# 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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### Why is the value of $A$, in the expression for Boltzmann's distribution of speeds, not directly calculated?

I've read the proof for the expression for Boltzmann's distribution of speeds on this site. There, $f(v)$ is first factorized into $f(v_x)$, $f(v_y)$ and $f(v_z)$ and $A$ into $A_x$, $A_y$ and $A_z$. ...
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### Products formed on the electrolysis of wet HF

We know that, electroysis of water produces $\ce{O2}$ at anode and $\ce{H2}$ at cathode. In a similar way I thought that on electroysis of $\ce{HF}$ it would produce $\ce{F2}$ and $\ce{H2}$ at their ...
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### How to calculate the temperature of a mix?

I'm trying to solve a problem but there is something im not quite getting. It says, if we mix 84.2 mL liquid water at a 15°C and 50 mL of 100% sulfuric acid at 25°C, What is the maximum temperature ...
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### How can the reaction heat be ignored in an energy balance?

I have received from my professor the following (here summarized) problem: A first-order exothermic reaction A->B takes place in a tubular reactor (typical PFR). The tube is cooled to a constant ...
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### Calculating the Hopping distance in K+ F- bonds

[![enter image description here][1]][1] This is a graph showing the formation of K+ F- ionic bonds. To my understanding, when the atoms are far apart, their neutral state is more stable. But when they ...
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### Definition of Molecularity of a reaction? [closed]

If nucleophilic attack occurs simultaneously at two seperate electrophilic sites of the molecule following SN2 at each site, will the moleculularity still be 2? Does molecularity depend on the total ...
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2 answers
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### Why can't there be a gas-dispersed-in-gas colloid? [closed]

Colloids, a special type of heterogeneous mixtures, typically have two components. One is the dispersed phase (DP), which is the "solute-like" part and another one is the dispersion medium (...
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### If there are two possible reactions, will the one with a more negative Gibbs Free Energy be favored?

I was thinking of the reaction between methanol (CH3OH) and sodium amide (NaNH2) and wondering if I could get methylamine (CH3NH2) from it. One reaction forms methylamine and sodium hydroxide, while ...
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### Analytical Prediction of Molecular Interactions [duplicate]

Is it possible to predict the molecular interaction between any two molecules analytically or through some simulation mechanism based upon analytical theory? I see a rather big gap between, say ...
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1 answer
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### Relation between Solubility Product and Equilibrium Constant

I had read about Solubility, and I found that Solubility is not Molarity (because previously I believe that both are same thing). But, they have a big difference (source : https://en.wikipedia.org/...
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1 answer
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### Fractional Composition of Acid Question

I present to you a fractional composition question that my professor refuses to answer because he encourages me to use equations without understanding them. Any help you can provide would be very, ...
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### For the same substance, which are stronger, the bonds in the solid or the bonds in the liquid?

As a teacher, I show students the particle model as an explanation of solids, liquids and gases, and changes of state. I did this today, explaining that the bonds in the solid break because the ...
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1 answer
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### Standard Gibbs free energy when all the reactants and products are at standard condition

I have read in my textbook that for a reaction $\Delta G=\Delta G^o-RT\ln Q$, where $\Delta G^o$ is the Gibbs free energy change when the initial concentration of products and reactants are unity. ...
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### How do thermodynamic variables behave in reversible and irreversible processes?

I read this definition: reversible process is one which can be stopped at any stage and reversed so that the system and surroundings are exactly restored to their initial states. An irreversible ...
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### How to find the wave equation in a 1D box with a 2 different V(x) values

So this is for a simple infinite well $1$D box. The bounds are defined as $V(x)=0$, for $0<x<\frac{L}{2}$, and $V(x)=V_0$ for $\frac{L}{2}<x<L$ with everywhere in the box having a ...
1 vote
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### How does 25% CO2/75% Ar welding gas exist?

What state does a 25% $\ce{CO2}$ / 75% $\ce{Ar}$ mixture exist in under high pressure? This mixture is a common welding shielding gas. I'm not sure if manufacturers are referring to this mixture by ...
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2 votes
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### Relation between concentration and activation energy

Will increasing the concentration of the reactants in a chemical reaction increase the proportion of molecules with an energy greater than the activation energy $E_\mathrm{a}$? It seems to me that the ...
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### How do we find hybridization when molecule has resonance?

Consider the following image which shows the resonance structures of $\ce{CO_3^{2-}}$ ion. What is the hybridization of $\ce{O}$? How do we proceed in such cases? In one resonance structure, the top ...
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### Rate equation for the decomposition of hydrogen peroxide with iron(III) chloride as catalyst [duplicate]

I am trying to determine the activation energy of the decomposition of hydrogen peroxide with iron(III) chloride added as a catalyst. To do that, I need to find the rate constant, but I am not sure ...
-1 votes
1 answer
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### Viscosity and repulsive forces

Suppose we let a ball move in a fluid with initial velocity $u_i$. Then as time goes on its velocity goes down and tends to $0$ after infinite time. I understand viscosity in the following way: In ...
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