# 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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### How can the potential energy at the infinite energy level in an atom be zero?

I have recently learnt about atomic structure and the Bohr model of the atom and have observed a discrepancy between it and my previous knowledge based on physics. For simplicity, assume the atom is ...
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### Free induction decay in NMR (as stated in Pavia)

There is a statement in a very popular textbook of spectroscopy by Pavia (Chapter 3, Intro. to Spectroscopy), it says "The observed FID is actually an interference signal between the radiofrequency ...
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### Isobaric-isothermal ensemble with degeneracy

I've been studying statistical mechanics for a while, the topic is very far from what I've learned till now so my questions may be superficial. When trying to see what my entropy is in an isobaric-...
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### Calculating Air Density and Effect of Air Composition

I have to calculate density of atmosphere, assuming that it is: 79% : N2 21% : O2 Does the percentage of gases affect the answer, and how can we find the density with such little information?
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### Enthalpy change of gas expansion against constant external pressure

A certain mass of gas is expanded from $\pu{1 L}$ at $\pu{10 atm}$ to $\pu{4L}$ at $\pu{5 atm}$ against a constant external pressure of $\pu{1 atm}$. If initial temperature of gas is $\pu{300 K}$ and ...
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### How is it that I could obtain endothermic Temperature ~ Time plots for a calculated Exothermic Enthalpy of Solution?

I recently conducted a coffee-cup calorimetry experiment in which we attempted to measure if the dissolution of inorganic crystals such as LiCl, NaCl, and SrCl were endothermic or exothermic based on ...
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### What material can be used as scraper in a chemical reactor?

I am having a 10L reactor built using SS316 for Plastic Pyrolysis. TEMPERATURE : 550C I would like a scraper to clean the char that forms on the reactor's inner layer. Teflon scraper is available ...
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### Relationship between Yield and Applied Potentials

This question revolves around this question from Atkins' Chemical Principles 5th ed., Chapter 13, Question 13.116: Consider the electroplating of a metal $+1$ cation from a solution of unknown ...
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### Conductivity variation on Caustic (NaOH) Dilution System

I am reading the drawing for an automatic caustic dilution system where 50% NaOH is diluted down to 20%. I was expecting to see a density sensor on the outlet to provide feedback to the dilution ...
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### Change in Free Energy in Gas Reaction

I try to estimate whether particles form pairs or not. What I know is the difference in the potential Energy $\Delta U_\mathrm{pot}$ which occurs when both particles form a pair. When I have a ...
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### Inverse use of a reverse osmosis membrane

I've got a question regarding Osmosis. I recently came across 'Thin-film composite membranes'. Those are build up of layers with one of those being semipermeable. As I'm not well versed in chemistry, ...
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### ammonia, methylammonia, dimethylammonia, trimethylammonia reactions

Perhaps a "basic" question (pun intended), but I have a few questions about the reactivity of ammonia and its methylated cousins. I come from an engineering background, essentially I use a process in ...
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### Is there any mathematical formula for electron affinity and ionization potential?

I already know about the mathematical formula for electronegativity, but it requires the ionization potential and electron affinity. How can I can easily calculate the ionization potential and ...
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### Do gases behave ideally near the critical temperature?

In class, my TA said the closer the temperature of a gas is to the critical temperature, the more ideal it is. I'm struggling to understand this, as I thought more ideal behavior occurs at high ...
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### Thermochemical data of methanol

I am trying to find the standard entropy and enthalpy of methanol as functions of temperature, but they are not available on the NIST-JANAF tables: http://kinetics.nist.gov/janaf/ Does anyone know ...
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