texts: Lucas test in the presence of EWG like -CN

texts:
Does the given compound give Lucas test?

My teacher says due to the presence of a strong electron withdrawing group the carbocation formed is unstable.
But I say if it undergoes $\mathrm{S_N2}$ mechanism then an electron withdrawing group should increase its reactivity. Why then does this compound not give the test?


texts: How to refine manganese metal from manganese(IV) oxide found in batteries?

texts:
I opened up some lantern batteries, and inside there's $\ce{MnO2}$ powder, carbon rods, and zinc casings, and other stuff that I don't know what it is exactly. I scraped out $\ce{MnO2}$-containing powder, but I would like elemental manganese from it.
How can I obtain manganese from manganese dioxide? How strong a reducing agent do I need? How hot does it need to get? Can I just add charcoal powder and smoke it with an oxyacetylene torch?


texts: Difference between free energy of formation and free energy of combustion

texts: I was wondering what is the main difference among those two values.


texts: Why would hydrogen not be generated at the cathode when electrolysing zinc sulfate?

texts:
Describe how zinc metal can be obtained from zinc sulfate solution by electrolysis.
  A labelled diagram is acceptable. Include all the products of this electrolysis. The electrolysis is similar to that of copper (II) sulfate solution with inert electrodes.

The answer key says that zinc would be formed at the cathode. However, zinc is more reactive than hydrogen, so logically hydrogen should be given off at the cathode, not zinc.

As I understand it, the ions involved in this electrolysis are $\ce{Zn^2+}$, $\ce{H+}$, $\ce{OH-}$ and $\ce{SO4^2-}$.

Also, why can possible cathodes in this reaction be carbon, platinum OR zinc while the anode can only be carbon or platinum? What allows the cathode to be zinc?


texts: Can pthalic acid or 1,2-Benzenedimethanol be possible products of Cannizzaro reaction of phthalaldehyde?

texts: I know the main product that is ortho-hydroxymethyl benzoate ion but I think that phthalic acid and catechol must be formed also in very small amounts but I am unable to get any confirmation from the internet. Please help me with the products.


texts: What would happen if I mix salt and sugar in a cup of water?

texts:
If I mix water in a cup with sugar at some stage the solution will become saturated and no more sugar will dissolve into the water. If I now add salt to the solution will the salt dissolve into the water or is the solution already saturated?

I have not tried an experiment as I cannot figure out how to measure the dissolved component of the 2, intuitively I think that some salt will dissolve, but not as much as in a pure salt water mixture.


texts: I mean doesn't every compound has its own different reduction and oxidation potential ? Or its just one potential that can be compared to understand which one will get reduced and which one will get oxidised ?


texts:
I had a doubt while reading about the saponification reaction of esters in basic medium. What is the molecularity of the reaction and why?
P.S - I think its bimolecular and heres why -
The RDS of the reaction is the formation of the tetrahedral intermediate after the attack of  the OH ion. In this step both the ester and the hydroxide ion are involved (The ester is shifting the carbonyl bond electrons to the oxygen and the hydroxide is attacking the electrophilic carbon). Therefore, the molecularity should be two.


texts: Electrolysis of Potassium Iodate/Hydrogen Peroxide in Briggs-Rauscher Oscillation

texts:
I would like to investigate the effect of adding a voltage in the Briggs-Rauscher oscillation reaction. I will examine the oscillations visually.

The ingredients I will use include potassium iodate, sulfuric acid, acetone, manganese sulfate, starch indicator and hydrogen peroxide.

There are a number of complex reactions which have not to this day been completely analysed. Hence I will not attempt to explain all of them.

To the point. What electrodes should I use for electrolysing potassium iodate? Just like the saltwater circuit, would electrolysis will proceed as iodine carries charges towards the aluminium anode, and as potassium obtains them in the copper cathode? Could I electrolyse hydrogen peroxide alternatively?

I would like to examine reduction potentials, comparing them to what extent the electrolysis of potassium iodide prevents the behavior of potassium iodide in the other equilibria, as possibly seen visually.

Is it also possible for the manganese metal to conduct with copper just as potassium might?


texts: How to determine if two calibration curves are parallel, within 5%

texts:
I have complex matrices and I need to make sure the matrix does not affect the measurement of my analyte. To do that, I need to prepare samples of my analyte in a solvent and of the matrix reinforced with my analyte. Both curves are going to have 5 concentration points, each done 3 times and, for sake of argument, let's assume both have comparable levels of precision. Then, I linearize these two calibration curves and check if they are parallel, which is where my question lies.

How do I prove that both curves are parallel (meaning no matrix effects are present), within a margin of 5%?

I have found the following method:

Get the y-data of the matrix data and apply them to the calibration function of the solvent and get an "apparent concentration" of the matrix.
Perform a linear regression of the concentration values of the solvent with the apparent concentrations of the matrix.

Then, I have an intercept a and a slope b. A value of b different from 1 indicates a concentration dependent bias. I have both standard deviations of the fit, stdev_a, stdev_b, so I have to determine the confidence interval (95%) of b and check if their values are withing these confidence intervals.

I have found two ways to do that in Excel and I am unsure which one is correct. For example, the slope:

Do I use the conf = CONFIDENCE.T(0.05, stdev_b, N-4), get b+-conf, and check if 1 is within this interval b+-conf?
Do I use t = T.INV(0.95,N-4), multiply that by the stdev_b, get the range b+-t*stdev_b and check if 1 is within this range?

I have used N-4 for the degrees of freedom, since it's two linear regressions, each consuming one degree of freedom, correct? In this case, N-4 == 11.

In summary:

Which function do I use to calculate the confidence intervals for this example in Excel, and
Is this method of checking parallelism correct?
Is there an easier/simpler or more correct way of doing this parallelism check?


texts: What is the formula for vapor pressure of liquid related to surface tension of liquid? I know that if the surface tension increases, vapor pressure will decrease. Toluene evaporates faster than ethanol even though it is having more surface tension. How can I relate vapor pressure and surface tension between every solvent through a formula?


texts: Combinatorics of Molecule given the Elements

texts:
I have search a lot on Internet and my own researches on a sheet of paper failed to found an analytical closed formula for the following problem:

Considering:

Common ranges of temperature and pressure
A FINITE number of given pure elements with their respective valence

Found a lower-bound of all possible complete/incomplete molecules formed involving ALL the given elements (ignoring valences that are indistinguishable).

Examples:

Given one C, one H. We can form only one "incomplete" molecule: CH (lowerbound=1)
Given two H. We can form only one "complete" molecule H_2 (lowerbound=1)
Given one O and two H. We can form H_2 but also H_2O, but also incomplete HO (lowerbound=3)

Thx for feedback


texts: How did early chemists measure mass of atoms?

texts:
Here a book says that Berzelius measured atomic masses using a simple lab and his measurements was so close to modern results. Can someone explain how a person living in 19th century was able to measure atomic masses? Like he took this and those, observed this and that and did something else. Can I repeat his experiments at home too and get his results?

Do I actually understand atomic mass right? For me it is a mass in gramms of one atom of an element.

Also, I can't understand how Gay-Lussac measured the volumes of gases reacted with each other. What does the book mean by saying 2 volumes of Hydrogen? How much are 2 volumes? Are they measured in m^3 or what?

Please try to avoid the use of moles in answers as I don't understand why we need moles actually. So, I think I need to understand questions above first before moving to moles.


texts:
need some help with NIOSH 7300 method https://www.cdc.gov/niosh/docs/2003-154/pdfs/7300.pdf

I have two 37mm cellulose filter paper, one is my filter blank while other is sample. The sample has 80L of natural gas passed through and I plan to test for Mg , final concentration in mg/kg.

Both are digested and top up to 10 ml with dilution acid.

ICP OES Result:

Filter Blank : Mg = 0.022 mg/L , Pb = 0.002 mg/L

Sample       : Mg = 0.038 mg/L , Pb = 0.006 mg/L

(From Method)
Given the formula is

Solution concentrations for the sample, Cs(µg/mL),

Filter blank , Cb(µg/mL)

Volumes of sample, Vs(mL), and Filter blank , Vb(mL),

calculate the concentration,C (mg/m3), of each element in the air volume sampled, V (L):

C= (CsVs - CbVb)/V = mg/m3

NOTE: µg/L / mg/m3

My calculation,

[(0.038 mg/L x 0.01 L) - (0.022 mg/L X 0.01 L)]/ 80L

= 0.00016 mg/ 80L

Edit:

According to the composition result, density is = 17 gmol-1 ,
and I calculate this under STP.

= 0.00016 mg / [(80/22.4)mol * (0.017kg/mol)]

= 0.00263 mg/Kg

is this correct?


texts: How does a Lewis acid differ from an oxidizing agent; Lewis bases from reducing agents?

texts:
A Lewis acid is defined as an electron acceptor. An oxidizing agent is also defined as an electron acceptor (in the electronic theory of oxidation).

So then what is the basic difference between an Lewis acid and an oxidizing agent?

Similarly;

A Lewis base is defined as an electron donor (Lewis theory). A reducing agent is also defined as an electron donor (electronic theory). Therefore, what is the difference between Lewis bases and reducing agents? Are they exactly same thing?

There is a similar question which, however, only considers bases and nucleophiles and does not go into detail about oxidation and reduction.


texts: Transition state optimisation on the surface of periclase

texts:
I want to model a reaction catalysed by periclase ($\ce{MgO}$) using DFT.
I have a good guess on the transition state (TS) of the reaction that goes in gas phase/solvent (produced using MOPAC).

The proposal for this reaction goes by the Eley–Rideal mechanism and I have a good guess on how the reactant adsorbs.

Now comes the question: I would like to optimise the TS on the surface using DFT (either ORCA or NWChem), but in tractable time.

I am tempted to use a simple, fixed model for the surface, e.g., a set of fixed atoms in bulk arrangement.
Can this work?
How am I supposed to find a structure with just one imaginary frequency using a partially fixed model (maybe using some clever vibrational projections)?

Even though NEB could be applied, the implementation of it in NWChem does not work with fixed atomic coordinates.
Besides, I am confident on the TS I found without the catalyst, so I would like to use that instead of starting all over again.

Edit: what about using a very small cluster model, say, 8-16 atoms, and let it relax? Do you think it could work (in the sense of giving a reliable TS in terms of geometry and energy)?


texts: Syn-addition or anti-addition to fumaric acid?

texts:
In my textbook, the addition of alkaline $\ce{KMnO4}$ to fumaric acid (trans) is stated as a syn-addition even though $\ce{OH}$ is present on opposite sides in the product.

But,the defination of syn-addition is:

  Addition of electrophile and nucleophile on the available sites on the same side of molecule.

Isn’t this contradictory?


texts: why do we modelize an electronic double layer with a classic capacitor?

texts: in an electronic double layer, there is a voltage drop between the metal and the solution but in the litterature, scientists always modelize EDL with a classic capacitor. My question is why ? because for me, the two electrodes have not the same potential (+/-), it is assymetric ...


texts: What is the non-ideal equivalent of mass action kinetics?

texts:
Starting from the equations of mass action kinetics, one may show that (for suitably chosen numbers $A_i$), the function $\sum_i x_i(A_i + \log x_i)$ is a Lyapunov function, i.e. it decreases over time.

Apart from an irrelevant factor of $RT$, this is the expression for the free energy of an ideal solution (or ideal gas, etc). So it seems that mass action kinetics carries with it an assumption that the reactions are taking place in an ideal solution.

I'm interested in how to think about kinetics in non-ideal solutions, but I haven't been able to find any information about it. Is there a standard set of kinetic equations that remain valid when the chemical potential is given not by $\mu_i^0 + RT\log x_i$ but by $\mu_i^0 + RT\log \gamma_i x_i$, for activity coefficients $\gamma_i$ that depend on the concentrations?

There are several alternatives to mass action kinetics that I know about, such as Michaelis Menton kinetics for enzymes - but these are actually derived from mass action kinetics applied to elementary steps, so they don't seem to be able to escape from the assumption of ideality.


texts: Ammonia for cleaning - what is the interaction between ammonia and oils?

texts: Household ammonia is recognized as being an excellent cleaner for grease and oil. My question is, how does this work? Does ammonia merely put the oils into a suspension, like a detergent does? Or is there a more significant chemical reaction between the two - along the lines of how enzymes affect oils?


texts: Why does Mg2+ have the ionic radii bigger than Ca2+

texts: If they were atoms, $\ce{Mg}$ should have a smaller radii. How does this change?


texts: Calculate the lattice energy of ammonium carbonate

texts:
The lattice energy is a measure of the stability of a compound and I need this data for the ammonium carbonate ($\ce{(NH4)2CO3}$) but I don't know how to calculate and I can't find it anywhere. I know that it can be calculated with the Born-Lande equation but I don't know how to apply this equation to solve my problem.

I wonder if anybody knows a database where I can find this value, I need it for an important chemistry assessment.

Thank you for your help


texts: How to calculate Hirshfeld charges from Gaussian?

texts:
I am new to Gaussian and want to calculate Hirshfeld charges from Gaussian 09 or 16.
I found this input file for Methanol:
%nproc=8
%mem=1600mb
# mPW1PW91/6-311+G(2df,2p) pop=Hirshfeld scf=tight
Methanol
0 1
8 -0.046153000 -0.751257000 0.000000000
6 -0.046153000 0.658469000 0.000000000
1 0.857779000 -1.062372000 0.000000000
1 -1.086394000 0.976180000 0.000000000
1 0.437376000 1.072716000 0.889654000
1 0.437376000 1.072716000 -0.889654000

but when I run it I get this error:
QPErr --- A syntax error was detected in the input line.
 p) Pop=Hirshfeld scf=tight Methanol 0 1
                            '
 Last state= "GCL"
 TCursr=      3523 LCursr=        51
 Error termination via Lnk1e in /opt/software/gaussian/g09.e01/l1.exe at Wed Aug 19 01:02:31 2020.
 Job cpu time:       0 days  0 hours  0 minutes  0.6 seconds.
 File lengths (MBytes):  RWF=      5 Int=      0 D2E=      0 Chk=      1 Scr=

Any suggestion which part is the problem?


texts: What is non-hückel double bond of Aromaticity?

texts:
Chemistry of Aromaticity. What's non hückel double bond ?
What are the difference between hückel and non-hückel double bond ?
[ Here, in figure the green one is non hückel double bond ]


texts:
Using Lewis structures to describe chemical bonds inside a molecule is still fairly common start in undergraduate education. Lewis structure however can be misleading, or just simply wrong in many cases. Mostly I see this with aromatic systems, Diels-Alder reactions etc.

My question is if there is a rule of thumb when one can safely use Lewis structure and when we should just  forget them? Or should I just check it every single time and compare them with eg. MOs?


texts:
You and a co-worker have developed a molecule that has shown potential as cobra anti-venom ($\ce{AV}$). This anti-venom works by binding to the venom ($\ce{V}$), thereby rendering it non-toxic. This reaction can be described by the rate law, $\text{rate} = k\left[\ce{AV}\right]^1\left[\ce{V}\right]^1$.

You have been given the following data from your co-worker: $\left[\ce{V}\right]_0=0.20\ \mathrm M$, $\left[\ce{AV}\right]_0=1.0\times10^{-4}\ \mathrm M$. A plot of $\ln\left[\ce{AV}\right]$ versus $t$ (s) gives a straight line with a slope of $-0.32\ \mathrm s^{-1}$. What is the value of the rate constant ($k$) for this reaction?

My logic tends to fail me on this question. So to start off, the overall  reaction order is 2, thus the equation is: $${A}^{-1}=kt+{a}^{-1}$$ However, we're only given a $k$ value for the law: $\text{rate}=k\left[\ce{AV}\right]$. I'm lost as to how to proceed next. Given the k we can calculate the initial rate of $\left[\ce{AV}\right]$ but how is this going to help me find the $k$ for $rate=k\left[\ce{AV}\right]^1\left[\ce{V}\right]^1$? I suspect something tiny that I missed in this problem, any directions or hints would be appreciated!


texts: Relating change in internal energy and to that in enthalpy

texts:
The question is

  For which exothermic reaction is $\Delta\,E$ more negative than
  $\Delta\,H$?

  (A) $\ce{Br2(l) <=> Br2(g)}$

  (B) $\ce{2C(s) + O2(g) r 2CO(g)}$

  (C) $\ce{H2(g) + F2(g) -> 2HF(g)}$

  (D) $\ce{2SO2(g) + O2(g) r 2SO2(g)}$

r is supposed to be reaction? Either a one headed or equilibrium arrows. The "correct" answer is supposed to be D.

However, using the formula $H = U + PV$ to $\Delta H = \Delta U + \Delta PV$, I found that $\Delta U$ would be less if $\Delta V$ was positive.

Thus, more gaseous products should be produced. As a result, I chose B.

Note, A is not exothermic, so would not be considered.

Could anyone confirm my answer or offer an explanation for my answer being wrong?


texts: How does hyperconjugation explain stability of partial positive charges?

texts:
Recently I was reading this answer to the question Why does boron add to the less substituted carbon in the hydroboration of an alkene?.
See the transition state given in the above answer, and the reason given to explain it's stability.

As far as I know, hyperconjugation is a result of σ-p interaction in carbocations.
If partial charges are developed(as in the case of linked answer), there is no empty p orbital in them.

So how can hyperconjugation be used to explain their stability?


texts: Which is more stable: isobutylene or cis-2‐butene?

texts:
How do you compare which is more stable without using the heat of hydrogenation or combustion or any other numeric factual value:
$\ce{(CH3)2-C=CH2}$ or $\ce{CH3-CH=CH-CH3}$ (cis)?


texts: Experiments in chemistry involving use of stereo microscope?

texts: I recently got a decent stereo microscope. Besides using the scope to teach my children, I have been thinking of picking up something new to learn myself. I have been interested about chemistry for a long time but never studied it after upper secondary school. I was thinking would there be some experiments that would allow me to learn more microscopy and chemistry at the same time? I have ~10  years of experience in machine vision, signal processing, neuroscience, programming etc., so research-grade problems are welcome too.


texts: How to get the second electron affinity of tellurium?

texts:
I need the value of the second electron affinity of Te, i.e. the energy change associated with the attachment of an electron to a $\ce{Te-}$ anion
$$\ce{Te- + e- -> Te^{2-}}$$
In the books (e.g. J. Huheey, E. Keiter, R. Keiter; Inorganic Chemistry: Principles of Structure and Reactivity, 4th Ed.) I find second electron affinities only for certain elements from the periods 2,3,4 of the Periodic Table but not for tellurium.

I found a paper[1] that shows how to calculate the second electron affinities, for different elements, and gives an example how to do it for the oxygen.

The calculations use Coulomb and exchange integrals $\mathrm{J_{xy}}$ and $\mathrm{K_{xy}}$ for two electrons in different 2p orbitals, and with the same spin.

Do I understand correctly, for tellurium, I need the values of these integrals for two electrons in different 5p orbitals, and with the same spin?

Is there any software package where I can calculate these integrals or is there a paper or a book where these values are calculated? Is there another way to calculate the second electron affinity of Te or a paper where it is calculated or measured?

Reference:

Pearson, R. G. Negative electron affinities of nonmetallic elements. Inorg. Chem. 1991, 30 (14), 2856–2858 DOI: 10.1021/ic00014a008.


texts: Do you assume undrawn hydrogens are pointing away from you when determining R/S?

texts: When determining R/S of stereoisomers, the group with the smallest atomic number needs to be in the back (dashed line). But if no group attached to a chiral center is drawn in dashed line, do we assume that the undrawn hydogren is dashed? I have attached an example below, the chiral center is circled in red. Thanks


texts: $Q_3$ is symmetric with respect to the $\sigma_v$ operation?

texts:
I am currently studying the textbook Infrared and Raman Spectroscopy: Principles and Spectral Interpretation, second edition, by Peter J. Larkin. Section 8. Symmetry: Infrared and Raman Active Vibrations, says the following:

Fig. 2.15 shows the Cartesian displacement vectors (arrows) of the vibrational modes $Q_1$, $Q_2$, and $Q_3$ of the bent triatomic $\ce{XY2}$ molecule (such as water), and shows how they are modified by the symmetry operations $C_2$, $\sigma_v$, and $\sigma^\prime_v$. For nondegenerate modes of vibration such as these, the displacement vectors in the first column (the identity column, $I$) are multiplied by either (+1) or (-1) as shown to give the forms in the other three columns. Multiplication by (+1) does not change the original form so the resulting form is said to be symmetrical with respect to that symmetry operation. Multiplication by (-1) reverses all the vectors of the original form and the resulting form is said to be antisymmetrical with respect to that symmetry element. As seen in Fig. 2.15, $Q_1$ and $Q_2$ are both totally symmetric modes (i.e., symmetric to all symmetry operations), whereas $Q_3$ is symmetric with respect to the $\sigma^\prime_v$ operation but anti-symmetric with respect to the $C_2$ and $\sigma_v$ operations.

It is this part that concerns me:

As seen in Fig. 2.15, $Q_1$ and $Q_2$ are both totally symmetric modes (i.e., symmetric to all symmetry operations), whereas $Q_3$ is symmetric with respect to the $\sigma^\prime_v$ operation but anti-symmetric with respect to the $C_2$ and $\sigma_v$ operations.

Shouldn't it say that $Q_3$ is symmetric with respect to the $\sigma_v$ operation, since this is the same form, and anti-symmetric with respect to the $C_2$ and $\sigma_v$ operations? It seems like a typo to me.
I would greatly appreciate it if people would please take the time to clarify this.


texts: Thermal Grease is used to remove the air gaps between CPU and heatsink. However, computing aside, what would determine the max temp that the grease can handle before it burns or breaks down?


texts: Where can I find a complete and accurate table of CPK colours?

texts: I have been using several chemical drawing softwares including MarvinSketch, Jmol, Accelrys DS Visualizer, Avogadro, etc., all of which I have set to CPK colouring. Despite this supposedly common setting I have noticed that fluorine atoms are coloured rather varyingly from software to software. For example, MarvinSketch uses orange, Accelrys uses cyan as does Avogadro and Jmol uses algae green for fluorine atoms. I have tried Googling for the answer but I have only found incomplete tables, aside from on the Wikipedia website but I am dubious as to using Wikipedia for this information due to its reputation for inaccuracy.


texts: Extracting Zinc (oxide) from baby powder

texts: I have a bottle of baby powder that is 15% Zinc oxide and the rest is talc. Is there an over-the-counter way of purifying zinc oxide from it? I'm trying to make some sunscreen from it.


texts: Is it possible to chemically treat grass to make it digestible?

texts: Is it possible to chemically treat grass after "harvesting" it to make it digestible by humans?  I know we can "eat" grass, but we can't break it down in our stomachs. If there is some chemical treatment to partially break grass down into something we can digest, I see it possibly being used to end world hunger!  I know we already treat bone to make it into gelatin, and I am wondering if something similar can be done for grass.


texts: Car Parinello advantages and disadvantages

texts:
A look at wikipedia and some online sources state that Car Parinello is less computationally demanding than self consistent methods. The original journal "Unified approach for Molecular Dynamics and Density Functional Theory" by Car and Parinello state that their method is appropriate for

  (i)
  compute
  ground-state
  electronic
  properties
  of
  large
  and/or
  disordered
  systems
  at
  the
  level
  of
  state-of-the-art
  electronic
  structure
  calculations;
  (ii)
  perform
  ab
  initio
  MD
  simulations
  where
  the
  only
  assumptions
  are
  the
  validity
  of
  classical
  mechanics
  to
  describe
  ionic
  motion
  and
  the
  Born-
  Oppenheimer
  (BO)
  approximation
  to
  separate
  nuclear
  and
  electronic
  coordinates.

Both of these advantages arise from the fact that the Car Parinello method is computationally less demanding However, I would like to know about its disadvantages. There must be a reason why self consistent methods are still widely used. I would also like to know if there are more advantages than it being computationally less demanding.


texts: What is the molecular formula of the nitrate of a metal Q that forms a carbonate of the form QCO3?

texts:
A metal $\ce{Q}$ forms a carbonate and a nitrate. The molecular formula of the carbonate of $\ce{Q}$ is $\ce{QCO3}$.  What is the molecular formula of the nitrate of $\ce{Q}$?

The answer says it is $\ce{Q(NO2)3}$ which I think is incorrect; I think the answer should be $\ce{Q(NO3)2}$. Am I right?


texts: What happens if I draw too much current from a home made battery?

texts:
If I try to make a battery like one of these: https://www.wikihow.com/Make-a-Homemade-Battery And then I short the two terminals, what will happen?

Disregarding anything getting hot and burning up, I'm curious what happens to the chemical reaction. I assume there is a max speed at which the reaction can occur because it seems unlikely that shorting the wires would give "infinite" current and use up the reaction in an instant.

My assumption is that the current will max out and the voltage will drop to basically nothing. Is this true? And if so what is actually limiting the rate of the reaction? Is this the same chemical mechanism as a store bought battery or are they different somehow?


texts: Why is this molecule named 1,1-chloroiodoethane, rather than 1-chloro-1-iodoethane?

texts:
$\ce{CH3CHClI}$

If there is more than one substituent on a carbon, shouldn't they be named separately like 1-chloro-1-iodoethane?


texts: Why is there a difference between O2 and B2 sigma 2p molecular orbitals in diagrams?

texts: The molecular orbital diagram for $\ce{O2}$ says that the  sigma 2p bonding molecular orbital is lower in energy than the pi 2p bonding molecular orbital. Why is this not the case in the $\ce{B2}$ MO diagram?


texts: Reaction of acyl chloride with excess Grignard reagent

texts:
I have a reaction to which I must find the majority organic product.

I think I found the correct product but the fact that the reaction takes two moles of propylmagnesiumbromide confuses me a bit. I added an image of the product I think would be the result.

I would like to know if I found the right product, and if the two moles of propylmagnesiumbromide means that there is a second part to this reaction.


texts: Does the wavelength of light absorbed by a complex depend upon extent of splitting or stability?

texts:
Background: we were doing Crystal Field Theory in school when this question popped up. Specifically we were talking about stability obtained due to the chelate effect and if the extra stability in a complex would affect the wavelength of light it absorbed.

The exact question is:

  Arrange in decreasing order of wavelength of light absorbed:
  $\ce{[Fe(ox)3]}$, $\ce{[Fe(CN)6]^{3-}}$ and $\ce{[Fe(H2O)6]^{3+}}$

If we considered wavelength depending on stability, the answer differed than if we consider splitting only.


texts: Effect of Temperature on Chemical Reaction Equilibrium

texts:
here is the question (part I):

For part (i), I need some assistance, I cannot figure out how to do the question. I know eventually what to do, it's just working out the equilibrium constants I'm having trouble with. So to start, I want to work out the K values at $\pu{600K}$ and $\pu{800K}$; I do this by considering the total pressure:

$$
\text{Total Pressure} = 1 \text{ bar}
$$

Initially:

$$
P_\ce{O2} + P_\ce{HCl} = \pu{1bar}
$$
Since there are $4$ moles of $\ce{HCl}$ per $\ce{O2}$ we can write:

$$
5P_\ce{O2} = \pu{1bar}  \to P_{\ce{O2}} = \pu{0.2bar}
$$

$85\%$ conversion means that in the end, $85\%$ of the oxygen has reacted; therefore, there is $\pu{0.2bar}*0.15 = \pu{0.03bar}$ oxygen remaining, therefore $\pu{0.12bar}~\ce{HCl}$ remaining. In addition to this, each mole of oxygen reacted results in $4$ new moles being created, and therefore there are $(0.85*0.2*2)\,\mathrm{bar}$ of water (and also chlorine) produced. With this information, I can calculate my equilibrium constant, right?


texts: I'm trying to do a reaction with phenyl piperazine, triphosgene, and 4-bromophenol. However, every time I do this reaction I seem to get the carbonyl di-4-phenylpiperazine as a major product (based on the LCMS masses). I tried to reduce the triphosgene step to 5min, which seemed to yield trace amounts of the intended product, but I still can't get my intended product as the major product. This should be such a simple reaction - what am I doing wrong?


texts: How to go from, Iron(II) Sulfate (anhydrous, FeSO4) to, Ferrous Sulfate Heptahydrate (FeSO4.7H2O)

texts:
In the lab I need some ferrous sulfate heptahydrate ($\ce{FeSO4.7H2O}$). We have some old anhydrous $\ce{FeSO4}$ from several years ago.

It seems that at normal humidity, $\ce{FeSO4}$ will hydrate to the heptahydrate on its own after a few days at most.

Is this correct? Can I "hydrate" my $\ce{FeSO4}$ just by leaving it out overnight?

Thank you.


texts: Why do elements transition discretely between solid, liquid and gas forms, rather than existing as a spectrum?

texts: I don't understand what makes a liquid entirely different from a gas, why wouldn't a liquid slowly become more gaseous, but instead transition completely from one form to the other?


texts: Why are aprotic solvents unable to solvate negative ions well? I know that the reason is due to the absence of very positive hydrogen atoms, but then why are they able to solvate positive ions well? Shouldn't its ability to solvate both types of ions be the same? I thought there their ability to solvate ions is related to whether they are partially positively or negatively charged, but shouldn't the extent to which they are partially positively or negatively charged be the same as it depends on the relative positions of the electrons?


texts: Why is calcium fluoride insoluble in water? $\ce{NaCl}$ is soluble, but $\ce{CaF2}$ is not. Why is this?


texts:
Get the temperature of the isotherm for water for which the local minimum is at $\pu{100 Pa}.$ Use the values of $a$ and $b$ of water.

My approach

In the van der Waals equation, set

$$\frac{\mathrm dP}{\mathrm dV} = 0$$

and get the value of $T.$ Plug this value in the initial van der Waals equation and and solve for $V$ from the biquadratic.
The calculations get very messy and the values come out to be unrealistic. (For example, temperature of the order of $10^6$)

My doubt is whether the $\pu{100 Pa}$ as provided by the problem setter a realistic value?


texts: At what position in the distillation apparatus does the temperature match the boiling point of the distilled substance?

texts:
A student is separating $\ce{CHCl3}$ (bp = $\pu{61 ^{\circ}C}$) from $\ce{CHCl2CHCl2}$ (bp = $\pu{146 ^{\circ}C}$) by distillation. She has just begun to collect the first distillate in the receiving flask. At what position in the apparatus will the temperature be $\pu{61 ^{\circ}C}$?

The answer to this questions is B.
I narrowed down the options to either A or B, because I know that the temperature at A would be slightly higher than $\pu{61 ^{\circ}C}$, but lower than $\pu{146 ^{\circ}C}$, and the temperature at B would be slightly cooler than the temperature at A. C and D would be much lower in comparison.
What makes the answer to this questions B rather than A? I think that the two temperatures should be somewhat close to each other, but is there some intricacy to this that I am missing?


texts: What is the effect of temperature during cryotrapping?

texts:
I'm working on a lab report that has some specific questions that need to be included. The lab work itself dealt with GC–MS.
What is the effect of the temperature selected during cryofocusing/cryotrapping? What is the effect of making this temperature warmer or colder?
My understanding was that the gas based samples would adsorb to the sample loop and then rapidly desorb when the temperature is increased. However, I am not sure what the effect of changing the cold temperature is.


texts: How do you calculate a unit cell's dimensions from an XRD spectra?

texts:
My inorganic lab had us do an XRD measurement, but I've never been explained how to interpret the data.

Question:

  Calculate the unit cell dimensions $a$, $b$, and $c$, for $\ce{YBa2Cu3O7}$ from the indexed X-ray powder pattern provided in [the textbook]. Explain why the crystals are nearly tetragonal in terms of the atomic structure of the compound. The following formula is useful:

  $$\sin^2{\theta} = \frac{\lambda^2}{4}\left(\frac{h^2}{a^2}+\frac{k^2}{b^2}+\frac{l^2}{c^2}\right)$$
  The three numbers, $hkl$, called Miller indices, indicate the direction of the scattering plane. The Miller indices can be read from the diffractogram provided. For simple reflections of the type $h00$, $0k0$, and $00l$, the value of $h$, $k$, or $l$ corresponds to n in Bragg's law.

Bragg's law:

$$n\lambda = 2d\sin{\theta}$$

The spectrum:

  (This is a scan from my textbook, while working on it I circled some items. Just ignore that.)

My Attempt:

$$\lambda = 0.154~\mathrm{nm}$$

Scouring the internet I found the formula for tetragonal atomic structure: the axes $a = b \neq c$, and the axis angles $\alpha = \beta = \gamma = 90^\circ$.

Solving for $c$:
$$\begin{align}
\sin^2{(22.9^\circ)} &= \frac{\lambda^2}{4} \left(\frac{h^2}{a^2}+\frac{k^2}{b^2}+\frac{l^2}{c^2}\right) \\
&=\frac{0.154^2}{4} \left(\frac{0^2}{a^2}+\frac{0^2}{b^2}+\frac{3^2}{c^2}\right) \\
0.151 &= 0.0237\left(\frac{3^2}{c^2}\right) \\
c &= 1.188
\end{align}$$

For $a$ and $b$:

$$\begin{align}
\sin^2{(22.9^\circ)} &= \frac{\lambda^2}{4} \left(\frac{h^2}{a^2} + \frac{k^2}{b^2} + \frac{l^2}{c^2}\right) \\
&= \frac{0.154^2}{4} \left(\frac{1^2}{a^2} + \frac{0^2}{b^2} + \frac{0^2}{c^2} \right) \\
0.151 &= 0.0237 \left(\frac{1^2}{a^2}\right) \\
a &= 0.156
\end{align}$$

Is this the right approach? If I have the right answer, what should the units be?


texts: Grease & Thermal resistant cardboard for the foods industry?

texts:
I am on the lookout for, preferably, a cardboard (ish), that is both heat & grease resistant, for usage in microwave popcorn. As such, the material must be appropriate for direct contact with food.

The idea is that a tray is placed on the bottom of a box, that will shield the body from any grease that will go liquid when heated (microwaved). Obviously, the most widely available material, and the cheaper the better is the quest that I have undertaken, and I hope that you folks can point me in the right direction, as I can't quite afford professional help for this project, as it stands.


texts: Are secondary alcohols more easily oxidised as compared to phenol?

texts:
Which among the following compounds is oxidised most easily?

  2-propanol ($\ce{CH3CHOHCH3}$)
  phenol ($\ce{PhOH}$)
  ethoxyethane ($\ce{Et-O-Et}$)
  1-methyl cyclohexanol

The answer given in my workbook is option 1. It's obvious to me that options 3 and 4 can't be the right answer (ether, hindrance). But I am confused between options 1 and 2.

I have arguments that can support either of the 2 options. There's less hindrance on phenol so formation of an intermediate ester like chromate ester would be easier their as compared to secondary alcohol. However, phenol is losing aromaticity as well, therefore activation energy of oxidation should be higher as compared to secondary alcohol.

Since $E_\mathrm{a}$ matters more, we would say that secondary alcohol is oxidised more easily, is it?


texts:
I am programming a small model to simulate diffusion of $\ce{H+}$ ions in human tissue. It's quite a simplistic model based on a naive algorithm, and I'm mostly doing it to familiarize with the concept of agent-based models.

My space is an $n\times n$ grid where each position $(x;y)$ hosts $h$ $\ce{H+}$ ions.

I understand that $\ce{pH}$ can be calculated based on $h$ as $-\log(h)$. As I want my initial $\ce{pH}$ to be stable at average human $\ce{pH}$, I'd set $h$ across the matrix to be $10^{7.5}$. (In fact, as I don't want to simulate $10^{7.5}$ protons I decided each particle will represent a bulk of $10^5$ protons and made my equation $-\log(10^5\cdot h)$. )

However, I do not understand the equation, wouldn't it at some point yield a negative $\ce{pH}$ as $-\log(x) < 0$ for $x > 1$?


texts: Is it possible to do Cobalt catalyzed directing group asisted meta C-H functionalization of arenes

texts:
Directing Group assisted Pd catalyzed (sp2)meta-C-H functionalization has a growing attention in recent years.
In addition, few examples can be found for meta-C-H functionalization via Rhodium. I am wondering whether it is possible to do meta-C-H functionalization using Cobalt as its a first-row transtion metal. Since Cobalt chemistry is somewhat different what sort challenges we are going to face? If someone could share any reported articles based on this chemistry, it is much appreciated.


texts: I would like to know how to locate conical intersection using a GAMESS calculation. I really appreciate an example alone with this since I am a novice I do not have a clear idea among bunch of examples on internet given. Also I want to know the parameters as well especially for the $DATA part in GAMESS.


texts: Haworth structures of sucrose and lactose

texts:
The haworth structures of lactose and sucrose  is

My question is regarding the glyosidic linkage, in lactose it is represented as a zig zag and in sucrose it is a "V". What does that mean. Also, in sucrose why is the the glyosidic linkage displaced down w.r.t the compound


texts: How does water evaporate completely when at room temperature?

texts: If water evaporates at room temperature because a small percentage of the molecules have enough energy to escape into the air, then why does a kitchen counter with a small amount of water eventually evaporate completely when at room temperature?


texts: Is chlorophenylmethane the correct IUPAC name rather than chloromethylbenzene?

texts: I thought that the correct IUPAC name for the molecule below (benzyl chloride) would be chloromethylbenzene because the ring always gets priority over the chain unless a primary functional group is present. However, it seems the correct name is chlorophenylmethane. Can someone explain why that is?


texts: How to calculate concentrations when dissolving two salts?

texts:
Some solid silver bromate was dissolved together with solid silver acetate what would be the highest achievable pH?
  \begin{align}
K_\mathrm{sp}(\ce{AgBrO3}) &= 5.38 \times 10^{-5}\\
K_\mathrm{sp}(\ce{AgCH3COO}) &= 1.94 \times 10^{-3}\\
\mathrm{p}K_\mathrm{a}(\ce{CH3COOH}) &= 4.76
\end{align}

Now I know this is just a question about the common ion effect. I know how to do the question if silver ions are already present in the solution then silver acetate is added. Also given the concentration of acetate ions, I can easily calculate the pH.

The real problem with this question is that you are dissolving 2 salts which are both in equilibrium. I don't know how to calculate the concentration of acetate ions in this scenario.

This is what I did:

$$5.38 \times 10^{-5} = [\ce{Ag+}][\ce{BrO3-}] = x^2$$
$$x = \ce{[Ag+]} = 7.33 \times 10^{-3}$$
$$1.94 \times 10^{-3} = [\ce{Ag+}][\ce{CH3COO}] = (7.33 \times 10^{-3} + y)(y)$$
I then used quadratic formula to find y.

I am pretty sure that this method is wrong because wouldn't the dissolution of silver acetate cause the equilibrium of silver bromate to shift backwards, causing the value of x to decrease. Or can we assume that this shift is negligible.

Also, by highest achievable pH doesn't that imply that the final pH of solution is variable. However, shouldn't it have the same pH every single time, making the words highest achievable pH redundant? Or am I missing something?


texts: Changing the level of theory for organometallic compounds

texts:
I'm finishing my Ph.D. in Inorganic Chemistry and having a debate with my supervisor. The work in question have two organometallic compounds A and B. The structures are based on X-Ray Diffraction, so I already have a good molecular frame and just need to optimize the hydrogens. For that I'm using PBEh-3c that usually work well for organometallics.
In the next steps, using the now pre-optimized structure, I have changed the level of theory for each task, selecting the (supposedly) best level for each, based on benchmarks:

Broken-symmetry (magnetic coupling): TPSS/Def2-TZVP
Bond Orders and spin distribution: SCS-MP2/Def2-TZVP
Energy Decomposition: DLPNO-CCSD(T)/Def2-TZVP
TDDFT: wB2PLYP/Def2-TZVP

My Supervisor is not comfortable with the mix of levels of theory, but I believe that it is OK if I'm sure that I have the correct ground-state geometry and I'm not comparing the same property for A and B with different methods (for example TDDFT using PBE for compound A and wB2PLYP for compound B).
So, the question is: is it OK to change the level of theory of my calculations to select the best setup for the property I'm trying to calculate if I know that I have a good ground-state geometry and that my calculation is not displacing the geometry?


texts: Is xenon electropositive in compounds of xenon?

texts:
Do you agree with the below passage in my text?

Electronegativity is defined as the ability for something in a covalent framework to attract electrons also in covalent bonds.

Electropositivity is the inverse of electronegativity or the ability of something to donate/release electrons in a covalent framework.

How can a highly oxidized element be very electropositive? A highly oxidized element by definition has a minimal amount of electrons to be donated.


texts: Can I add a 4 L bottle of methanol solution with 0.1% formic acid into a drum containing non-halogenated waste?


texts: Rate of change of reaction rate of 0th, 1st, 2nd order reaction?

texts: Does the rate of change of the reaction rate for a 1st order reaction change linearly over time? My teacher says it does, but my textbook seems to contradict this. Could anyone clarify?


texts: Mechanism for the reaction between trisilylamine and hydrogen chloride

texts:
In Concise Inorganic Chemistry by J. D. Lee (adapted by Sudarsan Guha), in the chapter "Chemical Bonding", under the topic "Back Bonding with Nitrogen as a donor atom" the following reaction is given:

  $\ce{(SiH3)3N +4HCl \to NH4Cl + 3SiH3Cl}$ (bond cleavage through $\mathrm{S_N2}$ mechanism)

I have learnt about $\mathrm{S_N2}$ in organic chemistry. I know its mechanism there and tried to do the same here (there is no reaction mechanism given for this in my book).

As suggested by this comment, $\ce{(SiH3)3N}$ is still basic so the following set of reactions takes place:

$$\ce{\color{orange}{(SiH3)3N} + \color{blue}{HCl} \to (SiH3)3NH+ +Cl-}\tag{Protonation}$$
$$\ce{(SiH3)3NH+ +Cl- \to (SiH3)2NH + \color{red}{SiH3Cl}}\tag{Nucleophilic Attack}$$
$$\ce{(SiH3)2NH + \color{blue}{HCl} \to (SiH3)2NH2+ + Cl-}\tag{Protonation}$$
$$\ce{(SiH3)2NH2+ +Cl- \to (SiH3)NH2 + \color{red}{SiH3Cl}}\tag{Nucleophilic Attack}$$
$$\ce{(SiH3)NH2 + \color{blue}{HCl} \to (SiH3)NH3+ + Cl-}\tag{Protonation}$$
$$\ce{(SiH3)NH3+ + Cl- \to NH3 + \color{red}{SiH3Cl}}\tag{Nucleophilic Attack}$$
$$\ce{NH3 + \color{blue}{HCl} \to \color{green}{NH4+Cl-}}\tag{Protonation}$$

Summing up all the above reactions we get the overall reaction as follows:

$$\ce{\color{orange}{(SiH3)3N} + 4\color{blue}{HCl} \to \color{green}{NH4+Cl-} + 3\color{red}{SiH3Cl} }$$

I got the mechanism I was looking for! But the main problem is the first step - protonation. In my book, it's given that in $\ce{(SiH3)3N}$, due to the presence of back bonding, the lone pair on nitrogen atom is not available for donation. Or in other words, $\ce{(SiH3)3N}$ cannot act as a lewis base (electron-pair donor). Thus the first step of protonation (acid-base reaction) is ruled out.

So, how does the above reaction take place? Do we have any other reaction mechanism for the above reaction? If yes, could you please specify the mechanism? Or is the above one is itself correct?

I am unable to find relevant information regarding this on the internet.


texts: How are pencil marks "adhered" to the paper?

texts:
Pencils create marks by physical abrasion, leaving behind a trail of solid core material that adheres to a sheet of paper or other surface. Wikipedia

Normal paper is mainly composed of cellulose fibers, which were "funded" by the plants. And this "solid core material" is supposedly composed of graphite and a type of binder clay.

Image source

"Adhering" is usually caused by intermolecular forces. (e.g.: when sugar adheres to wet surfaces because of Hydrogen bonding). The questions are:

Is the case of a pencil mark some kind of intermolecular force too?
If so, what is it?


texts:
I have always believed that it is impossible for the atoms of period 2 elements (when they are the central atoms in polyatomic ions/molecules) to accommodate more than 8 electrons in their valence shell. This is because of their small atomic size, which results in a significantly higher electron density being borne by the central atom and thus, instability can easily arise if too many electrons are held by it. Having seen many posts on this forum on the concept of hypervalency, I understand that many seemingly "hypervalent" molecules (e.g., $\ce {PCl5}$, $\ce {SF6}$, $\ce {ClO4^{-}}$) do not really have their central atoms possessing more than 8 electrons in their valence shells. This is due to the electron-withdrawing effect of the electronegative atoms that are bonded to the central atom, often resulting in there being less than 8 electrons populating the valence shell of these central atoms (Gillespie and Silvi, 2002).
However, my belief has recently been challenged by the existence of the orthonitrate ion, in which the $\ce {N}$ atom is claimed to possess $\ce {8.65}$ electrons in the valence shell (as written in the "Alternative definition" section of this article). This seems rather nonsensical to me as the $\ce {O}$ atoms surrounding it are more electronegative than the central $\ce {N}$. I would like to request for a verification of the claim regarding $\ce {N}$ possessing more than 8 electrons in the valence shell. Additionally, I would also like to ask if the ionically-bonded structure with one $\ce {N^+}$ and four $\ce {O^-}$ is an accurate representation of the bonding in the ion.
Reference
Ronald J. Gillespie, Bernard Silvi, "The octet rule and hypervalence: two misunderstood concepts," Coordination Chemistry Reviews 2002, 233-234, 53-62 (https://doi.org/10.1016/S0010-8545(02)00102-9).


texts: Entropy change in mixing a gas at constant temperature and pressure

texts:
The expression given on Wikipedia is (https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwj-_pDA2IfSAhUFto8KHa2kBAwQygQIIDAA&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FEntropy_of_mixing%23Mixing_of_ideal_materials_at_constant_temperature_and_pressure&usg=AFQjCNFVf8mAoquhiL05HeVXC1H3cw54xA)
But If I evaluate it as following I get a different answer .
$$\Delta S=\int q_{rev}/T=\int pdV/T $$
as p and T are constants $$p(V_1+V_2)/T $$
What is wrong with my method ?


texts: Since aqueous acids release Hydrogen cations into the solution, will an electric current create Hydrogen gas?

texts: I was wondering that since acids dissociate in water to make a lot of  $\ce{H+}$ cations. Is it possible that introducing a supply of electrons via an electric current, would create $\ce{H2}$ gas?


texts: How to check whether intramolecular hydrogen bonding takes place in cyclic compounds?

texts: How can we confirm or have a clear idea whether hydrogen bonding is taking place in substituents of cyclic compounds? For example, it takes place in ortho-nitrophenol, but it doesn't take place in ortho-flurophenol despite the fact that the nitro group and the fluorine are present at the same position and both are highly electronegative.


texts:
I came across a question where we have to find out the stability of species that are in chair conformations. The species are as follows:

Comparing the 'A' values tells me that compound I, III and VI should be most stable, but the answer given is: I,IV and V.
Can anybody tell me where did I go wrong?


texts: Synthesis of Aspirin, made unknown fluid

texts:
When I tried synthesising aspirin, after quenching and cooling it I noticed a translucent, milky, white fluid floating in the solution.

The method used was:

Salicylic acid (2 ml) was added to acetic anhydride (2 ml) in a flask with 8 drops of concentrated sulfuric acid.
Warmed the solution in a water bath until all solid was dissolved.
Added 5 ml of cold water to the solution to quench.
Placed solution in water bath to dissolve the solids again. (I noticed that not all the solid dissolved)
Added 10 ml of water to solution and placed in an ice bath (This was when I noticed the fluid forming)

When the solution was filtered only that fluid remained as the residue. Another person also had the same problem but said they got rid of the fluid by scratching the side of the flask with a stirring rod after taking it out of the ice bath. Could someone please explain what it is?


texts:
Researching the coloration of transition metal complexes one day, I came across this reference on Wikipedia 1:

I am not sure why this is so. Take $\ce{Mo(CO)_6}$, or any other carbonyl complex of the metals in group 6. If we have a strong $\pi$ acceptor like carbonyl, and hence a low-spin $d^6$ system, would we not get an orbital splitting pattern like this:

The excitation of an electron to one of the empty $e_g$ orbitals seems feasible to me. Why can't one of those paired electrons absorb radiation to exhibit colour for the complex?

Reference

1 https://en.wikipedia.org/wiki/Metal_carbonyl


texts: Which units do I use in calculating heat capacity?

texts:
The specific heat capacity of liquid water is $4.18 \, \text{J} \, \text{K}^{-1} \, \text{g}^{-1}$. Calculate the energy required to heat $1.0 \, \text{mol}$ of water from $298 \, \text{K}$ to $363 \, \text{K}$.
My question is: Do I have to change the moles of water into grams or should I sub in $1.0$ into the formula for specific heat capacity?


texts:
The pentahydrate salt of copper (II) sulfate exists as a blue solid while the anhydrous and monohydrate salts appear as white solids. The structures of these salts are discussed here. The blue colour of the copper (II) sulfate pentahydrate salt arises due to a similar reason why $\ce {Cu^2+}$ in aqueous solution is blue in colour. Based on Crystal Field Theory, this is due to the phenomena of d orbital splitting in the octahedral complex. As discussed in the post linked, in the pentahydrate salt, the $\ce {Cu^2+}$ ion is octahedrally coordinated, with 4 $\ce {H2O}$ molecules forming dative covalent bonds with it while the other two sites are occupied by the oxygen atoms of the sulfate ion. This leads me to wonder if the sulfate ions contribute to any significant degree of splitting of the d orbitals of the $\ce {Cu^2+}$ ion. As the colour of the anhydrous $\ce {CuSO4}$ salt is white, we can infer that the sulfate ions do not contribute to the d orbital splitting. Consequently, we can infer that the sulfate ions do not really form dative covalent bonds with the $\ce {Cu^2+}$ ion.

But why would this be the case? In the sulfate ion, there is rather poor delocalisation of the lone pair due to long $\ce {S-O}$ bond lengths and thus, ineffective p orbital overlap between the p orbitals of the sulfur and oxygen atoms. Hence, the negative charges, as well as the lone pairs of electrons, are rather localised on the oxygen atoms. This analysis all points to the conclusion that the sulfate ion should be able to act as a ligand.

Similarly, the fact that anhydrous, neutral $\ce {CuCO3}$ exists as a gray solid, suggests that the $\ce {Cu^2+}$ ion does not have dative covalent bonds with the carbonate ion , i.e. $\ce {CO3^2-}$ does not act as a ligand. Although for the carbonate ion, due to the stronger delocalisation of electrons within the ion, it may be more convincing to say that it may not be able to act as a ligand effectively.


texts: What is the meaning of the "dot" notation in chemical formulas?

texts: For example for 4 given elements A,B,C,D, what's the meaning of $\text{AB} \cdot x \text{CD}$?


texts: How to remove salt from powdered soup mix?

texts:
Sometimes I carry powdered soup mix (Knorr/Maggi) when I travel but they are way too salty. Is there an efficient and simple chemical process to lower the salt content?

I know sodium is super soluble and is hard to remove by precipitation, but is there a work around to perhaps only dissolving the salt and take them out? Thanks!


texts: why does milk of magnesia have an expiration date?

texts:
I noticed an old bottle of milk of magnesia in my refrigerator and saw that it had an expiration date printed: January 2015.  Checking the ingredients, I saw only three: magnesium hydroxide, purified water, sodium hypochlorite.  I understand that milk of magnesia is more or less a mineral solution.  How could this require an expiration date?  What would be the consequences of taking milk of magnesia past the expiration date?

(I see that this page discusses expiry dates on chemicals in the abstract; I don't know which of these arguments apply to milk of magnesia in particular, or any other over-the-counter dietary supplement or drug.  As an IT professional, I have absolutely no experience or expertise in the physical or life sciences.)


texts:
A liter of a solution contains $\pu{0.120 mol}$ of $\ce{C6H5COOH}$ $(K_a = 6.5
×10^{-5})$ and $\pu{0.105 mol}$ of $\ce{C6H5COONa}$. I'm asked to calculate the pH of the solution after adding $\pu{100 mL}$ of a $\pu{1.20 M}$ $\ce{NaOH}$ solution, the pH of the initial solution is $4.13$.
Here's what I've done. Since $\ce{NaOH}$ is a strong base it will disassociate completely, so we will end up with $0.120$ moles of $\ce{OH^{-}}$. Calulating the $\ce{pOH}$ we get $0.92$ and with that we can calculate the $\ce{pH}$ which will be $13.07$. Is that the correct way of doing it ?


texts: Can we determine the amplitude of vibration of O-H bonds in water?

texts:
This is going to be a long shot, and I might be wrong in any and all of my assumptions, be warned (... and please correct me). I might also be trivially right, I have no idea.

At equilibrium, each degree of freedom has the kinetic energy:

$$E = \frac{1}{2}k_\mathrm{B}T$$

So, I have water at, say, $300\ \mathrm K$. Water has three atoms, so 9 degrees of freedom (3 per atom, because space is three-dimensional). One of them is for a $\ce{O-H}$ stretching. I know that usually, you would need to divide into modes of oscillations, but let's say we combine half the energy of the symmetric and antisymmetric stretchings, giving that one $\ce{O-H}$ stretching has a full $\frac{1}{2}k_\mathrm{B}T$ in it. So we have an average, roll of drums,

$$ E = \frac{1}{2}(1.3806488 \times 10^{-23})(300) =  2.071\times 10^{-21}\ \mathrm J$$

in a $\ce{O-H}$ stretching.

NOW, let's say this stretching behaves like an harmonic oscillator, its' energy is given by the amplitude of oscillation:

$$ E = \frac{1}{2}kA^2 $$

where $k$ is the stiffness constant of the chemical bond.

That's nice, but we have two unknowns, $k$ and $A$. So let's go further. If we know the absorption band's wavenumber, we can say that the amplitude corresponds to this wavelength, $2.734\ \mathrm{\mu m}$ (source = Wikipedia). This would mean that we have a stiffness constant:

$$ k = 5.5412 \times 10^{-10}\ \mathrm{N/m}$$

I know that, although it was fun to blindly math around, this result is wrong. Just the fact that the stiffness constant would depend on temperature doesn't sound right. Neither does the bit about wavelength = amplitude.

My question is: is it possible to know the amplitude of oscillation/stiffness constant of a $\ce{O-H}$ bond?


texts: How much energy is required to operate a Sabatier Reactor?

texts:
I'm trying to model some industrial processes and having a hard time finding information about the Sabatier reaction. The sabatier reaction combines CO2 (and possibly CO) with H2 to produce H2O and CH4.
On the one hand this reaction is exothermic. On the other hand it requires high heat and pressure. Does the reactor need initial heating and pressurizing of the gases, and then is it self-sustaining (or rather requiring cooling)?
What is clear is that some energy is be needed to compress gases and flow them over the catalysts.
Are there any estimates of how much energy a reactor would use? I understand that scale would also be an important parameter, but any preliminary estimates are useful to me.


texts: USNCO Question - Determining solute using spectrophotometer

texts:
Below is a question from the 2017 USNCO:

The concentration of which approximately 0.01M solution could be most accurately determined by a visible spectrophotometer (or colorimeter)?

(A) $\ce{Mn(NO3)2}$

(B) $\ce{Co(NO3)2}$

(C) $\ce{Zn(NO3)2}$

(D) $\ce{Pb(NO3)2}$

The answer sheet states B is the correct answer.

I researched the colours of the ions in solution, and found:

Mn is pink
Co is pink
Zn is clear
Pb is clear

I was unsure how to progress from there.

How should I approach this question in an exam if there was no reference book?


texts: How can I determine if there are π-π interactions between an amide and an aromatic ring in a protein?

texts:
In a crystal structure I've determined, a triazole ring on my ligand appears to be stacking with a tyrosine (top in picture):

However, there is also an amide, courtesy a glutamine, near it (bottom).  Is it likely this terminal amide is engaging in π-π interactions with the triazole or just weaker dispersion forces?  How would I quantify how significant the interaction is?


texts: Which is more basic, piperidine or pyrrolidine and why?

texts: Pyrrolidine seems to be less basic as it is a 5-member ring and +charge on N atom won't be stable due to steric factors as compared to piperidine but the results are opposite.


texts: Circular dichroism of a hydrazone boron complex

texts:
Last year, I came across a quite puzzling article, in which the authors claim to have found a photophysical explanation for aggregation induced emission (doi:10.1038/nchem.2612). The model proposed implied that the lowest-lying excited state ($\ce{S1}$) was a non-emissive ("dark") state, whereas $\ce{S2}$ (or $\ce{S3}$) was emissive, and depending on the solvent, the molecule could be more or less emissive.

They claim to prove their model by observing the "dark state", and among other concerns, one point that particularly retained my attention was that one of their proofs was a CD spectrum (supporting information page 43) of this molecule:

Now, simply put, I don't understand anything about how it is possible. To precise my trouble, this can be broken into different subquestions (please feel free to answer partially if you wish).

I see strictly no reason why this molecule should show such a CD spectrum in solution (77K in Glycerol/Ethylene glycol (8:2 v/v)). Even if it is chiral, it should be a racemate. Why does this molecule show CD?
The maximum of the band is 150 mdeg. Why is it so high?
Absorption and CD spectra are not completely superimposable. The authors claim that this demonstrates that the band they are looking at consists of two different electronic transitions (hence proving the existence of the "dark state"). I don't find this statement straightforward (especially judging by the signal shape). If you have references which elaborate on this aspect, or other references using this same argument, I would be very pleased to read them.

Am I missing something very important concerning chirality, or CD spectroscopy?


texts: What is the effect of rolling a graphene sheet into a carbon nanotube on the lattice constant and the geometry of the graphene?


texts:
$$\ce{CO2(g) + Ca^2+(aq) + H2O(aq) <=> CaCO3(s) + 2H^+(aq)}$$
Find the equilibrium constant using a free energy table.

Finding the free energy and plugging it into the equation $\mathrm{G = -RT \ln (\mathit{K})}$ is easy, but I am confused about what $K$ it is. Is it $K_c$ or $K_p$, or does it even matter?
This is important because I am supposed to do equilibrium calculations with it later. I guess I have to use $K_c$, because only the concentrations of the aqueous solutions are given, plus $\ce{CO2}$ is in ppm. I think $\mathrm{G = -RT \ln(\mathit{K})}$ gives me $K_p$, so do I have to convert that into $K_c$ afterwards if I want to do equilibrium calculations?


texts: What is the mechanism of oxidation of phenol to benzoquinone?

texts:
I looked up the mechanism in a lot of organic chemistry books, including Clayden, Klein, Solomons, McMurry but I couldn't find the mechanism of oxidation of a phenol. I also looked it up in pharmacognosy books, but with no luck. All I could find in these books is the following scheme, with no mechanism:

It seems like other oxidizing agents can be used, such as hydrogen peroxide and silver oxide.

Unlike primary and secondary alcohols, phenol doesn't have an hydrogen atom attached to the carbon directly bound to oxygen. My guess is that the double bond of phenol will react with the oxidizing agent, but not sure of how this will work.


texts: Optical rotation in inversion of sucrose

texts:
In reading about the inversion of sucrose I came across the equation for the reaction rate constant below:

$$k = \left(\frac{2.303}{t}\right) \log\left[\frac{\alpha(0) - \alpha(\infty)}{\alpha(t) - \alpha(0)}\right] \tag{5}$$

What is the logic for difference of the rotations' sign for the logarithmic term? i.e conceptuatlly why is $\alpha(0)$ the minuend in the numerator and the subtrahend in the denominator?

I have seen other quantities like volume or pressure represented in this form but I don't understand the reason why reacting sugar would be presented this way.


texts: Work to overcome adhesion of a liquid to a solid

texts:
I'm interested in the van Der Waals force of a liquid adhered to a solid. For example, if you spray some water on a vertical piece of glass, the little droplets with adhere to the window rather than be pulled down by gravity.

How does one calculate the energy of that bond, or re-stated for my specific interest, the work required to de-adhere the liquid?

I haven't been able to find any good resources for macroscale liquid films on solid surfaces. My first guess was surface tension of the liquid multiplied by the interface area; the units work out and it makes some intuitive sense, but I don't like that its independent of the solid material.


texts: Why does a photon have linear momentum, although it doesn't possess mass?

texts:
We know that photon doesn't possess mass. But it has a tendency of colliding with surfaces, as we see in the photoelectric effect. As it doesn't possess mass, then how does it have linear momentum?

$E=mc^2$ and $E=hc/\lambda$

$mc = h/\lambda =p$

Here $m=0 \Rightarrow p=0$.
But photons can collide.


texts: Can the green spots in these coins be copper chloride?

texts:
My father collects coins as a hobby and lately has observed some green spots in some of his coins so he told me to ask here to see if anyone knows what it is.

The coins are made of silver (999 parts out of 1000 according to the description) so at first he thought that it might be some silver oxide but the silver oxide is dark brown and not green.

He looked it up in the Internet and he has read that it might be copper chloride but it doesn't seem right to him due to the purity of coin.

Is this feasible? Can the spots be copper chloride? If not, what can they be?


texts: Why is methoxy group an electron donating group?

texts: I am studying acidity of carboxylic acids and I found that benzoic Acid is more acidic than p-methoxybenzoic acid. It is written in my book that this happens because methoxy group is an electron donating group. I can understand why electron donating groups can reduce acidity of an carboxylic acid but I can't understand why methoxy group acts as an electron donating group?


texts:
I recently came across a question about the stability of radicals and this option was given as correct.

$\ce {F2C^.H}>\ce {C^.H3}  $

And the solution was given that $\ce{FC^.H2}$ and $\ce{F2CH^.}$ are more stable than $\ce {C^.H3}$ but $\ce{C^.F3}$  is less stable. Can anyone explain why?
If it has got something to do with inductive effect then all three $\ce {F2C^.H},\ce{FC^.H2},\ce{C^.F3}$ should be less stable than $\ce {C^.H3}  $. Right?


texts: What is the mechanism for the reduction of ketone to alkanes using $\ce{H2}$, $\ce{Pd/C}$ in ethanol? Searching on Google mostly yields the reduction of ketones to secondary alcohols using LAH.


texts:
On the table published here (link) each cell has one to five numerals arranged vertically in its top right corner. The sum of those numbers is always the relative atomic mass of the element. I suspect that, in most cases, two of those numerals represent the number of protons and the number of neutrons, respectively. However, I have no idea what the other numerals represent.

What do the numerals  on the top right corner of the cells in the periodic table represent?


texts: Wade's rules applied to metallic elements

texts:
There are many examples of metallic clusters that distort from the structure predicted by Wade's rules to a more 'spherical', closo-like arrangement. For example,

$\ce{Bi8^2+}$ is a square antiprism (WR predict an arancho-derivative of a bicappped square antiprism, with 1 capping and 1 adjacent to an open-face atoms removed, instead of 2 capping atoms)
$\ce{Bi9^5+}$ is a tricapped prism (WR predict a capped antiprism)
$\ce{Ge8R6}$ is a square prism (WR predict an arachno-derivative of a bicapped square antiprism)
$\ce{Ge9R3^-}$ is a tricapped trigonal prism (WR predict a capped square antiprism, i.e. expect nido but get closo)

My lecture notes (not available online) say that

  Wade's rules are much less effective at predicting structures of metallic elements because intact polyhedra (spherical arrangements of metal atoms) tend to be a lot more stable for the more metallic elements, as compared to boron.

Could someone please explain why intact polyhedra are more stable for these elements.


texts: Finding equilibrium constant from standard free energy

texts:
This question is asking to calculate equilibrium constant for oxidation of glucose from thermodynamics quantities. So the first expression came to my mind was $-\Delta G^\circ=RT\ln K$. I found the value of $\Delta G^\circ=-2\,278.78$ but as I proceed I've got $\ln K=1\,161.94$ which I couldn't reach to the $K$ value. Is there any other ways to solve this question?

$$\ce{C6H12O6(s) + 6O2(g) <=> 6CO2(g) + 6H2O(l)}$$

$\Delta G^\circ_\mathrm r=-2878.78\ \mathrm{kJ}$

At equilibrium, $\Delta G=0$; $Q=K$,

$\Delta G=\Delta G^\circ+RT \ln K$

$2878.78\times10^3\ \mathrm J=\left(8.314\ \mathrm{J/(mol\ K)}\right) (298\ \mathrm K) \ln K$

$\ln K=1161.93596$

Answer from the book is $K=5\times10^{504}$


texts:
I have a pH 10 NaOH solution. I need to bring down the pH to 9. So I used the $C_1V_1 = C_2V_2$ approach.

$C_1 = \mathrm{0.0001~mol/L}$

$V1$ is the necessary amount to produce 10 L of pH9

$C_2 = \mathrm{0.00001~mol/L}$

$V_2 = \mathrm{10~L}$

\begin{align}
C_1V_1 &= C_2V_2\\
0.0001~\mathrm{mol/L}\cdot V_1 &= 0.00001~\mathrm{mol/L}\cdot 10\mathrm{L}\\
V_1 &= \frac{(0.00001)(10)}{(0.0001)}\\
V_1 &= 1\mathrm{L}\\
\end{align}

I Applied this calculation in reality and used a pH probe and got a pH of 6.5. I think the drop is too sudden in this type of titration. What should I do?


texts: How does Aloe Vera leave a cool feeling on your skin? Why does it evaporate fast?

texts:
If you have ever grown Aloe Vera and applied it to your skin, it feels a bit slimy. However, after it evaporates it has a cool feeling on your skin.

Also, why does the Aloe Vera evaporate so fast? What is it made of, apart from water that makes Aloe Vera do this?

I am assuming Hand Sanitizer and Aloe Vera are not directly connected.


texts: Why does attractive forces of nucleus increase more than shielding across groups?

texts:
When you study the electronegativity of the elements, the general trend is that it rises with increasing group number, and decreasing period.

Supposedly this is because the attractive forces of the nucleus increase quicker than the shielding effect of the electrons.

Is this shielding effect simply a repellant force, or is there another phenomenon at play?
Why does the shielding effect not increase as rapidly?
Why does the difference between the attractive forces and the shielding effect become less pronounced with increasing period?

(source: wikispaces.com)


texts: What is the correct way to illustrate a bond to something irrelevant in a structural formula?

texts:
You can probably tell I'm not really a chemist (hi from physics!), but I've suddenly found myself having to draw some structural formulae, hence the stupid question.

I've drawn a diagram of the four DNA bases:

I don't care what they're attached to, and I don't fancy drawing an entire DNA molecule, but I'd like to show where they bond to the rest of the nucleotide. I've used \cdots ($\cdots$) currently, but that doesn't feel right. I considered R, but I'm not sure if an entire DNA molecule really counts as an R group. I saw a wavy bond once, but it feels like those are confined to stereochemistry.

What's the convention in cases like this? (And what do I Google to find it next time I want to know?)


texts: For example, in glycolysis, $\ce{NAD+} $ is reduced to $\ce{NADH}$ and then it's more energetic. Why adding electrons to an atoms gives it more energy?


texts:
How is the "correct" answer not a redox reaction?

Isn't the "correct" choice a textbook example of an organic redox reaction? After all, we are breaking a C-C bond and replacing that with a C-O bond. If that's not redox I don't know what is redox.

Or am I missing something fundamental here?


texts:
One of the first thing that every one learns in organic chemistry lab is how to monitor a reaction progress with TLC.

My question is what methods do we have for visualizing TLC ( UV , Iodine vapor , etc ) and each one of them is suitable for what purpose and condition ? and is there other ways like TLC (fast , easy , relatively cheap , etc) for monitoring reactions progress?


texts:
In naming the attached compound, is there a reason it is termed:

  3,5-dibromo-1-chloro-4-ethyl-2,6- dimethylbenzene

as opposed to:

  1,3-dibromo-5-chloro-2-ethyl-4,6-dimethyl benzene?

Shouldn't bromine be assigned the smaller numbers, given that it comes first alphabetically?


texts: Why does benzene have 3 π–π* transitions in the UV range, but ethene, butadiene, and hexatriene each have only 1?

texts: Are the π and π* orbitals of benzene much closer together in energy which allows for multiple transitions? Why is this not the case for hexatriene if they both contain the same number of pi bonds?


texts: Should I provide a citation for atomic masses?

texts:
I am writing my first lab report ever, and the handbook I was given did not say anything in particular about this issue. I will use the atomic masses for my calculations and I am not sure if I should cite the source from which I obtained the data for those figures.

Should I cite periodic tables? If yes, how?


texts: Is there a plastic that's clear, acetone resistant, and ideally sold in sheet stock that's ~1/8" or 1/4" thick?  Both acrylic and polycarbonate are out, they turn cloudy on contact with acetone.  I tried a piece of PETG and it was better, but still turned fairly cloudy after a few seconds.  I don't need continuous service, but I need it to still look decent if it gets wiped down with acetone.


texts: As the title implies, what is the molecular basis of cyanide toxicity? I did some searching around at the CDC and it only states that it prevents cells from using oxygen. I also read how it could take as little as $131~\mathrm{ppm}$ to kill. How can a simple $\ce{CN-}$ ion do so much damage?


texts:
I don't know what to call it I'll just provide a link. From what I can tell it is impossible, but why?

http://www.chemicalize.org/structure/#!mol=structureId%3A1609384473364&source=calculate


texts: What are bond lengths and angles for picric acid?

texts: I am working on a project in which I am required to create a model of picric acid. I do not understand how to find the bond lengths, bond angles, shape, and atom size of this molecule. Any help in finding these measurements or in showing me how to find them would be amazing!


texts: How to prevent feasibility of intermolecular attack of 1,2-diol?

texts:
I was given a problem that requires me to synthesize (1R,2R)-2-methoxycyclohexanol from cyclohexene. I tried it with syn-hydroxylation of alkene $\pi$ bond with $\ce{OsO4}$ and NMO then directly transformed the hydroxyl group to methoxy group with $\ce{NaOH}$ and $\ce{CH3I}$.

During the protonation of one hydroxyl group, I notice that it would be attacked from the other hydroxyl group and I think it would make ring closure, which is what I do not want. Is the intermolecular attack of 1,2-diol feasible on any starting material (cyclic or polycyclic)? How to prevent the intermolecular attack to get desired product?


texts: Why does phosphorus tribromide act as a Lewis acid (electron acceptor)?

texts:
This question is purely out of curiosity and to help me remember the "why" of a mechanism to help me remember the "what/how".

In organic chemistry we recently studied the  Sn2 Substitution of Primary Alcohol with PBr3:

My question is, why is it favorable for PBr3 to act as a Lewis acid (i.e. accept electrons from the oxygen to form a bond) when it already has a full octet and no formal charge?


texts: Measuring ions through color change during electrolysis

texts:
I have very little experience in chemistry, you might consider me a physicist, and I am mostly not even sure where to find the information I need. I will start off by describing my problem, I have a nutrient solution (for plants) and I want to measure the different nutrients using electrolysis based on the color change. I have read that if a Copper anode is used the solution will turn bluish and if ammonia is present it will turn deep blue.

Now this is great and all, but I have 18 other elements/compounds I want to be able to measure and I have no idea how to figure out what materials to use for the anode/cathode to get color shifts which are dependent upon the different compounds found in the nutrient solution. How do you chemists go about finding out such things, do I simply have to test a bunch of it for myself or do you have a secret lair of wisdom somewhere?

I'm mostly asking for guidance in information seeking here, but if anyone is interested in the specific ions present in the solution they can be found on Wikipedia: https://en.wikipedia.org/wiki/Plant_nutrition


texts: What are the products of the reaction of 1-methoxycyclohexene with dilute hydrochloric acid?

texts:
When 1-methoxycyclohexene is treated with dilute aqueous hydrochloric acid, methanol is produced along with another organic product. Identify this product. Explain why methoxycyclohexane is inert under these reaction conditions.

I don't understand why it isn't just a simple addition to the double bond. I get that there's conjugation but is this what makes things different? I don't get why methanol is the leaving group and therefore I cannot predict the other product. Also, it says that methoxycyclohexane (the same molecule without the double bond) is inert under these conditions. Why does it not undergo substitution? The oxygen could surely be protonated and then methanol would be a good leaving group which would give rise to substitution (probably SN1). Why is this not the case?


texts: What does it mean to calculate hardness in terms of ppm of calcium carbonate?

texts:
PPM means per part million or milligram per litre of solution.Calculation of ppm for a given compound say $x \pu{gms}$ of $\ce{Ca(HCO_3)}$ in 1 liter of water would be done like

$$ppm= \frac{1000\cdot x}{1\pu{1L}}$$

But I do not understand by what's meant by in terms of $\ce{CaCO3}$ is it equivalents or weight? This was asked in an exam and the formula is not covered in my textbook.


texts: Probablity distribution of bend angle in gromacs

texts:
In an analysis I got the probability distribution of a bend angle $P(\theta)$ with respect to time. However, I need to plot $P(\theta)$ with respect to $1- \cos(\theta)$ where $\theta$ refers to the bend angle in B-DNA.

Is there any command or procedure employed for it in GROMACS?


texts: What is the electronic configuration of La⁺?

texts:
Second IP of La is most likely to second IP of which element:

  (1) Be
  (2) Ba
  (3) Ca
  (4) Zn

The given answer is calcium. I don't understand if the 6s electron or the 5d electron leaves on ionization. Any help is appreciated.


texts: What is a benzene ring minus a hydrogen atom called?

texts: I thought it was Phenyl but the teacher said it wasnt and that it started with "A" I cant seem to figure it out


texts: Why does ammonia have higher melting point but lower boiling point than HF?

texts: I guess the reason is hydrogen bonding, but shouldn't both the trends be similar in that case?


texts:
Inspired by this question, what is the substance or compound with the highest melting point? At standard atmospheric pressure and ever-increasing temperature which substance a) eventually becomes liquid b) does so at the highest temperature?

I don't know much about glasses or related semisolids, so perhaps a reference viscosity? Glass transition temperatures are kind of like melting points, but some materials have a glass transition temperature and a melting point.

Some initial casting about on the internet finds that rhenium and tungsten have melting points at about 3400 °C, and hafnium carbide claims to be 'one of the highest' at 4100 kelvin. Does it actually melt or just decompose and then sublimate? 4100 kelvin is its 'refractory temperature', but I'm not certain how that's defined.


texts: CO : CO₂ ratio when given amounts of carbon and oxygen react with each other

texts:
By the reaction of carbon and oxygen a mixture of $\ce{CO}$ and $\ce{CO2}$ is obtained. What is the composition of the mixture by mass obtained when 20 grams of $\ce{O2}$ reacts with 12 grams of carbon?

I wrote the equation as

$$\ce{4C + 3O2 -> 2CO + 2CO2}$$

and identified $\ce{O2}$ as the limiting reagent then the masses of $\ce{CO}$ formed will be 11.66 grams and mass of $\ce{CO2}$ formed will be 18.33 grams, which gives the ratio as 7:11, but the answer is given as 21:11.

Can somebody please tell me where am I going wrong?


texts: Why does aqeous fluorescein shine when exposed to UV light?

texts: I know that (aq) fluorescein "absorbs" UV light and releases light in the visible spectrum , but how does it do that. It is a really interesting and useful organic chemical and I just wanted to know what goes on in it so that it lights up.


texts: Why aqueous KI is used when collecting Iodine?

texts:
In room temperature solid di-iodine pentoxide($I_2O_5$) reacts with carbon monoside to form carbon dioxide & Iodine. This can be used to measure the amount of carbon monoxide in an air sample. $5dm^3$ air sample is passed through a tube containing solid $I_2O_5$. $\bbox[yellow]{Discharged \space I_2\space is \space sent\space into\space a\space container\space which\space has\space excess\space aqueous\space KI\space solution.} $ This solution is titrated with $0.005mol/dm^3$$Na_2S_2O_3$ solution( Starch indicator was used). If$10cm^3 of Na_2S_2O_3 $ was used, find the concentration of carbon monoxide in ppm. (density of air sample =$1.4\times10^{-3}gcm^{-3}$

Question: Why have they used KI solution when collecting $I_2$?

My View: Is it because $I_2$ is readily dissolving in KI ?

P.S. I already did the calculation. Just interested in the following phenomenon.
Thanks


texts: Conversion of s-trans butadiene to s-cis butadiene

texts:
No nodes should be introduced in the rotational interconversion between the s-trans and s-cis forms of 1,3-butadiene.

What is the explanation for that, if one of the $\pi$-systems should rotate $180^\circ$? It seems to be that two positive and negative lobes turn upside down.


texts:
What is the order of basic strength of nitrogens in the compound given in the figure?

$$\ce{
H2\overset{.\!\!.}{\underset{(γ)}{N}}-\overset{.\!\!.}{\underset{(β)}{N}}H-\overset{\overset{\huge O}{||}}{C}-\overset{.\!\!.}{\underset{(α)}{N}}H2
}$$

The most basic is the γ-N since its lone pair can't go in conjugation. My doubt is between α and β nitrogens, whose lone pair can go in conjugation.


texts: Is there a reason to use bases in electrolysis and acids (eg vinegar) for electroplating?

texts:
To me, electrolysis for rust removal and electroplating seem to be the same process, with different metals and goals.

However, in seeing electrolysis and electroplating videos, it seems that electrolysis (for rust removal) uses washing soda, while electroplating uses vinegar.

Similarly, anodizing titanium seems to use a washing/baking soda (base) solution.

I am an EE. It seems to me vinegar would be less conductive. But from a chemistry perspective, what difference does the pH make?

Thank you


texts: What is the mechanism for the photolysis of $\ce{HX}$ to dihydrogen and dihalogen ? From the low quantum yield (0.3% for $\ce{HI}$ according to one paper) it seems unlikely to be a chain process but I am not sure why it would not be.


texts: Getting radial Kohn-Sham orbital from the output of an electronic structure code using gaussian basis sets

texts: As we know that in solving the Schrodinger equation (Kohn-Sham equation), we expand the wavefunction in terms of some basis sets and them optimize the energy (the expectation value of Hamiltonian) by varying the coefficients of the basis in the expansion. Most of the electronic structure codes use the basis sets. What I need is that if I use gaussian basis sets in NWCHEM for example, how would I get radial Kohn-Sham orbitals or the optimized coefficients of the basis? I will be grateful if someone can tell any other option to get these orbitals from different electronic structure code but the one which uses Gaussian basis sets.


texts: Is cobalt (III) hexaaqua paramagnetic or diamagnetic?

texts:
The complex ion $\ce{[Co(H2O)6]^3+}$ has $\ce{Co}$ in the $+3$ oxidation state, meaning it has an electron configuration of $[Ar] 4s^0 3d^6$. Therefore it has 4 unpaired electrons and would be paramagnetic.

However, in the octahedral complex ion, the d orbitals split into two levels, with three lower-energy orbitals and two higher-energy ones. The six d electrons would therefore be in the lower set, and all paired. Following this logic, the $\ce{Co}$ atom would be diamagnetic.

Which is correct?


texts: Does the mass of sulfur really decrease when dissolved in water and increase when burnt?

texts:
I was going through a bunch of interesting science 'facts' and one entry went this way:

  Name an element whose mass decreases when it is dissolved in water and increases if it is burnt.

I tried guessing, but that didn't help. So I had a look at the answer: it was Sulfur

There are two questions that struck my mind after I saw the answer:

What does mass decrease/increase as stated here mean?(Does it mean that mass of sulfur along with other elements combined with it changes/or anything ambiguous such as change in actual mass is taking place) )
Is sulfur really the correct answer to that question? If yes, then why does sulfur show this anomalous property? Are there elements that display a similar property?

Any suggestion is welcome.


texts: Biopolymers as alternative for PVC and PU?

texts:
I'm working on a project making a product line more sustainable, environmentally friendly and ready for recycling.

Now I'm searching for good and suitable biopolymers for a part of the product that is made from PVC and one for PU (Polyurethane). For PES I already have chosen PLA. Is there someone who can help me select the right biopolymers with similar characteristics of PVC and PU?

Please let me know, thank you!


texts: Why is the bond order in the SO₃ molecule 1.33 and not 2?

texts:
$\ce{SO3}$ molecule has three double bonded oxygen to the central sulfur atom.

Sulfur has $\ce{sp^2}$ hybridization and it has 6 outer electrons which make the bonds with the oxygen.
So shouldn't the bond order be 2?


texts: Group 15... Lewis Acid, Lewis Base or Not At All?

texts:
I am a long-time reader of this forum, but this is my first time post. I am a chemistry undergrad with a question about Lewis acidity or basicity of Group 15 compounds.

I know Lewis acids act as an electron pair acceptor and a Lewis base as an electron pair donor. Then sometimes a dative bond is formed between the two, forming a Lewis adduct (as per classic $\ce{NH3}$ and $\ce{BF3}$ reaction). But this is where my knowledge becomes a little sketchy, and hence my question:

When considering group 15, is it possible for the elements of this group to form compounds which are either Lewis acids or bases?

Firstly, the requirements for Lewis acids of group 15, is it empty d-orbitals or an incomplete octet which give a compound the ability to accept two electrons?
Therefore, would this make $\ce{PF5}$ an acid (d-orbitals)? Would $\ce{AsF5}$ be classed as an acid? (If so, is this due to $\ce{As}$'s ability to violate the octet rule coupled with the fact $\ce{As}$ is very positive in this compound).

Then are the requirements for something to be a Lewis base purely the presence of two non bonding electrons? Would this then make compounds such as $\ce{AsF3}$ and $\ce{PF3}$ bases?

I am a little lost, would like to know if the above is along the right lines. Do things like electronegativity and atom size play a part?

I think this is a base?

I think this is an acid?


texts: Salt + Sodium Bicarbonate releasing water in carpet

texts:
I had some fleas issues so I read about putting salt and sodium bicarbonate in the carpet and in the edges with the purpose to reduce the humidity and dehydrate eggs and larvae. After few days, the weather changed, to humid, rainy and foggy. UK weather... Suddenly, out of nowhere I found all the floors and carpets humid and specially in areas where the mixture was more abundant, there were quite a lot of drops of water.
I wonder why. Probably the hygroscopic property of salt and sodium bicarbonate, in a change in humidity or atmospheric pressure released the water accumulated during several days. I have no idea.


texts: Is organic chemistry mechanisms limited to organic chemistry?

texts: I am curious to know the mechanism of each reaction. Organic chemistry is satisfying for me because there is a mechanism behind each reaction which make a sense but when I Google for the mechanism of inorganic reaction I do not find any good results. I applied an organic reaction mechanism on an inorganic reaction and it worked as shown in the picture. By summarizing "Can we apply organic reaction mechanisms to inorganic reactions?"


texts: How does monoethanolamine (MEA) increase pH?

texts:
I know pH of a solution increases with increase concentration of $\ce{OH-}$.

I'm wondering: when adding MEA, is the $\ce{OH-}$ group from the MEA breaking off, or is it the whole MEA molecule taking a hydrogen from $\ce{H2O}$ leaving the $\ce{OH-}$?


texts:
When I prepare sodium perborate by mixing sodium hydroxide with metaborate ($\ce{NaBO}$) and hydrogen peroxide and cooling it I applied a test to it by acidifying it with $\ce{HCl}$ and adding $\ce{KMnO4}$. A precipitate appeared and it turned black. What is the reason?

I tested another sample of sodium perborate by acidifying it with $\ce{NH4Cl}$ and after that KI and this turned white. Again, why?


texts: Can a magnesium atom combine with just one chlorine atom?

texts: If I have a magnesium atom and a chlorine atom why can't the magnesium atom combine with just one chlorine atom? Wouldn't the magnesium atom become more stable, than it was before combining, as it gets closer to octet after combining with one chlorine atom?


texts: What chemicals cause the softer, less-raw taste of purified water sold in bottles?

texts:
I've seen the post, "What defines an element's taste?", but it doesn't answer my question.

I took water that is supplied by the municipality corporation and put it through a gravity based water filter. The taste of the water didn't change. It still had a raw, tap-water kind of taste.

However, if I buy one of the 20-liter cans (they charge x+y for the water+can and when you return the empty can, they return y amount of money), the water tastes softer and less tap water-ish.

A 2-liter bottle of mineral water costs x. Which is the same as the 20 liter can cost. So I'm wondering if they really purify it or whether they just add a few chemicals to it to fool people into thinking the water is purified. They might just be supplying us with ordinary tap water or borewell water.

Are there any chemicals that can change the raw taste of water? Maybe the raw taste caused by chlorine.


texts: How could I produce/rig this flame-colour lottery?

texts:
Not sure if this is the wrong SE for this, happy to move it if not...

In the Netflix TV series Sabrina, there is a scene where people take part in an appropriately-gothic-and-ominous lottery, which proceeds as follows:

Fourteen participants draw, one at a time, pieces of paper from a box.  The papers are all blank and have no differences visible to the human eye in the (rather moody) lighting.
The participants burn their paper in the flame of a candle which is in front of them.  There is a separate candle for each participant, but they all appear to burn with the same yellow flame.
Twelve of the papers burn up quickly, like flash paper.  The other papers burn more slowly, and release red (for the 'runner up') or white (for the 'winner') smoke, respectively.

   The runner up waits on the winner hand and foot for three days, and then the winner is killed and eaten cannibalistically, with a strong religious 'ascension' dogma.

Depending on your point of view, this is a lottery you may or may not want to win, and also one which there would be great advantage in being able to rig to ensure a particular winner.  So my questions are:

What chemistry could you use in the papers and candles to achieve the effects shown?


texts: Is there any database, or reference, for retardation factors (Rf)?

texts: I'll like to compare the Rf of myrcene, obtained in Thin Layer Chromathography, for different species.  Toluene:Ethyl Acetate (97:3) would be fine, but is not a necessity.


texts: In sp² hybrid orbital, why does the p orbitals only have 3 sides instead of 4?

texts:
Usually two separate p orbitals would have '4 lobes' while in a $\ce{sp^2}$ hybrid those 2 p orbitals would only have '3 lobes'. why?

I'm referring to diagrams such as the one shown below:


texts: Is it possible to make polyethylene in a high school laboratory?

texts:
We learned how to make small amounts of ethene from ethanol using sulfuric acid.

Is there a way to make a visible amount of polyethylene from that using materials I could get for a school lab? We can't do pressures of 1000+ bars obviously, but we don't need high efficiency either -- just enough of a solid for the students to see that something happened.


texts:
I read that B3+ ions do not exist in aqueous solution, because hydration energy cannot compensate for the sum of first three ionisation energies.

This leads me to the following questions:

If boron (III) ion really doesn't exist, how was the hydration energy data calculated? and ionisation potentials?
Boron being small in size and carrying a high charge of +3 (if it exists) should be greatly hydrated. This high hydration energy should be able to compensate for the ionisation energies, but it is not so.

Could someone please explain?
Thanks!


texts: Alternative to Hanging Drop Crystallization

texts:
Forgive my ignorance if I am way off, but I was having a look at the crystallization of a number of different substances (e.g. proteins) through the hanging drop vapour diffusion method.

The examples given use a precipitating agent (e.g. $10~\%\ \ce{NaCl}$) at the bottom of the well and then you put the liquid protein you are looking at upside down on the top cover and the water moves from the protein into the precipitating agent, slowly crystallizing the protein.

So my question is, for simplicity would it be possible to use a divided container (e.g. petri dish) which has two compartments that share the same atmosphere to achieve the same thing, that is have a container that has a salt solution on one side, and the solution I wish to crystallize on the other?

Would this likely work?


texts: Is the first step of most the accepted mechanism of Perkin's reaction correct?

texts:
If I am not wrong this is the most accepted mechanism of perkin's reaction:

In the first step, is the acetate ion basic enough to abstract proton from acetic anhydride?
If yes, I have a counter arguement. It is well known that acetic anhydride doesn't answer iodoform test despite having an acetyl group. It is mainly because, abstraction of proton is not possible as it would produce a unstable carbanion (because of cross conjugation).
If OH- cannot abstract the proton iodoform rxn. , how could acetate ion which is a weaker base abstract the same proton in Perkin's reaction?


texts: Distance between successive tetrahedral voids in FCC

texts:
What is the distance between successive tetrahedral voids in a FCC
crystal structure?

The distance between a face centered atom and a tetrahedral void is $\sqrt{\frac{3a}{4}}$ if the cube's edge length is $a$. Now If I know the angle made, between the line joining a tetrahedral void and the face centered atom, and the successive tetrahedral void and face centered atom, I can find the distance.  But how do I calculate that distance since I don't know the angle.


texts: Trying to understand the necessity of orbital approximation or the independent electron model

texts:
I'm reading the approximations used for solving the Schroedinger's equation for molecules; the first is the the Born-Oppenheimer approximation:

  Freeze the molecule with a fixed internuclear separation $R;$ then carry
  out calculations to obtain the total energy, $U,$ and wavefunctions for that $R$ value.$^1$

Then another approximation is used which is known as the orbital approximation to get rid of the inter-electronic repulsion as said by the same source.

  Consider each electron to move in some sort of "average potential" which incorporates the
  interactions with the two nuclei and an "averaged interaction" with the other electron.

  The electronic Hamiltonian can then be separated into two parts:
  $$\hat{H}_e = \hat{H}_1 + \hat{H}_2 \\ \text{where}:\\ \hat{H}_1 \;\text{is dependent only upon the properties of electron (1) and upon R .}\\ \hat{H}_2 \;\text{is dependent only upon the properties of electron (2) and upon R .}$$

I couldn't understand for what purpose this approximation is meant for. Also, I couldn't able to conceive what average potential actually means.

I then googled the term finally to come before a pdf file where it is written that

  $\color{red}{\bullet}$ Electrons repel each other according to Coulomb's law,
  with the repulsion energy $r^{-1} _{ij} .$

  $\color{red}{\bullet}$ Hartree-Fock replaces this instantaneous electron-electron
  repulsion with the repulsion of each electron with an
  average electron charge cloud.

Prior to that it is written:

  $\color{red}{\bullet}$ It assumes that each electron interacts with an average
  charge distribution due to the other electrons. This is
  wrong!

I've spent a hard time understanding this approximation.

Could anyone please explain why this approximation is taken & how it actually solved that problem? The source cites the reason of inter-electronic-repulsion as the problem; how does this term in the Hamiltonian cause problem & how is it solved by the approximation? Also, what is meant by average potential?

An intuitive explanation would be appreciated.

$^1$ http://www.chem.qmul.ac.uk/software/download/mo/3.pdf


texts: Does hyperconjugation only arise from C–H bonds?

texts: I have to an extent understood hyperconjugation but I don't understand why the donation can only occur from a $\mathrm{sp^3}$-hybridised orbital bonded with hydrogen? What about other bonding partners?