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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Explanation and terminology of a phenomenon [closed]

Please observe the picture given- I want to know what exactly is this phenomenon and what exactly is causing it. Context - an organic solution (WD40) is spilt on a wet surface outside, light bouncing ...
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Why is the Gibbs free energy of titanium(IV) chloride reduction to titanium metal positive?

I use the Ellingham diagram to find the Gibbs free energy at the equilibrium state to find the partial pressure of chlorine. I have to use the Van 't Hoff reaction isotherm and the partial pressure of ...
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Charge acquired by sols after their preparation

This table from my textbook (p. 20), shows nature of charge on particles of listed sols, in their original or natural form. What reasons can be attributed to these observations? Positively charged ...
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The rate of the reaction [closed]

Recently I look into some reaction for Vinyl Chloride Monomer. I would like to know why the rate of 1,2dichloroethane dehydrochlorination under the conditions of ethylene oxychlorination is described ...
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Solubility and solubility product in relation to the number of ions in a formula

I was taught that if a salt was formed by ions with higher charges, the lattice energy would be also higher (Born-Landé), and the solubility in water would be lower, as it takes more energy to break ...
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How to calculate fugacity

How does one calculate the fugacity in a level 1 fugacity model? If we already know the fugacity capacities and volumes of the different environmental compartments, and the total amount of the ...
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Improving accuracy of water lead test

Home water tests for lead have an accuracy of about 15 ppb. If I first do a gentle/slow boil for one hour (hot plate under a glass beaker of water) to reduce 2000 mL to 20 mL, will I then effectively ...
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Can the number of moles be a ratio of mass percentage and molecular mass? [closed]

I recently started studying mole concept and came across this formula, $$ n=\frac{\text{mass percentage}}{\text{molecular mass}}$$ I don't know how it came into existence. How does this formula work?
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What Chemicals to Reduce, Remove or Substitute to Make My Dry-erase marker ink Clean well after It has Dried

Can someone please help me with the best formula for the production of dry-erase marker ink that can be completely cleaned after a day of writing on the whiteboard? Here's my formulation: 1.Ethanol ...
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Calculating pH of a solution of benzoic acid and NaOH [closed]

Calculate the final pH of the solution when $\pu{17.5 cm3}$ of $\pu{2 M}$ benzoic acid reacts with $\pu{25 cm3}$ of a $\pu{1 M}$ standard $\ce{NaOH}$ I found the number of moles of benzoic acid to be ...
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1 answer
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Pressure vs. Size of Particles [closed]

If two containers with different sized particles are held at the same temperature, which gas will exert more pressure?
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What happens if a black body object is better at absorbing than emitting radiation? [closed]

I know that if a black body object is a perfect absorber and a perfect emitter than it will give out the same energy it receives. However, what happens if it's better at absorbing than emitting?
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Relation between activation and threshold energies

Activation energy $E_\mathrm{a}$ and threshold energy $E_0$ appear to be equivalent quantities: In particle physics, the threshold energy for production of a particle is the minimum kinetic energy a ...
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GLP mass to volume conversion problem (Rotary Meter)

this is my first post here on this forum. I would like to share a question that is bothering me: I have a gas powered system. I would like to measure the total gas consumption in ...
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Determine the sea level specific weights of liquids in lbf/ft 3 having densities of : a. 1.75 slug/ft 3 b. 62.6 lbm/ft 3 with g = 32.2 ft/ sec 2 [closed]

Determine the sea level specific weights of liquids in pound force/ft^3 having densities of : a. 1.75 slug/ft^3 b. 62.6 pound mass/ft^3 with g = 32.2 ft/ sec^2
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Is Bohr Postulate Of Angular Momentum Wrong? [closed]

i just get to know about two formulas $$\sqrt{l(l+1)}\frac{h}{2\pi}$$ and $$mvr = n\frac{h}{2\pi}$$ where mvr is the angular momentum... let's say I talk about s subshell where l=0 its angular ...
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Stability of Al Vs. stability its ions [closed]

We were studying ionisation energy in class and so I learnt that: I.E1 Of Al(~580j/mol) < I.E2 of Al(~1815j/mol) < I.E3 of Al(~2740j/mol) <I.E4 of Al(~11600j/mol) I can see that it requires ...
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What is the difference between a single displacement reaction and a two competing reaction system?

For example, consider the single-displacement reaction $$\ce{AB + C <=> BC + A}$$ My question is then if writing this reaction as the system \begin{gather} \ce{AB <=> A + B} \\ \ce{B + C &...
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How do I interpret the dissolution rate unit? [closed]

I have found a paper (link) that is interesting for my research project. The dissolution rate unit in this paper is described as $\pu{mol/cm^2/s}$. For my project I would need the dissolution speed ...
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How do I calculate q/m? [closed]

My chemistry book (Mortimer in German) has the following question: Calculate the value q/m for the following Ions: ("mit Masse" meaning "with mass") How do I calculate q/m? Thanks ...
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1 answer
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Can we calculate final temperature of two gases in thermal contact? [closed]

This is a question from IIT-JEE - ADVANCE 2018 A closed tank has two compartments A and B, both filled with oxygen (assumed to be ideal gas). The partition separating the two compartments is fixed ...
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2 answers
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How does carbon dioxide in the atmosphere keep heat trapped?

In the classic description of how greenhouses gases are increasing the temperature of Earth's surface, shorter wavelengths of light like visible and ultraviolet (UV) penetrate the atmosphere, hit the ...
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2 answers
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Molecular orbital mixing in second period elements

Why do the $\pi_u(2p)$ and $\sigma_g(2p)$ diatomic MO mix within the second period elements as it's shown in the image below?
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Why do we subtract the volume correction term in the van der Waals gas equation [duplicate]

The following equation is valid for ideal gasses $$pV=nRT$$ Please mind the following notation, any parameter that is related to an ideal gas would be denoted with a subscript $i$ and anything related ...
7 votes
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Bonding in hypervalent molecules

I don't know where they go the electrons of the extended-valence in molecules like $\ce{SF6}$ or $\ce{PCl5}$ for instance, because my teacher said that the d orbitals can't interact with s and p (or ...
1 vote
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How do I calculate enthalpy change calculations questions?

Below is a question I'm struggling with. When $\pu{0.1 mol}$ of aqueous potassium hydroxide was added to $\pu{0.1 mol}$ of nitric acid, $\pu{5200 J}$ were transferred to the surroundings. What is the ...
8 votes
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Schlögl model - Stationary States far from Equilibrium

The Schlögl model can be represented as follows: $$ A + 2X \underset{k_2}{\stackrel{k_1}{\rightleftharpoons}} 3X \, , \\ X \underset{k_4}{\stackrel{k_3}{\rightleftharpoons}} B \, . $$ The chemical ...
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Molecular collisions in an ideal gas

(The equation of ideal gas is $pV=NRT$. If p = 1 atm, N = 1 mole, T = 0°K, and R = gas constant, then volume = V = zero. Hence, the volume of an individual molecule of ideal gas is zero). An ...
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Can chemical potential be directly measured like this?

I have a system of a pure ideal gas $a$, which I call 'the reference', with a known $P^{ref}, V^{ref}, T^{ref}$ and $n^{ref}_a$. I know the chemical potential formula for an ideal gas, so can ...
2 votes
1 answer
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Why does Hartree-Fock overestimate the energy gap?

Everybody knows that Hartree-fock overestimates the energy or band gap, but it is difficult to have a clear explanation of the origin of this large deviation from the experimental values. I know that ...
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Overheated Teflon plumbing tape and pipe dope

I had to solder connection in a water tank, near a fitting that had Teflon tape applied and Kevlar pipe dope. My understanding is that Teflon brakes down above 500F Once the fumes are gone the any ...
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What is the state of matter of a substance if the melting point or boiling point of a substance is exactly at room temperature(25 degree Celsius)?

A substance can exist both in solid and liquid state at melting point, and A substance can exist both in liquid or gaseous state at boiling point. In the above image the state of matter is ...
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How to make clean water from urine in a wastewater treatment plant? [closed]

Referring to a video here, describing a filter that treats wastewater, wouldn't urine in the wastewater not get filtered out because a sand filter alone does not separate urine from water? How is ...
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Can the charges at the ends of a dipole in a polar molecule exceed unit electronic charge?

According to my current understanding, charges at the end of the dipole of a polar molecule are formed due to the shifting of the electron cloud towards the more electronegative atom. In my book it is ...
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Adiabatic Venting of Propane Tank

A few weeks ago, a question was submitted regarding adiabatic venting of a chlorine cylinder: Issues with Chlorine Liquefaction The member submitting the question was interested in why the stream ...
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1 answer
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Oscillating vs Autocatalytic reactions

Are all oscillating reactions autocatalytic? Or are all autocatalytic reactions oscillating? What's the relation between them? Am I just mixing up different things or are they basically the same? For ...
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Exception to the order reaction and stoichiometric coefficient equality in elementary reactions

When a reaction is elementary,the stoichiometric coefficients always equal the order for each reactant? Is there any exception? Because at Ángel González Ureña's Cinética Química it says that this is &...
4 votes
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Half-life vs. relaxation time vs. average lifetime

On page 25 of Ángel González Ureña's Cinética química (2001), appear the terms half-life time (of an intermediate) and relaxation time, but it refers to both of them with the letter $\tau$. Why is ...
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Why can't the half-life be determined in a reaction with more than one reactant?

We have a second order irreversible reaction with 2 reactants (A and B, order 1 for both) so that the initial concentrations are different. I've read that the half-life doesn't make sense in this ...
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How do we know that rates depend on the product and not the sum of reactant concentrations [closed]

I've been struggling to understand the mathematics behind the calculation in enzyme kinetics within systems biology at an intuitive level. Every research article and textbook says it is based on the ...
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How does pressure affect the color of reaction medium with equimolar amounts or reactants and products at equilibrium?

Chlorine gas is pale yellow-green, and both hydrogen and hydrogen chloride are colorless gases. According to the Le Chatelier's principle, the change in pressure will not affect the following ...
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Why the electronic configuration of samarium is ending with 4f⁶6s²

What is coming in my mind is that 4f^7 6s^1 should be more stable as it allows two orbitals to be half filled rather than 4f^6 6s^2 in which only one orbital is completely filled....can someone please ...
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Differential equation in consecutive reactions

I'm blocked in a step of getting to the equation $(7)$, more precisely in the step between $(5)$ and $(6)$. I show my way to solve it down, but I don't get the same as $(6)$, so I wanted to know if I ...
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Surface-Plasma Interaction Education Guidance

I work in a field where understanding interactions between plasmas and metals for the purpose of generating a particular reaction is important. However, I know very little about plasma assisted ...
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Photoelectric effect: What happens when you irradiate the metal strip with a wave of frequency exactly equal to threshold frequency of the metal?

My teacher said that if we irradiate the metal strip (used in generating the photoelectric effect) with light having frequency equal to the metal's threshold frequency, then the electrons will have ...
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Iodine clock reaction: lower temperature but faster result?

I was told by several high school students that they experienced odd results in their iodine clock reaction lab. They did several different trials, and the lower the temperature, the faster the blue ...
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Why is it impossible to determine number of visible emission spectrum of He+

We know that atoms emit spectral lines on excitation and de excitation. I was doing one high school question based on this theory Number of visible lines when an electron returns from 5th orbit upto ...
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Negative or fractional order of reaction

Let $\ce{A}$ be the reactant and $\ce{P}$ the product at the imaginary elementary reaction $\ce{A->P}$. Could it possibly have a net total order of $-1?$ $$-\frac{\mathrm d[\ce{A}]}{\mathrm dt} = k[...
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How does adding oxalic acid to water change the volume of the solution?

Does $\pu{87.4 mL}$ of $\ce{H2O}$ and $\pu{12.6 g}$ of $\ce{HOOC-COOH.2H2O}$ create $\pu{100 mL}$ of a solution? So in our practical class our teacher wanted to make $\pu{100 mL}$ $\pu{1 M}$ aqueous ...
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What do the positive and negative signs on the atomic orbitals diagram imply? [closed]

I was reading up on wave functions and electrons behaving like a wave when they are bound in an atom. In the orbital diagram, the + and - signs don't make any sense to me, and the reasoning that one ...
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