The study of chemical systems using the laws and concepts of physics. This usually requires the techniques of thermodynamics, statistical mechanics and quantum mechanics.

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15 views

Is this equation of state original?

I created this equation of state as a personal undergraduate summer project seven years ago https://www.docdroid.net/ygLo4Gu/equation-of-state.pdf.html I tried to show it to my professors but none ...
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2answers
41 views

How should I think about potential energy surfaces for reactions of complex systems?

I've recently started doing some computational chemistry, studying the reaction dynamics of some moderately complex organic and inorganic reactions. I'm doing things like finding maxima, minima, TS's, ...
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24 views

Explaination for covalent solids being brittle

Brittleness of Ionic solids is caused due to repulsion between similar charges when layers slide.But Covalent Solids do not have such repulsions. Do they ? so why are they described as being ...
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15 views

Question on surface tension and adsorption

I just read that positive adsorption is observed with solutes which are hydrophobic when water is the solvent, and alcohol in water is given as an example (which was then generalized as polar organic ...
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1answer
25 views

How to obtain saturated pressure of water at 200 ºC using fugacities

The target is to obtain saturated pressure of water at 200 ºC using PHI-PHI (fugacity coefficients) approach,so it means it's a VLE of water only,so we write equilibrium condition: $f_i(l)=f_i(v)$ ...
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1answer
26 views

What is the difference between the chemical potential μ and the molar Gibbs free energy Gm?

I'm not too sure if I understand this correctly: Is the $G_\mathrm{m}$, the Gibbs free energy of the entire system, divided by the amount of substance making up the system, while $\mu$ is the Gibbs ...
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10 views

Mass of gas calculations [on hold]

Which mass of gas would occupy a volume of 3 dm3 at 25 degree celcius and 1 atmospheric pressure? i tried using PV=NRT but cannot get the right answer.
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19 views

Is UV-Vis absorption polarization dependent ? Why?

Consider molecule of interest be dissolved in a solvent (and this molecule has absorption in the visible region). We are using a broadband visible light source say tungsten lamp. This light passed ...
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1answer
31 views

Spin of electrons about it's own axis, release of energy & COLLAPSE of atom?

An electron spins about it's own axis. So it has rotational accln. Thus, according to Maxwell's Electromagnetic Theory , Rotational Kinetic energy must be released. Thus, at some pt. of time , ...
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1answer
46 views

How to derive Van't Hoff equation for Henry's constant

While studying about Henry's Law, I encountered this equation,I didn't know how to derive it so I searched about it and got nothing, I tried to substitute $H$ (Henry's const.) by $\gamma\cdot f_i$ ...
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0answers
14 views

eudiometry(gas analysis) [on hold]

40 ml gaseous mixture of CH4,CO2,Ne was exploded with 10 ml of oxygen .On cooling , the gases occupied 36.5ml . after treatment with KOH the volume reduced by 9 ml and again on treatment with alkaline ...
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11 views

electrons of cathode ray comes from where? from cathode metal or gas in discharge tube? [closed]

The particles constituting cathode rays ( electrons) are of metal with which cathode is made up of or of the gas filled in discharge tube?
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1answer
14 views

XlogP of octanol and water itself

According to Pubchem, the XLogP of octanol is 3 and that of water is -0.5. Why aren't they both 0 or 1 which seems to make more sense to me?
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0answers
14 views

Equilibrium potential example

Hi guys, just wondering if there is a mistake my lecturer made with this example she gave in one of her lectures, according to the Nernst equation, the oxidised species should be at the top and the ...
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1answer
26 views

Temperature in the Gibbs Free Energy equation

My professor gave us 2 different ways to calculate this problem. I did it using the Clausis-Clapeyron equation. However, I don't quite get the second method because I thought that if the change in ...
10
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1answer
138 views

Does aromaticity require a co-planar pi system?

It's well established that angular twisting can decrease the degree of delocalization across a $\pi$ system (e.g. biphenyl). Moreover, there's considerable debate about aromaticity in spherical ...
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1answer
30 views

Can sodium acetate anhydrous be used as a desiccant?

Sodium acetate trihydrate can be converted to sodium acetate anhydrous easily with an oven. I've been told to quickly store sodium acetate anhydrous in a sealed container because it takes water from ...
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2answers
46 views

Difference bewteen polarizability and dipole moment?

In my head, any molecule that is very polarisable, has a dipole moment. Is this true? I am very confused and can't seem to find anything that helps my thought, and I can't seem to distinguish between ...
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1answer
68 views

Why is the first ionization enthalpy of zinc higher than expected?

The following sentence is stated in my current chemistry book:- "The first ionization enthalpy of Zinc is higher because it represents an ionization from the 4s level". Now zinc does have an ...
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37 views

Way to decide if a solid is crystalline or amorphous besides experimentally?

If am asked to classify the given solids into crystalline or amorphous, but how can I proceed without having any prior information. The exact question was: Classify into Crystalline or Amorphous- ...
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17 views

Why Heating turns Amorphous to Crystalline and How?

I found this answer here but iam still confused: "Polymer chains are entangled and frozen in an amorphous state. The role of heating is to liberate these entangled chains, so some parts of chains are ...
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0answers
72 views

Estimating stability and mean life of anomalous tautomers

A pair of bases in the DNA, say, A-T, have a tautomerized form A*-T* (resulting from switching the sides of both protons along the hydrogen bridges). I have studied how, by means of DFT computations, ...
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0answers
25 views

potential profile in kinetics and spontaneity in reactions

We usually think of the criterion of spontaneity of a reaction as the change of Gibbs energy. By Clausius inequality, one of various forms of the 2nd law, we know that $ ...
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1answer
18 views

What is generally meant by distinct line spectrum?

In a single hydrogen atom the electron is excited to 6th orbit. The book says maximum 5 distinct spectral lines are possible when the electron comes to the ground state. Looks like they have only ...
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1answer
45 views

Is this a phase change in a gas under Thermodynamic Equilibrium?

The above graph shows the molar density (i.e. n/V from PV=nRT) of a gas plotted against pressure. There are two regions with ...
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1answer
21 views

Is this gas in thermodynamic equilibrium?

Please consider the following graph of Molar Volume against Pressure for a fixed volume Can we say whether this system under thermodynamic equilibrium or not? Update Thinking about this some more, ...
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15 views

Challenging modern formula to calculate molecular mass of solute from relative lowering in vapour pressure

According to modified form, $\frac{P-p}{p} = \frac{n}{N}$, where: $p =$ partial pressure of solution, $P=$ partial pressure of pure solvent $N=$ mole fraction of solvent $n=$ mole fraction of ...
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34 views

(Literature) Diffusion Coefficient Of Potassium Permanganate

I'm doing a practical report on an experiment I had this week where I studied the diffusion coefficient of KMnO4 in water by the free boundary method. I have calculated the diffusion coefficient of ...
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1answer
27 views

What's the relationship between dew point and temperature?

From a Ph.D dissertation, the writer change the land surface from nature earth to urbn and built up to compare the difference ...
5
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0answers
51 views

Vapor-pressure or Vapor-concentration

To summarize from my textbook: rate of evaporation: proportional to surface area but essentially independent from pressure (of surrounding gas) rate of condensation proportional to both surface ...
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0answers
31 views

Ionic radius paradox

consider a compound AB which forms cubic close packing(FCC) structure in which B forms FCC and A occupies the octahedral voids.let x and y be the radius of A(cation) and B(anion) respectively.if we ...
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1answer
57 views

How to understand Nelson-Obert charts?

The compressibility factor is given by: $$ z=\frac{P\overline{V}}{RT} $$ The Nelson-Obert chart is: This chart brings the following information: At very low pressure (Pr << 1), gases ...
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38 views

pH of a double buffer

If $1,2,3,4$ moles of $\ce{H3PO4}$,$\ce{NaH2PO4}$,$\ce{Na2HPO4}$ and $\ce{Na3PO4}$ respectively are mixed together to form an aqueous solution of $1$Litre , resulting $\ce{pH}$ is? This question has ...
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3answers
88 views

What is the difference between ΔG and ΔrG?

Consider the reaction $$\ce{A -> B}$$ The reaction Gibbs free energy, $\Delta_\mathrm{r} G$ is given by the following equation $$\Delta_\mathrm{r} G = \Delta_\mathrm{r} G^\circ + RT \ln Q$$ Now ...
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18 views

Choice of Dopants for Semiconductors [duplicate]

Excuse my grammar errors... While I'm trying to learn the work principle of a solar cell, I realize that doped semiconductors play a very important role and thus I have to also learn more about them. ...
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0answers
23 views

Making a glow in the dark substance glow only when heat is applied

I want to make a glow in the dark substance that glows only if it gets warm. How do I obtain this substance, or what chemicals to I need to mix to make it? It's going to go in a sealed glass jar ...
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0answers
30 views

Equilibrium Problem Involving Solids: Faulty?

I am convinced that this is a faulty problem: $\ce{2 Cu + S -> Cu2S}$ For the reaction above, $\Delta H$, $\Delta S$, and $\Delta G$ are all negative. Which of the substances would ...
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15 views

Reducing water content of gypsum/plaster powder. I'm having caking problems

I have a gypsum/plaster of paris powder that I need to pass through a mesh filter. However, the powder keeps on caking at the mesh filter due to what I suspect is the high water content. The powder ...
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1answer
48 views

Volcano plots: How is the data fitted?

When studying about catalysts I normally come accross volcano plots like the one shown below: What confuses me is how are the two lines fitted, how do you determine what points to include and what ...
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0answers
26 views

Why is ionisation energy defined for gaseous species? [duplicate]

Most high school and college textbooks usually define the first ionisation energy as such: The first ionisation energy is the energy required to remove 1 mole of electrons from one mole of ...
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1answer
30 views

A doubt in chemical equilbrium

say we have a reaction N2O4 reversible 2NO2 for this reaction,if initial number of moles of N2O4 is 'a' can we write t = 0 a - at equilbrium a-x 2x similarly can we do the same for pressure? i.e. ...
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0answers
51 views

Gibbs Free Energy and entropy of the universe

I'm having a little bit of trouble after putting alot of thought into the relationship between entropy of the universe and Gibbs Free Energy. Both are used to predict spontaneity, but from my ...
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2answers
60 views

A problem from thermodynamics

I am trying to do the following problem: Freezing of water at $273~\mathrm K$ and $1~\mathrm{atm}$ Which of the following is true for the above thermodynamics process? p) $q=0$ q) ...
3
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1answer
54 views

What is the difference of molar volume between dissolved 35Cl- and 37Cl-?

Im am geochemist, dealing with isotopes such as 35Cl and 37Cl. For some model I'm trying to make I need to be able to estimate what is the difference of partial molar volume between dissolved 35Cl ...
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1answer
77 views

Doubt regarding the second law of thermodynamics [closed]

$$\frac{q_{rev}}{T} = \Delta S$$ Here, what does $\Delta S$ signify? Does it mean the change in entropy of the system or the surroundings? How are the entropies of the system, the surroundings, and ...
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0answers
9 views

is it possible to use a luminescent chemical in a refrigeration system to detect small refrigerant leaks?

I know there is a flourescent chemical that can be added into refrigeration systems to identify refrigerant leaks but they have to be large leaks where oil is actually leaking from the system, my ...
3
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1answer
55 views

Understanding effect of ph on solubility of salt

In the following picture why Ksp is not simply S2- ? Why is f included with one species only? Please explain the last part. What does f represent and why it is used in molar solubility?
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28 views

Application of ideal gas law equation [closed]

I'm given this problem Total number of moles of oxygen atoms in 3 litres of $O_2$ (g) at 270°C and $8.21$ atm are: I know that I can simply use PV $=$ nRT and just by plugging the values I can get my ...
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0answers
40 views

Unit cell question on determining compound stoichiometry of KCoS?

For 5(a) and 5(c), how are we determining that the answer is K4CoS4? I keep counting it and getting K2CoS2. We know that the K and the S ratio must be 1:1, but how can we count the Cobalt? . ...
3
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3answers
51 views

How is mean square displacement defined in Brownian motion?

I am trying to calculate mean square displacement (MSD) of water in a simulation to calculate its diffusion coefficient. However I am little confused on its exact form. Can anyone please explain it in ...