texts: Why do we use molality on describing colligative property?

texts:
I'm satisfied with the explanation about Raoult's law that the chance of vaporizing will depend on the surface exposed to the atmosphere and solute will decrease such chance by taking portion of the surface at rate of $X_{solute}$.
However, incase of elevation and depression of boiling point, I can't find any explanation why it should depends on the molality. There's a molarity, molality, mole fraction, etc.. why molality among them?
I know that since it's microscopic, we can't be sure about anything since we cannot observe. But still I'm looking for some satisfactory explanation.
And below is the example of boiling-point-elevation equation that I made by looking at the graph of tripoint and considering the fact that boiling point elevation occurs due to the vapor pressure change. Why can't we use such method? it seems accurate to me though..
Let $$P(t):T \to P, when$$ $$t_{tri}<t, t \in T (temperature), t_{tri} \in T (temperature), p\in P(pressure)$$,
$$P^{-1}(p): P \to T $$ $$p_{tri}<p, t \in T (temperature), p_{tri} \in P (pressure), p\in P(pressure)$$
$p_{tri}, t_{tri}$ are pressure and temprature at tripoint $P, P^{-1}$ are function for solvent before dissolve.
According to the Raoult's law, we can calculate vapor pressure of solution's solvent $P_{2}(t)$ as such
$$P_{2}(t)=P(t)*X_{solvent}, X_{solvent}=mol_{solvent}/(mol_{solvent}+mol_{solute})$$
Let's say that we want to know the elevation of boiling point at pressure $P(t_0)$ when $t_0$ is former boiling point. According to the Raoult's law stated above, we can say that boiling point elevation $\Delta t=P^{-1}(\frac {P(t_{0})}{X_{solvent}})-t_0$.
(I'd tried to write down the specific process. But I couldn't do it well on words. Still you can see it by looking at the graph of any tri point.)


texts:
I know that cyclooctatetraene is non-planar because of

Angle strain and
Antiaromaticity if it was planar.

But what about cycloocta-1,3,5 triene or cycloocta-1,3 diene. It doesn't risk being antiaromatic, but there still is angle strain. Would it lose its planarity and hence inhibit resonance?

In general, when is the angle strain enough, that releasing the angle strain but also inhibiting resonance at the same time lead to a net increase in stability?


texts: Ambigious nature of aldehydic group in glucose

texts:
In aqueous solution, α-anomer and β-anomer of glucose
  remain in equilibrium with each other along with a small amount of
  glucose in open chain form ($0.02~\%$). The open chain form in the
  solution contains a free aldehydic group and hence gives several
  reactions involving free aldehyde.

Though little, the open chain form of glucose reacts with many reagents which are used to treat free aldehydic groups. Therefore, glucose in aqueous solution also reacts with those reagents.

$$\ce{glucose_{(aq)} + HCN -> gluco cyanohydrin} $$

$$\ce{glucose_{(aq)} + H2NOH -> gluco oxime} $$

$$\ce{glucose_{(aq)} + H2NNHPh -> gluco phenylhydrozone} $$

$$\ce{glucose_{(aq)} + 3H2NNHPh-> gluco osazone} $$

$$\ce{glucose_{(aq)} + Br2_{(aq)}-> gluconic acid} $$

Glucose also answers Tollen's reagent test, Fehling's solution test and Benedict's solution test.

However, as interesting it may seem, glucose is a two-face molecule. Here are some reactions which glucose does not like:

$$\ce{glucose_{(aq)} + NaHSO3 -> no reaction} $$

$$\ce{glucose_{(aq)} + {2,4-DNP} -> no reaction} $$

$$\ce{glucose_{(aq)} + {Schiff's reagent} -> no reaction} $$

Why is that glucose does not react with $\ce{NaHSO3}$ or $\ce{{2,4-DNP}}$ or Schiff's reagent while it answers many other reactions where the free aldehydic group is involved?

I am looking for a convincing answer. Most answers in web tell that some are strong and some aren't strong enough. If you give enough time, all the carbonyl reactions should work with glucose because there will always be $0.02~\%$ in open chain form. If some of it gets used up, then the equilibrium will shift and hence more open chain form of glucose will be formed.


texts: What is a hydrogen bond acceptor and donor?

texts:
I recently read about hydrogen bonding. One thing about which I am really confused is how to distinguish between hydrogen bond acceptors and donors.

I looked it up on SE and found this post, which said that water can form four hydrogen bonds as it has 2 hydrogen bond acceptors (the H atoms) and two H bond donors (the two lone pair of electrons on O atom).

When I looked it up on Wikipedia, it said:

  In a hydrogen bond, the electronegative atom not covalently attached to the hydrogen is named proton acceptor, whereas the one covalently bound to the hydrogen is named the proton donor.

And both of them seem to be contradictory. Which is correct?


texts: What is the source of discrepancy in the calculation of Standard State Gibbs Free Energy change of the reaction of HCl (l) dissolving in water?

texts:
I have calculated $\Delta_\text{r} G^o$ two different ways and got completely different results. Why? What assumptions have I made incorrectly, particularly in the first calculation shown below?

Okay, so everyone knows that liquid Hydrochloric acid is a strong acid so it completely dissociates in water according to the following chemical equation:

$\ce{HCl (l) + H2O (l) -> H3O+ (aq) + Cl- (aq)}$

If I used tabulated values of Standard State Gibbs Free Energy of formation $\Delta_\text{f} G^o$ to calculate $\Delta_\text{r} G^o$, standard State Gibbs Free Energy formation change of the reaction.

Standard State Gibbs Free Energies of formation:
$\begin{array}{lr}
\ce{HCl (l)} & \pu{-131.17 kJ mol^{-1}}\\
\ce{H2O (l)} & \pu{-237.19 kJ mol^{-1}}\\
\ce{H3O+(aq)} & \pu{-237.19 kJ mol^{-1}}\\
\ce{Cl-} & \pu{-131.17 kJ mol^{-1}}
\end{array}$

Source (I used this one because I couldn't find any that listed $\ce{HCl}$ as a liquid and not a gas):
http://www.vias.org/genchem/standard_ent...

Then, if you have one mole of each constituent according to the chemical equation, the standard state Gibbs Free Energy of the reaction = 0 kJ

by means of calculating ΔGoreaction = ΣΔGoformation of products - ΣΔGoformation of reactants

So ΔGoreaction should be less than zero if the reaction is favorable! But we know that HCl completely dissociates in water into Chloride ion and hydronium. What is going on here!?

If I calculate the standard state Gibbs Free Energy of the chemical reaction a different way.
That is that

$\Delta G^\circ_\text{reaction} = -R \cdot T \cdot \ln(\ce{Keq})$ at equilibrium, where

for the acid $\ce{HCl}$, $\ce{Keq = Ka} = \pu{1.3e6}$,

Then the Gibbs Free Energy change of the chemical reaction at standard state

$\Delta G^\circ_\text{reaction} = (\pu{-8.314 J K-1 mole-1}) \cdot (\pu{1 mole}) \cdot (\pu{298 K}) \cdot \ln(\pu{1.3e6})$

$= \pu{-34.88 kJ}$,

which is less than zero; therefore, the reaction is favorable. What is going on!? See the difference in the calculations!?

It seems that the Ka of strong acids like HCl is usually assumed to be too large for most websites to even bother displaying. But, I found a table of Ka's of strong acids here: http://depts.washington.edu/eooptic/links/acidstrength.html


texts: How does alum improve the settling of particles to produce 'clean' water?

texts:
How does the addition of alum — potassium aluminium sulfate or $\ce{KAl(SO4)2}$ — help settle the dust particles in water?

There was such a statement in my Year 9 textbook, and so I was wondering how exactly alum does it.

Edit: I have posted an answer below based on what I've found, but I'd love it if some else could verify and fill in the missing gaps in it.


texts: How can I undo the tarnish on my aluminium headphones?

texts: I thought of cleaning my headphones, which has an outer aluminium casing, with Dettol liquid which I believe has strong oxidising agents. This was a bad idea. It left a tarnish on the aluminium and I'd like to know if I can undo this.


texts: Free radicals vs Hund's rule contradiction?

texts:
How do we reconcile these two statements?

Formation of electron pairs is energetically favorable.  Therefore, free radicals are particularly reactive
Hund's rule - it takes energy to pair electrons, so orbitals are typically filled singly first


texts: How does the silver nucleate on glass in Tollen's reagent mirroring?

texts:
I want to know the exact mechanism for how silver would start to grow during a mirroring with Tollen's reagent. I've made two pictures to illustrate how I see the nucleation/growth process of silver on silica:

As you can see, I didn't draw any chemical bonds, because I think that the silver adherence is due to Van Der Waals forces. Am I correct? If that is the case, then I believe a place with high permanent polarisation would be better suited for the nucleation of silver.
Now, let's follow the logic. We have a greater electronegativity difference between $\ce{O}$ and $\ce{Si}$ ($3.44 - 1.90 = 1.54$) than between $\ce{O}$ and $\ce{H}$ ($3.44 - 2.2 = 1.24$).
For the upper oxygen, assuming an angle of 109 degrees, you get a total dipole moment of: $2(1.54)\cos\left(\frac{109}{2}\right) = 1.79$
For the lower oxygen with the bonded hydrogen, assuming an angle of 120 degrees , you would get a total dipole moment of: $1.54 + 1.24 = 2.78$
(please tell me if I'm wrong to assume a straight line!)
This would mean that you have a greater accumulation of electrons at the bottom oxygen, which would favor Van Der Waals attraction (Debye interaction, I guess, since you have a permanent dipole and an induced dipole). This, in turn, would mean that it would be a better nucleation site.
If you make a surface treatment using silane groups, I believe you promote the presence of $\ce{OH}$ groups at your silica surface, though I'm unsure about this. I do know that it makes better silver mirroring though. I've made another drawing:

Following my logic, this one is wrong in many way. First of all, I drew angles on the $\ce{Si-O-H}$ bonds, which I didn't draw on my first pictures. Secondly, the silver is not even near the oxygen atoms, which I believe are the nucleation points.
I'm confused, could you please point out to me where I'm right or wrong in my logic/knowledge?
Mainly:

Is there a bond forming between the silica surface and the silver? Or is there only Van Der Waals (Debye) attraction?
Is my depiction of nucleation & growth correct (for the first two pictures)?
Is my logic regarding the electronegativity correct?
Is my logic of " higher total electronegativity difference, hence better nucleation site" correct? (assuming I'm right about the Van Der Waals Forces)
Is my depiction of silanisation correct?
Am I right to say that the higher abundance of surface $\ce{OH}$ groups by silanisation implies better nucleation?
Could I do the same when using a strong acid on my glass surface?


texts: Does passing chlorine gas through water form hydrochloric acid or bleach? Also, will a mixture of hydrogen and chlorine gas from electrolysis of brine do the same?


texts: Cleaning a round-bottom flask, especially after distillation

texts:
I was wondering, how can I clean my RBF after doing a distillation? Cleaning it with a simple pipe-cleaner or similar cleaner is a headache, due to the roundness of the flask.

Is there a more effective method?


texts: Why some materials are transparent, but other ones aren't?

texts: We have two materials; say glass and wood. Light passes through glass but it doesn't pass through wood. Is it caused by atoms and molecules arranged in glass and wood such that they interact differently with light?


texts: Automated Identification of Isomeric Relationship from 3D Structure?

texts:
Is there a software package that when given two sets of 3D structures can return the isomeric relationship between them?  Even if it was only able to state that they are conformational isomers that would be enough.

It appears that Jmol has the ability, but I am seeking a non-graphical solution that could be easily included in scripts that would compare many such pairs of structures - in addition, I'm not a java programmer.


texts: How to model Chemical Kinetics when both ligand and receptors are moving?

texts:
I am not a chemistry student but trying to understand something that requires Chemistry. My problem is that when we have Ligand and receptor reaction to form complex we normally assume as from wikipedia

"In protein-ligand binding, the ligand is usually a molecule which produces a signal by binding to a site on a target protein."

My issue is do we have chemical kinetics giving us some clue when both of Ligand and receptor is moving, of course this is something like a reaction in a solution but I am majorly concerned with probability that Ligand be able to bind with receptor when both of them are in random motion and any literature related to that.
I may not that much clear in my presentation, but it will be really helpful if any kind of support be given.


texts: Is change of pH of water with respect to temperature linear?

texts:
Only recently I learned that the pH of water varies with temperature, from about 7.47 at 0 °C to 6.14 at 100 °C.

My question is, first, is there a geometric explanation for this, in the sense that water can perhaps arrange itself in a way that partial bonding of oxygen to a third hydrogen can happen without simultaneously producing hydroxide ions to balance things out?

And--related--is the spread of pH above enough to create a detailed profile for the variation of pH with temperature? If so is it linear?


texts: Can high-tin bronze be made sharper than low-tin bronze?

texts:
I am not sure how sharpness is measured, but I do know that certain materials can be designated sharper than others, for example obsidian is said to be the sharpest material:

  The prismatic glass blade is infinitely sharper than a honed steel edge

So my question is, will a honed edge of high-tin bronze be sharper than a honed edge of low-tin bronze, and if so why?


texts: Was technecium "recently" renamed technetium in English? I know when I formally studied chemistry (in the USA) that earth, air, water and fire were on the periodic table, but I really remember the element as being technecium.


texts:
I'm confused about the crystal system of MoS2.

In the case of the monolayer MoS2, it has 3-fold rotation symmetry when viewed from the top of its unit cell (c-axis). Even in the case of bulk (AB stacking) MoS2, it has only 3-fold rotation symmetry from the same direction. So, I expected that it must be the trigonal system. However, 'Materials Projects' doesn't seem the trigonal system.

Here are some database from 'Material Projects'

List of MoS2

https://materialsproject.org/#search/materials/{%22reduced_cell_formula%22%3A%22MoS2%22}

Bulk MoS2

https://materialsproject.org/materials/mp-2815/

Bilayer MoS2

https://materialsproject.org/materials/mp-1025874/

and so on.

Some of them are the trigonal system, and the others are the hexagonal system. I studied the minimum symmetries determine the crystal system, or that is a misconception. But now, it might be wrong by the web data.

Which one is correct and if both are correct, how can I check the 6-fold rotation symmetry for the hexagonal system?

(appended--------------------------------------------------------------------)

This is the figure for the HCP structure. Its symmetry along the c-axis can be called 3/m or bar(6).

This view is the bulk MoS2 along c-axis. In the unit cell, it has two layers of MoS2. However, it has 6/mmm point group. How does this happend?...
https://materialsproject.org/materials/mp-1018809/#


texts:
My professor stated the following statement:

  In a covalent bond, there is a presence of a partial charge in the atoms that combine to form a compound. For example in $\ce{H2O}$, since $\ce{O}$ is more electronegative, therefore there is a presence of a partial negative charge around $\ce{O}$. Similarly, as $\ce{H}$ is less electronegative, it has a presence of a partial positive charge around it. These partial charges are very feeble.

I found this statement to be little incomplete. So, I decided to find the reason of this partial charge. One of the video that talked about partial charges stated this:

  Since $\ce{O}$ is more electronegative than $\ce{H}$, therefore the shared electrons tend to spend more time around $\ce{O}$ than $\ce{H}$ and this is the reason of the partial charges.

Now, my questions are:

 If the shared electrons spend more time around $\ce{O}$ then it means that for some time $\ce{O}$ will be negatively charged and for some time $\ce{H}$. If this holds true, then why do we say that there is presence of  partial charges  around the atoms instead of saying that there is a presence of complete charge around the atoms but the charges keep on changing?

 What does my professor mean by 'feeble' charges? Is the charge reduced or something else?

If the question is unclear, ask me to edit it in comments.


texts:
The web page Aromaticity in Graphene and other 2-D Systems begins:

I. Graphene
While the σ-bonding in graphene is assumed to be a rigid honeycomb framework built out of two-center two-electron (2c-2e) C-C σ-bonds, the π-bonding is supposed to be delocalized. However, according to the adaptive natural density partitioning (AdNDP) analysis and the electron sharing indices, graphene is aromatic, but its aromaticity is different from the aromaticity in benzene, coronene, or circumcoronene. Aromaticity in graphene is local with two π-electrons located over every hexagon ring. (emphasis added)
II. BC3 Honeycomb Epitaxial Sheet
[...]

Update: The wording is similar to what is written in Is Graphene Aromatic? Popov, BozhenkoEmail &  BoldyrevEmail (2012), Nano Research, 5, (2), pp 117–123 (open access here):

ABSTRACT
We analyze the chemical bonding in graphene using a fragmental approach, the adaptive natural density partitioning method, electron sharing indices, and nucleus-independent chemical shift indices. We prove that graphene is aromatic, but its aromaticity is different from the aromaticity in benzene, coronene, or circumcoronene. Aromaticity in graphene is local with two π-electrons delocalized over every hexagon ring. We believe that the chemical bonding picture developed for graphene will be helpful for understanding chemical bonding in defects such as point defects, single-, double-, and multiple vacancies, carbon adatoms, foreign adatoms, substitutional impurities, and new materials that are derivatives of graphene.

Question: How is the aromaticity in graphene different from the aromaticity in benzene? It is likely that those familliar with the topic will already understand the explanation in the block quote, but is it possible to find a simpler if less accurate way to explain the difference, in a similarly compassionate way to how this answer was extremely helpful to my question about double bonds and chromophores?


texts: What dangerous gases could electrolysis with water and sodium carbonate produce?

texts:
My friend was very nervous when he noticed that I'm performing electrolysis in a room that we've just been residing. (it was under open window to let $\ce{H2}$ out) After a sharp argument, he made me shut it down, though I still thought that it was safe.

I'm using $\ce{Na2CO3}$ as electrolyte and as far as I know, it doesn't get electrolysed. I use normal pipe water. Such water surely contains some minerals however in really small amount. My friend pointed out that it also contains chlorine and that's what he's afraid of. He would disregard my notice that he's drinking this water often.

I'm using copper electrodes, producing copper hydroxide and copper carbonate. I failed to find out whether these compounds are hazardous. They're in solid state anyway.

From what I've said you can see that I'm very sure that the reaction is not hazardous. But I'm not chemist. There could be something I didn't think of in which case I've been poisoning myself for quite a while.

Could you make me sure or warn me?


texts: Can a solute be physically filtered out of a solvent?

texts:
Suppose that I have a substance dissolved in water. I then pour the solution into a filter. The filter's pores are large enough to allow the passage of water, but not the passage of the substance. In this case, would the substance come out of solution as the water goes through the filter but the substance doesn't, thus resulting in a solute being filtered out of a solvent? In this scenario, the substance is a molecular compound that does not dissociate into ions when dissolved.

In a second scenario, what if the substance is an ionic compound like salt, and the filter's pores are large enough to let one of the ions through (And of course, water molecules can also pass), but not the other? What would happen then?


texts: Understanding Moseley’s law from the Rydberg-type equation?

texts:
To explain the characteristic X-ray emission peaks for various elemental targets, a formula was developed which was similar in construct to the Rydberg equation for H-atom as derived by the Bohr-model.

$$\tilde\nu=R\left(\frac{1}{n_\mathrm{f}^2}-\frac{1}{n_1^2}\right)\left(Z-\sigma\right)^2$$
where $\tilde\nu$ is the wavenumber, $\sigma=1$ for the $K_\alpha$ line and $7.4$ for the $L_\alpha$ line. My question is:
Although Bohr model is wrong in light of the modern quantum mechanical concept of atomic structure, why does the energy for transition (and X-ray emission) of complicated atoms with complicated screening effect be represented by a simple adjustment of the $Z$ factor in the Rydberg equation with the value of $R$ used in case of H atom? Why isn’t there a need of complicated corrections (instead of simple subtraction of an experimentally obtained $\sigma$) to predict the X-ray wavelength?


texts: Book for understanding synthetic techniques and apparatus(with pictures)

texts:
Is there a standard textbook to understand numerous laboratory apparatus and the assembly techniques that can be used for carrying out different processes (with pictures)?

I have been cleaning my lab and came across many glassware, from as long as 30 years back which I don't have much idea about regarding their usage. Is there a book which could help me in understanding and classifying the resources that i have with me?

P.S. I am in a crystal engineering lab.


texts: How can you infer that density decreases when ice melts from the water phase diagram?

texts:
I know the phase diagram shows negative slope for water which is an exceptional case...  But how do you read that graph and get to the conclusion that density is increasing?
It's the one with pressure plotted against temperature
Thanks ..

sorry i couldn't attach the graph here...


texts: How to calculate the concentration of NO at equilibrium?

texts:
$\ce{N2(g) + O2(g) <=> 2NO(g)}$, $K_c = 4.1 \cdot 10^{-4} (T=2000~^\circ\mathrm{C})$
  What is $\ce{[NO]}$ when a mixture of $0.20~\mathrm{mol}$ $\ce{N2(g)}$ and $0.15~\mathrm{mol}$ $\ce{O2(g)}$ reach equilibrium in a $1.0~\mathrm{L}$ container at $T=2000~^\circ\mathrm{C}$?

When K is $\cdot10^{-4}$, you can assume the change is negligible, and just using the concentrations you can get from the given mole amount and the container volume, I get the right answer. When plugging back into, to see if it matches the give $K_c$, it's right:
$$((0.20~\mathrm{M}~\ce{N2})(0.15~\mathrm{M}~\ce{O2}) \cdot 4.1\cdot10^{-4} K_c) = x^2.$$ Ans: $\ce{[NO]} = 0.0035~\mathrm{M}$.

From what I've read and heard you should be able to do it 'the hard' way, using the quadratic formula, like you would if $K_c$ wasn't to $10^{-4}$, and small enough. But I can't seem to get the right answer trying to do it that way.

Rearranging everything, the equation I get to plug into the quadratic formula is
$$x^2 - 0.35x + 0.03,$$ then I get $0.2$ and $0.15$ as the answers. $0.2$ is too high, subtracting it from the $0.15~\mathrm{M}$ $\ce{O2}$ initial wouldn't be right. So using the $4.15$ as $x$, the change in $\mathrm{M}$, and subtraction that from the initial concentrations I have, then plugging that into the equation for $K_c$, even tried rearranging it in case I have got something mixed up, but I don't get anything close to the given $K_c$.


texts: What is the difference between fire and warm body?

texts:
A burning body has flames (Candle flame)whereas a hot or warm body (warm utensil or body being hot but doesn’t burn )is just very hot. Keeping hand near a burning body makes you feel hot but not exactly near a hot body.A burning body has flames which are yellow,then blue and purple for some outside in colour.
What exactly is a burning body and how does it differ from a warm-body?
Please tell how can I improve my question if not suitable ?


texts: Electrolysis, Concentration of Electrolytes

texts: So it says the Chlorine gets discharged as the concentration of chlorine ions are higher than OH ions, but why don't the concentration applies to Na+ ??


texts:
Do electron donating groups make a molecule nucleophilic?
One group, the alkyl group in this example, is electron donating in $\ce{CH3CH2O-}$. Will the molecule be nucleophlic?


texts: Chemical formula of a compound crystallized in a cubic lattice

texts:
Question

  In a cubic lattice of $\ce{XYZ},$ $\ce{X}$ atoms are present at all corners except one corner which is occupied by $\ce{Y}$ atoms. $\ce{Z}$ atoms are present at face centres. What is the formula of compound?

Answer

   $\ce{X2YZ24}$

My solution

Let the number of atoms in a unit cell be $N.$ Then

$$
\begin{align}
N(\ce{X}) &= 7 × \frac{1}{8} = \frac{7}{8}\\
N(\ce{Y}) &= 1 × \frac{1}{8} = \frac{1}{8}\\
N(\ce{Z}) &= 6 × \frac{1}{2} = 3
\end{align}
$$

Therefore, the ratio would be

$$N(\ce{X}):N(\ce{Y}):N(\ce{Z}) = \frac{7}{8}:\frac{1}{8}:3,$$

which is the same thing as $7:1:24.$ So, the formula is $\ce{X7YZ24}.$

What am I doing wrong?


texts: Term symbols for nitrogen: determining J

texts:
I'm trying to figure out what terms are possible for nitrogen with the electron configuration $\ce{[He] 2s^2 2p^3}$. There is an old question on StackExchange and the corresponding answer was a great help already but doesn't mention $J$ or specify what terms exactly are possible. I'll try to explain how I would determine the possible terms:

The s-electrons needn't be considered for they complete the s subshell, this means I'm left with three p-electrons. I do get the same results for the possible values of $L$ and $S$ as user orthocresol provided with his answer namely:

$L=3,2,1,0$

$S=3/2, 1/2$

Now the possible values of J range from $L+S$ to $|L-S|$:

For $L=0$ there are two S-Terms*: $^4\!S$ and $^2\!S$ giving

$$^4\!S_{3/2} \quad ^2\!S_{1/2}$$

$L=1$ gives two terms*: $^4\!P$ and $^2\!P$, the former term has the following possible J values: $J = 5/2, 3/2, 1/2$ and the latter: $J=3/2, 1/2$. The P-Terms of this electron configuration are:

$$^4\!P_{5/2} \quad ^4\!P_{3/2} \quad ^4\!P_{1/2} \quad ^2\!P_{3/2}\quad ^2\!P_{1/2}$$

Doing the same for $L=2$ there are two D-Terms*: $^4\!D$ and $^2\!D$, possible J values for the former: $J = 7/2, 5/2, 3/2, 1/2$ and for the latter: $J = 5/2, 3/2$. This gives six different terms.

I'm stopping at this point because I think I'm not doing it right. Using the NIST ASD I only see five terms with this electron configuration in the Grotrian diagram:

$$^4\!S_{3/2}, ^2\!D_{5/2}, ^2\!D_{3/2}, ^2\!P_{1/2}, ^2\!P_{3/2}$$

and according to the book "Physical Chemistry: A Molecular Approach" Table 8.4 for three p-electrons only $^2\!P,^2\!D,^4\!S$ Terms are possible. What's wrong with my approach that I'm that much off?

*Question on the side: I don't think it's correct to use the term "term" here because what I'm talking about is split into actual terms. Is there a way to refer to, for example, the $^4\!D$-Terms in general, maybe term system?


texts: Why is electrospray ionization a soft technique in comparison to electron ionization?

texts:
I know that electrospray ionization (ESI) is a soft ionization technique and that electron ionization (EI) is not, because it causes a great amount of fragments in a fast time due to the fact that a single electron is accelerated up to 70 V. ESI MS can cause fragments, but slower and not as good. But why is this effect less strong than in EI?

Thank you for your help!


texts: What is the voltage dependence of the thickness of oxide coating through anodising?

texts:
In titanium anodising, solid titanium reacts with the oxygen formed at it's surface (to form titanium(IV) oxide or $\ce{TiO2}$) through the electrolysis of water. Experimentation and research has shown that the thickness of the coating is dependent on voltage and not current. The potential difference obviously plays some part in the reaction then (besides the water electrolysis) due to the fact that merely placing titanium in an environment with more oxygen gas does not affect the thickness of the naturally occurring oxide, but I am struggling to find out how (through both thought and research) the voltage affects the depth of the coating formed.

I understand that the actual oxidation reaction can be written as:

\begin{align}
\ce{Ti &-> Ti^{4+} + 4e-}\\
\ce{O2 +4e- &-> 2O^{2-}}
\end{align}

Which are added together to get:

$$\ce{Ti + O2 -> TiO2}$$

I also understand that redox reactions usually include a reduction potential or $E^0$ value. Now this may or may not be relevant but it is the only related value I can find with a voltage associated. I have also thought that as the coating of $\ce{TiO2}$ builds up, the resistance of the circuit would increase. I just cannot understand how or why the voltage affects the depth (Is this the right word, as it is converting not depositing?) of the formed oxide layer.

So with that my question is more like a request for any insight/resources that could help with my understanding of the voltage-dependency of the depth of the formed oxide layer (specifically titanium, but I'm assuming it would be relatively easy to generalise from other metals such as aluminium or niobium (which I have also searched for)).


texts: Why is that tyrosine, phenyalanine, and  tryptophan absorb UV light while other amino acids don't even absorb visible light? Does it have something to do with aromatocity?


texts: Diffuse functions for Ahlrichs/Karlsruhe basis sets in Gaussian?

texts:
As the question states, can one use the basis sets of Ahlrichs and coworkers (e.g. def2-SVP, def2-TZVP, ...) with diffuse functions (e.g. def2-TZVPD) in Gaussian?

The regular basis sets have been implemented, but not the diffuse functions according to their homepage. Is there some other way to access diffuse functions for these basis sets in Gaussian?


texts: How to calculate Energy Efficiency of electrochemical production

texts:
I'm trying to understand some basic electrochemistry as a non chemist and struggling to find the info online effectively.
Its clear that energy efficiency = Energy(useful) / Energy (input).
So, I know how to solve for energy efficiency (η) when given a quantity of product and quantity of electricity.
η = product combustion energy / (power x time)
However, I'd like some help figuring out what to do with the information that is usually given in papers, so I can calculate η when it is not given.
Most papers report Faraday efficiency ( which I understood to be the moles of electrons that end on desired product/ invested moles of electrons)  (the denominator here can be calculated from the current and F constant).
also given are:
Catalytic surface area.
Cell voltages.
Over potentials.
ohmic drops...
etc.
For instance, I want to calculate the energy efficiency of formate production given in this paper (see image) https://www.nature.com/articles/s41467-020-17403-1/figures/3

Alternatively:
How to calculate the bottom line here:

If you can explain how its done or points me to resources to learn this, that will be super helpful.
Thanks,
D.


texts:
I’m a little concerned that there is a far stronger mix of antifreeze in my car's coolant system than I am aware. I check the antifreeze level in my car (using a refractometer) when the engine is cold (after being left overnight).

During the night, can the antifreeze settle to the bottom of the cooling system, thus leaving a weak mixture of water and antifreeze within the coolant reservoir up top, where I take a sample with the refractometer?


texts:
In the Acid-base map -shown below- each line denoted as an isohydric line shows the pairs of $ PCO_{2}$ & $ [HCO_{3}^{-}] $ that give a certain $ pH $. So each line connects the values of $ PCO_{2}$ & $ [HCO_{3}^{-}] $ that give a value of $ pH $ that is constant across that line..
The 7.4 line shows the isohydric line of physiological pH,the central ellipse shows the normal range.
I understand the Henderson–Hasselbalch equation:
$\mathrm{pH}=\mathrm{p} K_{\mathrm{a}}+\log _{10}\left(\frac{[\mathrm{Base}]}{[\mathrm{Acid}]}\right)$
What I would like to know is how this map established either experimentally or mathematically or both preferably.


texts: How to figure out number of atoms in a molecule? e.g. Phosphorus exists as P4

texts:
We know that Phosphorus exists as P4 but how can I figure out the number of atoms in a molecule for other elements?

This is the question that requires the use of P4. I would never have known Phosphorus is tetra-atomic and that the equation will involve this. Is there a way to figure that out?


texts: What mechanisms might make a substance travel different distances on the same TLC plate?

texts:
When doing TLCs to monitor reactions, it is considered good common practice to not only spot the reactants and the reaction mixture (likely after some mini-workup), but also to include a ‘cross-spot’: every other substance (mixture) spotted somewhere on the plate is spotted together on one spot, commonly labelled something like X.

When asking why during my bachelor's thesis, the PhD student supervising me said something that roughly translates to:

  You can't be sure that the components don't run differently in the mixture than by themselves.

But in a perfect world, they should. Aside from the obvious case of having a polar reaction solvent that didn't entirely evaporate and skewes the elution mixture on parts of the TLC, are there other reasons why the components of a mixture should have different Rf values when spotted separately?


texts: Is phosphorus trichloride really a stronger Lewis acid than antimony pentafluoride?

texts:
The following was a question from the ETS Chem GRE guide and apparently this was an actual question on an exam a few decades ago. Unfortunately, no explanation for the answer was given, and I couldn't find anything more helpful on the internet.

  Which of the following molecules is the strongest Lewis acid?
  (a) $\ce{NF3}$
  (b) $\ce{SbF5}$
  (c) $\ce{NaCl}$
  (d) $\ce{PCl3}$
  (e) $\ce{SnCl2}$

The correct answer is supposed to be (d), which I find very surprising.  I thought it should be (b), since I know that $\ce{SbF5}$ has an empty orbital that can facilitate electron donation.  I also know it is a strong Lewis acid.

What orbital on $\ce{PCl3}$ is empty and why would $\ce{PCl3}$ be stronger than $\ce{SbF5}$?


texts: What is the difference between atomic theory given by Democritus and John Dalton? Because I have read in many books and figured out that both theories explain the same i.e atom is an indivisible particle and all elements differ in shape and weight of their atoms. So basically what is the difference in both the theories?


texts: First of all, I'm not a chemist and my knowledge in chemistry is not that extensive. However, I would like ask the following question: are there any chemical reasons that would explain that mixing a blue ink with alcohol and MEG, lets say 3% as part of a volume of 1 L, gives a ways stronger blue than mixing in a big tank 3% of the same ink on a volume of 30000 L? Being in that last mix a greenish colour the result.


texts:
The following question came in Paper 2 of JEE Advanced 2014-

Here we have $\ce{CH3-}$ as the nucleophile. There are 2 possible attacks:

SN2 type attack on the chlorine group.
Nucleophilic addition on the carbonyl.

The answer given is option D, which will happen by the 2nd pathway(nucleophilic addition).

Why is nucleophilic addition given a preference over SN2? I feel that nucleophilic addition should rather decrease the reaction rate because the carbon goes from sp2 to sp3, decreasing the bond angle and hence increasing the repulsion


texts: How does bombarding a molecule with electrons cause ionization?

texts:
I am a chemistry student, and my current are of study is mass spectrometry.

In the ionization process, atoms are bombarded with electrons, but how does this work? I assume the flow of electrons attract the electrons of the atom, thereby removing them, but where do the atom's electrons go?


texts: What is the temperature dependency of the van-der-Waals constants?

texts:
What is the effect of the temperature on the van-der-Waals constants $a$ and $b$?

I have checked on the effect of pressure and volume on the van-der-Waals constants, but I've not been able to get the effect of temperature.


texts: How to know the aluminium sulfate solubility as function of the pH?

texts: I'm trying to find a diagram or a reference for to know the solubility of aluminium sulfate $\mathrm{Al_{2}(SO_{4})_{3}}$ in differents pH values. Something like:


texts: Why isn't calcium carbide more corrosive?

texts:
Acetylene has a pKa of 26, I think.  While that's pretty acidic ... for a hydrocarbon ... I still expect calcium acetylide (carbide) to be a very strong base indeed.  Yet the NFPA fire diamond health code is just a 1, compared to a 3 for both sodium and calcium hydroxides, even though each mole of the carbide ought to create a mole of calcium hydroxide the moment it touches water.  Little kids play with toy cannons powered by somewhat impure calcium carbide, taking no special lab precautions.  Why is that possible?
Update: I have since noticed that those NFPA diamonds don't all agree. The Santa Rosa Fire Department and Wikipedia say Health rating is 1.  Fisher Scientific says it is 2.  NOAA says it is 3.  I may never look at one of those little diamonds the same way again...


texts: How to explain the products of the nucleophilic aromatic substitution of 1-chloro-3-methylbenzene with NaOH?

texts:
I guess this reaction is a nucleophilic aromatic substitution where $\ce{ONa-}$ is the nucleophile $\ce{Cl-}$ the leaving group, is that right?

Methyl group is a ortho-, para- director. So why should I have a meta product here? Don't we need an electron withdrawing group ($\ce{NO2}$ , carbonyl) in a NAS-reaction which is at ortho or para positions to the leaving group?

I am a bit confused about the shown picture.


texts: Do azeotropic mixtures evaporate proportionally?

texts:
Do azeotropes evaporate, without boiling, in proportionate amounts, or does this property describe their behaviour only at boiling point?
Concretely, if 91% isopropyl alcohol/water (by volume, i.e. an azeotropic mixture) is left open at say 25 °C, will it remain in that proportion as it evaporates, or become more dilute (until just water) as the alcohol evaporates faster?
Further, above this point, would the alcohol evaporate faster 'degrading' it until 91% at which point it behaves as the answer to above? (Which would incline me to think the answer is no, if not boiling the water and alcohol would evaporate 'independently' and the alcohol concentration would fall no matter the starting point, it's not magic.)


texts: Why can't you achieve the equilibrium exactly in the middle (K=1) when you add enough heat/energy?

texts: My reasoning would be that given the high amount of energy added, both the activation energies of the reaction from left to right and right to left are excessively surpassed thus both directions are as easily achieved. Please correct my reasoning if this is wrong. Thanks!


texts: Which has more internal energy, a bucket of hot water or a bucket of cold water

texts:
Online answer I found :
The bucket of hot water has more internal energy.
Internal energy depends on the amount (mass) of substance and the kinetic energy of the molecules of the substance.
My thinking to it :
Since it is written dependant on mass, then swimming pool has more mass than bucket of hot water.Since it has even higher K.E , then how can Bucket of hot water have more Internal energy than swimming pool?


texts: Does anyone know of groups working on water sorbtion testing and/or the use of inverse gas chromatography for characterizing Perovskites (as a class of materials)? Especially with regard to applications eg solar PV


texts:
Why is $\ce{Ba(OH)2}$ Barium hydroxide not Barium dihydroxide?
Why is Lithium carbonate $\ce{Li2CO3}$ instead of $\ce{LiCO3}$?

Is  there a formula or is just the case for these two?


texts:
While reading the preparation of phenol from cumene by reaction with $\ce{H2O2}$ or partial oxidation, I was curious to find out why toluene wasn't used.

I checked the literature and found that benzaldehyde would be formed in the case of toluene [1, 2].

Why does benzaldehyde form in the case of toluene?
Does the peroxide formed after initial oxidation become benzaldehyde due to its instability?
Why doesn't acetophenone form from the peroxide formed in cumene?

References

Sun, H.; Blatter, F.; Frei, H. Selective Oxidation of Toluene to Benzaldehyde by $\ce{O2}$ with Visible Light in Barium(2+)- and Calcium(2+)-Exchanged Zeolite Y. Journal of the American Chemical Society 1994, 116 (17), 7951–7952. https://doi.org/10.1021/ja00096a084.
Wang, X.; Wu, J.; Zhao, M.; Lv, Y.; Li, G.; Hu, C. Partial Oxidation of Toluene in $\ce{CH3COOH}$ by $\ce{H2O2}$ in the Presence of $\ce{VO(Acac)2}$ Catalyst. The Journal of Physical Chemistry C 2009, 113 (32), 14270–14278. https://doi.org/10.1021/jp9028062.


texts:
I have been asked to find the major product of the following reaction:

This is my thought process: the lone pairs of the oxygen atom connected to $\ce{-Et}$ are less delocalised than the other oxygen atom. So, that will abstract the $\ce{H^+}$ from $\ce{HI}$ leaving behind $\ce{I^-}$ and producing a positive charge on the oxygen atom. Now the oxygen atom will take up the bond pair electrons and $\ce{I^-}$ will form a bond in $\ce{S_{N}2}$ mechanism, producing $\ce{I-Ph-O-Ph}$ and $\ce{EtOH}$ as products.

But, the answer in the book states that:

The ether linkage will break as it does not have a double bond character due to the absence of resonance.

Why is the ether linkage breaking here? What does it mean by "it does not have a double bond character"?


texts: Can anybody give me an example of an endothermic dissolution process, preferably one in which name of the substances involved are easy to remember. I have searched the Web thoroughly but could not find an example, only definitions. Thanks in advance.


texts: How does the effect of heat and effect of substituents affect racemization of biphenyl compounds?


texts: Conversion of 1,2-dione to a 7 membered oxepane?

texts:
Has anyone heard of forming a seven membered ring from the rearrangement of a 1,2-dione? What I am talking about specifically is benzil rearrangement:

Could anyone give me guidance for how on earth something like this would form?


texts: What is the 'electronic energy', in units of 'negative' hartrees, of a molecule?

texts:
On a NIST (National Institute for Standards and Technology) page on the molecular details of water and it's various isotopologues, I came across this:
Electronic energy:  -76.4089547246 hartree
There is, really, no other context on the page....
I found the page after typing in 'ionization energies of water'....
I put this here on Chemistry SE rather than Physics SE, I hope that is OK....
I DID look around to try to find an answer elsewhere, before coming here and posting...


texts: Last step of nicotine extraction using DCM

texts:
After using hydro-distillation method with distilled water and NaOH, separating the extract with dichloromethane, distillate it at 40 °C/104 °F, I'm left with some yellow pale oil.

I'm just wondering if traces of DCM could still be detected in the final product or if I need more steps to purify the extracted alkaloids ?


texts: Selective etchant for Al2O3 (Does not etch Al, Cu, Zn, Sn)

texts:
I'm looking for a wet-etchant to remove aluminum oxide created by anodizing, but not etch the unoxidized metal (with greater than 10:1 selectivity)

I know about chromium(IV) oxide and fluorine-based etchants, but those are problematic for safety and disposal. Are there other etchants? It can be an acid or a base.


texts:
I've searched the internet for a definition of what the different shells in enzymes/proteins are and haven't found a good answer. This Nature article, which is about an enzyme that catalyzes Kemp Elimination, has the sentence:

  The Val12Met and Phe77Ile mutations, also in the second shell, cause changes to internal cavities that cause a slight rotation in the backbone at Trp50 that also favors the alternative configuration.

What is the second shell, and how many different shells are there?


texts: Why we make pyrogallol alkaline to absorb oxygen?

texts: Pyrogallol is activated by -OH groups but what is the use of making it alkaline?


texts: Does aniline react with diazonium ions at C or N?

texts: In the azo coupling of aniline with benzenediazonium cation, I thought of two possible products 1 and 2 that could be formed. However, I can't work out which will be preferred. What would be the major product and why?


texts:
My teacher said that OF2 is the third most powerful oxidising agent after F2 and atomic O, but I think O2F2 should be even more oxidising, since it less stable than OF2. I just read on quora that O2F2 is so unstable that it readily oxidises anything that comes in contact even when it is frozen. Also, in case of hydrides of p-block we say that reducing power increases down the group as the tendency to donate H increases due to decreasing thermal stability, so on similar lines, I think O2F2 should be a more powerful oxidant.

Or is it because in OF2, the oxidation state of O atom is +2 (compared to +1 in O2F2), which it wants to get rid of and thus gets reduced, oxidising the other species readily. But if this is true then why is it more stable as we know that stability is inversely proportional to reactivity? Or are the concepts of stability and oxidising power completely unrelated?

I was not able to find the electrode potentials of these species, so how could they be even compared reliably?


texts: What does the Mesh in the mesh size of silica gel that is used for various chromatography techniques mean?


texts: Why or why not can hydroquinone and 2H-pyrrole act as ligands?

texts:
I want to understand why hydroquinone and 3H-pyrrole can or cannot act as ligands in transition metal complexes. If they are ligands, then what is their denticity?

I'm trying to understand the overall co-ordination behaviour of these two molecules, so please consider all atoms and rings as possible electron donors.

I think the denticity for the second molecule should be 1, since there's only 1 donor atom N, but would it be a weak ligand as the nitrogen is double bonded to a C?


texts:
The specific heat capacity at constant volume and the specific heat capacity at constant pressure are intensive properties defined for pure, simple compressible substances as partial derivatives of the functions u(T, υ) and h(T, p), respectively,
$$c_v=\left ( \frac{\partial u}{\partial T} \right )_v$$
$$c_p=\left ( \frac{\partial h}{\partial T} \right )_p$$
Can someone explain why this is? The book from which I got this from doesn't derive these expressions.


texts: I am a PhD student in materials engineering. What is D3O? It is not a chemical, but rather a "polyurethane energy-absorbing material" (from Wikipedia). I would wish to know and study the chemical composition of this impact shock absorbing materials.


texts: Intermolecular Forces for Ionic Compound?

texts: So in class we have learned London dispersion, dipole-dipole, ion-dipole and hydrogen bonding for intermolecular forces. Our teacher always uses covalent molecules as examples. So I was wondering which intermolecular forces ionic bonds have, if so, how are they formed?


texts: What reactions will their reaction rates increase with time?

texts: My textbook states that for most reactions, the reaction rate decreases with time. I wonder what reactions will have increasing reaction rates with time. I know that adding a catalyst will increase the reaction rate but the final reaction rate will finally be zero. So, what reactions will their reaction rates increase with time?


texts:
Why is $\ce{[Pt(py)4][PtCl4]}$ called tetrakis(pyridine)platinum(II) tetrachloridoplatinate(II) and not tetrapyridineplatinum(II) tetrachloridoplatinate(II)?

I thought you use tetrakis for ligands that contain numerical prefixes. I don't understand how pyridine contain numerical prefixes.
I saw this in this site.
The same applies for copper(II) glycinate in IUPAC naming.

Is this because of the property of the ligand?

I know this seems to be a silly question, but I can't understand why this is.


texts:
A few weeks ago I decided to harvest the lavender in my garden and put it through a still to extract the essential oils. The still in question is essentially just an air cooled condenser.

I collected the first fraction in a clear plastic vial. Within a day the vial had become cloudy looking (like frosted glass - the lavender oil itself was not cloudy - just the container). After a week this had happened:

The whole top of the container has been eaten away and is now flexible where before it was rigid.

What's caused this, is it expected behaviour?

Is there anything I should consider before using the lavender oil in fragrances and soaps?


texts: Why is 2-methyl-2,3-pentadiene achiral (allene)?

texts:
2-Methyl-2,3-pentadiene is achiral. Why?

  Centre of symmetry
  Plane of symmetry
  C2 axis of symmetry
  Centre and Plane of symmetry.

I've drawn the structure:

So far I've dealt with planes of symmetry in determining whether a compound is chiral or achiral and nothing more. So I'm relatively new to axes and centers of symmetry.  I can't visualise the rotations in the axis of symmetry.
What I don't understand is: How can you say a compound is chiral/achiral based on it's axis of symmetry?


texts: Chemical shift value and proton NMR spectroscopy

texts:
I am a bit confused about what chemical shift value signifies in proton NMR spectroscopy. If the proton of the standard substance TMS absorbs X Joules of energy to go into resonance, than a substance with a chemical shift value of 2.5ppm means it absorbs:

energy absorbed= X- (2.5X/10^6)?

Could someone please tell me if this is what chemical shift value is mathematically. In my book, it says the substance absorbs "2.5 millionth less amount of energy than TMS to go into resonance"... but I don't really understand this.


texts: Why can curcumin cross the blood-brain barrier, but not congo red?

texts:
I've read that both congo red and curcumin are able to inhibit the clumping together of amyloid $\mathrm{β_{42}}$ in the brain, which would otherwise result in Alzheimer's disease.

Apparently, congo red cannot cross the blood-brain barrier (BBB) while curcumin can.

From what I learned at my biology classes, the BBB is lined by squamous, endothelial cells. Those cells are, as far as I know, the most permeable kind of cells you could come across in the human body, and if congo red doesn't pass through that, then it must be one stubborn molecule.

Now the cell membrane, itself being composed of a phospholipid bilayer, normally shouldn't have a problem transporting lipophilic molecules across the membrane. From an earlier conversation with Jan, I believe congo red is a lipohilic molecule. Yet inspite of it being lipophilic, it still isn't able to cross the BBB.

Comparing the structures wasn't particularly enlightening.

But the possibility congo red could act as a bidentate ligand, does seem to make it stand out from  curcumin. Am I onto something here? Apart from that, and a somewhat larger size, I don't see why congo red shouldn't be able to cross the BBB.

Now, I'd like to know two things,

1) What enables curcumin to cross the BBB?

2) Why isn't congo red able to cross the BBB, even though it has a structure similar to that of curcumin?


texts: What happens when deodorants or perfumes expire

texts:
I know that deodorants and perfumes have alcohol as their main ingredient so I was thinking what happens when their expiry date passes?

I tried to search on google but got mixed results. Some say that they do not ever expire but some say that an expired deodorant can burn the skin.

What i think is  that as they contain mainly alcohol so maybe a major part of the alcohol gets oxidised to ketones or acids which may in turn harm the skin. Does anyone of you know what happens when deodorants expire?


texts:
I got in my car this morning and the temperature read 13 F (that's around -10.5 C.) While driving down the road, I noticed a bottle of water in my cup holder was frozen solid as expected.

Another bottle of water (cheap, thin-walled, plastic disposable water bottle) contained liquid water! I shook the bottle, not a single crystal of ice!

Shortly thereafter, I noticed the water became slushy, so it had begun freezing quite quickly!

The interior of the bottle was hardly perfectly smooth given the quality of the bottle and the water was half drunk so it was probably not super pure.

What caused this? Was this supercooling?


texts:
Lithium bromide refrigerator

Why is lithium bromide used in absorption refrigerators?  It is more expensive than sodium chloride.  The wikipedia article on lithium bromide says it is extremely hygroscopic.  However, it is less soluble in water than NaCl.  I am thinking that a salt capable of generating a more concentrated solution would work better in the absorption refrigerator as it would increase the propensity of water to leave the gas phase and enter the solution.  Am I wrong about that?  Is the affinity of water for lithium bromide so high that it is the most important factor?


texts: Does the rate reaction of clock reaction increase over time?

texts:
I'm studing the following version of iodine clock reaction, in which, $[\ce{H_2O_2}]_0$ > [ascorbic acid]$_0$
$$\ce{I^- + H_2O_2 -> I_2}$$
$$\ce{I2 + ascorbic acid -> I- + side products}$$
When the concentration of ascorbic acid is zero, also known as induction period,
$$\ce{I2 + I- -> I3-}$$
$$\ce{I3- + starch -> blue complex}$$
During the first moment I thought that due to the abrupt occurrence of the product, the rate reaction must increase after the induction period. But after doing some research I realized that the occurrence of the product is actually due to the stoichiometric constraint of ascorbic acid.
So, now I think that the rate reaction of a clock reaction decreases over time and that the concentration of products only increases due to the stoichiometric constraint. Is this correct?


texts: Why do the melting points of Group 15 elements increase upto Arsenic but then decrease upto Bismuth?

texts: The boiling points of group 15 elements increase on going down the group (or, as size increases) but the same is not true for the melting points. The melting points increase from $\ce{N}$ to $\ce{As}$ and then decrease from $\ce{As}$ to $\ce{Bi}$. Why is this the case?


texts: Preparation of an aromatic Grignard reagent

texts:
I was tasked with preparing 4-fluorophenylmagnesium chloride from the corresponding aryl chloride. But I've heard that aryl Grignard reagents are very difficult to prepare. I think that the optimal solvent for the reaction would be THF. Any advice would be greatly appreciated!

Also what are the downsides of using magnesium powder instead of magnesium turnings?


texts: Surface-dependency of kinetic in speed law?

texts:
we can comprehend the quantitative dependency of the kinetic of a chemical reaction through the speed law: $v(t) = k \cdot c(...)^k \cdot c(...)^n$

Here I used the concentration $c$ for    that take place in aqueous phases. For the gas phase, I can use $v(t) = k \cdot p(...)^k \cdot p(...)^n $ All is fine, moreover I can convert $p$ into $c$ through $pV=nRT$

But what is with solid-solid reaction? Here the "reaction surface" is the crucial key word. But how can I express this in the speed law which I written above for aqueous and gas reaction? Or is this impossible for solid-solid reaction in this way?

Thank for your answers!


texts:
Why is the pOH of 1 molar HCl 14 in an aqueous solution?

I was learning about strong bases and strong acids in chemistry within this context:

We have 1L of pure water at 25°C, and the pH of water is 7 and the pOH of water is 7, so it is a neutral solution.

Then we add 1 mole of HCl into the water. HCl, because it is such a strong acid, disassociates completely in the water. After some basic calculations, we found that the pH of HCl was 0 and the pOH was 14, but the way he showed this was using the water's pH and pOH - does this make sense?

So we found that the pH of water is 0, and then he did something funny and got a pOH of 14. Why is the pOH of this solution 14?

Here is the video, video mark, 10:02: Khan Academy - pH & pOH of Strong Acids and Bases


texts: Is a metal hydroxide fully or partly oxidised in insufficient base?

texts:
Firstly, my question only applies to transition metal compounds with more than one hydroxide group, otherwise it would be more obvious.
The reason I'm asking is in an effort to oxidise some nickel dihydroxide into nickel oxyhydroxide for practical use in an electrode. I've only come across somewhat laborious methods (any help in this would be appreciated) so I've considered the oxidation like in a NiMH cell (the second equation).
With nickel in a basic solution:
My question could stem from the following situation; If I stir a 2:1 ratio of NaOH:Ni(OH)2 together I would assume the following reaction would be favoured:
$$\ce {4 Ni(OH)2 + 8OH- -> 1O2 + 2 Ni2O3 + 8H2O}$$
But, if I stir a 1:1 ratio of NaOH:Ni(OH)2 and ground the solution:
$$\ce {Ni(OH)2 + OH- -> NiOOH + H2O + e-}$$
*I may or may not be misssing some electrons...I'm just starting out in electro-chemistry.
Is this assumption true? Why or why not? Am I missing the bigger picture? Cue Gibbs?  I did try it, but with the setup I had, I couldn't check for gaseous oxygen, and unfortunately both Ni2O3 and NiOOH are black and powdery.
Similarly with iron in an acidic solution:
In insufficient acid, which one is what would happen and why?:
$$\ce {Fe(OH)3 + H+ -> [Fe(OH)2]+ + H2O}$$ vs.
$$\ce {Fe(OH)3 + H+ -> Fe^{3+} + 3 H2O + excess \,\,\, Fe(OH)3}$$

I guess the question boils down to; How do reduction / oxidation potentials change with multiple individual reduction / oxidations?
I hope everything makes sense. If not I will gladly try to explain my question further.
Thank you for your help!


texts: Calculate the rate of decomposition of H2O2 at 25 °C when [H2O2] is exactly 10.0 mmol/L

texts:
I'm really confused?

$$\ce{2H2O2 -> 2H2O + O2}$$

$$\begin{array}{ccc}\hline
\text{Experiment no.} & c(\ce{H2O2}) & \text{rate} \\
\hline
1 & 14.45 & 3.35 \times 10^{-3}\\
2 & 28.90 & 6.65 \times 10^{-3}\\
3 & 57.80 & 13.35 \times 10^{-3}\\
\hline\end{array}$$

So from previous parts of the question, I found the order of reaction (1st), the rate equation for the reaction ($r = k[\ce{A}]$), the rate constant ($2.3 \times 10^{-4}\ \mathrm{s}^{-1}$, which is correct according to the answers), and now I need to find the rate of decomposition of $\ce{H2O2}$ when $\ce{[H2O2]}$ is exactly $10.0\ \mathrm{mmol\ L^{-1}}$.

I thought it's just $2.3 \times 10^{-4} \times 10.0$, which is $2.3 \times 10^{-3}$, but the answers provided is double that (so $4.6 \times 10 ^{-3}$), so I must have gotten the rate equation wrong?


texts: Must lactose-free milk be ultra-pasteurized?

texts: In this question I asked why lactose-free milk lasted such a long time. The answer was because it is ultra-pasteurized. This leads naturally to another question: does lactose-free milk have to be ultra-pasteurized?My initial guess is that it does because:Since the lactase added to make the product lactose free breaks down lactose into twice as many sugar molecules, any living bacteria have twice as much nutrients to thrive in.Since the disaccharide lactose has been broken down into the simple monosaccharides glucose and galactose, the bacteria do not need to produce their own lactase to use the sugar; thus any non-lactase producing bacteria can thrive in the milk.And finally, I have been adding lactase to regularly pasteurized milk to produce my own lactose-free milk. However, this milk almost always goes bad a couple of days before the Best-By date stamped on the container.This all leads me to think that lactose-free milk must be ultra-pasteurized in order for it to have any reasonable shelf life.


texts: How to calculate the solubility of AgCl in a MgSO₄ solution?

texts:
The solubility product of $\ce{AgCl}$ in water is given as $1.8\cdot10^{-10}$
Determine the solubility of $\ce{AgCl}$ in pure water and in a $0.25~\mathrm{M}$ $\ce{MgSO4}$ solution.

I solve to the $K_\mathrm{{sp}}$ and got $1.34\cdot10^{-10}$
for Part B I was told to use the activity and am not sure if I did it right,
my new $K_\mathrm{{sp}}$ turn out to be $1.123\cdot10^{11}$
could someone help me with part B?


texts: What exactly is happening when sodium, potassium, or other alkali metal explodes in water?

texts:
There are lots of videos on YouTube showing sodium, potassium, etc. exploding when dropped into water (this, for example).

I understand that when an alkali metal is exposed to water, a violent exothermic reaction occurs where a hydroxide and hydrogen gas are produced, but why and how does the sample of metal end up detonating and fragmenting?  Physically speaking, how can a block of metal seemingly blast apart from the inside when the reaction occurs on the surface of the sample?

The Wikipedia article on alkali metals explains this, but I still don't seem to understand how this would result in an explosion.  Diagrams would be very helpful.

The key of the question is how does the release of hydrogen gas and energy result in an explosion?  Is there thermal runaway, and is the metal physically destabilized in some way during the reaction?


texts: Multiple values for the magnetic quantum number and the spin projection quantum number?

texts:
The valence electron configuration of boron is $2\mathrm{p}^1$.

So, $n=2$, and $l=1$. $m_l$ ranges from $-l$ to $l$. Can I say $m_l$ (for the specified electron)
may be (-1 or 0 or +1) or should I just say (-1)?

As you know the $\mathrm{p}$ subshell has three orbitals ($\mathrm{p}_x, \mathrm{p}_y, \mathrm{p}_z$).

Can I associate $\mathrm{p}_x$ with $m_l = -1$, $\mathrm{p}_y$ with $m_l = 0$ and $\mathrm{p}_z$ with $m_l = +1$?
(associate each magnetic quantum number with a particular orbital)

I tried to explain what I meant in the following illustration :

$m_s$ is either $+\frac{1}{2}$ or $-\frac{1}{2}$.
Can I say $m_s$ (for the specified electron) equals ($+\frac{1}{2}$ or $-\frac{1}{2}$)? (both values)
or $+\frac{1}{2}$ because it's alone in the orbital (not paired)


texts: What is the meaning of "more thermodynamically stable surface" when we speak of crystallographic facet formation? For example in wurtzite crystals, the formation of (10-11) surfaces are more favorable than the formation of (20-21). Why? and How? and What is the physical explanation behind?


texts: What are the total amount of resonance structures for these two cations and which is the most stable cation?

texts:
Please see the following two cations.

I have proposed the following resonance structures.

Please let me know if I have missed something.

Thank you.


texts: Mechanism of lithium-halogen exchange of primary alkyl iodide

texts:
On Clayden's page 190 this reaction is given for preparation of organometallics:

What is the mechanism of this reaction? I expected the "almost carboanion" part of the $\ce{t-BuLi}$ to attack as a nucleophile and form a longer 7 membered chain? But instead, that almost anionic $\ce {t-Bu^-} $ has attached to iodine.

I realised that $\ce{t-Bu-}$ is too unstable because of electron releasing alkyls, but what is the exact mechanism of this reaction?


texts: Why is it hard to reduce titanium dioxide?

texts:
Titanium is expensive, although it is not rare and titanium dioxide is a ubiquitous component, it's part of such mundane articles as toothpaste, paper or plastics.

The reason for that is that the processes that extract titanium from titanium dioxide (which occurs naturally and just needs some inexpensive purification) are quite costly. The established industrial method for this is the Kroll process. It works by first chlorinating the titanium to $TiCl_4$ and then moving the chlorine over to some $Mg$, yielding $MgCl_2$ and pure $Ti$. Then follows a costly remelting process under vacuum to further purify the metal.

Recycling titanium scrap is even harder, and removing the other components from the alloys is not entirely possible, so recycling only yields titanium based alloys, not the pure stuff (which is not necessarily a problem since it's very rarely used in its pure form).

What specific chemical properties of titanium make it so hard to purify? For example, the chlorine process at the beginning of the Kroll process takes place with coke in a fluidized bed reactor, very similar to the reduction of $Fe$ in a blast furnace, but if the carbon takes care of the reduction, why is that not sufficient? Why is the chlorine route needed?

Research into titanium production dates back to the late 1880s, and the Kroll process, patented in 1940, made it feasible for mass production, but remains costly and has not been improved upon since, despite much effort. How would a chemist look for suitable reactants during such research?


texts: Is an aqueous solution of calcium chloride hygroscopic?

texts:
Calcium chloride is deliquescent, it is hygroscopic, so much so that it dissolves in the water it has attracted by hygroscopy.

Sulfuric acid is hygroscopic, even if not anhydrous. So a solution containing water can be hygroscopic.

Is a concentrated solution of calcium chloride that was created by the solid salt attracting water still hygroscopic, attracting more water?

If yes - down to which concentration is that the case?


texts: Number of products on dehydrobromination

texts:
Question:

  The total number of alkene products possible from the dehydrobromination of 3-bromo-3-cyclopentylhexane using alcohol KOH is :

This question was asked here before but I am getting more products than those mentioned there

Dehydrobromination of 3-bromo-3-cyclopentylhexane and number of possible alkene products

My doubt is, why doesn't Hydride shift and ring expansion take place here? I would expect the Elimination reaction to be E1 as Br is a good leaving group and it is 3° halide. So there should be a carbocation intermediate on C3.

There is an alpha hydrogen in the cyclopentyl ring wrt this carbocation. Why won't hydride shift or ring expansion into cyclohexane (more stable ring) take place here?


texts: Which alkene on heating with alkaline KMnO4 solution gives acetone and CO2?

texts:
Which alkene on heating with alkaline $\ce{KMnO4}$ solution gives acetone and a gas that turns lime water milky ?

  2-methyl-2-butene
  isobutylene
  1-butene
  2-butene

I know that $\ce{CO2}$ turns lime water milky but, I'm not able to find the alkene in the question. Also, I want the mechanism involved.


texts: Can antimony pentafluoride be made by adding hydrogen fluoride to antimony trifluoride?

texts:
I was looking at how the strongest acid was made and I found something I did not understand. On the Wikipedia page for antimony trifluoride it shows the production of $\ce{SbF3}$ using $\ce{HF}$:
$$\ce{Sb2O3 + 6 HF -> 2 SbF3 + 3 H2O}$$
The page also shows production of $\ce{SbF5}$ using $\ce{F2}$:
$$\ce{SbF3 + F2 -> SbF5}$$
However on the page for fluoroantimonic acid it shows production of:

$$\ce{SbF5 + 2 HF -> SbF6- + H2F+}$$

So my question is why the production of $\ce{SbF5}$ seems to require fluorine insted of hydrogen fluoride? And is it possible to use hydrogen fluoride to make $\ce{SbF5}$?


texts: Doesn't methyl amine give carbylamine test?

texts:
A compound $\ce X$ of formula $\ce{C2H5NO2}$ on treatment with $\ce {HNO2}$
   $(\ce{NaNO2}+\ce{HCl})$ gives off an inactive gas $\ce Y$ and forms $\ce Z$. When heated with soda lime, $\ce X$ gives $\ce{A(CH5N)}$ soluble in acid. Find the true statements :

  $\ce A$ answers carbylamine test.
  $\ce X$ is an amino acid.
  $\ce Y$ is $\ce{CO2}$.
  $\ce Z$ is a hydroxyl acid.

My attempt :

$\ce X$ is glycine.

$\ce A$ is methyl amine.

$\ce Y$ is dinitrogen.

$\ce Z$ is 2-hydroxy ethanoic acid.

Hence, correct options should be : $1,2,4$. But the answer given is $2,4$.

Can anyone help me to understand if and where I went wrong?


texts: Hartree product and the Slater determinant

texts: I am very new to theoretical chemistry so my question may sound very basic to most. It is known that the Hartree product does not satisfy the antisymmetry principle for electrons while the Slater determinant is able to do so. Thus, the electronic wavefunction is often written as a Slater determinant, rather than a Hartree product. However, I am just wondering if the Hartree product can still be used to approximate the electronic wavefunction or if it is still being use to do so in some theoretical methods? And if the Hartree product is used, what other measures are implemented to ensure that the antisymmetry principle is not violated? Also, in Density Functional Theory, which is used to approximate the wavefunction, the Hartree product or the Slater determinant?


texts: given the image on the left, when you look at it from the side would it look like the image in the right? since the thicker lines means it's coming out of the page?


texts: Can sunlight and its heat create a caustic or toxic substance from coconut oil on human skin?

texts:
I heard that story quite often, if it's true, how does it work?

Notice that I’m not talking about using coconut oil as a sunscreen (it’s another topic) but about the action of the sun on the oil and its impact on the human skin: will coconut oil degrade into something toxic under the sun, if so why?

And also, does the same degradation mechanisms applied for other oils (such as olive oil).


texts: Is my understanding of the Frasch Process correct?

texts:
So basically, the whole point of this process is to extract elemental sulfur from underground deposits. Is this process essentially correct or am I missing out certain details?

Firstly, three concentric pipes are placed into the underground sulfur deposit
Then, water that has been superheated is pressurised into the sulfur deposit through the outermost pipes.
The result of the above is melted sulfur stuck in the ground in an emulsion. The pressure of the chamber is also increased (i don't know why?)
To get it out of the ground, compressed air is injected through the innermost pipe: this forces the sulfur-water emulsion to the surface through the middle pipe
When this mixture is cooled, the solid sulfur separates from water and 99.5% pure sulfur is obtained

Is this basically the process? Also, are these the properties of sulfur that this process relies on:

Sulfur has a low density, hence the compressed air is able to lift the sulfur-water emulsion to the surface
Sulfur is insoluble in water and not reactive. Hence, sulfur can be recovered more easily after the sulfur-water emulsion cools as it does not mix with the water, nor react with it.

There are also some problems with this process if I am right:

The hot water used in this process causes thermal pollution, and may also contain some dissolved minerals. This may disrupt the chemical composition of local ecosystems, so one must recycle it.
Depending on the make up of the area, remaining crypts can lead to earth subsidence. These are also harder to refill.
This process releases sulfur, which must be quickly cooled otherwise it oxidises to sulfur dioxide or may be reduced to hydrogen sulfide, both of which are serious air pollutants.


texts:
In GC-MS what are the relative advantages/disadvantages of using Selected-Ion Monitoring (SIM) vs using Total Ion Chromatograms (TIC)?

I know that SIM offers a better S/N ratio, however if the S/N is acceptable using TIC, is it better to use TIC and if so, why?


texts: How can I make the product in the picture below from cyclohexanone? I did Stork enamine synthesis, but it results in terminal primary alcohol. I need secondary alcohol with one more carbon atom at end. How to do that?


texts:
In a question asking to compare the basicity of pyrrole and aniline, the explanation given for aniline being more basic than pyrrole was as follows:

Basicity depends on the availability of lone pair of $e^-$ on Nitrogen atom.
In pyrrole, lone pair of $e^–$ present on $\ce{N}$ are involved in resonance with the ring which provide aromatic character to the ring.
On protonation of pyrrole, the electron will not be above to participate in resonance, While anilines aromatic even though the involvement of line pair of nitrogen of $\ce{—NH2}$ group is not there and lone pair of aniline is delocalized in benzene ring but due to deocalization benzene loss its aromatic character so, the delocalization is not that strong as in pyrole molecule.
Lone pair is more available of protonation. Hence, aniline is more basic than pyrrole.

But, why should the aromatic character get destroyed? It is still a planar structure and should be aromatic. What is an intuitive explanation?


texts: Know any micropipettor that is acid resistant?

texts:
We pipet concentrated nitric and hydrochloric acids. our current pipettor is rainin lite but its piston is metal and thus corrode easily.  We discussed this with our inhouse technician and he suggested a pipettor with a plastic piston.  So do you guys know any?

We try to avoid using filtered tips as we need to leach the tips prior to use.

Thanks


texts: I've been trying to find a  transition state for the reaction of Pd + F2 with no luck. Has anyone ever tried a similar reaction, have they managed to get the TS? The reaction proceeds from the reactants to a linear reactant complex forming a stable PdF2 product (104.4-degree angle).


texts: Chemical consideration of biodegradeability

texts:
We hear the term 'biodegradeability' being thrown around alot in science, but rarely ever is the science itself explained.

What are the chemical properties in a substance that make it biodegradeable?

Furthermore, what exactly are the chemical processes involved in biodegradation?


texts:
(from pg. 1334 of Clayden Organic Chemistry 1st ed.)

In the above reaction catalyzed by Pd, I'm not exactly sure what's going on at the second step. It says in the book that Pd is using its electrons to push out X, and the electrons are returned to Pd when Nu comes and pushes out Pd.

My understanding is that in the first intermediate, the double bond's 2 pi electrons are complexed to Pd. When X leaves, the 2 pi electrons (that are now spread out between 3 C's) are still complexed to Pd. By the drawing of the mechanism, it seems to me that Pd has also used 2 of its electrons to bond with the 3 C's. So in the second intermediate, are the Pd and the allyl cation sharing a total of 4 electrons? If so, shouldn't there be a double bond, not a single bond, from Pd to the allyl cation?


texts:
Polyethylene is a polymer of only carbon and hydrogen.  If 2.300 g of the polymer is burned in the oxygen it produces 2.955 g H2O and 7.217 g CO2.  What is the empirical formula of the polyethylene?

So my method for this problem is
1) find the mass of carbon from CO2
2) find mass of H from H20
3) Find mass of O by subtracting
4) cont. answer with formula from % composition

Therefore:

(7.217 g x 1mole x 1 mole Carbon x 12 grams) /  44g CO2 = 1.96 g
(2.955 g x 1mole x 2 mole Hydrogen x 1g)     /  18g H2O = .328 g

1.96g / 12g = 0.163
.328  / 16g = .0205 (smallest #)

.163 / .0205 = 8 Carbon
.0205 / .0205 = 1 Hydrogen

The answer is CH2 :/, but I am having a hard time finding out where I slipped :(


texts: Is there a way to speed up the formation of para-formaldehyde in a formalin solution?


texts:
Pyruvic acid on reduction with yeast gives (-) lactic acid while with $\ce{NaBH4}$ it reduces to (+) lactic acid. How?

I know this has something to do with stereoselectivity. But I don't know which one would be a correct answer.

It would be more helpful if you could explain a bit about stereo-selective reactions. I know what it is, what I want to know is, how to find which of the products will be stereochemically preferred one, just like in this question.


texts: What is the difference between hydroxyl, hydroxide and hydroxy?

texts: Is there any difference between hydroxide, hydroxyl, and hydroxy used in chemistry or are they all the same?


texts: How am I to interpret the phrase "a solution of acid"?

texts:
The question title is a bit odd, I couldn't find a plainer way of saying it.

I'm given the concentration and conductivity of a solution of a particular acid, let's just call it $\ce{AH}$. I then have to deduce that acid's acidity constant.

My first instinct is to write out the expression for the solution's conductivity... but then I realize I don't know how to do that. I have the coefficients for all the relevant ions (I'm not sure what the technical term is, but essentially I mean the lambdas in the second equation here), in particular, the ions $\ce{H_3O^+}$, $\ce{OH^-}$ and the conjugate base $\ce{A^-}$.

So if I had the concentrations of those ions in the solution, I could solve the problem! But hang on... I have no idea how to figure them out. I know the concentration of the acid in the solution. Suppose the acid has just been added to the water. Then it won't have started to disassociate yet, so the water will be exactly as it was before we added the acid: $[\ce{H_3O^+}] = [\ce{OH^-}] = 10^{-7}$. But what if originally there was a lot more acid, but it's had time to react with the water? Then the water will have been filled with an amount of $\ce{A^-}$ dependent on how long ago the acid was dissolved in it.

Do I assume the acid is at equilibrium? The question doesn't specify that.


texts: How do I display a potential energy surface with molden?


texts: How can an α,β-unsaturated ketone tautomerise?

texts:
I was taught that for aldehydes and ketone to exhibit keto-enol tautomerism, it is essential that there must be at least one α-hydrogen.

For example, acetophenone and butan-2-one show keto-enol tautomerism, but benzaldehyde and benzophenone don't show keto-enol tautomerism, since they don't have any α-hydrogens.

However, I was subsequently told that the cyclic enone 6,6-dimethylcyclohex-2-en-1-one also exhibits tautomerism:

How is this possible? It does not have any α-hydrogens (the vinylic proton cannot be enolised as it is orthogonal to the C=O π* orbital).


texts: How can a nonlinear field gradient be generated in NMR?

texts:
I am working on the topic of optimal control in NMR, where spins undergo non-unitary evolution caused by gradient field pulses at different time intervals. I am studying the effects of this on the spin dynamics.
For my project I need a particular kind of gradient field as given by the equation $-z\exp(-z^2)$, where $z$ is the the spatial position of the region from center of the sample. All the books I had referred to (Levitt's Spin Dynamics and Keeler's Understanding NMR Spectroscopy) talk about constant gradients. So I have no idea if it is possible to create even an approximation of a spatially varying gradient as given here.
In particular, I need my field due to the gradient to look like a delta function in space. So I thought of using a derivative of a Gaussian with a small standard deviation as an approximation, which is the equation given above.


texts: Why are discharge tubes filled at reduced pressure?

texts: Why are the gas sample tubes of hydrogen filled at a reduce pressure when observing hydrogen's emission spectrum? In my HS chemistry lab, we looked at gas sample tubes of hydrogen through a spectrometer and I am wondering why they were filled at a reduced pressure?


texts: Why doesn't NASA or SpaceX use ozone as an oxidizer for rocket fuels?

texts:
Presumably, it would be expensive to use ozone ($\ce{O3}$) as an oxidizer instead of $\ce{O2}$, but would the extra oomph be worth it? Does $\ce{O2}$ provide as much thrust/energy/heat as can be provided, given the liquid hydrogen propellant?

I figured Chemistry was better than Physics, Engineering or Astronomy for this question.


texts: Difference between Oxidation Number and Oxidation State

texts:
I know the theoretical definitions and that they do not defer much, infact these terms are used quite interchangeably.
However, my chemistry teacher once taught me that Oxidation State of an atom in a compound is the average of the different Oxidation Numbers in the molecule. For example, in Acetic acid, the Carbon atom has oxidation numbers +3 and -3, so the Oxidation State of Carbon (i.e. the average) would be 0.
I've stuck by this for long, but yesterday I came across a question the answer to which implies that it is the other way round, as in ON is actually the average of all the OS of an atom. Several sites on the internet quote the same, and other references quote what my teacher taught me, which is the opposite.
What is the right answer?


texts: Ether nomenclature: Oxygens on alkyls and alkyls on alkyls

texts:
Does the ether hold priority over longest chain? If so, my bet would be on:

4-(2-ethylheptanyl)oxy decane

If not, I would say:

4-(octan-2-yl methoxy) decane

Again, if ether takes precedence and not longer chain (which, if you ask me, would be ideal), I'd say:

4-[(1-methyl,2-propylheptan-1-yl)oxy]decane

If not:

4-(ethan-1-yl oxy nonan-4-yl)decane

What is correct?


texts: Purify gas produced after reactions with sulfuric acid

texts:
Say, I preheat 50ml of 98% $\ce{H2SO4}$ and proceed with adding 25ml of 85% $\ce{HCOOH}$.
The result of which is:

$$\ce{H2SO4 + HCOOH -> CO + H2O}$$

Sulfuric acid will dehydrate formic acid producing $\ce{CO}$, however, gas could still be contaminated with vapor. What is the correct way of removing these impurities?


texts: What is the standard heat of formation of the nitrate ion, based on the standard enthalpy of formation of silver nitrate?

texts:
Given the standard enthalpy of formation of $\ce{AgNO3(aq)} = \pu{-99 kJ/mol}$ and the standard enthalpy of formation of $\ce{Ag+(aq)} = \pu{+105 kJ/mol}$, what's the standard heat of formation of $\ce{NO3-(aq)}$?

How can I know this if the standard enthalpy of reaction is not known? This is self test 10.1 in Atkins, PC.


texts: Can I split water without constant refill of solution?

texts:
I've looked all over the place to find a way for me to separate water without needing to put in salt. What I've found is you can separate water into hydrogen and oxygen through electrolysis (which needs salt to make the water conductive), radiation (which I don't want to use - this is a house project that I want to get into), thermal (the water needs to be hotter than what I can provide), and photobiological (looks cool - but it looks like it won't produce much).

There's a lot of things out there for electrolysis water splitting, but every single one looks like it needs salt. Can I initially provide salt to a water splitting machine, then never refill it and still split water? Is there anything else, in which I could put in the water to make it split, and not have to ever refill said thing?

Really, I want to build the machine, and not have to keep providing resources that I'm going to have to get - just provide the machine water and electricity.


texts: Why is nicotinoyl chloride available as its hydrochloride salt? How can we separate them?

texts:
Nicotinoyl chloride is only available as its hydrochloride salt.

Why can't nicotinoyl chloride be synthesized in free form? How can we seperate nicotinoyl chloride from its salt form? Can we try any base for this purpose?


texts: I want to estimate aerosol mass loading by dividing emissions of the particular aerosol by the associated area. Assuming the air had no other particles in it to begin with - is this procedurally correct?


texts: What results from the reaction of pent-3-en-2-ol with hydrogen bromide?

texts:
I have seen the following reaction in my textbook:

This was quite easy to understand, though I wonder why 2-bromopent-3-ene is not a possible result:

Isn't this how $\ce{-OH^}$ groups and hydrogen halides interact? Any clarification would be appreciated.


texts: Specific gravity of H2O2 bleached viscose

texts: What is the specific gravity of $\ce{H2O2}$ bleached viscose? In literature, I can find that this is $1.52~\mathrm{g~cm^{-3}}$, but for bleached viscose is it not findable. Can I presume $\ce{H2O2}$ treated viscose has the same density?


texts: Alcohol or Carbonyl - Which is more reactive towards PCl5?

texts:
We're aware that ketones and alcohols both react with phosphorus pentachloride, to produce geminal dichlorides and alkyl chlorides respectively.

What happens in the compound shown below, when treated with $\ce{PCl5}$? Which group reacts first? (which is to say, what happens if I were to add just one equivalent of $\ce{PCl5}$?)

Please help me out here, I'm not able to qualitatively predict an order.


texts: Reactions between Ca(OH)2 and CO2, and Sr(OH)2 and CO2

texts: So I'm doing an investigation, and it involves using supersaturated solutions of Ca(OH)2 and of Sr(OH)2. I notice that there's always a flaky precipitate formed on top. I need to know about the reactions with carbon dioxide. Is it carbonate that's formed? Or is it hydrogen carbonate? Why?


texts:
I was asked to determine the coordination compound which has the name:

$$\text{triamminetrinitritocobalt(I)}$$

I thought it must be: $$\ce{[Co(NH3)3(ONO)3]^2-}$$

The $-2$ charge can be deduced by adding up the oxidation numbers.

However, in this case, shouldn't the name be written as cobaltate instead of cobalt? Where is my mistake and what did I miss here?


texts: Why is it that lighter atoms are more likely to produce Auger emission and the heavier atoms fluorescence in x-ray spectroscopy? It doesn't make any sense. Lighter atoms should try to resist double ionization, plus there are fewer electrons around which means there is a lesser chance of a photon hitting an electron.


texts:
A reaction I am trying to perform says to use a strong base like Sodium Amide with Acetone and Iodo-Benzene as reactants with DMSO as the solvent to form Phenylacetone. The main idea is to use the Acetone Enolate to form Phenylacetone when the Halogen is removed from the Halobenzene.

Can I just put NaOH in Acetone with a Halobenezene?


texts: Why does lithium aluminium hydride appear grey?

texts:
Commercial lithium aluminium hydride is a grey compound, which loses a lot of reactivity the darker it is. Luckily you can clean it up to get the reactive white compound and the separated grey contamination. Over some time, however, it is said to slowly convert back to the grey form (at least this is what I read, I haven't watched clean samples turn grey again yet).

My question is, what is this contamination? I remember to have heard somewhere that it may be elemental aluminum, which forms by decomposition. And in fact, the thermal decomposition really yields aluminum as a side product. But I cannot find any reliable source I could quote for my thesis. Does anyone have a paper or book that actually mentions the grey contamination?


texts: Coordination Numbers and Hybridization schemes of anions

texts:
Draw the molecular structures of

  (a) the borax anion, $\ce{[B4O5(OH)4]^2-}$

  (b) the peroxoborate anion, $\ce{[B2(O2)2(OH)4]^2-}$

          borax                    peroxoborate

  (i) What are the co-ordination numbers of the $\ce{B}$ and $\ce{O}$ atoms in the anions (a) and (b)

  (ii) What are the hybridisation schemes used by the $\ce{B}$ and $\ce{O}$ atoms in the anions (a) and (b)

I: For (a) $\ce{B}$ has 2 four-coordinate ($\ce{BO4}$) and 2 three-           coordinate atoms ($\ce{BO3}$).I'm assuming $\ce{O}$ is 0 since its not a central atom.  , (b) $\ce{B} = 4$ and again I'm not sure but I thought coordination numbers only applied to one atom in a molecule. In this case the boron atom.

II: For (a)  $\ce{B}$ has 2 $sp^3$ hybrid orbitals and 2 $sp^2$ hybrid orbitals, $\ce{O}$ has just $sp$  orbitals. , (b) $\ce{B}=$ has just $sp^3$ orbitals and $\ce{O}$ has $sp$ orbitals.

I would just like some clarification on the coordination numbers of the $\ce{O}$ atoms in both anions and to see if my hybridisation schemes are correct.


texts: 'In MO theory, electrons are treated as spreading throughout the entire molecule'- isn't it exhibited in VB theory also?

texts:
First statement:

  In the molecular orbital theory, the valency electrons are considered to be associated with all the nuclei in the molecule. - Concise Inorganic Chemistry by J.D.Lee.

Second statement:

  In molecular orbital theory, electrons are treated as spreading throughout the entire molecule: every electron contributes to the strength of every bond. - Elements of Physical Chemistry by Peter Atkins.

Two different sources are actually saying the same thing in regard to MO theory: electron density is spread over the entire molecule, okay that is quite right & agreeable.

But the way the fact is presented as if it were the sole property of MO theory. Doesn't the electron density span over the entire molecule in VB theory also?

Check this pic taken from Peter Atkin's above mentioned book:

This is the electron density in $\ce H_2$ as predicted by VB theory; notice how the resultant wavefunction after bonding is spread over the entire molecule & this implies the electron density is spread over the entire molecule. So, even in VB theory, the electron density is spread over the nuclei of the molecule. So, why those special writings above?

Why is it that the spreading of electron density over the nuclei of the molecules specially in MO theory? Is not this exhibited even in VB theory also? Or am I missing something?

Can anyone please help me whether the spreading of the electron density is the sole property of Mo theory as is put up by the two authors? Is not it exhibited in VB theory also?


texts:
If I add sodium percarbonate to my natural laundry soap recipe, can I still claim "No Artificial Anything"?
I know it's used in many "natural" products, but is it considered an "artificial ingredient"?
I don't want to make any false claims with my product.

thank you!


texts:
An experiment from Vogel that I want to conduct requires "a mixture of ice and salt of about -10 °C". Reading trough the text it appears that I need at least 1-2 liters of this. Obviously the salt is added to lower the freezing point of the water. I guess the interaction of water with the dissolved salt trough hydrogen bonding / lone pair donation is more favorable (less energetic) than ordinary water-water interaction.

With "salt", does Vogel mean just $\ce{NaCl}$?
Since I'm a hobby chemist I do not have the same fancy machinery as they have in the lab (those cool things that generate rough ice shards and in which everybody stuffs food against all safety regulations lol). All I can use is a small refrigerator with a tiny freezer. It's easy enough to make some ice cubes, but how do I go about making these ice shards that are used in the lab? I don't think grinding the cubes is very practical as it is a tedious job that takes a lot of time in which the shards have probably already melted (also from hitting them with a pestle continuously)...


texts: What current and voltage are best for electrolysis rust removal?

texts:
I weld carbon steels all the time, and sometimes I get parts from the scrapyard. Unfortunately, these parts are generally oxidized, so I've been assembling an electrolysis tank for it. This tank removes the oxidation in about a day. I'm getting the feeling that I can make it go faster if I step up the current or voltage. What combinations of currents or voltages would make the fastest method of removal?

NOTE: I'm familiar with the risks of doing electrolysis, including hydroxy production, and the restriction on stainless steel electrodes.


texts: Raman Scattered (inelastic) photons rescattering outside of capture area

texts:
Imagine that you are focusing the raman laser right at the center of the vial sample with water (or any liquid) using 532nm laser.

(from "Photometric Standards for Raman Spectroscopy)

For raman 180 degree backscattering sample geometry, can the inelastic scattering photons upon travel to the spectrometer becomes elastically scattered on way to it by the thick liquid sample such that it is scattered outside the area?

If yes, does it mean it is better not to focus so deep into the sample so the return path would be less (that is focusing the raman laser just after the glass on the liquid sample)? The side effect of this is getting some raman noises from the glass itself.


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

So the question is:

What are some of the techniques of combining oxides to obtain desired major phase?

Online/book references or paper citations are also welcome apart from your valuable answers.


texts: Why does phosphine reduce HgCl2 to Hg but LiAlH4 / LiH reduces it to Hg2Cl2?

texts:
Why does phosphine reduce $\ce{HgCl_2}$ to $\ce{Hg}$ but $\ce{LiAlH4}$
  or $\ce{LiH}$ reduces it to $\ce{Hg2Cl2}$ ?

It seems phosphine has more reducing tendency.But why?

Moreover can it be predicted whether a reducing agent will be reduce $\ce{HgCl_2}$ to $\ce{Hg}$ or $\ce{Hg2Cl2}$ ?


texts: Whats the difference between ionization energy and orbital energy?

texts: If you look at the trend in orbital energies as you go across a period the pattern is clear (orbital energy decreases with increasing effective nuclear charge) and, to my knowledge, it has no anomalies like the trend in ionization energies does when a 2p orbital is filled for the first time with two electrons (when this happens the ionization energy decreases). I expected that the graphs for ionization energy would be mirror images in the x-axis given that orbital energies are negative and measured relative to an ionized electron (which equals 0) albeit with different y-scales because ionization energy is the energy to ionize a mole of a substance in a gaseous state. Is my understanding that orbital energy = -(energy required to remove one electron from that shell) incorrect? Fundamentally, the question is, why doesn't the trend in orbital energies mirror the trend in ionization energies?


texts: Why are potassium organic salts ever preferable to the sodium equivalents?

texts:
$\ce{KOH}$, $\ce{KCN}$, $\ce{KNO3}$, $\ce{K2CO3}$, and plenty of other potassium salts are frequently used in industry.  But, as far as I can see, the sodium equivalents are also widely used, often interchangeably.  Since Na weighs only 60% of K it seems like the sodium salts should always be preferred because they carry more of whatever base is attached per unit weight (i.e., the sodium salts have "more of what you want"). $\ce{Na}$ is also slightly more abundant (on earth) than K.

So what other factors favor the industrial use of K-salts?  E.g., are K-salts just more abundant in natural sources?  Are they more reactive because the ionization energies of K are lower than those of Na?  Are the behaviors of these simpler salts actually different between the K- and Na- variants, and if so, is there some other elemental characteristic that suggests this?

Going the other way, it seems like if K is preferable to Na, Rb should be even more so (because it appears that in every elemental characteristic in which K exceeds Na, Rb exceeds K).  Would it be if it weren't so relatively scarce?


texts: Confusion about comparing the charge densities of benzene and fluorobenzene

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I understand that the functional group $\ce{-F}$ is an electron-withdrawing group. It is expected that the difficulties of an electrophile to attack the carbon atoms are $$\ce{PhH}<\ce{2,4of PhF}<\ce{3 of PhF}\tag{1}$$Therefore, I want to demonstrate it quantitatively by computing the charge densities of carbon atoms.
Using command # opt freq hf/3-21g pop=nbo geom=connectivity
and the molecule models in Gaussian 09,
I obtained the charge densities of $\ce{PhH}$ and $\ce{PhF}$. To my surprise, the result is:
$$\begin{array}c\text{molecule}&\text{ortho}&\text{meta}&\text{para}\\\ce{PhH}&-0.239&-0.239&-0.239\\\ce{PhF}&-0.306&-0.222&-0.261\end{array}$$
By observing this result, the fact that the electrophilic substitution of $\ce{PhF}$ is likely to occur in o- and p- is verified, or the right half of $(1)$ is verified.

  But why would the charge density of position 2,4 of $\ce{PhF}$ is more negative than that of benzene, given the fact that $\ce{-F}$ decreases rate of the electrophilic substitution reactions?

My speculation
i) $(1)$ may be false.
ii) The NBO charge densities between two different molecules cannot be compared.
iii) The charge density cannot indicate the difficulty of the attacking of electrophile.

Which one, or something else, can explain this strange observation? Can another method to order electron-withdrawing ability of some functional groups computationally be suggested?


texts: What determines the boiling point of esters of the same number of carbon atoms but different structural formula?

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The boiling point of esters increases with molecular weight (and therefore, number of carbon atoms) because of more dispersion forces.
But if you had two different esters with the same number of carbon atoms but different structures (e.g. methyl-ethanoate and ethyl-methanoate), what determines which one will have a higher boiling point?
Does it have something to do with the number of carbon atoms in the alkyl group in comparison to the acyl group?


texts: What is the purpose of the solution in a galvanic cell?

texts: In other words: What is the purpose of the solution that the electrodes are immersed in, in a galvanic cell, and is it possible to generate a current without any solution?


texts: In this simple redox reaction, why does the Hydrogen oxidize the calcium metal?

texts: I am understanding that the Hydrogen ions oxidize the calcium metal, neutralizing itself and creating a calcium cation. My question is why does the Hydrogen oxidize the calcium? Doesn't it prefer to have an empty outer shell? Does it want more to be neutral or to have an empty outer shell?