texts: Why do ionic compounds dissociate whereas coordinate complexes won't?

texts:
An ionic bond is the bonding between a non-metal and a metal, that occurs when charged atoms (ions) attract after one loses one or more of its electrons,and gives it to the other molecule, for example sodium and chlorine. This makes the bond stronger and harder to break.
  In other words, an ionic bond is the electrostatic force of attraction between two oppositely charged ions. The positive ion is called cation, and the negative ion is the anion. It is like the north and south poles of a magnet.
  A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms. The stable balance of attractive and repulsive forces between atoms when they share electrons is known as covalent bonding. For many molecules, the sharing of electrons allows each atom to attain the equivalent of a full outer shell, corresponding to a stable electronic configuration.
  A dipolar bond, also known as a dative covalent bond or coordinate bond is a kind of 2-center, 2-electron covalent bond in which the two electrons derive from the same atom.
  NOTE: It is important to recognize that pure ionic bonding - in which one atom "steals" an electron from another - cannot exist: all ionic compounds have some degree of covalent bonding, or electron sharing. Thus, the term "ionic bond" is given to a bond in which the ionic character is greater than the covalent character - that is, a bond in which a large electronegativity difference exists between the two atoms, causing the bond to be more polar (ionic) than other forms of covalent bonding where electrons are shared more equally. Bonds with partially ionic and partially covalent character are called polar covalent bonds. Nevertheless, ionic bonding is considered to be a form of noncovalent bonding.

$$\begin{equation}\tag{1}F=\frac{1}{4\pi\epsilon}\cdot\frac{q_1q_2}{r^2}\end{equation}  $$
 According to Coulomb's law equation $(1)$, the force between two charges depend on the medium in which they are placed. The value of $\epsilon_r$ (relative permitivity) of air is found to be approx $1$, whereas relative permittivity of water is found to approx $80$ at room temperature.

I thought Coulombs law could answer why ionic compounds dissociate into ions whereas other compounds of different bonds won't. I thought, ionic compounds are formed by the electrostatic interaction of two oppositely charged ions (I assumed these to be charges), they will be stable in air, as relative permittivity value is not much effective. When, the same is dissolved in water, I thought they will dissociate as relative permittivity value of water effects more. I found the explanation, so as to why ionic compounds dissociate into ions when dissolved in water. In case of coordinate bond, I thought an atom losses a pair of electron and thus can be called as cation, whereas the other becomes anion. So, even here we can expect electrostatic interaction, and as discussed above must dissociate into ions when dissolved in water. But coordination complex of coordinate compound won't dissociate? I think, I have misunderstood somewhere or else there must be some chemistry theory which could explain, why coordinate complex won't dissociate?

Even in case of covalent bond we can see the bond to be formed by stable electrostatic attraction and repulsion between electrons and protons, so I thought, even covalent bonds should break, when dissolved in water, as electrostatic interaction is going to be affected. I thought, there must be some other forces which must be keeping them bonded. If so what are they?

I don't know whether I am right or wrong, if any was the case please explain.


texts:
The system of constant entropy and constant volume will attain the equilibrium in a state of minimum energy. Why?

I know that:

$\Delta G= \Delta H-T\Delta S$
And at constant volume and entropy: $\Delta G =\Delta U$

But from above equations how can we justify the give statement?


texts: Which d orbitals are used in sp3d3 hybridisation?

texts:
What d orbitals are used in the hybridisation of the molecule $\ce{IF7}$. I know the hybrid state of Iodine is $sp^3d^3$ i.e. 3d orbitals are involved in hybridisation.

Some say they are $d_{(xy)}, d_{(yz)}, d_{(zx)}$ and some say $d_{(x^2-y^2)}, d_{(z^2)}$ and $d_{xy}$ are involved? Also what is the theoretical reason for it. Like I know for $sp^3d^2$ hybridisation only $d_{x2-y2}$ and $d_{z^2}$ are involved because they lie along x,y,z axes and so do the hybrid orbitals like in $\ce{SF6}$ each angle is π/2. Is there some theoretical explanation for $\ce{IF7}$ also which has pentagonal bipyramidal shape?

I know a very similar question has already been asked; How can the Bonding in IF7 be explained using LCAO method?

But it says that bonding in $\ce{IF7}$ cannot be predicted as bonds are predominantly ionic plus the answers mentioned there are using very complicated principles and theories which I am unaware of. I only know the basic theories of VSEPR, Valence Bond and the  hypothetical concept of hybridisation plus very little Molecular Orbital Theory. May someone explain the bonding in $\ce{IF7}$ in a fairly simple manner especially the d orbitals used in its hybridisation. I am not specifically asking for $\ce{IF7}$ but any molecule showing $sp^3d^3$ hybridisation?


texts: When we react a ketone with NaBH4, it reduces to alcohol. I coudn't understand the mechanism of this reaction. The first step in my text book states that the hydrogen from NaBH4 attacts the carbonyl carbon. I didnt't understand why this happens. Specifically, I coudn't understand why the Boron didnt attack oxygen instead.


texts: How to dissolve a strong resin in difficult situation?

texts:
The resin is made up from two components:

Component A: silicic acid, sodium salt (less than 10% sodium silicate)

Component B: Diphenylmethane-4,4'-Diisocyanate, isomers and homologs (MDI,Polymer-MDI)

It has been cured in place, however it became stuck to a piece of equipment made out of rubber.
It is stuck several meters down a line so access is very limited.

Is there anything that would be strong enough in small quantities to dissolve or even loosen this adhesive?

Any thoughts on a mixture of water 90%, ammonia 8% and detergent 2%?
Would I need a large quantity of this mixture or how effective would it be?
Or a mixture of the same except using sodium carbonate instead of ammonia?

Any help or suggestions would be greatly appreciated.

Thanks


texts: Is there a way to tell which one is the racemic or meso compound with 1H-NMR if all you had was the structure and spectra?

texts:
I know that diastereomers will have different chemical shifts but can you predict which one is which via up/down field shifts in the spectra?

For instance, is it like alkenes vicinal H’s when cis and trans are up and down field respectively?

I ran a 1H-NMR of hydrobenzoin and when comparing it to the literature I noticed that the racemic mixture was further upfield than the meso.

I made the Newman projections below and assumed the most energetically favorable positions to show the cis and trans H’s in the diastereomers.

Is this the right way of thinking about this?


texts: Calculating amount of ice required for heat loss

texts:
Question:

  Given $400.0\ \mathrm{g}$ of hot tea at $80.0 °\mathrm{C}$, what mass of ice at $0 °\mathrm{C}$ must
  be added to obtain iced tea at $10.0 °\mathrm{C}$? The specific heat of the
  tea is $4.18\ \mathrm{J}/(\mathrm{g}\ \cdot°\mathrm{C})$ , and $\Delta H_{\mathrm{fusion}}$ for ice is $+6.01\ \mathrm{kJ\ mol}^{-1}$ .

$q$ is the amount of heat transferred. Since the solution is decreasing heat, then $q_{\mathrm{ice\ tea}}=-q_{\mathrm{ice}}$ We can then solve q using the information given.

$q_{\mathrm{ice}\,\mathrm{tea}}=\left(\dfrac{4.18\,\mathrm{J}}{\mathrm{g}\cdot ^{\circ}\mathrm{C}}\right)(400\,\mathrm{g})(-70\,^{\circ}\mathrm{C})=-1.17\times 10^5\,\mathrm{J}$

The next part cofuses me, this is what the solution manual does.

$q_{\mathrm{ice}}=1.17\times 10^{5}\,\mathrm{J}=(6.01\,\mathrm{kJ\ mol}^
{-1})\left(\dfrac{1000\,\mathrm{J}}{1\,\mathrm{kJ}}\right)\biggl(m_{\mathrm{ice}}\times\dfrac{1\,\mathrm{mol}\,\mathrm{H}_{2}\mathrm{O}}{18.02\,\mathrm{g}\,\mathrm{H}_{2}\mathrm{O}}\biggr)$

$\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;+\left(\dfrac{4.18\,\mathrm{J}}{\mathrm{g}\ \cdot\ ^{\circ}\mathrm{C}}\right)(m_{\mathrm{ice}})(10.0\ ^{\circ}\mathrm{C})$

I'm not too sure where this equation is derived from or of its purpose. The top part is determining the the enthalpy of ice but why is it being added to the specific heat of ice?


texts: Rationalizing the Planarity of Formamide

texts:
In formamide, the nitrogens appear to be $\ce{sp^3}$ hybridized, implying tetrahedral geometry. However, analysis shows that the molecule is actually very nearly planar with bond angles close to 120 degrees.

EDIT: as suggested by Martin and another poster, hybridization is a rough concept. So perhaps the hybridization of nitrogen upon further analysis should best be described as somewhere inbetween $\ce{sp^3}$ and $\ce{sp^2}$. This however would still necessitate planarity, correct? Pi bonds are formed through the above and below electron-pairing in p-orbitals; effective bonding is achieved when these p-orbitals are parallel with respect to each other.

I'm thinking this has to do with the partial double bond character in the molecule (also appears to be some ionic character to the molecule - likely due to electron-withdrawing effects of the nitrogen and the oxygen).

This is the standard answer. However, would intramolecular hydrogen bonding also play a role? Couldn't there be a hydrogen bond between the peripheral hydrogen on the nitrogen and the oxygen? Couldn't this also help with achieving the 120 degree bond angles?


texts: How would I synthesize ethyl 2‐oxocyclohexane‐1‐carboxylate from cyclohexanone?

texts: I thought the 1st step would be deprotonation of a H atom to form the enolate. Then an aldol reaction, but the product I end up with is the alcohol, not the ketone.


texts: Why is a 3° Carbanion unstable than 1° Carbanion? Carbon atom with negative charge will become little electropositive relative to a neutral carbon. So if a Carbanion is attached to three neutral carbons, essentially it should donate it's electrons distributing the negative charge of -1, thus stabilizing it. By this logic, more carbon atoms attached means more stability. But this does not happen. 1° Carbanion is most stable. Why?


texts: Can I obtain a different density of a recycled elemental material?

texts: I am recycling Aluminum products/scrap. I melted it and then form cylindrical ingots. When I measure their density, I calculated $\pu{2.4 g/cm^3}$ but Al has density of $2.7$. I think all the materials are aluminum since they all melt in the same temperature using a home setup. Can I claim that the ingot is Al?


texts: Why are halogens ortho para directing even though deactivating?

texts: Halogens bonded to benzene ring has three lone pairs. These three electron pairs can cause resonance in benzene ring. But, halogens are also highly electronegative and thus they have strong -I effect. So, they are deactivating groups. But, why are they ortho para directing?


texts: Isothermal compression at critical temperature

texts: Suppose I am compressing a gas isothermally at its critical temperature. Initially, it has a large volume. I start compressing it and reach the critical point. At this point, the gas will start to form liquid and both of these phases cannot be distinguished, right? Now if I further compress it isothermally at its critical temperature so that the pressure reaches beyond critical pressure, what will my gas look like? Will it be a liquid or a gas or something in between, I don't know. Is there a video where I can see something of this sort? Just curious


texts: Why won't ethene and ethyne react with halogens?

texts:
With alkanes, a free-radical halogenation (substitution) is observed.

I was told that there will be no reaction in a similar situation with ethene and ethyne — and I am having trouble understanding why.

Is it because the halogen radical will not be able to abstract a hydrogen atom from carbon because it is influenced by the greater electron density in the carbon-carbon double/triple bonds? Or because the $\ce{C-H}$ bonds are shorter in these molecules compared to alkanes? (resonance?)

I've assumed that the problem arises in the propagation step of the most common reaction mechanism seen with alkanes.

Or is it due to sterics? ($\unicode[Times]{x3c0}$-bonds get in the way of the attacking bromine radical or restricted rotation in double/triple bonds get in way of ideal orientation for reaction to proceed to the transition state)

The necessary heat/$h \nu$ is provided for the reaction. Additionally, no other reactants/catalysts are present.

Please keep your answers on a novice college student level.


texts: Differences in Novichok agent mass spectra

texts:
As we have all heard, in 2018, a series of poisonings with a nerve agent alleged to be of the Novichok series was carried out on British soil. It is claimed that the agent used was A-234. However, a novichok agent was also previously used in the poisoning of a banker named Ivan Kivelidi in 1995.
The Russian Wikipedia page on Novichoks states that not only was the mass spectrum of A-234 published in NIST by someone affiliated with Edgewood Arsenal, but also provides the mass spectrum of the agent used in the Kivelidi case.

Top: Mass Spectrum of chemical agent used in the Kivelidi case. Bottom: Mass Spectrum of A-234 as published by Edgewood.
As one will notice, the spectra almost match, except for the fact that the top spectrum contains a peak with a mass of 42.The bottom spectrum has no such peak. What is the significance of this peak? How would the structure of the agent in the Kivelidi case differ from A-234? Is the A-234 spectrum correct?


texts:
The question was:

  If you are given a $1$ Litre solution of $\ce{CaF_2}$where there is $2.0 \times 10^{-5}$ M $\ce{Ca^{2+}}$. How many mililitres of $0.1$ M $\ce{NaF}$ would you need to precipitate $\ce{CaF_2}$? The solubility product of $\ce{CaF_2}$ is $1.7\times10^{-10}$ .

The answer given is

   956 ml

What I attempted:
I thought that if $x$ Litres of  $\ce{NaF}$ is necessary to precipitate $\ce{CaF_2}$; then after the mix, the ionic product($K_{ip}$) of $\ce{CaF_2}$ will exceed the solubity product($K_{sp}$). $$K_{ip} > K_{sp}$$
$$\ce{[Ca^2+][F-]^2} > K_{sp}$$  and from this equation I tried to solve the value of $x$.

Here's what I tried in details:-

step 1) Write down the dissociation  reaction of $\ce{CaF_2}$

$\ce{CaF_2 <=> Ca^{2+} + 2F-}$

and from the solubility product formula $K_{sp} = \ce{[Ca^2+][F-]^2}$ I calculated the concentration of $\ce{[F-]}$ which I got was $2.91\times10^{-3}$.

step 2) Then I again calculated the concentration of $\ce{Ca^2+}$ and $\ce{F-}$ after adding  $x$ Litres, using the formula $\ce{S_1\times V_1 = S_2\times V_2}$, because the volume now was not $1$ Litre, but $(1+x)$ Litres.

I got $$\ce{[Ca^2+] = \frac{2\times 10^{-5}}{(1+x)}}M$$ $$\ce{[F-] = ( \frac{0.1x}{1+x} + \frac{2.9\times 10^{-3}}{1+x})}M$$

step 3) Then as I stated before, the condition of precipitation would be as follows
$$K_{ip} > K_{sp}$$
$$\ce{[Ca^2+][F-]^2} > K_{sp}$$

So, from the equation above, I calculated the value of $x$ which I got was $1.8$ Litres (approximately) which was nowhere near the given answer in the book. How to solve this problem?


texts: Why would two isomers have different solubilities in water?

texts: I was wondering as to why, e.g. $\ce{CH3CH2CH2CH2OH}$ and $\ce{(CH3)3COH}$, do not have the same solubility in water, considering they both have the same molecular formula.


texts:
Why does Freundlich adsorption isotherm not have a term for surface area?

The formula given by Freundlich adsorption isotherm:

  $$ \frac{x}{m}= k P ^{1/n}$$
  Where $x$ is the mass of gas adsorbed on mass $m$ of the adsorbent and pressure $P$. $k$ and $n$ are constants which depend on the nature of the absorbent and the gas at a particular temperature.

There is no term for the surface area involved for adsorption and I had read that adsorption increases with the increase in surface area so if I take a highly porous substance, it will adsorb more gas on it. What am I missing here?

Edit: Actually, what I mean is that, let's say I have a single piece of adsorbent, it has a certain value of $x$ for a given $P$. Then I break it into 10 pieces, The value given by the formula is still the same, while there will for sure be an increase in $x$, due to increased surface area.


texts: Are there any magnetic particles that are safe to inhale?

texts:
In medicine, there is an (old?) experiment where a subject is asked to inhale radioactive Xenon gas, and radiation counters are placed at different positions near the lungs. Using this experiment, it has been demonstrated that the (alveolar?) volume of the lungs is highest in the bottom parts, and smallest in the top parts.

I don't know if this experiment is still used today, since inhaling radioactive gas has the obvious radiation related risks.

I was wondering if there are some magnetic particles that would be safe to inhale? I know that for example helium does not diffuse into blood, and it does not permanently bind into anything. However, I think it does not have any suitable magnetic properties. Let's assume the detector is very very sensitive to any magnetic fields (so, a super-conducting quantum interference device).


texts: Who developed the concept of ICE tables?

texts:
Many general chemistry courses (at least in the US) or online tutorials solve problems of chemical equilibrium by using ICE (sometimes RICE) tables, which track how the moles of reactants and products change going from an initial state to equilibrium.

I'm curious when this technique became so widespread and who developed it? My understanding is that ICE tables are a somewhat modern pedagogical tool, but I have yet to find a source for the idea and when it was popularized.


texts: Can the Arrhenius equation be used if the reactants are in the solid state and if I can use it for any state, how do I do so?


texts: Sodium-24 decays into an excited nucleus of magnesium-24. Magnesium reaches nuclear ground level via two consecutive gamma emissions. What are the half-lives (time scales) for these two processes? I think that those gamma photons are emitted very rapidly after Mg-24 is formed. I'm curious to know but I cannot find data. I'm a Chem undergrad with interests in nuclear chemistry.


texts: Mechanism for oxidative workup of ozonide

texts: Oxidative workup of ozonide produces ketone (in case both the substituents of carbon are alkyl groups) or carboxylic acid (in case one of the substituents is hydrogen), depending on the alkene. I have tried for the following mechanism with hydrogen peroxide but unable to find the exact one.


texts:
An atom typically consists of electrons, protons, and neutrons. Electrons are negatively charged and participate in bonding to stabilize the atom.

Conversely, protons are positively charged and balance the charge of the atom. In addition, their positive charge attracts the negatively charged electrons.

What role do neutrons play in an atom?


texts:
I'm struggling to understand why the element Nickel can be written like so: [Ar]3d84s2, but cannot be written as [Ar]3d10.

I know that the d-orbital can 'house' 10 electrons, and that according to the Aufbau principle, electrons must be 'housed' in the vacant orbital which has the lowest energy, so the first way I presented seems wrong to me.

I'm sure that there's some confusion on my end here, or rather, I'm missing something that might seem obvious, but I really don't get it.


texts: Reaction of 1,3-dibromobutane with zinc dust upon heating

texts:
I've studied that when 1,3-dibromopropane (or in general any halogen, not just bromine) is heated with Zn dust, the electrons produced cause the halogens to break away homolytically and two free radicals are formed. These free radicals then combine to form cyclopropane.

My question is, will this also occur for 1,3-dihalides when the carbon count is increased, say in 1,3-dibromobutane?
Everything I found related to this was either talking about the 3-carbon dihaloalkane case, or seemed to be some complicated free radical cyclization which was way out of my reach.


texts: Could detergents dissolve cell membranes?

texts: Animal cells have a lipid membrane and detergents are great at emulsifying lipids. Yes, there are proteins, cholesterol and other numerous substances in the lipid bilayer, but the lipids make up the majority of it. If we dipped a bacterium or an isolated animal cell in detergent, would their membrane be dissolved?


texts: Negative DBE/Degree of Hydrogen Deficiency?

texts: I tried calculating the Index of Hydrogen Deficiency for C6H15SiCl, and I get negative one. I get this value by subtracting the number of chlorine and hydrogen atoms from that of the carbon atoms, and then adding one. I don't think I am supposed to do anything with the number of silicon atoms.  Is this correct/normal?


texts: What is the name of the formula ΔE = q + w?

texts:
What is the name of this formula? Google could not provide me with an answer.

$$\Delta E=q+w$$


texts: Relative rates of two acyclic dienes in the Diels-Alder reaction

texts:
As for factors that affect the rate of the Diels Alder reaction, having an s-cis conformation is primary.

But in a case as shown below, what makes the second diene react faster compared to the third?

The only reason I can think of is that the second diene has substituents pointing outward so they cause less steric hindrance as it reacts with a dienophile thus has a lower activation barrier. Are there any other underlying reasons apart from hindrance?


texts: How do we indicate a volume fraction like 0.05 in procedure descriptions?

texts:
I'm translating a Russian biotech text, and there's this sentence with a number without measurement units:

  The contents of the wells were discarded; the wells were washed three times with 200 µL of Buffer containing 0.05 of Tween 20.

I was told that this figure indicates a volume fraction, and is dimensionless, hence no units after it. Will this be understood by the native speaker of English as-is, without any units, as in my quote?

Or is it better to write it down as:

  The contents of the wells were discarded; the wells were washed three times with 200 µL of Buffer containing 5% (v/v) of Tween 20.

Or maybe like this:

  The contents of the wells were discarded; the wells were washed three times with 200 µL of Buffer containing 5 vol% of Tween 20.

Is there a way to retain 0.05 and somehow indicate that this is a volume fraction?


texts: Why isn't CASPT2 used in surface hopping simulations?

texts:
I will write what I think the answer is. I'd like someone to confirm and maybe explain in detail.

I think that since surface hopping dynamics simulates movements on PES, it has to calculate gradients in each step. Since gradient for CASPT2 method can be evaluated only numericaly, CASPT2 quantum mechanical base for surface hopping dynamics would make calculations imspossibly slow.

Is this correct?


texts: Would there be a difference if deuterium is embedded instead of protium (regular hydrogen) in acids?

texts: So instead of regular hydrogen, it would be a deuterium (still a Hydrogen). For example, instead of $\ce{HCl}$ it would be $\ce{DCl}$ where D is a deuterium.


texts: Six independent papers reporting epitaxial formation of silicene in 2012

texts:
According to a Nature news article cited below (info-box "The rise of silicone"), six independent papers were published reporting successful epitaxial formation of silicene.
Does anyone know which those were? I am just able to find the following two papers:

Fleurence, A., R. Friedlein, T. Ozaki, H. Kawai, Y. Wang, Y.
Yamada-Takamura (2012). "Experimental evidence for epitaxial silicene
on diboride thin films". Physical Review Letters 108(24)
Vogt, P., P. De Padova, C. Quaresima, J. Avila, E. Frantzeskakis, M.C. Asensio, A. Resta, B. Ealet, G. Le Lay (2012). "Silicene: compelling experimental evidence for graphenelike two-dimensional silicon". Physical Review Letters 108(15)
Nature (2015). "Graphene’s cousin silicene makes transistor debut". Nature news article. URL: http://www.nature.com/news/graphene-s-cousin-silicene-makes-transistor-debut-1.16839

Does anyone know where to find the other four?


texts:
How can we identify bases and acids by their chemical formulas?

Take for example this reaction. I know that HNO3 is an acid and KOH is a base, but if I didn't know that how would I be able to identify that using the chemical formulas

$\ce{HNO3(aq) + KOH(aq) \rightarrow KNO3(aq) + H2O(l)}$


texts: Help on alternative terpene names and naming schemes

texts:
I am a software developer and currently parsing data involving terpene profiles of plant samples. The data in question uses different ways of naming the same terpenes in-between samples and since this is not my field I would like to ask:

if there is an online index showing all possible names for a specific terpene or
if there is a software library for normalizing those names or
if somebody could simply tell me which ones of the attached list are the same terpene and what the recommended naming scheme would be

The list of terpenes I am concerned with is as follows:

3-Carene
α-Bisabolol
α-Humulene
α-Pinene
α-Terpinene
β-Caryophyllene
β-Myrcene
β-Ocimene
β-Pinene
Camphene
Caryophyllene
Caryophyllene Oxide
CaryophylleneOxide
cis-Nerolidol
δ-Limonene
DLimonene
Eucalyptol
Geraniol
Guaiol
Humulene
Isopulegol
Linalool
Ocimene
PCymene
p-Cymene
Terpinolene
trans-Nerolidol
TransNerolidol 1
TransNerolidol 2
trans-Ocimene
γ-Terpinene

(Some of those names are obvious duplicates of others, but I just wanted to give you the full, unaltered list here)

If anyone could point me in the right direction I would be very grateful!


texts: Why is propanoic acid weaker than butanoic acid?

texts:
I was reading about electronic effects in organic compounds, and I found the explanation that carboxylic acids are weakening as their number of carbon atoms increase.

But I found a table of $K_\mathrm{a}$ for different acids, and it writes that $K_\mathrm{a}$ for propanoic acid is $1.34\times 10^{-5}$ while butanoic acid's acidic constant is $1.48\times 10^{-5}$. This means that butanoic acid is stronger than propanoic acid, but isn't this a contradiction to the inductive effect?


texts: What are the products in the reaction of sulphuric acid and Group 2 metals?

texts:
When group 2 metals, says magnesium, is reacted with nitric acid, oxide of nitrogen is produced beside hydrogen gas. The standard electrode potential values agree with this:

$$
\begin{align}
\ce{Mg^2+(aq) + 2 e- &<=> Mg(s)} &\quad E^\circ &= \pu{-2.38 V} \\
\ce{H+(aq) + e- &<=> 1/2 H2(g)} &\quad E^\circ &= \pu{0 V} \\
\ce{NO3-(aq) + 4 H+ + 3e- &<=> NO(g) + 2H2O(l)} &\quad E^\circ &= \pu{+0.96 V}
\end{align}
$$

Does sulfate ion from sulfuric acid is reduced too when reacted with group 2 metals? The standard electrode potential values suggest it is possible, but I can’t find any source from internet stating $\ce{SO2}$ is produced from reaction of sulfuric acid with, says, magnesium.

$$
\begin{align}
\ce{Mg^2+(aq) + 2 e- &<=> Mg(s)} &\quad E^\circ &= \pu{-2.38 V} \\
\ce{SO4^2-(aq) + 4 H+ + 2 e- &<=> SO2(g) + 2 H2O(l)} &\quad E^\circ &= \pu{+0.17 V}
\end{align}
$$

If sulfate ion can’t be reduced by magnesium to sulfur dioxide, then what’s the reason?


texts: Temperature and moles of gas given volume, pressure, enthalpy and constant pressure molar heat capacity

texts:
I've been assigned this question as homework and have been attempting it for hours but cannot seem to get anywhere. Any help would be greatly appreciated!

An airbag of volume $40\ \mathrm L$ is inflated adiabatically through the following reaction:
$$\ce{NaN3(s) -> Na(s) + 3/2N2(g)}$$
One mole of $\ce{NaN3}$ decomposed produces an enthalpy of $-23.1\ \mathrm{kJ}$. $60\ \%$ of this energy is deposited in the gaseous product; assume the decomposition is instantaneous. $C_{\mathrm m,p}(\ce{N2})=29.12\ \ \mathrm{J\ mol^{-1}\ K^{-1}}$. When fully inflated, the pressure of the $\ce{N2}$ gas inside the airbag is $2.5\ \mathrm{atm}$.
Estimate the mass of $\ce{NaN3}$ needed to operate the airbag and state any assumptions or approximations being made.

So far, I'm only sure that I've done the following correctly:
$H=U+PV=q+w+PV$ where $q=0$ since the process is adiabatic, so $H=w+PV$
For the expansion of $\ce{N2}$ gas:
$H=0.6n(23.1\ \mathrm{kJ})=n(13.86\ \mathrm{kJ})$ where $n$ is moles of $\ce{NaN3}$
$n(13.86\ \mathrm{kJ})=U+PV$ so $U=n(13.86\ \mathrm{kJ})-(2.5\ \mathrm{atm})(40\ \mathrm L)=n(13.86\ \mathrm{kJ}-RT)$
$q=0$, $P=2.5\ \mathrm{atm}$, $V=40\ \mathrm L$ and $C_{\mathrm m,p}(\ce{N2})= 29.12\ \mathrm{J\ mol^{-1}\ K^{-1}}$
I'm not sure what else to do from here. I'd really appreciate any advice or if anyone could point me in the right direction. Thank you!


texts:
I searched the net and a lot of books, but I was unable to find any information about dichlorine pentoxide.

Does dichlorine pentoxide($\ce{Cl2O5}$) exist?
If it doesn't exist, then why so?
If dibromine pentoxide and iodine pentoxide do exit, then why not dichlorine pentoxide?


texts: How paper-tag survive in the dry-cleaning process?

texts:
This prevent the clothes from being ruined by ink on the paper tag.

To put the garments attached with this paper through the whole process of dry-cleaning,

I have the questions listed below

paper type?
ink type?
Is paper need to be coated?
if need >> what is this coating technique called?
printing technique (refer to http://en.wikipedia.org/wiki/Printing)

Note that, the dry-cleaning solvent is not just water.

Does that sound scientific?

I don't know the more appropriate place to ask this kind of question. If there is, just let me know.

Thanks,
pakorn


texts: How would you recommend attaching a film of anatase to a flat polycarbonate surface without compromising its photocatalytic characteristics?  The self cleaning paints that I have seen are generally meant for masonry.  Is there a relatively easy way to do it, or is it something that just should not be done around the house?


texts:
According to this Mc Graw-Hill link during a spontaneous redox reaction Gibbs Free Enthalpy must decrease and at the same time the change in the Gibbs Free Enthalpy is the maximum electric work that the reaction can do:
$$\Delta G = W_\text{max}=-n F E_\text{cell}$$
in which $F$ stands for the Faraday constant, the amount of charge carried by one mole of electrons, and $n$ represents the number of moles of electrons to be transferred from the reducing agent to the oxidizing agent
according to the balanced equation, and $E_\text{cell}$ is the electromotive force of the cell, which equals $V_\text{cathod} - V_\text{anode}$, or alternatively, $E_\text{oxidizer} - E_\text{reducer}$ wherein $E$ here stands for the reduction potential. As $\Delta G$ must be nagative in the spontanous direction so $E_\text{cell}$ must be positive.

However, according to the first and second law we have

\begin{align}
&\delta Q-\delta W=\mathrm dU=T\mathrm dS-p\mathrm dV+\sum_i\mu_i\mathrm dN_i\\
&\Rightarrow\;\delta W-p\mathrm dV+\sum_i\mu_i\mathrm dN_i=\delta Q-T\mathrm dS\le0\qquad\because\text{2nd law}\\
&\Rightarrow\;\delta W-p\mathrm dV+\mathrm dG\bigr|_{p,T}\le0\\
&\Rightarrow\;\delta W-p\mathrm dV\le-\mathrm dG\bigr|_{p,T}\\
\end{align}

If $\delta W=p\mathrm dV$ then $\mathrm dG\le 0$, that is, the condition $\mathrm dG\le 0$ coincide with the 2nd law only id the only work done by the system is the pressure work.

Also if $\delta W=p\mathrm dV+\text{other works}$, then $\text{other works}\le-\mathrm dG\bigr|_{p,T}$. This means the change in the "minus Gibbs function" is the maximum work attainable from the system beside the pressure work. This extra work can be positive or negative, in the form of electric work or friction work or etc.

Now here I have some problems with the content of the link provided at the beginning of my question, as follows:

First of all, the maximum work that a system can do on its surrounding equals minus the change of the Gibbs Free Enthalpy, so the equality $\Delta G=W_\text{max}$ doesn't hold!?
If $\Delta G=W_\text{max}$ is valid, that is, I mean if the work attained is the maximum possible, then the process must be assumed as reversible , but if the process is reversible thenwe will need $\Delta G=0$ and not $\Delta G<0$, so that the process should be at equilibrium and spontaneous in no direction!?
That the Gibbs Free Energy must decrease in a closed system in the constant temperature and pressure is true only when the only type of work which is done is in the form of pressure work in expansion of the system's volume, not if other works like friction or electric works are also available, so that again using at the same time $\Delta G=W_\text{max}$ and $\Delta G\le0$ is misleading!?
The electric work is an internal work for a system containing the redox reaction and shouldn't enter the above formulation at all, as by work in the 1st law formulated above we mean only those work-based energy transport that occur at the boundaries of the system. So the electric force can never enter this formulation unless we change the control system under study, isn't it right?
And the main question. if I was wrong in analyzing the content of the provided link (which is very probable) where is my mistakes and if I was correct then how can I obtain the same result (which is certainly correct), that "in a spontaneous redox reaction we should have $E_\text{oxidizer}-E_\text{reducer}\ge0$"?


texts:
Usually branching (or decrease in surface area) leads to increased volatility. But in case of alcohols, my book states that:

  The higher alcohols (butanols to decanols) are somewhat viscous, and some of the highly branched isomers are solid at room temperature.

Here the decerease in surface area did not increase the volatility; on the contrary, volatility has considerably reduced.

What is the reason of this anomaly? Or is this even an anomaly?


texts: Partial pressure and chemical equilibirum

texts:
Suppose I am given following reaction in a vessel:
  $$\ce{NH4HS(s) <=> NH3(g) + H2S(g)}$$
  $P_\ce{NH3} = P_\ce{H2S} = \pu{1 atm}$ at equilibrium; if volume is doubled at this instant, then what would be $P_\ce{NH3}$ at new equilibrium?

I know that as soon as volume is doubled, pressure would drop to half at this instant, and $K_\mathrm{c}$ will have the same value at new equilibrium, but how to actually use this to calculate the partial pressure of ammonia at new equilibrium?


texts:
The process of racemization of an optically compound is entropy driven and hence nature prefers a racemic mixture to an optically active one, which is consistent with the idea of the intuitive understanding of entropy as the degree of randomness or disorder. Then, how can the entropy change of a process of conversion of an optically pure compound to its racemic mixture be computed theoretically or atleast estimated accurately enough so that it can be compared for two different reaction outcomes or the spontaneity of a reaction be estimated?

Moreover, which has higher entropy, a racemic mixture or a mixture of all possible stereoisomers of a compound including the meso form? In the later case, there is more randomness and hence should possess greater entropy. Can we treat a mixture of stereoisomers as a mixture of two different compounds and then use their mole fractions (or activities) to calculate the entropy of mixing which in case of gases is $-nR(x_1\ln {x_1} +x_2\ln{x_2})$.


texts: Is the change in enthalpy (ΔH) for dissolution of urea in water positive or negative?

texts:
To test the properties of a fertilizer, $\pu{15.0g}$ of urea, $\ce{NH2CONH2_{(s)}}$, is dissolved in $\pu{150 mL}$ of water in a simple calorimeter. A temperature change from $\pu{20.6^\circ C}$ to $\pu{17.8^\circ C}$ is measured. Calculate the molar enthalpy of solution for the fertilizer urea

I worked through this question by finding $Q = mc\Delta T$, and then dividing $Q$ by the moles of urea present. I can tell the process is endothermic because $\Delta T$ is negative, however my answer for $\Delta H$ comes out as negative, which would only make sense if this was an exothermic reaction. I'm not sure where I am wrong to be honest.
Here is my work:
$$
\begin{align}
\Delta H &= \frac{(\pu{150ml}) \times (\pu{1g mL^{-1}}) \times (\pu{4.18J g^{-1} K ^{-1}}) \times (\pu{-2.8 K})} {(\pu{15g}/\pu{60.07g})}\\
&= \pu{-7030.59J/mol}\\
&= \pu{-7.03kJ/mol}
\end{align}
$$
TL;DR - question asks for $\Delta H$ of an endothermic process, not sure if my answer should be positive or negative


texts: When a carboxylic acid acts as a nucleoplile, why does it attack through the carbonyl bond?

texts:
Here's a couple of examples of what I mean. Firstly, in the reaction with thionyl chloride to make a carboxylic acid:

Secondly, in this specific example of a hydroboration reaction:

I don't really understand why you cant attack from the hydroxide group and then proton transfer. Any suggestions?


texts:
I would like to ask a question about the ordering of the $\ce{X}$ spins on the right hand side of an $\ce{AX2}$ energy diagram.

I was given the diagram here below:

and asked to evaluate why this diagram results in a triplet. This is simple, since there are 4 possible energy transitions, but one of them is equivalent to the singlet transition, hence only 3 transitions would appear in the NMR spectrum.

Prior to this though, I was confused because I thought the ordering for the bottom 3 spins was incorrect. Taking $\ce{\alpha}$ as the lower energy spin, I thought the bottom 3 spins should read as:

$$\begin{align}&\beta \beta \\
 \beta \alpha &~~~~ \alpha \beta \\
 &\alpha \alpha \end{align}$$

and the energy levels would be drawn more appropriately.
I attempted but failed to mention this to the lecturer during the presentation.

Am I correct in this instance?


texts: How is Gibbs free energy related to stability?

texts:
I have been learning thermodynamics for quite some time and I fail to relate Gibbs free energy and stability.
For example, how do I compare stability of metal oxides using the following data?
Also, do stable compounds decompose easily or hard?
$$
\begin{array}{clrr}
\hline
\text{#}  & \text{Compound} & \Delta_\mathrm{f}G^\circ/\pu{kJ mol^-1} & \Delta_\mathrm{f}H^\circ/\pu{kJ mol^-1} \\
\hline
1 & \ce{ZnO(s)} & -318.4 & -348.3 \\
2 & \ce{Cu2O(s)} & -146.0 & -168.8 \\
3 & \ce{HgO(s)} & -58.5 & -90.8 \\
4 & \ce{PbO(s)} & -187.9 & -217.3 \\
\hline
\end{array}
$$


texts: How is ECR (Electron Counting Rule) done in a structure?

texts:
I've been told how to apply the ECR to GaAs{001}(2×4) in my lectures but it makes no sense to me and I don't seem to be able to find any other sources that explain this. (This is a further question on another one posted here .)
Could anyone please tell me how this is done? Or give me some sources on how to apply the ECR?
"This question has been previously asked on the Physics Stack Exchange where it is bountied, but I was told that I should try and post it here as I might be more successful in getting an answer."

This is the explanation I have been given for the following structure:

Count the number of electrons, going down to two of As atoms level with the bottom of the trench and count per unit mesh. There are 8+4 As atoms = 60 valence electrons. There are 6 Ga atoms = 18 electrons. Hence a total of 78 electrons.
Count the bonds that need to be filled :
1. 3 As dimer bonds = 6 e
2. 6 As dangling bonds (2 per dimer) = 12 e
3. Ga dangling bonds (sideways into trench) are empty = 0 e
4. 8 backbonds from top As dimers = 16 e
5. 12 backbonds from Ga to 3rd row As = 24 e
6. 16 backbonds (bulk-like) from 3rd row As to underlying Ga: each takes 5/4 e from As giving 5×16/4 = 20 e
78 electrons for both totals so structure is neutral and should be stable.
I am trying to learn how to do this as I am trying to prove that this is not applicable to the GaAS{001}(2x1) structure, which I believe to be represented like the image below from the help I was given at a previous related question, here.


texts: How to calculate vibrational spectra of organic molecules?

texts: I watched a ted talk (Luca Turin: The science of scent) and was wondering if anyone had any examples of how to calculate vibrational spectra of molecules (used as fragrances)?  Would love to figure out how he computed these charts.


texts: Are there IP limitations on (M)SDS documents?

texts:
Much effort is put in putting together (M)SDS documents:

  Many companies offer the service of collecting, or writing and
  revising, data sheets to ensure they are up to date and available for
  their subscribers or users. Some jurisdictions impose an explicit
  duty of care that each SDS be regularly updated, usually every three
  to five years. However, when new information becomes available, the SDS must be revised without delay.

Are there any intellectual property (IP) limitations on MSDS documents? i.e. are they copyrighted?


texts: Differences between galvanic cells and Li-ion?

texts:
There are clearly some differences between the classical galvanic cell and the Li-ion batteries, but if one looks at the schematics, they looks a bit similar. Please see below:

a) The galvanic cell:

and

b) Li-ion

So I know that in theory there are two fundamental differences between the galvanic cells and Li-ion batteries:

In LIB, the Li ions intercalate in the structure of the anode and cathode
In LIB, there is solid-state mass diffusion of ions.

This is easy to understand, in theory, but what happens in fact in the galvanic cell? Why isn't there any diffusion? Is it because it is not concentration driven (there are two species instead of one)? But if there is no diffusion, how are they moving? In the galvanic cell, are the ions diffusing on the surface of the electrodes instead of intercalation in the structure?

Can anyone help me to understand better the differences between the two cells?

Thank you!


texts: How to rationalise the trend in the covalent radii of the transition metals?

texts: Why do the covalent radii of transition series decrease at the start rapidly, then become almost constant and at the end of series begin to increase from left to right in periodic table?


texts: does Sodium persulfate evaporate at room temperature

texts: I use Sodium persulfate to etch a copper board to manufacture home made Printed Circuit Board (PCB), and I use the same etching tank on the below photo which has no cover on the top. I wonder if it is okay to keep it like that at the room temperature or would it evaporate?


texts:
A glass vessel weighs $\pu{20.2367 g}$ when empty and $\pu{20.3102 g}$ when filled to the etched mark with water at $\pu{4 °C}$. The same vessel was then dried and filled to the same mark with a solution at $\pu{4 °C}$, the vessel was now found to weigh $\pu{20.3300 g}$. What is the density of the solution? (Assume the density of water is $\pu{1.00 g/ml}$)

Here’s what I did:

The mass of the water is just $\pu{0.0735 g}$ when you subtract the weight of (water + vessel) and (empty vessel). Then I found how many $\pu{ml}$ of water there was in the vessel by realizing that the density ($m/V$) must be equal to $1$, so $\pu{0.0735 g}$ of water must be $\pu{0.0735 ml}$ of water too. So with that, I figured out how many grams of the unknown solution were in the vessel ($\pu{0.0993 g}$), and knowing that it was filled to the same “etched mark,” we can say that the density of the unknown solution is $\pu{0.0933 g}/\pu{0.0735 ml} = \pu{1.27 g/ml}$. I went through all of that because I am not sure if my thoughts are on track with logic and I am pretty confused.


texts: In dative bond S→ S, why are the Oxidation state of donor S = +2 and recipient S= -2 although both of them have the same electronegativity?

texts: We know that if the dative bond is directed towards less electronegative element, it is ignored while calculating the oxidations state and it is considered as +2 for donor and -2 for the recipient when it is directed towards the more electronegative species. But in the case of the same electronegative species, Why the second rule (same as directed towards more electronegativity) is used? What is the significance? How is it different from above two condition?


texts: How were old style stereographic structures produced?

texts:
Old papers on chemical structures often contained "3D" renderings of the molecule by using 2 2D images and requiring the reader to go cross-eyed to get the 3D image. A good example I recently found was figure 2 from Carter and Kraut, 1974, which I copied below:

However, this paper is from 1974, which feels like ancient history for 3D graphics. Since I have unrelated interests in molecular biology and 3D graphics, I was wondering how they produced these images so long ago, and if the code to produce them is floating around somewhere. I know there are programs to do it for me because I have seen modern images of proteins that do this, I want the code because I might try to build it into my crappy 3D rendering project that I'm wasting too much time on.


texts: Measuring reaction rates when reactants and products both have (different) molar extinctions at the chosen wavelenghth

texts:
In my Biochem labs we would always measure the consumption of NADH, and they always noted that it was useful that NAD+ had essentially no absorbance at 340 nm, which allowed us to directly relate absorbance to concentration by NADH's known molar extinction coefficient (i.e. all of the absorbance at 340 came from NADH).

I'm imagining that it would be possible to measure a reaction rate where the reactants and products both absorb at a given wavelength, but there is a difference between the reactants and the products. Is this as trivial as saying that for every M reacted, the absorbance will change by the difference in molar extinction coefficients?

I'm just wondering about it because they stressed the value of the lack of A340. Was this just a matter of high responsivity/good signal, and maybe convenience? There is no inherent reason why this wouldn't work, right?


texts: Meaning of the term "Activation of alkene"

texts:
While reading organic texts, I have come across authors referring to "Activation of alkene" what does that mean !? Does it mean to include the alkene in resonance or what else exactly ?
I saw this notation, while reading about Heck reaction:

The palladium-catalyzed C-C coupling between aryl halides or vinyl halides and activated alkenes in the presence of a base is referred as the "Heck Reaction"

I also observed this while reading about nucleophilic conjugate addition:

Ordinary nucleophilic additions or 1,2-nucleophilic additions deal mostly with additions to carbonyl compounds. Simple alkene compounds do not show 1,2- reactivity due to lack of polarity, unless the alkene is activated with special substituents.


texts: Does sour milk have something else in it besides lactic acid that gives it such a horrific taste and odor?

texts:
Even slightly sour milk has a horrible, nauseating taste, while plain yogurt tastes either great, or at least nowhere near as bad. A dozen sources (all of them) say that the sour odor and taste of sour milk and also of yogurt is caused by the presence of lactic acid. Does sour milk have something else in it besides lactic acid that gives it the horrific taste and odor that yogurt (which has plenty of lactic acid it it) almost never has. Or is there more than one kind of lactic acid?
Is the taste of sour milk due to lactic acid and one or more amino acids?
https://foodsafety.foodscience.cornell.edu/sites/foodsafety.foodscience.cornell.edu/files/shared/documents/CU-DFScience-Notes-Milk-Flavor-Defects-Sensory-Eval-04-10.pdf has this to say:
"CHARACTERISTICS OF MILK OFF-FLAVORS...
Typical Milk:
No criticism. Very little distinct odor, pleasantly sweet and clean with no aftertaste...
Acid:
Basic taste sensation. Sour, tart, may cause tingling sensation on tongue. “Cultured milk” or “sour” odor may be present. Cause: Growth  of  lactic  acid  producing  organisms  such  as Lactococcus lactis,  due  to  poor refrigeration, especially when temperatures exceed 70°F (21°C)."
Like everyone, the Cornell author explains the sour taste and odor of sour milk by referencing only lactic acid.
https://www.nationalgeographic.com/culture/article/when-good-milk-goes-bad is no different when talking about slightly sour milk, as opposed to the much later (very) spoiled moldy milk, which involves yeasts and molds and ...danger.
https://www.reddit.com/r/chemistry/comments/j15maj/what_does_lactic_acid_smell_like/ says pure lactic acid does not smell bad. Aha! On the other hand, it does say whether or not it smells like sour milk. What a pity.
To those that nitpick that it is subjective to say that sour milk tastes awful, I say this: 1. Taste and odor is subjective, obviously. 2. I Googled 'Sour milk tastes okay' and there was not one relevant hit so people are not in any way divided on this. 3. This is an SE question, not an academic paper.


texts: It is found that increasing composition of $Ethanol$ in $Ethanol$-$water$ mixture increases the viscosity of the mixture upto certain composition, but after that the viscosity begins to decrease again. I could not figure out any theoretical explanation to this phenomenon. Any help with theoretical reasons will be appreciated.


texts: I am trying to figure out what makes an electrolyte better than another. I originally thought it was acidity, but a potato produces more voltage than a lemon. When I tried this same thing with acetic and muriatic acids, I found that acetic acid produced a constant voltage of a little under 1, while the muriatic (hydrochloric) acid started at about .60v and rapidly dropped into a negative voltage. So if acidity is not an indicator of a good electrolyte, what is?


texts: π-ligands in trigonal prismatic complexes

texts:
We recently had a discussion here about the symmetry problems for the often postulated s- and p-mixing with the d-orbitals in complexes to somehow allow a d-d-transition. It was pointed out back then that the s- and p-orbitals of the ligands do not possess the $t_2$ symmetry, which is required to mix with the $t_2g$-orbitals in an octahedral geometry.

I looked for some literature but could not find much. The only answer I came up with was that this was only true for pure σ-ligands, because at least the π*-orbital has the $t_2$ symmetry. That is why only π-type ligands influence the ligand field splitting on the side of the $t_2g$.

I think it was Mingos who wrote in his new book that you can predict this by looking at the dual body of your coordination geometry and only if the dual contains triangular faces it will leave no non-boding orbitals. I will finish that sentence with 'in a pure σ-complex' (I guess this is what he wanted to say).

So the dual body of the triangular prism is the triangular bipyramid. So this should leave no non-boding orbitals. And I also checked the character table for the corresponding point-group, all d-ortbials find a symmetric partner in the s- and p-orbitals of the ligands (if I'm not mistaking). So this leaves me with the question, whether π-donor/acceptor ligands have any influence on the ligand field splitting?

This should not be the case here, so for all ligands it's basically up to the electronegativity in the end?

EDIT: I checked it again and just saw that I jumped one row I think, it seems like the $d_xy$ and $d_yz$ orbitals can only be represented by the π-ligands.


texts: Is iron(III)nitrate changed and if so how?

texts:
We have the solution:

$\ce{Fe^3+(aq) + SCN-(aq) <=>Fe(SCN)^2+}$

When we add more $\ce {SCN-}$ to the solution above, the solution produces more product.

My question is, how does it affect $\ce {Fe^3+}$? Do the concentration of iron(III)nitrate change or something?


texts: A more efficient method for electrolysis?

texts: If you made the anode and cathode both out of a single piece of zeolite that has been coated inside with graphite (or graphene) wouldn’t that provide a conductive path and greater surface area thus making electrolysis of water more efficient?


texts:
I just started learning about proton NMR.
According to Molbase, the HNMR data for tert-amyl alcohol (2-methylbutan-1-ol) shows four kinds of protons at 0.9 ppm, 1.24 ppm, 1.44, and 3.65 ppm.

However, it seems contradictory to what I learnt, since the protons on secondary carbon (1.44 ppm) are downfield to the protons on tertiary carbon (1.24 ppm), which confuses me, since I learnt that protons on tertiary carbons experience more de-shielding.
Is there something I have missed out in my thought process?
EDIT: Thanks to @orthocresol and @Buttonwood for pointing out my error. My revised question would then be:
Between the two types of protons on secondary carbons (1.24 and 1.44 ppm), why is it that the one at 1.44 ppm is more deshielded?
From what I understand, it is because carbon is more electronegative than hydrogen, therefore causing the deshielding effect, but at the same time from organic chemistry I learnt that alkyl groups are electron donating, which should cause shielding. Is there some misconception in my thinking?


texts: How to calculate the concentration after a certain timespan from the specific reaction constant?

texts:
A container at $30~^\circ\pu{C}$ contains $\ce{HNC_{(g)}}$ reacting to form $\ce{HCN_{(g)}}$. Knowing that the specific reaction constant is $4.4\cdot10^{-4}~\pu{s-1}$ and that you initially have $\pu{1 g}$ of $\ce{HNC}$: how many moles of each gas are in the container after one hour and a half?

I'm pretty sure that the reaction is reversible here. However, I have no idea how to calculate how many moles of each gas will there be after $\pu{1.5 hrs}$ (even if it was not reversible).
I have many doubts:

Did they skip the concentration because there's only one reactant?
Does $K$ take into account the $30~^\circ\pu{C}$?
What's the equation for "change of concentration over time" here?
How can I figure out how many moles of $\ce{HNC}$ and $\ce{HCN}$ the container will have after 90 minutes, ignoring the fact that it's a reversible reaction?


texts: Simulation of electronic potential from nanoparticles interacting with molecules

texts:
I work with SERS, where the Raman signal gets enhanced by the electric field of the nanoparticles. Now I like to simulate this kind of spectrum with Gaussian. I found a paper[1], where it looks very nice how they simulate it. They don't get a bond between the molecule and the silver nanoparticle. If I try it on my own, then the nanoparticles are thrown away by Gaussian.
Has anyone of you an idea of how they simulate it? My idea is the following workflow: Frist, they optimize the attached molecule alone; after this, they made a scan with one variable. The variable is the distance between the part of the molecule where the nanoparticle should attach and the nanoparticle itself. And after this, they put the nanoparticle in the distance with the lowest energy and make a single point calculation with options to get the orbitals and the ESP mapping. It makes sense, or is it not an ordinary workflow for gaussian? I learned Gaussian myself self so I'm not sure at all.
[1] Gao, Y.; Xu, M.-L.; Xiong, J. J. Environ. Sci. Heal. Part B 2019, 54, 665-675
Additional Information:
This is my route section: #p opt=vtight int=ultrafine oniom(PW6B95D3/aug-cc-pvtz:b3lyp/lanl2dz) nosymm geom=connectivity
I used the OMNIC layer model and used the high layer for the molecule with PW6B95D3/aug-cc-pvtz and the low layer for the gold atom with b3lyp/lanl2dz. I have no idea how to fix the gold atom in a specific region.


texts: Why does aluminum have a lower first ionization energy than magnesium?

texts: I used to use the explanation that $s$ orbitals penetrate better than $p$ orbitals, however, could the explanation be that $3s$ is shielding the $3p$ in aluminum?


texts: In the gold foil experiment why didn't thallium form?

texts:
When alpha particles hit the gold nucleus shouldn't they form thallium.
More over shouldn't it also ionize the gold or any atom it hits how does it remain unchanged unionized?


texts: Why do noble gases like Xe and Kr form compounds, despite offending the octet rule?

texts: According to the octet rule noble gases should not form compounds but xenon and krypton form compounds like $\ce{XeF2}$, $\ce{XeF4}$, $\ce{XeOF2}$ and $\ce{KrF2}$ respectively. Why?


texts: Why does the equilibrium constant depend on the temperature but not on pressure and concentration?

texts: According to my textbook (and intuitively) certain changes when the aforementioned 3 variables are altered occur in accordance with Le Chatelier's Principle. However, what I don't understand is what makes temperature change alter the equilibrium constant while the other two do not. All three cause changes in the equilibrium position (the state of concentrations at which equilibrium is achieved with lowest possible stress in the system), so why don't they all also change $K_{eq}$?


texts: How to get the SMILES from structure without software?

texts: Usually I use online programs and structure drawing tools to find the SMILES of a compound. How to find the SMILES without software? Where to find resources to learn it?


texts: Oxidation of Carbon atom in Alkene, Alkyne and Alkanes of functional groups?

texts:
Nomenclature priorities are in order of the degree of oxidation of the
  carbon atom.

I am not sure if it's advisable to just take it as it is and use it or try to understand the basis of the functional group prioritization. I guess the latter interest me. So looking at the priorities for functional groups,

Alkene has higher priority than Alkyne and followed by Alkane. I started reading some materials about Oxidative Cleavage of Double Bonds and rest of the reactions, which kinda went way over my head.

Can someone explain, how and why the carbon oxidation in Alkynes are lower than Alknenes? Or put in another word, why would Alkene carbon oxidate faster than Alknenes?


texts: Alkylation of enolates using tertiary halide

texts: I was recently studying the alpha alkylation of enolates using LDA followed by subsequent treatment with primary halides to give the product.I was wondering what happens with teritary halides. My guess is that elimination will take place,and the carbon nucleophile formed by LDA will abstract a proton fron the tertiary halide giving an alkene. Is this chain of reasoning correct?


texts: Is the reaction of calcium carbide with water a Brønsted-Lowry acid-base reaction or Lewis acid-base reaction?

texts:
Consider the following reaction:

$$\ce{CaC2 + 2H2O -> Ca(OH)2 + 2C_{2}H_{2}}$$

If it can be considered as an acid-base reaction, is it a Brønsted-Lowry (B.L.) reaction or a Lewis reaction?

If it is B.L., of course it is also Lewis; but I cannot understand if it can be B.L. in this case, since 2 protons are actually passed to the double carbon atom, but there is also the $\ce{Ca}$.


texts: IUPAC names accidentally differing in hyphen only

texts:
Here is an example of two compounds

  $$\ce{CH3CH2COOCH3}$$
  vs
  $$\ce{(CH3)2CHCOO-}$$

i.e.

  vs

whose possible IUPAC names

  methyl propanoate
  vs
  methylpropanoate

accidentally differ only in presence/absence of a space. (Note that complete, unambiguous name of the second compound is 2-methylpropanoate)

Is there an (accidental) example of two IUPAC names for different compounds, that differ only in presence/absence of a hyphen ("-") instead?

(Question might sound hypothetical, strange and inappropriate, but is related to to this one)

UPDATE: Mentioned ‘methylpropanoate’ preferred IUPAC name is 2-methylpropanoate. There's a better example pair:

phenyl acetate ($\ce{CH3COOPh}$)
phenylacetate ($\ce{PhCH2COO^{-}}$)

Note that in some language localized official IUPAC nomenclatures, the names really differ by the hyphen instead of the space (e.g. in Czech: fenyl-acetát vs fenylacetát), but I was wondering about the English nomenclature.


texts: What acids, solvents is lithium-6 fluoride soluble in (other than HF)?

texts: $\ce{LiF}$ is quite insoluble in water, and I'm trying to use some water-soluble acid or solvent to dissolve $\ce{^6LiF}$ (95% enriched) in. I'm not a chemistry person, I'm a radiation detection person, and I have very little idea of chemistry. Could anyone please help?


texts: Is the energy of the orbital an electron "resides" in, considered to be a factor of that electrons ionization energy?

texts:
The answers to a Quora question mainly refer to the factors as generally being, the electrostatic forces of attraction between the electron and the positively charged nucleus and all other events, by which this force is affected, i.e. atomic size (distance of the electron from the nucleus), the penetration effect, the shielding effect (by inner electrons) and the spin-pair repulsion phenomenon.

My textbooks also mention that electrons in the same shell have a "reasonably constant" distance from the nucleus, leading to the key factor of the observed progressive pattern down a period being due to the increase in atomic charge.

I get all that, but what I fail to understand is why none of these sources mention the energy of the electron's resident orbitals. It's my understanding that when an electron is "plucked" from the atom by means of the ionization energy value, or put into orbit by that value, they do so from their orbitals/subshells.

Now, each of these subshells have a different integer value of energy which increases up the count. I also concur that these orbitals have differing forces of attraction acting on them from the nucleus due to distance, inner electrons and the electrons proximity to the nucleus leading to different values of Ionization energy for the electrons "in" them, but I find it difficult to grasp that all electrons in the same shell have similar "distances". In one shell, for instance $n = 3$, there are 3 subshells each of which have a different three dimensional geometry and hence distance from the nucleus. The electrons in these subshells also have different amounts of energy which is what I'm asking about.

Don't these different energy values play a part in their ionization energy? i.e. can't the lower ionization energy of electrons in further subshells be explained by the higher potential energy of that subshell, as the higher the energy the lower the value of ionization energy?

Can't the energy of the orbital an electron resides in, be considered to be a factor of its ionization energy?


texts: On adding sugar to water, does the entropy increase or decrease?

texts: This question is a little confusing. According to my teacher, the entropy should decrease, but I think that sugar is crystalline first and later it dissolves, so the randomness increases and so the entropy should also increase. What is the correct answer?


texts: Minimum amount of water in pressure cooker

texts:
When cooking I would like to know the minimum amount of water I can add to my 6.2 L pressure cooker, worst case, so without any food. At second ring cooking the pressure is 0.8 bar.

I assume I need to solve $pV = nRT$ and know the density of water vapour at 0.8 bar, but that introduces $m = \rho V$, where I suppose $m$ and $V$ are unknowns?

Question

My high school chemistry is really rusty. Can someone help me in the right direction, and perhaps also tell if it at all something that can be solved without knowing the temperature?


texts: How to change CO₂ to a less polluting gas?

texts:
I want to change $\ce{CO2}$ coming out of the tailpipe of a car to some other compound that is considerably less harmful to the environment with a filter of some sort.

What are some ways that this is possible?

$\ce{CO2}$ to carbon and oxygen?


texts:
I came upon the following statement in a true/false question:

  Glycine can be esterified by an alcohol in the presence of inorganic acid

Is this statement correct?

Glycine contains the basic $\ce{-NH2}$ group, which would get protonated in the presence of inorganic acid. As a consequence, would the esterification process still be carried out on the $\ce{-COOH}$ group? This paper says that the reaction needs trimethylchlorosilane as a catalyst and not an inorganic acid.


texts: Considering the IUPAC rules state that you cannot extend the main chain and that carbon can only have 4 bonds, there is only one way to have two methyl groups on a but-2-ene. Therefore, why do we still keep the '2,3'?


texts:
I was at a chemistry competition, and one of the questions they asked was on Berry pseudorotation

Now the question gave 4 molecules, namely, $\ce{IF5, PF5, PCl5, and XeF5-}$, and asked which of these molecules is unable to undergo Berry pseudorotation. I immediately eliminated $\ce{PF5 and PCl5}$ as they have trigonal bipyramidal structure, so that left me with the other two molecules.

At this point, I am unable to determine which of the remaining molecules should be the answer, so I take a guess and select $\ce{IF5}$, as my reasoning is that it has lone pairs so it is unable to interconvert. (However this also could be used to explain for why $\ce{XeF5-}$ is a possible answer too)

After reading the Wikipedia article above, it turns out $\ce{IF5}$ is able to undergo such pseudorotation, which leaves me surprised, but in that case, could someone explain why $\ce{XeF5-}$, as opposed to $\ce{IF5}$, is unable to undergo such rotation? (I think it has something to do with the lone pairs on $\ce{XeF5-}$, but I'm not sure)


texts:
I was told that dd-water will superheat when heated up in a microwave because of a lack of ions.

1) Doesn't water auto-ionize? I asked this; the answer was it auto-ionizes "too slowly" in dd-water to prevent superheating.

2) This begs the question: what are the kinetics of the auto-ionization of water? What's the rate?

3) This also begs the question - what is superheating? What does ions have anything to do with superheating?


texts: Need help interpreting this data table (provided below)

texts: I am confused about this data table. Can someone please explain how this person got a linear alkanes of differing molar masses? (I know some basics of organic chemistry, but I'm still learning.) Are there differing compounds to each of the ones listed underneath Boiling Point? If so, where can I learn these compounds or is there a database that has a list of compounds under each one?


texts: What is the minimum thickness for stainless steel crucible to melt aluminum

texts:
I am planning to make a stainless steel crucible (air-tight) to melt aluminum. Aluminum is known to oxidize in presence of air. I therefore want to create a custom crucible made with sheet metal stainless steel. What is the recommended thickness of sheetmetal in this case?
I shall be cladding the crucible with refractory material to ensure no heat losses from the stainless steel crucible. The crucible shall hold roughly 10-15kg of Aluminum. As per the comments I yet have to see now to have the crucible vacuumed to ensure no gasses are present or employing a one way valse, so that it doesn't become a dangerous to operate.


texts: Karl Fischer Titration simple explanation

texts:
I'm looking for a simple explanation how the Karl Fischer method to determine the content of water works. I'm not a chemist but an engineer from an electronic-physical field and my chemistry courses are a while ago, meanwhile. That's why I can't understand what's going on but I don't really need a detail explanation, just low-level enough that I can say "Yep, makes sense" and high-level enough, that I can understand it.
Hence, could someone please describe roughly what's going on?


texts: Can activated charcoal be used to filter bacteria out of air?

texts: As the title says: Can activated charcoal be used to filter bacteria out of air and or gas?


texts: Why do neutral metal atoms have affinity towards electrons?

texts:
Since first electron affinity is almost always negative, neutral atoms of most elements (including metals) must have an affinity towards electron. But shouldn't metals want to lose electron(s) rather than having an affinity towards it?
Take lithium for example. It can attain noble gas configuration as it loses an electron. But first electron affinity of lithium is -60 KJ/mol. So, it has an affinity towards electron although it wants to lose one. But wasn't it supposed to have a positive electron affinity?


texts: In electroplating, can a galvanic cell substitute the direct current supply? The process is to change iron metal to a silver one, but a galvanic cell is connected to the two electrodes.


texts: Why is ammonia so much more basic than water?

texts: The only reason I can think of is that the lone pairs in the oxygen in water are in lower energy orbital relative to the nitrogen in ammonia due to increased effective nuclear charge in oxygen. However, as far as I am aware, ammonia is SIGNIFICANTLY more basic than water. Surely the orbital energy cannot account for this.


texts: How much copper powder dispersed into 2 liters of water will result in a 10 ppm concentration? I am not a chemist.


texts: Explanation for why nickel turns green in hydrochloric acid

texts:
My daughter has a chemistry test that I am helping her prepare for. One question is

  Nickel sulfate, $\ce{NiSO4(aq)}$ is a green solution. Nickel chloride, $\ce{NiCl2(aq)},$ is a yellow solution. If you add nickel, $\ce{Ni(s)},$ to hydrochloric acid, $\ce{HCl(aq)},$ what color solution do you expect?

Wikipedia states that it will turn green but doesn't give an explanation for why. Can anyone fill in the blanks for us? (This is for high school intro to chem so try to keep it at that level.)


texts:
Would a [2]catenate whose each ring consist of a different number of methylene groups only, be optically active if one hydrogen atom of a random methylene group is replaced with e.g. chlorine? I think yes, but I need a second opinion.

The compounds attached seem to be enantiomers. I don't see how, by rotation, they could be super-imposable.


texts:
[EDITED]

If humans disappeared today, and aliens visited in the future, for how long would plastic or other "obviously" non-natural polymers be detectable on the planet, using known or plausible technology. That is, how likely would it be that the aliens would say: "Clearly, the presence of these molecules indicates past technological activity"?

I'm mostly interested in accidental preservation of plastic (buried in sediment, microplastics in the ocean, etc.), but also the long-term stability if, for instance, someone intentionally tried to preserve a plastic artifact. Could it survive for thousands of years if adequately protected? Millions? Billions?

Comments imply that if isolated from biological activity, at least some plastics are sufficiently stable to survive for billions of years (I assume that requires temps below, say, 40C or so?).  Is it plausible for plastic to end up in an arid region, get buried in sediment, and survive for millions of years intact while getting buried under successive layers?  At what pressure would the plastics degrade and no longer be recognizable as the product of technology?  I assume this would occur well before it turns into coal.

Finally, while I recognize that this is the Chemistry SE and not Biology, are all plastic species today degradable by some known biological organism (meaning, for each specie, does there exist a known bacterium that eats it)?  Is there a reason that life would not eventually adapt a way to "eat" every kind of plastic/polymer we produce (like, not enough energy to recover, etc.)?

Note: I have basically a high-school level understanding of chemistry, so apologies for the ill-posed question.


texts: I was told that the more exothermic the solution, the more soluble the salt. Is this statement wrong?

texts:
I was also told that $$\Delta H(\text{solution}) = \Delta H(\text{hydration}) - \Delta H(\text{lattice E})$$

However, for $\Delta H(\text{solution})$ to be exothermic, it has to have a negative value <0. Which means lattice energy is going to have to be greater than $\Delta H(\text{solution})$ to produce a negative value, based on the equation above.

Yet I am also told that hydration energy released needs to be enough to compensate for the lattice energy required to break down the solid. So it can't be lesser than $\Delta H(\text{lattice E})$.

Isn't this contradictory? I am confused.

I have read a similar question at   Enthalpy of solution
but the answer given is that dissolving is dependent on Gibb's free energy instead.
Does that mean that I should disregard the statement "the more exothermic the solution, the more soluble the salt."?


texts: Why does 1,4-diiodobenzene have a non-zero dipole moment?

texts:
From this answer, I came to know that 1,4-diiodobenzene has a dipole moment of $0.19~\rm D$ in benzene at $20\ ^\circ\rm C$. On the basis of symmetry, I'd expect the bond moments due to the difference in electronegativities of iodine and carbon atoms to cancel each other out, similar to other 1,4-dihalobenzenes. However, it turns out to be non-zero. What is the reason for this observation?
I asked the same question in the comments, and I was suggested that this could be due to the high polarizability of the large iodine atoms. I can understand this reason since this is how books explain the increase in boiling point of alkanes with increase in chain length. And in this case, the boiling point of 1,4-diiodobenzne ($285.0\ ^\circ\rm C$) is higher than 1,4-dibromobenzene ($218.5\ ^\circ\rm C$). But this is the first time I'm seeing that dipole moment is altered by dispersion forces and I'm also confused by the issues described below.
We know that dipole moment $\vec{p}$ of a charge distribution is given by:
$$\vec{p} = \sum_i q_i \vec{r_i}$$
where $q_i$ and $\vec{r_i}$ are the charge and position vector of the $i$th charge about a particular origin. If it's the dispersion forces, arising due to the lack of symmetry of the fluctuating electron cloud, how can we ascertain a particular value of dipole moment as both $q_i$ and $\vec{r_i}$ are indeterminate?


texts: Radial pair distribution function (VMD). How to define it for a water NaCl system with multiple Na and Cl?

texts:
I'm struggling to understand a paper in which someone has presented radial distribution functions (RDFs) for a system that contains multiple Na, Cl, and water atoms/molecules.  I don't know exactly how the RDFs have been calculated--there must be some standard method.

I'm a newbie to molecular dynamics and have run my own simulations.  I would like to compare my RDFs to the ones in the paper.  However, I am not sure that I understand RDFs.  One reason I'm worried is that I keep receiving an error when I try to plot my own RDFs using the software, VMD.  The error is something like "cannot measure RDF."  It is either a bug in VMD or a conceptual misunderstanding on my part.  I don't know exactly how VMD calculates an RDF.

Let's say we have an RDF from Na to Cl in my system that contains multiple Na and Cl. Is it correct that an RDF is based on an average of what ALL Cl atoms are doing in relation to ALL Na atoms?  Or do I have to somehow define pairs of Na and Cl (I don't have these--they're all far apart in my system) and create RDFs for each pair?

I'm not sure whether "Chemistry" is the right StackExchange section for this question.  If it isn't and anyone has any advice on a more appropriate section, I'd be very grateful.  Thank you.


texts:
(Callen 9.7-2)

The phase diagram of a solution of A in B, at a pressure of 1 atm, has a coexistence region in the $(X,T)$ plane (e.g., $X_A$ is a liquid molar fraction with $N=N_A+N_B$ and T temperature and $Y_A$ is a gas molar fraction). The upper bounding curve of the two phase region can be represented by

$T=T_0-(T_0-T_1)Y_A^2$

and the lower bounding curve of the two-phase region is represented by

$T=T_0-(T_0-T_1)X_A(2-X_A)$

Show that if a small fraction of the liquid $−dN/N$ is boiled off, the change in the fraction of the remaining liquid is,

$dX_A =-\left[(2X_A-X_A^2)^{\frac{1}{2}}-X_A \right]\frac{-dN}{N}$.

All I knew was that $dX_A$ could be obtained from $dN = dN_A+dN_B$

and from there

$dN_A+dN_B = N dX_A + X_A dN + N dX_B + X_B dN$... I previously found that, when temperature is such that $X_A=X_B=1/2$, $Y_A=0.8660$...


texts: Each goes through a carbocation intermediate which is enormously reactive so what would promote attack towards a proton (E1) rather than towards the carbocation for substitution. Besides an increase in temperature I can't think of much.


texts: reference or data on internal hydrogen bond strength

texts:
As suggested by the title, I am looking for data on the strength of different internal hydrogen bond configurations. In general, an internal hydrogen bond may form when the donor and acceptor are separated by 3-5 bonds thus forming rings of size 5-7. Below is a picture of the basic examples.

This is an oversimplification that is most relevant to small molecules (not proteins, etc). I'm sure there are situations where other conformational considerations make internal hydrogen bonds of other lengths possible.

At any rate, I am looking for some quantitative data regarding the strength of internal hydrogen bonds of different path distances. This means the same donor and acceptor atom types separated by varying distances like in the picture above. In general I would like to know how much more stable the path 4 configuration is compared to the path 3 and path 5.


texts: How to safely change the color of a fire tornado?

texts:
So I've been watching a lot of fire tornado videos and I came across one that had a reasonable and safe setup (around the 3:23 mark):

Fire Tornado DIY

Is there a way to change the color of the fire tornado using the butane-powered base option?

The initial display of the tealight allows for either powdered/liquid chemicals to be added, but how would one safely add chemicals such as alcohol with the butane base setup?


texts: How to separate HCl and NaOH from salt and water solution?

texts:
I mean, how can we reverse the neutralization reaction of $\ce{HCl}$ and $\ce{NaOH}$ to get back $\ce{HCl}$ and $\ce{NaOH}$.

I want to extract $\ce{HCl}$ and $\ce{NaOH}$ from a mixture of common salt and distilled water in equal proportions at home.

Basically, how can I make this reaction happen?

$$\ce{H2O + NaCl -> HCl + NaOH}$$

What temperature or pressure conditions are required?
Also, would the extracted components be pure? (I know common salt contains iodine and even distilled water is not pure, that's why I am asking this.)


texts: Book recommendations for protein structure refinement

texts: I’m an undergraduate Chemistry student and I’m currently writing my dissertation about semi-empirical methods, particularly PM7, applied to protein structure refinement from X-ray structure. Could you recommend me any book/article about it?


texts: Is the negative excess volume of ethanol/water the cause of my math error?

texts:
I have a binary mixture, say ethanol at $90\%wt$ ethanol, $10\%wt$ water.  According to Perry's Chemical Engineers' Handbook 9th Ed., that mixture has a density of $0.81797g/cc$ (at $20^{\circ}C$).  So my $1L$ of mixture should have a mass of $817.97g$.

Now, I want to create this mixture.  I know the total mass and the mass %'s, so I just multiply them out: we find that we need $736.17g$ ethanol and $81.80g$ water.  Ok, so far so good.  However, say all of my balances are broken, so I only have graduated cylinders to work with.  Easy, just convert those masses back to volumes using their respective pure substance densities: $0.78934g/cc$ for ethanol and $0.99823g/cc$ for water.

However, doing this tells me that I should have $932.6mL$ of ethanol and $81.9mL$ of water, which adds up to a total volume of $1014.6mL$ of binary mixture, so somehow I magicked $14.6mL$ of liquid out of thin air using this conversion algorithm.

Is this due to the negative excess volume of the ethanol/water mixture upon mixing?  That's my current guess, but for the life of me I'm having a hard time figuring out the math here.  It seems like the change in volume should be much smaller: $10\%wt$ water in ethanol is about $10\%mol$ and there's about $4.5mol$ of water in the mixture, so based on this dataset it seems like there should only be a difference of about $3mL$.  Even with all the rounding I just did, it seems like this can't be the only error source.

Is there something wrong with the logic of my algorithm here?  Can anyone point me to the reason I'm seeing this numerical error whenever I run this calculation?


texts: The structure of 1-(butan-2-yl)-4-tert-butylbenzene is displayed below. What is -yl on this compound and when do I use it?

texts: I can't figure out how to use -yl on organic nomenclature and how do I use it in nomenclature. Please explain everything about the use of -yl in nomenclature.


texts: What is the difference between an analytical standard and a certified reference material?

texts: I am analysing the analytical standard market, but every time I try to understand what an analytical standard is, I only get the definition of a certified reference material. Is there a difference?


texts: Why do we write electrode potentials next to chemical reactions?

texts:
We might have a half cell consisting of the redox couple $\ce{Ag+}/\ce{Ag}$, which for example's sake might be fixed to be at the cathode (i.e. undergoing reduction).

The reaction at the cathode is then

$$\ce{Ag+ + e- -> Ag}$$

The standard electrode potential of the $\ce{Ag+}/\ce{Ag}$ couple is $+0.80\ \mathrm V$ with respect to SHE. I've seen the above reaction written as such:

$$\ce{Ag+ + e- <=> Ag} \quad E = +0.80\ \mathrm V$$

I'm confused as to why we write this electrode potential next to the reaction, considering that the electrode potential of a redox couple is reasonably disjoint to the concept of the chemical reaction. Although, at the end of the day, the chemical reaction results in the interfacial potential difference which causes the electrode potential, $E$ is a property of the electrode, not the chemical reaction.

Is it perhaps just because we want to write the equation of the reaction occurring at a certain electrode and the electrode potential of the electrode on the same line?

I'm aware that for associating potentials with written reactions, there exist two different conventions: European, where all reactions are labelled with the reduction potentials of the couple, and American, where oxidation reactions are labelled with the oxidation potentials of the redox couple and likewise reductions with reduction potentials. However, my question is why we need to attach the electrode potential to the chemical reaction in the first place!

That is, ultimately, aren't redox potentials associated with redox couples/electrodes, not reactions?


texts: Is coupling reaction performed in acidic or basic medium?

texts:
Why is coupling reaction between aryldiazonium chloride and aniline carried out in a mild basic medium and not under acidic medium?
According to me, it can be performed in both mediums.


texts: Can pi backdonation occur on non-metal centers?

texts:
The common example of back-donation is the interaction of a CO molecule with a metal center (d-orbitals) on a surface.

Can a similar mechanism occur between CO and a non-metal center, like oxygen on a surface (like in an oxide)? Can the p-orbitals of the surface oxygen be involved in such an interaction?


texts: In terms of nomenclature, is there a difference between RCHO and RCOH when referring to an aldehyde?


texts: Order of Reaction differs in equation and linearisation

texts:
I have given the following equation: $A + 2B \rightarrow C$

$ v = –k\cdot [A]\cdot[B]^2$

gives me the orders 1 for A and 2 for B. That results in a total order of the reaction of 3.
So far so good. But I have given the following plot for linearization:

But this linearization with $\frac{1}{[A]}$ defines a 2nd Order for A, not 1st.

The question is what does this mean for the given equation? And in which sequence could steps of the reaction occur?


texts: Increasing the length of a carbon chain in an alkane

texts:
What would be the best reaction to increase the carbon chain length in an alkane? Preferably, it would be by one at a time; however, if that is not possible, just generally increasing the total length of the carbon chain (such as producing pentane from propane) would be fine.

Moreover, is there a way that I can add a methyl group to a compound in the form $\ce{R-CH3}$?


texts: How is "the surrounding" and its temperature defined to calculate entropy change during a reaction?

texts:
Lets say supercooled liquid water at $263\ \mathrm K$ isobarically changes to solid ice at the same temperature. I wish to calculate the change in entropy of the surroundings and I happen to know the $\Delta H$ for the reaction.

This should be simple enough. Since the process is isobaric, $q_\text{rev} = \Delta H$ and $q_\text{surr}=-q_\text{reac}$

$\Delta S_\text{surr} = \frac{-\Delta H}{T} $

But what should T be here? Is it $263\ \mathrm K$? Or the temperature of the surroundings? Or are they both the same, ie;

Do we consider the temperature at which the reaction is taking place to be the temperature of the surroundings as well?

If so, why?


texts: Energy required to remove an electron from He

texts:
The energy required to remove both electrons from the helium atom in its ground state is $79.0\;\mathrm{eV}$. The energy required to ionize helium (i.e. to remove one electron) is -

  (A)   $24.6\;\mathrm{eV}$

  (B)   $39.5\;\mathrm{eV}$

  (C)   $51.8\;\mathrm{eV}$

  (D)   $54.4\;\mathrm{eV}$

My thoughts: What I actually did was to take half of the given energy value since energy required to remove electrons depends only on the principal quantum number(and also on atomic number). But, I found my answer to be wrong.

On the other hand just calculating the energy required to remove one electron from $n=1$ state gives the correct answer. Why is it so?


texts: Is lead (Pb) radioactive? I have heard about it being radioactive but have also heard it referred to as the heaviest stable element. Radioactivity refers to release of alpha, beta, gamma rays.


texts: What prevents the anode from corroding in electrolytic organic reactions?

texts:
An electrode can be plated by having a solution full of electrolyte, using the the metal that will receive the plating as the cathode, and the metal doing the plating as the anode. Current is put through the cell and the anode dissolves oxidized metal ions into the solution, which gravitate over to the cathode, and then "plate" onto the cathode.

My question is, what prevents this process from happening when doing an electrolytic organic reduction or oxidation? Imagine you plate an electrode with a specific metal to be used as an anode in a different reaction, what prevents that anode from immediately corroding and having the metal ions fall off into the solution when current is applied? Does the presence of an organic species to be reduced/oxidized take priority over the anode corrosion, thus preventing it?


texts: is there a database of known chemical reactions?

texts: I am looking for a complete directory of chemical reactions. It should be searchable by element or substance and also the various factors (pressure, temperature, catalyst, etc) should be mentioned. Is there something like this? Thanks!


texts: Better understanding the pyrolysis reaction

texts:
I'm no chemist, but much of my work revolves around biochar.  I've always understood it with the following rough approximation:

$$
\ce{CH2O (dry plant matter) + heat -> black carbon + H2 + CO + CH4 + hydrocarbons}
$$

I've got two questions:

Is the above a decent approximation?  In what ways is it misleading (as all approximations always are)?
A colleague recently told me that methane is only formed in this reaction when there is water vapor present -- he said that it mixes with CO at high temperature to form the methane.  Is this true?  Will one not get any methane from oven-dried biomass that is exposed to heat in the absence of oxygen?


texts: What is the highest possible effective nuclear charge as a percentage of nuclear charge an electron in any neutral atom can experience?

texts:
I was wondering about the following statement "The higher the principal quantum number of the orbital the electron is in, the lower the nuclear charge it experiences." I then argued that this statement is false because when an atom has more electrons, it also has more protons and as the orbitals become more diffuse, the attraction of the protons would significantly outweigh inter-electronic repulsion at higher atomic numbers.

This led me to think about the following question: What is the highest possible (nuclear charge an electron can experience divided by the nuclear charge of the atom)? My guess is that this electron would certainly belong to one of the more diffuse subshells. (i.e. d or f)

Please note that the quantity I am looking at is not effective nuclear charge but it is the effective nuclear charge divided by the nuclear charge.


texts:
Will the following reaction give a racemic mixture or not?

According to me, it should give. But my teacher disagrees, but I cannot understand the reasons he gave. Shouldn't there be equal approaches from above and below the molecules?

I am confused when he says that the adjacent 3° Carbon can change its configuration too.

Update

Original question:-

Solution provided:-


texts: Oxidizing agent, reducing agent, acid or base

texts:
In concrete reactions, how can you define whether Ammonia reacts as an oxidizing agent, reducing agent, an acid or a base? I'm confused because in the examples given it's not an acid/ base when an $\ce {H+}$ is donated/ accepted.

$$\ce {2NH3 + 3Cl2 -> N2 + 6HCl}$$ (oxidizing agent)

$$\ce {Na + NH3 -> NaNH2 + \frac{1}{2}H2}$$ (reducing agent)

$$\ce{NH3 + H2O + CO2 -> NH4HCO3}$$ (base)

$$\ce{NH3 + LiCH3 -> LiNH2 + CH4}$$ (acid)


texts: Does a salt always have a neutral charge?

texts:
I know that a salt is the product of a reaction between a base and an acid, but does this mean that there will always be one cation and one anion and therefore a neutral charge?

In relation, are acids and bases charged?


texts: Ideal gas Law best describes the properties of which of the following gases at 0 degrees Celsius and 1 atm?

texts:
a. $\ce{PH3}$

b. $\ce{HBr}$

c. $\ce{SO2}$

d. $\ce{N2}$

I believe that it is $\ce{N2}$, but I'm not too sure, since technically all of them would act the same at STP.


texts: How does the wax layer of a leaf get damaged by acid rain?

texts: I know that wax is not soluble in water so I think it doesn't react with or dissolve in water-based solvent. Some sources I have consulted say that it does react but slowly. So getting confused by different opinion, I have no idea what the truth is.


texts: Modeling 3-center-2-electron bonds in Avogadro

texts:
Is it possible to model 3-center-2-electron bonds in Avogadro?

It seems to allow users to add however many bonds they would like to an atom, but I can't seem to find documentation on whether this is valid.  When modeling $\ce{B2H6}$, for example, I can draw a $\ce{B-H-B}$ bond, but does Avogadro understand that this is a bridge bond?

For example, below is an $\ce{(AlH3)5}$ cluster I modeled in Avogadro. Two pairs of bridge bonds appear merged after UFF optimization, which doesn't seem right. This is what led me to wonder if modeling the bridge bonds the way I did was incorrect.


texts: chemical equilibrium and exothermic reaction

texts:
here is an interesting question about the chemical equilibrium and Le Chatelier's principle.

the following pressure show the partial that produced in the equilibrium reaction at time (t1 and t2)

$$\ce{N2 + 3H2 <=> 2NH3 \Delta H =-92 KJ}$$

at point t1 hydrogen is added to the previous equilibrium system at this point on the curve and after a period a new equilibrium state took place at point t2
so
A = ...
B = ...
C = ...

what i say is the answer is A=H2 ,B=N2 and C=NH3
becuase by adding more hydtogen thus increasing the conc. the reaction will move forward so the temp will increase increasing the pressure according to The Pressure Temperature Law so the the pressure of N2 increases but again also the pressure of NH3 should increase because the no of moles will increase as the reaction will shift forward so I am lost here


texts: Why must a buffer solution contain both a weak acid and a salt solution of its conjugate base?

texts:
Doesn’t the weak acid dissociate to produce the conjugate base on its own?

I understand that when a strong base is added to the buffer solution, the hydroxide ions will react with the hydrogen ions formed via the dissociation of the weak acid. The equilibrium position will shift rightwards to replenish these hydrogen ions, ensuring that few hydroxide ions remain in the solution.

Conversely, when a strong acid is added to the buffer solution, the hydrogen ions will react with the conjugate base to form the weak acid molecule, thereby ensuring that most of the additional hydrogen ions are removed from the solution, and the pH of the solution remains stable. In the literature I’ve been reading so far, it is mentioned that a salt solution containing the conjugate base ensures that there is a continuous supply of the ions, but can’t the ions simply be replenished by the dissociation of more weak acid molecules, as in the previous case?


texts: Which metal bicarbonates do not exist in solid state?

texts:
$$\ce{(i) LiHCO_3       (ii) Ca(HCO_3)_2       (iii) Zn(HCO_3)_2      (iv) AgHCO_3}$$
From my prior knowledge compounds i and ii are not solids because of the high hydration energy of Li and the high polarizing power of Ca respectively. But the answer to this question includes both options iii and iv. Which property makes them not solid/exist in solution state?


texts: Specific heat for tetraatomic gas molecules

texts:
I came across a question which involved non linear tetra atomic gasses.
In it, the value of specific heat capacity at constant volume was given as
$9R,$ added up as

$$\frac 3 2 R + \frac 3 2 R + 6R = 9R$$

Now I know $6R$ is $C_V$ for triatomic gasses, but why do we add the two $\frac 3 2 R$ terms?

Also, how does being linear or non-linear affect the specific heat capacity of a gas?
Explanations with diagrams showing it in 3-D coordinate system would be helpful.


texts:
Given 10 mM potassium phosphate buffer (pH = 7.0), 50 mM potassium propionate and 20 mM EDTA (acid). After addition of all 3 components pH becomes 4 since EDTA has 4 $\ce{OH}$ groups.

How to calculate the ionic strength if I am pHing it with $\ce{KOH}$ up to 7.1?
I can calculate ionic strength for binary mixtures, but 4 different components makes me stuck.


texts: Is "stainless" a bulk or a surface property of stainless steel?

texts: In particular, if I cut a block of stainless steel in half, would the newly formed faces be stainless as well?


texts: Why did we multiply equilibrium constant with concentration of pure water and called it the water product?

texts: Equilibrium constant is calculated by taking active masses of pure liquids as unity. But while calculating ionic product of water we could have simply defined the equilibrium constant as water constant.


texts:
I should like to know roughly how the hormone melotonin is synthetically made for the pharmaceutical industry (i.e. not how it is made in living beings). I can't seem to find any reference to its manufacture on the web, it is seen to have a fairly simple structure on its Wiki page and biologically it is synthesised from the forerunner amino acid tryptophan. So I believe it is likely to be readily synthesised for use in pharmaceuticals without the use of animal products, but I cannot confirm this.

Specifically, a close relative of mine has been prescribed melotonin and I want to confirm that this substance is not made from animal products, as I live in a country where the authorities in their great wisdom have deregulated the food and meat processing industries. Astoundingly, they did this at exactly the same time that a UK royal commission recommended re-regulation of the same to prevent contamination of food and pharmaceuticals by the Creutzfeld-Jacob prion.


texts: Why this redox equation occurs on basic medium?

texts:
I have the following redox equation that I need to balance:

$$\ce{MnO4-(aq) + SO3^2-(aq) → MnO2(s) + SO4^2-(aq)}$$

The problem says that it happens on basic medium, but I don't see the $\ce{OH-}$ which I usually use to identify the basic medium.

How do I identify that this reaction happens on basic medium? Is it something that the problem should clarify?


texts: Equivalence point vs inflection point in the titration curve of a weak acid

texts:
Let's suppose we want to titrate a solution containing an unknown monoprotic and weak acid. We use a strong base, such as $\ce{NaOH}$. When the number (and moles) of hydroxide ions coming directly from the base is equal to the amount of hydronium ions due to the acid, here we have the equivalence point.

When titrating a strong monoprotic acid the equivalence points coincides with the inflection of the titration curve, and pH is seven.

In our case, however, the aqueous solution results to be slightly basic at the equivalence point. Therefore, does the inflection point on our curve still coincide with the equivalence point or it is to be found slightly before?

In other words, what does the inflection point indicate, that $\mathrm{pH}$ is seven (so the inflection is distinct but may coincide with the equivalence point, and shows where the rate of increase in $\mathrm{pH}$ is maximum) or the equivalence point itself?


texts: Why does hydrogen have a lower ionization energy than fluorine?

texts:
I found here that the ionization energy of hydrogen is $\pu{1312kJ/mol}$ and for fluorine, it is $\pu{1681kJ/mol}$. Now clearly, from the data, we can see that hydrogen has a lower ionization energy when compared to fluorine.

I did not expect this because I saw here that fluorine is twice as big as hydrogen (I am referring to the empirical values of the atomic radii). This means that it would be significantly easier to remove an electron from a fluorine atom than from a hydrogen atom. That's why I expected hydrogen to have a higher ionization energy. But I found that it's the other way round. Why is it so? What is wrong with my reasoning? Is this an exception?