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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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What is the hydrated diameter of a lithium ion?

When salts dissolve in water, the anions, cations, and strongly polar water molecules undergo hydration reactions, resulting in the formation of hydrated ions with a specific number of coordinated ...
陈永曜's user avatar
1 vote
2 answers
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Why do reduced variables for gases use their critical constants?

I understand why it's useful to have reduced variables, especially as it is the basis for the theorem of corresponding states. However, I'm having a hard time understanding why the critical constants ...
chemN00b's user avatar
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Bancroft's point

In the last problem (Problem 10.43) within the problem section of Chapter 10 in "Introduction to Chemical Engineering Thermodynamics" (J.M. Smith, H.C. Van Ness, M.M. Abbott, McGraw-Hill, ...
Metal Storm's user avatar
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A first order gaseous reaction - getting the rate law

There is a specific example cited in our NCERT Class 12 textbook, to find out the rate law equation for a general gaseous reaction, $$\ce{A->B + C}$$ It describes the entire procedure as shown: ...
Harikrishnan M's user avatar
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1 answer
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Why is the ionic product of water also the equilibrium constant of dissociation of water?

This answer presents a derivation of the value of ionic product of water at $25^{\circ}\text{C}$. The relation $K_\text{eq} = \operatorname{e}^{-\frac{\Delta_\text{r}G^{\circ}}{RT}}$ is used for the ...
Dodo's user avatar
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NaOH etching time and temperature for Stainless Steels (SS-304) for Surface Preparation for coating

To improve adhesion of TiO2 coatings on stainless steel sample I am treating SS-304 with 1M NaOH for functionalizing the surface with metal hydroxide groups as well as increasing roughness. What would ...
Shah Fuhaid's user avatar
-3 votes
3 answers
106 views

How salt helps to melt ice even when there is no dynamic equilibrium between water and ice?

I am a high school student and I am confused about freezing point depression. We say that when in winter's it gets even colder than normal freezing point Temperature then we use solute to melt ice ...
Virender Bhardwaj's user avatar
1 vote
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History of Azeotrope (azeotropic mixtures)

I'm currently researching the history of azeotropic mixtures for an essay, and I've come across some interesting information. The term "azeotrope" was coined in 1911 by English chemists John ...
Max89's user avatar
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Why is my Briggs-Rauscher reaction not oscillating?

I have been trying to run the Briggs-Rauscher reaction following this guide, which is pretty similar to other guides out there, yet the reaction is failing to not only oscillate, but display any color ...
user16791137's user avatar
0 votes
1 answer
208 views

What is meant by "the position of equilibrium lies left (or right)"?

I am a high school student currently learning about equilibrium. I was told that when there are more products of a reaction formed compared to reactants when the reaction reached the equilibrium, the ...
user377786's user avatar
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1 answer
324 views

How can the double-layer capacitance be constant in the Helmholtz model?

The differential capacitance of ideal electrochemical double layers is constant, as the surface charge $\sigma$ linearily increases with the applied surface potential $\Psi$ relative to the point of ...
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The existence of a principal quantum level or energy shell after the loss of an electron from the outer shell of an atom

With the loss of an electron from $\ce{Li}$ ($\mathrm{1s^2\ 2s^1}$), we get $\ce{Li+}$ ($\mathrm{1s^2}$), then the 2nd shell where the electron had been revolving in $\ce{Li}$ will get disappeared or ...
Shreya Murasing's user avatar
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1 answer
172 views

Gibbs phase rule for azeotrope and Solid-Liquid phase diagram

Azeotrope An azeotrope is a mixture of two or more components in fluidic states whose proportions cannot be altered or changed by simple distillation Applying the phase rule to azeotrope. There are 2 ...
Shira's user avatar
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Surface treatment and current density: electrodeposition of Cd and Ag

I'm currently working on a cadmium and silver electrodeposition project. Let me explain: I'm doing electrolytic surface treatment on low-alloy steels as well as stainless steels. At present, we have ...
Soporelle's user avatar
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How to indicate that a substance is in a standard state?

An superscript circle or Plimsoll is typically used to indicate that a thermodynamic property is that of a substance in its standard state. On the other hand, when writing a chemical equation we ...
Buck Thorn's user avatar
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Dependence of Butler-Volmer equation on n for multiple transferred electrons

I was working on an exercise sheet regarding the RDE results of an irreversible electrochemical reduction, with n transferred electrons. In it, we had to plot the Koutecky-Levich plot at different ...
Mäßige's user avatar
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How do pencil erasers erase on a fundamental level? [duplicate]

One could say we're taking advantage of friction, but I want to dig deeper down to molecular/atomic level: what's the process or chain that happens when one erases from a macroscopic to a more ...
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1 answer
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Quantum Mechanics expectation value help

I am working on the following question: I've so far done the first part of a, finding $H_{so}$ in terms of J L and S. I'm struggling to see how to relate that to $E_{LSJ}$ as it involves the ...
chem12314's user avatar
2 votes
2 answers
143 views

Boiling point, pressure, and Gibbs free energy

The water boiling process can be represented by the equation: $$ \ce{H2O(l) → H2O(g)} \tag{1} $$ Since free energy depends on pressure $$ \left(\frac{\partial G}{\partial P}\right)_T = V \tag{2} $$ ...
Marijus Klp's user avatar
2 votes
1 answer
148 views

Mechanism of adhesion of particles on solid surfaces [closed]

What is the mechanism of adhesion of particles on solid surfaces? How does anything stick to anything, for that matter? Why does cigarette smoke stay so stubbornly on our bodies? Why does perfume also ...
damacc's user avatar
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1 vote
1 answer
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Does Hess' law in standard conditions involve consuming all reactants?

The standard free energy change for equilibrium problems is relative to both reactants AND products starting at 1 molar. Hess’s law takes the sum of the values for products minus the sum of the values ...
Alfred's user avatar
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4 votes
0 answers
306 views

Reason for positive enthalpy and volume change of mixing for mixtures showing large positive deviation from Raoult's law

At onset let me make it very clear that similar questions do exist already on this site, but none of them has a kind of answer I expect, hence I ought to ask a fresh question. It may appear that this ...
Qwerty's user avatar
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5 votes
1 answer
161 views

Calculating partial pressure: Difficult cubic equation in bulky Chemical Equilibrium numerical

The problem, which I found in a popular book for Physical Chemistry, written by Neeraj Kumar, is fairly simple, being simply 2 equations and 2 variables, yet its simplification is a nightmare. $\pu{5 ...
Bongo Man's user avatar
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1 answer
107 views

Charge as a function of time in electrolysis

According to Faraday's laws of electrolysis, $\frac{Q}{Z}$ = no. of moles of substance released (n), where Z is n-factor x 96500. Assuming the electrolyte is a strong electrolyte, specific ...
chocolate kiwi's user avatar
2 votes
1 answer
111 views

What is the purpose of the reflux ratio for solvent extraction?

Not distillation If I understand it correctly, in my example, one has two components, A and B, starting at the "feed" in the aqueous phase. They get both extracted in the mixer settler, but ...
P M's user avatar
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6 votes
1 answer
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Potential Energy Function for Two Atoms

The potential energy between two atoms, in a molecule, is given by $$U(x)=\frac{a}{x^{12}} -\frac{b}{x^6}$$ where $a$ and $b$ are positive constants and $x$ is the distance between the atoms. The atom ...
Starlight's user avatar
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1 answer
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Entropy of the system is different for irreversible and reversible adiabatic process?

Entropy change of a system is a state function... But if we consider reversible adiabatic process, the entropy change of the system is zero, whereas the entropy of the system is greater than zero in ...
Natasha J's user avatar
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0 answers
49 views

Energy Decomposition Analysis for SN2 involving ambident nucleophiles and an alkali metal counterion

I am wanting to perform an EDA on transition state structure of the nucleophilic attack of an ambident nucleophile (2 atoms that could be used in nucleophilic attack on the same molecule) on a benzyl ...
MrAmateurChem's user avatar
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1 answer
113 views

Why does Raman Activity Require Anisotropic Polarizability?

Normal mode of a molecule needs to involve the change in molecular polarizability (anisotropic polarizability) to be Raman active. Explanation is provided in Physical Chemistry textbook by Atkins on ...
Dario Mirić's user avatar
2 votes
2 answers
286 views

How does steam distillation work to extract a substance from a mixture, below its boiling point?

This is a small confusion I have regarding steam distillation. Let us consider a sample of water mixed with an organic compound that is insoluble in water. Let us also consider that the boiling point ...
donthababakka's user avatar
1 vote
1 answer
148 views

Calculation of formation heat given molar heat capacities and reaction enthalpy

Consider the following reaction for the formation of liquid water at $\pu{298 K}:$ $$\ce{H2(g) + 1/2 O2(g) -> H2O (l)} \quad \Delta_\mathrm rH = \pu{-286 kJ/mol}$$ If molar heat capacities (at ...
Harikrishnan M's user avatar
0 votes
1 answer
62 views

Reaction kinetics exercise for hydrogen iodide synthesis

The rate constant for the reaction of hydrogen with iodine is $\pu{2.45E-4 M-1 s-1}$ at 302 °C and $\pu{0.905 M-1 s-1}$ at 508 °C. a. calculate the activation energy and Arrhenius preexponential ...
wengen's user avatar
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0 votes
2 answers
119 views

Why does the reaction "pause" when the battery is not connected to a circuit? (or does it?)

The general set up, In an alkaline battery, the negative electrode is zinc (Zn) and the positive electrode is manganese dioxide ($\ce{MnO2}$). The alkaline electrolyte of potassium hydroxide (KOH) At ...
Reuben's user avatar
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1 vote
0 answers
47 views

Electrochemical double layer formation

I was revisiting some of my notes about the electrochemical double layer but I have some doubts, and even the textbook of Bard and Faulkner could not really help. In electrochemical systems, at the ...
Mäßige's user avatar
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1 vote
0 answers
87 views

Why is the standard enthalpy of formation temperature-dependent in JANAF tables?

I'm unsure why $\Delta_\mathrm{f}H^\circ$ within the NIST-JANAF Thermochemical Tables [1] is temperature-dependent. Wouldn't the $\Delta_\mathrm{f}H^\circ$ represent the enthalpy of formation at the ...
Jacob Ivanov's user avatar
0 votes
1 answer
90 views

How to compute solvent reorganization energy in Marcus' non-equilibrium approach?

I try to solve the following equations for some system solvated in the water. The goal is to obtain value in kcal/mol. Unfortunately, I cannot reach the desired output. May someone help me? The ...
farmaceut's user avatar
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-2 votes
1 answer
96 views

Small (personal) scale sea salt production?

I was looking to try to make a small setup for producing small amounts of sea salt. Ideally a series of evaporation chambers, with a heavy brine as the finished product, that could then be baked. May ...
user139996's user avatar
-1 votes
1 answer
262 views

In JJ thomson's cathode ray experiment why is the effect of gravity on the electron not considered? [closed]

Explaining the setup: The experiment is described in the picture. Instead of the magnets in the picture imagine two circular coils on both the sides with current running through it, this creates a ...
Saif's user avatar
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1 vote
0 answers
27 views

Determination of ground state energy that has the same L and S values

Determination of the energy of a multielectron atom in the ground state can be estimated using the atomic term symbol which involves the values ​​L, S and J. If an atom has the same L and S values ​​...
Jots's user avatar
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-2 votes
1 answer
105 views

How to convert molar volume to volume?

This seems like a simple question that people must have asked already, but I can't find an answer online. I'm not a chemist, but need to use a code that deals with thermodynamics. I am trying to use ...
Ant's user avatar
  • 131
3 votes
2 answers
117 views

Is gas solubility independent of pressure?

My physical chemistry textbook poses this question: Prove the statement that an alternative way to express Henry’s law of gas solubility is to say that the volume of gas that dissolves in a fixed ...
GMoss's user avatar
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0 votes
1 answer
187 views

How can enthalpy of an ideal gas be independent of pressure?

I know that when one applies a manipulation of the Ideal Gas Law to the Maxwell Relations the result that enthalpy is independent of pressure tumbles out of it, i.e., $(\mathrm dH/\mathrm dp)=0$. I ...
MattGeo's user avatar
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0 answers
36 views

How to perform NBO calculations at each point while scanning the bond length?

For a given bond, I would like to perform an NBO calculation for each structure while scanning the bond lengths. Can I use Opt=ModRedundant in combination with pop=nbo? Simply specifying both ...
user139725's user avatar
0 votes
3 answers
180 views

Possible error in textbook question? (Heat transfer)

I am dealing with either (a) a severe misunderstanding of the question, or (b) a wrong textbook answer. Here is question verbatim: A jacketed vessel is used to heat a water stream using steam ...
Lim Min Kang's user avatar
-1 votes
1 answer
60 views

Where does the relation Λm=κV come from? is it experimental?

I was learning about molar conductivity in electrochemistry and this relation Λm=κV came up in my textbook. it somehow '...
chemistrylearner's user avatar
-1 votes
1 answer
82 views

First order kinetics

Finding time t in a first order reaction (JEE Adv 2019) In reference to the above question,taking into account the stoichiometric coefficient, the standard equation of first order reaction time ...
Kashvi's user avatar
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2 votes
2 answers
128 views

Fractional Distillation Question

We're covering fractional distillation in my physical chemistry class. I'm confused regarding this diagram: From your starting point, you heat the binary mixture (in this case benzene and toluene) to ...
GMoss's user avatar
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0 votes
3 answers
94 views

Doubt regarding isothermal reversible process- Thermodynamics

Since its a reversible process, I can say $P_{ext}=P_{int}\pm dP$ so now $W_{int}=\int_{V_1}^{V_2} P_{int}dV$ My question is why can't I assume $P_{ext}=P_{int}$ here and take it as a constant ...
Rexquiem's user avatar
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8 votes
2 answers
584 views

Mulliken Labels: How do I tell apart E, doubly degenerate, symmetry apart from T, triply degenerate, symmetry for a molecular orbital?

With A and B, it's pretty simple. If you rotate the molecule about its principle axis to where the orbitals line up, and the signs change, it's Mulliken label has a B. otherwise, it's A. I heard E ...
AdamT's user avatar
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0 votes
0 answers
84 views

How original is my general matrix formula for rate equations?

I was dissatisfied with the method my teacher taught me to solve rate equations, where you're given experimental values for the concentrations of reactants, and the rate of reaction, which given by $$...
Jamie Cline's user avatar

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