texts: Nucleophilic Substitution Reactions help

texts:
Which halogenoalkane reacts fastest with sodium hydroxide?

A. 1-iodobutane
B. 1-chlorobutane
C. 2-chloro-2-methylpropane
D. 2-iodo-2-methylpropane

Iodine has a larger radius, thus less electronegative making it a better leaving group. And since OH is a protic substance it favors Sn1, which is a tertiary, so the answer must be d... but it says that the answer is b.. how????


texts: For reactions involving gases, an increase in pressure is no different from increasing the concentration of reactant particles, thus increasing the rate of reaction. But for reactions involves different phases, such as both solid and liquid, what will the pressure increase cause? Will it increase the rate of reaction? Or, because the rate also depends on other reactants and in reactions involving different phases, will pressure not change significantly even if gas is present?


texts: Origin of the names “thionyl” and “sulfuryl”

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Compounds in question:

Thionyl chloride - $\ce{SOCl2}$
Sulfuroyl dichloride/Sulfuryl chloride - $\ce{SO2Cl2}$

I understand that the "thio" prefix is often used when sulphur replaces oxygen in its compounds, like "thioalcohol" or "thiosulphate". I also note that sulphur and sulfur for the same element $\ce{S}$.

However, even after countless attempts, I manage to swap the two compounds with each other, and have not been able to accurately identify their formulae when their names are given (and vice-versa). So, if someone asked me the name of $\ce{SO2Cl2}$, I would respond with thionyl chloride or sulfuryl chloride, and never be sure which one is which.

The names of other inorganic compounds are generally logical and memorable. The use of prefixes like meta, ortho, per, etc. is logical as well. However, these two sulphur compounds are very confusing. This makes me ask the question:

  What is the rule/logic/reason behind the naming of these two inorganic compounds?

I hope if I know the reason I'll be better able to recall their formulae from their names and vice-versa.


texts:
When reducing an oxide with carbon what would be the product? I think it would produce $\ce{CO2}$ and then the $\ce{CO2}$ would react with $\ce{C}$ to give some amount of $\ce{CO}$.  For example:

$$\ce{2CuO + C -> 2Cu + CO2}$$


texts: First ionization energy of hydrogen molecule

texts: If we have the dissociation's energies of hydrogen molecule $\ce{H_{2}}$($D_{0}$) and the corresponding molecule ion $\ce{H_{2}^{+}}$ ($D_{1}$) together with the first energy of ionization of hydrogen atom ($E_{I}$), how can we estimate the first energy of ionization of hydrogen molecule?


texts: How can CO2 exist in two different phases?

texts:
Given a container of $\ce{CO2}$ at a pressure of 100 bar and 295 K, I check the chart below and find:

I'm within the liquid region
I'm before the critical point (304 K)

My question then is, why can I go purchase a tank filled at 100 bar that contains both liquid and gas?  What stops the gas from condensing, since according to this chart, the pressure and temperature map to a liquid phase.


texts: What are the mechanisms for capture of As(III) and As(V) by magnetite from water?

texts:
Magnetite, $\ce{Fe3O4}$ is able to capture $\ce{As(III)}$ and $\ce{As(V)}$ from drinking water through the following mechanisms.

Bidentate-binuclear complex

Monodentate-binuclear complex (both from here)

I'm assuming these are standard reactions in inorganic chemistry, but are there known mechanisms (I don't have a text available)? The first looks like an attack on the $\ce{As}$ by the $\ce{O}$, but the second seems to take place in two steps.


texts: Calculation of rate constant for bimolecular reaction from Gaussian DFT calculations

texts:
I am working with a bimolecular reaction for which I have computed the energy profile. I have output files for TS and reactants which I intend to use for rate constant calculations. From TST we have:

$$k=\frac{k_{\mathrm B}T}{h}\frac{Q^{\ddagger}}{Q_A Q_B}\exp\left(\frac{-E^\ddagger}{RT}\right)$$

But how do I calculate the rate constant from the Gaussian output? I know how to find $E^\ddagger$, but the partition functions are teasing me. In the output file values for $Q$ are shown both for the vibrational motion, the electronic, the translational, and the rotational:

I have found that $Q=q'_\text{trans}q_\text{rot}q_\text{vib}q_e$

I am not too sure about what the prime in $q'_\text{trans}$ means other than it might have something to do with the translational function being per unit volume.

I have stumbled upon a book where it is explained that you have to convert the translational function to being per unit volume to get the correct units of $\pu{m3 mol-1 s-1}$ for bimolecular reactions. I do not quite understand this nor which of the vibrational partition functions to use (Total Bot or Total V=0).

Furthermore, I am uncertain if the unit of $\pu{mol-1}$ is just obtained by multiplication with the Avogadro constant and what the unit of the translational partition function exactly is. I thought the unit was $\pu{m-3}$ based on:

$$\operatorname{dim}q_\text{trans}=\frac{\operatorname{dim} q^\ddagger}{(\operatorname{dim} q_\ce{A})(\operatorname{dim} q_\ce{B})}= \frac{\mathsf{L}^{-3}}{(\mathsf{L}^{-3})(\mathsf{L}^{-3})} = \mathsf{L}^{-3}$$

But with introduction of the relative translational motion per unit volume as explained in the link, I am confused of where the unit comes into play.


texts:
I know that a neutralization reaction (i.e. a reaction between an acid and a base) results in the formation of a salt and water, but when I came to know that $\ce{Fe(OH)3}$ is salt, I began to have doubts:

If bases are ionic compounds that break apart to form a negatively charged hydroxide ion ($\ce{OH-}$) in water, then why is $\ce{Fe(OH)3}$ is salt and not a base?


texts: Suggest the product from two-substituted benzene ring

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Which are the possible products from this reaction?

The answer in the mark scheme shows that it should be as demonstrated as pic A.
However, I think it could be either A. or B. since both substituted groups of the benzene ring, NH2 and Cl, direct the incoming electrophiles to attack the 2,4 and or 6 positions. Do I understand correctly?

I have never come across two substituted groups before. Should I consider both NH2 and Cl as substituted groups or only one of them, but which one? Also, how to count the position of carbon on the benzene ring in this case?

Please help! Any help would be much appreciated.:)


texts:
I was willing to understand a little bit better the physics behind iceskating.

Messy thoughts

From New Scientist (1964) (probably not the most up-to-date reference $\ddot \smile$), I found a diagram showing the relationship between both the static and kinetic coefficients of friction and the temperature (x-axis is reversed) for ice.

When we ice skate, we put a big pressure on the ice. As the ice is less dense than liquid water, this pressure may eventually be high enough to turn ice into liquid water. Intuitively I would think that high pressure would yield to high temperature but I suppose that this would hold true exclusively for gazes ($PV=nRT$). In any case, I don't quite have a good intuition for why warmer (or more pressurized eventually) ice would decrease the coefficient of friction of ice.

Questions

What is the intuition behind the fact the coefficient of friction of ice decreases as temperature increases?
Does the coefficient of friction of ice decreases with higher pressure too? For the same reason as above? As a correlated-side effect of increasing temperature?
Why do ice skates slide so well? Because it puts a high pressure on the contact surface or because it puts a high pressure on the contact surface which in turn increases the temperature?


texts:
Is there any trick to memorize the angles and sides of 7 crystal systems of crystalline solids?
1. Cubic
2. Tetragonal
3. Orthorhombic
4. Monoclinic
5. Hexagonal
6. Rhombohedral or Trigonal
7. Triclinic


texts: Determine and draw planes and axes of symmetry of a molecule using software (VESTA or Mercury)

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I designed the $\text{MoS}_2$ molecule (bilayer), with polytype 2H in the VESTA. My goal is to draw the plans and axes of symmetry of the bilayer set. According to the information in the literature, this molecule belongs to the $\text{D}_{3d}$ point group. How can I draw and determine the planes and axes of symmetry in VESTA?

These are the parameters I used in VESTA:

Mercury Attempt:

I exported the .vesta data to a .cif file.

Table with space and point groups for $\text{MoS}_{2}$ (taken from https://iopscience.iop.org/article/10.1088/0953-8984/28/35/353002/ampdf) (see 2H phase for $\text{MoS}_{2}$):


texts: How does molecular orbital theory explain CH4?

texts:
I have understood the formation of $\ce{CH4}$ by valance bond theory, but I'm having trouble understanding it through molecular orbital theory.

The energy level diagram of molecular orbitals of $\ce{CH4}$ is not clear to me.


texts: Electrochemical characterization of benzenesulfonamide

texts: I'm trying to elucidate current peaks for benzenesulfonamide, using an acetic acid-sodium acetate 0.1M buffer at pH 5.5 as electrolyte. When doing cyclic voltammetry, I get a voltammogram similar to the platinum (Electroanalytical Chemistry and lnterfacial Electrochemistry, 43 (1973) 9-36), because I use platinum as a working electrode. So, I can not see any current peak related to benzenesulfonamide, and I have not found any article related to this. I've been thinking about using a glassy carbon electrode instead of platinum.


texts: Why doesn't hydrogen peroxide decompose into hydrogen and oxygen?

texts: I'm trying to understand why hydrogen peroxide doesn't decompose into $\ce{H2}$ and $\ce{O2}$, but instead into $\ce{H2O}$ and $\ce{O2}$.


texts:
My two questions: Is replication of recording $\text{IC}_{50}$ values prior to (primary?) publication less common than performing a reaction several times to determine a more reliable record? Provided the very small quantities used in these tests (vide infra), should a synthetic chemist rather stay skeptic if a newly isolated material is described as highly potent?

In a literature seminar, the story/history of maoecrystal V, a highly congested polycyclic natural product was presented:

(source first part of an overview)

Initially, both the molecular architecture as well as the the $\text{IC}_{50}$ value ($\pu{0.02 ug/mL}$ at a molar mass of $\pu{330 g/mol}$, $\pu{60 nmol}$) in comparison to cis-platin ($\pu{0.99 ug/mL}$ at a similar molar mass of $\pu{300.01 g/mol}$) against cervical HeLa cancer cells reported by Li et al. in  Org. Lett. (doi 10.1021/ol0481535) in 2004 triggered the interest of several chemists to synthesize this material.

About a year ago, the Baran group published again efforts towards this compound (doi 10.1021/jacs.6b06623, ACS AuthorChoice / open access), displaying again tremendous efforts in the lab.  With larger quantities of the material in hand, however, the initially claimed activity against cancer cells (not only against HeLa) could not be confirmed.

The supporting information of the last paper sheds some light on the frugal scale the $\text{IC}_{50}$ values were recorded:

  Synthetic (–)-maoecrystal V (1) was dissolved in 100% DMSO at a     concentration of 1 mM. [...]  A day after cell seeding, 10 μL of prediluted compound was added to the cells (1:16 dilution).

Which would refer to low umol quantities of the material deployed per test.  Still, the question arises why the initially reported activity differs so greatly from the one eventually determined.  (Speculation: perhaps fewer groups would have joined the challenge to prepare the material if interested merely in its architecture.)

Addition

For the interaction of Maoecrystal V and other, already known, agents for example facing HeLa cells, page S52 of the SI of the 2016 publication shows this plot:

Note that Actinomycin D is considerably heavier ($\pu{1255 g/mol}$) than Maoecyrstal V ($\pu{330 g/mol}$).


texts:
I find very little data on the solubility of tyrosine, other than that it has a very low solubility at room temperature for an AA. (1)
Does anyone know different ways to dissolve fair amounts of it in water (preferred) or an organic solvent?
I suspect I could increase its water solubility by decreasing the $\mathrm{pH}$ and increasing temperature, but I'm not sure what is the best way to do it, which would be the most effective, and by how much it would increase the solubility.

(1) https://pubchem.ncbi.nlm.nih.gov/compound/Tyrosine#section=Solubility


texts: Are there square planar complexes with sp2d hybridization?

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We were taught (Under the section 'Valence Bond Theory') seven types of geometries a transition metal complex may assume and its corresponding hybridization states,

Linear - $\ce{sp}$
Trigonal planar - $\ce{sp^2}$
Tetrahedral - $\ce{sp^3}$
Square planar - $\ce{dsp^2}$   (Inner d-orbital involved)
Trigonal Bi-pyramidal - $\ce{dsp^3}$  (Inner d-orbital involved)
Square Pyramidal - $\ce{sp^3d}$   (Outer d-orbital involved)
Octahedral - $\ce{d^2sp^3}$   (Inner d-orbitals involved)

We were told that there are quite a few instances (for Octahedral complexes), where the outer, vacant d-orbital takes part in hybridization, so the hybridization state would thus become: $\ce{sp^3d^2}$

Now my question is:
Are there Square Planar complexes in which the outer, vacant d-orbitals take part in hybridization (i.e- are there square planar complexes with sp2d hybridization) ? If so, could someone provide a few examples.


texts: Preparation of a fluoride solution using CaF2

texts: I need to prepare several solutions with different concentrations of $\ce{F-}$, in order to carry out some investigations on fluoridated water. Would this be achievable by dissolving calcium fluoride, $\ce{CaF2}$, in water? Wikipedia writes that $\ce{CaF2}$ is insoluble in water, so I am not sure.


texts:
Cyclohexene is reacted with bromine in carbon tetrachloride in the dark. The product of the reaction is:

I know that reaction with bromine in $\ce{CCl4}$ will result in vicinal dibromocyclohexane. So the answer is either A or B. But how to decide between A and B? Since its an SN2 reaction it would lead to inversion of the reacting compound. Does this have to do anything with the answer?


texts: Resonating structures of (pentan‐2‐ylidene)oxidanium

texts:
Draw resonating strictures of the following compound:

In this molecule there are two π-components, but they are not conjugated.
According to me, as there is no conjugation, it should not have a resonating structure.
But it has. Why?


texts: According to what criteria was the periodic table of elements ordered?

texts: I was wondering why the elements in the periodic table were disposed the way they are. I understand, of course, that they are put in increasing atomic number fashion, but I'd like to know more about the topic. Could you link some reference that examine in detail the structure of the periodic table?


texts: Why are we finding the integrated rate law by starting with r=k[A]?

texts: When deriving the integrated rate equations, we start off with r =k[A] for example, and then we do the whole integration thing to find an equation of [A] in terms of time. But why are we ingnoring any other reactants here? Wouldnt the r=k[A][B] if B was was another reactant?


texts: Product formed under ethoxide/ethanol and heating?

texts:
What would be the major product of the following reaction sequence?

I believe that the first step will be the formation of a radical at the first carbon of the ethyl group because benzylic radicals are quite stable. However, I'm not really sure what happens after that. The answer key has 'I' as being the correct answer.


texts: method to certify the number of chiral carbons in fischer and haworth projection of glucose

texts:
While reading some notes about Glucose and its various projections:

Fischer Projection: 4 chiral centres

Haworth Projection: 5 chiral centres

My doubt is that is there any (specific) method (practical) to ascertain the number of chiral centres in both the forms.
I know that more than 99.5% of glucose exists as Haworth Projection - Closed Ring Structure and hence Linear - Fischer Projection practically does not exist.
But it (linear ie open chain glucose) could be always isolated though difficult.
Thank you!


texts: Identifying Structure based off 1H-NMR & Mass Spectroscopy Data

texts:
I have almost the whole night trying to identify this structure with no avail as there is always one part that does not fit. The determined formula for this structure was $\ce{C13H17BrO}$ from the $m/z=268$ (M-100%), $m/z=269$ (M+1-14.7%), and $m/z=270$ (M+2-98.6%).

The $\ce{^1H}$-NMR data is as follows with integration in parentheses:

a. $\pu{7.30-7.27 ppm}$: multiplet (5) - arene with 5 hydrogens

b. $\pu{3.20 ppm}$: singlet (2) - R-CH2-Br attached to tetra-substituted carbon?

c. $\pu{2.45 ppm}$: triplet (2) - R-CH2-CH2-CO-CH3

d. $\pu{2.17 ppm}$: singlet (3) - R-CH2-CO-CH3

e. $\pu{1.68 ppm}$: sextet (2) - R-CH2-CH2-CH3

f. $\pu{0.90 ppm}$: triplet (3) - R-CH2-CH3

And this is the structure I come up with:

which is the only structure that fits all the hydrogen integrations, but does not support the chemical shift at all.

I believe this is part of the molecule

because it takes care of shifts d,c,e,f. However, it is impossible to attach that structure to the remaining Arene, CH2-Br, and tetra substituted carbon. Actually spent over 6 hours on this problem and I'm losing my mind please help me.


texts: Could blue flames arise within the hull of a burning ship?

texts:
In Joseph Conrad's Youth: A Narrative, set in 1876, a 400-ton barque ship, the Judea, is sent to Java Head to transport 600 tons of coal. Although various delays occur during its journey, the coal it is carrying spontaneously combusts while off the coast of Western Australia. The crew attempt to smother the fire, unsuccessfully. Then attempt to flood the fire, but this is also unsuccessful. Finally, the gases in the hull explode and blow up the deck, and the crew hail a steamer to tow them to an intervening location. However, during their towing, the speed of the steamer's ship cause the fire currently present on the Judea to smoulder into flames, which the narrator describes thusly:

The speed of the towing had fanned the smoldering destruction. A blue gleam appeared forward, shining below the wreck of the deck. It wavered in patches, it seemed to stir and creep like the light of a glowworm

My questions:

Given the amount of fuel and material of the ship available, is it possible that a blue fire of 2300-3000 degrees Celsius (from a quick Google search), could be produced within the hull of the Judea?

Or is it the case that due to the nature of coal gas, a lower temperature than aforementioned need only be met for flames to appear blue, similar to how the flames of a gas stove appear blue?

Additional information, if helpful:
At its last port to Java Head, the Judea had been recalked and copper sheathed before embarking on the last stretch toward Java Head. The Judea explodes and is towed at night.


texts: Halogenation of an alpha-halogen ketone in acidic conditions

texts: When a methyl ketone is submitted to halogenation in acidic conditions with two equivalents of a halogen, the first halogenation happens at the secondary alpha carbon atom , while the second halogenation happens at the primary alpha carbon atom. Why is it so? Why doesn't it happen on the same carbon atom (the secondary one)?


texts: Modifications and alterations in the state of chemical equilibrium

texts:
Let us consider that we have a mixture of gases, considered ideal, that is in balance. Like, for example,

$$3\ce{NO} (g) \rightleftharpoons \ce{N2O} (g) + \ce{NO2}(g)$$

If we consult the thermodynamic tables, we can appreciate that the reaction is exothermic and exergonic.

This thermodynamic state of chemical equilibrium can be altered depending on various parameters, such as temperature or pressure.

Modification of the temperature: If we increase the temperature, the system moves in the endothermic direction, that is, towards the formation of products. This rule is well known, but I would like to be able to justify it by mathematical reasoning. I have thought about Van't Hoff's equation, but since I do not know the value of the equilibrium constant at a certain temperature, I have not been able to use it.
Modification of the volume. This is where I have the most doubts. I need to determine which way the system is moving. I know that the system moves to where it is least bothered, in this case, to the right. But, again, I wonder if this can be justified mathematically. I seem to remember my physical chemistry teacher doing it based on the definition of K (considering partial and constant pressures of fugacity)
If a non-inert (reactive) gas is added to the equilibrium mixture Here I know that there are several cases to distinguish:
3a) If the total volume is not modified
3b) If the total pressure remains unchanged
3c) If the temperature remains unchanged
3d) If the intensive variables can be modified
But, really, this one I have no idea how to reason with.
If we add an inert gas, any noble gas, I'm not sure what to do either.

I know the question is a long one. But, I have tried to reason out everything I know about the subject (basically, Le Châtelier's principle). But, I need to justify it on the basis of mathematical reasoning, since my teacher has told me that, in some cases (which are not many), Le Châtelier fails.


texts: Simple alternative to UNIFAC to prove that a mixture containing 1ml of x and 5 litres of propylene glycol is not flammable?

texts:
Section 2.6.1 of the REGULATION (EC) No 1272/2008 (CLP) defines a flammable liquid as:

  Flammable liquid means a liquid having a flash point of not more than
  $60 ^{\circ}$C.

So data on flash point are needed for the classification of a liquid.
The CLP goes on to state that data can be determined by testing, found in literature or calculated.

In the case of mixtures the flash point need not be determined experimentally if the calculated flash point of the
mixture, using the method described in Gmehling and Rasmussen (Ind. Eng. Fundament, 21, 186, (1982))], is at least 5°C greater than the legally defined threshold/s. This assumes that the liquid is homogenous and we know certain details about the components.

I have had a look at this method which appears to be called the UNIFAC method. As a non-scientist, it looks overly complicated for situations where you just intuitively know that a mixture is not going to be flammable.

I have a hunch that if I pour 1 ml of food flavouring into a 5 litre bottle of propylene glycol (PG) the resulting mixture is not going be classed as 'flammable' (where the flash point of PG is deemed to be 104°C ).

Is this hunch one of those areas where science and intuition conflict?

Does it make sense to perform the whole UNIFAC process to confirm this conclusion or is there a simpler (but still scientific) 'rule of thumb' that we can use to discount having to perform a UNIFAC method?

For example, if I have a mixture containing:

1 ml of pure water, which as far as I can tell has no flash point, and
2 litres of PG (flashpoint 104°C)

Is the UNIFAC process the simplest way to determine the flammability of this mixture or is there a simpler, yet reliable, method to determine the flammability of this mixture?


texts: Significance of single point energy when calculating interaction energies

texts:
I am currently investigating about the interaction behavior of a few atoms in certain conditions.

Is it possible to use the concept of single point energy to represent the atomic interaction energies or I have to go other way around?
What is the basic difference between potential energy and single point energy?


texts: How to synthesize a material at 2000atmospheres?

texts: I am trying to combine various elments and at high pressure. How to achieve these pressures for a gas and in quantities of at least 1 cubic centimeter.


texts: Why doesn't liquid propane in a closed coke bottle burst?

texts:
I was watching this YouTube video in which the original experiment was to make a small rocket out of liquid propane and Coke. When that failed, the person doing the experiment decided to try pouring liquid propane into the Coke bottle and closing the cap on it to see what would happen.

I would have expected (and I believe he did too) that the bottle eventually would build up enough pressure to explode. However, that did not happen and along with that not happening, the liquid appeared to warm up to about air temperature and stopped boiling. When he opened the lid of the bottle, it quickly depressurized, the liquid began boiling and returned to its normal, cold state.

My guess is that once the propane vapors filled the bottle and expanded sufficiently, it put enough pressure on the liquid to keep it from boiling. So my question here is, is my guess correct and, along those lines, if it had been warmer outside, would that bottle have built up enough pressure to explode?

Note: Even if my guess is correct, I want to see the hows and whys of it in an answer.


texts:
It has 4n electrons and is completely conjugated. It should be anti aromatic.

Why is this compound non-aromatic?


texts:
Adiabatic process is isentropic, but I can't get it why is it so. If we go by statistical method
$$S = K\ln W,$$
where $W$ is the thermodynamic probability, and if we look into adiabatic expansion the volume increases, we can say that the thermodynamic probability increases, and hence the entropy of the system should increase.
Moreover, if we look into isothermal expansion of an ideal gas in vacuum, there would be no work done, and so no heat would enter or move out of the system. But since there is a change in volume, we can write
$$∆S = nR\ln\frac{V_2}{V_1}.$$


texts: Regenerating the imaginary data of a 2D NMR spectrum with a hilbert transform

texts:
2D spectrum take up a large amount of hard disk space. At my last lab it was standard practice to delete the imaginary portions of the spectrum with xfb n (We used TopSpin) and if needed later, to regenerate it from the Real part of the data with a Hilbert transform (Related, the TopSpin Commands and References, ~pg P-233 in version 2.1.2)

My first question: If the raw data is still stored in the ser file (TopSpin Commands and References v2.1.2, pg P-8) why can't you just reprocess the raw data? Is all the data not there? (I suspect this somewhat, as those files are much, much smaller then the processed files, and TopSpin processes 2D spectra as it acquires them, unlike 1D spectra)

My second (highly related) question: Is there a downside to regenerating the imaginary data from the real data? Is it a perfect replication of the original data, or is it an approximation? Why do we ever bother to store this data if we can recreate it at any time?


texts:
If I use a iron rod to hit a 3" × 12" iron plate there is the distinct sound of a metallic ring.

What is the cause of this distinct sound? Is it the crystal structure of iron or that iron is a metal and most metallic objects will ring when struck?


texts: lowest energy conformation of butan-2,4-diol

texts:
Do the OH groups want to be furthest apart? or the CH3 groups?

I'm trying to determine the lowest energy conformation - and I don't know which group has the bigger steric effect?


texts: What easily available chemicals do I use to turn oak light grey?

texts: I have 10 square meters of dry and freshly sanded oak that I would like to artificially age/weather to the colour of the above photo. Once treated the oak is to be used for a bedroom interior. I was wondering if there are any chemists out there who may know how to do this.


texts: Is there ANY chemical that can destroy PTFE, or Teflon?

texts:
Polytetrafluoroethylene was discovered by accident. It now is an important material in the industry mainly because of its extremely high bonding energy, which prevents corrosion, halts reaction, and reduces friction (yeah carbon-fluorine bonds!)

And people would have definitely put it to the test, making it contain some of the most vicious and chemically diabolical substances ever created. There is a whole HOST of items it can contain that some chemists have gone so far as to say they were 'evil':

Dioxygen Difluoride
Known as the gas of Lucifer, there is a whole list of people blown up and killed while just trying to work with one of its components, fluorine. It ignites stuff at temperatures that most of the stuff that we breathe in would be in liquid form. No one really knows about its atomic structure (obviously).
Fluoroantimonic Acid
With a staggering pH of -25, it chews through stuff you might not even believe could be corroded; like wax or glass. It can even strip hydrogen off of methane

...There are a lot of other chemical demons it can contain, but this is not the point. Let this suffice: Chemical Resistance Comparison (Spoiler: Fluorine is good at this corrosion thing.)

With this kind of hyper-resistance to about anything chemically destructive, is there anything that can destroy Teflon through only chemical means? A chemical that reacts exothermically to release heat, which melts the PTFE does not count. You get the drift.

Also, I am very curious as to whether there is anything more resilient than Teflon? Polytetrafluoroethylene is made of many carbon-fluorine bonds in series. However, carbon-fluorine is second only to the Si-F bond. Is there an "overclocked" Teflon made of silicon-fluorine bonds that is even stronger?

EDIT: Now I know that some, but very few, solvents can make a mark on Teflon; but my question has not been answered: Is there any more resistant substances?

(More Teflon bragging: Here. Take that aqua regia)


texts:
My 7th grader is embarking on a long-term science project and I'm on tap to "help." He is showing a strong interest into finding ways to get drinking water to the masses. His idea is that we need to find inexpensive and efficient desalination processes. So, we are exploring current desalination processes to see what makes it "expensive" and "inefficient."

However, we live in the Rocky Mountains and don't have access to proper sea water. We started to explore simply adding salt to tap water and researching how much. Then, we discovered "Artificial Sea Water" or "ASW" is a common creation in science. Because sea water contains more than just salt. It contains chemicals like fluoride, strontium, boron, bromide, inorganic carbon, potassium, calcium, sulfate, magnesium, chlorine and of course, sodium. I am not a chemist, so this is starting to look daunting.

So, here are my questions to counsel my son:

To experiment with desalination, is adding salt to tap water
sufficient or do we need to investigate finding official ASW?
How do we test the salinity of water? Do I really need to invest
hundreds of dollars on a salinity meter?


texts: What is the pH of a solution of iron acetate?

texts:
What is the pH of a $\ce{0.1 M}$ solution of $\ce{Fe(CH_3COO)_3}$? I'm not sure how to do this, as it would involve complicated mass balance equations, but I think I can apply the approximation $\ce{pH = \frac{1}{2}*(pKa(Fe^{3+}) + pKa(CH_3COOH)) = \frac{1}{2}*(4.76 + 2.22) = 3.48}$.

Is this approximation valid in this situation? If not, how would I correctly calculate the pH of the solution without solving complex mass balance equations?


texts: How to calculate the depression in freezing point of a solution in which there are multiple solutes being added?

texts:
In just about every problem I've encountered earlier, all such questions describe the process for calculating the depression in freezing point for a solution wherein there is only one solute. However, on a take-home exam, we were asked to solve the following problem:

What is the freezing point of a solution containing $\pu{0.2 mol}$ glucose and $\pu{0.2 mol}$ $\ce{KCl}$ in $\pu{250 g}$ $\ce{H2O}$?

My thinking is to use the general formula
$$\Delta T_\mathrm{f} = imK_\mathrm{f}.$$
What I'm concerned about is how to reconcile the multiple molalities, as both glucose and $\ce{KCl}$ have the same molality, but ought we add them together? Multiply them? Just a little confused.
Also, he gave us a set of “useful equations”, but on the sheet he did not specify a van 't Hoff factor for $\ce{KCl}.$ This is confusing to me because I'm pretty sure that $\ce{KCl}$ is a strong electrolyte and ought to have one. Should we just assume $i = 2$ since there are two species $(\ce{K+}$ and $\ce{Cl-})$ we are sure to get afterwards?


texts: I dipped a sticky note in water and there was a clear difference between the water absorption in the area with glue and the one without glue. The area with glue was more damp than the one without it. I would like to know why.


texts: When a molecule loses hydrogen atoms, does it become oxidised?

texts:
I had the following question on a bio test covering cell respiration and glycolysis, but I'm not sure if I agree with the answer.

  When a molecule loses hydrogen atoms (as opposed to hydrogen ions), it becomes
  B) oxidised

According to my textbook (Principles of Life, 2nd Edition), oxidation is defined as

  Relative loss of electrons in a chemical reaction; either outright removal to form an ion, or the sharing of electrons with substances having a greater affinity for them, such as oxygen. Most oxidations, including biologial ones, are associated with the liberation of energy.

Hydrogen atoms have one proton and one electron in their typical state. If a molecule is losing hydrogen atoms, then its net charge wouldn't change. For example, if a (hypothetical) molecule had 7 protons and 6 electrons, it would have a charge of +1. If it then lost a hydrogen atom, it would now have 6 protons and 5 electrons, which still yields a net charge of +1. Am I missing some critical piece of information, or is this still considered oxidation?


texts: In my textbook it is written that primary valences are ionizable. I saw a case of complex $\ce{[Co(NH3)5Cl]Cl2}$  Here it is written that primary valency is 3. The $\ce{Cl}$ inside coordination sphere serves as both primary and secondary valency. Since the constituents inside are non ionizable, will it be right to day that primary valences are always ionizable?


texts:
Is NH4Cl Dative or Ionic or Covalent ?
I made the Lewis structure but I was not able to make it...
After many tries I posted this question
Some where I saw that they are made up of Ions but contain Covalent bond..


texts: Why and how does lycopene absorbance increase with heating?

texts:
Lycopene, which is a carotenoid and a phytochemical is the main reason for why tomatoes are radio-protective.

Source 1, Source 2

Let's cut to the chase: I was wondering if this claim of this source is of scientific value:

"Heating will result in an increase in amount of lycopene absorbed by the body."

It may be possible that the researcher made a more "every-day" statement for the readers to understand.

I have two questions:

Is the statement scientifically correct?
If so, why and how would such a chemical be absorbed more with the heating process?

Note that if you want to make the argument that this is a biology question rather than a chemistry one, I would bring up these reasons:

The temperature in which the heated lycopene and raw tomato are going to be absorbed in the body are the same. Thus, it might be possible that heating lycopene results in a chemical reaction.
I'm not looking for the pattern of absorption by the body. I'm looking for possible changes or specifications of its structure.


texts:
Why is HOOH such a good oxidizer?

I understand that the oxygens in HOOH are in a negative 1 oxidation state, and that oxygen generally adopts an oxidation state of negative 2.

I also know that oxidizers themselves are reduced, and that reduction entails a drop in oxidation state. This suggests to me that oxygen is more stable when found with a negative two oxidation state rather than a negative one oxidation state. This makes sense; oxygen is the second-most electronegative element on the periodic table, so it likely would be okay with a more negative oxidation state.

And from organic chemistry I understand that the O-O linkage in peroxides is relatively weak; light can rather easily homolytically cleave the O-O linkage. And HOOH is generally stored in dark bottles as to block light. This says something about thermodynamic stabilities to me - that HOOH has relatively weak bonds and that it would be enthalpically favorable for the oxygens to form other, stronger, bonds. Is this how HOOH is used in bombs? The O-O bond is weak; bond formation is exothermic, thus providing a way for the O-O bond to break and rearrange into stronger bonds releases vasts amount of energy?

I'm trying to tie together redox with thermodynamic stabilities.


texts: Heterogenous equilibrium nernst equation

texts: In the nernst equation, when a gas - ion electrode is used eg when we write the equation for standard reduction potential for a particular electrode : we get a term of activity of h2 gas and h+ ion. We respectively put 1 atm and 1 molar. However how can we use partial pressure and molarity in the same expression for Q? Shouldn't it be one or the other?


texts: Iron Filing Catalyzed Toluene Reaction with Bromine Solution

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When toluene and a bromine solution react, there is no reaction. That is, the solution turns a yellow/brown colour, the same as the bromine solution.

I conducted an experiment where toluene and a bromine solution were meant to be catalysed by iron filings. However, instead of the solution losing its colour (like you'd expect in an alkene/alkyne), it became rustic in colour. If the iron filings were intended to catalyse the reaction, why did the solution become darker? The reaction that took place seems entirely counter-intuitive.


texts: Proper (and safe) way to pressurize a vessel to around 70 kPa with gentle (~38* C) heat

texts:
I'm trying to force crystallization in a complex mixture by maintaining gentle pressure and heat. I'm thinking of using a Duran pressure plus bottle with a cap that has 2 GL-14 fittings, one attached to a compressed air pump and the other with a pressure gauge with release valve. I'm also considering Ace Glass pressure vessels. I don't have any experience working with pressurizing vessels and want people's input.

Thanks!


texts: Precise definition of cylindrically symmetry in MO theory?

texts: I was watching an MIT OpenCourseWare lecture on MO theory which mentioned that $\sigma$ orbitals are "cylindrically symmetrical." I was a bit confused, because I was under the assumption that the cross section of a $\sigma$ orbital is an ellipse, such that a $\sigma$ orbital is an ellipse that has undergone a full revolution around an axis. This is somewhat of a topology/nomenclature question, but seeing as the context is Chemistry, I though I'd post here first. Could anyone clear up the definition of cylindrical symmetry?


texts: Niobium has a density of 8.57 g/cm3 and crystallizes with the body-centered cubic unit cell. Calculate the radius of a niobium atom

texts:
Here is my question

  Niobium has a density of $8.57 \pu{g/cm^3}$ and crystallizes with the body-centered cubic unit cell. Calculate the radius of a niobium atom.

Here is my solution


texts: Synthesing tetrahydropyran from ethylene oxide

texts:
I thought that the first step must be using a Grignard reagent to add carbons, but I need a hydroxyl group on the carbon on the other side to make it a diol and produce the product given, but nothing seems to be working.
How do I proceed?


texts: How to reduce propyne selectively for the trans product

texts:
In my textbook it is given that when alkynes react with sodium in liquid ammonia, hydrogenation takes place and a trans isomer is formed.

It is also given (in another part of the chapter) that when terminal alkynes react with sodium in liquid ammonia, they form a salt with sodium.
I assume the first mentioned reaction doesn't take place in the case of terminal alkynes.

Then, how do we, for example, add deuterium to propyne so as to form trans 1,2-dideuteropropene?


texts: Alkylation of 1-naphthol in trifluoroethanol versus in DMSO

texts:
I am supposed to work out which product is formed in which solvent when naphthalen-1-olate is treated with benzyl iodide.

DMSO is a polar aprotic solvent, as it does not possess an acidic hydrogen. So, the negative charge on oxygen will be concentrated as the anion will be poorly solvated. Hence, it should act as a hard nucleophile. Since alkyl halides such as BnI are soft electrophiles, I think that the substituent should preferentially add to the ring.

In 2,2,2-trifluoroethan-1-ol (TFE), I think the reaction would proceed via an SN1 mechanism. Now, the carbocation is a hard electrophile, and thus O-alkylation might be observed.

But considering the better solvation of the negatively charged oxygen in TFE, it would also be more hindered, which suggests that C-alkylation might also be seen.

Which products are actually formed, and am I on the right track?


texts: What information can we gain with the photoluminescence spectra of solids?  The bandgap can be determined for example, but are there any other useful properties we can learn?  I care about this in the context of semiconductors but other answers are also appreciated.


texts: How is combustion speed regulated in solid propellants?

texts:
My question on Space.SE didn't yield anything I didn't know already: the secondary regulation mechanism – grain (cross-section shape) of the propellant, changing the area of open surface of the propellant as it burns away; the combustion occurs only on the surface, travels inwards only as much as the surface burns away, and produces uniform amount of exhaust gasses per unit of area of open surface; the variance in surface area is what changes the overall thrust.

But I'm currently interested in what is done to composition and/or inner structure of the propellant, so that it burns uniformly on the surface, at predictable (and quite slow) pace, instead of, say, exploding all at once, or at least deflagrating at shocking speed, like common explosives (of very similar composition!) do. What property or reaction keeps the combustion to the surface and makes it progress inwards only so slowly – in case of the Space Shuttle, 290 seconds to burn through about 1.5 m of the propellant.


texts: How to distinguish palmitic acid from lauric acid?

texts:
I'm reacting either palmitic acid or lauric acid ($\ce{C16H32O2}$ or $\ce{C12H24O2}$) with $\ce{NaOH}$, sodium hydroxide.

I'm wondering if there's any way to tell which one of those two acids it is after I've already reacted it with NaOH. It has to be a relatively short process, as I won't have much time. I'm doing this for a lab.

In case you feel uncomfortable about what you may call "helping me cheat", please note that my assignment states that I can have online help:

  You may look up information to complete your flow-chart, just be sure to cite your sources...

Note: it doesn't have to be NaOH, it could be any base, I just picked that one. If you think another one would work better, recommend that as well, please.


texts: Is FeS2 both an ionic and covalent compound?

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Iron (II) disulfide.  Iron pyrite.  Fool's gold to some.  But what bond does it fall under?  It could possibly be used for both?

This would give a deeper understanding into other like examples, where it is a fine line between the determination of an ionic compound or a covalent compound.


texts:
In the electrolysis of $\ce{Na2SO4}$, is it valid to write the anode half-reaction (oxidation) as
$$
\ce{OH-} \rightarrow \ce{H+} + \frac{1}{2}\ce{O2} + 2\ce{e-}
$$?

My book says it's
$$
\ce{H2O} \rightarrow 2\ce{H+} + \frac{1}{2}\ce{O2} + 2\ce{e-}.
$$

Other than the additional $\ce{H+}$, there's no difference between the two.


texts: I know as a fact that HCl is a stronger acid than H3O+, but I want to know the reason behind it. The definition of an acid is a substance which dissociates to give H3O+ ions. In that case H3O+ should be the strongest acid available because it does not even need to dissociate it give itself!!


texts: Why is a strong base needed for an E2 reaction and not a an E1 reaction?

texts:
For E2 reactions, why is a strong base like $\ce{NaOH}$ or $\ce{RONa}$ needed? Whereas for E1, even a weak base like $\ce{H2O}$ could be used.

Wikipedia states:

  E2 typically uses a strong base, it needs a chemical strong enough to pull off a weakly acidic hydrogen.

However it does not explain why. The lone pair of the base directly attacks the hydrogen, regardless of E1 or E2.


texts: Why does the boiling and freezing-point of non-polar molecules rise with increasing molecular mass?

texts:
In the section about fuels, my textbook mentions that the boiling and freezing-points of alkanes (which are non-polar) increase with an increase in molecular mass due to London dispersion forces.

Now, I understand what these are and why they become relevant when talking about non-polar molecules, but I can't figure out how they are connected to the boiling and freezing point of the matter. How do these London dispersion forces influence the boiling and freezing point?


texts: Determining molar mass of protein from osmotic pressure

texts:
A 299 mL solution containing 21 g of a protein in toluene had an osmotic pressure of 0.053 atm at 27 degrees Celsius. What is the molar mass (in g/mol) of the protein?

We can use the formula that

$$\Pi = iMRT$$

where $\Pi$ is the osmotic pressure, $i$ the van't Hoff factor, $M$ being the molarity, $R$ being the constant (0.08206), and $T$ being temperature in Kelvin.

Using these values, we can substitute into the equation:
0.053 atm = 1 * M * 0.08206 L atm/(mol * K) * 300.15 K

When we equate this to M, we get
0.00215 = M

Now we know that there is 21 grams of toluene within the 299 mL solution. We can convert the Molarity given by multiplying it by the liters of solution there is. Therefore,
0.299 L * 0.00215 mol/L = 0.000643 mol

Finally, to get molar mass, you simply divide the mass of toluene by the mols given:

21 g / 0.000643 mol = 32639.41 g/mol

This value, however, doesn't seem to be correct, as it is absurdly large. Can anyone help tell me what I'm doing wrong?

-EDIT- I was reading through the question and realized that the answer was correct, I was just thinking about it in a different sense. Thanks to everyone for their help!


texts: Determine the rate equation (intermediate reaction)

texts:
I was helping some students today, quite successfully, until I came across this problem:

$$\begin{align}
\ce{A &<=>[$k_+$][$k_-$] B + C} \\[5pt]
\ce{C + D &->[$k_1$] E}
\end{align}$$

The first equation is a fast process  with forward and reverse rate constants $k_+$ and $k_-$, respectively.
The second process is slow, with rate constant $k_1$.

The objective is to write down a rate law for the resulting equation:

$$\ce{A + D -> B + E}$$

The technique that had been working was to write down the rate for the slow process...

$$r = k_1[\ce{C}][\ce{D}]$$

Since $\ce{C}$ is a product in the fast reaction, which is an equilibrium equation, we also have:

$$k_+[\ce{A}]=k_-[\ce{B}][\ce{C}]$$

This is where things went awry, because the rate law that we seek is a function of $[\ce{A}]$ and $[\ce{D}]$ only. Considering the stoichiometry, it seemed appropriate to put $[\ce{B}]=[\ce{C}]$. This leads to the substitution $[\ce{C}]=(\frac{k_+}{k_-})^{1/2}[\ce{A}]^{1/2}$. The interface has declared the result to be invalid, so it must be an illegal maneuver. How, then, do I eliminate $[\ce{B}]$ and $[\ce{C}]$ and come up with the desired reaction rate law?


texts: Direction of external cell when voltage is supplied by it to Daniel cell to oppose cell potential

texts:
The above diagram is from our textbook for a Daniel cell.

This is a diagram from our textbook showing a Daniel cell when an external voltage opposing the cell potential is a applied. Here ${E}_{ext}$ is less than cell potential.

This diagram show the Daniel cell when ${E}_{ext}$ is greater than cell potential. What I do not understand is why has the direction of the cell been reversed in the last diagram?
Is this an error? If it is not an error, then why are the $\ce{Cu^2+}$ ions in the solution NOT accepting the electrons provided by the cell and getting reduced? Why is the Copper electrode acting as an anode?


texts: How to calculate mass produced when a given gas is burned?

texts:
The equation below represents combustion of methane ($\ce{CH4}$, $\pu{16.04 g/mol}$). Balance the equation, and calculate the mass of water ($\pu{18.02 g/mol}$) formed when $\pu{40.0g}$ of methane is burned.
  $$\ce{CH4(g) + O2(g) -> CO2 + H2O(g)}$$

I have started the problem by balancing:

$$\ce{1CH4(g) + 2O2(g) -> 1CO2 + 2H2O}$$

I then continued by calculating the amount of substance of methane:

$$\ce{C ($\pu{12g/mol}$) + H ($\pu{4 \times 1g/mol}$) = $\pu{16 g/mol}$ \implies ($\pu{40 g}$ methane) / ($\pu{16 g/mol}$) = $\pu{2.5 mol}$}$$

From here I wold like to know how to convert or get to amount of substance of $\ce{H2O}$ to get the mass of $\ce{H2O}$ produced in this reaction.


texts: Understanding Joule-Thomson expansion apparatus

texts:
I am reading the Joule-Thomson experiment and although I can follow the mathematics I can't understand what is going on. Here is the apparatus

taken from Atkins. So initial the gas is at $P_i$ and because of the opening and the difference in pressure it will eventually reach the right compartment with $P_f$. What I can't understand is what the role of porous plug and how this setup differs from an adiabatic expansion. I mean couldn't we let the the gas expand from $P_i$ to $P_f$ and then record the difference in temperature? Also what is the role of porous plug in this setup if the system doesn't exchange heat and the work is done on the environment in right and left compartment respectively.


texts:
I optimized a geometry of $\ce{Ni(H2O)6}$ using quantum chemistry and got a molecule which is symmetrical for the $\ce{Ni-O}$ distances as shown
here:

In the literature it says that this complex has an $\ce{O_h}$ point group, but this complex looks like it is $\ce{T_h}$. Do I need to revise my group theory or is what I am looking at actually a $\ce{T_h}$ point group?


texts: What is the origin of the names P-1 and P-2 of nickel boride catalysts?

texts:
From Chapter 2 of Catalytic Hydrogenation in Organic Syntheses:

  Highly stereospecific hydrogenations of acetylenes to cis-olefins can be achieved with a nickel (P2) catalyst, prepared by sodium borohydride reduction of nickel acetate in ethanol, and ethylenediamine as a promoter.

The Wikipedia article on nickel boride describes two forms, P-1 and P-2, differing in their ratio of $\ce{Ni2B}$ to $\ce{NaBO2}$.

What is the origin of the names "P1" and "P2"? Does it have to do with whether the catalysts add hydrogen in a syn or anti fashion?


texts: What type of reactions are used in this synthesis?

texts:
The compound $\ce{(CH3)2CHCH2NH2}$ can be synthesised by the following route.
$$\ce{CH3CH=CH2 ->[1] CH3CHBrCH3 ->[2] (CH3)2CHCN ->[3] (CH3)2CHCH2NH2}$$
What types of reaction are used in stages 1, 2 and 3?

A 1=substitution; 2=addition; 3=reduction

B 1=substitution; 2=addition; 3=hydrolysis

C 1=addition; 2=substitution; 3=reduction

D 1=addition; 2=addition; 3=reduction

E 1=addition; 2=substitution; 3=hydrolysis

Could someone please explain to me how they worked out what reactions were used in the stages? I have been able to figure out stage 1 and 2, but I am really stuck on stage 3, I think it should be addition but this isn't one of the answers.


texts: Current reversal in galvanic cell according to Nernst equation

texts:
In a galvanic cell with zinc, zinc sulphate solution and copper, copper sulphate solution, if at equilibrium concentration of zinc sulphate solution increased/copper sulphate solution decreased, will current flow in the opposite direction (from copper rod to zinc rod)?
(The value of cell potential according to Nernst equation will be negative in this case, and to re-establish equilibrium, current should flow from copper rod to zinc rod. )


texts: Green colour resulting from the formation of pi complex

texts:
Peter Sykes mentions in Guidebook to Mechanism in Organic Chemistry (6th ed.) on p.132 that there would significant differences in physical properties of the resultant mixture when we:

React methylbenzene with $\ce {HCl}$ to form a $\sigma$ complex
React methylbenzene with $\ce {HCl}$, with $\ce {AlCl3}$ as Lewis acid catalyst, to form a $\pi$ complex

One of the differences he mentioned was that the former would remain colourless while the latter would give a green colour. However, he did not make clear what gives rise to the colour difference. Is it due to formation of the $\pi$ complex?


texts:
When you fill up a balloon about a quarter way with liquefied butane fuel and let it sit at room temperature it will turn into gas. But why does the gas weigh the same as the liquified butane?
The liquefied butane liquid weighs just about as much as water.


texts: Are certain logP values eluted when 100% methanol is used as the solvent in a C18 column?

texts:
I have used a C18 sep-pak to concentrate metabolites in a chemically complex solution. The column was first washed with pure water, 75% methanol:water mix, and finally the compounds eluted with 100% methanol.

What I am wondering is what chemical properties that I can infer from this information? I know I would have washed the very polar compounds away, and in pure methanol, I would expect compounds of a semi-polar nature to be eluted. Can I assume that these compounds would have a specific LogP range? I cannot find an answer online anywhere, so I guess the answer must be no, and if so, why not?

There is one (or more) compound of a biologically active nature in this complex mix. I am wondering if I can use the elution conditions to understand some of the chemical properties of the compounds eluted. Further, I did FT-ICR-MS on this mix, and I would like to look at a list of compound hits from the mass spec databases and understand how feasible a particular hit is based on its polarity.


texts:
I know atoms are held together by Ionic and Covalent bonds and i understand the ionically bonded atoms are held together by electrostatic forces. What about covalent bonds?
How are molecules of bonded atoms held together?Are ionic compounds just aggregates of oppositely charged ions and hence don't have any definitive "molecules". What about molecules of covalently bonded atoms?


texts: What is it that makes this noncontact catalytic system unique in 2020?

texts:
Phys.org's Accelerating chemical reactions without direct contact with a catalyst discusses the new Science Advances paper Noncontact catalysis: Initiation of selective ethylbenzene oxidation by Au cluster-facilitated cyclooctene epoxidation. I expected to read about something really unusual, long range forces, virtual entangled photons...
But Figure 1 of the paper (shown below) helps to explain that the catalyst produces an intermediary species and it's this that initiates or catalyzes the desired effect.
Question: Is it possible to make clear to a non-chemist how new the published noncontact catalytic system reaction really is? What is it that makes this unique or novel in 2020? Did nobody think of this until now, or have people been trying for a long time but this is the first success?

Fig. 1 A noncontact catalytic system.
A catalyst (Cat) catalyzes reaction A (AR ➔ S ➔AP) in which the intermediate S is effective in either initiating or catalyzing reaction B (BR ➔ BP), although reaction B is not catalyzed by the catalyst.


texts:
I have been given the task of designing a new wheel rim (the metal part of the wheel) but instead of metal, it has to be made out of a polymer.

I'm thinking of using either PVC or PET but I don't know if either of those plastics will be able to support the weight of a car and am not sure how to find that out.

If anyone can think of a different polymer that I could use instead that would be better suited feel free to include it as an answer. This is only theoretical so cost/difficulty to manufacture is not a big hassle.


texts: Gibbs free energy calculation for redox reaction

texts:
I was wondering if it is correct to calculate the Gibbs free energy of reaction at $P = \pu{1 atm}$ and $T = \pu{1100 K}$ using the NIST-JANAF thermochemical tables. For example, for the reaction of ammonia and nitrous oxide:

$$\ce{NH3(g) + 1.5 N2O(g) -> 2 N2(g) + 1.5 H2O(g)}$$

Can I later use this result to calculate the electric potential knowing the amount of electrons transferred?

I'm no electrochemist, I'm just trying to estimate the open circuit voltage for a fuel cell.


texts:
Why do we say that an alpha hydrogen is necessary for hyperconjugation? What exactly is an alpha hydrogen? From what I read online, it is the hydrogen attached to a functional group. Why is that required?

For example, in $\ce{CH3-CH=CH2}$, hyperconjugation takes place, but I don't see clearly any functional group that would facilitate it.

Alternatively, in $\ce{CH3-COOH}$ it does not take place.

Why is this?


texts: Aluminum Battery with PAC setup : Rapid voltage drop problem after a charge

texts:
I am a retired man and seek for activity. I dont have background in chemistry but I want to learn an aluminum battery..the known problem is my aluminum metal get eaten and also corrosion even if using sodium electrolite and worse if using Aluminum chloride.
So I just try PAC for water treatment and it look like the reduction is minimum. But as usual the usual voltage drop always problem in any set up of galvanic.
What happen and how to prevent that? my experiment setup is a square aluminum that act as a case also as cathode. Fill with carbon powder separated by paper. in the center is a graphyte rod pour with PAC in water...this gives a 2,5V
please review what kind of chemical formula during equilibrium and during recharge? why voltage is droping or how to make this setup more better and stable as battery?


texts: Qualitative Analysis for Chemistry Project

texts:
I am making a chemistry project wherein I wish to analyze the contents of purified and unpurified water, mainly the salts contained in them.

What I wish to know is: What is the best way to do this? How do I start? Should I separate all the salts first?


texts:
Which alcohol will most easily react with HCl to form an alkyl halide?

A. Primary alcohol

B. Secondary alcohol

C. Tertiary alcohol

D. All alcohols react equally to form alkyl halides


texts: Separating boric acid from sodium chloride

texts:
I want to create some boric acid with borax in the following reaction:

$$\ce{Na2B4O7·10H2O + 2 HCl → 4 BH3O3 + 2 NaCl + 5 H2O}$$

However as you can see, the leftover solution will contain a mixture of boric acid, sodium chloride and water. Both chemicals are soluble in cold water so neither will want to immediately crash out of solution.

My question is, how can I remove the excess water and sodium chloride to leave myself with some powdered/dry boric acid crystals?

I know I can probably just use some liquid ammonia, but then the boric acid is only slightly soluble in it leaving much of it behind. I could perhaps use glycerin also, however I am limited to how much I currently have.


texts:
Which form of the cyanamide ion is more stable?

As per the resonance rules, I find both of them equally stable as number of bonds is the same, more electronegative atom has negative charge and so on. Is my conclusion right?


texts:
I have been reading an introductory book on fuel cells, and it's indicated that SOFC need to be brought to $\pu{600\! -\! 1000 ^\circ C}$ to be more efficient.
So, my understanding is that if I want to have a working fuel cell, I would need to come up with a system that could "heat up" my fuel cell to $\pu{750 ^\circ C}$?
Most of the articles I have been reading explain how fuels cells work, but what would be the actual set-up? I would have to put the fuel cell in some sort of oven?
Thanks for your input!


texts: The products of the reduction of esters with $\ce {LiAlH4}$ and the products of the reduction of amides with $\ce {LiAlH4}$ are vastly different. The former reduction cleaves the ester and produces two alcohols while the latter reduction produces an amine with the carbonyl group of the original amide replaced with $\ce {CH2}$. A carbamate seems to display both chemical behaviour of esters and amides. I am curious to know what would be the mechanism by which reduction of carbamate with $\ce {LiAlH4}$ takes place and what would be the products of such a reduction.


texts: Through bond interaction in biradical dioxo compound and its correlation diagram

texts:
I'd like to investigate into the ring opening, the migratory reverse reaction of the electrocyclic ring-closure of Dimethyldioxirane:

As a first question I'd like to ask if I have drawn the through bond interaction correctly?

Following scheme is wrong, because the p orbitals are perpendicular to the O-C-O as @ron clearly pointed out in his answer in Are the p orbitals of the biradical dioxo compound in the HOMO perpendicular to the plane?

Next I tried to draw the orbital correlation diagram.
I guess for this correlation diagram I don't have to draw the through bond interaction, yes?

In the dioxo biradical product I've drawn a smaller energy gap between $\pi$ and $\pi^*$ orbitals as for $\sigma$ and $\sigma^*$. I guess this should be correct.
Because there is an additional through bond interaction for the product I've drawn a small exothermicity. I see no activation energy for the disrotatory ring opening. So the disrotatory ring opening must happens very fast (without a lot of thermal energy, may be even at room temperature).

Finally, I tried to draw the state correlation diagram:

For the photochemical reaction there is a transition from $S_0$ to $S_2$. Because of the avoided crossings the conrotatory correlation is steeper falling down, therefore I expect most of the electrons direcetly going in the pericyclic minimum and do there Interal Conversion to the $S_1$ surface and afterwards the excited product gives off a photon going back to the $S_0$ state. I expect products in excited states are not very long living and therefore undergoes emission of a photon as Internal Conversion under fluorescence here.
Another way out from the pericyclic minimum can be the directly falling to the transition state of the $S_0$ state and giving the product to a good quantum yield.
As third option some part of the $S_2$ states can go through the disrotatory pathway and directly emitting light from $S_2$ to $S_0$. As written in the first point I think this way is less probable because of the less steeper falling down the energy surface.

Is this all correct?


texts: Using electronegativity and atomic size to compare acidity of cysteine with serine

texts:
In proteins, the alcohol group of serine is generally more difficult to deprotonate than the thiol group of cysteine.

Serine and cysteine respectively:

In the literature, the explanation given is that the sulfur atom is larger than the oxygen atom, and therefore the resultant negative charge is stabilised over a larger surface.

But I am confused. Oxygen is a more electronegative atom than sulfur and therefore can more stably carry a negative charge. How are these two assertions compatible?

oxygen can carry negative charge more easily because it is more electronegative, and
sulfur can carry negative charge more easily because it is larger?

Clearly, they cannot both be true and in the case of these two amino acids, the size of the sulfur prevails over the electronegativity of the oxygen. Why is that? Why in some circumstances is it the other way around?


texts: Reference to find dielectric constants and dielectric relaxation time

texts:
I am working on a Master degree and need to know the following data :

The static (low frequency) dielectric constant of isopropanol at 25 °C
The Optical (high frequency) dielectric constant of isopropanol at 25 °C
Dielectric relaxation time (τ) of isopropanol at 25 °C

Could someone please provide me with these values and a reference or link to a book contains these data?


texts: Do Cyclohexane-1,3-diones Give Positive Haloform Reactions?

texts:
Recently a post appeared on ChemSE asking why cyclohexane-1,3-dione (dihydroresorcinol) 1a doesn’t give a positive iodoform test. Unfortunately, the post was subsequently taken down after several comments. A paper by Fuson and Bull[1] reviewed the haloform reaction and stated that the iodoform test was negative for 1a. However, dihydroresorcinol undergoes the bromoform reaction[2] to yield both glutaric acid 9a and bromoform 7 as does 5,5-dimethylcyclohexane-1,3-dione (dimedone)[3] 1b yield β,β-dimethyl glutaric acid 9b and bromoform. Moreover, dimedone 1b affords the same diacid 9b and chloroform when sodium hypochlorite is employed.[4]
Mechanistically, dibromination of 1,3-diones 1 affords dibromides 2, non-enolic β-diketones. In alkaline medium diketones 2 cleave to provide dibromides 4 via intermediate 3. Further bromination of dibromides 4 sets the stage for the bromoform reaction on 5 leading to bromoform 7 and the glutaric acids 9.

These reactions were found by searching Chem. Absts. but there was no sign of the iodoform reaction on these two diketones. So, the question is, why no iodoform reaction?
a) It is unimaginable that the reaction has never been conducted.
b) Perhaps more vigorous conditions are required.
c) The diiodo analog of dihalo diketone 2, if ever formed, may be formed reversibly by iodide or hydroxide reduction. Even so, the equilibrium should be shifted to the right.
d) If the diiodide is slow to fragment, might it undergo a Favorskii ring contraction instead?
Any insights are appreciated.

R. C. Fuson and B. A. Bull, Chem. Rev., 1934, 15(3), 275-309. DOI: 10.1021/cr60052a001. PDF link
D. Vorlander and M. Kohlmann, Chem. Ber., 1899, 32, 1878.
G. Komppa, Chem. Ber., 1899, 32, 1423.
W. S. Johnson and D. D. Cameron, Org. Syn., 1951, 31, 40. DOI:10.15227/orgsyn.031.0040


texts: Effect of temperature in the free radical polymerization of acrylic acid

texts:
I am working with the model of a free radical polymerization process in a tubular reactor. In the simulations, I observe that by keeping the feed flow of the initiator (sodium persulfate) and the monomer (acrylic acid) constant and just by increasing the jacket temperature, the concentration of the monomer (for example of the product) increases, even though the reaction is exothermic.
I have used the method of moments to model the chain length distribution of polymers. Change of viscosity has not been modeled.

My question is: Is the increase in the monmoer concentration by the increase of temperature, an expected behavior in polymerization? If so, do you know some literature that I can learn more about this?


texts: How to determine the van't Hoff factor for different salts in water experimentally?

texts:
How do I experimentally determine the van't Hoff factor for different salts in water?

I'm going to dissolve each of sodium chloride, potassium chloride, and lithium chloride in $\pu{20 mL}$ of water to form $0.1$ molality standard solutions. I want to determine the actual van't Hoff factor for these ionic compounds. Theoretically, it is 2, but how do I find the actual value? I know that the formula for van't Hoff is actual number of ions/theoretical number of ions, but I don't know how to find the actual number of ions. Can someone please help?
PS: My experiment is about ionic association. I am trying to see, how it affects van't Hoff and therefore freezing point depression. I was initially going to find the depression and then use the formula to find van't Hoff, but this is too tedious.


texts: Product of Friedel-Crafts cyclisation of (3-methylpent-4-en-1-yl)benzene

texts:
My proposed mechanism and final product is:

But the book says the answer is:

I know that a 6 membered ring is more stable than a 5 membered ring so I made the product with the 6 membered ring (however, the carbocation was a secondary carbocation).

However, the book claims the answer to be the one with the 5 membered ring (the carbocation here was a tertiary carbocation).

Is the answer provided in the book wrong?


texts: Is there a common name to refer to the groups 13 and 14?

texts: The group 15, 16, and 17 are called the pnictogens, chalcogens, and halogens respectively. Is there a name for the groups 13 and 14 as well?


texts: Do we prefer the substituent or the longest chain in IUPAC nomenclature?

texts:
I've seen too many related questions already, but mine is a simple and slightly different query

Take this compound as an example:

The name written below it is generated by ChemSketch. I agree with this generated name, because according to me, "bromo" is not a functional group, but rather a substituent only. Hence, it is not necessary to include it in the parent chain. Thus, the above name has preferred the longest chain (length) over substituent inclusion.

However, my book gives the answer as 1-bromo-2-ethyl-2-methylbutane, preferring substituent inclusion over longest chain (length).

My query thus is:

  In any hydrocarbon where the substituent does not lie on the longest chain, do we prefer the longer chain, or sacrifice it for the inclusion of the substituent?


texts: What is the significance of Sphingolipids in human?

texts:
I want to know the significance of sphingolipids in human. I have learnt that sphingomyelin is the most significant type of sphingolipid in human. Also that the sphingomyelin serves as a structural constituent of myelin sheath of nerve fibres.

Is that all? I need to clarify this. Please help me. Thank you


texts:
I had total blackout with these ideal gas equations as I haven't needed these in years. If I have two gasses, A and B which both have same volume V and quantity N. We also have temperatures T1 and T2.

Now, I let energy change between these two ideal gases. How do I get the final temperature out using these informations?

I realise we take the ideal gas equation $p = \frac{NRT_1}{V}$ and get the answer from there, right?


texts: In a mass spectrum, are there peaks corresponding to a combination of 13C and bromine isotopes?

texts:
I just began studying mass spectroscopy and I don't understand why certain peaks are not represented in the mass spectrum graph. Like let's say you have methyl or ethyl bromide. Usually, there are two equal molecular ion peaks at the right-most side, which indicate a $1:1$ ratio of $\ce{^{79}Br}$ and $\ce{^{81}Br}$ isotopes.

But this is only when you assume all carbon atom are $\ce{^{12}C}$. Why doesn't the graph show peaks with combination of $\ce{^{13}C}$ and bromine isotopes?

None of the examples online indicate this.


texts: how to determine the relative differences in activity between metals

texts: I am doing a lab for school and I do not know what this question is asking. In this lab we are making electrochemical cells from different metals.


texts: What is the physical basis for Hund's first rule?

texts:
According to Hund's first rule, a set of degenerate orbitals are singly occupied first, before the second slot in any of the orbitals are populated. This is quite intuitive because electron-electron repulsions would make an atom more unstable if the electrons start filling two at a time in a single orbital.

However, the rule also states that in the ground state, electrons that singly fill the orbitals will adopt the same spin. Why is it necessary for the electrons to have the same spin?


texts: How do I calculate the proportion of respective conjugates of one base mixed with several acids (and/or conversely) at different temperatures?

texts: How do I calculate the proportion of respective conjugates of one base mixed with several acids (and/or conversely) at different temperatures, and is there a free software tool that would allow me to interact with the computations therefor (e.g. search the temperature or portion that maximises one conjugate over another)?


texts: Can every conductor be electroplated using copper and sulphuric acid?

texts:
I really like electrolysis. Today I bought 30% sulphuric acid to electroplate something with pieces of copper.

I've poured half water and half acid in a glass. I connected some cuprextit-copper plate to the anode and outdated aluminium coin to the cathode.

After starting the process, I could see that nothing is appearing on the cathode. I scratched the aluminium of the oxides. After repeating the electrolysis, aluminium turned black wherever scratched. Then I found out I swapped the wires.

So, once I had the wires correct, this happened to my cathode:

The dust can be easily washed off.

According to the image from wikipedia, any metal should be "electroplateable". I actually thought that any conductor that doesn't react with the solution can be electroplated.

So what's the reality? Was I just impatient? Is electroplating only limited to some conductors? What about non metal ones? Can I electroplate carbon electrode?


texts: Finding chair and boat transition states during ring-forming reactions

texts:
Reactions that form 6 membered rings most commonly go via either boat or chair transition states but the products themselves do not necessarily adopt the same conformation as the TS.

I'm attempting to model a cyclisation in which an amine attacks a pi system to form a new ring, giving rise to two diasteromers depending on which face of the pi system is attacked.

The products have been explored (MM conformational search then QM optimisation of all low energy conformers) and are both chairs (the boat being significantly high in energy as to be essentially unpopulated).

In the reaction of interest there is precedence in the literature from computational studies that the reactions can go via either boats or chairs (depending on the exact structure) and so I would ideally like to find both possible transition states leading to each diastereomer.

My initial plan was to start with the product and work backwards (the transition state is thought to be late, meaning it should resemble the product) , elongating the bond by x angstroms (optimising at each step whilst constraining the distance) and then looking for a 'maximum' from which I would then optimise to a TS however this doesn't provide  a method for me to find the boat TS's.

How does one go about finding all possible transition states? Is it valid for me to find a high energy boat conformation of the product and apply the same bond lengthening exercise?


texts: Adding more solid to a solid/gas equilibrium

texts:
$$\ce{CaCO3(s)<=> CO2(g) + CaO(s)}$$

In this equation, what happens if you increase the amount of one of the solids while there are existing quantities of everything else?

According to the calculation for the equilibrium constant, equilibrium is only dependent on the concentration of $\ce{CO2}$, so it technically should not change anything, right? However, if you decrease the pressure of the $\ce{CO2}$ enough, then shouldn't there be a point where the equilibrium constant can no longer be met because there aren't enough moles of $\ce{CO2}$?

Additionally, at this point, shouldn't adding more $\ce{CaCO3}$ change the point of equilibrium?


texts: Why is the melting of ice a spontaneous reaction?

texts: So here's my question: we know that melting of ice is an spontaneous reaction but is it spontaneous? We have to supply energy in the form heat for the reaction to take place.


texts: What is the proof for saying all the compounds-of-an-element (except few), to have the same oxidation number?

texts:
Following statements are extracted from Puri, Sharma, and Kalia's Principles Of Inorganic Chemistry book:

In all hydrogen compounds (except hydrides of active metals), the oxidation number of hydrogen per atom is +1.
In all oxygen compounds (except hydrogen peroxide and other peroxides and superoxides), the oxidation number of oxygen per atom is -2.

Have Chemists tested the oxidation state of every compound (of hydrogen, Oxygen or any element considered to have fixed oxidation sate) in the universe, to say all the compounds (with few mentioned exceptions) of the considered element to have the fixed oxidation state?
Is there any proof or law for supporting above statements? Or is the author sloppy in not saying "In all the known hydrogen/oxygen compounds"?


texts: Comparing the mesomeric effects of amino and mercapto groups

texts:
I was quite surprised to find that $\ce{NH2}$ has much more $+M$ effect than $\ce{SH}$. But shouldn't we also consider the fact that $\ce{SH}$ has 2 lone pairs? Or is the greater electron density of nitrogen playing some role here?

How can I rationalise the stronger mesomeric effect of nitrogen?


texts: Why is the standard enthalpy of formation of black phosphorus not zero?

texts: Black phosphorus is the most stable allotrope of phosphorus. Then why is its standard enthalpy of formation not taken as zero?


texts:
In $\ce{CH3CH2-}$  what should be direction of inductive effect?

If going by order mentioned in my book, it is to be from carbon containing negative charge to CH3, but is not the carbon containing the negative charge more electronegative? So should not the direction be towards it?


texts: Assignment of the 13C NMR of 2-heptanone

texts:
The 13C NMR of 2-heptanone is given below:

I understand the assignments of the carbons labelled 7, 6, 4 and 1.

My question is: Why is the shift of environment 5 higher than that of 3, despite being further away from the electron withdrawing carbonyl group?


texts: As far as I know, glass is a non-crystalline amorphous solid. Does glass exist in crystalline forms? Or is it the definition of glass that it's non-crystalline, in which case my question is based off of a false assumption?


texts: Does boiling water alter the chemical properties of dishwashing liquid?

texts: An ex-housemate of mine claimed to be a former chemist, and once told me not to use boiling water (or recently boiled water) when leaving dishes to soak, as the temperature would chemically alter the dishwashing liquid, rendering it useless or at least significantly less effective. However I've never found anything in internet searches to support this assertion. Can you lovely peeps help give me a definitive answer?


texts: Finding the volume needed to make a new pH

texts:
In the titration of 20.00 mL of 0.500 M HCl by 0.500 M NaOH, calculate the volume of 0.500 M NaOH required to reach a pH of 2.0.

I have tried to change the 20.00 mL into the amount of substance (0.01 moles), then I turned the 2.0 pH into concentration (0.01 M). I then tried to find the total volume, which came out to be 1 L, which creates 980 mL of NaOH. Plugging it back in though doesn't give 2.0 pH. So, I was wondering if anyone knew how to find the volume, or if there was a formula that I could use to solve it.


texts: Calculating the mass of water removed by air conditioning condensation

texts:
I cannot figure out how to calculate the mass.

The question is:

  "Suppose the percent relative humidity is $\mathrm{80.0\%}$ at $\mathrm{91.4\ ^\circ F}$ ($\mathrm{33.0\ ^\circ C}$) in a house with a volume $\mathrm{245\ m^3}$. Then the air conditioner is turned on. Due to the condensation of of water vapor on the cold coils of the air conditioner, water vapor is also removed from the air as it cools. After the temperature has reached $\mathrm{77\ ^\circ F}$ ($\mathrm{25\ ^\circ C}$), the percent relative humidity is measured to be $\mathrm{15.0\ \%}$. What mass of water vapor has been removed from the house? (Reminder: take into account the difference in saturated water vapor pressure at two temperatures.)"

The answer is $6.00\ \mathrm{kg}$.

Relative humidity= (actual pressure of $\ce{H2O}$ pressure/partial pressure of $\ce{H2O}$ if saturated) * 100

So, my first step was to find the actual pressure of the initial and final conditions.

$X/355.1 = 0.80$

$X = 284.08~\mathrm{Torr}$

Then $X/23.76 = 0.15$

$X= 3.564$

$\mathrm{284.08~Torr- 3.564~Torr = 280.516~Torr}$ (water removed, I think)

I attempted to use the ideal gas formula ($pV= nRT$) but kept getting the wrong answer. How do I approach the rest of the problem?


texts: How do oxide formations affect voltaic cells?

texts:
I asked a question previously on here but still have some confusion. To briefly summarize, I made a voltaic cell for a school project with 0.1 M copper nitrate and varying concentrations of aluminum, zinc and nickel nitrates. My results were fairly consistent with the theoretical values from the Nernst equation for zinc, however, the aluminum and nickel cells produced substantially less voltage than their theoretical values. The answer I got from my previous question explained how the low voltage in the aluminum cell was a result of its oxide layer.
However, I still had some confusion over why there were differences between aluminum and nickel, and zinc. Firstly, it's my understanding that a metal's ability to form an oxide layer is related to its reactivity. This would explain aluminum's tendency to form such a strong oxide layer however, zinc has a higher reactivity than nickel so wouldn't it also form an oxide layer and its outputted voltage would be lowered similarly.
My next explanation for the differences between aluminum and nickel, and zinc was related to the ability of the oxides to either react or dissolve in the nitrate solutions, however, I found that nickel oxide is soluble in acids and aluminum oxide reacts with acids.
I was also wondering how I even got a voltage in the aluminum cell if the oxide layer does not allow any aluminum ions to be transferred.
I would appreciate some guidance from the chemistry wizards because at this point I am stumped.


texts:
I'm talking about this video, from where I'm referencing.

My problem is with stage 3. From what I understand, we need $\ce{H2SO4}$ for mixing it with sulfur trioxide to produce oleum. From oleum later by adding water, we derive brand new sulfuric acid again.

So without sulfuric acid, we can't carry out the contact process, am I right?

Also, now which of the two reaction is exothermic i.e. which reaction should the chemicals should be carefully dropped in small drops?

$$
\begin{align}
\ce{SO3 + H2SO4 &-> H2S2O7}\tag{1}\\
\ce{SO3 + H2O &-> H2SO4}\tag{2}
\end{align}
$$


texts:
The advice for cleaning salt stains (for example from shoes) with a vinegar + water solution is fairly ubiquitous on the internet. Is there a chemical explanation for why the vinegar is important? Why not just water?

Edit: I don't actually know that vinegar helps clean salt stains. There might be actually be no chemical reason for the advice to be valid.


texts: I heard somewhere (I think is was a show called "How The Universe Works") that the big bang was the result of a hydrogen atom and a helium atom. Is this true? If so, where did all the other elements come from?


texts:
Consider:

I found these rearrangements, but I could not understand what the mechanism is behind this.

When I searched on the Internet I found the Wikipedia page Di-pi-methane rearrangement.


texts: Does firing a proton beam on water make it acidic?

texts:
Lets say I fire a proton beam upon the surface of water. Lets assume I do the experiment in an air-free environment and that the proton beam doesn't reflect off the surface of water.

Now, protons, which are simply $\ce{H+}$, should enter the bulk of water and probably combine with a $\ce{H2O}$ molecule and form $\ce{H3O+}$. As per the definition of acidity and pH:

$$\ce{pH}=-\log [H^+]$$

If the pH reduces, the solution would become acidic as seen here. But at the same time, the water becomes charged, so I am not sure whether this is applicable.

So, in short, does water become acidic due to a proton beam?

Edit: I do not have access to proton guns and it's certainly not on sale on eBay. I only attempt to theorize on what may happen.


texts: Effect on mass when decreasing pressure in equilibrium reaction

texts:
For example, if we have the reaction:
$$\ce{A + B <=> C}$$
And the volume is decreased, the pressure would increase. Hence, according to Le chatelier's principle, the system will partially oppose the change by favoring the forward reaction to produce more $\ce{C}$. I have a few questions:

Would the mass of $\ce{C}$ increase?

I think yes, since the forward reaction is favored

Would the concentration of $\ce{[A]}$ be greater when compared to the original concentration of $\ce{[A]}$?

I think yes, since the volume is decreased.

Would the amount of $\ce{A}$ be reduced?

I think yes, since it's being consumed for the forward reaction.


texts: What does a molecules color have to do with its bond/orbital energies?

texts:
For example, elemental iodine is deep violet. Its sigma bond or perhaps the lone pairs are capable of absorbing all visible light frequencies except violet which is why we see it as that color.
Lithium, on the other hand, is red which means its valence electrons must be reflecting red frequencies.
So, does that mean the valence/bonding electrons of $\ce{I2}$ are higher energy than the lithium valence electrons?
In other words, is there a relationship between an orbitals energy and the type of light it can reflect?

You could perhaps compare $\ce{I2, Sn^{II}I2}$, and $\ce{Sn^{IV}I4}$, and which are violet, yellow, orange (in decreasing order of visible light energy).

Perhaps it has to do with symmetry? $\ce{I2}$ is $D_{\infty\mathrm{h}}$, stannous iodide is $C_{2\mathrm{v}}$, and stannic iodide is $T_\mathrm{d}$.


texts:
The test for anions can be done with a platinum wire and a Bunsen flame.
My textbook says that it can also be done by preparing a solution of the given salt in water and ethanol and spraying it onto the Bunsen flame.
How do I prepare this solution in terms of how much water, ethanol and salt ?


texts: Synthesis of Pt(II) complex using trans effect

texts:
By making use of the trans-effect in platinum(II) complexes, show efficient routes for the synthesis of all the possible isomers of $\ce{[PtCl(NH3)2(py)]+}$ (where $\ce{py}$ = pyridine) from the starting material $\ce{K2PtCl4}$.

So far, I've had problems with trying to substitute ammonia and py in the right places. Since $\ce{Cl-}$ is higher on the trans effect list than the two ligands I want to substitute with, I found that it's just not possible to do that.


texts: name of a pharmaceutical drug used in dentistry that has Ionic bonding? and how this bounding is made?

texts:
Hello I am looking for this information and I did not find anything, the closest thing I have found it is Fluorocarbon, but I think it is wrong, does anybody know?.
Help really appreciated I am still looking for this


texts: How can I predict the product of the reaction of 2-methyltetrahydrofuran with HI?

texts: I am supposed to explain why treatment of 2-methyltetrahydrofuran with hydrogen iodide leads to the formation of 5-iodopentan-2-ol. However, I am getting stuck as it seems that the less stable primary carbocation is being preferentially formed, leading to the product. Is my mechanism incorrect?


texts: Wood burning and carbon dioxide or monoxide?

texts: I am building greenhouse and i want to operate greenhouse at winter time. For heating i ll use wood. And also i am thinking to give back  carbon monoxide which ll come from burning process of wood. There is a question, how can avoid to get carbon monoxide from burning wood, do i must give more air flow (or oxygen flow) to burning process? Or when you burn wood there is just one gas output that is carbon dioxide?


texts:
Why the concentration of a solution expressed in gram equivalent weights of solute per litre of solution is termed as "normality" ?

Does it have anything to do with the word "normal" ?


texts: Cat litter crystals causing toxic smell upon rubbing and pouring out of the package, safe?

texts:
I am under-educated in terms of chemistry hence the question and assumptions.

Basically, for our cats, we are using what seems to be the latest scientific achievement in litter sand - the litter crystals. Might be about 2 years now, since we switched from clumping sand to crystals.

As of late, I have started to pick up a somewhat toxic, disturbing smell, that feels to me as if those could be dust particles or something. Now, since I read that the litter contains something of silica family:

  Most cat litter crystals are composed of silica gel which is a combination of water, oxygen, and silica dioxide sand.

And also that the silica dust is somewhat toxic - this kind of matches, though, I may just be getting paranoid.

But yeah, when the cat rubs the litterbox after he has done his business, the smell picks up and it's heavily noticeable, really unpleasant for my and wifes nose.

Obviously, when the packages are being transported - the crystals rub/grind against each other, making them crumble and when I pour the crystals out - the crumbled parts get up in the air making the smell again.

Yeah, I'm starting to become a little concerned about the possible health hazards that the crystals could cause, therefore I'm looking for some clarification from you guys.

Are these things safe?


texts: Reduction of ester / eneone in presence of epoxide

texts:
I want to reduce an ester and an eneone in the presence of a terminal epoxide.

I read on here @jerepierre did an ester in the presence of an epoxide with DIBAL.

I know the DIBAL works for my ester, but am not sure if it will also open the epoxide; reports are conflicting.

Any advice on reagents or conditions to consider or references to read are greatly appreciated!


texts: How to calculate the equilibrium constant from the density of a nitrogen dioxide and dinitrogen tetroxide mixture?

texts:
The density of an equilibrium mixture of $\ce{N2O4}$ and $\ce{NO2}$ at $\pu{1 atm}$ and $\pu{373.5 K}$ is $\pu{2.0 g/L}$. Calculate $K_c$ for the dissociation reaction

I did this:

Let initial amount of substance be $a$.
Initial vapor density $=(\text{mass of }\ce{N2O4})/2 =46$
For final vapour density I find effective molecular mass of the mixture $\ce{N2O4}$ + $\ce{NO2}$ at equilibrium using ideal gas equation which comes out to be $61.33$ and thus final vapor density is $61.33/2=30.665$.
Now supposing degree of dissociation to be $x$ , total amount of substance at equilibrium is $a\times(1+x)$.
As $\text{Vapor density} \times \text{total amount of substance} = \text{constant}$ at same temperature, $46\times a=30.665\times a\times(1+x)$
$x=0.5$ Using this in the equation
$$K_p=\left[\frac{4x^2}{1-x^2}\right]\times P$$ for this reaction I get $K_p=\frac43\pu{ atm}$ and then $K_c=0.043$.
The answer is 2 but how?


texts: How does one determine the probability of H⁺ to H₂O in pure water?

texts:
The ratio of $\ce{H+}$ to $\ce{H2O}$ is something around $10^{-8}$. How did people determine that?

You cannot use the $K_\mathrm{w}$, $\mathrm{p}\ce{H}$, $\ce{[H+]}$ ion concentration value to answer because you get all that from the probability.                                                                   Is there any independent way to find the probability. Please elaborate on the steps.
I do not want to know why the ionic product is what it is. how was the ionic product found ?


texts: Why do real gases deviate from ideal gas behavior?

texts:
While studying Gaseous state in books, there was a common question which I had difficulty answering -

Why do real gases deviate from ideal behavior (3 points)?


texts: Different force constant in ground vs excited state in spectroscopy

texts:
The force constant of iodine in the first excited state is $k=41.78$ N/m, and in the ground state it is $170$ N/m.

I know that the formula for calculating $k$ is:

$$ k= (\frac{ΔE_{vib} *2π}{h})^2 µ$$

What causes this difference?

Is it that the energy difference for the ground state is greater then that of the excited state and so the force constant is also greater?


texts: Energy absorbed by the gas from a PV-diagram

texts:
The $PV$-graph for a monoatomic gas is shown in the figure. Find the energy absorbed by the gas during this process.

I’m having trouble with this question because both pressure and volume are changing and I cannot calculate a value for $T$. So far, I ended up with an answer using the ratio of $C_p$ and $C_v$, and got $6.25P_0V_0$. The answer is $8.5P_0V_0$.


texts:
I’m a bit confused regarding cell potentials. If I have two half  reactions each involving a different number of electrons, there are two ways I can see to calculate the net emf of their cell:

Simply add the potentials across the two theoretical half cells, that is, treat each half reaction as a voltage source in series
Calculate the value for the net cell reaction as a whole, that is, make consideration for the energetics of the reaction

As a more specific example, say I have a metal $\text M$, and $$\ce{E^0_{M^{3+}/M}=2V, E^0_{M^{2+}/M}=1V}$$ and would like to figure the standard cell potential, say $x$ of $\ce{E^0_{M^{3+}/M^{2+}}}$.
With Method 1 we have $$x= \ce{{E^0_{M^{3+}/M}}-{E^0_{M^{2+}/M}}}=2-1=\mathbf{1V}$$
With Method 2 we have $$\ce{\Delta G^0_{M^{3+}/M}=-3*F*2=-6F, \Delta G^0_{M^{2+}/M}=-2*F*1=-2F}$$
$$\implies \ce{\Delta G^0_{net} = -6F - (-2F) = -4F}$$
$$\implies x=\frac{-\ce{4F}}{\ce{-1*F}}=\mathbf{4V}$$
How do I rectify these inconsistent values? Does it make any difference here whether I say I am looking for $\ce{E^0_{M^{3+}/M^{2+}}}$ or $\ce{M|M^{2+}(1 molar)||M^{3+}(1 molar)|M}$? What if I use an inert electrode like $\ce{Pt}$ in the latter representation?
Further, if I have another metal $\ce Y$ for which $\ce{E^0_{Y^+/Y}}=\ce{3V}$, which is a stronger oxidizing agent? $\ce{M^{3+}}$ or $\ce Y^+$?
In various sources it seems some use method 1 while others use 2. In this answer on CSE it seems 1 is the right one. But I maybe missing some conceptual context.
Thanks!


texts: What actually happens to the volume of a gas in an isolated system?

texts: In an isolated system with adiabatic walls in which gas is filled what exactly happens? How do we define the volume of a gas here? Is volume of 1 mole of gas  present in that inelastic container the same as the volume of say 5 moles of the same gas in that container?


texts: What's the evidence that it is the nitronium cation (NO2+) acting as the attacking electrophile in mixed acid nitration of aromatic compounds (SeAr)

texts:
As per the title, I'm looking as to what is the evidence is that it is the $\ce{NO2+}$ cation acting as the attacking electrophile in an electrophillic aromatic substitution reaction involving the 'mixed acid' reagents of $\ce{H2SO4 + HNO3}$

I have considered the following although I feel as if other explanations exist and doesn't really specifically tackle the question:

The generation of the electrophile is as follows

$$\ce{2 H2SO4 + HNO3 -> H3O+ + NO2+ + 2 HSO4-}$$

Of which has been shown to be valid via spectroscopy methods & being consistent with the expected freezing-point depression. The $\ce{NO2+}$ cation can be trapped within unreactive anions (such as $\ce{BF4-},\ce{PF6-}$) to form salts which can then themselves act as nitrating agents to obtain the same nitration reaction product.


texts: What is the definition of porous materials?

texts:
Is there a consensus on scientific definition of porous materials? There are many definitions out there which do not seem accurate enough:

from wikipedia (accessed July 2017):
A porous medium or a porous material is a material containing pores (voids).

-problem : Then almost all materials are porous, since there is some sort of void in everything.

from Merriam Webster (website accessed July 2017):
Containing pores, permeable to fluids, capable of being penetrated.

-problem : A piece of tubing would be porous since fluid passes through it.

At what scale do we consider the pores to qualify a material as porous? How much does the permeability matter in a formal definition? Is there a convention on defining pores and porous materials that is agreed upon by scientific organizations like IUPAC or ASTM etc?


texts:
There is a sentence in my book I don't understand:

  Every atom or ion, which has one valence electron, will have double lines in the atomic emission spectrum. For example $\ce{Na}$ will produce lines at $589.0\:\mathrm{nm}$ and $589.6\:\mathrm{nm}$.

Why does this happen?


texts:
Priority to longest carbon chain or double bond?

Above structure and its nomenclature is given in my notes. However, I suspect it is wrong because the Carbon chain of 8 instead of 7 is available. So my question is do we give preference to double bond over the number of carbon in a chain during nomenclature?

I found this question here but it only makes me more confuse as its answer states that we give preference to the carbon chain. So is my notes are outdated(which is possible) or is there any other rule which I am unaware of?


texts: Have we found stable, super-heavy elements?

texts: Have we found a stable super heavy element or created one in a lab, or are they still hypothetical?


texts: How can the trityl tetrafluoroborate function as a Lewis-acid catalyst

texts:
Trityl tetrafluoroborate is a reagent sometimes used in synthesis as a very mild Lewis acid catalyst, and recently I've been (unsuccessfully) using it in some protecting group chemistry.  Several other uses are mentioned in eROS:

  ...for various transformations, e.g. the Mukaiyama-type aldol reaction using a dithioacetal and silyl enol ether. It has also been used as the catalyst for the formation of glycosides from alcohols and sugar dimethylthiophosphinates and for the formation of disaccharides from a protected α-cyanoacetal of glucose and a 6-O-trityl hexose. Michael additions of various silyl nucleophiles to conjugated dithiolenium cations also proceed well. Finally, the [4 + 2] cycloaddition of cyclic dienes and oxygenated allyl cations has been effected with trityl fluoroborate.

  Ref: Encyclopaedia of Reagents for Organic Synthesis

Clearly, the trityl cation could act as a Lewis acid catalyst (or at least its reactivity suggests that it does), and indeed it has a vacant p-orbital allowing it to accept an electron pair (the IUPAC gold book definition being a molecular entity that is an electron-pair acceptor).

What makes less sense to me is the 'mechanism' this catalysis occurs by. The cation itself is pseudo-stable (relative to a standard planar carbocation intermediate such as that observed in an SN2 reaction)  since the aromatic rings are able to stabilise the positive charge, but even if it did react, surely one would expect this to be irreversible, such that a nucleophile would attack the vacant p-orbital to form a stable compound, killing off the reaction.

To give an example of this, trityl tetrafluoroborate may be used to protect an alcohol with a DMB protecting group. What isn't observed is the alcohol attacking the cation to form an O-trityl bond (the trityl group itself is sometimes seen as a protecting group).