the nice solution to cut off spectral lines for UVA or UVC, to make it one day to generate ozone and another day to use it for disinfection as UVC band lamp. I mean using precoated tubes and put mercury vapor lamp inside or using coated glass as a shield.

Related: What property allows ozone to absorb uv light


texts: Recently, the houses next to us were fumigated with "Vikane", which apparently is $\ce{SO2F2}$. To my surprise, the gas was just pumped out in the atmosphere without further ado at the end of the procedure. I was told by the pest control people that this gas is "degraded by light" and that there is no hazard whatsoever for humans living close to the house. However, I've also read that sulfuryl fluoride is a potent greenhouse gas staying in the atmosphere for up to 40 years which it probably wouldn't do if it were deteriorated easily by light. Which is it??


texts: Formation of tetrahydrofuran in the reaction of n-butanol with lead tetraacetate

texts:
When n-butanol reacts with lead tetraacetate it forms tetrahydrofuran.

And lead tetraacetate is a good oxidising agent so why doesn't it form n-butanal?

So when does cyclisation take place and why?


texts: Why is a silent electric discharge used for the preparation of ozone from oxygen?

texts: I learnt that ozone is prepared by passing oxygen through a 'silent' electric discharge. Can someone please explain what is meant by a 'silent' discharge here, and why that helps? I couldn't get a satisfactory answer while Googling.


texts: How to calculate atoms of *each* element in a compound

texts:
I am trying to do the following exercise in a chemistry workbook. I have searched over internet but I couldn't find or understand it.

How many atoms of each element are found in:

5 moles $\ce{H2SO4}$

Now the only confusing thing for me is the 5 moles.
For example lets take $\ce{H2}$ element

so n=N/Na --> n × Na = N (number of atoms)
2 × 1gr/mol H = 2 moles H x 5 moles in the compound = 10 moles
10 moles $\ce{H2}$ × 6.02 × $10^{23}$ = 60.2 × $10^{23}$ atoms

Or do I do like this?

5 moles $\ce{H2}$ × 6.02 × $10^{23}$ = 30.1 × $10^{23}$ atoms


texts: Relation between ∆(tetrahedral) and ∆(octahedral), ∆t = 4/9 ∆o

texts: I remember my teacher saying that ∆(tetrahedral) being 4/9 times the ∆(octahedral) for the same ligands and the same central metal ion due to some analogy by number of ligands, but I do not seem to remember it.


texts: Reaction rate constants for the inhibition of cholinesterases by various carbamates

texts:
Darvesh et al. [1] have conducted a study on the anticholinesterase activity of various carbamates derived from phenothiazine. The authors measured the inhibition rate constants of rivastigmine for acetylcholinesterase and butyrylcholinesterase as $\pu{1.13E3 M^-1 min^-1}$ and $\pu{129E3 M^-1 min^-1},$ respectively.
I want to see how the anticholinesterase activity of the different compounds studied by the authors compares to that of more traditional carbamates. What are the AChE and BuChE inhibition rate constants for pyridostigmine, neostigmine, TL-599, their uncharged analogs, and carbaryl?
Reference

Darvesh, S.; Darvesh, K. V.; McDonald, R. S.; Mataija, D.; Walsh, R.; Mothana, S.; Lockridge, O.; Martin, E. Carbamates with Differential Mechanism of Inhibition Toward Acetylcholinesterase and Butyrylcholinesterase. J. Med. Chem. 2008, 51 (14), 4200–4212. DOI: 10.1021/jm8002075.


texts: When 3-chloro-2,2-dimethylbutane reacts with water what are all of the products and followup questions

texts:
I would like to know what all the products are. I know that in the classical Sn1 reaction, we have 3,3-dimethyl-2-butanol. For the alkyl shift in a Sn1 reaction, we also have 2,3-dimethyl-1-butene and 2,3-dimethyl-2-butene.

I have other follow up questions: This is my first time learning about organic chemistry as a layperson. I have no access to university resources like equipment. How do chemists separate all of this in a lab setting?

Also, I'm curious about these alkyl shifts. How do you explain them? From what I understand when the carbon is attached to four other carbons and it is adjacent to a carbocation, we can have the methyl group move over to the adjacent carbocation. This is used when a hydride shift is not favorable due to higher order carbocations being more favorable.


texts:
Recently I read about Hyperconjugation. But i have a doubt.

What is the need of hyperconjugation in this structure when there is charge separation resulting in lesser stable structure.


texts:
I am looking for a cationic detergent for a project.  Unfortunately most ( or all?) cationic detergents are quaternary ammonium that smell like rotten fish or even worse
The product I am working on can not have odor. Is there such cationic detergent out there or an odor neutralizer ?


texts: How come uranium's relative atomic mass is 238.03 when it only contains isotopes with a mass number of 238 or less?

texts:
I have always been led to understand that the mass of an element on the periodic table is the weighted average atomic mass over all naturally occurring isotopes. This seems to make sense with all the elements I have looked at except for uranium. Wikipedia's featured article on the element assures me that uranium's relative atomic mass is 238.03. The commonest isotope is U-238, mixed with 0.72% of U-235 and 0.005% of U-234, plus traces of a couple of isotopes with smaller mass numbers.

How then can uranium's relative atomic mass exceed 238? Either I have completely misunderstood something, or there is something else at work - relativistic maybe?


texts: Are there any surface treatments that would make calcium usable for metallurgy?

texts:
Calcium is the best conductor for its weight, but the soluble powdery oxide makes it impractical for use in power lines.  Are there any surface treatments or alloying processes that could help?

(Calcium phosphates are reasonably insoluble, but I don't know how well they bind to the metal underneath; lithium-aluminium alloys are used in a lot of aerospace applications despite the strong reactivity of lithium with air and water)


texts:
When Methyl D-glucopyranoside is treated with $\ce{HIO4}$, what is the amount of $\ce{HIO4}$ (in moles) consumed per mole of the sugar?

I have studied that $\ce{HIO4}$ oxidises only those vicinal diols which are cis to each other. But here only one pair is cis, so shouldn't the answer be 1?


texts: How to calculate minimum temperature of a reaction?

texts:
For burning ethanol (its reaction with oxygen), we need a minimum activation energy (a minimum temperature) to start the reaction.

Is it possible to calculate what are the minimum temperatures required for burning ethanol and methanol to compare them?


texts: Why is the net dipole moment of carbon dioxide equals zero

texts: Why is the net dipole moment of carbon dioxide equal to zero? And what is the partial charge of carbon in co2? Is it +2 because it forms two polar bonds or if they cancel the effect of each other due to their linear stereo structure then is it +1? What is the relation between being linear and having +1 partial charge? (my book says it have +1 and I couldn't understand why as I believe it is +2 because it forms 2 polar bonds so it has +1 from each oxygen atom)


texts: Easiest/Fastest way to obtain a good quantity of fine Iron powder?

texts:
I am wanting to make a reasonable quantity (10-100g) of iron powder that I can use to visualise magnetic fields (by putting the powder in a thin layer between two transparent materials).
The finer the powder and more consistent the size the better. Ideally I would like a particle size 1 micron or smaller.
I've used a very fine grit sandpaper of about 2000 grit and this had a great result but took an eternity to produce.
I also made iron powder via electrolysis with an iron anode/cathode, in an aqueous solution of iron sulphate. I used an old repurposed PC PSU to supply 3V and however many amps the PSU could output for the electrolysis.
This produced some iron flakes which seemed a bit too large for what I wanted but it made a lot of iron particles quickly and with little effort.
Main question:
Do you know of any good processes I could use to make fine iron particles using electrolysis or another chemical process?
Related side questions:
What's a good liquid medium for suspending iron particles?
Is iron the best material to use for a viewing magnetic fields? How does it compare to other materials like Cobalt,Nickel,magnetite,Tungsten (Paramagnetic), NdFeB dust, etc?
A magnetic field viewer with silvery white particles (as opposed to black particles) could look nice. What might be a good way to turn the magnetic powder more silvery instead of black?
Is there a way to produce a good quantity of very fine, needle-like rods of iron? This could also work well for visualising magnetic fields as I believe the 'needles' would want to align to the magnetic fields.
I appreciate any help you can offer me!


texts: How to study Sodium hypochlorite stability with materials

texts:
first of all I'm not not sure to be in the right stack exchange site, but I'm a material engineering student and this year I have a project: choose a material for a container filled with Sodium hypochlorite, my university has given us CES Edupack, that contains a lot of infomartion about mechanical and physical properties, but nothing about material stability.
Since we haven't done any lecture about materials stability/decomposition, I'm here to ask if there is someone that could enlight me about how to proceed to evaluate the stability of a material.The only thing that I came across while thinking about it is to avoid materials(polymers) that has got active groups with Sodium hypochlorite, is it a good approch?
EDIT
Maybe my question is a little dispersive so I make it clear here: my main concert is more general: how do I study the stability of sodium hypochlorite inside the container? What should I check to be sure that the container doesn't "melt"?


texts:
I am planning on doing some synthesis in the near future and due to safety purposes I am looking for a methylating agent that is both effective and safe. The substrate is a deprotonated amine and the solvent is water. I understand that DNA methylation is involved in the toxicity of the compounds, but there should still be ways to minimize risk. Ideally, the compound should be a powder that is soluble in water. Can any ideas that work for this substrate and solvent be thrown on the table?

I was planning on using methyl iodide solely as a last resort.


texts: Meaning of "ad" in a pharmaceutical patent: "Acetic acid ad pH 5.0"

texts:
Can the abbreviation "ad" mean "up to" in pharmacology? I saw a translator translate the Russian line "до pH 5.0" ("pH level up to 5.0") in a table describing the composition of a drug product as "ad pH 5.0". The meaning of the Russian record was "the content of the excipient in the product may be as high as to bring the product's pH to 5.0, but not higher".

I looked up a list of pharma abbreviations, and "ad" there does not have the meaning "up to".

I googled and found this on Google Patents:

  Ammonium acetate 0.77 mg Sodium chloride 7.21 mg Benzyl alcohol 10.0 mg Polysorbate 80 0.2 mg Acetic acid ad pH 5.0 0.1 q,s, NaOH 0.1 N ad pH 5.0 0.1 q,s, Water for injection ad 1.0 ml

But this is unlikely to mean "up to", yes? I wonder what the meaning is there.

To be on the safe side, I used "up to" in my translation, but now I'm curious.


texts: Why is the pKa of the thiol group in N-acetylcysteine higher then the pKa of the thiol group in cysteine?

texts: I understand why cysteine has a $\mathrm pK_{\mathrm a}$ of 8.3. But the $\mathrm pK_{\mathrm a}$ of thiol in N-acetylcysteine is 9.27. Since there is an acetyl group attached to the nitrogen, doesn't this lower the $\mathrm pK_{\mathrm a}$ via the inductive effect?


texts: How to calculate the oxidation number of sulfur in H2SO5?

texts:
I am in class 11th and I am having trouble solving the question.

  Calculate the oxidation number of sulphur in $\ce{H2SO5}$?
  (The answer is given as as $+6$.)

$\ce{H2SO5}$ exists it is named as "peroxy sulfuric acid".

How tried it:
\begin{align}
2(+1) + 1(x) + 5(-2) &= 0\\
2 + x - 10 &= 0\\
x&=\pm8
\end{align}


texts:
So I got a problem recently which asked to calculate the amount of energy needed to increase the temperature of 200 g of water from 26 to 51 degrees Celsius. The value I got was 20900 J.

So far I feel like it is endothermic because heat had to be added to the water in order for its temperature to go up, so the water essentially absorbed heat, but I'm really not sure.


texts: Use of combinations to determine number of isomers

texts:
Our teacher asked us how many geometrical isomers are possible with the formula $\ce{c2ClBrIf}$.
I answered with the logic $^4C_2=6$ and it turned out to be correct.

Is the use of combinations this way generally helpful in determining the number of possible isomers? For example, if I have a rigid molecule with three carbon atoms and six substituents (perhaps a cyclopropane), is the correct number of possible isomers 20?

$$^6 C_3 =\dfrac{6!}{(6-3)!\cdot 3!}= 20$$


texts: Separation of Regioselectively Alkylated Ionic Solid

texts:
How would one go about separating a solid mixture of regioselectively alkylated solids.  I'll give a specific example.

Take the hypothetical alkylation of methylpentazole with MeI.

There are three (3) different products possible.  How would you go about the separation of these products after recrystallization of the product mixture (with the assumption the reactants and products don't explode).

The problem is that you cannot simply distill off each part of the mixture due to the high boiling point of the solids.


texts: Vacuum distillation apparatus selection and configuration

texts:
I want to assemble a "hobbyist-level" vacuum distillation apparatus for extracting small volumes of "typical" solvents (e.g., water, alcohols, ketones, diols).

I already have standard lab glassware with 24/40 joints, 10mm barbed inlets.

How do I select a suitable pump?

I would want a pump that can run for extended periods to perform vacuum desiccation.
So far my research suggests that I should be looking at diaphragm pumps, but:
I don't know if there are other features or specifications available in a low-three-figure pump that will make life easier.
What kind of tubing do I want?  I know that larger inner diameter is better, but I don't know if something special is used instead of regular tubing to support the vacuum, or what the standard adapters and sizes are to come off the 10mm glass fittings.

What elements need to be part of such an apparatus, and how should they be configured?  E.g., I have seen mention of:

Filters: What are used, and when are they necessary?
Traps: Does this only refer to "cold traps," which I understand to simply be another condenser in front of the pump?  If so, is it correct that this would only help if I can cool the "trap" significantly below the temperature I'm using for the primary distillate condenser?
Manometers
Capillary bubblers: I can't even find anything on these, other than what's mentioned here.

Also, how do these answers change if I'm doing vacuum desiccation of the named solvents (i.e., where the only difference is I don't care to capture the evaporate)?  E.g., can I just let the system exhaust through the pump?


texts:
Could someone please illustrate how to determine the E/Z configuration of this molecule?

What I understand so far is that if the two highest priority substituent on each side are on the same side, then it's Z and vice versa.

Now, how can I handle such a structure?
I've considered it and I thought it might be $\ce{CH-CH3}$ on one side (up), and $\ce{CH2CH2}$ on the other. However, I don't think it's right.

Bottom line is that I don't understand how to fractionate the ring into two substituents.


texts:
I figured I’d study $\ce{C2O4^2-}$ as an organometallic ligand, and found that it is weak field (pi donor). I hence decided to construct a MO diagram.

The oxalate anion is of D2h symmetry, so one can immediately use that, form irreducible representations and find the C-C orbitals:

Following which, I tried to use projection operator to look at all the group orbitals.

Unfortunately, this means that there are a lot of orbitals with Ag and B2u symmetry, and a couple with B1g and B3u symmetry. How would these orbitals interact?


texts: Why is the ionic product of water not divided by the concentration of water?

texts:
I know the ionic product of water is $[\ce{H+}][\ce{OH-}]$, by following the equation:

$$\ce{H2O <=> H+ + OH-}$$

But actually it's just another way of writing:

$$\ce{2H2O <=> H3O+ + OH-}$$

Since, $K_\mathrm{w}=K_\mathrm{c}[\ce{H2O}]$ and

$$K_\mathrm{c}[\ce{H2O}]= \frac{[\ce{H3O+}][\ce{OH-}]}{[\ce{H2O}]}$$

Why can't the following equation be used? $$K_\mathrm{w}= \frac{[\ce{H3O+}][\ce{OH-}]}{[\ce{H2O}]}$$


texts: Volume change of solute addition to solvent

texts:
When making and manipulating high concentration stock solutions of sugar excipients, is there a way to predict the corresponding volume effect that occurs? I am asking in order to be able to create end solutions with exact wt/volume concentrations.

I know about partial molar volumes and some of the thermodynamics of mixing, but am wondering if there are models and/or correlations to predict the volume behavior of some of these solutions.

Thanks!


texts: Does solubility matter when measuring density with displacement method?

texts:
Can the volume of a solid (specifically a granular crystal or powder) be accurately determined using the displacement method with a liquid in which the solid is soluble?

Originally I thought by dissolving in the liquid there would (or could) somehow be a change to the density of the mixture which would affect the displacement. As such, it would be a good idea to ensure the substance is not soluble in the liquid being used to determine the solid's volume. But if the dissolution of the solid is only a physical process (i.e., dissolving sugar or salt in water), would this at all affect one's ability to measure the volume of the amount of substance added?

I guess when dealing with an unknown substance, we might not be able to easily determine if the dissolution took place as a physical or chemical process without further testing, so it would make more sense to conduct the measurement with a liquid in which the substance was insoluble.


texts: Regioselectivity of Birch reduction (electron donating groups)

texts: Why does Birch reduction on benzene derivatives with an electron donating group happen at ortho and meta positions? When the substitute is electron withdrawing, ipso and para reduction take place because the electron withdrawing group stabilizes the anion in these positions. What's the explanation for electron donating group directivity?


texts: Which ultra-high temperature ceramics make a good electrical insulator?

texts: I am looking for materials with melting point above 3,000 °C and yet is a good electrical insulator. Generally metal carbides have high melting point but a lot of them are electrical conductors.


texts: How do I write the complete and net ionic equations for Insoluble compounds?

texts:
So, I was doing my homework and had to write out the complete equation and net ionic equation for a combination of Lead (II) Iodate and Sodium Hydroxide.

So my equation is given as:

$\ce{Pb(IO3)2_{(aq)} + NaOH_{(aq)} -> ?}$

However my dilemma is that both of these compounds seem to be insolvable and I'm not really sure that I can either write the complete equation or even the net ionic equation, since I have no idea what to expect. If I do it on Wolfram Alpha I get the resulting products as:

$\ce{H2 + I2 + 2Na + 4O2 + Pb}$

However I have no idea if this is right/and or what's even going on here?


texts: Electrochromic properties of ethyl viologen

texts:
I came across this article on electrochomic displays. It mentions Ethyl Viologen as an electochromic chemical. I would like to attempt an experiment to showcase it's electrochomic properties but don't really know where to start.
First off, where to get some. Googling I came across these, three, pages. Will one of these work? If not where do I get some? Or do I need to synthesize it (if so how)?
Second, what to do with it once I have it? I take it there's more to it than just sticking some electrodes in a beaker of it.
The article states, "If the EV-molecule absorbs a second electron, EV turns pale blue. This reduction however is irreversible and definitely not wanted." What care (if any) do I need to take to avoid this?
Sorry if I ask something obvious, I'm very inexperienced with chemistry.
Thank you.


texts: How to determine the theoretical carbonic acid concentration in soda water from a Soda Stream

texts:
I've seen it cited that commercial carbonation devices like a SodaStream put about 100 psi (700 kPa) of pressure to dissolve gaseous $\text{C}\text{O}_{2}$ in to solution. I've also heard that the reason carbonated water tastes different than the water before it is carbonated is the presence of carbonic acid ($\text{H}_{2}\text{CO}_{3}$). I guess my question is a two-parter:

1) How can one determine the gaseous $\text{CO}_{2}$ concentration knowing only the temperature (assume room temperature) and the pressure (above).

2) How can one determine the carbonic acid concentration knowing only the dissolved $\text{CO}_{2}$ (g) concentration?

Is there a lit. value for the eq. reaction coefficient for this reaction at room temperature?

$$\ce{CO2(g) + H2O(l) <=> H2CO3(aq)}$$

If so, where would I find it? And could it be used to get a ballpark for the carbonic acid concentration?


texts: Is NADPH sensitive and unstable in UV light?

texts:
According to the MSDS for NADPH Tetrasodium Salt, it says to store it in a place away from heat and light. Does this include UV light or just visible light? I was told that a pure NADPH stock solution (with pH 7 phosphate buffer as solvent) could be re-used after absorbing UV light at 340 nm, but based on the MSDS it seems that shouldn't be the case. So my question is: could I reuse a sample of pure NADPH stock solution that was exposed to UV for my enzyme activity assay?

datasheets.scbt.com/sc-202725.pdf

https://www.interprise.com.br/produtos/download/90289.pdf


texts:
When I first time smell the methanol, for me it was similar to the benzene (completely different from the ethanol). But almost everywhere information says, that it should me very similar to the ethanol. (I am talking about almost dry methanol, not dissolved in water or mixed with ethanol.)

I understand, that smelling chemicals is not healthy, but kills the dosage, not the poison. The only breath won't kill anybody. (Off-course, if you are working with methanol or other dangerous compounds you must wear gas-mask and/or work with good ventilation!)

How would you describe the smell of the methanol?


texts: What analytical method(s) to use for finding the contaminations in a fatty base material

texts:
In a large batch of a fatty combustible mixture there appear to be two contaminations, since after combustion there are 2 residues clogging up the injectors and exhaust system:
- a calcium salt
- a phosphate

We can easily analyse these residues, but to find a method to remove these contaminations before they are combusted we need to find out what form they have in the base material.
From that information we could try to 'wash them out' and quantify the contamination in both the 'washing sollution' and in the combustion gasses to optimize this process.
But for starters we need to know where the contamination is comming from in the first place, so hence my question: what analytical method(s) could be used to figure out these (probably small) contaminations in this fat ?


texts: Possible erratum in solutions to Orbital Interactions in Chemistry 2ed

texts:
I was attempting the problems in Chapter 1 of Orbital Interactions in Chemistry, and found a slight problem.

ftp://ftp.wiley.com/public/sci_tech_med/orbital_interactions_2e/Chapter%201%20-%20Answers.pdf

For Q1 (d), I obtained the same secular determinant as the question. However, my answer was slightly different as solving the determinant yielded completely different answers for me.

For the question, H12 (resonance integral) was given as -14.18 eV, S12 (overlap) was given as 0.596, and the energy of the 1s hydrogen atomic orbital was given as -13.60eV. However, plugging these numbers into the secular determinant yielded me orbital energies of -18.26eV, -13.6eV and 41.07eV (the answer given was -33.657eV, -13.6eV, 6.457eV).

Here's the question, for reference. Is my answer incorrect, and if so, how is it incorrect? Thanks!

Here's the question.

Any help would be appreciated.


texts: Why does chocolate ice cream melt faster than others?

texts:
The other day I was dipping out Neapolitan(strawberry, vanilla, & chocolate) ice cream and noticed that the chocolate ice cream tended to melt faster than that of the vanilla and strawberry.  I couldn't remember in which order I dipped the ice cream so I decided to do a controlled experiment with it the next time I dipped it out.

I took three bowls of the same type/shape and dipped out the strawberry first, then vanilla, and chocolate last.  Even dipping the chocolate ice cream last showed that the chocolate ice cream would melt faster than the strawberry or vanilla.

Neither the strawberry nor chocolate use artificial coloring, though the vanilla states that it does.  Is there a reason as to why chocolate ice cream melts faster?  Is it because of the darker coloring that attracts heat or perhaps the low melting temperature of chocolate in general?


texts: Why does whey protein powder make porridge much less viscous?

texts:
When I mix whey protein powder into warm porridge (that I cooked in the microwave), the thick porridge becomes much less thick.
I searched this, and I found several forum threads discussing this too so it seems to be a common phenomenon. Happens when cooking porridge on the hob too, not just from mixing protein in after cooking.
I make the porridge through simply heating porridge oats + cow's milk. It doesn't matter if the oats are steel-cut or rolled, part of a fast-cook microwave pack, or completely natural.
How come the porridge becomes more liquidy when whey is stirred into it?


texts: Why isn't the ionic radius of Mg2+ bigger than F-?

texts: They will both have the same number of valence electrons, but $\ce{F-}$ is more electronegative. Why is it not the case that $\ce{Mg^2+}$ has a bigger radius than $\ce{F-}$?


texts: Why do Zr, Sn, and Ti enolates form syn aldols selectively?

texts:
In Organic Chemistry (2nd ed.) by Clayden, Greeves, and Warren, it is stated that (p 869)

  [...] the enolates of some metals [Sn(II), Zr, Ti] give syn aldols regardless of enolate geometry.

There are also literature examples of syn-selective Zr aldol reactions, e.g. Tetrahedron Lett. 1980, 21 (48), 4607–4610.

If they were to obey a simple Zimmerman–Traxler chair-like transition state model, as is applicable for Li or B enolates, then (Z)-enolates should give syn aldols and (E)-enolates anti aldols. How does the mechanism or stereochemical model differ for these enolates?


texts: Mechanism of chlorine disproportionation

texts:
It is a common fact that $\ce{Cl2}$ reacts to form $\ce{HCl}$ and $\ce{HOCl}$ when dissolved in water. However, how exactly does the reaction proceed?
The first step could either be that the oxygen atom in $\ce{H2O}$ attacks $\ce{Cl2}$, forming $\ce{Cl-}$, and $\ce{H2OCl+}$, which then loses a proton to become $\ce{HOCl}$.

But it could also be that chlorine attacks the $\ce{H}$ in $\ce{H2O}$, forming $\ce{Cl+}$, $\ce{HCl}$, and $\ce{HO-}$. The first reaction seems more probable (based on the products), but I am not sure.


texts: Is my teacher correct about organic compounds?

texts:
So in my chem notes its written that CCl4 , CH2Cl2 are both organic compounds as they are derived from CH4 which is also an organic compound.

It says that because CCl4 and CH2Cl2 are "derivatives" of CH4

Well...then lets say we involve CH4 in a reaction and take the product and involve the product in another reaction and then take the product of that reaction too and involve IT in another reaction and keep on doing this 10 times and then end up with SO2 does that mean that SO2 is an organic compound too?

I mean if this is the definition then ANY element/compound can be termed as an organic compound right?

Please help.


texts: What are the products formed when phenol is reacted with benzyl bromide?

texts:
What are the products formed when phenol is reacted with $\ce{PhCH_2Br}$ (benzyl bromide)?

I can think of two ways in which the reaction would proceed. One would be the formation of an ether through SN2 mechanism. The other is formation of 4-benzylphenol (Friedel–Crafts alkylation)

Which one of the two products is likely to be formed?
If both are formed, is there any preference for one being the major product?


texts: Finding time t in a first order reaction (JEE Adv 2019)

texts:
The decomposition reaction $\ce{2N2O5(g) ->[\Delta] 2N2O4(g) + O2(g)}$ is started in a closed cylinder under isothermal conditions at an initial pressure of $\pu{1 atm}$. After $\pu{Y \times 10^{3} s}$, the pressure inside the cylinder is found to be $\pu{1.45 atm}$. If the rate constant of the reaction is $\pu{5 \times 10^{-4} s-1}$, assuming ideal gas behavior, the value of Y is?

I used the equation given here for a first order reaction, $[A]=[A]_oe^{-kt}$
Using $k = \pu{5 \times 10^{-4} s-1}$, I am getting 4.606 but the answer given is 2.3.
Why is this wrong?
The question is from JEE Advanced 2019 paper 2.


texts: During monochlorination of propane why is chloropropane the major product formed. As far as I know using free radical mechanism 2-chloropropane is the supposed to be formed as the secondary free radical is more stable than a primary free radical. But the calculations involving reactivity order of chlorination tell otherwise. Why is this so!?


texts: Why does the reduction of NAD+ to NADH change the absorbance so much, and cause fluorescence?

texts:
This is an updated question:
I don't have a very strong background in biophysics, but I want to understand the theory behind $\ce{NAD+}$ and $\ce{NADH}$ absorbance and fluorescence.

Background: I understand that the additional hydrogen that $\ce{NAD+}$ gains to form the reduced $\ce{NADH}$ results in the molecule being able to absorb light at $\pu{340nm}$. And that only the reduced $\ce{NADH}$ is able to produce fluorescence. This is also the property which is explored when studying, e.g., enzyme kinetics - if the enzyme binds $\ce{NADH}$.
Question: The oxidized form, $\ce{NAD+}$, still has an aromatic ring - why is it that it is not able to fluoresce? Why, in a nutshell, is the transfer of the hydrogens causing fluorescent in $\ce{NADH}$ and such a big change in absorbance spectrum?
Also, perhaps a bit naive question, but why is it fluorescence better to measure than absorbance?
I have tried to look for articles (the old and original) that explores these properties, but I can't seem to find any that purely speak about the spectroscopic properties.


texts:
Q.) Determine the concerntration of a solution made by dissolving 10.0g of sodium chloride in 750.0ml of solution.

I did the following; 1mol of sodium chloride = 58.44

58.44*10 - 584.4g
Concentration = number of moles/volume
584.4/0.750 = 779.2 - and this is the wrong answer.

Any pointers would be appreciated.


texts: Serious introduction to the chemistry of explosives recommendation

texts:
I'm looking for a serious introduction to the chemistry (and perhaps to a lesser extend the physics) of explosives. Presupposition of basic university courses in Organic Chemistry and Thermodynamics is no problem, though it would be helpful if some of the specifics needed to understand subsequent material would be briefly outlined as a reminder (e.g. in an introductory chapter). Sadly this search is quite hard because of all the Uncle Fester and like trash clogging up search results. To be clear, that is absolutely not what I'm after. I want an academically oriented introduction, not some "recipe" book.

A book that more or less resembles (I guess) what I'm after is The Chemistry of Powder and Explosives by Tenney L. Davis. However, it is over 70 years old and might be a little to advanced for me (might, I just don't know without some guidance).

Every help is appreciated!

PS. I actually found an online copy of the book I mentioned. It does not look really theoretical?


texts: What does metals form when they react with water,for instance sometimes they form metal oxide but sometimes they form metal hydroxide.so how does this vary


texts:
Mercury is toxic. It forms amalgams and inorganic mercury compounds/salts are available.

My question is on toxicity. I am interested in its toxicity, not the mode of action (as it will be part of biology SE)

Is amalgam toxic? (sort of yes / no)
Mercury salts are toxic? (sort of Yes / no)
If mercury salts / amalgams are non-toxic, what makes them non-toxic. Is it because of the ionic nature / other metal or any other reason?


texts: I am learning about 'cathode ray discharge tube'. I know when electrons are given out from cathode, they travel to anode, because anode being positively charged attract those electrons and continue to accelerate those electrons. When the electron hit any of the gas atom in tube, it helps to knock out electron from it and therefore, electron knocked also start moving towards anode. But i think that one stage would come when there are no electrons left with gas atoms those can be knocked out and when electron hits the gas ions, it would just slow down the electrons(emitted by cathode) and eventually leading to no ray at the end.


texts: Reaction between sodium carbonate and water

texts:
In this Wikipedia article, it mentions:

  As the concentration of sodium carbonate increases, it undergoes
  hydrolysis to form sodium hydroxide.
  $$\ce{Na2CO3 + H2O → 2NaOH + CO2}$$

Because this occurs in boilers, I can assume that it requires a heat of no more than 100 degrees Celsius. Why is this process not used when commercially producing $\ce{NaOH}$, rather than the chloralkali process?

Possible reasons:

Not enough concentration of sodium hydroxide is formed
The sodium hydroxide is contaminated with significant amounts of sodium carbonate
The reaction is too slow


texts: Is there a way to turn cellulose into sugar at home?

texts: I know that once you have sugars, you can ferment, distill, and dehydrate to create 95+% ethanol. I've also read about cellulosic ethanol, with the new step there being the breakdown of the cellulose into simpler sugars.  Is there a relatively cheap way to do that yet, or it still only in expensive research labs?


texts: Does IUPAC nomenclature have the ability to name all organic compounds?

texts:
We all know about IUPAC nomenclature. There are rules to name straight chain compounds, cyclic ones, polycyclic ones, ones with functional groups, and so on. But I have come across several examples of compounds which I simply cannot name, most of them being pharmaceutical drugs. Take the heme group complex in hemoglobin:

I'm not sure, but systematic nomenclature appears not suitable to name this structure. A popular antacid, Zantac, also known as ranitidine has this structure:

Can compounds like these even be named systematically using IUPAC rules?


texts: how do i synthesize (E) 2-methyl-1-phenylpent-1-en-3-one?

texts:
i need a way to synthesize the (E) 2-methyl-1-phenylpent-1-en-3-one
it's 2 days and still i can't find a solution.


texts:
Here is the question:

We have to find the order of their acidity.
Here is my thought process:
We check the acidity order by finding which conjugate base is more stable. Thus we remove $\ce{H+}$ from all of them. One question I have here is that in (IV), from which position should I remove $\ce{H+}$? Will it be the position from where resonance can take place or from the middlemost carbon?
In (I), (II), and (III), resonance can take place in all of them after removing $\ce{H+}$. Resonance will be more in (II) and (III) than in (I).
Conclusion:
(II) and (III) are more stable than (I). I am uncertain about the stability between (II) and (III) and about (IV).
Please tell me if I have been wrong somewhere and how I could proceed further...


texts: Chemical Equilibrium - Why do changes in pressure cause a shift in the ratio of products and reactants?

texts:
I understand Le Chatelier's principle and how every change to an equilibrium system causes an opposing reaction from the system. I also understand how, when pressure is increased, the equilibrium shifts to the side with the lowest number of moles of gas and vice versa.

So, why does this happen? How is it more energetically favourable - or is it something else?

Also, are these explanations of why the ration changes for the other factors right:

Temperature - equilibrium moves to the endothermic side of the reaction as temperature increases because the activation enthalpy of the exothermic reaction increases as the overall energy of the system is less
Concentration - ratio of products/reactants changes immediately after one part of the reaction's concentration increases, it then approaches the same ratio (assuming one whole side of the reaction is added)
Catalysts do nothing more than decrease the time it takes to reach equilibrium as they catalyse both sides of a reversible reaction and reduce the activation enthalpy


texts: How to distinguish two molecules with same formula but different geometry with vibrational spectroscopy

texts:
There is a sample that we know is all made up by only one of these two molecule:

how you can see they have the same formula but two different geometries. The question is if it is possible to know by which of these two molecules the sample is made with an experiment involving vibrational spectroscopy (IR or Raman). The following is a quite wide answer I gave to myself but I'm not sure it is right, so please correct me or confirm what I have written.
We know that if we are considering small oscillations, the vibrational part of the wave function of a molecule with $N$ atoms is the product of $3N-6$ quantum armonic oscillators eigenfunctions, and we also know that in a classic way to proceed the nuclei can move in $3N-6$ differents normal modes. Fixed one of these normal modes, if it is for example IR active, we know that all the $3N-6$ oscillators moving in that normal mode can absorb photons from the external radiation. So if the external radiation has a frequency band enough large to contain all the proper frequencies of the oscillators, we'll notice $3N-6$ absorbtion lines. While if we are considering a not IR active normal mode of course we won't see any absorbtion lines. In general the nuclei of a molecule move on a linear combination of all the normal modes. So we can think that each IR active normal mode of the combination gives the same $3N-6$ lines while each not IR active mode gives zero lines. So I would expect to observe for my real sample 12 absorbtion lines (I am not considering overtones and the noise of the media) which correspond to the proper frequencies of the oscillators. So since the two molecule have exactly the same oscillators (it only changes their position), I should observe the same 12 lines on both cases, so I'd say that it is not possible to distinguish between the two. The same argument can be used for the Raman. However I'm almost sure that I'm wrong and a way there must exists.


texts: What properties does a solvent with a high dielectric constant have?

texts:
My professor commented that water has a higher dielectric constant than alcohol.

Okay, but on what basis?

He didn't elaborate; he asked us which one seemed "more electric" and most answered water. I guess from intuition.

But why exactly is water "more electric"? I think it has to do with the relatively high extent of auto-ionization in water, correct? Alcohols are generally less polar than water and thus cannot stabilize ions as effectively as water can. And I've even seem some computers submerged completely in oil. I'm guessing that only works because oil doesn't ionize much and thus isn't able to conduct a lot of electricity - or enough to short out any circuits.


texts: Is chirality a physical or a chemical property?

texts:
In my opinion, it should be both, because it will affect the way in which a molecule will interact with plane polarized light (physical), but also affect chemical interactions such as receptor binding.

On the other hand, consider $\ce{CHDBrCH3}$, which is chiral, as there 4 distinct groups attached to the central carbon. This would insinuate that chirality is a purely physical property, as despite deuterium having the same chemical properties as hydrogen, we are able to form a chiral molecule.


texts: Calculating the molarity of DNA in a cell

texts:
In the following questions use a value of 3 for $\pi$, $6 \times 10^{23}$ for Avogadro’s number and $660$ for the molecular weight of $\pu{1 bp}$ of DNA. The volume of a sphere of radius $r$ is $4/3\,πr^3$. A bacterium has a single copy of a $\pu{4 \times 10^6 bp}$ circular genomic DNA.
If the diameter of this spherical cell is 1 micrometer, what would be the molar concentration of DNA in this cell?

The volume comes to be $\pu{2 \times 10^{-5} L}$.
Amount of substance is $\pu{6.7 \times 10^-18 mol}$.
Dividing this by the volume, my answer comes $\pu{3.3 \times 10^{-13} M}$, but the answer given in my book is $\pu{3.3 \times 10^{-9} M}$.


texts: Why do polarizable nucleophiles favor SN2 over E2?

texts: Weakly basic ions and polarizable bases favor $\mathrm{S_{N}2}$ over $\mathrm{E2}$. Why? The argument used that polarizable nucleophiles form bonds earlier, stabilizing the transition state, can be applied to either $\mathrm{S_{N}2}$ or $\mathrm{E2}$.


texts: What does the "total energy" of a molecule mean for the Chem3D MM2 minimized energy calculation?

texts:
I was fiddling around with Chem3D and the MM2 calculation for finding a molecules minimized energy.

Benzene was assigned a total energy of -0.5741 kcal/mol while biphenyl was assigned a total energy of 4.5397 kcal/mol.

What is the "total energy" relative to? In other words, why does benzene have a negative total energy while biphenyl has a positive total energy? What is the 0 energy state that they are being compared to?


texts: Aren't two last steps superfluous? I just do not see how the fourth and last forms differ.


texts: Why conductivity of electrolyte decreases on dilution, but molar conductivity increases?

texts:
I learnt that on dilution of an electrolytic solution, it's conductivity decreases. However, there is an increase in the molar conductivity of the solution. The book explained the reason by comparing the definition of the two terms. However, it gave a hypothetical example which contradicts the statement it earlier stated. Maybe there is a printing error, but it has got me confused now.

Can someone please explain why the conductivity of an electrolytic solution decreases but molar conductivity increases on dilution, maybe with the  help of a good hypothetical example?


texts: Precipitation of Calcium ions in basic Sodium Hydroxide solution?

texts: I recently conducted an EDTA titration of milk to find its Calcium contents. I got a value significantly smaller than the theoretical value. (≈10 times smaller). I made $50ml$ samples to which I added $2ml$ 8M NaOH to precipitate any Magnesium ions. However, assuming milk is neutral, this would make the pH of the sample equal to $13.5$. Would this cause precipitation of Calcium? If so, how could I calculate the extent of this? I know it has to do with solubility, but it is not a part of the curriculum at my school, and after a long research, I am still lost. I would really appreciate the help.


texts: Where does the rate equation come from? (r = k [A]^x [B]^y)

texts: Equations are great, but they're much better when you can understand them. I don't quite get why this works. Could someone explain it to me?r = k [A]^x [B]^y


texts: How does NaCl (or any inorganic salt) increase surface tension?

texts:
Does the compound "prefer" to stay in the solution?
If yes, wouldn't the surface tension of the solution be equal to that of pure water, since only water is in the surface?

See: Does NaCl reduce the surface tension of water?

Or is the compound distributed evenly and because the ionic bonds are stronger than the attractions between water molecules, the surface tension increases?

Read here a reddit answer to why do ionic compounds such as NaCl increase the surface tension of water?

Explain like I'm 5 please.


texts: Given advancements of computational power an machine learning, how is it still not possible to predict products from chemical reactions?

texts: Given that it seems every answer to this question is that it is "impossible to predict the outcome of a chemical reaction." Is chemistry just trial and error? Given how fundamental and revolutionary a simulator capable of predicting possible outcomes of a reaction would be, why has it not been done yet? Do you think it will ever happen?


texts: How to use the calculate velocity correlation from VanHove correlation?

texts:
I am trying to derive an expression for the velocity correlation function $C(t) = \langle \mathbf{V}(t) \mathbf{V}(0)\rangle$ from the VanHove correlation:

$$
G(\mathbf{r},t) = \frac{1}{N}\left( \sum_{i,j} \langle  \delta(\mathbf{r}- \mathbf{r}_i(t) +\mathbf{r}_j(0)   \rangle \right)
$$

However I am not sure how to get the time dependency and the $\dot{\mathbf{r}}(t)$ from the VanHove correlation. The average $\langle\rangle$ is over the ensemble.

I tired to figure out how to derive a term for velocity autocorrelation from the original paper, but without any luck.


texts: How do I run MP2 and/or CCSD-level hyperpolarizability calculations with GAMESS?

texts: I have used GAMESS before for TDHF (RPA) / TDDFT level first hyperpolarizability ($\beta$) calculations. However, I cannot figure out how to calculate $\beta$ with MP2 and CCSD for comparative purposes. Do I have to use the FFIELD keyword for the finite field approach? If that is the case, what is the general workflow necessary to calculate the time-varying hyperpolarizability?


texts: What does reaction exothermicity say about the stability of molecules

texts:
If a reaction is exothermic it means that the energy state of the products is lower than that of the reactants so this will be the state that 'nature' will naturally strive for. Often you see that stability of molecules is argued in this way (e.g. in one of the answers here), saying that the higher the exothermicity of the decomposition reaction, the more unstable the molecule and thus the more unlikely that it will exist in nature.

My question is whether this reasoning is correct?

The reason I am doubting this, is that the reaction enthalpy $\Delta H_r$ is not the only parameter of importance in the energetics of chemical reactions: the activation energy $\Delta E_a$ can also play a major role. To clarify my point, take a look at the diagram for 2 hypothetical reactions I have made. Reaction 1 has a low activation energy and a low exothermicity, whereas 2 has a high activation energy and a high exothermicity.

Judging solely by exothermicity you would conclude that the reactants of reaction 2 are more unstable, but if you look at the activation energies for the reactions than I would argue that the reactants of reaction 1 are more unstable because they more easily react to form their products. Of course having a high activation energy would at best make the reactants meta-stable, but metastability could last for decades as well given the right conditions.

So my general question is: can reaction exothermicity be used to say something about the stability of molecules and what is the role of activation energy in this story?


texts: Is the refractive index of a solution of four substances the median of the four substances' refractive index?

texts: I need to determine the purity of a solution and we need to discuss about the  'theoretical' refractive index of the substance that we are supposed to have.


texts: Concentration of gas in water: What is the time derivative of concentration toward steady state?

texts: The Henry's law gives the steady state concentration for a gas in water. But it does not tell about the speed for this to happen if the concentration is not in steady state. What is the time derivative of concentration of oxygen in gas?


texts:
What may seem to be a silly question could actually have roots in some core chemistry principles. The other day, I was cooking fish when I noticed that I'd forgotten to use a fork, and touched the fish with my bare hands. When I tried to get rid of the fishy smell, it just wouldn't go away.

Why are some smells so hard to get rid of?

My Hypothesis:

I think that the phrase "hard to get rid of" really means "resistant to washing," because that's what we're actually thinking of when we say you can't get rid of a smell. And when we say "wash" we really mean "attempt to dissolve in water using soap emulsification".

I'd conclude that "a smell being hard to get rid of" is caused by chemicals that are not soluble in water, and for some reason, possibly because the molecules are too large to fit in a stable emulsive bubble, refuse to be emulsified into aqueous suspension by soaps. But that's just my theory.


texts: On the unit of standard reduction potential and its independence of elements involved

texts:
Why is the standard reduction potential in units of volts (Joules/coulomb)? What does this tendency of a material to reduce has to do with the charge in coulombs?

Also, why this number doesn't depend on which elements the reducing material is interacting with? (which material gets oxidized)


texts: Why is direct addition not preferred in this reaction?

texts: According to HSAB, direct addition is more preferrable in this reaction with the hard carbonyl carbon electrophile and the hard grignard reagent. But answer given in my book is that with 1,4- addition. I would like to know why 1,4-addition is done here? Thermodynamic control? But I don't think the reaction is reversible.


texts:
Recently the IUPAC added four new elements to the periodic table and it seems the race for discovering new elements is just getting faster. I was wondering if a "last element" exists; an element with so great an atomic number that it would be impossible to make anything larger.

There should probably be a bound placed on the maximum number of protons in an atom by quantum theory. Because, elements with extraordinarily large an atomic number should become so unstable that it would impossible for them to come into existence(in theory).

I do not know quantum theory so I am not sure; but is there such a possibility? Or the number of elements created is just limited by our current technology and the energy of our particle colliders meaning that this race will never end?