texts: Reactant energy distribution and spontaneity of reactions

texts:
I wonder about the implications of substances having an energy distribution around a mean, as opposed to them all having the same energy level, on the spontaneity of reactions.

2 somewhat separate questions:

Can a reaction with a high activation energy, but which in the end has a negative Gibbs free energy change at certain temperature, occur spontaneously even though at this temperature the energy level of the reactants is lower than the activation energy? If I understand correctly, the answer would be yes because the energy of the reactants is just an average of a broader distribution, and so some small fraction of the reactants would attain the $E_a$ even if on average $E_a > E_{\text{reactants}}$?
Wouldn't it also be possible that some non-spontaneous reactions (with a positive change in Gibbs free energy) occur spontaneously? I mean we know that if we invest $\Delta G$ energy, we will force the non-spontaneous reaction to occur. But what if some small fraction of the reactants get to the energy level they would have had if $\Delta G$ energy was invested in them (without it being actually invested). Wouldn't that mean that for that fraction of the reactants, in the high end of the energy distribution around some average, the reaction would occur (while not occurring for the rest and vast majority of the reactants who fail by themselves to attain the same energy level they would have had if ΔG energy were invested in them)? Is there a flaw in this understanding?

I guess the question here is whether the idea that $\Delta G > 0$ reactions are non-spontaneous is a statement of probability that says that such reactions are just very unlikely or is it an hard and fast rule like the conservation of energy?


texts: Reaction of Silicon monoxide with alcohols

texts:
Elements from the carbon group tend to form compounds with two oxygen's. Let's say I want to produce $\ce{SiO_2}$ out of $\ce{SiO}$ by mixing it with some alcohol, for example:

$$\ce{SiO + CH_3-CHOH-CH_3 \longrightarrow SiO_2 + CH_3-CH_2-CH_3}$$

Is this likely to occur? at least before all the alcohol evaporates...


texts: Why do the d orbitals have these notations?

texts: Why do the d orbitals have the following notations: $xy, yz, xz, z^2$ and $ x^2-y^2$? What do they represent in their wave-functions?


texts: What does "at%" refer to in sol-gel method?

texts: I'm reading on the preparation of ZnO thin films for UV stimulated emission and I found a method called Sol-Gel. During this I found a paragraph saying, " the ration Ag/Zn in the sol is 3 at%......". so I want to know what at% refer to.


texts: Which of the following compounds were involved in the titration?

texts:
We have a sample that weighs $\pu{0.3148 g}$.This sample may contain one,two or even three of the following compounds: $\ce{NaOH, Na2CO3, NaHCO3}$. We have as a clue, that the sample was titrated with $\pu{20 mL}$ $\ce{HCl}$ $\pu{0.09 M}$ using phenolphthalein as an indicator. Later, the sample was titrated with $\pu{50 mL}$ of the same $\ce{HCl}$ using orange methyl as an indicator.

The question is how do we understand which of the compounds were involved? Should we set for example mass of $\ce{NaOH} = x$, mass of $\ce{Na2CO3} = y$ and mass of $\ce{Na2CO3} = z$, then write down the reactions between all of the compounds with $\ce{HCl}$ and then extract some equations from the equivalent point? One equation comes from the total mass.


texts: Gas spectra in the 400 nm - 1000 nm range

texts:
Disclaimer: My background is computer science.

Is it possible to detect any gas using a visible light and near infrared (400 nm - 1000 nm) hyper spectral imaging camera? This can be related to gas leaks, pollution, gasses released in fires... From what I found when googling, this is not really possible, but I though to check here to be sure.


texts: How do I increase the amount of electrons transferred in a battery?

texts:
I made a simple battery with $\ce{Al}$ as anode electrode with $\pu{0.7 M}$ aluminum sulfate electrolyte. Platinum is my cathode electrode with $\pu{2 x 10^-4 M}$ $\ce{KOH}$ solution. I am generating $\ce{85 mA}$ (my cell produced $\pu{0.04 V}$ under a $\pu{47 \Omega}$ load). How can I increase amount of electrons to increase the current produced by my cell?

My half cell reactions are
\begin{align}
\ce{2Al &-> 2Al^3+ + 6e-}\\
\ce{3H2O + 6e- &-> 3H2 + 6OH-}
\end{align}


texts:
I am trying to extract chitosan from crab shell (Japanese snow crab). I want to dissolve chitosan in water and mix in gelatin to obtain some type of gel, that I would then test for my Master 2 Architecture thesis.
However, because I am from an architecture background I am having a hard time to understand the process of chitosan extraction.

I got 1M $\ce{HCl}$ (500 mL) and 1N $\ce{NaOH}$ (500 mL). We gathered around 3 kg of crab shell. I am following the guide of two researchers (here and here), but I can't really understand what they mean in terms of percentage, and dosage of the acid.

Could you please help me in very simple terms?
What does the percentage relate to (solute and solvent)?
Do I need to add water with the acid I have and then mix it with the shell?


texts: What happens to minerals once you boil off liquid in a water and fat mixture?

texts:
Let us say you are cooking a curry.  As water evaporates the minerals will become more and more concentrated in the curry's water but they will not deposit in the fat which would be at the top layer of the liquid. Regarding the minerals not depositing in the fat whilst water exists, is this correct?

Once you have evaporated all of the water which I imagine happens before any fat starts evaporating, would the minerals then deposit in the fat?

Is there a way to know by observation that water has evaporated and you are left with minerals and fat?


texts: Are benzyl alcohol and o-cresol functional isomers or position isomers?

texts:
My textbook categorizes them as functional isomers (phenol and aromatic alcohol) whereas

The above mentioned isomers are given as position isomers on 'chemguide.co.uk'


texts: Is KHF2 an ionic compound or a covalent compound?

texts:
The statement below is an excerpt from my school textbook:-

  Because of the tendency of fluorine to form hydrogen bond, metal
  fluorides are solvated by $\ce{HF}$ giving species of the type $\ce{HF2-}$ like in $\ce{KHF2(KF.HF)}$. Also,  because of hydrogen bonding, $\ce{HF}$ dimerises to $\ce{H2F2}$ and exhibits dibasic nature and forms acid salt like $\ce{KHF2}$ on reacting with $\ce{KOH}$ whereas $\ce{KHCl2}$ does not exist because chlorine does not form hydrogen bond.

But since $\ce{K+}$ is a cation and  $\ce{HF2-}$ is an anion, it can easily form the ionic bond $\ce{K+HF2-}$. So, is KHF2  an ionic compound $\ce{K+HF2-}$ or a covalent compound $\ce{KHF2(KF.HF)}$?


texts: Minimum resolution to acquire exact mass on a spectra from m/z peak

texts: I'm having a little difficulty with finding what the minimum resolution required to obtain the exact mass of a 400 $m/z$ peak in a mass spectrum. I would appreciate any help.


texts: Does the order of a written redox couple matter?

texts:
My understanding is that a redox couple is an unordered pair of two conjugate species. So we could speak of the redox couple consisting of $Ag$ and $Ag^+$; depending on whether a given redox couple is undergoing oxidation or reduction, we could then write a half equation involving the species given in the redox couple.

In my textbook, it is given as a convention that all redox couples are expressed in the form Ox/Red. So for instance, it states "at anode containing the $Zn^{2+}/Zn$ redox couple, the oxidation half equation is $Zn \rightarrow Zn^{2+} + 2e^-$". This convention makes sense to me, since it doesn't seem that the couple itself refers to a half equation in a given direction. The order of the half cell line representation, however, does change the order to $Zn | Zn^{2+}$.

However, some texts reverse the order of the written redox couple, which I would interpret as either them writing the couple in the order of the current half equation (which seems wrong) or that they are ignoring the order because it is unimportant.

So I wondered whether anyone could clarify, is a redox couple just a pair of species which exist at a given half cell, or do we need to change the order of the written couple depending on the reaction occurring at that half cell?


texts: How to calculate the number of skeletal electrons

texts: The number of skeletal electrons in CH is 3 and the number of skeletal electrons in BH is 2. How


texts: How to use a spectrometer to determine NPK

texts:
I'm trying to determine if it's possible to use a low-grade spectrometer to read NPK values of a solution.

I believe I should be able to take readings of the individual compounds (e.g., calcium nitrate) and then use that to "subtract" from a reading of the mixed/final solution and basically deduce how much of each compound is present - is that correct?


texts: Which are the Geometrical isomers of the complex [Cr(NH3)2Cl2(en)]+?Is it one or two?

texts: I was recently studying coordination compounds and i came across optical isomerism shown by complexes.I think that the complex i gave above have 4 geometrical isomers(I think this is where I am wrong, that it only has three geometrical isomers),but among those four geometrical isomers,how many of them are optically active?.According to what i studied only two of the three geometrical isomers should be optically active,other two having plane of symmetry(I am not too clear about the plane of symmetry concept),but all  the solutions i looked up for the question said the complex only have 3 Geometrical isomers.Where am i wrong?.Is it that among the four geometrical isomers, two geometrical isomers are same?,if yes then how?


texts: Can butane-2,2,3,3-tetraol be oxidized by potassium permanganate?

texts: Can the compound butane-2,2,3,3-tetraol, $\ce{C4H10O4}$, be oxidized by $\ce{KMnO4}$? If so, in what conditions? As I have learnt in class, normally the hydroxy group would oxidize to form a ketone, but what about this particular case?


texts: Does a red hot metal reflect light in the same way as a cold metal?

texts: I know that a metal at room temperature looks shiny because of the free electrons on the surface, but what about a hot red metal? Would it also reflect light in the same way as it does at a colder temperature? Even if it emits some red light due to it being hot?


texts: How this tricky Wagner-Meerwein rearrangement occurs?

texts:
In 1979, Karel Frantisek Wiesner performed a tremondous total synthesis in $59$ steps of the 13-desoxydelphonine. In one of those steps there is a very tricky Wagner-Meervien rearrangement. I tried to find something by myself, I also look on the net, I found this and you can see page $8$ they have the same problem than me.

What is the mechanism of this rearrangement ?

Just to be a bit more clear, the acetate which looks to appear magically obviously don't, it comes from the previous step because of the solvant, they just heat several days after so the solvant is still the same as you can see in the picture below.

If someone has an idea, I would be glad! Thank you in advance :)


texts: Calculating Ratio of Stability Constants

texts:
Solution I contains a mixture of $\ce{FeCl2}$ and $\ce{FeCl3}$, and solution II contains a mixture of $\ce{K4Fe(CN)6}$ and $\ce{K3Fe(CN)6}$. The concentrations of iron-containing species satisfy the relations $[\ce{Fe^2+}] = [\ce{Fe(CN)_6^4-}]$ and $[\ce{Fe^3+}] = [\ce{Fe(CN)_6^3-}]$. The potential of platinum electrode immersed into the solution I is $0.652\ \mathrm{V}$, while the potential of platinum electrode immersed into solution II is $0.242\ \mathrm{V}$.
Standard redox potential for $\ce{Fe^3+ + e- -> Fe^2+}$ is $0.771\ \mathrm{V}$
Calculate the ratio of the stability constants $\beta [\ce{Fe(CN)_6^3-}] / \beta [\ce{Fe(CN)_6^4-}$]

My attempt
First I wrote out the Nernst Equation for both reactions:
$$0.652 = 0.771 - 0.059 \times\mathrm{log}\ce{ \frac{[Fe^2+]}{[Fe^3+]}}$$
$$0.242 = \mathrm{E_{cell}^\circ} - 0.059 \times\mathrm{log}\ce{ \frac{[Fe(CN)_6^{3-}]}{[Fe(CN)_6^{4-}]}}$$
Also I wrote out the expression for the ratio of stability constants"
$$\frac{\beta _1}{\beta _2} = \ce{ \frac{[Fe(CN)_6^{3-}][Fe^2+]}{[Fe(CN)_6^{4-}][Fe^3+]}}$$
Now I know that the ratio is just the sum of the 2 logs in the Nernst equations that I have wrote above. However I am not sure how to calculate the $\mathrm{E_{cell}^\circ}$ for the second reaction. Can we assume that $\mathrm{E_{cell}^\circ}$ for the second reaction also equals $0.771\ \mathrm{V}$?
The answer is $8.90 \times 10^6$
Any help is greatly appreciated.


texts:
My book states that $\ce{2AgNO3(aq) +Cu ->Cu(NO3^-)2(aq) +2Ag(s)}$. In addition to the formula, it also shows the following image:

As in the image it shows the salmon colored copper atoms are donating an electron to the $\ce{Ag+}$ ions. In the 2nd picture on the page it shows the $\ce{Ag}$ atoms on top of the salmon colored copper atoms. I would assume that the $\ce{Cu}$ and $\ce{Ag}$ form somewhat of an ionic bond, is this correct to say? If that is the case, why does the formula not indicate a bond between the copper and silver instead the overall product is just copper nitrate plus silver. I would think it would be something like $\ce{CuAg}$?


texts: Why does water spills on our shirt change its colour?

texts: While drinking water, some of it spilled on my shirt and as usual, as has happened to many of us, the colour darkened. So why does this happen? Is it due to some chemical effect or physical one?


texts:
From wiki page about valence electrons:

An atom with a closed shell of valence electrons (corresponding to an
electron configuration $s^2p^6$ for main group elements or $d^{10}s^2p^6$ for
transition metals) tends to be chemically inert.

My question is, which are the transition metals with $d^{10}s^2p^6$? Looking at the periodic table, I do not see anyone.
After this paragraph, wiki says that valence orbitals for d-block elements (transition metals) are (see table):

ns (n-1)d np

I though one of the characteristics of transition metals is that they do not have electrons in last p orbital.


texts: Why is HCl the acid of choice for swimming pools?

texts: Why is muriatic acid the go to acid to put into pools? Does it work better than nitric acid, sulfuric acid, or another strong acid? I mean they all will add the same amount of H+ right? Note, we use some cyanuric acid as well, but mainly HCl for adjusting pH.


texts: How does localized bonding theory and hybridisation work?

texts:
So I understand molecular orbitals and how to do VSEPR models, but I seem to be struggling with understanding localized bonding theory and how to do hybridizations.  After drawing the initial lewis structure then molecular orbital, I do not know where to go in terms of whether something has a $\pi$ or $\sigma$ bond.
Also, how do I know when an atom has a carbon attached as an extra sigma bond or not? I understand how to know if it is $\mathrm{sp}$, $\mathrm{sp}^2$, etc. but I do not know what that means.


texts:
What is the fundamental argument behind explaining why Ta metal is so inert and does not usually participate in corrosion? I know that it forms a protective oxide, but nothing explains why in an acidic solution it is resistant to nearly everything (aside from HF). I want to know if it has to do with a bond strength of the metal or the molecular orbitals.
An in-depth citation is required.


texts: How does aminoguanidine interfere with the formation of advanced glycation endproducts?

texts:
This says that aminoguanidine interferes with the formation of advanced glycation endproducts (AGEs) through interacting with 3-deoxyglucosone.

But how does it interact with 3-deoxyglucosone that prevents AGE formation?


texts: How are SN2 transition states stabilised by adjacent double bonds and carbonyl groups?

texts:
It is my understanding that transition states in an SN2 reaction have some filled and some empty orbital character, as we have the backside of the C-X σ* beginning to fill with electrons from the HOMO of the nucleophile, forming a C-Nu σ bond in the process.

If we have an adjacent carbonyl group to the α carbon, I have learnt that the TS is then only stabilised by the  C-O π*, i.e. by electron withdrawal and not by the C-O π.

However, with adjacent double bonds, I have learnt that the TS is stabilised by both the C-C π and the C-C π*.

I was wondering why this would be the case, as looking at the shape of the orbitals, there seems no reason that the C-O π could not align itself so that the partly-empty p orbital in the TS is parallel to the lobes of this MO, therefore stabilising the TS as new lower energy MOs form.

Also, with regard to the best representation of these structures, I always see partial negative charges on the Leaving group and the Nucleophile in the transition state, but never the positive charge located on the α carbon. Surely if with adjacent carbonyl groups we only have stabilisation by electron withdrawal, it is valid to put the partial positive charge there?


texts: Jamming Theory or DLVO Theory for Oobleck

texts:
After doing some research I came across two theories that explain the shear thickening effect of Oobleck.  The DLVO theory which involves the suspension of molecules via two opposing forces [attractive (Hamker/Van de Waals) and repulsive (electrostratic)].  When a force is applied the attractive force (which reigns over smaller distances) temporarily overcomes the repulsive electrostatic forces.  This causes the particles to clump together and the mixture takes on properties of a solid. My question is which theory is the correct one in the case of oobleck.  The Jamming theory states that the sudden application of pressure, displaces the water that the starch molecules are suspended and move freely in.  This causes that particle to "jam" together (due to the low pressure zone created) effectively locking them in place.  This temporarily results in the oobleck becoming a solid.

**I know the description of the DLVO theory is quite watered down but I just wanted to speed up the answering process (if that's even possible) More info on DLVO Theory


texts:
The beryllium ion, $\ce{Be^{2+}}$, forms the aquo complex $\ce{[Be(H2O)4]^{2+}}$. According to LibreTexts, this complex is acidic in solution: $$\ce{[Be(H2O)4]^{2+} + H2O -> [Be(H2O)3OH]+ + H3O+}$$
It is not clear to me why it should be acidic. I read here that "the hydrolysis happens because the $\ce{Be−O}$ bond is very strong and so in the hydrated ion this weakens the $\ce{O−H}$ bonds hence there is a tendency to lose protons."
I have two questions:

What is meant by a "very strong" $\ce{Be-O}$ bond? Is it stronger than those in other metal aquo complexes? If berylium's tendency to hold on to water ligands is unusually strong, is it due to its small ionic size?
Why does a strong $\ce{Be-O}$ make the $\ce{O-H}$ bond weaker? I know that oxygen forms a coordinate bond with metal cation so the electrons in the $\ce{O-H}$ bonds would get shifted towards oxygen. But as far as I can tell this only makes the $\ce{O-H}$ bonds more polar. Why does a polar bond have to be a weaker one?


texts: What are the chemical similarities between gallium and barium?

texts:
I am analyzing nutrient concentrations in wood, and I have found that in all my samples the distribution of gallium and barium are closely related. As a related phenomenon, the presence of these elements also sometimes correlates to that of another pair of nutrients, calcium and strontium, but not always. For example, in samples from a humid site $\ce{Ba}$, $\ce{Ga}$, $\ce{Ca}$ and $\ce{Sr}$ are always closely related, but in samples from a dry site $\ce{Ba}$ and $\ce{Ga}$ remain correlated to each other, but are generally not strongly correlated with $\ce{Ca}$ and $\ce{Sr}$.

I would like to know what aspects of their respective chemistries might cause $\ce{Ga}$ and $\ce{Ba}$ to have this strongly correlated relationship in wood samples.  For example, is there some sort of similarity in how their valence electrons participate in bonding?


texts:
What software / webservice can one use to find a compound that has similar 3D structure/dimension to another compound?

eg. say we are tying to find a 'better' version of atropine, so naturally we try to find compound with similar 3D structure to Atropine (antimuscarinic)

and 3d structure of atropine (and all other drugs) is available

so what software can we run to search 3d shape look-alike of atropine among all available 3d structures ?

similar shape and size for starter?


texts: Is it possible to calculate the momentum of an electron precisely?

texts:
In a national level, undergraduate examination (TIFR-2018) following question was asked:

Which of the following is not correct with regard to the uncertainty principle?

An electron in an atom cannot be defined by a well-defined orbit.
The momentum of an electron cannot be measured exactly (correct answer)
A harmonic oscillator possesses a zero-point energy
Measurement of one variable in an atomic system can affect subsequent measurements of certain other variables

In my view answer should be (4). My explanation:
To calculate an electron's momentum precisely, it must have a totally undeterminable position! Since our apparatus have some definite size, you have to confine it in some definite space.
$$\Delta x \Delta p \geq \frac{\hbar}{2}$$
Since we want to make $\Delta p$ to approach zero, $\Delta x$ must approach infinity, which is not possible. So we can't measure the electron's precise momentum. So option (2) shouldn't be the answer.
Moreover, as far as I know, Heisenberg's uncertainty principle restricts us from measuring two quantities(which doesn't commute each other) simultaneously. We can measure them subsequently (one after another). So option (4) should be the answer.
P.S. I know that it is not necessary that we will get the same measurement on repeating the experiment, we can get any of the eigenvalues of that observable. But this is not related to Heisenberg's uncertainty principle. It's related to observer's effect.


texts: Reason for enthalpy being non-zero at constant temperature

texts:
Suppose a reaction is occuring at constant temperature. Then $\mathrm dH=nC_{p}\mathrm dT = nC_{p} × 0=0$.

Please explain what the mistake is that I have done. Clearly, there are many reactions which take place at constant temperature and have a definite enthalpy change. But according to the equation $\mathrm dH=nC_{p}\mathrm dT$, if temperature $T$ is constant then $\mathrm dT =0$ and $\mathrm dH = 0$. But this is clearly not true. There are reactions with constant temperature and $\mathrm dH≠0$. Please explain what is wrong?


texts: Competition between substitution and elimination (uni- or bimolecular)

texts:
Whats is/are the main product/s of the following reaction:

I think the main product would be the one obtained by $S_N2$, and then the one pair of enantiomers obtained by $E2$. Is $E1$ with subsequent rearrangement possible?


texts: Can any solute be used to lower the freezing point of water?

texts:
Let's say I want to lower the freezing point of water by 5 degrees Celsius.
I know that for a fixed volume of water, I will need $x$ moles of solute to do so.

Because freezing point depression is a colligative property, does that mean I can use any solute to lower the freezing point of water as long as the molality of the solution is maintained, or are there other properties of the solute that need to be considered?


texts:
I am trying to sputter $\ce{Nb}$ on $\ce{SiO2}$ Z-Cut wafers (quartz crystal).  I was wondering if $\ce{Nb}$ will stick well to the surface of the wafer.

I've routinely deposited $\ce{Nb}$ on $\ce{Si}$ wafers but have never done so on quartz crystal wafers.


texts: Buffers: what does the strong base react with?

texts:
I am a bit confused on buffers:
If I have a solution with a weak acid (say $\ce{NH4}$) and its conjugate weak base ($\ce{NH3}$), I have a buffer solution (in $\ce{H2O}$).

  $$\ce{NH4 <--> NH3 + H+}$$

But now If I add a strong base to my solution ($\ce{OH-}$ for example) I get that my pH will go up but I don't understand the dynamics of it.

Will my added $\ce{OH-}$ react with the weak acid $\ce{NH4}$ (more $\ce{NH3}$ produced)?

$$\ce{NH4+OH -> NH3 + H2O}$$

OR will my added $\ce{OH-}$ react with the $\ce{H+}$ produced by my weak acid (Less $\ce{H+}$ produced)?

$$\ce{NH3 + H+ (products of $\ce{NH4}$) + OH- -> NH3 + H2O}$$

I understand that both cases up end up with the pH going up but but I want to be sure to understand with what exactly my $\ce{OH-}$ molecule reacts once added to my solution.

Is it the $\mathrm{1^{st}}$ reaction which means more $\ce{NH3}$ produced?

Or is it the $\mathrm{2^{nd}}$ reaction which means less $\ce{H+}$ produced?


texts: How to recast Henderson–Hasselbalch when fitting data on a chemical shift vs. pH graph for NMR

texts:
I've just been getting into organic and been reading about H-H related to $\mathrm{NMR}$. I've been seeing articles state how recasting of H-H is necessary and want to know how equations like below are derived.

$$σ_\mathrm{peak} = σ_\ce{HA} + \frac{Δσ}{1 + 10^{(\mathrm{p}K_\mathrm{a} - \mathrm{pH})}}\tag{1}$$
$$y = y_\mathrm{min} + \frac{y_\mathrm{max} - y_\mathrm{min}}{1 + 10^{(\mathrm{pH} - \mathrm{p}K_\mathrm{a})}}\tag{2}$$

Eq. 1: https://www.nature.com/articles/srep43748
"In the equation, $\sigma_\mathrm{peak}$ is the measured $\mathrm{NMR}$ chemical shift of the peak of interest, $\sigma_\ce{HA}$ is the chemical shift of the protonated form and $\Delta\sigma$ is the difference between $\sigma_\ce{HA}$ and the chemical shift of the deprotonated form of $\ce{HA}$ ($\sigma_\ce{A}$)."
Eq. 2: https://pubs.acs.org/doi/full/10.1021/ed3000028?mobileUi=0
"$y$ is the experimentally measured parameter (chemical shift, in this case), and $(y_{max} - y)$ and $(y - y_{min})$ are proportional to the concentrations of the deprotonated and protonated forms of the acid, respectively."


texts: Side product obtained in reduction of cuprous oxide with carbon

texts:
So my book sates that in the extraction of cuprous oxide, the following reaction takes place.
$$\ce{Cu2O + C -> 2 Cu + CO}$$
This makes sense to me, if it is seen as the following two reactions coupled.
$$
\begin{align}
\ce{Cu2O &-> Cu + 1/2 O2} \\
\ce{C + 1/2 O2 &-> CO}
\end{align}
$$
But as per the Boudouard reaction, carbon monoxide is the dominant form of oxide of carbon at higher temperatures, however using carbon for reduction is also possible at lower temperatures, which can be seen from Ellingham diagram.
So, are both $\ce{CO}$ and $\ce{CO2}$ possible as side products depending on temperature at which the extraction of $\ce{Cu}$ is done?


texts: How can an insoluble compound be a strong electrolyte

texts:
Here's a quote from Petrruci General Chemistry (pg. 160):

Silver chloride, $\ce{AgCl}$ is an insoluble ionic compound. When $\ce{AgCl}$ dissolved in water, it is 100% dissociated into $\ce{Ag}^+\text{ and } \ce{Cl}^-$ ions; there are no $\ce{AgCl}$ pairs.

I'm confused:

1) If $\ce{AgCl}$ is insoluble, how is it dissolved in water?

2) If  $\ce{AgCl}$ is a strong electrolyte but insoluble, does it mean a  $\ce{AgCl}$ molecule is ionized, but isn't separated - i.e. the silver and chloride remains close (they're not solvated by water molecules) but each becomes and ion?
I'm confused, can someone explain what's going on?


texts: Copper sulphate use as mould deterrent in evaporative humidifier

texts: Is it okay to use copper sulphate in an evaporative humidifier to prevent mould growth?


texts:
Does anyone know if it is possible to open an epoxide and do a 2-C extension using an enolate ion, say, of acetone? Here's an example of what I mean:

Based on what I know of enolate chemistry, this shouldn't be problematic, but I've never seen it.

I have done some preliminary literature searching and checked out masterorganicchemistry.com, etc. but have not been able to find anything about this.


texts: Zero filling leading to increases in resolution (NMR)

texts:
Zero-filling involves adding data points with zero intensity to the end of an FID. According to this website https://www2.chemistry.msu.edu/facilities/nmr/handouts/DH%20NMR%20Basics.pdf zero filling can take a spectrum with low apparent resolution to one that is much more helpful like so

In this instance, going from bottom to top corresponds with more zero filling. I do not understand how this happens. How does adding data points with zero intensity lead to increases in apparent resolution? I am certain I am missing some crucial point, but I can not pinpoint what that may be. For what its worth, I understand that we are not increasing the resolution of the instrument's measurements, rather we are manipulating the data to view information that would otherwise not be displayed.


texts: Addition of Br2 to Double Bond and Carboxylic Acid

texts:
In the above reaction, I remember reading that Br2 in CCl4 develops a partial polarity and adds on to the double bond, resulting in addition of Br on 2 adjacent carbons.

But, as per the text, the end product is a ester. (As given below)

Why is this the final product, and how to judge the products in cases like this?

Note - If I look at the answer and work backwards I would say that first Br+ attacks, and a carbocation is formed, on which hydroxy group attacks to form the final product. Is this right? And of it is then, why is this happening?


texts:
I was reading my book, in which it mentioned that aluminium and gallium oxides are amphoteric and and indium and thalium oxide are basic in their properties.
But no explanation was given.
My main question is we know that mostly metal oxides are basic and non metal oxides are acidic. But we see some metal being amphoteric, what is the cause of this difference?
I tried to search online but found no reliable piece to read.


texts: How to determine the iron content in spinach with a spectrometer?

texts:
I used a spectrometer to find the absorbency of 5 solutions with different iron concentrations.

\begin{array}{rrrrr}
  \ce{Fe (III)} / \pu{mol L-1} &
  \text{Absorbance} &
  V(\ce{HCl}) &
  V(\ce{FeCl3}) &
  V(\ce{KSCN}) \\
  \hline
  0.00005 & 0.194 & \pu{9 mL} & \pu{1 mL} & \pu{10 mL} \\
  0.0001  & 0.424 & \pu{8 mL} & \pu{2 mL} & \pu{10 mL} \\
  0.00015 & 0.674 & \pu{7 mL} & \pu{3 mL} & \pu{10 mL} \\
  0.0002  & 0.89  & \pu{6 mL} & \pu{4 mL} & \pu{10 mL} \\
  0.00025 & 1.113 & \pu{5 mL} & \pu{5 mL} & \pu{10 mL}
\end{array}

With this data I've constructed a graph and a line of best fit.
\begin{align}
y &= 4608x - 0.0322 &
R^2 &= 0.9994
\end{align}

I took $\pu{5.10g}$ of spinach leafs and burned them, then added $\pu{10.00 mL}$ of $\ce{HCl}$ and $\pu{10 mL}$ of $\ce{KSCN}$ then filtered the contents (so ashes weren't in the beaker).

The absorbency of this spinach extract was $0.015$.

My question is: How do I calculate how much iron is in this sample? I need to determine the mass of iron per $\pu{100 g}$ of spinach.

Using the line of best fit question, solve for $V(\ce{Fe(III)}) = x$ concentration:
\begin{align}
0.015 &= 4608x - 0.0322\\
x &= 0.0000102431
\end{align}

Convert $\pu{mol/L}$ to $\pu{g/L}$ to $\pu{mg/L}$:

\begin{align}
0.0000102431 \times 55.845 &= 0.00057202591\\
\pu{0.00057202591 g} &= \pu{0.572 mg}
\end{align}

But this is clearly wrong because it's not taking account the amount of spinach I started with ($\pu{5.10 g}$). Anytime I try to include the amount, either by multiplying the density my answer is way off.

Is it reasonable that I'm getting a number above $\pu{10 mg}$? The iron amount reported by the USDA says that there is $\pu{2.7 mg}$ of iron per $\pu{100 g}$ of spinach.

Can anyone guide me in the correct direction?


texts: Where can I find reliable data for melting points of organic compounds?

texts:
I'm interested in the melting/freezing points of organic compounds, but the online literature has data that's all over the map. I can understand that especially for isomers of alkanes, pure samples can be difficult to obtain; but as basic a property as melting point ought to be well-established and easy to reference.

For example, the m.p. listed for 3-methylpentane varies from -118 °C to -163 °C depending on source. That's an enormous spread; in fact, those two numbers reoccur frequently enough that I suspect that sources are quoting older sources possibly back to the early 20th century. And that's far from the only example I could cite.

Are there any reliable sources that have experimentally confirmed the values?


texts: How can I get big bubbles when I electrolyse water with detergent?

texts:
I've made carbon electrodes by putting 12V through a couple of short 15Ω pencils, but when I try to make hydrogen and oxygen bubbles from soapy water, I get tiny bubbles, smaller than table salt.
If I move the electrodes closer together, it's the same tiny bubbles, but a bit faster.
These don't catch fire very convincingly, and my daughter is unimpressed.
How can I get larger bubbles? Different electrodes? Higher voltage? Just shove the AC power in straight from the wall? :)


texts: Is there a way to use free software to convert SMILES strings to structures?

texts:
So far I've been unsuccessful in finding an open source tool that will convert a large number (>100k) of SMILES strings to a chemical structure.
Is this really only solved by commercial applications?
I would not mind converting through a number of intermediate formats.
Ideally I'd do it with R, but that is the least of my worries.
It's also neither for personal nor academic use.


texts:
I've run into a question that says after doing the Lewis structure of $\ce{IF3}$, which I did, explain why $\ce{I4}$ doesn't exist.

I am confused as to how it can be explained. I've thought that maybe it has to do with iodine's valence orbitals, both hybridised or not being too large and as a result the different orbitals would have to overlap and superimpose. But again I'm not sure.


texts: Salt Water Metal etching 50 (Euro-)Cent Coin

texts:
I want to etch the 50 Cent Euro Coin using this following technique that I came across on some DIY site: Immerse the coin and some disposable piece of metal in salt water such that they do not touch and attach current. Cover the non-to-be-etched parts of the coin with nail polish.

The article proposed to use a 9V battery block and used brass in their example. I understand the 50 Cent coin is made out of Nordic Gold: Is this etching method still viable, and does the 9V block deliver enough energy to at least remove the imprinting of the coin? Is there something else to consider (safety isseus)?

Unfortunately, I have no noteworthy background in chemistry. Thanks a lot in advance for any help.


texts: Theoretical Value of Activation Energy of Potassium Iodate and Sodium Bisulfite?

texts:
I investigated the Arrhenius equation using the reaction between potassium iodate (containing the IO3- iodate ion) and sodium bisulfite (containing the HSO3- hydrogen sulfite ion. The ionic equations for the reaction’s two stages are as follows:

IO3- (aq) + 3HSO3- (aq) -----> I- (aq) + 3SO42- (aq) + 3H+ (aq)

5 I- (aq) + 6H+ (aq) + IO3- (aq) -----> 3I2 (aq) + 3H2O (l)

I rearranged the Arrhenius equation to give:
ln(k)=(-Ea)/R)(1/T) + ln(A)

I changed the temperature of the reaction and timed the speed of the reaction, which I used to calculate the values of k. I then graphed the relation between ln(k) and 1/T , with the slope giving –Ea/R.

My graph ended up having a slope of -0.0003, so I obtained an activation energy of 0.00024942 J/mol.

I was wondering if anyone had a theoretical value of the activation energy of this reaction I can compare my experimental value to?


texts: Can allenes be used as motors or generators?

texts:
I was thinking about an allene, fucoxanthin:

Potentially, we can draw a resonance structure in which up to eight of the carbon-carbon double bonds have moved one position to the left, a carbocation is present somewhere along the carbon chain, and the allene is replaced by a carbanion.  We could also imagine beginning with the enol form and one extra C=C bond, in which case the positive charge could be on the epoxy alpha carbon.
It is also conceivable to reverse the polarity, with a carbocation at the allene and a carbanion somewhere on the left.
There is a problem, of course, which is that allenes are linear while carbanions are bent. Carbocations should be linear, though I doubt they are as "stiff" as an allene.
To be sure, the bending of these allenes doesn't seem nearly as dramatic as has been observed.  I looked up the crystal structure and worked out the bond angle of the allene for 1337, 1383, 1433, and 1481, getting 2.4, 1.6, 0.8, and 0.0 degrees of bending - I doubt any of those are significant differences.  Still, I wonder if the natural world is always so quiet as a crystal structure.
In general... could this molecule interconvert electrical energy to physical force?  Could electrons passing through the photosynthetic complex physically flap the right side of the molecule as they come and go, or could mechanical force on the right side be used to generate "photosynthetic" energy?


texts: Major product of the dehydration of alcohols

texts:
Well I was doing some questions and I have a bit of confusion on dehydration reaction. For instance, consider following reaction:

How do I decide which adjacent hydrogen gets attracted by $\ce{HSO4-}$?

now we have 3 possibilities:

either hydrogen 1,2, or 3 can leave resulting in 3 different products. So my question is how do I identify the major product in this case?


texts: Molecule analog similar and commercially available

texts:
I wanted to carry out some experiments on the following molecule:

Unfortunately this molecule (santalene; either isomer will do) seems neither commercially available nor easily synthesizable.

Hence I am looking for analogs that I can start out with. Any idea which commercially available molecules might be similar to this molecule?

I did fine one analog (curcumene) but even that does not seem to be available with Sigma or any of the usual sources for even fairly esoteric molecules.

Any thoughts / tips? Alternatively, a synthesis for my target molecule might also help, in case I am missing any obvious routes.

PS. Any recommendations for tools / sites that will do a good search for analog molecules?


texts: Is it correct to talk about an empty orbital?

texts:
Professor A. J. Kirby mentions:

  The properties of an orbital are those of an electron contained in it. It is normal practice, illogical though it may sound, to talk of 'vacant orbitals'.The properties of vacant orbitals are those calculated for electrons occupying them.

Since an orbital isn't defined until it is occupied by an electron, would it still be correct to say that an empty orbital (such as a LUMO) can interact with other filled orbitals?


texts: Are the Phosphate and Sulfate ion diagrams with double bonds an invalid picture?

texts:
Whenever you see an image of phosphate, it's always shown having 5 bonds. 3 single bonds to anionic oxygen atoms and a double bond to an extra neutral oxygen.

Not only that, but they're shown being arranged in a tetrahedral manner. All of this additionally applies to sulfate, only that it has 2 double bonds instead of  just one.

Now, from what I've been able to gather from the net, including this website is that this can be explained by invoking sp3 hybridization and a d orbital. The 3 anionic oxygens who already have a charge of -1 pair up with the 3 partially filled hybrid orbitals in phosphorous, while the remaining filled sp3 orbital on phosphorous donates it's electron pair to the empty orbital on an extra oxygen.

Once again, this is exactly the same for sulfate, except that it can only bond to 2 anionic oxygens while also being able to donate 2 electron pairs to other oxygen atoms.

This leaves us with 4 single bonds to oxygen atoms. This doesn't seem unusual at all. Nitrogen can easily take on 4 bonds just like phosphorous, and seeing how row 3 elements have a looser hold on their outer electrons, it makes sense that they can donate their complete electron pairs much easier than row two elements, seeing how their electron pairs would "stick out" more, making them much more available for bonding.

However, in Phosphate when you get to the 5th bond you have to explain it by being a little more creative. You could say that a p orbital on one of the oxygen atoms donates it's electron pair to an empty d orbital on phosphorous, creating and extra bond between phosphorous and one of the oxygens. The same thing happens in sulfate only that for some reason it can form two double bonds. (which I really wonder if that would be pushing the limits of stability at all. I mean wouldn't the two d orbitals kind of overlap at an awkward angle causing some kind of repulsion?)

Now, apparently from what I've heard, experimental evidence has shown that there is very little d orbital involvement in molecules like phosphate or sulfate, and they're practically all single bonds. So my question is, is this true? And if so, then why is the double bond picture still in practically every textbook, diagram, and piece of scientific literature that you come across? How did this picture of these ions emerge? I know it had something to do with linus pauling, but was this just accepted based on theory alone and no experimental evidence at all? Was there some experimental evidence for it in the beginning?

Sorry if it sounds like I'm asking too much, but I just find this whole situation so confusing. I'd appreciate your answers.


texts: Group 13 elements reactivity with halogens

texts: All the trihalides of the Group 13 elements are known, but $\ce{TlI3}$ is not. Why is this so?


texts:
I took samples of tapwater in order to examine concentrations of Escherichia coli and enterococcus in a rural area. I was told, from an analytical lab, to take samples in four sterilized vessels bought from pharmacy.

The problem is that at the completion of the last vessel, its cap fell frοm my hand down into the soil and some grains of sand were stuck on the inner surface of the cap. As fast as I could I picked it up and washed it off totally with the water of the sampling tap. After that I closed my last sampling vessel with it and this is the completion of the sampling.

How large is the possibility my sampling has a serious contamination of these twο biological pollutants after this incident?


texts: What type of isomers are the following two compounds?They do not seem to be geometrical isomers as the methyl groups at terminal position are not in same plane as such.Are they conformers?


texts: What is the molecular shape of Sulfur Pentafluoride Anion?

texts:
$\ce{SF6}$ is an octahedral shape which makes perfect sense. $\ce{SF5^+}$ arranges 5 pairs of electrons in a trigonal bipyramidal structure. But what if you add a lone pair to this? Will the electron pairs arrange into an octahedral shape, but due to extra repulsion of lone pair, or will it have some distortion?

Will it be similar to $\ce{BrF5}$ structure?


texts: Aufbau's principle violation at the time of complex formation

texts:
My doubt is why don't we write 4s orbital before 3d as it is lower in energy according to Aufbau's principle? (I'm getting this info from other sites that 3d comes before 4s in transition metals but I'm not pretty sure about this thing)

Further, why are 4p and 4d come directly after 4s? Should have 5s come before 4d according to Aufbau's Principle?

Please help me I'm very much confused


texts: Setting up a water aspirator pump for vacuum distillation

texts:
I have a question about the functioning of a water aspirator in a vacuum distillation setup.

I have read about how the water aspirator is hooked up to the water source and the vacuum is in turn connected to the vacuum adapter, and that there should be a splash guard or tubing on one end of the aspirator as well. I'm trying to figure out what to make of the highly suggested use of a water trap. Supposedly the water trap needs to be connected to the vacuum as well as the system.

What outlet is there left to connect to the aspirator, already being connected to the water source and apparatus, as well as the splash guard underneath? Also, if a water trap should be connected to the system, where should it be connected, is a flask with additional adapters required?


texts:
I am trying to find out what BPA is used for in the industrial production of plastics. On sources such as Wikipedia I only found the information that it is used, but not why.

What are the advantages in using BPA in the production of plastics? Why is it needed?


texts: I understand that the square of the wave function is the probability density of finding an electron. However, what is the wave function itself? I am trying to understand molecular orbital theory but this concept is getting in the way of me completely understanding it. Any help would be great. Thanks.


texts: Chemical reactions with a room-scale cooling effect

texts:
Are there chemical reactions that could cool down an average sized room by a noticeable amount (say 5 °C)?

I would like to investigate if it is possible to have a situation where I can mix 2 reagents at room temperature and pressure and in open air then they should react and become colder than room temperature without evaporation of some type, with an eye to making a noticeable drop in the room temperature.


texts: Why do atoms generally become smaller as one moves left to right across a period?

texts: It seems to me that the addition of electrons and protons as you move across a period would cause an atom to become larger. However, I'm told it gets smaller. Why is this?


texts:
I am new to chemistry. I am looking for a gas that would de-oxidise aluminium.
Which gases would work for that and at what temperature?

Details: I need to sinter aluminium powder. But because the top layer of aluminium is oxidized when exposed to the atmosphere, I need to remove the oxide film before the sintering would work.

Thanks so much,

Sergey


texts: How to find the average half life of radioactive nuclide which undergoes two different decays?

texts:
Find the average life of a radio nuclide which decays by parallel paths,
  \begin{align}
A  &\rightarrow B\\
2A &\rightarrow B,
\end{align}
  where the decay constants are $\lambda_1 = \pu{0.018 s-1}$ and $\lambda_2 = \pu{0.001 s-1}$, respectively.

I used the formula
$$\frac{1}{t} = \frac{t_1 t_2}{t_1 + t_2,}$$
where $t$ represents the mean life. The equation can be written as:
$$\frac{1}{t} = \lambda_1 + \lambda_2$$
But I am getting the correct answer only if I take $\lambda_2$ as 2 times the given decay constant for the second reaction. Is this because of $\underline{2}A$ on the reactant side instead of $A$?


texts: Strange "far out" orbitals in HF and DFT calculations. Why do they occur?

texts:
I calculated some orbitals and I get quite strange results with orbital geometries I wouldn't expect from MO theory. A more experienced colleague just said: "That's always the case with big basis sets, just ignore those and search for the ones that make sense" which is a very unsatisfying answer and he couldn't explain what's the cause or what they mean. I also noticed that these occur more often/with lower energy when using HF but they also occur using DFT.

Can anyone explain what happens here and why?

Here is one example with the first two looking like I would expec.

The first 5 unoccupied orbitals using HF (6-311+G(d,p)) including energies in eV:


texts: Which factor should I take into priority to determine reactivity of of Halides?

texts:
Such as in the attached question I was taking into account the stability of the carbocations (by the number of resonating structures) formed after removal of Chlorine from and concluded to be the order I>II>III>IV>V the answer states the order to be I>III>IV>V>II

Can conclude what factors they are priority to. Help needed


texts: What is the difference between primitive Hexagonal unit cell and Hexagonal closed packing HCP

texts:
There are 14 types of Bravais crystal lattices (Primitive + Centered) in 3D. Every solid in this universe is made by the unit cells of these lattices.

With the help of these Bravais lattice can HCP be formed?.
Is there any relation between Hexagonal unit cell and Hexagonal close packing
As we see that Hexagonal unit cell exists only in primitive AAA form then how can HCP ABA be formed from it .

Primitive Hexagonal unit cell

Hexagonal closed packing HCP

If there is a clear distinction then Should HCP also be placed among 14 Bravais lattice.


texts:
Is there a way of calculating the amount of sodium metabisulfite from the sulfite content?

I found online instructions for the test kit for sulfite that suggests multiplying by $2.37$ to obtain $\pu{mg/l}$ of $\ce{Na2S2O5}$ from the $\pu{mg/l}$ of $\ce{SO3}$ found in a sample.

Where did they get that $2.37$ from?

This is the formula I came up with:

$$\frac{\pu{mg/l} (\ce{SO3}) \times \text{total volume} \times M(\ce{Na2S2O5})}{M(\ce{SO3})}$$

i.e.

$$\frac{\pu{5 mg/l} (\ce{SO3}) \times \pu{100 L} \times \pu{190.107 g/mol}}{\pu{80.063 g/mol} \times 100} = \frac{5 \times 100 \times 190.107}{80.063 \times 100} = \pu{27.306 g} (\ce{Na2S2O5}) \text{ in 100 liters}.$$


texts:
This is the raman spectrum of the black cap:

I was expecting it to be Polypropylene but the peaks didn't match in wave numbers. Anyone got idea what kind of plastic has that peaks on the side of 1500?

When I tried the raman analyzer on the clear housing.

I got this raman spectrum.

Which matches that of Acrylonitrile butadiene styrene see:https://en.wikipedia.org/wiki/Acrylonitrile_butadiene_styrene

Original message:
I was trying to identify the material of this sediment filter cap whether it is really Polypropylene but i couldnt get a good signal but only noises no matter the exposure and time (my raman spectrometer is 532nm.

Is it really hard to get raman signal out of black matte object, maybe it cant reflect the laser?
I was able to get good raman signal of the blue casing though but not the black cap.


texts: How to determine the minimum pH at which iron(III) hydroxide dissolves completely?

texts:
Knowing $K_\mathrm{s} = 6\cdot10^{-38}$ for $\ce{Fe(OH)3}$ in neutral solutions, calculate the minimum pH of an acidic solution in order to completely dissolve $\pu{10 mg}$ of $\ce{Fe(OH)3}$. Data: $V = \pu{0.1 L}$.

My idea was to calculate the amount of $\ce{Fe^3+}$ and $\ce{OH-}$ ions, and then add enough acid containing $\ce{H+}$ ions in order to neutralise the $\ce{OH-}$ ions corresponding to the amount of $\ce{Fe^3+}$. To do this I used the equilibrium constant leaving the hydroxide ions as the unknown. Then I calculated the difference between the initial hydroxide concentration (corresponding to $\pu{10 mg}$ of salt) and the needed concentration to reach $K_\mathrm{s}$. This corresponds to the concentration of hydronium ions in the acidic solution, and I can calculate pH.

Doing this I get $\mathrm{pH} = 3.03$. Is this how it should be done?


texts: When reacting a strong acid with a weak base, would all of the strong acid react with the weak base

texts:
If I do the following reaction:
$$\ce{Na3PO4 + 3HNO3 -> 3NaNO3 + H3PO4}$$
Does nitric acid completely react with the Trisodium phosphate to form a weak acid and a salt, or does it form a small amount of the weak acid or nothing? If it does form the weak acid, will this reaction create heat?
I have only really dealt with neutralization reaction so I don't really understand what will happen, any help would be greatly appreciated.


texts: Common chemcials that produce phosphorescence

texts:
Are there any common lab chemicals or household stuff that produce phosphorescence?
I am aware of ZnS, CaS, Fluorescein, Erythrosin B, Vanillin Benzaldehyde, Vitamin B2, Tryptophan etc.
I just need something for sanity check on a fluorescence/phosphorecence lifetime measurement system. I am getting results with fluorescence, but not with phosphorescence.
My samples are biological plant material. With TCSPC in nano second timescale, I am getting fluorescence decay. But with micro and milli second timescale, I am getting only unifom constant counts (looking like background counts). The sanity check is to see if the instrument is able to detect phosphorescence decay from any material known to have phosphorescence, hence the question.
Counts with Nano second timescale

Counts with Milli second timescale (Red = IRF, Black = Decay)


texts:
What exactly is the mechanism by which Benedict’s test works for reducing sugars? As I understand it the free hemiacetal groups on reducing sugars opens up and an aldehyde is formed, this is then oxidised by Cu2+ which then results in a red copper(I) oxide.
RCHO + 2 Cu2++ 5 OH- → RCOO- + Cu2O + 3 H2O.
The equation above isn’t really clear to me, what is exactly going on?
Additionally why are alkaline conditions required for the test? And if a red precipitate is formed how come there is such a wealth of colours observed (green, yellow, orange) for varying concentrations of reducing sugars?
Perhaps these are a couple of questions too many :D


texts: Finding the pOH of a buffer from the scratch without the Henderson Hasselbalch equation

texts:
I found this question on the internet that said:

Find the pOH of the solution obtained by mixing $\pu{0.1 mol}$ of $\mathrm{NH_4 OH}$ $(K_\mathrm b = 10^{-5})$ and $\pu{0.1 mol}$ of $\ce{(NH4)2SO4}$ in a $\pu{500 mL}$ solution.

What my approach was to do it without applying the Henderson Hasselbalch equation and doing it from the scratch using the "common ion" effect. Here is how I did it:
$\ce{NH4OH}$ is a weak acid and $\ce{(NH4)2SO4}$ is a strong electrolyte.
$\alpha$= The dissociation constant per mole
$$\ce{NH4OH <<=> NH4+ + OH-}$$
\begin{array}{l|c|c|c} \hline
n_\mathrm{initial} & 0.1& 0 &0\\
n_\mathrm{equilibrium} &0.1(1-\alpha) &0.1\alpha& 0.1\alpha \\
\hline
\end{array}
$$\ce{(NH4)2SO4 -> 2 NH4+ + SO4^2-}$$
\begin{array}{l|c|c|c} \hline
n_\mathrm{initial} & 0.1& 0 &0\\
n_\mathrm{dissociation} &0 &0.2 & 0.1\\
\hline
\end{array}
Now, we can say that
$$K_\mathrm b = \frac{[\ce{NH4+}] [\ce{OH-}]}{[\ce{NH_4OH}]}$$
$$10^{-5}= \frac{\dfrac{0.2+0.1 \alpha}{0.5} \times \dfrac{0.1 \alpha}{0.5}}{\dfrac{0.1}{0.5}}$$
As, $\alpha$ is very small for a weak acid, $0.1 \alpha \approx 0$.
Doing the further calculations, we get:
$$\boxed{\alpha = \frac{5}{2} \times 10^{-5}}$$
$$\implies \boxed{\ce{[OH-]} = 0.1 \alpha = \frac{5}{2} \times 10^{-6} \frac{\pu{mol}}{\pu{500 mL}}}$$
Now, $$\mathrm p\ce{OH}=\log[\ce{OH-}] = -[\log(5)-\log(2)-6] = \boxed{5.6}$$
But if we directly apply the Henderson Hasselbalch equation for the buffer, we get:
$$\mathrm p\ce{OH} = \mathrm pK_\mathrm b + \log\left(\frac{[\mathrm{salt}]}{[\mathrm{base}]}\right)$$
$$\mathrm p\ce{OH} = 5 + \log\left(\frac{\dfrac{0.2}{0.5}}{\dfrac{0.1}{0.5}} \right) = 5+ \log(2)=\boxed{5.3}$$
[.] = molarity
Where did I go wrong in the calculation or what mistake did I do while solving this question?


texts: Is barium sulfate soluble in dilute mineral acid?

texts:
I have read that $\ce{BaSO4}$ is soluble in $\ce{HCl}$ , but I am not sure whether this works for dilute acid as well.

The reaction is -
$\ce{BaSO4 + 2 HCl ->BaCl2 + H2SO4}$


texts: Why hasn't chemistry brought about a greater level of human enhancement(as of yet)?

texts:
So, this question had me thinking, this as someone who comes from the field of machine learning. Why haven't chemicals enhanced our minds and bodies as much as was predicted in the early years?

From the 40s till about the 70s I would say, many scholars and general talking heads predicted that chemistry would not only revolutionize food, industry(which it has) but also completely redefine the limits of humans by extending life exponentially as well as give super-human like mental and physical attributes.

Seemingly, this has not happened yet. While chemistry has completely changed a lot of what humanity does, it has never quite lived up to expectations(much like mine). So what is the disconnect? Is it that we just need more time? I am suspicious of that as chemistry is an very old field by academic standards and from what I read has been seeing diminishing returns in research.

I ask this as someone with only a rudimentary understanding of organic chemistry. Thanks!


texts: How is entropy change defined for a chemical reaction?

texts:
I know that:

ds = dq/T for reversible processes.

Can I write change in entropy of a system in which a chemical reaction is happening using this equation. Basically, my question is about whether a chemical reaction happening in an open vessel(isobarically and isothermally) be treated as a reversible process?


texts: Why do unbonded electrons exist in pairs?

texts:
Basically the term which we use to refer them is lone pair. In Lewis structure why we represent those unbonded electron in pairs. Like here (structure of SO2)

Here if we assume both the unbonded electrons to be existing in pairs then it's geometry will be different from what we would observe in case when both electrons exists freely (without pair).

So why we basically consider those electrons to be existing in pair? Is it any kind of observation or any theory or both?


texts: What is smell??How come 2 things have the same smell

texts:
I have been wondering how something smells.
How come something smells the same as other thing? What is similar in them?
Like what is the chemistry behind a particular smell of a substance?

For example compounds with SH (thiol) smell awful and similar, so what is similar between them? I know SH, but I am asking why can't they smell different.


texts: Is there a way to convert aniline to phenol without diazotizing it?

texts:
I am a high school student and while reading about reactions on amines, I was trying to figure out a way to convert aniline $(\ce{C6H5NH2})$ to phenol $(\ce{C6H5OH})$ without diazotizing it with sodium nitrite $(\ce{NaNO2})$ and dilute hydrochloric acid $(\ce{HCl})$ in temperature conditions of $\pu{273 K}$ to $\pu{278 K}$ and then reacting it with $\ce{H2O},$ i.e. anything that does not involve the following reaction:
$$\ce{RNH_2 + NaNO_2 + HCl ->[$273–\pu{278 K}$] [RN2^+Cl^-] ->[H2O] ROH}\tag{R1}$$
I tried converting it to an isocyanide via the carbylamine reaction, but that seemed to make things more complicated. The closest I found to solving this was Tilden's reagent $(\ce{NOCl}),$ which reacts with primary amines in the following way:
$$\ce{RNH2 + NOCl -> RCl + N2 + H2O}\tag{R2}$$
However, this is limited to primary amines by definition.
Is there any way to convert aromatic amines to aromatic alcohols without diazotizing the compound? More specifically, is there a way to convert aniline to phenol without converting it to a benzene diazonium ion?


texts: Does the delocalization of p-orbitals ensure conductivity?

texts:
For example, polyacetylene is a conjugated system, i.e. with de-localized p-orbitals, but accroding to Chiang et. al. (1977) polyacetylene is semiconducting, and becomes conductive only when doped with Cl/Br/I/AsF5.

Isn't the conjugation alone enough to allow conductivity?

(source)

UPDATE

One reason they mention in the paper is:

  In the idealized situation of a uniform chain, the resulting
  conduction band would give rise to metallic behavior. However, such a
  system is unstable with respect to bond alternation, which causes the
  formation of an energy gap in the electronic spectrum.

But if this is true then (1) how the halogens improve the situation, and (2) why isn't there a similar phenomenon in all conjugated systems?


texts:
The equivalent weight of HNO3 in the following reaction is ‘x’, then the value of x/21 is

3Cu+8HNO3⟶3Cu(NO3)2+2NO+4H2O

in this I atempted by using redox formulas but my answer is comming 1 but correct answer is 4


texts: What classifies as a solvent/base in SN1, SN2, E1, and E2 reactions?

texts: I need to clarify some terminology for an intro to organic chem class. We are studying substitution and elimination reactions and it has not been made clear what exactly these terms describe. For instance, in the bottom example of this image I have seen CH3OH on both the top and bottom of the arrow. Does this imply that it is the nucleophile/base when it is on top, and a solvent when it is on the bottom?


texts: What is the reason behind optically activity of compounds

texts:
I am currently being taught optical activity of compounds and I had this question:

  Optical rotation (optical activity) is the turning of the plane of linearly polarized light about the direction of motion as the light travels through certain materials.

What happens inside these compounds (for example sucrose) that causes them to behave on this manner. By that I mean to say that what takes place in the compound due to which they turn the plane of light when it travels through these materials?


texts: Are there any common and identifiable hazards to being a Chemistry Teacher?

texts:
I'm a High School Chemistry teacher. I have only been teaching for a few years and know very few other chemistry teachers. Of the ones I do, One has died of cancer, one is a cancer survivor and one is being tested and currently in cancer therapy while an equal number remain healthy (but have taught fewer years). That's scarry.

Could it be coincidence or some other more localized cause? Yes. Although cases were up to 100 miles apart. I realize the sampling size is small and this is all very anecdotal but I'm looking for answers nonetheless.  It seems to me that a possible culprit might be the haphazard way that stock handling and chemical lab supply making is done in High Schools as compared to higher education institutions or research facilities. Many schools don't vent their stock rooms even though it's required (there are no consequences) and teachers take the stock put it out on the counter and measure out what they need and make solutions. They don't bother with gloves, lab coats or aprons either. In a professional laboratory this would be done in a fume hood to minimize long term exposure to many substances with proper protective clothing.

Are there any readily identifiable health hazards for a High School Chemistry teacher based on the above information?


texts: Nucleophilic substitution of 2-chloropropanoyl chloride

texts:
Upon heating 2-chloropropanoyl chloride with concentrated ammonia in a sealed vessel, a primary amide is formed but the chlorine atom at the beta carbon does not get substituted with an amino group, that  is, the alkyl chloride portion of the molecule  fails to undergo nucleophilic substitution.

Why is this so?


texts: How many times should I run a solvent extration experiment through?

texts: For advanced higher chemistry project, I am extracting cinnamaldehyde from cinnamon via first steam distillation and then solvent extraction using hexane. I'll be adding sodium chloride to the water/cinnamaldehyde mixture. I'm not sure how many times I should run the solvent extraction or if there is a calculation for it.


texts: Is protein folding thermodynamically favourable? If yes.. why?

texts: The second law of thermodynamics dictates that the sum of entropy of the universe is always increasing. Is the process of protein folding a spontaneous process which is increasing the entropy? Is this why it can be called thermodynamically favourable? Or is there something else I am forgetting..


texts: Why doesn't the bidentate ligand form dative bonding three times?

texts:
I was looking at this question where  it asked you to work out the final complex formed when an excess of 1,2-diaminoethane is added to and aqueous solution of copper (II) sulphate.

So the equation I worked out would have been:
$$\ce{[Cu(H2O)6]^2+ + 3(NH2CH2CH2NH2)-> [Cu(NH2CH2CH2NH2)3]^2+ + 6H2O}.$$

Therefore I worked out the complex to be: $$\ce{[Cu(NH2CH2CH2NH2)3]^2+}$$

However the answer was : $$\ce{[Cu(NH2CH2CH2NH2)2(H2O)2]^2+}$$

Why is this?


texts: Why don't salt crystals attract each other?

texts: If salt is made of ions in a giant lattice, surely if I have two crystals they would attract each other and fuse? Or maybe the ions can't get close enough to each other to attract, or the surface is made of a different, neutral material?


texts:
The third point of difference suggests that amorphous solids can't be cut into two parts of regular surfaces
But glass being an amorphous solid is cut into regular pieces often.
What am I getting wrong?


texts:
I know 3 types of unit cells, the simple cubic, the body centered and the face centered.

But what is a hexagonal unit cell, and why does it have a hexagon base while others are all cut into a cubic? And how can I calculate the number of atoms in every primitive hexagonal unit cells?


texts: Which is more soluble in water, HF or SO2?

texts:
I was wondering which is more soluble in water, hydrogen fluoride or sulfur dioxide? Since $\ce{HF}$ will hydrogen bond to other HF particles (as opposed to $\ce{SO2}$ dipole-dipole attraction).

Wouldn't $\ce{SO2}$ dissolve better as it would be easier for the $\ce{H2O}$ particles to dissociate?
Or would $\ce{HF}$ dissolve more readily as it will form hydrogen bonds with the $\ce{H2O}$ particles?


texts: How can vinyl chloride arise from treating 1,2-dichloroethane with a solution of potassium hydroxide in ethanol?

texts:
Liebig apparently created it that way (https://en.wikipedia.org/wiki/Vinyl_chloride#Production). However, googling I can not find chemical equation for such reaction, I only see ethene as result of such elimination reaction:
https://www.quora.com/What-is-the-product-when-1-2-dichloroethane-reacts-with-alcoholic-KOH


texts: Does it undergo Chloroform reaction or Canizzaro reaction?

texts:
What are the products formed when Trichloroacetaldehyde is made to react with NaOH? I see 2 possible routes the reaction can take:

It can form chloroform and Sodium formate, since this is the final stage of the chloroform reaction
It can undergo Canizzaro reaction to give Trichloroethanol along with the sodium salt of Trichloroacetic acid.

Please tell me which reaction occurs and why.


texts: What is the mechanism of platinum as catalyst poisons on alumina?

texts:
I'm wondering if anyone knows by what mechanism is platinum (or other noble metals) catalyst on alumina substrate poisoned?

Presently, I'm using platinum on alumina to decompose a hydrogen peroxide / $
\ce{KNO3}$ solution and have found the catalyst material poisoned.  I'm wondering if the poisoning is due to the $\ce{KNO3}$ or if my peroxide is contaminated.

I can imagine $\ce{KNO3}$ crystallizing and thereby occluding the active sites on the alumina but I'm not a chemist, so I've come here looking for better insight.


texts: Simple practical, non-toxic, non-flammable reaction for slow release of CO2

texts:
Someone I know (not me) has recently had problems with bed bugs. I have advised him his best bet is to (1) Buy a kick-ass steam cleaner and nuke the brutes from orbit, (2) get a professional pest controller in, and (3) Stop buying second hand furniture in future!

But being an inventive sort, he prefers a more subtle approach and is now intent on designing the perfect indoor bed bug trap.

It appears these critters are attracted by a localized $\ce{CO2}$ excess and by body heat, and are repelled by light and (presumably) excess heat. So assuming this trap won't involve a tethered goat or suchlike, he will need a compact, non-flammable, non-toxic, readily and cheaply available substance that can be persuaded to release a steady stream of $\ce{CO2}$ for several hours (without releasing CO or any other noxious or smelly biproduct).

I was thinking perhaps water dripping slowly onto calcium carbide, if there was some way of converting the resulting acetylene to $\ce{CO2}$ without burning it at a readily discernable rate. But a "slow burn", if it could be attained, might provide the heat source (although I reckon a more controllable electric heater would be better for that).

Any ideas? I suppose one obvious answer would be to simply buy a $\ce{CO2}$ cylinder, but could one then buy a sufficiently slow release valve to go with it?


texts: We know that 1 mole is equal to $6.023\times10^{23}$ atoms. But why it is not written as $6023\times10^{20}$ ?


texts: What advantages does the mole have over counting large numbers using SI prefixes?

texts:
I'm trying to understand why chemists use the mole unit instead of just counting and using SI prfixes to simplify the big numbers with units such as zetta- or yotta-molecules (yotta=10^24).

Here's what I've found so far, but it doesn't seem to be enough to make moles particularly important:

Reasons for moles:

You can easily approximate the number of atoms from the mass of a sample because the mass number of an isotope approximately equals the mass of 1 mole of atoms in grams.
It's a historical convention that would be too expensive or uncomfortable to change now.
You can use millimole and micromole instead of having to learn several more obscure SI prefixes like exa and peta. EDIT this reason is added from Jan's answer
Shorter descriptions, eg "mole of carbon" vs "yotta atom of carbon" (from matt_black's answer).

Reasons against moles:

For accurate calculations (beyond about 3 significant figures), the relationship between mass number and mass in the first reason above breaks down. So this is a risky thing to use.
It's a additional concept and set of facts that chemists have to spend effort learning but which describes human convention rather than nature.
We need extra conversion factors such as 1/mol which people often neglect and Faraday's constant used in Q = n(e-) x F [1] which wouldn't exist without moles.

Non-reasons for moles:

You can easily calculate the number of atoms from the mass of a sample because the atomic mass of an element equals the mass of 1 mole of atoms in grams. This relationship only exists because of the special units commonly used for atomic mass. If periodic tables listed atomic mass in grams (or perhaps yoctograms), then we could do the same calculations just as easily without moles.
In practice, we can't measure the number of molecules so we have to measure mass or volume instead and should therefore count them using a unit that's defined in terms of mass. I don't think the precise details of how a unit is defined matter for practical purposes. If you have 1 litre of an ideal gas, you still have to do calculations to find out many moles it contains just as you would to find how many molecules it contains. There is even a proposal [2] for SI to redefine the mole to be independent of the mass of any substance, indicating that keeping the definition isn't very important.
Chemists would make mistakes with those big numbers. They'd use "yotta" in the same way they use "mole", not doing calculations with the actual number it represents and not being at risk of other types of error. (from matt_black's answer) However it would be more complex replacing millimole with zetta because you'd have to remember that a zetta-atom is a milli-yotta-atom.

Here's a similar question but it's mixed in with the idea of measuring number rather than mass or volume -
Why do people still use the mole (unit) in chemistry?

This other similar question mainly addresses the uncommonness of quantities as big as 1 mole in other areas of life -
The mole is used extensively in chemistry, why not elsewhere?

[1] http://www.ausetute.com.au/faradayl.html

[2] https://en.wikipedia.org/wiki/Proposed_redefinition_of_SI_base_units


texts: Equation for the reaction of iodide to iodine using hydrogen peroxide under acidic conditions?

texts:
I'm building a home lab around All Lab, No Lecture Illustrated Guide to Home Chemistry Experiments and I'd like to understand the chemistry that I'm doing a bit better. For example, here's an iodine experiment.

  Weigh out 2.0 g of potassium iodide and transfer it to a test tube.
  Add about 1.5 mL of distilled water to the test tube and swirl to dissolve the potassium iodide.
  Add 1.5 mL of concentrated hydrochloric acid (or about 1.8 mL of hardware store muriatic acid) to the test tube and swirl to mix the
  solutions.
  Add about 10 mL of drugstore 3% hydrogen peroxide. The solution immediately turns dark brown as the iodide ions are oxidized to
  elemental iodine, which precipitates out.
  Swirl the test tube to suspend the iodine and pour the liquid through a funnel with a folded piece of filter paper to capture the
  iodine crystals.
  Rinse the iodine crystals on the filter paper several times with a few mL of distilled water. The rinse solution appears brown from
  dissolved iodine, but iodine is not very soluble in water, so you're
  not losing much of your yield.
  Spread out the filter paper on a watch glass or saucer and allow the crystals to dry thoroughly. Iodine gradually sublimates (passes
  directly from solid to gaseous form) at room temperature, so don't
  leave the crystals exposed to air any longer than necessary to dry
  them.
  Once the crystals are dry, transfer them to a sealed storage bottle or vial.

It's easy enough to follow and I know I have $$\ce{KI, H2O, HCl, H2O2}$$ with a result of $$\ce{I2\, +\, ???}$$ but then what?

I've had HS Chemistry, skipped Chem in college :(, so I know how to balance equations, convert from g or ml to moles, etc, but where can I learn to translate an experiment into equations without having to ask others (Textbooks or online resources are ideal, going and taking chem at a local uni. is a distant second, since I work fulltime)?

Currently I'm sticking to inorganic chem, so that should simplify things a bit.

I'm currently studying EdX's Solid State Chemistry, so I hope that'll help some.


texts: Why there is no need for reference standards in High Resolution Mass Spectrometry (HRMS)

texts:
I have a question about HRMS (High  Resolution Mass spectrometry). HRMS is a powerful technique that can discriminate between possible target compounds without the need of reference standards, unlike QqQ (triple quad systems). My question is simple why do HRMS don't need reference standards for analysis?

A short explanation would really help I cannot find the answer online or anything related to it.

Thank you, hopefully I can be helped with this part. I put a section of a book as an attachment maybe that will help.

Greets,
Student


texts: What is the state of stationery phase in paper chromatography?

texts:
Paper chromatography is a kind of partiotion chromatography where stationery phase is water, and I think it should be , because in partiotion chromatography solid is not stationery phase. but as per Wikipedia and this site:http://www.chemguide.co.uk/analysis/chromatography/paper.html

Stationery phase in paper chromatography is paper(a solid) . So which one is correct? Is paper chromatography really a kind of partition chromatography or adsorption chromatography?

The picture is from my textbook: NCERT class 11 ,pg-353


texts:
What is the purpose of a boiling stick when heating a reaction mixture?

I read some stuff online and still don't understand how it works. Does it just ensure that the mixture will boil evenly? If so, then what's wrong when a reaction doesn't boil evenly?

This is the LibreTexts page I was reading information from. I don't understand the terms "bump" and "superheated". If the liquid is above the boiling point, why hasn't it turned into a gas then?


texts: Program that simulates basic reactions in organic chemistry

texts:
To explain - a friend and I have been working on a program that would allow you to draw organic molecules, indicate the conditions, and predict the products.  This would be primarily aimed at basic, first year undergrad organic chemistry (SN1/2, E1/2, applications, potentially (retro)synthesis, etc).

We've realized that it is probably worthwhile to figure out if there are similar existing programs out there.  From what we've read there doesn't seem to be something that meets what we're planning - everything we've found seems to be aimed at professional/higher level chemists, not assisting a beginner.

Basically it comes down to a couple main points:

Are you aware of similar software?
Do you think that this sort of software would be used (either by yourself or students or whoever).
If/when we have a working version, would users here be interested in using/testing it?

I apologize if this doesn't meet the guidelines/standards for questions here, I was kind of iffy about asking it.


texts:
My textbook says the formula for fluoroapatite is $\ce{CaF2 * 3Ca3(PO4)2}$, whereas according to Wikipedia it's $\ce{Ca5(PO4)3F}$.

What is the correct chemical formula of fluoroapatite and why there are different representation of the same compound?


texts: Kinetic Energy Evaluation Integral Evaluation Program Ostlund

texts:
I'm reading Ostlund's Modern Quantum Chemistry. In Appendix B, the kinetic energy integral is evaluated using the Gaussian Basis functions as

T11=T11+T(A1(I),A1(J),0.0D0)*D1(I)*D1(J)
T12=T12+T(A1(1),A2(J),R2).D1(I).D2(J)
T22=T22+T(A2(1),A2(J).0.0D0).D2(1).D2(J)

I understand T11 to be the kinetic energy integral using the first atom orbitals so it will give the kinetic energy of the electron of the first atom, and this is why it is passing zero as the bond length parameter. The same is T22 but for the second atom.

What is T12 used for, aren't T11 and T22 enough to calculate the total kinetic energy?


texts: Validating a method to meet accuracy criteria using precision and accuracy?

texts:
If a method has a precision of 10% and an accuracy of 95 to 105% is required, can this method be validated to meet accuracy criteria? Explain your rationale.

This question was posed by my professor and I'm struggling to come up with an answer.
I understand that precision refers to whether your method gives consistent repeatable results and that accuracy refers to how close your results are to the value you should actually obtain. However, I don't understand how a method's precision and accuracy could validate a method to meet accuracy criteria as the question asks.


texts: Why is it that some liquid mixtures (that exhibit positive/negative deviation from Raoult's law) form azeotropic mixtures at certain compositions? What is the physical reason behind this; are there any extra forces holding the two components together? If so, please elaborate on this.


texts: How to properly relate quantum mechanical energy to the classical world

texts:
The Equation of Interest

The energy equation derived from the "Particle in a 1-D box" problem is as follows:

$E=\dfrac{n^2h^2}{8mL^2}$

where $n$ is the principle quantum number, $h$ is Planck's constant, $m$ is the mass of the particle (e.g. electron), and $L$ is the length of region of space (i.e. box).

The Goal

I would like to illustrate the harmonious nature of this energy equation derived from the quantum mechanical nature of the system and classical mechanics.  In theory we should be able to define a mass and region of space for a clear comparison.

The Example: Electron vs. Car

I want to compute the lowest possible energy of an electron using the equation above.  We define $m=9.11\times10^{-31} \textrm{kg}$ and the region of space as a reasonable value for the diameter of an atom, $L=0.2 \textrm{nm}$.

Plugging this into our equation along with Planck's constant ($h=6.626\times10^{-34} \textrm{ m}^2 \textrm{kg s}^{-1}$) we obtain

$E_{\textrm{electron}} = \dfrac{(6.626\times10^{-34} \textrm{ m}^2 \textrm{kg s}^{-1})^2}{8 *9.11\times10^{-31} \textrm{ kg} * (2\times 10^{-10} \textrm{m})^2} = 1.51 \times 10^{-18} \textrm{ J}$.

Now let us imagine a car with $m=2000 \textrm{ kg}$ and a region of space as $L=1 \textrm{ m}$.  The resulting energy is

$E_{\textrm{car}}=2.74\times10^{-71} \textrm{ J}$.

Now in both cases, the energy is so small that we might as well say its zero (from a classical standpoint anyway).  Of course $E_{\textrm{car}} << E_{\textrm{elecron}}$.

*So we cannot stop here as quantum theory and classical mechanics are virtually indistinguishable (with respect to raw energies) at this point correct?

We can, however, convert these energies (which are purely kinetic energies) into something which is clearly distinguishable such as velocity by using the equation

$E = \dfrac{1}{2}mv^2$

Alternatively,

$v = \sqrt{\dfrac{2*E}{m}}$

where $m$ is the mass of the object and $v$ is the velocity.  If we plug in our previously determined energies we get the following results...

$v_{\textrm{electron}} = 1.8\times 10^6 \textrm{ m s}^{-1}$

and

$v_{\textrm{car}} = 1.7\times 10^{-37} \textrm{ m s}^{-1}$

Here we see that the velocity of the car is essentially zero (or technically speaking, so slow that it wouldn't ever be observed as moving in billions of lifetimes).  This jives with classical theory.  However, we see that the velocity of the electron is staggering, even though the energy of the electron is 'essentially zero'

The Conclusions

So, in order to properly relate the energy equation derived from the quantum mechanical system of a particle in a 1-D box, one cannot simply compare the raw energies of the particle (i.e. electron) to that of an ordinary object such as a car because both energies result in a number that is essentially zero which defeats the point.  As such, one must relate the energy to something appropriate such as the velocity of the object to properly illustrate how the energy equation still relates to everyday life.

The Question

Are my conclusions correct or can the raw energetics simply be used to make a proper comparison between quantum/classical theory without resorting to recasing the results into a physical property such as velocity?

#not-homework


texts: Does temperature affect the %oxygen in air by volume? (even though oxygen density varies inversely with temperature according to P/RT=n/V)

texts:
I want to investigate how temperature affect the concentration of oxygen in air as it will affect how much oxygen we inhale per breathe. Oxygen by percent composition in air is 20.95%. However, the oxygen concentration/density in air varies due to the expansion of gas particles and varies inversely wth temperature according to P/RT=n/V (where n/V is the density of gas).

I did an experiment that involves the rusting of steel wool to determine the percent oxygen in air by volume (determined by volume of water rose in a test tube divided by the total volume of air in the test tube). However, I'm not sure if the % oxygen I determined is a measure of the oxygen density (if so I can convert the percentage to ppm).

My initial hypothesis is that as there are less oxygen molecules in hot air, water level will rise less since there is less oxygen reacting with the steel wool (compared to cold air). Hence lower % oxygen concentration. Vice versa for cold air.

Then later, I'm thinking that as oxygen molecules (or any gas particles) are heated, they move quicker so each oxygen molecule will occupy more volume. Vice versa if the gas particles are colder. However, since there are more oxygen molecules in cold air than warm air, the increase in number of oxygen molecules will occupy more volume and make up for the smaller volume each oxygen molecule occupy by slower movement.

Therefore, the % oxygen in air by volume I determined by the volume of rising water level over the volume of air, will theoretically be the same and hence it can't be used to determine the oxygen density in air.

But then I also saw a picture of a vernier O2 probe with percentage O2 reading (which im not sure if it's percent by volume or percent composition) that can be converted to concentration in ppm by a click of a button. I then did some research and found out percentage concentration (by mass or by volume) can be converted to ppm (which will be a measure of oxygen density).


texts:
$\ce{2Ca3(PO4)2 +6SiO2 +10C->6CaSiO3 +P4 +10CO}$

What is the maximum amount of P4 that can be produced from 1.0 kg of phosphorite if the phosphorite sample is 75% $\ce{2Ca3(PO4)2}$ by mass

I am confused. How do I find a maximum amount of a reaction


texts: How to prepare and store anisaldehyde tlc staining solution? What will be the color of this solution? What is its shelf life?

texts:
I prepared  anisaldehyde charring solution,  and refrigerated it.  Its color was yellow.
However when I am using it for staining tlc plate,  it is giving  dark pink color on tlc plate surface and unclear blue stains...  Also not all the stains are visible.  If I am not wrong it should have white background  with dark brown spots appearing clearly.

What mistake I am doing here possibly?


texts: Does negative pH mean it is a stronger acid than one with positive pH?

texts: I've searched this site but I don't think this has been asked yet. Does negative pH indicate a stronger acid than a positive pH (since it's further down the scale)? I'm asking this because in one of the problems from my homework set, they asked "which of the following solutions contains the strongest acid?" and one of the options yielded a negative value.


texts: I know that a certain gas is soluble in water but not in alcohol. How can I find the solubility of the gas in mixture of water and alcohol? Do I use a simple linear relation? The gas in question is not a noble gas, but does not react with either liquid.


texts: Can't decide between E1 and E2 mechanisms for this reaction

texts: I can see that due to the substrate being bulky, an elimination reaction will take place and not substitution. The reagent is a strong base. E1 reactions are independent of the base chosen, and E2 requires strong base. There is no information about the geometry of the substrate (i.e., whether the beta hydrogens are anti to the halide). How do I decide between the two mechanisms?


texts: Does the salt bridge in a galvanic cell deplete over time?

texts:
I searched for the answer for this question on Wikipedia and Stackexchange  a lot but couldn't find same question or a required answer in some other similar question.

I understand that the function of the salt bridge is to complete the circuit and maintain electrical neutrality in both the half cells of a galvanic cell. This is achieved by movement of cations and anion in the salt bridge. the anions move towards anodic half cell and cations move towards cathodic half cell.

My question is-
Are these cations and anions are provided by salt bridge itself and it depletes over time as the electrochemical reaction progresses?

OR

Is salt bridge is just a medium and passing the anions from solution of cathodic cell to anodic cell and passing the cations from solution of anodic cell to cathodic cell?

OR

Both of this happens?

I will be grateful for insight on this topic.


texts: Proper definitions of resistivity of conductivity

texts:
Is resistivity the same as specific electrical resistance?
And conductivity is same as specific conductance when I am dealing with electrical properties ?


texts: Why are there 3 columns in Group VIII of the Periodic Table?

texts:
I'm currently reading in-depth about the layout of the Periodic Table, and I wondered why the table has 3 columns in its Group VIII:

As I understand, this is an old notation of the table, now deprecated. But why was Group VIII a triple-sized group?

The answer might be trivial, but it's interesting.


texts:
I was wondering:

How is the specific heat of an alloy obtained?

My first attempt is to assume a thermal equilibrium between a mechanical solution and an homogeneous solution of two metals, A and B.

\begin{align*}
    Q_{A+B}&=Q_A+Q_B\\
    n_{A+B}C_{A+B}(T_{eq}-T_{A+B})&=n_{A}C_{A}(T_{eq}-T_A)+n_{B}C_{B}(T_{eq}-T_B)\\
    C_{A+B}(T_{eq}-T_{A+B})&=\frac{n_{A}}{n_{A+B}}C_{A}(T_{eq}-T_A)+\frac{n_{B}}{n_{A+B}}C_{B}(T_{eq}-T_B)\\
    C_{A+B}(T_{eq}-T_{A+B})&=X_AC_{A}(T_{eq}-T_A)+X_BC_{B}(T_{eq}-T_B)\\
    C_{A+B}&=\frac{X_AC_{A}(T_{eq}-T_A)+X_BC_{B}(T_{eq}-T_B)}{(T_{eq}-T_{A+B})}
\end{align*}
Where Q=heat, C=specific heat, n=moles, X=molar fraction and T=temperature.

Is it correct?

Is there another way of doing this?

I have previously searched and this are some relevant things on Chem.SE what I have found:

What is this equation for?
Properties of steel and aluminum alloys

I did not find a solution or an approximation in any of those links.

My aim is to prepare a class and teach my students how to determine the specific heat of any alloy, if possible, without going to a lab. (There is no basic infrastructure for special labs).


texts: How to I find the equilibrium temperature in this problem?

texts:
From Castellan's Physical Chemistry, chapter 12 [1, p. 276]:

  12.18 At $\pu{25 °C}$ we have for rhombic sulfur: $ΔG_\mathrm{f}^\circ = 0,$ $ΔS^\circ = \pu{31.88 ± 0.17 J K-1 mol-1};$ and for monoclinic sulfur: $ΔG_\mathrm{f}^\circ = \pu{63 J mol-1},$ $ΔS^\circ = \pu{32.55 ± 0.25 J K-1 mol-1}.$ Assuming that the entropies do not vary with temperature, sketch the value of $μ$ versus $T$ for the two forms of sulfur. From the data determine the equilibrium temperature for the transformation of rhombic sulfur to monoclinic sulfur. Compare this temperature with the experimental value, $\pu{95.4 °C},$ noting the uncertainties in the values of $ΔS^\circ.$

I have plotted the graph of $μ$ vs $T$ successfully, but unable to find the equilibrium temperature. The answer is showing 119 °C and possible range from 83 °C to 277 °C.

How do I find it mathematically? I have used the equation $\mathrm d\mu = -S\,\mathrm dT + V\,\mathrm dp,$ but lot of the things are unknown. Can anyone solve it completely with calculation?

References

Castellan, G. W. Physical Chemistry, 3rd ed.; Addison-Wesley: Reading, Mass, 1983. ISBN 978-0-201-10386-1.


texts: Shift of the null half-reaction potential

texts: If we change the null half-potential, would it change half-potentials of other half-cell reactions by the same amount, so that voltages of net reactions stay the same?


texts: Why does basicity go down along the group 15 hydrides?

texts:
As we go down Group 15, the sizes of atoms increase and these are the central atoms in their corresponding hydrides. Shouldn't the large size of central atom (in case of $\ce{Bi}$) actually help the lone pair inside the $\ce{sp^3}$ hybrid orbital to easily be donated and thus increase the basic character down the group?

$\ce{N}$ is small and shouldn't it hold lone pair with much more strength than others, but $\ce{NH3}$ seems to be strong base while $\ce{BiH3}$ is the weakest one.


texts: Why derived name of nomenclature is used for Alkanes and alcohols only?

texts:
My chemistry textbook says derived system of nomenclature of organic compounds is only limited to alkanes and alcohols!

What is the reason behind it? Is it chemical or like a ritualistic/cultural?


texts: Reaction of mixed carbonyl compound with ethylene glycol in acidic medium

texts:
I Know that there is cyclic ketal or cyclic acetal is formed when carbonyl compound reacts with ethylene glycol. But I am confused here because I am unable to decide what will be the major product  formed here because there are two possibilities, i.e. cyclic ketal and cyclic acetal.
Can anyone help me in reasoning what will be the major product and why? Also, I want to know the role of dry $\ce{H+}$ in this reaction.
I think the cyclic ketal should be formed as major product because the oxygen of ketone will be more willing to donate lone pair to $\ce{H+}$ and react. Is it correct?


texts:
A steel sample ($\pu{0.3500 g}$) was dissolved in nitric acid and the resulting solution made up to $\pu{500 ml}$. The absorbance of this solution measured by atomic absorption was found to be $0.410$. A standard $\pu{6 ppm}$ solution of $\ce{Ni}$ gave an absorbance of $0.522$ under the same conditions. Assuming linearity between absorbance and concentration, calculate the $\% \ce{Ni}$ in the steel sample. (8 marks)

Seems so simple but is confusing me.
A steel sample ($\pu{0.3500 g}$) was dissolved in nitric acid and the resulting solution made up to $\pu{500 ml}$.The absorbance of this solution measured by atomic absorption was found to be $0.410$.
A standard 6 ppm solution of Ni gave an absorbance of $0.522$ under the same conditions.
In the final diluted sample,
$$\frac{\pu{6 ppm}\ \ce{Ni}}{0.410\times0.522}=\pu{28.03476311 ppm}\ \ce{Ni} \tag{1 }$$
In the first solution
$$\frac{\pu{28.03476311 ppm}\ \ce{Ni}}{\pu{500 ml}}=\pu{0.05606952622 mg}\ \ce{Ni} \tag{2}$$
Supposing the density of the first solution to be near that of water:
$$\pu{1000 g}\times\pu{0.05606952622\times10^{-6} g}=\pu{5.60695\times10^{-5} g} \tag{3}$$
In the steel sample:
$$\frac{\pu{5.60695\times10^{-5} g}}{\pu{0.35 g}}=0.000160198=0.016\ \%\ \ce{Ni}\tag{4}$$
$2$nd attempt:
\begin{align}
\frac{\pu{6 ppm}}{0.522}&=\frac x{0.410}\\
\implies \frac{\pu{6 ppm}\times0.410}{0.522}& =x\\
x&=\pu{4.7126ppm}\ \ce{Ni} \tag{6}
\end{align}
This means you have $\pu{4.7126 mg}$ nickel per $\pu{1 kg}$ of steel (ppm is one millionth, and thus, mg per kg). Then one tenth of that amount of steel $(\pu{0.1 kg}/\pu{1 kg})$ contains $1/10$ of the $\ce{Ni}$. that is $\pu{0.47126 mg}$
Since it was marked up to $\pu{500 ml}$
In the steel sample:
\begin{align}
\pu{0.47126 mg}\times\frac{500}{50}&=\pu{4.7126 mg ml-1}\\
\frac{4.7126}{100}&=0.047126\\
\frac{\pu{0.047126 g}}{\pu{0.35 g}}&=0.134645\\
&=13.46\ \%\ \ce{Ni} \tag{7}
\end{align}
I feel that I am missing a step in calculations. I would prefer to read a resource of working this out myself than finding the answer.
I feel more confident in my second attempt of finding a correct answer.
This question is from a past paper.


texts: Do I need to include lattice energy when calculating the energy required to vaporize NaCl?

texts:
I understand that the lattice energy is the energy released when a crystal forms and that's the reason it takes the negative sign. But do we need to add this energy again when we are trying to vaporize an ionic compound ?

For example, let's assume we want to completely vaporize a mole of NaCl starting at room temperature, how much energy do we need ?

I don't know neither the specific heat nor the latent heat of vaporization of NaCl, but I understand we would need:

1- Energy to raise the temperature of mole of NaCl from 298 °K to its boiling point.

2- Energy equal to the latent heat of vaporization of a mole of NaCl.

I don't know whether NaCl would go through the liquid state or not, but if it does then we would need to add the latent heat of fusion too.

Now, according to wikipedia, NaCl has a lattice energy of −756 kJ/mol. So my question here is: do we need to add this lattice energy to the calculated steps above to account for all the energy required to vaporize a mole of NaCl ?


texts: what is the exact meaning of oxidation state?

texts:
can you mention the concept of oxidation state without its simple definition i-e it is the apparent charge +ve or -ve.....
I found these in wikipedia but didn't understand."Conceptually, the oxidation state, which may be positive, negative or zero, is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic, with no covalent component. This is never exactly true for real bonds.". what does it mean? please clear with example if possible.


texts: What does Ae mean when used in a chemical formula?

texts:
In this video on slide 38 for example, the 35 minute mark, the formula appears

HAeBe

With the explaination "some chemestry has taken place..." and an infrared spectra.

What is Ae? I tried looking it up thinking it might be a common shorthand, but the only hits are answers that say "no, did you mean Al, Ag, etc.".


texts: Preparation of Saturated Salt Solutions - W/O Being Wasteful

texts:
Question

What is the most cost effective way to prepare saturated solutions of each of these compounds? LiCl, K2CO3, and NaCl.

Background

I am trying to create a rudimentary controlled humidity device within my lab. I am essentially taking a desiccator, removing the desiccant, cleaning thoroughly, and inserting various saturated salt solutions in order to have a controlled vapor pressure of water above the surface of the saturated solution; assuming there is a constant temperature.

I have included a temporary link to the two journal articles I am using to try and accomplish this goal, but I will try and give all the relevant information here as well so people don't have to go and check out my shadylinks.Dropbox w/ journal articles

I have the salts needed to make up solutions of LiCl, K2CO3, and NaCl. They were quite expensive for our small research group though and I don't want to waste any materials. The volume in the bottom of the desiccator is about 200mL and I have 100g of each salt to use for the course of the short experiment.

I know that a saturated solution in general chemistry is simply prepared by dissolving as much salt as is possible into a heated solution and then cooling it. However, as I have been reading some of these papers there are many reports of non-diffusing barrier layers on the surface of many saturated salt solutions. This means that the relative humidity of these solutions changes a significant amount over time. Some papers report the use of "slurries" or "sludges" in which just enough water is added to a pile of salt in order to make it appear damp.

I have also read that the preparation of a saturated salt solution is very dependent on the relative humidity which is established by that salt solution. More specifically, that low rel. humidity saturated solutions might need the slurry approach and higher rel. humidity solutions favor the standard saturation techniques. However, I have no idea what the cuttoff for "low" and "high" is and I am left to assume it's whatever the atmospheric humidity is.

I am more than happy to do the legwork and read up on as much as need be, and I am still doing so as this post sits. I just don't know where to go or how to approach the question of how much saturated solution, or how much slurry, will be enough to control the humidity inside of about a 1L container. I can't afford really to go about preparing the solutions in order to find the best method experimentally and I was really hoping there were some experienced people out there who could point me in the right direction.

Thank you for all of your time reading this regardless of response! It is much appreciated!


texts: Predicting the temperature of an object using the heat of its surroundings after a certain amount of time?

texts:
how would you predict what the temperature of something would be if it spends a certain amount of time exposed to heat from its surroundings? is this possible?

ex. what temperature would a hot bottle of water at initial temp 48 C be after being put in a 4 C refrigerator for 2 hours?