Questions tagged [physical-chemistry]

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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An ideal gas is undergoing an isothermal expansion against a constant external pressure. Which of the following statements is true?

An ideal gas is undergoing an isothermal expansion against a constant external pressure. Which of the following statements is true? 1) This process is reversible. 2) This process is ...
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Most exothermic FeBr2 + Cu(OH)2 reaction? [closed]

What is the most exothermic reaction of $\ce{xFeBr2 + yCu(OH)2}$ where x and y are determined by that reaction? Note: I'm not asking for an equilibrium distribution of products but rather for the one ...
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Is the molecularity of the slowest step equal to the order of the slowest step of the same reaction? [closed]

My book says "YES" , to the above question. However, i say "NO" . Please tell me whether my book is right or me.
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Would a Acrylic Plexiglass tube be safe to smoke out of? [closed]

Sorry for the dumb question, but I used to have a tube made out of polycarbonate material that was used to smoke in the form of a steamroller but I've since lost it. I think the company went out of ...
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Why is it experimentally difficult to accurately find the critical volume of a real gas?

I was reading up on the derivation of the values of various critical state functions( $\ce{Vc}$, $\ce{pc}$ and $\ce{Tc}$) from the Van der Waals equation (Physical Chemistry by G.W. Castellan). There, ...
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Frequency region and “uncoupled oscillators” in vibrational spectroscopy

I am currently studying the textbook Infrared and Raman Spectroscopy by Larkin. In the first chapter of the textbook, the author presents the following table and accompanying explanation: The ...
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43 views

Enantiomers to diasteroisomers (rotational spectra)

Enantiomers have identical rotational spectrum because their mass distributions are identical. Recently a trick has been introduced in microwave spectroscopy in which a enatiomerically pure gas chiral ...
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2answers
50 views

Can you approximate the change in entropy of a reaction?

I found a problem in which I am given a hypothetical reaction in which from 2 liquids (reactants) I get 4 moles of gas and 1 mole of a solid substance (products): $$\ce{A (l) + B (l) -> 4C (g) + ...
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if we a have a molecule can we calculate its energy as a whole with it bonds electrons and protons and neutrons and to how match accuracy [closed]

sry i well explain better and simplify if we a have a molecule can we calculate its energy as a whole with it bonds electrons and protons and neutrons and to how match accuracy
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28 views

Period of palladium [closed]

The configuration of palladium is 2,8,18,18. Then what is it doing in the 5th period? Is there an explanation without the concept of subshells?
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29 views

How can there be concentration and pressure terms simultaneously in the Nernst equation?

In the Nernst equation we are taught that the reaction quotient can have pressure terms and concentration terms simultaneously. According to my knowledge this does not happen anywhere else, so why can ...
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Understanding reason behind existence of chemical equilibrium

Many chemistry reactions are reversible in nature. In such reactions initially reactants react to form products but after some time products also react to give reactants back again. And an equilibrium ...
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To understand reason behind large difference between melting points of carbon and nitrogen [closed]

Carbon is group 14 element having melting point above 3000°C while its adjacent element nitrogen has very low melting point i.e. -210°C . Why do they differ in their melting points upto such a large ...
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38 views

Activation energy vs temperature [closed]

We know that activation energy is independent of temperature. But during the dehydration of alcohol or any reaction, activation reaction can be increased by following the thermodynamically controlled ...
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1answer
49 views

Raoult and Henry's law

According to my textbook, for Raoult's law, we have: $$μ_i(\mathrm{vap}) = μ_i^* (p_i^*,T) + RT \ln⁡ x_i$$ where $μ_i^* (p_i^*,T)$ is the chemical potential at $T$ and $p_i^*$, the pressure of pure $...
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Why isn't ΔH = TΔS in ΔG = ΔH - TΔS?

Applying a Legendre transformation on $U = q - w$ we get the familiar $G = H - TS$. Making an innocent approximation delivers $\Delta G = \Delta H - T\,\Delta S$. When one wants to predict the ...
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How do we calculate the force of a kinesin molecule? [closed]

In a physical chemistry book, we learn how to calculate the force of lifting yourself up against gravity. The force is equal to the body mass times gravitational acceleration. Then in the next problem ...
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How can the rate of reaction between thiosulfate ion and acid be calculated as v = 1 M/Δt? [closed]

The experiment is done in the following way: Sodium thiosulfate is added in a beaker (the concentration is noted). Acid is added (the same amount each time). Time is taken till the reaction reaches ...
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Free electrons of the wire in a galvanic cell [closed]

In a galvanic cell, do the free electrons contained inside of the conductive wire actually flow since a voltage is created across the wire, or is it just the electrons produced by the redox reaction? ...
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86 views

How to set up an equation to solve a rate law computationally?

I am confused on how to set up my equations to use in the solver. I have an equation $$\ce{A + 2B -> C}$$ As a given, it is first order in A and second order in B. What I need to do is to solve for ...
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27 views

What is the activation energy of a Daniell cell?

I'm having trouble finding a posted literature value for the activation energy for the Daniell cell redox reaction: $$\ce{Cu^2+ + Zn -> Cu + Zn^2+}$$ Where might I be able to find this ...
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About ∆G in standard conditions and Graph of ∆G vs temperature for few reactions [closed]

I have this graph Notice: $x$-axis is temperature in Celsius ($\pu{^\circ C}$) and the rest is the numbered reactions as follows: $$\ce{2Mg + O2 -> MgO} \tag{1}$$ $$\ce{2Zn + O2 -> 2ZnO} \tag{...
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Why are colloidal dispersions stable? [closed]

Smaller particles in a colloidal dispersion are less stable than larger ones due to their higher surface to volume ratio. Therefore Ostwald ripening occurs, a process which promotes growth of larger ...
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In which order should I learn Thermodynamic [closed]

I study physical chemistry on my own and I have to decide in which order I learn the following topics These are my topics: Statistical Thermodynamics (especially entropy, partition function, ...
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Finding (∂U/∂V )T = n^2a/V^2 for a van der Waals gas [closed]

$\displaystyle dU = \left(\frac{\partial U}{\partial T}\right)_V dT + \left(\frac{\partial U}{\partial V}\right)_T dV \to dU = C_v dT - C_v\left(\frac{\partial T}{\partial V}\right)_U dV$ Not sure ...
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Determining molar mass of protein from osmotic pressure

A 299 mL solution containing 21 g of a protein in toluene had an osmotic pressure of 0.053 atm at 27 degrees Celsius. What is the molar mass (in g/mol) of the protein? We can use the formula that $$\...
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18 views

For what processes is mayor's formula applicable?

I know that Cp-Cv=R but I have also seen Cp-Cv=R/M being used in case of ideal gas. So in what cases the former is used and in what cases is the latter used?
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35 views

Regarding the infinitesimal form of the First Law of Thermodynamics

First Law of Thermodynamics is expressed as[1] The internal energy of an isolated system is constant. If $w$ denotes the work done on a system, $q$ for the energy transferred as heat to the system,...
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1answer
44 views

Rate of reaction involving different stoichiometric coefficients

Suppose I have a reaction (Say it is the Haber process): $$\ce{N2 + 3H2 <=> 2NH3}$$ If we have to calculate the average rate of reaction of the above we follow the reasoning the rate of ...
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1answer
72 views

Beer's law: UV-Vis absorbance values exceeding 2

In classical analytical chemistry, absorbance values in Beer's law can theoretically range from 0 to infinity. As general rule of thumb neither high, nor very low absorbance are used for ...
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Order of Reaction differs in equation and linearisation

I have given the following equation: $A + 2B \rightarrow C$ $ v = –k\cdot [A]\cdot[B]^2$ gives me the orders 1 for A and 2 for B. That results in a total order of the reaction of 3. So far so good. ...
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67 views

What happens to the crystal structure of ice as it gets colder and colder [duplicate]

Not sure if this belongs on Chemistry or Physics stackexcahnge. As water freezes into ice, it turns into a solid, and expands as it forms a crystal structure. But what happens to this crystal ...
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60 views

How are reaction enthalpy and entropy affected by temperature

The equation for Gibbs Free Energy demonstrates how the standard change in Gibbs Free Energy for a reaction is affected by temperature. $$\Delta G^\circ = \Delta H^\circ - T\,\Delta S^\circ$$ ...
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Why does Larmor precession occur in NMR?

Larmor precession is the phenomenon that in NMR the spin (and by default also the magnetic dipole moment) of protons does not line up with the applied magnetic field but rather precesses around this ...
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How does the rate constant change with the change of the temperature?

In class, we discussed the following multiple-choice question. The rate expression for a reaction is: $$rate = k[X][Y]$$ Which statement is correct? A. As the temperature increases, the ...
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why is 4s subshell less enrgetic than 3d? [duplicate]

General rule is that as we move away from the nucleus of the atom the energy of the shells increases but then why 4s is less energetic than 3d although 4s is at more distance from the nucleus than 3d.
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Using osmotic pressure to find the molar mass of a compound

Working on-board a research vessel somewhere at sea, you have (carefully) isolated 12.5 micrograms $(\pu{12.5E-6 g})$ of what you hope is pure saxitoxin (a non-electrolyte) from a poisonous (and quite ...
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Is it possible to use ethyl acetate to extract fat using a Soxhlet?

I am wondering if it is possible to use ethyl acetate as a solvent for extracting fat from a compound using Soxhlet. Correct me if I’m wrong, but I shouldn’t the solvent be non-polar to dissolve fat,...
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1answer
47 views

Spectrum Of Metals [closed]

Recently, I've read that when metals are exposed to a high voltage source, metals produce a spectrum. I am curious on what is the minimum value of that 'high voltage'? Is the spectrum due to the high ...
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2answers
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How can I eliminate the harmful gas produced from the heating/manipulation of galvanized steel? [closed]

When welding on steel with a galvanized coating, hexavalent chromium is yielded from the chemical reaction. This gas is something that I would like to eliminate before I begin welding, possibly with ...
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1answer
53 views

How to derive the steady-state solution for simple two-step reaction with differential equations? [closed]

Consider this simple two step reaction, a variant of a Michaelis-Menten type of problem, where $\ce{A}$ and $\ce{B}$ reversibly bind to make $\ce{AB}$, and $\ce{AB}$ and $\ce{C}$ reversibly bind to ...
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Observing bands which I shouldn't be!

I performed the iodine spectrum experiment to observe vibronic transitions. I heated the iodine crystals to produce vapors (at a little above room temperature) and observed absorption spectrum with a ...
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1answer
58 views

Why is the voltage produced by a voltaic cell affected by temperature as described by the Nernst Equation?

I understand why changing the concentrations of the electrolytes in a voltaic cell affects the voltage. Given a zinc-copper cell for example, if I were to increase the concentration of the zinc ...
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1answer
669 views

Understanding @ symbol used in material science

Hello I'm trying to do some research and came across the phrase "Silicone Rubber/Paraffin@Silicon Dioxide" also written as $\ce{SR/pa@SiO2}.$ Any help in understanding what this means is greatly ...
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Is the active mass of every solid and liquid taken to be unity?

I learnt from my textbook and the question/answer - Why is active mass of a pure solid or liquid always taken as unity? that active mass of a solid or liquid is taken to be unity as: $$[A]=\frac n V=\...
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How will the dielectric constant of water change when ethyl acetate is added?

How will the dielectric constant of water change when ethyl acetate is added? The $\mathrm{p}K_a$ value of weak acids in aprotic solvents will be lower than in protic solvents because the dielectric ...
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2answers
52 views

Does dissociation of molecules into atoms change the volume of mixture?

For example, if $\ce{H2}$ is converted to two $\ce{H},$ does the volume of the mixture change? If it doesn't, does it imply that the work done is $0$ because work is $P\,\mathrm dV?$
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chitosan question [closed]

when chitosan is coated on the surface of iron oxide nanoparticles, are the amine groups of the chitosan pointed out?
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Finding amount of CaCl2 produced in a reaction

The question is as follows: Calcium reacts with chlorine gas to form solid calcium chloride. If $\pu{5.3g}$ of calcium reacts with excess chlorine. Find out how much calcium chloride will be ...
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How can Ellingham diagrams be linked to Gibbs energies of formation?

My textbook quotes the following as the limitation of Ellingham diagram: The interpretation of $\Delta G_\mathrm{f}^\circ$(standard Gibbs free energy of formation) is based on $K$ ($\Delta G_\...

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