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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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1answer
57 views

Is there a better model than the Kinetic Theory of Gases [closed]

I'm looking for a better relationship between the Kinetic energy of a gas and it's Temperature, and also how they vary with gravity (not altitude, just gravity!). So is there a model better than the ...
20
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5answers
2k views

Why do some chemical reactions require many steps?

I posted the following question in Physics SE and was advised to transfer it to Chemistry SE. I studied physics in college ten years ago and I recently started to learn biochemistry. I enjoy finding ...
3
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2answers
149 views

Does activation energy depend on steric factors?

I thought that activation energy depends on steric factors. By Arrhenius equation it must depend on steric factors since $A$ depends on steric factors. $$k=A\cdot\mathrm e^{-\frac{E_\mathrm a}{RT}}$$ (...
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2answers
11 views

Why do some chemical reactions require many steps? [duplicate]

I was a college student of physics ten years ago, and recently started to learn biochemistry. I enjoy finding out that some familiar concepts in physics play important roles in biochemistry such as ...
2
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1answer
45 views

Dependence of mass transfer coefficient on solubility

Does solubility of the solute affect the value of the mass transfer coefficient? The book I am following mentions that the mass transfer coefficient is a characteristic of the constituent and its ...
3
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0answers
89 views

If dG is a state function, why do reversible and irreversible paths differ?

For a reversible process at constant T,P in a closed system with no non-expansion work dG = 0. For an irreversible process under the same conditions, dG < 0. Since dG is a state function I would ...
0
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1answer
56 views

Relative magnitudes of intermolecular forces from phase diagrams

Is it possible to say whether or not a system A or B has stronger intermolecular forces from a phase diagram according to which: The $T_{\text{b}}$ of A is lower than the $T_{\text{b}}$ of B. The $T_{...
5
votes
2answers
144 views

Finite probability from discrete distribution and zero probability from continuous distribution in Maxwell-Boltzmann statistics

I have difficulty understanding a certain concept with the derivation of the Maxwell-Boltzmann distribution $f(v)$ function from Boltzmann statistics. The derivation starts with the Boltzmann ...
5
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1answer
462 views

What do 1T and 2H mean in front of compounds?

I have seen 1T and 2H used as prefixes for metallic compounds in literature, but I am having trouble finding what they mean. For example, 1T-HfS2 or 2H-HfS2.
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1answer
54 views

Chemical Kinetics- Net Number of Particles

I have a box of 5 types of particles, $A$, $B$, $C$, $x$ and $y$. They react in the following way. $\ce{$A$ + $B$ -> $C$ + $x$}$ and $\ce{$C$ + $y$ -> $A$ + $B$}$ If only the first reaction ...
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0answers
34 views

Total pressure conservation during equilibrium reaction

I tried to solve the following exercise but my solution is different from the one of the book and I can't understand why. The exercise is the following: With total pressure $$p_\text{tot}=\pu{0.5 ...
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0answers
27 views

How many components and phases are in an equilibrium system comprising lead sulfate, lead ions, and sulfate ions?

I am going to calculate the degrees of freedom ($F = C-P+2$) on the following system, but I can't figure out whether we have to take $\ce{PbSO4}$, $\ce{Pb^2+}$ and $\ce{SO4^2-}$ as a single component ...
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1answer
65 views

Why nature favours lower potential energy? [closed]

It is very abstract but I was asked this question recently and unfortunately I was not able to answer it decently enough. I've seen it coming up in various forums of physics, chemistry or biology. ...
1
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4answers
600 views

Raoult's law & Dalton's law of partial pressures

I am confused between Raoult's law and Dalton's law of partial pressure as they state completely different things about same thing... Raoult's law claims $p = P \cdot x$ where $p$ is the partial ...
8
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4answers
402 views

Why does the Leidenfrost effect (seemingly) not apply to the case of molten NaCl when it is poured into water?

On pouring molten sodium chloride into water you can see that when molten $\ce{NaCl}$ (table salt, i.e. sodium chloride) is poured into water ($\ce{H2O}$), the Leidenfrost effect appears to be ...
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1answer
93 views

Chemistry - Solutions

Please give me a few hints as to how I can approach this problem A mixture of two miscible volatile ideal liquids P and Q (obeying Raoult’s law) is kept in a vessel (molar ratio of P and Q in the ...
12
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3answers
522 views

Derivation of Maxwell–Boltzmann statistics

I have 2 questions regarding the derivation of the formula which calculates the probability of molecules having a particular amount of kinetic energy $E_x$ in a system of $N$ molecules. It states that:...
0
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1answer
46 views

Capillary action only works with glass tubes?

I tried to reproduce the capillary action and measure how high the water rises. So far, I've tried unsuccessfully with a regular drinking straw and a very narrow plastic tube with an internal diameter ...
6
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1answer
655 views

Why is dp/dv zero for a real gas in critical conditions?

I have read this fact in various websites but cannot understand the reason. What is an intuitive explanation of this?
2
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0answers
88 views

Generalized reaction rate and derivation

Most textbooks give the reaction rate $$r = k C_\ce{A}^a C_\ce{B}^b \tag{1}$$ for the elementary process $\ce{a A + b B -> P}$. However, expression (1) is not valid in the general case: e.g. it ...
0
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0answers
79 views

How to find out which plane in a cubic structure has the highest density?

For a cubic structure (namely FCC, BCC, or simple cubic) we can always draw a plane and predict the plane which has highest density of atoms. Is there any rule of thumb to arrive at such a plane? How ...
2
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1answer
112 views

Modeling Belousov-Zhabotinsky reaction using ordinary differential equations

Is it possible to model the BZ reaction using first order ODEs? If so what would these equations be? Or, is there something about the reaction that needs higher orders?
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1answer
39 views

Turning Soda Glass into Lead Glass and Fused Silica [closed]

What would be the method of turning Soda Lime Glass into: A. Lead Glass B. Fused Silica Soda Lime Glass is $\ce{SiO2}$ ~70%. Lead Glass is $\ce{SiO2}$ ~ 62.9%. Fused Silica is $\ce{SiO2}$ ~ ...
1
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1answer
92 views

Equation to find specific gravity (or density) from a solution of sugar and water

Is there an equation or simple way to calculate the final density of a solution made from x grams of sugar and y liters of water? And would it work in reverse? if we have y liters of water at z ...
1
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1answer
51 views

Is it possible to prevent agglomeration and sedimentation of microparticles just by increasing the viscosity of the medium?

I am considering a suspension of a fine powder in a high-viscosity liquid. The suspension shall be stable over long time scales, i.e. the particles only move a few mm per year, and I have the ...
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0answers
66 views

Rutherford's alpha particle scattering experiment for sheets made of different metals [closed]

The correct order of increasing number of alpha particles passing undeflected through the foils of Au, Ag, Cu and Al of 1000 atoms thickness each in an alpha scattering experiment of Rutherford would ...
1
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0answers
27 views

Stat Mech: Maxwell-Boltzmann Distribution of Momenta

I'm trying to show that the MB distribution of scalar momentum that I've found is properly normalized but I'm stuck. My process: I started with the MB distribution of momentum in 2D and found the ...
0
votes
1answer
61 views

What happens to the gas inside cold drinks as the cold drink is frozen?

According to Henry's law the amount of gas dissolved is directly proportional to the pressure exerted by a gas on the surface of the liquid. And we know if we increase the temperature, the amount of ...
1
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1answer
201 views

Equilibrium constant Kp for vaporization of water?

For the reaction H2O(l) -->H2O(g) it is given that Kp = p(H₂O(g))/p° where p° is the atmospheric pressure. Why is it not just equal to p(H₂O(g))?
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1answer
59 views

Does the probability function for a molecule to have energy in a certain mode depend on the minimum required quantum energy level of that mode?

I understand that the probability density for a particular velocity v+dv in one dimension for a molecule in a system is: $$f(v) = \sqrt{\frac{m}{2\pi k_B T}} \cdot e^{\frac{-mv^2}{2k_B T}}$$ I'm ...
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1answer
307 views

Calculate Heat of Atomisation [closed]

What is heat of atomisation of P4O6(s) Given heat of sublimation of P4O6 is x kJ/mol & P–O bond energy is y kJ/mol. What is heat of atomisation of P4O6(s) Given heat of sublimation of P4O6 is x ...
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1answer
62 views

How to correctly mix solutions?

Imagine you have two ingredients - 45 grams of 60% ethanol, and as much water as you wish. The only accurate tool you have is a scale, which measuring error is up to $\pm \pu{1gram}$. How would you ...
0
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0answers
35 views

A problem on Gas bubble column

It is known sulphite to sulhate oxidation can be achieved by using H2O2 or oxygen as oxidising agent. If we flow a liquid mixture of sulphite with H2O2 along with air bubble through the solution in a ...
1
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3answers
2k views

Work done in an isothermal irreversible process

In calculating the work done in an isothermal irreversible process, why do we consider the external pressure only (using formula: $W_{\text{ext}} = P_{\text{ext}} \mathrm{d}V)$ but not the internal ...
3
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0answers
39 views

Reverse rate coefficient for thermolecular and thermal dissociation reactions

I am an astrophysicist working in exoplanetary atmosphere chemistry right now, in particular modelling the chemical kinetics taking place within the atmosphere. Based on this IOP article, we have that ...
0
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1answer
35 views

Can air inside a high temperature (1300C) Kiln cause an explosion?

I saw many kiln designs that lack an opening for hot\pressurized air to come out , or any pressure valve. But when air is heated to such a high temperature (1300C) inside a closed chamber (the kiln), ...
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1answer
46 views

More effective fire extinguisher liquid than water

I join robot fire fighting contest. One of the mission is to extinguish candle by spraying it with liquid (water is default option). For spray mechanism I use pump with Venturi effect principle. Is ...
4
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0answers
139 views

Atkins' Physical Chemistry 10th edition Question on steady-state approximation

Please help me with Example 20E.2 of Atkins' Physical Chemistry 10th edition textbook on using the steady-state approximation. I have attached my attempt but am just not sure how to get to the final ...
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0answers
72 views

Barking dog reaction mechanism

Liebig's blue devil or the "barking dog" reaction is the gas phase oxidation of carbon disulfide with either nitrous oxide or nitric oxide. What are the gas phase reaction steps in this reaction, I ...
5
votes
1answer
53 views

Test for a dipolar compound?

Just surface level here, if I had two compounds and wanted to know which one was dipolar, could I just add them to water? If so, would the dipolar substance dissolve while the other compound is ...
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1answer
58 views

Hybridisation in Molecular Orbital Theory

How loosely can the term hybridisation be incorporated while constructing molecular orbitals? Does hybridisation hold any significance when looking at molecules through the Molecular Orbital Theory?
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1answer
377 views

Why does 1 mol. of any gas at STP occupy only 22.4L Volume when it should occupy the volume of entire container in which it is kept? [duplicate]

Let us say we have a container of 100L capacity and a gas inside it is kept at STP. According to the law the gas should occupy only 22.4L of volume but shouldn't the gas occupy the entire volume of ...
0
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0answers
51 views

Formation of both bonding and anti-bonding orbital

For the formation of molecular orbitals, you get both a bonding and an antibonding orbital. I don't understand how both can happen. For example with combining p orbitals, to make a bonding orbital you ...
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0answers
20 views

Capillary forces in horizontal plane

In a physical chemistry course, we went to the lab and made a microstamp out of an elastomer. This stamp has gaps of 25 µm in width. When the elastomer had hardened, we placed it on a microscope slide ...
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1answer
30 views

Find amount of benzoic acid in dissolution

Solubility of benzoic acid in water at $\pu{0^\circ C}$ is $\pu{1.7 g/L}$ and given the fact that $\pu{37 mL}$ was used to dissolve $\pu{1 g}$ of benzoic acid. How much of the benzoic acid would be ...
3
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3answers
2k views

Is there always a limiting reagent in every equation?

Is there always a limiting reagent in every equation? For instance, is there a limiting reagent in $\ce{CaCl2 + Na2CO3 -> 2NaCl + CaCO3}$ where the same number of moles are reacting with each ...
0
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1answer
288 views

Why is the difference between the melting point and boiling point large for some compounds, and small for others? [duplicate]

I was looking at a list of melting and boiling points of various compounds and I realised some had very large differences while some have very less differences between their melting and boiling points....
2
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1answer
130 views

Obtaining values for electrical mobility from ion transport numbers in a Hittorf cell

I am following the experiments detailed in the links below in order to find the electrical mobility of a variety of ionic species: Wikipedia article on ion transport numbers and Hittorf method PHYWE ...
2
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1answer
66 views

Could a strong acid become a strong base? [closed]

Is it technically possible for a strong acid to change into a strong base, through a chemical reaction? Example: if an acid with pH 1 became a base with pH 12.
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0answers
326 views

Why Gallium has less atomic radius than Aluminium but Thallium has more atomic radius than Indium? [duplicate]

All four elements mentioned here belong to the 13th group, where they follow the order- Al, Ga, In, Tl. Gallium's atomic size is less than that of Aluminium, because of the poor shielding effect of ...