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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In which cases do we use the the reduced mass formula?
Edit: Karsten added a description of reduced mass:
"It is a quantity which allows the two-body problem to be solved as if it were a one-body problem."
I do not really have a strong Physics ...
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Unit of equilibrium constant in formula for Gibbs free energy change at arbitrary temperature
We know the relation for Gibbs free energy change of a reaction at any stage and any temperature
$$\Delta G=\Delta G^{\circ}+RT\ln Q$$
where Q is reaction quotient. Subsequently, we get the rate ...
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If Ethyne has the lowest C-H bond length (highest C-H bond energy) compared to Ethane and Ethene, why is it the most acidic? [duplicate]
I am not an expert in chemistry, but these are the few facts I know from Standard XII chemistry books (these facts could be wrong or incomplete or modified by now).
Facts I know -
Ethane has 'sp$^3$' ...
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Chemistry project on hand warmers: Salt hydrates
Currently I am working on a chemistry project about hand warmers. My goal is to find a salt hydrate which gets warmer than sodium acetate trihydrate and can supercool. I already bought magnesium ...
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Better Way for Crushing Coconut into 500 mesh Coal for Carbonization
I am planning to use coconut as a raw material for carbonization, but I need to crush it into 500 mesh coal. Currently, I am using a mortar and pestle to grind the coconut shell into a fine powder, ...
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Disposal of Aqueous Magnesium Salts
Where can I find out where (specifically) aqueous magnesium chloride and aqueous magnesium bromide can be disposed? I was trying to find out whether solutions could be diluted and washed down the ...
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Calculating percentage of Zn in a coin
Question:
An old coin found in an ancient temple is composed of zinc coated with copper. In an experiment to find the percent zinc in the coin, a student determined the weight of the coin to be 3.0 g. ...
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Ratio between the corresponding force constants of Cl2 and F2
MCQ Question:
Vibrational frequency (f) of a diatomic molecule is given by
where 𝑘 is the force constant and 𝜇 is the reduced mass. For a diatomic molecule (AX), the reduce mass is given by
where �...
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Is there an algebraic form for the textbook reaction coordinate curves?
So here is a curve often used in textbooks to illustrate a reaction coordinate.
It's a nice short-hand device to learn the relationship between kinetic and thermodynamic parameters that control the ...
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Why is C a matrix and not a vector in Roothaan Equations?
I'm trying to figure out why $C$ is a matrix and not a vector in the Roothaan Equations. Below, I have a derivation which I have taken from this PDF in which, to me, $C$ appears to be a vector. But ...
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What are the reactions between Zinc acetate dihydrate and Methoxyethanol? [closed]
I am synthesizing a sol-gel solution with Zinc acetate dihydrate + Methoxyethanol and ethanolamine as stabilizer, and I wonder what are the reactions that are taking place in the process. Could you ...
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Is there experimental evidence to show boiling point increases with external electric field, and if so, by how much?
I was wondering whether anyone has demonstrated that a liquid will have a higher boiling point if it is placed in a very large electric field. I believe to be the case, since induced dipoles would be ...
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Water dissociation constant $K_w$ in vapour, or are there charges entities ($\ce{H3O+}$, $\ce{HO-}$,...) in water vapour?
When water is in vapour state, to which degree is there still some dissociation with the existence of charged species like $\ce{H3O+}$ and $\ce{HO-}$? (I would be interested by any reference to ...
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How can we say that p in ΔU= q_p-pΔV and p in ΔH=ΔU+pΔV are equal? About the derivation of ΔH=q_p
I was studying about thermodynamics and everything was fine until I studied about enthalpy $H$. The first thing I wanna know is what is $p$ in eq. $H=U+pV$. Is it internal pressure or external ...
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Application of Beer-Lambert Law to Absorptivity
The Beer-Lambert law gives a linear relationship between the concentration of a solute $c$ and the absorbance $A$, with absorbance defined as the logarithm of the ratio between the transmitted radiant ...
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Why is work done on the system in irreversible adiabatic compression greater than work done on the system in reversible adiabatic compression?
So, while reading about Quasi- Static process, I came across this question here:
Question about Quasi- static process
From the answers given there, what I understood is this: After irreversible ...
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Outer shell electrons [closed]
I'm trying to find the answers for how many free outer shell electrons that are present in Nickel chloride, I know that nickel has 2 outer shell electrons and chlorine 7.
But nickel chloride is made ...
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Density of dissolved and non-dissolved salts
I am doing a calculation, which needs to be 100% correct. My question is as follows; Does the density of dissolved salt differentiate from the density of non-dissolved salts?
My specific problem is a ...
Martin Sneltvedt
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How do you know if a bond according to VB theory consists of 2 "3 electron bonds" or one "fully paired" bond?
First of all, I want to discuss the whole thing strictly according to the VB - theory and not use any concepts of the MO - theory.
According to Linus Pauling, the "3 electron Bond" is the ...
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How to electroplate vias and THT holes on PCB with copper?
How can I electroplate copper into PCB's vias and THT holes?
I found several instructions, but they all use palladium (which is expensive), or calcium hypophosphite (which I can't get in my country), ...
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Which gas at 15 °C and 1 atmosphere of pressure has the highest refractive index in visible light?
For my own curiosity's sake, I am attempting to find the gas that at 15 °C and 1 atmosphere of pressure in pure form has the highest refractive index on average and overall, for visible light. Assume ...
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Can an oxidising/reducing agent oxidise/reduce itself? [closed]
I am new to the study of this divine science. So Just a query: Can an oxidising/reducing agent oxidise/reduce itself? If it can can anyone give an example and explain it?
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How can I measure the energy contained within water vapor?
Let’s say I have a kilogram of water vapor at $\pu{423 K}$. Can I directly measure the energy, contained as heat, within the vapor? All the laws I know depend on knowing the changes that happened that ...
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Why is the local coupling constant (vibronic coupling) given in eV?
Should the local coupling constant g not be without a unit, as the Holstein Hamiltonian suggests?
$
H=\underbrace{\sum_{P, Q} h_{P Q}^{(0)} a_P^{\dagger} a_Q}_{\text{Fixed geometry}}+\underbrace{\sum_{...
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Volume of a solution in terms of molality, molar mass and density [duplicate]
I found this equation in "Experiments in Physical Chemistry" by Garland, Nibler, Shoemaker. This is on page 174 (Experiment 9).
$$V=\frac{1000+mM_2}{d}$$
where $V$ is the volume of the ...
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Why must the beta term in the rigid-rotator PDE take the form J(J+1)? [duplicate]
Here is the partial differential equation for which the solutions Y are are the wave functions for the rigid-rotator (Equation 5.5 in McQuarrie and Simon's Physical Chemistry).
$$\sin\theta\frac{\...
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Interpretation of Helmholtz energy and Gibbs energy
I know that this question has many other variations on this site, but I'm trying to see if I understood Helmholtz and Gibbs energy properly or not. The material I'm reading from is Physical chemistry ...
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What is the difference between distillation temperature and boiling point?
Is there a difference between the distillation temperature and the boiling point of a fluid, in my case kerosene? And if there is, what is the difference?
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More minerals in seawater at greater depths?
There are lists such as the one below detailing how much of different minerals seawater contains:
https://web.stanford.edu/group/Urchin/mineral.html
(For instance )
Would you expect this to be the ...
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Electron orbitals
Can electrons be found anywhere within the space described by a 3D orbital "90% of the time" (as stated in my textbook)? But that would mean they can be found right next to the nucleus or in ...
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Why does a symmetric stretch mode not have an imaginary frequency?
Currently studying potential energy systems and our professor asked a question at the end of a lecture and I can't wrap my head around it.
He said, "Picture a 2D PES for the simple reaction of H+...
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Why the change of the position of the salt bridge or metal piece leads to different voltage value?
I am doing an experiment where I use salt bridge to create galvanic cell. The goal of my experiment is to find if there is some correlation between the amount of solvent being used and the voltage ...
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Colligative properties and binary phase diagrams
I'm having troubles with colligative properties and how to relate them to binary liquid-vapour and solid-liquid phase diagrams.
First of all, in my book it is indicated that colligative properties are ...
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Confusion about equilibrium constant in simultaneous equilibrium
Ok, so the equilibrium constant in terms of pressure is the ratio of partial pressures at equilibrium of gaseous products to reactants (all raised to the powers equal to the stoichiometric ...
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Diffusion, Migration and Einstein Equation
In the textbook: Electrochemical Systems by Newman and Alyea, 3rd edition, chapter 11.9: Moderately Dilute Solutions, equation for the mole flux of the component $i$ is given by: $$ N_i = - \frac {u_i ...
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Find volume of methanol produced via reaction between carbon monoxide and hydrogen gases
Methanol is manufactured by the reaction of carbon monoxide gas with hydrogen gas. If a $95~\%$ yield is usually obtained, approximately how many liters of hydrogen gas at $\pu{350 °C}$ and $\pu{300 ...
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What processes generate entropy as heat flows across temperature gradient
Suppose, we have a source at high
temperature $T_\mathrm h$ and sink at temperature lower temperature $T_\mathrm l$.
If $Q_\mathrm h$ amount of heat flow from source to sink, then change in entropy of ...
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Claim that the temperature of steam is not the boiling point on a stovetop?
Came across this claim here that "The liquid water is at exactly the boiling point temperature. The water vapor (steam) can be hotter. You can have a thermometer immersed in the water which will ...
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Can we calculate van der Waals' constant a for the following case?
The given Z vs P curve for 1 mole of a gas at 400K starts at Z=1 & P=0.
The slope at the point when the curve again intersect Z=1 is 0.005. The critical temperature of the gas is 500K.
My approach:...
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Question about entropy generated in isothermal expansion of an ideal gas
So, this has been bugging me for a while.
Consider the isothermal expansion of an ideal gas in a container. As the gas is allowed to expand, it does work on the surroundings which causes the ...
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how helium can be compressed if its compressibility factor is alway greater than 1? [closed]
I was studying real gases and found that H2 and He have Z>1, that means they cannot be compressed even at high pressure as their graph is always upwards meaning Z>1 always. Then how come the ...
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Length of a 1D box in hexa-1,3,5-triene
Problem
From Hayward's Quantum Mechanics for Chemists [1, p. 36]
2.3. Calculate the wavelength of light that will be absorbed when
a it electron in hexa-1,3,5-triene, $\ce{CH2=CH—CH=CH—CH=CH2},$ is ...
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Why does FCC crystalline forms form hexagonal crystalline structures during CVD?
During the CVD process, Copper and Nickel which are both Face Centered Cubic crystalline structures are used as substrates for shaping hexagonal atomic structures such as graphene and hexagonal Boron-...
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What is the determining factor between two potential bond candidates? [closed]
Say you have a vacuum (imaginary, of course) with three hydrogen atoms, how do we determine which two will bond and which one will be left out? If the same energy is present (equally) for the entire ...
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Is there a difference between Hartree-Fock method and LCAO?
I have to dive in some quantum chemistry for a quantum machine learning project and I came across the so-called Hartree-Fock method.
In one of the reference I used, they considered electrons as ...
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Equality of partial derivatives (Schwartz’s theorem) and total differential
I'm reviewing some Physical Chemistry concepts and the two books I'm using show the total differential and right away they present the Schwartz's theorem. I don't get the relationship. In the ...
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Reaction rate derivation: amount of substance vs concentration [closed]
Let's say you have the reaction
$$A + B \; \rightarrow \; C.$$
I would like to understand why $\frac{\mathrm{d}[C]}{\mathrm{d}t}$ is proportional to $[A][B]$. I can see why
$$\frac{\mathrm{d}n_C}{\...
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In gas law equations, if volume and temperature are directly proportional, why can't we write the equation as temperature divided by volume? [closed]
In gas law equations, volume, temperature, pressure and amount of substance may vary. In the simpler equations, like Charles' and Amonton's, temperature and pressure/volume are directly proportional. ...
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If liquids absorb heat from their surroundings to become gas, why does gas feel hotter than liquid?
I know what you're thinking, "OP, are you for real!? Gas is obviously hotter because it absorbed heat from the environment!"
But hear me out. Yes it is hotter in absolute terms because it ...
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Difference between pre-equilibrium and steady-state approximation?
Both are reaction mechanisms in which there are several steps and at least one intermediate present. However, I am confused about the differences of both methods, especially when using them to ...
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