texts: How good is 2-Butoxyethanol as a replacement for acetone?

texts:
I have recently bought a bottle of acetone from my local hardware store. When I opened the bottle, I was surprised about the absence of the strong smell of acetone. Only then I discovered the smaller printed words "Eco replacement" on the label:

On the backside, the bottle indicates the constituents as:

2-Butoxyethanol
< 10 % anionic surfactants

I compared the chemical composition and characteristics of 2-Butoxyethanol and acetone. To the eyes of a non-chemist, they are very distinct substances. Both are very good solvents, 2-butoxyethanol seems less toxic than acetone. I am happy to believe that 2-butoxyethanol can replace acetone for very many applications, but I fail to find any application notes about 2-butoxyethanol as an acetone replacement.

My question is about the limits. Are there applications where 2-Butoxyethanol fails to replace acetone?

If this is too broad as a question, I would like to narrow it down to the two applications that I am really interested in:

use as a cleaner before applying glass fiber reinforced resins (epoxy or polyester). Acetone is usually used because it solves many polymers, but leaves polyester intact.
use to "rejuvenate" PEI (polyetherimide) coated heat beds for 3D printing. The materials to be removed from such heat beds are the printing materials (including PLA, PETG, and ABS), as well as glue stick residues, and body grease.

Is 2-Butoxyethanol a good choice for these uses?


texts:
I'm trying to apply conjugate theory, which I can apply very well to acids/bases, to redox. Can you verify my logic, which I have broken down below?

1) I know that solid sodium is a strong reducer.

2) I know this because solid sodium when placed in water reacts violently, forming, among other products, sodium ion.

3) Reducers are oxidized. Reducers lose electrons. Correct; $\ce{Na^{+}}$ is the product of placing solid sodium in water.

4) So in this half-reaction: $\ce{Na<=>Na^{+} +e^-}$, sodium is the reducer. $\ce{Na^{+}}$ is the conjugate oxidizer.

5) Oxidizers are reduced. Oxidizers gain electrons.

6) Because sodium is a strong reducer, which means it has a strong tendency to be oxidized, or a strong tendency to lose electrons, its conjugate oxidizer must be weak. Oxidizers are reduced; oxidizers gain electrons. The potential for $\ce{Na^{+}}$ to gain the electron that $\ce{Na}$ just lost must be small, or $\ce{Na}$ would not be a good reducer.

7) Therefore, a strong reducer's conjugate oxidizer must be weak.

8) Likewise, a strong oxidizer's conjugate reducer must be weak.

9) Likewise, a weak reducer's conjugate oxidizer must be strong.

10) Likewise, a weak oxidizer's conjugate reducer must be strong.

Also, if anyone could point me to a good reference on gaining insight into redox, tha would be great!

And while we're on the topic of redox, what's the mechanism for this reaction? Are both bonds cleaved homolytically? I see how the nucleophilic chlorines attack the electrophilic hydrogens but how's the bond broken?

$\ce{H_2 + Cl_2 ->2HCl}$


texts: Why does a Beckmann Rearrangement not occur in the in nitrosation of cyclohexanone?

texts: In my textbook Organic Chemistry, 2nd edition by Clayden, on pg. 464 it states the addition of $\ce{NO2-,HCl}$ to cyclohexanone to 2-nitrosocyclohexanone, which hydrolyses to 1,2-cyclohexadione. Why does the Beckmann rearrangement not occur in 2-nitrosocyclohexanone instead?


texts:
If I combine two p orbitals in such a way that they form σ bonds, which linear combination will represent bonding and antibonding?

My work on this problem:

$$
\begin{align}
&\text{Bonding:} &(\phi_1 - \phi_2)\\
&\text{Antibonding:} &(\phi_1 + \phi_2)
\end{align}
$$

where $\phi_1$ and $\phi_2$ are the wavefunctions of 1st and 2nd p orbitals.

Reason: While forming a bond, in bonding combination two lobes of same phase will overlap so they are actually mirror images of each other, and therefore they are negative of each other.
While in antibonding combination opposite phase combine, so the wavefunctions are actually added.
Is this correct?


texts: What, if any, hydration states does sodium bicarbonate have?

texts: Sodium carbonate has a few hydrates in addition to the anhydrous form. I haven't found any references online that assert any hydrates of sodium bicarbonate though. Do they simply not exist?


texts: Is there any non-toxic and non-solvable-in-air liquid?

texts:
I want to heat the air with non-aqueous, non-toxic and non-solvable-in-air liquid (with very low relative pressure in air). Is there any such liquid exists?

It would be great if the boiling point of the liquid would be 110 °C.


texts: What is the arrangement of water molecules in a hydration shell around an anion?

texts: I believe I read somewhere that the hydration shell of ions always has hydrogen on the outside, but I can't relocate the exact whereabouts of this. Thus, I decided to ask here, as to what the arrangement of the water molecules around a anion is (is it both hydrogens pointed inwards to the ion or if one is facing outside, one is facing inside).


texts:
I have been making a formulation of roughly 50/50 MEA triazine (CAS no. 4719-04-4) and 37% formalin, with a <1% of a benzalkonium chloride.
The formulation has been pretty stable, but it has occurred that after being subjected to strong agitation it suddenly starts reacting increasing the temperature to more than 100ºC and giving off fumes that smell very strongly like amine.
What I mean by strong agitation is the sloshing of transporting it in a tanker truck filled up to 70% of its capacity and/or filling a tank from the top letting a stream of the product fall the height of the tank.
Thanks!


texts: Why is the maximal percent concentration of acids similar to their molar mass

texts:
Why is the usual percent concentration of a concentrated acid's solution similar to its molar mass?

For example:

                FW (amu)     mass %
sulfuric        98.08        98%
nitric          63.00        68%
hydrochloric    36.46        36%

Is there some reason for this similarity or is it coincidence?


texts: Is it possible to light a match by scratching it on hard surfaces, like they do in movies?

texts:
In movies cool guys don't need a matchbox − they just light a match by scratching it on whatever hard surface − concrete walls, wooden bar tables, leather belts, etc. Is it just a movie trick, or is there actually a type of matches you can do that with?

So far I've tried scratching usual matches on a ton of different surfaces and the heads just smear without even a smoke.


texts: Is it true that a pH higher than the pKa of an acid make the H automatically disassociate?

texts: Will the hydrogen atom always disassociate if the pH of the solution is higher than the pKa of the acid?


texts: Can a very high concentration of hydrogen peroxide, inhibit or denature the enzyme catalase?

texts: My experiment, where I am investigating the effect of increasing substrate concentration of hydrogen peroxide on enzyme activity hasn't worked out as I hoped. The last result, highest concentration of hydrogen peroxide, shows a decrease in enzyme activity compared to the lower substrate concentration and I don't understand why?


texts: Why is enthalpy change = heat change only for constant pressure?

texts:
Please help me, a mathematician doing his elective course on Physical Chemistry, out with this very simple question: why does the relation between enthalpy and heat $$\Delta H = \Delta U + p\,\Delta V = \Delta Q$$ hold only under constant pressure? With the integral definition of work, couldn't one just as well write $$\Delta H = \Delta U + \int_{V_i}^{V_f} p(V)\,\mathrm dV = \Delta Q $$ in the case where the pressure is not constant during expansion?
I'm still having some trouble with chemical notation of derivatives/infinitesimals as well as with the physical realities behind the formulae, so there might any number of basic things I'm missing here.
Thanks in advance. Also as this is my first question here, apologies if I did anything wrong or if I missed a similar question.


texts: Effect of increase in volume of container on concentration of chlorine at equilibrium conditions

texts:
How the concentration of the chlorine would be affected if the volume of the container is increased?
  $$\ce{4 HCl + O2 <=> 2 Cl2 + 2 H2O + $Q$}$$

My initial thought was that the total and partial pressures were decreased on increasing the volume of the container. But I did not account for the fact that the $\ce{HCl}$ did not play a role in this pressure.

So, according to my previous process, the reaction should proceed in the backward direction, concentration of $\ce{Cl2}$ should decrease. On the other hand, if we exclude the $\ce{HCl}$ factor, the reaction should proceed in forward direction increasing the concentration if $\ce{Cl2}$.

Please help me understand what will be the actual effect.


texts:
Copper is a metallic element, so it is likely to be?

A. Poor conductor of electricity       B. A substance with a low melting point      C. Malleable     D. Poor conductor of heat     E. An element that forms negative ions

For me, C should be the only right. But are metallic elements really likely to be malleable?


texts:
I have named this according to the numbering shown as
3-ethyl-6-(1-methylbutyl) oct-2,4-diene-7-ynenitrile.
But my book's answer key says
3-ethyl-6-ethynyl-7-methyl deca-2,4-dienenitrile
This means it has taken the triple bond as a side chain. But IUPAC rule says that the chain with maximum number of double and triple bond is taken even if it is shorter than a chain with lesser double or triple bonds. Which answer is correct and why, for the given example?


texts: Products which adhere to human nail while still being removable/reusable?

texts:
I am at loss as to what I can use for my project. I require a product which can adhere to the human nail (not any damaging glues) while still being easily removable. There will be a degree of 'overlay' on the nail so it's going to need to cover the entire nail plus a bit more (maybe seen with fake nails?).

I've looked online and video tutorials on adding fake nails isn't convenient (while it could work). My biggest problem is I don't want to damage the nail so I can't use any popular practices often seen in beauty salons.


texts:
I would be interested to know people's opinion on the following matter.

Background

Often, when the far-from equilibrium behaviour of a chemical reaction system is analysed mathematically (in papers or text books), the system is placed in a gradient between a fixed non-zero concentration of "resource" species, and a fixed concentration of "waste" species (which is often zero). The other species in the reaction system are designated as "intermediates", and it is their behaviour which is of prime interest.

For example, for the oscillating Lotka-Volterra reaction system:

$R + X \rightarrow 2X$

$X + Y \rightarrow 2Y$

$Y \rightarrow W$

Species $R$ and $W$ are the fixed concentration resource and waste species respectively, and species $X$ and $Y$ are the (oscillating) intermediates.

Question

It appears as if these reaction systems are being studied in a physical scenario which could not be realised in the lab, a magical reaction tank if you like.

The two reasons most often stated as to why resource and waste are held at constant concentrations, whilst the intermediates can vary, are that:

1) The reaction takes place in a large reservoir, where resource is abundant and where any waste produced by the reaction quickly diffuses away into the vastness

or

2) The reaction has resource species quickly "pumped in" by some external agent, and likewise waste species quickly "pumped away".

My problems with these explanations are as follows:

If in explanation 1, a very large reservoir is keeping resource and waste species at constant concentration, then if follows that the intermediate species can never reach any appreciable concentration, for they too exist in the same large volume. In other words, if the waste diffuses away, then why don't the intermediates?

Conversely, in explanation 2, if a pumping process is artificially maintaining resource and waste concentrations, it is hard to see how this pumping process is being "micro selective" in completely removing the waste compounds, but leaving the intermediate compounds totally unaffected.

More physically realistic models of chemical reactions can be made by also explicitly including the reactor in the model - for example by considering the reaction as taking place in semi-permeable compartments or in bulk in a CSTR. However, additionally modelling the reactor often changes the mathematical properties for the "bare" reaction reported in the literature (for example, in a CSTR, the intermediates as well as the waste are removed).


texts: Can a chiral molecule be optically inactive?

texts: Does there exist a chiral compound with zero optical activity? It seems possible that for some (chiral) arrangement of atoms, the optical activity of one section of the molecule could be exactly compensated by another section of the molecule, even if these two sections are not mirror images of each other. Although this is just a mathematical coincidence, does any chiral molecule have an optical activity of exactly zero?


texts:
Is there a tendency that could be used to generally forecast how a double salt might dissolve in aqueous medium compared to the simple salts of its constituents?
Example:
There is metal A, metal B and acid C.
The solubility of AC and BC are known. Could one use these as a rule of thumb to know what to expect from the solubility of say ABC?
Would it (1) Be fairly in between the solubilities of AC and BC? (2) Be fairly close to that of the least soluble among the two (3) Be fairly close to that of the most soluble among the two, or could it (4) exceed or lie beneath the solubility of the least soluble of the two?
Poutnik enlightened me on factoring in the possibility of double salts in another question which prompted this interrogation in my mind so I thought I'd make a separate question specifically for this topic.


texts:
What percentage of deuterium might be removed from water after a typical electrolysis procedure? From a post on this site I read that, "In the first stage, $\ce{NaOH}$ solution (initially $0.5\rm{M}$) is subject to electrolysis, until only $\frac{1}{32}$ of the original volume remains. This increased the original concentration of deuterium by a factor of $12$."

This seems to be, for the electrolyzed hydrogen, an approximate $38\%$ decrease from the original concentration. If we assume the original concentration was $150\rm{ppm}$ then after the first pass, we might expect to have $93\rm{ppm}$ in the deuterium reduced hydrogen. If my estimate is valid, may I expect that each successive pass would reduce the deuterium content by a similar percentage?


texts: How thick is the colored oxide layer on heat treated stainless steel?

texts:
When stainless steel is welded, or just heat treated, it will develop a thicker oxide layer, which in some cases is is rainbow colored, but can become so thick as to appear almost black. From the colors (diffraction effects, I assume), the nicer-looking layers must be on the order of a wavelength of light. Is there any more numerical information on their thickness?
Follow-up question: The colored oxide layers can be removed with a pickling paste (based on HCl) or a passivating cleaner (based on HNO$_3$ plus HF), but the resulting surface is much rougher than the original. Well, it is observably rougher if the original surface before heat treating was mirror-smooth. We call the new surface satinized. Is there any simple way to estimate surface roughness/surface area of the satinized surface?
Further follow-up: would the surface chemistry be expected to change due to the surface area increase (perhaps like shiny Pt vs platinized Pt (~340 mV): https://en.wikipedia.org/wiki/Platinum_black


texts: Is there a practical re-use value gained by grinding up activated carbon that is spent/saturated?

texts:
I want to buy bulk activated carbon for use in a DIY air-filtration set-up, like this, to improve air quality in my bedroom.
From what I understand, the relatively larger sizes of carbon media on the market are optimal for air filtration to maximize the amount of time the air is in contact with the carbon.
My question is, once my activated large-granule carbon is used up, say after a few months in my air filter, am I throwing away any untapped potential? Specifically, is there value in further crushing/grinding the carbon and then putting it into another application optimized for the new, more fine-grained size-- perhaps a water filter, or an air filter where the carbon is in a long tube, and air is moving slowly through it.
The same FAQ suggests it is impractical and messy to grind up the AC, but it seems to me that mess can be contained with a bit of planning. I'm also happy to be pointed to general resources that are helpful, especially if I'm barking up the wrong intuition trees, here. Thanks!


texts: Is it possible to efficiently convert hydrogen to methane?

texts:
According to this wikipedia page, hydrogen can combine with the carbon found in carbon steel to form some methane inside the steel, weakening it. Is is possible to convert hydrogen to methane by putting it through
graphite powder or activated carbon?

Note that I mainly want the reaction to occur at STP. The flow of the
gas through the graphite will be very slow (at the speed it is generated by electrolysis), so
maybe catalysts not needed?

The purpose of this is to form a more energy-dense fuel than pure hydrogen. Also, it will be much safer since methane is less flammable.


texts: Joule–Thomson effect: why does temperature decrease during expansion

texts:
When a gas under a high pressure in a piston (isolated from surrounding is allowed to pass through a valve), why does its temperature decrease once during expansion?

I haven't still studied thermodynamics but would like to know why exactly the temperature decreases.

Is it because under high pressure the heat was concentrated under small volume once expanded the heat is distributed?

Once the gas molecules are allowed to expand through the valve its kinetic energy increases. Where is the source of energy coming from, is it from its internal energy?


texts: Why is a strong acid like $\ce{H2SO4}$ used for imine formation here instead of a weaker acid like TsOH? I thought that if the pH was too low, the amine molecule would get protonated to an ammonium, which are not nucleophilic?


texts: How did Michael Faraday melt Sodium Chloride?

texts:
Michael Faraday melted sodium chloride in a silver spoon and ran an electric current through the molten salt, which released chlorine as a gas and left pure sodium behind.

Sodium chloride melts at $800\ \pu{^\circ C}$. How did Michael Faraday melt the salt?

*I know he invented the bunsen burner, but did he use that?


texts:
Could anyone please help to find the height of the potential barrier between silver and copper or $\ce{Ag-Cu}$. I am working on a piezo-resistive sensor based on copper fabric and silver electrodes. I was wondering if I can validate my experimental results with the model given by Zhang, X.-W., et al. [1]

I am not a chemistry expert and have a little knowledge on the height of the potential barrier. It would be highly appreciated if anyone could help me with providing the value for the height of the requested potential barrier.

[1] Zhang, X.-W., et al., Time dependence of piezoresistance for the conductor-filled polymer composites. Journal of Polymer Science Part B: Polymer Physics, 2000. 38(21): p. 2739-2749.


texts:
The most important are π orbitals as they are lower in energy than σ orbitals and the carbonyl group (C=O) is the most important of these—indeed it is the most important functional group of all. ~Clayden, Chapter 5

Why is it that Carbonyl Groups in organic chemistry are given so much importance? I am still in highschool, and at this level every book (like Peter Sykes, Solomon, Clayden) or my teachers, all talk about how Carbonyl compounds are the most important. But why is it? Why are they given so much importance?


texts: Would all wooden materials have the same density? Why or why not? (Examples may help). I have the following solution to the question: No, not all wooden materials would have the same density. Due to the makeup and properties of the components found inside certain wooden materials.


texts: Dependence of rates of neighbouring group participation on length of alkyl chain

texts:
On the topic on neigbouring group participation, it is mentioned in Carey & Sundberg (2007)[1] that the effectiveness of the participation is dependent on on the ease with which the molecular geometry required for the participation can be attained. The example of the cyclization of ω-hydroxyalkyl halides was then given:

  The rate of cyclization of ω-hydroxyalkyl halides, for example, shows a strong dependence on the length of the chain separating the two groups.

To prove the point, they showed the data for the solvolysis rates for ω-chloro alcohols with various chain lengths. Clearly, when a 5-membered ring is form, the rate of reaction is fastest. This is reasoned with the fact that a 5-membered ring has relatively little ring strain and thus, the rate of forming it would be relatively higher. However, this analysis does not seem to be convincing. If this reasoning was indeed correct, then wouldn't the next member in the series, with the capability of forming the 6-membered ring, have a higher solvolysis rate?

\begin{array}{|c|c|c|c|} \hline
\text{Substrate} & k_\mathrm{rel}{}^\text{[2,3]} \\ \hline
\ce{Cl(CH2)2OH} & 2000 \\ \hline
\ce{Cl(CH2)3OH} & 1 \\ \hline
\ce{Cl(CH2)4OH} & 5700 \\ \hline
\ce{Cl(CH2)5OH} & 20 \\ \hline
\end{array}

In general, why doesn't the rate increase as the alkyl chain increases in length, based on the reasoning using ring strain in the intermediate? We see that 3-chloropropanol is also another outlier.

Additional information

It seems that the relative solvolysis rates of ω-methoxyalkyl p-bromobenzenesulfonates also follow the same trend, with the rate peaking with the formation of the 5-membered ring.

\begin{array}{|c|c|c|c|} \hline
\text{Substrate} & k_\mathrm{rel}{}^\text{[4]} \\ \hline
\ce{CH3(CH2)2OSO2Ar^*} & 1 \\ \hline
\ce{CH3O(CH2)2OSO2Ar} & 0.28 \\ \hline
\ce{CH3O(CH2)3OSO2Ar} & 0.63 \\ \hline
\ce{CH3O(CH2)4OSO2Ar} & 657 \\ \hline
\ce{CH3O(CH2)5OSO2Ar} & 123 \\ \hline
\ce{CH3O(CH2)6OSO2Ar} & 1.16 \\ \hline
\end{array}

*The first entry shows the rate of solvolysis without any neighbouring group participation from the methoxy group.

References

Carey, F. A., & Sundberg, R. J. (2007). Advanced Organic Chemistry Part A. Structure and Mechanisms (5th ed.). Springer.
Capon, B. Neighbouring group participation. Q. Rev., Chem. Soc. 1964, 18 (1), 45–111. DOI: 10.1039/QR9641800045.
Richardson, W. H.; Golino, C. M.; Wachs, R. H.; Yelvington, M. B. Neighboring oxide ion and fragmentation reactions of 1,3-chlorohydrins. J. Org. Chem. 1971, 36 (7), 943–948. DOI: 10.1021/jo00806a019.
Winstein, S.; Allred, E.; Heck, R.; Glick, R. Neighboring methoxyl participation in solvolytic nucleophilic substitution. Tetrahedron 1958, 3 (1), 1–13. DOI: 10.1016/S0040-4020(01)82605-3.


texts: NMR spectrum of cyclohexanol - hints on integration

texts:
I've been given this NMR along with the IR and Mass Spec and assigned the task of figuring out the unknown compound. I know that it is cyclohexanol and by analysing the NMR I know that the peak at around 2.8 is the OH and the peak around 3.6 is the deshielded CH. However I can't pair up the other protons and the peaks between 1-2 ppm. I know that the difference between the peaks/protons is their vicinity to the OH group.

My questions is:
Is there any way to do the integral of the points lying between 1-2 ppm. This will be useful as I think that the peak at around 1.3 ppm represents more protons than the others. Also could the peaks be different due axial and equatorial protons resonating at different frequencies, or would the temperature

Or is there a better way to pair up the peaks between 1-2 ppm and the remaining protons in the cyclic.


texts:
When two liquids mix, and they are not hindered by a polarity mismatch (like oil and water), why don't they always form a homogenous mixture? Due to entropy, a liquid will disperse itself evenly. This even distribution will lead to homogeneity, no? According to an answer to this question (one given when this question looked different), said that they don't always distribute themselves evenly. So, let me lay done some ground rules:

Both the liquids are non-polar or polar
The liquids do not react in a way that creates products

Now, what hinders these liquids from dispersing evenly in each other?
Also, I'm going to clarify a certain conception I have, in case it is wrong:

A homogenous mixture is a mixture where the parts are evenly distributed. A solution is a homogenous mixture, where the solute has been deconstructed into its ionic components.


texts: Dissolving Metal Reduction of 4-Octyne to (E)-4-Octene and What Else?

texts:
I was reading Solomon's Organic Chemistry and came across the Dissolving Metal Reduction of 4-Octyne to (E)-4-Octene. (The same as can be found this question)

But the book states that the (E)-4-Octene is only produced in a 52% yield. This doesn't seem very impressive to me. What is the other 48%? If it's (Z)-4-Octene, can we really say that the reduction favors anti addition? If it's octane, I'd understand, but still would think you're losing a lot of product.

So does anyone know what the other products in the reaction are?


texts:
Why is the cone voltage on mass spectrometers positive for positive ions?
I would have thought that the positive ions would be attracted to the
cone by a negative potential. Is the voltage, perhaps, indicative of something else (and not of the degree of attraction between ions)?


texts: What is the naming convention for Sn and Pb in inter-metallic compounds?

texts:
How would one go about naming inter-metallic (specifically, transition post-transition) compounds containing tin and lead?

It is usually easy figuring out the naming of such compounds as they follow a simple naming convention, for example ruthenium germanide, niobium aluminiumide and so on.

But what about tin? Would you get ruthenium stannide? Stannumide? Or something completely different? Same goes for lead, but I feel like I've heard the name aurous plumbide referring to $\ce{AuPb2}$ before.


texts: Truly Understanding the Second Law of Thermodynamics and Entropy

texts:
There are some seemingly contradictory things I’d like cleared up:

Second Law states: $\mathrm dS_\text{univ} = \mathrm dS_\text{sys} + \mathrm dS_\text{surr}$, and $\mathrm dS_\text{univ}$ is always positive in a spontaneous process.

First off, what does “spontaneous” truly mean? “It means the reaction occurs without any external energy input” – I’ve heard this one before, but it doesn’t make sense. In an equilibrium there is a spontaneous direction (the side that is favored) but the reverse reaction also occurs, though at a slower rate, than the spontaneous reaction. What is the most fundamental definition, intuitive and universally applicable definition of spontaneous?

Moving on, according to ChemWiki the Second Law states that the entropy change of the universe can never be negative, even though my textbook says that this is only true for spontaneous processes. Who is right and why (explain in quantum terms, since I understand that in the long run of course the entropy of the universe increases by the laws of probability)?

An example to work through:

In a living cell, large molecules are assembled from simple ones. Is this process consistent with the second law of thermodynamics?

Book’s solution: To reconcile the operation of an order-producing cell with the second law of thermodynamics, we must remember that $\mathrm dS_\text{univ}$, not $\mathrm dS_\text{sys}$, must be positive for a process to be spontaneous. A process for which $\mathrm dS_\text{sys}$ is negative can be spontaneous if the associated $\mathrm dS_\text{surr}$ is both larger and positive. The operation of a cell is such a process.

First off, are we to consider the operation of a cell in this problem spontaneous? As I recall from biology, life processes require ATP, the carrier of energy, so these would technically “require external energy input,” would they not? However, the book treats it as a spontaneous process. Again, this confuses me because the definition of spontaneity is inadequate as I now semi-understand it.

Sorry for such a long post, but these are very important and fundamental ideas in spontaneity, entropy, and free energy, and I don’t want to read on until these ideas are well ingrained, and correctly so.


texts: Calculate concentrations of ions after acid-base reaction given volumes and concentrations

texts:
A $\pu{35.0 mL}$ of $\pu{4000 ppm}$ $\ce{HCl}$ solution is mixed with $\pu{45.0 mL}$ of $\pu{0.1025M}$ $\ce{NaOH}$ solution. Assume volumes are additive.
$$\ce{NaOH(aq) + HCl(aq) -> NaCl(aq) + H2O(l)}$$
Calculate the concentrations of the ions $([\ce{Na+}],$ $[\ce{H+}],$ $[\ce{OH-}],$ $[\ce{Cl-}])$ remaining in solution after the reaction is complete.

$[\ce{Na+}]$ and $[\ce{Cl-}]$ are the spectator ions:
$$[\ce{Na+}] = \pu{0.1025 M}$$
$$[\ce{Cl-}] = \frac{\pu{4000 ppm}}{1000\times\pu{36.456 g mol^-1}} = \pu{0.1097 M}$$
Limiting ion is $[\ce{H+}],$ there are no $[\ce{H+}]$ left in solution after reaction.
Am I correct? And I want to know how to calculate the concentration of  $[\ce{OH-}]?$


texts: I came across the compound dl-stilbene dibromide, and I am confused by exactly what this means. I thought it might have meant a racemic mixture but there is only one chemical structure given.


texts: How to tell between carbon powder or graphite powder?

texts:
I have a black powder that I cannot reliably tell just by looking or touching whether it is graphite powder or charcoal powder.

Are there any simple tests that I can perform to tell whether it is one or the other?

What I have tried:

Adding it to water, it sinks to the bottom and leaves a slight oily looking film on the top. Upon stirring, it darkens the water and then gradually sinks back to the bottom after some time.
I tried writing some thick lines on a piece of paper with a graphite pencil and testing for conductivity (high resistance).
Same high resistance with the powder (granted this is very unrepeatable)
Rubbing it into paper it has a much blacker colour than the graphite (which to me looks like a really dark gray). However, I don't know if that is a reliable indicator.

I've also added a picture, if it helps:

EDIT:

Ok, I've made a paste using isopropyl alcohol and the carbon powder and made a small "stick" or rod of the stuff. I have now been able to achieve solid continuity at around 2 centimeters in distance and the resistance dropped from the high 40 - 50 kOhms for the loose powder, to the low 10s (ie 40 Ohms). If this helps anyone.


texts: Are we capable of deliberatly creating DNA from inorganic compounds?

texts:
Good day
The  Miller–Urey experiment showed that organic compound can naturally form from inorganic substances. What i wish to know is this: Could we as humans deliberately create a DNA molecule starting with only inorganic substances?


texts: What is the correct net ionic equation for the neutralization of phosphoric acid?

texts:
What is the net ionic equation for the reaction between phosphoric acid and sodium hydroxide?

I came up with
\begin{align}
\tag1 \ce{H+ + H2PO4- + OH- &-> PO4^3- + H2O},\\
\tag2 \ce{H+ + OH- &-> H2O}.
\end{align}

Or is it, since phosphoric acid is a triprotic acid, whose ionization is
$$\ce{H3PO4 <=>3H+ + PO4^3-},$$
therefore the net ionic equation will be
$$\ce{3H+ + 3OH- -> 3H2O}?$$


texts: Will a container made of ice hold an alcoholic beverage that is below freezing in an environment that is also below freezing?

texts: This very specific question that came after saw I a travel episode where they served alcoholic beverages in ice glasses in an ice bar. I wondered if the drink contents would stay in the glass (of ice) without the glass (of ice) melting. I reason that the drink would be cold enough to not melt the ice thus allowing it to stay frozen.


texts: Frequency, the only real characteristics of electromagnetic radiation ??

texts: My book says: frequency is considered as the only REAL characteristics of electromagnetic radiation, because it is unchangeble if the radiation comes up with some other environment, while the wavelength and the wavelength number do change. How can wavelength change and the frequency not ? The formula tells us very clear that while frequency increases, wavelength decreases and vice versa ?!


texts: Visualizing the e_g and t_2g orbitals in case of tetrahedral crystal field splitting

texts:
I am reading about the crystal field theory (CFT) for the case of tetrahedral coordination entities. I understand that the $\mathrm{t_{2g}}$ orbital is nearer to the ligand than the $\mathrm{e_g}$ orbital, from the data of the angles between the respective orbitals, central metal atom and the ligands. But I do have the following questions:

Deriving the angle for the $\mathrm{t_{2g}}$ and $\mathrm{e_g}$ orbital mathematically.
The angle in case of $\mathrm{e_g}$ orbital is roughly $55^\circ,$ which seems to come from dividing the tetrahedral angle by $2.$ Also, the angle in case of $\mathrm{t_{2g}}$ orbital comes out as $35^{\circ}16',$ which I have no idea about.

Positional analysis.
Lee's Concise inorganic chemistry [1, p. 220] states that

Alternatively the $\mathrm{t_{2g}}$ orbitals are half the side of the cube away from the approach of the ligands, whilst the $\mathrm{e_g}$ orbitals are half of the diagonal of the cube away.

I believe the angles mentioned can be derived from the statement, but I'm not sure how the statement came about. It would be great if anyone could share some visual models of this part of CFT for tethrahedral coordination entities and suggest the right approach to understanding this.
Reference

Lee, J. D. Concise Inorganic Chemistry, 4th ed.; Chapman & Hall: London ; New York, 1991. ISBN 978-0-412-40290-6.


texts: Is there a better way balancing reaction equations than systematic trial and error?

texts:
I was introduced to the concept of balancing chemical equations in school and I did some practice examples, which were easy and took me about 2 minutes per question. I used the systematic trial and error method and I don't really like it.

I'm worried that my teacher will give us a more difficult question, so I'm looking for a method to solve chemical equations such as
$$\ce{C3H8 + O2 -> CO2 + H2O}.$$

I have tried matrices, but I don't really understand them, as I am not in grade 12 yet. If you know matrices, can you explain how I can balance the chemical equation with aforementioned method (thoroughly)? I would also be grateful if you have any other useful and quick methods which work for pretty much any high school chemical equation balancing problem.


texts: Why CO2 is not reducing the pH of NaOH as the way it is expected

texts:
I am using $\ce{CO2}$ for the reduction of pH of $\ce{NaOH}$ solution ($\pu{2.5g}\; \ce{NaOH} + \pu{250ml}\; \ce{H2O}$, with $\mathrm{pH}\; 13+$).
I am introducing $\ce{CO2}$ with different dosages ($\ce{50cc, 100cc, 150cc, 200cc, 250cc, 300cc, 600cc, 900cc, 1200cc}$, and $\pu{1500cc}$) using syringe into $\pu{35 ml}$ solution of $\ce{NaOH}$ prepared as mentioned above. The $\mathrm{pH}$ first increases and then starts decreasing but stop at the same level of initial $\mathrm{pH}$ value of the solution (The amount of $\ce{CO2}$: $\pu{50cc}=\pu{0.03g}$).
Trials run for $\pu{60 min}$ after that, the samples are preserved at $\pu{4 ^\circ C}$ and $\mathrm{pH}$ measured again after $\pu{24 h}$, but the value does not reduce.

Ideally, if everything works properly, the $\mathrm{pH}$ of the solution should decrease gradually. However, instead of $\mathrm{pH}$ reduction first it increases and then decrease at the same level, when we mix $\ce{CO2}$.

I will appreciate if someone share his or her experience or comments as to what is the possible cause of this unexpected trend and how to fix it.


texts: Could muscarine be an antidote to atropine poisoning?

texts:
According to Wikipedia,

  "Muscarine poisoning is characterized by miosis, blurred vision, increased salivation, excessive sweating, lacrimation, bronchial secretions, bronchoconstriction, bradycardia, abdominal cramping, increased gastric acid secretion, diarrhea, and polyuria. If muscarine reaches the brain it can cause tremor, convulsions, and hypothermia. Cardiac ventricles contain muscarinic receptors that mediate a decrease in the force of contractions leading to a lower blood pressure. If muscarine is administered intravenously, muscarine can trigger acute circulatory failure with cardiac arrest... The specific antidote is atropine."

However, the wikipedia article on atropine also states,

  "In overdoses, atropine is poisonous."

Could muscarine be used to treat atropine poisonings, just like atropine is used to treat muscarine poisonings?


texts:
I have book that contains the following paragraph:

  Due to high dielectric constant, it (water) has a very strong hydrating tendency. It dissolves many ionic compounds. However, certain covalent and some ionic compounds are hydrolysed in water.

Is this statement self-contradictory? Doesn't 'hydolysed in water' mean dissolved in water?


texts: Varying data about solubility of sodium acetate trihydrate

texts:
I recently looked up the solubility of sodium acetate trihydrate in water at 20°C and found surprisingly diverse values such as:
613g/l (GESTIS-Stoffdatenbank)
762g/l (TU Freiberg)
1250g/l (applichem, a vendor)
612g/l (German Wikipedia)
1233g/l (English Wikipedia)
I also found 408g/l somewhere but I can't find the source anymore.

As those values differ by a huge amount, I wanted to ask if someone knows how it comes to such a big difference.

Furthermore, I would be very grateful if someone could point out the correct value.


texts: Why do diamond and graphite have different structures, when they are both composed of carbon?

texts:
Both diamond and graphite are covalent networks and are both made entirely from carbon, but why does diamond have a three dimensional network of strong covalent bonds which makes it hard, whereas graphite has flat layers of carbon atoms which makes it a weak object and breakable.

This seems strange to me, because they both are made of the same atoms and both are covalent networks.


texts: What does this representation of organic aromatic compounds mean?

texts: I saw this structure in some problem. What does this mean? How to express this in form of a simple structure


texts: Why does pyridine make such a big change from SNi to SN2?

texts: When an alcohol is treated with SOCl2 alone, retention through SNi takes place, whereas adding pyridine makes the reaction follow SN2 mechanism and inversion takes place. What concept lies behind this occurrence?


texts: How do you calculate the total heat capacity of a reaction

texts:
I need help with this one homework question:

I am combining $100\,\text{mL}$ of $0.5~\text{M}~\ce{HCl}$ and $100~\text{mL}$ of $0.5~\text{M}~\ce{NaOH}$ to obtain $200~\text{mL}$ of $0.25~\text{M}~\ce{NaCl}$. The change in temperature of this reaction was $\Delta \vartheta  =3.38~\text{°C}$. I have to calculate the heat of reaction for 1 mole of the reactant. I also need to calculate the $c_\text{total}$ of this reaction. How do I go about doing this?

So the equation is $$\ce{HCl + NaOH -> H2O + NaCl}$$

Suppose the heats of formation of $\ce{HCl}$, $\ce{NaOH}$, $\ce{H2O}$, and $\ce{NaCl}$ are $-166.19$, $-469.07$, $-285.85$, and $-406.77$, respectively, all in $\text{kJ/mol}$.

I went about doing this calculating the heat $$q=\Delta H=[-(-166.19-469.07)+(-285.85-406.77)]~\text{kJ/mol} = -57.36~\text{kJ/mol}$$

I then found the mass of the liquids used for the reaction:

$$\begin{aligned}m &= 0.1~\text{L}\times 0.500 ~\text{M}\times 36.4611~\mathrm{g\,mol^{-1}} \\
&\;\;+0.1~\text{L} \times 0.500~\text{M} \times 39.99715 ~\mathrm{g\,mol^{-1}}\\
&=3.822~ \mathrm{g} \end{aligned}$$

I then solved for $c$ using $q=mc\Delta T$.

$0.05\times 57360~\mathrm{J} = 3.822\ \mathrm{g}\times c_\text{total}\times 3.38~\mathrm{K} \Rightarrow c_\text{total}=222.01 ~\mathrm{J \, g^{-1}\, K^{-1}}$

By the way, I multiplied the $q$ by $.05$ because that's how many moles of reactant I have (since we have the molarity and volume of the reactant).

I am pretty sure I am doing something wrong, but I am not sure what.


texts: Why lactols being tetrahedral complexes do not break?

texts:
The answer given is (D) but I think (B) should be the answer as the concerned benzylic carbon in option (D) is an unstable tetrahedral complex and it should break. Besides, the medium is acidic so it should catalyse this process.
In generalising, my question is: are lactols stable?
Edit:
I found online that there is an equilibrium between lactols and corresponding hydroxyaldehyde. So, why lactol is favoured more in this case?


texts: I would like to find out how long it would take to completely turn 50 litres of water to steam. Let's assume power of 2500 W and the water is already at boil. I am not very scientific so please forgive any omissions. Thanks


texts: Effects of atmospheric gases on colour of aurora

texts:
Recently I moved to the north of Norway, so I've seen quite a few auroras. Because the colour is mainly green, I was sure this must be due to electron transitions in $\ce{N2}$ (because the atmosphere is like $75\%$ $\ce{N2}$)
Looking into this, however, I found out that the colours of the aurora are mainly due to electron transitions in oxygen gas. Why is it that the electron transitions of oxygen are most prevalent in the colours of the aurora, even though it is far less abundant than nitrogen?

I also read that oxygen gas gives one colour up to $150$ miles altitude(green), and another above $150$ miles (red). Can someone explain the reason for the difference in colour? Does oxygen exist in different oxidation states at different altitudes, leading to different electron configurations => different available electron transitions?


texts: Why is the volume in this compress gas cylinder constant throughout?

texts:
I am stuck on this gas question and its really stressing me out.

  A compressed cylinder of gas contains $2.25 \cdot 10^3~\mathrm{g}$
  of $\ce{N2}$ gas at a pressure of $4.25 \cdot 10^7~\mathrm{Pa}$ and a temperature of
  $19.4~^\circ\mathrm{C}$. What volume of gas has been released into the atmosphere
  if the final pressure in the cylinder is $1.80 \cdot 10^5~\mathrm{Pa}$?
  Assume ideal behaviour and that the gas temperature remains unchanged.

I know I have to use the ideal gas law for this.
I've seen the solution for this problem, but something still doesn't make sense to me.
In the solution they used $$\frac{nRT}{p} = \frac{n_\mathrm{f}RT}{p_\mathrm{f}},$$ to find the final amount of nitrogen gas in moles, $n_\mathrm{f}$, remaining in the gas cylinder. But why is the initial volume and final volume the same? Since gas is being released into the atmosphere, shouldn't the final volume change?


texts: White creamy substance (not calcium) observed when boiling water is filtered through coffee paper filter

texts: We have hard water from our well. It is filtered twice before boiling it: by the water filter and with a manual on-the-counter filter. When boiled in a clean kettle a white substance floats in the water, and it isn't calcium which is hard and sinks at the bottom. Then we filter that hot water through a coffee paper filter and a white creamy substance remains. I called water related companies but no one knows. Anyone have a answer to this one?


texts: What is the function of PhLi in this reaction?

texts:
Can someone please explain the mechanism of the reaction when we add 2 moles of $  \ce{Ph3P}$ and $\ce{PhLi}$ to 1,2-dichloroethane.

I know this is a type of Wittig reaction but I am not able to figure out how the reaction will work out.


texts: What is the Lewis dot diagram for molybdenum and cerium?

texts:
How do I draw a Lewis diagram for $\ce{Mo}$ and $\ce{Ce}$?
 I am a bit confused since they are transition metals.
Attempt
The outer electron configuration for $\ce{Mo}$ is $\ce{5s^1 4d^5}$. The number of valence electrons would be 6 if I am correct. Wouldn't the Lewis dot structure look like the one for group 6A elements with six dots?

EDIT: I spoke to my lecturer, he said I have to do research and draw the Lewis dot diagram of Mo and Ce. My textbook says that transition metals have incompletely filled inner shells, and that generally we cannot write simple Lewis dot symbols for them. Yet, my lecturer said it would be similar to other elements. I am very confused!


texts: I see many sites that claim to sell working gold detectors but I am not convinced that they work. Also, does a metal detector detect gold?


texts: Sodium peroxide is a strong oxidizing, but when it is added to an acidified dichromate solution then already chromium is present in its highest oxidation state so the color of the solution shouldn't change, still, it is given in my textbook that color of the solution changes to blue. How does that happens?


texts: What does it mean for meth or any other compound to be 'pure'?

texts:
In Breaking Bad, Walter White can cook $99.1\%$ pure meth. In general what does it mean for a substance to be pure? In this case, what exactly does it mean for meth to be pure? Does higher purity mean less unhealthy? More addictive? Giving more euphoria for the user?

For comparison, is the purity of prescribed methamphetamine or methylphenidate to people with ADHD or narcolepsy close to $100\%$? My guess is that purity is how close Walt's product is with legal meth.


texts: Why does copper(II) carbonate decompose into copper(II) oxide rather than copper(I) oxide when heated?

texts:
I recently did a lab at school surrounding the decomposition of copper(II) carbonate into copper(II) oxide, and subsequently into pure copper, when sufficient heat is added. What I don't understand is why the copper(II) carbonate can't decompose into copper(I) oxide, rather than copper(II) oxide.

For example, copper(II) carbonate decomposing into copper(II) oxide would be:

$$\ce{CuCO3 ->CuO + CO2}$$

While copper(II) carbonate decomposing into copper(I) oxide would be:

$$\ce{4CuCO3 -> 2Cu2O + 4CO2 + O2}$$

If anyone could help me understand why copper(II) carbonate decomposes into copper(II) oxide rather than copper(I) oxide, I would greatly appreciate it.

Edit: I've been nosing around Wikipedia a bit and discovered that copper(I) oxide reacts with atmospheric moisture to become copper(II) oxide. This would explain why copper (I) oxide is not present; it has degraded into copper(II) oxide. I'm still interested in how copper(I) oxide and water react with respect to reactants and products, so if anyone knows what the equation between the products and reactants is, I would like to know.


texts: Z-matrix of a series of 5 colinear atoms

texts:
How can I write a Z-matrix for the following complex?

  O==C==O  H--O
               \
                H

I have managed to write:

O
C   1  a
O   2  a     1  180
H   3  d     2  180    1  ?
O   4  b     3  180    2  ?
H   5  b     4    t    3  ?

but I don't know how to specify the dihedral angles indicated with ?. Are they all zero? Or completely unspecified? If so, will I be able to do a coordinate optimization with these variables or will it be a problem?


texts: How does liquid mercury conduct electricity?

texts: It is stated that mercury is a liquid at STP because the high relativistic mass of its valence electrons stabilizes their orbits and thus prevents the electrons from being shared. If so, liquid mercury would seem to have no "free" electrons; how, then, does it conduct electricity?


texts: what does the mixture between urine and dishwater cause?

texts: I have built an rv from a short school bus.  I ran a hose from the "toilet" to a tank in the back to drain the toilet. We wash our dishes in a basin on the counter and dump the dishwater into the toilet to also drain into the tank. I am getting a tannish/white build up in the hose that is plugging the line and not letting it run into the tank. It is the consistency of toothpaste when its wet and when it dries, it is like chalk. Any ideas on what the mixture of urine and dishwater is making? Also, we use vinegar to rinse dishes, so there is a small amount of vinegar going into that hose also.


texts: How could household vinegar create a salt on car carpet?

texts:
I am not a chemist! My chemistry classes from my molecular biology undergrad are far behind me. But I think I created a salt, and I don't know how. Here is my mystery:

I recently got some water in my car, and wanted to prevent mold growth in my carpet mats. I brought the mats inside, vacuumed off, and completely soaked them in household vinegar. Then I placed the mats near a running dehumidifier (where the warm air comes out in the back).

White crust appeared on the carpet. At first I thought my dehumidifier was spitting something out, but the white substance was not on any other nearby surface--only on the car carpet. Eventually as the further parts of the carpet dried, they also showed the white crust. It covers pretty much all of the carpet.

Is this, in fact, a salt? If so, what basic substance could have been in my car carpet mat that would cause this reaction? Thanks everyone!


texts: How is NaOH able to clear a solution of Paraformaldehyde?

texts:
While making a solution of $4~\%$ para-formaldehyde for immunohistochemistry (to fix the tissue), we add para-formaldehyde into water and stir. It looks like a chalky supersaturated solution even after stirring with a magnetic stirrer. And as per protocol, you are supposed to add 2 drops of $2~\mathrm{N}\ \ce{NaOH}$ to clear the solution. It surprisingly turned crystal clear!

I was amazed at how just 2 drops could make such a huge difference. Does it react with para-formaldehyde? Does changing pH change solubility? But para-formaldehyde is a polymer, how could it suddenly become soluble? Does adding $\ce{NaOH}$ make it a monomer?


texts: The ionic radius of aluminium(III) vs. the covalent radius of neon?

texts:
I was wondering if it is a valid comparison to look at the ionic radius (noble-gas-like configuration) of a metal and the covalent radius of a noble gas. Specifically, $\ce{Al^{3+}}$ and $\ce{Ne}$.

This website gives me the impression that for comparable radii definitions, neon is slightly smaller than $\ce{Mg^{2+}}$ but larger than $\ce{Al^{3+}}$.

Someone I know is wondering why we should/shouldn't just use the atomic radius of neon, rather than the covalent radius, to compare to the ionic radius of metals like aluminum and magnesium (yes, even though they are on the next period).


texts:
If two similar sized atoms have different electronegativity values, the atom with higher electronegativity holds the electrons more tightly, and thus is more stable. Example: hydroxide vs azanide (NH2-).

If two atoms have different sizes (down the periodic table), the larger atom has electrons more spread out and thus is more stable.
Example: fluoride vs iodide anion

To me, these two statements are contradictory. One says tight electron cloud means not reacting while the other says spread electron cloud means stability (less repulsion). Is one of the statements wrong? I'm sure I am missing something here. Thank you in advance for your help.


texts: How to calculate a molecule's oscillator strength?

texts:
I was wondering how to calculate a molecule's (e.g. biphenyl) oscillator strength using a very simplified model.

If I want to calculate a molecule's excited states a good start is something like a particle in a box model, which won't come up with even nearly exact energies but with an idea of energy values. Is there anything similiar for the oscillator strength which would deliver simplified solutions?


texts: Melting temperature vs Isotropisation temperature in liquid crystals

texts: What is exactly the difference between these two? I think melting point is when the compound melts down to visually liquid state but actually LC state and latter is when polymer becomes completely isotropic liquid.


texts:
The glass sensor has became red inside like something melted. I stored it in a liquid with pH that mentioned in the manual. What is that and why could that happen, how often that happens with pH-meters?
(10 bucks pH-meter from China)


texts: Can rearrangement in carbocations cause inversion?

texts:
Can rearrangement reactions in carbocations cause inversion?

If you have a carbocation rearrangement (i.e. a methyl shift or a hydride shift), is it possible for inversion of stereo chemistry to take place?

The carbocation has the free p-lobe, so is it possible for the hydride/methyl group to bond to either lobe, such that one can cause retention of stereochemistry while the other can cause inversion of stereochemistry? Does this logic even make sense?


texts:
My attempt:- 1)At 0.68e15 Hz frequency of light,Metal A gives 7.2eV Kinetic Energy(KE).

2)At 1e15 Hz frequency of light, Metal B, gives 6eV Kinetic Energy.

3) At 1.1e15 Hz frequency of light, Metal C gives 5.5eV Kinetic Energy.

4)At1.2e15 Hz frequency of light, Metal D gives 5eV Kinetic energy.

Now $KE_{max}=(\frac{hc}{\lambda}-\phi)$ where c= speed of light, $\lambda$=wavelength of light and $\phi$= work function of metal.

Now $7.2eV=(4.14e-15eVs \times 0.68e15 Hz- \phi)$ for metal A.The wavelength of light is 441 nm. Likewise we can compute wavelength of light incident on Metal B, C and D.

But we don't know the work functions of Metal A,B, C and D.

So, how to answer this question?


texts:
PROBLEM: A solution was prepared by mixing $\pu{25.00 mL}$ of $\ce{NaOH}$ $\pu{(c = 1mol/L)}$ and $\pu{10.00 mL}$ of acetic acid $\pu{(c = 2.5 mol/L)}$ in water to give $\pu{250 mL}$ of solution.

What is the $\mathrm{pH}$?

$K_\mathrm{a}=\pu{1.76\times 10^{-5} mol/L}$

Ok, so I know acetic acid will react with sodium hydroxide do form sodium acetate:

$$\ce{CH3COOH + NaOH -> CH3COONa + H2O}$$

initial quantities of $\ce{CH3COOH}$ and sodium hydroxide are $\pu{ 0.025 mol}$  (c*V)each

after the equilibrium is reached all base and acid have reacted, so we have $\pu{0.025 mol }$ of $\ce{CH3COONa}$

I can't calculate the $\mathrm{pH}$ using Henderson-Hasselbalch approximation, because concentration of acid is 0.

I got a response that I should solve it like this (after I do ICE table like I did above):

$$\ce{CH3COO- + H2O <=> CH3COOH + OH-}$$

$[\ce{OH-}]=\sqrt{  K_\mathrm{b}\cdot c_\mathrm{salt}}$
and after I calculate $\mathrm{pOH}=5.12$ I can calculate the $\mathrm{pH}=8.88$

I dont understand the last part, why is this so? what is

$$\ce{CH3COO- + H2O <=> CH3COOH + OH- }$$

representing?

Thanks for answering! :)


texts: Is it possible to solve the equation for the diffusion of gas through a sphere analytically by applying e.g. "combination of variables"?

texts:
In the case of diffusion through a thin film it is possible to combine the variables in the following way:
$\sigma = \frac{x}{\sqrt{4Dt}}$

where

$x$=length
$D$=diffusion coefficient
$t$=time
$\sigma$=a function of x and t

Thereby, x and t is substituted by the single variable sigma

Is there a similar expression for a sphere?

E. L. Cussler discribes in detail how to solve the equation for a thin film by applying "combination of variables".


texts: Which etching process is better, photochemical or electrochemical?

texts:
My boss and I are experimenting with several different ways to micro machine .01" and .005" stainless steel. When I look up how it's done professionally, I see an overwhelming majority of companies use photochemical etching (acid etching). I have also seen electrochemical etching as an option, but not as a "precision" method. So far, both methods have achieved sub-millimeter precision and electroetching currently takes a slight lead over photochem, but neither have achieved the incredible accuracy that I've seen online that appears to have resolution finer than the human eye can distinguish.

Electrochem etching has also proven to be much simpler and safer since we don't have to be involved with potentially dangerous chemicals. My suspicion was that acid etching would be more precise since it is so widely used, but our results are not supporting that hypothesis. I am wondering what advantages does acid etching have over electroetching that makes it so much more popular? I'm curious to know more so we can further refine our etching process.


texts: Coordination compounds with alkene ligands

texts:
I came across this compound: $\ce{[Pd(η^2-C2H4)Cl2(H2O)]}$

What does that '$\eta^2$' sign mean? I am guessing that it means that the ligand is bidentate because if it wasn't, I don't think it is possible (well it would be rare) for a metal to be only co-ordinates by 3 ligands.

If this is the case, how can the carbon atom in ethene bond to Pd as it doesn't have a lone pair? Does the double break and hence the 2 carbons bond to the metal?


texts: Lithium is known to have the highest ionization energy among Group 1 elements. Also, characteristic colours in the flame test arise due to the excitation and de-excitation of electrons. Then why Lithium gives Crimson Red colour in the Flame test, why not a colour corresponding to a higher frequency like Purple or Blue colour even though the highest amount of energy is involved in the excitation and de-excitation of electrons of lithium when compared to the energy involved in the same process for other Alkali metals?


texts: Which quantum chemistry approximation to use?

texts:
I'm just getting started with quantum chemistry using some simple test problems.  I have a few of the software packages installed (ASE, Psi4, GPAW etc) and everything is working - no issues with the software itself - but there is a bewildering variety of methods, from semi-empirical (PM7) to DFT (B3LYP) to coupled cluster (CCSD(T)); plus options for each such as basis functions, and nothing in the documentation gives any specific advice on what to use when.
Is there concrete guidance on which method is appropriate for which type of problems?
What I'm mostly interested is biological systems: molecules in water at room temperature, and both covalent and non-covalent interactions; most of the atoms are CHNOSP.  An example would be taking a system of a few hundred atoms and optimizing the coordinates (either locally or trying to find the global minimum).  A slightly more ambitious project would be to optimize the coordinates a few hundred atoms within a much larger system of thousands of atoms (where the other atoms have partial charges and produce electrostatic forces, but are otherwise fixed).


texts:
My textbook mentions that chlorination of alkanes by $\ce{SO2Cl2}$ is preferred over $\ce{SOCl2}$, but I didn't understand why.

Could someone explain which of the two reagents I should use in what situations, and briefly tell me why?

There is a similar question here:
How does SO2Cl2 react with alcohols?

However the answers there did not completely clarify my doubts.


texts: Finding chiral carbons in aromatic or cyclic compounds

texts: I know that for a carbon to be chiral four different groups should be attached to that particular carbon. But, what about in the case of cyclic compounds? What's the method to check chirality if the carbon is not $\mathrm{sp}^3$ hybridized and only three, or two groups are attached to it (through double or triple bonds)?


texts: Request for a graph of the combined probability density of the three p-orbitals

texts:
This started when i was wondering why p-orbitals have an unsymmetrical shape (which isn't clear to me yet). But then i came across Halliday/Resnick/Walker's Fundamentals of Physics. In it, they have said that the three p-orbitals show their individual shapes in presence of a magnetic field. But normally, in an isolated atom, the three p-orbitals have the same energy and are indistinguishable, and that their combined probability density is spherically symmetrical.

I am having trouble in visualizing this. The three dumbells do not look like they could complete a sphere! For example, what about the region in the direction of $\hat i + \hat j + \hat k$? Wouldn't gaps be left behind? Wouldn't this destroy the symmetry of the distribution?

A visual graph of the three separately and then the three together (like different coloured dots for different p-orbitals) would help. I have no resources or skills (not even remotely close!) to do it myself, so i am requesting this to the skilled people out here. Thank you very much!


texts: Is there any substance that's a 0-0-0 on the NFPA diamond? Basically a perfectly safe chemical.


texts: How to use dispersion correction with TPSSh in Gaussian 16?

texts:
A colleague of mine suggested to use TPSSh as a functional. Since I am applying Grimme's D3 dispersion correction by default, I was surprised that it wasn't implemented in the standard density functionals, cf. Gaussian Manual (Copy @ The Internet Archive).

Since I might not be the only one to come across that: How can I use dispersion correction with TPSSh (or other non-implemented functionals) in Gaussian 16?

In principle the following route section is in use:

#P TPSSh/def2TZVP           ! verbose, method/ basis set
EmpiricalDispersion(GD3BJ)  ! Switch on D3 with Becke-Johnson damping
opt(MaxCycle=100,VeryTight) ! Run optimisation
int(ultrafinegrid)          ! use finer grid for dfa

Related Error is if attempted:

 R6DS8: Unable to choose the S8 parameter, IExCor= 2523 IXCFnc= 35 ScaHFX=  0.100000 IDFTD=4
 Error termination via Lnk1e in [...] g16.b01_bin/l301.exe at Thu Oct  4 18:59:24 2018.

But it could also be the S6, a1, or a2 parameter. If zero-damping is used, then it could also be S6R.


texts: Copper plating with switched anode and cathode

texts:
Please help!
I was working on a mock research project/lab for my chemistry class testing the rate of electroplating of copper vs. voltage. I had copper and nickel electrodes and .1M copper sulfate solution. I made a huge mistake, however, and plugged the positive end into my nickel electrode and the negative end into the copper. This meant that the copper in solution was attracted to the copper electrode, not the nickel. I however, didn't notice because as I ran more and more trials, an orange buildup was in fact showing up on my nickel electrode that looked just like copper plating. When I measured the mass, however, of the nickel electrodes, they consistently went down (the higher the voltage, the bigger the difference). What happened? Why did the mass of the nickel electrode go down (shouldn't it have stayed the same)? What was being plated onto the nickel?

Thank you!


texts: Which is the suitable process for ball milling?

texts: Why do we mainly choose the wet ball milling process in spite of dry ball milling process? Both processes are used to make a homogeneous mixture of different compounds.


texts: Relation between equilibrium constant and entropy change

texts:
Like the Van't Hoff equation, which relates change in enthalpy to equilibrium constant, is there a similar equation for the relation between change in entropy and equilibrium constant?

Consider the following specific case,

  For a reaction taking place in a container in equilibrium with its surroundings, the effect of
  temperature on its equilibrium constant K in terms of change in entropy is described by

  [A] With increase in temperature, the value of K for exothermic reaction decreases
  because the entropy change of the system is positive

  [B] With increase in temperature, the value of K for endothermic reaction increases
  because unfavourable change in entropy of the surroundings decreases

  [C] With increase in temperature, the value of K for endothermic reaction increases
  because the entropy change of the system is negative

  [D] With increase in temperature, the value of K for exothermic reaction decreases
  because favourable change in entropy of the surroundings decreases

  Answer: (B) and (D)

My attempt:

Since equilibrium with surrounding is given, the reaction must be reversible.

This implies, $∆S=0, ∆S_s=∆S_{surr}$.

Also, at equilibrium $∆G=0$.

This implies, ∆$H=T∆S_s=-T∆S_{surr}$

(where the s subscript denotes system, and surr denotes surrounding)

Writing the van't Hoff equation in differential form, I got

$= d(lnK)=∆H(dT/RT^2)$

$=d(lnK)=-∆S_{surr}(dT/RT)$

Now, aren't options A and C true too?

As on integrating, we can see directly the variation of $K$ with $∆S$.

What is the correct way to solve this?

Edit: Where ever there is a big space, it implies ∆.
Example,     '       ' H=T '       '  ,

Means, ∆H=T∆S


texts: m-CPBA Selectivity between Baeyer Villiger Oxidation and Epoxidation?

texts:
If both a ketone and an alkene are present in a molecule and you add one equivalent of m-CPBA, what are the factors that determine which group will be oxidized, the ketone through Baeyer-Villiger oxidation or the alkene through concerted epoxidation? Is one of the reactions particularly faster and better than the other?

EDIT: Since the literature seems to be conflicted and there is not a clear general answer, let us take the below as an example because I am interested in the competing factors here. For this example, I am leaning towards epoxidation just due to electron-rich alkene, and there is no base to make m-CPBA a better nucleophile for BV.


texts: Methods to increase the speed of dissolving potassium sulfate in water apart from heating, grinding or shaking

texts:
I bought potassium sulfate to be used as a fertilizer. The fertilizer comes in the form of small pebbles 1-2mm in diameter. Wikipedia states that the solubility is around 111g/liter at 20°C.

I tested several concentrations

100g / liter

50g  / liter

25g  / liter

at room temperature (22° C). After 2 hours there are still solids remaining in the solution. The water here is hard (EC= 0.6ms / cm) which hinders the dissolution. What can I do to improve the solubility of this fertilizer in water apart from heating, using reverse osmosis, grinding the pebbles or vigorous shaking of the solution (which worked) but is very tedious.


texts: My mom gave puffed rice to eat, I had quite wet hands. I saw that, each puffed rice pieces started hanging to the hand, when I brought my hand in contact with them. I thought about electrostatics initially to be the cause. Actually, the electrostatics usually deals with rough surfaces. Here due to hand being wet, it has got smooth surface. Then, what might be reason? I started thinking, suddenly I thought it to be because of hydrophillic nature of kadale puri (puffed rice). Is it really because of hydrophillic nature of puffed rice?


texts:
Fluorine has an electron affinity of about -300 kJ/mol. Lithium has an electron affinity of about 60 kJ/mol.

As I understand it when $\ce{Li^-}$ loses an electron about 60 kJ/mol is released but when $\ce{F}$ gains an electron about 300 kJ/mol is released.

Furthermore, when $\ce{Li^+}$ gains an electron about 520 kJ/mol is released because that is the first ionization energy of lithium and when $\ce{F^+}$ gains an electron about 1700 kJ/mol of energy is released because that is the first ionization energy of fluorine.

Shouldn't the cases that release the most energy be $\ce{Li}$ and $\ce{F^-}$ and so shouldn't those be the states that gases of those elements occupy?

Is it the case that $\ce{2F^-}$ is less stable than $\ce{F2}$ or something? Or is it the case that $\ce{F^-}$ could only exist in a highly artificial situation such as a magnetic contraption that trapped ions?

Why don't gases of elements with negative electron affinities exist as ions in nature?


texts: Why Do Electrodes Develop Equilibrium Potential?

texts: When we place metal electrode in solution of its ions, metal ions from metal have tendency to go into solution and ions from solution tend to enter the metal lattice. My question is what is a cause of this tendency for ions in metal lattice? Is it the same tendency which creates vapor pressure of liquids a.k.a Boltzmann distribution which allows some of metal ions (liquid molecules) that have enough energy to break metallic bonds and go into solution. If interactions with solvent or any other phase for that matter are favourable equilibrium position is more shifted towards solvation of ions (more negative electric potential of metal). Basically is Boltzmann distribution cause of tendency of ions in metal to move into solution and vice versa?


texts: Behaviour of oleophobic and hydrophobic object in an oil and water solution

texts: I am wondering what would happen if I put a small (between $\mathrm{5mm}$ and $\mathrm{1\mu}$, density between $\mathrm{1}$ and $\mathrm{2\: g/mL}$) item with both oleophobic and hydrophobic properties into an oil and water solution. Does anybody know? Would the item become suspended between the oil and water layers? I have not been able to find the answer anywhere!


texts: What fluid can I store metal filings in so they do not oxidize?

texts: I am working on an art project that will involve storing filings of various metals (e.g., iron, copper, zinc) in a colorless fluid. I want to prevent the metals from oxidizing for several years, so water is out. I already have 70% isopropyl alcohol. Will this work, or will the remaining 30% water be a problem? If not, what fluid would you suggest?


texts: If copper has 2 valance electrons and sulfur 6, why don't they bind in pairs?

texts:
Simple question, the average neutral copper atom has 2 valance electrons, and sulfur 6. Wouldn't the two electrons jump from copper and bind to sulfide?

The empirical formula is: $\ce{Cu + S -> Cu2S}$.

So apparently two copper atoms bind with every one sulfur atom. Does that mean that the copper atoms each gives one electron away and leaves them with 1 valance electron each?


texts: is there a reliable database with the pKa of halogenated carboxylic acids? I am also looking for the pKa of ethanoic acid substituted with other electronegative elements (like sulfur and oxygen).


texts: How does charge come on dispersion medium in colloidal sols ? (It is said that in electro-osmosis flow of dispersion medium takes because it is also electrically charged, but why ? )


texts: Why are absolute enthalpies of reactants not available?

texts:
The standard enthalpy of reaction is given as $$\Delta_r H = \sum\nu\;  H_m(\text{products})- \sum\nu\;H_m(\text{reactants}).$$
Peter Atkins in his book Elements of Physical Chemistry then writes regarding this equation:

The problem with this eqn, is that we have no way of knowing the absolute enthalpies of the substances . To avoid this problem, we can imagine the reaction as taking place by an indirect route, in which the reactants are first broken down into the elements. [...]
With the introduction of standard enthalpies of formation, we can write $$\Delta_r H = \sum\nu\;  \Delta_f H(\text{products})- \sum\nu\;\Delta_f H(\text{reactants}).$$  The first term on the right is the enthalpy of formation of all the products from their elements; the second term on the right is the enthalpy of formation of all the reactants from their elements..the fact that the enthalpy is a state function means that a reaction enthalpy calculated this way is identical to the value that would be calculated from the former eqn, if absolute enthalpies were available.

I'm not understanding why we can't calculate the absolute enthalpies. After all, enthalpy of a substance at a certain pressure (which is constant as we are talking about standard state & that is 1 bar) is given by the defining equation:
$$H= U +pV$$.
Yes, can't we calculate the internal energy taking a certain state as the zero of the energy? Why isn't it possible to calculate the absolute enthalpy?


texts: A simple question about the direction of a chemical reaction

texts:
I do not know much about Chemistry and whatever I knew has become rusty. I have a very simple query. I take a beaker containing pure $\ce{H2SO4}$ solution and immerse a rod of pure $\rm Zn$ into it. Now, the $\rm Zn$ will react with $\ce{H2SO4}$ to form $\rm ZnSO_4$ and hydrogen gas.
$$\ce{H2SO4(aq) + Zn(s) -> ZnSO4(aq) + H2(g)}$$
Why does not the reaction spontaneously reverse once again forming pure $\rm Zn$ and $\ce{H2SO4}$ molecules?

$$\ce{H2SO4(aq) + Zn(s) <- ZnSO4(aq) + H2(g) ?}$$

If your answer contains any technical jargon of Chemistry, please explain that in simple terms.


texts: Which of the given compound has the highest rate of dehydration?

texts:
I came across this question recently:

For which compound acid catalyzed dehydration rate is highest?

Now, they all are secondary alcohols so their dehydration should follow E1 mechanism and the stability of the carbocation formed in the RDS should be considered while comparing their rates.
Following this rule, I think, the answer should be (B) as ketone group shows (-)R effect in (C) and (-)I effect in (A) and (B), all which destabilize the carbocation formed.
But the actual answer is (A). How can that be? Is there some other mechanism to follow? I can’t understand what am I doing wrong.


texts: Reagent for identification of Water Hemlock (Cicuta) or Cicutoxin?

texts: Chemical reagents are used for macroscopic identification of some wild mushrooms. Are there similar reagents used to identify Water Hemlock (or potentially cicutoxin) as a supplement to visual identification of this incredibly poisonous plant?


texts: Quantitative MO theory- how is the overlap integral and the weighting coefficients of the molecular orbital actually evaluated?

texts:
Title. In my inorganic chemistry course, we learn about SALCs and qualitative MO treatment, with only a fleeting reference to the S integral and actual molecular wave functions (only hydrogen, $\ce{H2}$, was discussed).

I'm curious about how the S integral is evaluated for MOs in slightly more complex molecules i.e. $\ce{BF3}$, $\ce{CO}$, $\ce{H2O}$, and how the weighting coefficients are found, as they aren't discussed at all at my level.

Can someone explain this? Thanks!


texts: Isopropyl Alcohol leaves a white haze on plastic, is there anything I can use to clean it off?

texts:
Recently I wanted to clean up some lubricant on some keyboard switches. On some forums, an Isopropyl alcohol bath was recommended so I decided to give that a try and went to purchase some 91% Isopropyl from Target(purest I could find near me and I admit, I am a little impatient).

Good news - it worked in getting the lubricant off the switch! Bad news, on some of the switches, it left this white haze.

I'm not sure what it is, though from what I've been reading, it sounds like this is a common issue when using Isopropyl, my best guess is that it's some mix of the lubricant mixing with the alcohol and reacting poorly with the switch housing plastic given that I'm only seeing this haze on the bottom half of the switches which were the only parts of the housing that were lubed, the other parts are clean. Another reason for my guess is that this haze isn't appearing in the same amounts on all the switches if at all, some switch bottoms are basically clear.

It does appear to scrape off but looks like it will require a fairly strong brush which I don't have at the moment and I'm not sure if there's one available for purchase that could be used in this situation.

Is there any plastic-friendly household cleaner available that might be able to help speed up the process?


texts: Measuring distance in a conductive liquid

texts:
What is needed to  measure distance between two electrodes imersed in seawater ?
I have  tried measuring the voltage across the path (a suposed resistance) with a constant current source (about 10uA) passing the water to GND of circuit. (the resistance is suposed proportional to distance of electrodes) The probes are 100Hz reversing switched to avoid polarization. And I am using AG/ AGCl pellets as electrodoes. But until now I could not have stable results.
What may be wrong ?  Could someone help ?
Thanks

The AgAgCl sinterized disks was choose because it is very used as reference electrode for seawater potential measurements (cathodic protection) with very good results and low maintenance, but I really dont know if it is the the best for my application. The suface area is about 1 cm2 then we are expecting about 20 Ohms per cm of distance in seawater. With a 10uA as (AC square wave) current source  between electrodes voltage will range from about few milivolts up to 1 volt at 50m.  As you see the potential is bellow of water electrolisys. What you mean "with a lot of corrosion protection" for Stainless Steel plates ?
I understand that salinity, temperature etc could vary in the media but these factors are not expected  to change so quickly and I also intend to use a known distance sensors for reference as well averaging the measures.
I intend use this sistem in a dynamic environment where the reletive speed between sensors or the flow may be about 10 cm / sec.
What you think about the method ? There are a better one ?


texts: determine density of oxygen gas using modified ideal gas equation

texts:
I am trying to determine the density of a gas (oxygen). As the gas is a compressible fluid a modified version of the ideal gas equation is required. I have been given the following equation and I am struggling to interpret it. I would like advice on the unit conversions and whether this is the correct equation at all.

$$\rho=\frac{(P+1.01325).10^5.MW}{z.8314.(T+273)}$$

where:

$\rho$ = density (Kg/m3)

P = pressure (bar(g))

MW = molecular weight (in kg/kmol)

z = compressibility factor (dimensionless)

T = temperature  (deg. C)

I think that the 1.01325 converts the bar.g. to bar.a. then to pascals using the 100,000 multiplier?

Has the universal gas constant $8.314 J/(k.mol)$ been converted to $J/(K.kmol)$ ?


texts:
Just had a lecture there where the lecturer was doing revision on electronic configuration.

He stated that the electronic configuration of $$\ce{In^3+=[Kr] 5s^2 3p^1}$$

He didn't include the $\ce{4d^10}$ orbital. He said it doesn't matter and if we write the full E.C out it's incorrect. It basically goes against everything we studied in 1st year general chemistry. Also I believe he didn't take into account the fact that $\ce{In^3+}$ has $46 \, e^-$ not $49 \, e^-$.

Should the electronic configuration not be $$\ce{[Kr] 5s^0 4d^10 3p^0}= \ce{[Kr] 4d^10}$$

Can someone shed some light on whether he is right.


texts: Use of aqueous KOH and alcoholic KOH in dehydrohalogenation reactions

texts: What is the difference between aqueous KOH and alcoholic KOH? How do they react differently in dehydrohalogenation?


texts: Production of hydrogen through the reaction of aluminium metal and sodium hydroxide

texts:
If I have a solution of 25% $\ce{NaOH}$, and I simply add a cut-up aluminium can or some aluminium foil, will it react into hydrogen and sodium aluminate?

In principle this reaction should happen, but it didn't work when I attempted it. Perhaps an oxide layer prevented it, or a protective layer of sodium aluminate was formed. (Perhaps my experiment was faulty.) Should this happen, and what can I do to fix it? (My goal is to generate hydrogen gas.)


texts: I did an excited state calculation (TD-SCF)in Gaussian and wanted to see the MOs of the first excited state. But when I opened the checkpoint file in GaussView5 and clicked edit -> MOs, I could only see the configuration and MOs of the ground state. How do I see the excited state MOs in GaussView or other visualisers that can be downloaded for free?


texts: Why is bleaching with chlorine permanent but with sulphur dioxide temporary?

texts:
I was reading the properties of chlorine when I came across this statement:

Chlorine is a powerful bleaching agent; bleaching action is due to oxidation. Chlorine bleaches vegetable or organic matter in the presence of moisture. Bleaching effect of chlorine is permanent. $$ \ce { Cl_2 +H_2O -> 2HCl + O} $$ $$ \ce { Colored Substance + O -> Colorless Substance } $$

I searched it up and found out that bleaching with $\ce{Cl2}$ is an oxidation and is made powerful with the help of the nascent oxygen, hence it is permanent, but bleaching with $\ce{SO2}$ is a reduction and hence it is temporary.
Could someone please help me understand why the oxidation is permanent and the reduction is not? Is it powerful to an extent of the reaction not being able to get reversed? If yes/no, is there any quantitative/qualitative measure for the same?


texts: Amount of substance of a molecule in a solute the same as amount of substance of constituent elements?

texts:
I’ve done absolutely no chemistry since high school.  Now, 16 years later, I’ve been asked to look at some chemical analyses and I’m having trouble!

Context: I’ve got a series of spectroscopy results giving the concentrations (in mg/l) of chlorine and $\ce{SO4}$ in a sample.  I want to find the molar and mass ratios of $\ce{S}/\ce{Cl}$.

What I’ve done: I convert the mg to g, then (mass) concentration into a molar concentration by dividing by the molar mass (35.5 g/mol for $\ce{Cl}$ and 96 g/mol for $\ce{SO4}$).

Question: am I right in thinking that the molar concentration of $\ce{S}$ will be the same as the molar concentration of $\ce{SO4}$?  My reasoning is that 1 mol $\ce{SO4}$ contains 1 mol $\ce{S}$ and 2 mol $\ce{O2}$.

Furthermore, to get the mass concentration of $\ce{S}$ alone, can I just multiply my concentration of $\ce{SO4}$ by the molar mass ratio, $\frac{M(\ce{S})}{M(\ce{SO4})}$?


texts: I need to reduce the Nitrile group without affecting the boronic acid. How to do that?

texts: I need to Reduce the Nitrile group (CN) in the (3-cyanophenyl)boronic acid in to a primary amine without disturbing the Boronic acid group.Using LAH can trigger reduction of Boronic group. what are my options?


texts:
I'm trying to work out which are the aromatic ring systems in the drug aklavinone:

I am trying to follow Hückel's rules that the compound must be cyclic, be planar, possess a p-orbital on every atom in the ring, and have a π-system with $4n+2$ electrons.

I see that the benzene rings are obviously aromatic. But does the quinone ring (in red) also count as part of the 'aromatic ring system'?


texts: Does cinnabar react with bromine and iodine to form elemental sulphur? This reaction was described in "Explorations in the history of science and technology in China" but I have doubts...


texts: Is it possible to construct a 3D molecular model using x-ray powder diffraction data?

texts: I've got x-ray powder diffraction (XRPD) data on bendamustine HCl from a patent and I want to know how to construct a 3D model using this data with software.


texts: Predict Entropy based on the Balanced Equation

texts:
You cannot use values but must determine from looking
The equation I have trouble with is as follows:

  $$\ce{2Na(s) + 2H2O(l) -> 2NaOH(aq) + H2}$$

According to my teacher the entropy is positive. I also got the entropy to be positive, but now that I think of it, the moles is decreasing and one is becoming aqueous. So does turning into a gas trump everything?

What if NaOH was solid? Would it mean still that the entropy would be positive?

Also finally according to the textbook the entropy values is as follows:

  $$\ce{s<l<<g}$$

But where would the (aq) be?


texts: Why is the pressure correction in the van der Waals equation proportional to (n/V)^2?

texts:
The van der Waals equation for real gases is stated as follows:

$$\left(P + \frac{an^2}{V^2}\right)(V - nb) = nRT$$

For the coefficient $b$, we can reason out that more the number of molecules, the more volume will be occupied by the molecules (in turn reducing the free space available for the motion of the molecules). It must be linearly proportional to $n$ because $b$ represents the sum of the excluded volume of each molecule in a mole. Therefore, we must multiply it by $n$ to obtain the total excluded volume.

The coefficient $a$ is said to represent the strength of the intermolecular attractive forces. Intuitively, we can say that it must be proportional to the number of molecules per unit volume. The more the number of molecules around a molecule, the more attractive forces it shall feel.

Therefore, the correction term for pressure must be proportional to $\frac{n}{V}$. But we know that in reality, it is proportional to the square of $\frac{n}{V}$.

Why does it vary squarely?


texts: Is water neutral in nature or amphoteric in nature? I understand it as an neutral compound in complex compounds, but I've been told that it is amphoteric, too.


texts: Why do we need to add Al in excess for the reaction between a nitrate and a base to give ammonia?

texts:
I don't know if why we add Al for the reaction between Nitrate and a base so it would release NH3 gas.

So what I want to know is if what is the role of Al here?
And why do we have to add it in excess?
Can we do this with every nitrate? ( in my case I came across the reaction of Sodium Nitrate and Sodium hydroxide)

And thank you for your time!


texts: Dissociation equilibria of ammonium bifluoride in water

texts:
Ammonium bifluoride or ammonium hydrogen fluoride is a salt of a weak base and a weak acid.
The weak acid is because the second equilibria of $\ce{HF}$ written as:
$$\ce{HF + F- <=> HF2-}$$
and it has constant of $\pu{3.963 M}$.
But does the bifluoride anion further dissociate?
$\ce{HF}$ in water has many species: $\ce{H+},$ $\ce{F-},$ $\ce{HF2-},$ $\ce{H2F2}$ and $\ce{(HF)_nF-}.$ The $\ce{NH4HF2}$ has a more acidic $\mathrm{pH}$ than a solution of $\ce{NH4F}$.


texts:
When certain oxides are combined in a pre-determined stoichiometry and synthesized with a ceramic-like synthesis process(power-in-tube), multiple phases may be obtained which not necessarily is same as the original stoichiometry desired. For example, in the superconducting compound $\ce{YBa2Cu3O_{7−x}}$, other ratios such as $\ce{YBa2Cu4O_y}$ (Y124) or $\ce{Y2Ba4Cu7O_y}$ (Y247) might exist in the same material.

From stoichiometry perspective,

Is there a limit on the number of oxides due to crystal lattice limitations and such?
What precautions can be taken during synthesis of these oxides when partial stoichiometries are involved?

EDIT: FCC for example, accommodates a max of 14 atoms per unit cell which YBCO does. But take for example Bi2223. https://www.researchgate.net/publication/225413281_Crystal_structure_and_superconductivity_of_Bi-2223
This has a crystal structure, unlike any traditional lattices.
The question I have is to what extent can one go to obtain desired stoichiometry? Bi2234, for instance, is hard to synthesize: https://en.wikipedia.org/wiki/Bismuth_strontium_calcium_copper_oxide. How do we know beforehand (educated guess) that a certain phase is not easy to synthesize?


texts: A question asks for physical properties of potassium nitrate, and specifically asks for "magnetic charge" and "strength" (that is how it is phrased). I have properties such as white in color, vitreous, odorless, and melting point of $\pu{334^\circ C}$. It is relatively stable, and a strong oxidizer, so it acts as a good fuel source. However, is strength asking about bond strength? And I'm not sure how to find the magnetic charge since none of my research has found anything.


texts: How was the quantum three-body problem solved?

texts: What method was used to solve the quantum three-body problem?  I heard it was solved and was not sure about the status of the problem.


texts: Using calculus to find the rate of a bivariate reaction

texts: Recently, I've been learning about rates and have found the concept fairly easy to understand in the case of a reaction with a single reactant, which is essentially solving $$f'(t) = kf(t)^n$$ where $f(t)$ gives the concentration of the reactant at time $t$. Now, for a reaction with two reactants, I'm not exactly sure how to represent the rate in terms of a function. My best guess was defining a function $r(t) = \left(x(t), y(t) \right)$ where $x(t)$ and $y(t)$ represent the concentration of both reactants respectively at time $t$, then solving $$\mid \nabla r(t) \mid=kx(t)^ay(t)^b $$ This boils down to mostly a math problem but I don't know much about multivariable calculus. I'd appreciate if anyone could provide an answer or a link to a source. Thanks.


texts: Rigorous but terse introduction to molecular orbital theory

texts: Is there a terse but rigorous introduction to MOT? I'm looking for the 'Berge's Real Analysis' of MOT, if that analogy resonates with anyone. If not, I'm looking for a book that I can use as a reference rather than a gentle tutorial.


texts: 13C-NMR of aniline: Why are carbons that are further from the amine group more downfield than carbons that are closer?

texts: A $\ce{^{13}C}$-NMR of aniline shows that the carbons further from the $\ce{-NH2}$ group are more downfield than the ones near the top of the benzene ring. If electronegative atoms like nitrogen have a deshielding effect on nearby Carbons, why is this the case? Is it because of dipole vectors?


texts: What's the difference between enthalpy of combustion and heat of combustion?

texts:
Wikipedia has two different pages for enthalpy of combustion and heat of combustion. Their definition is the same and they use the same symbol $\Delta H_c^\circ $

It says that enthalpies of combustion are always negative as these reactions are exothermic. The heat of combustion tables list positive values for all substances.
Why do these values differ in sign?


texts: Curious as to what CorA1 is and what it does?

texts:
First time Chemistry SE poster,

Was wondering what actually CorA1 is and what it actually does?

I ask because I found out I was allergic to a incredibly long list of items and this popped up to be a high allergen as I work through the list.

Google defines it as a: Magnesium transport protein CorA and it contributes to Ion transport?


texts: Can someone explain my professor's answers for these alkene additions?

texts:
(a) Why would cyclohexane expand into cycloheptane? Cyclohexane is stable.

(b) Why would cyclopentane not ring expand into cyclohexane? In the process a tertiary carbocation would be formed just like with the methyl shift, but you would also get rid of ring strain.

(c) Why is there only one product? Wouldn't the double bond have hydrogen addition on both carbon sides leading to a potential cyclobutane to cyclohexane expansion?

(e) Once again like in (c), why is there only one product shown?

(f) Wouldn't there be two products once more?

POTENTIAL EXPLANATION: By examining more mechanisms in class, I have noted that potentially the methyl/alkyl shifts could be occurring in concert with the hydrobromination so perhaps that is the reason why.


texts: Equilibrium, temperature change, and prediction in constant volume

texts:
When it's constant volume, change of $T$ (Kelvin temperature) in a reaction equilibrium system won't change the volume. Let's say we change the temperature from $T$ to $2T$ of this reaction at equilibrium

$$\ce{3A + B -> C + D}$$

Because of the change of temperature, $K_\mathrm{p}$ will change, depending on whether the reaction is exo- or endothermic. At the same time, because of constant volume and change of temperature, reaction quotient $Q_\mathrm{p}$ at $2T$ is newly formed (originally $Q_\mathrm{p}(T)=K_\mathrm{p}(T)$ in equilibrium turn to $Q_\mathrm{p}(2T)$)

Here's a question. Say, this reaction is exothermic, and $T$ is changed to $2T$. So, $K_\mathrm{p}$ should be lowered, and with $K_\mathrm{p}$ lowered, reaction also proceeds to reverse. This can also be explained by Le Chatelier's principle.

But when it is at constant volume, $Q_\mathrm{p}$ could newly form simultaneously. And if $Q_\mathrm{p}(2T)<K_\mathrm{p}(2T)$, the reaction could proceed forward even though it's exothermic with the increase in temperature.

I've done some math and it seems it only depends on how big $\Delta H$ is. So can that really happen? Or am I missing something? If what I'm saying is right, is this an expception of the Le Chatelier's principle?

(I've explained everything here, but I can explain with an example if anything is still unclear)


texts: Heterolytic vs homolytic cleavage of the C−H bond in cyclopentadiene

texts:
Consider the cleavage of the indicated hydrogen in cyclopentadiene:

The hydrogen indicated will be easily removed as $\ce{H^.}$ or $\ce{H^+}$. Assume a nonpolar medium.

My question was that would aromaticity give enough stabilization for hydrogen to be more easily removed as $\ce{H+}$?


texts: Are there any chemical compounds that disintegrate (without going into other chemical reactions; let's say in a vacuum) before reaching a melting temperature?


texts: how to Find $P_{tot}$ Given that $K_p = 28.5$ and the partial pressure at equilibrium


texts:
Currently I am attempting two questions on concentration but I am not sure if I am correct. Can someone help me with these questions? These are the questions:

  1) Calculate the volume of pure water added to dilute $\pu{0.2 M}$ $\ce{HCl}$ solution in $\pu{250 cm3}$ to $\pu{0.12 M}$ $\ce{HCl}$ solution.

$\pu{0.2 M}$ solution contains $\pu{0.05 mol}$. $\pu{0.12 M}$ solution contains $\pu{0.03 mol}$. The difference between the two solutions is $\pu{0.02 mol}$ (Which is how much water was added), so

$$V(\ce{H2O}) = 0.02 \times (2 \times 1 + 1 \times 16) = \pu{0.36 L}$$

  2) Calculate the mass of $\ce{Na}$ that will form $\pu{0.15 M}$ solution of $\ce{NaOH}$ by reacting with $\pu{400 cm3}$ of water.

I know that this method is totally wrong but I'll show you:

$$\pu{0.15 M} = \frac{n}{0.4} \implies n = 0.06$$
$$m(\ce{Na}) = 0.06 \times 23 = \pu{1.38 g}$$

where $n$ just refers to the concentration ($C = n/V$).

Edit:

Thanks to @George Tian I have made another attempt for the second question.

I have calculated the number of moles of NaOH for a 0.15M solution:

c = n/v
n = 0.4 x 0.15
  = 0.06

And I calculated how much Na is needed for this reaction:

The balanced equation is: 2 Na + 2 H20 -> 2 NaOH + H2
So, 0.06 mol of Na is needed (Due to the molar ratio)

Then I converted moles to grams

Mass = 0.06 x 23
     = 1.38 g


texts: What are the intermolecular and intramolecular forces between Hg molecules/ atoms in liquid mercury?

texts:
Mercury is the only metal that is liquid at room temperature.

I know that metallic bonding exists between metal atoms but my knowledge is limited to metallic bonding found in solids. Will there be metallic bonding between $\ce{Hg}$ atoms in the liquid phase?

  Moreover, there will be London dispersion forces between the $\ce{Hg}$ molecules.

Does mercury liquid only have metallic bonding as the intramolecular force and London dispersion force as the intermolecular force?

If liquid mercury (with both metallic bonding and LDF) is compared with a hypothetical liquid that has hydrogen bonding along with LDF, will the boiling point of mercury be higher than the aforementioned hypothetical liquid?


texts: Distribution coeffecient without concentrations

texts:
From what I understand about distribution coefficient is straight from my book — which does not give any practice examples — is that

$$D = \frac{C_\mathrm{A}(\text{ext})}{C_\mathrm{A}(\text{orig})}$$

where $C_\mathrm{A}(\text{ext})$ and $C_\mathrm{A}(\text{orig})$ represent the total concentration of all analyte species present in the two phases regardless of chemical state. Below is a homework problem that I'm try to solve, but having no luck, since I'm not given any concentrations, only weight and volume.

  In an extraction experiment, it is found that $\pu{0.0376 g}$ of an analyte are extracted into $\pu{50 mL}$ of solvent from $\pu{150 mL}$ of a water sample. If there was originally $\pu{0.192 g}$ of analyte in this volume of the water sample, what is the distribution coefﬁcient?

The answer for this problem is $0.731\%$, but no matter which way I plug in the numbers that are given do I reach this answer. Any ideas on what I'm missing?


texts: Is NMR possible using nitrogen as the nucleus?

texts: Is NMR spectroscopy performed using nitrogen nuclei? If yes, then where?


texts: Merge rigid parts and flexible results after docking (Vina)

texts:
If I use flexible residues in the binding pocket, they are cut from the file.

The protein is broken and the amino acids are unbound in the room.

How can I get my results and the protein together again?


texts: What is the flow of electrons, cations, and anions in a voltaic cell (please see image attached)?

texts: This is an IB question. The mark scheme says that the correct answer is A and only A. But I believe B is also correct. The following is my thought process. Since A is more reactive, it undergoes oxidation to form A2+ ions, while B2+ ions undergo reduction and form B. From this we can deduce that A is the anode and B is the cathode. According to my notes and many sources on the internet, electrons and cations both travel from the anode (A in the image) to the cathode (B in the image). Therefore, A and B would both be correct. Please can someone confirm my thinking or point out any mistakes. Thank you


texts: Why would permeability for krypton be higher than argon?

texts:
So, I've been looking over data on permeabilities and there's something that bothers me.  Permeability data on the noble gases is somewhat hard to find, but the Parker O-Ring Handbook has them for a number of materials:

http://www.parker.com/literature/O-Ring%20Division%20Literature/ORD%205700.pdf

(as an example material to choose in the list, say, PTFE)

What I don't get is... why is the permeability rate for krypton usually higher than that of argon for most materials? ?  Their chemical properties are basically identical, krypton is just a larger atom.  By all standards one would expect it to permeate slower.  Xenon permeates slower than both of them, as expected.  So what's up with krypton?


texts: Does the Hofmann Rearrangement extend to Secondary Amides?

texts:
I have read where it is explicitly stated that the Hofmann Rearrangement is a reaction whereby primary amides are converted into primary amines with one less carbon. I have tried to find examples where a secondary amide is used, but haven't been able to find it addressed anywhere. I have been able to find examples where a N-hydroxylamide is used, but that's still a primary amide.

What happens when a N-methylamide or an N-methylhydroxylamide is subjected to Hofmann Rearrangement conditions?