Questions tagged [physical-chemistry]

Study of macroscopic and microscopic phenomena in chemical systems in terms of physical laws and concepts [thermodynamics, statistical mechanics, kinetic theory, quantum mechanics...].

Filter by
Sorted by
Tagged with
3
votes
1answer
51 views

Stability of Chemical Reactions

Given the following reactions: $$A + X \xrightarrow{k_{1}} 2 X$$ $$Y + X \xrightarrow{k_{2}} 2 Y$$ $$Y \xrightarrow{k_{3}} B$$ I was able to write the following rate equations for the concentrations: $...
0
votes
0answers
11 views

Learning resources for Physics, Physical Chemistry and Chemistry like mathworld? [closed]

What are similarly extensive (the most extensive) web resources like https://mathworld.wolfram.com/ for maths, but for physics, chemistry (and maybe physical chemistry)?
0
votes
1answer
37 views

Why octet atom are stable? And what make atom unstable?

I have search a lot that want make octet atom stable but all I found is that it need to fill the orbit! why . Why it need to fill the orbit. And I also search that why atom which don't have octet are ...
1
vote
1answer
25 views

Covalent bond between two hydrogen atoms with the same electron spin?

According to Pauli's principle, two electrons in an orbital cannot have the same spin. Does this mean, for example, that two hydrogen atoms, each with one electron, will not covalently bond to H2 if ...
0
votes
1answer
31 views

Can sound be used to identify a molecule?

A few notes to this: Can a molecule have a particular "response" to sound? I understand that soundwaves arise from the synchronisation of millions of particles but assuming such a fine ...
0
votes
0answers
11 views

Fourier transform of normal vector on undulating surface

I am trying to obtain a relationship between the Fourier transform $\textbf{n}(\textbf{q})$ of a 3D normal vector $\textbf{n}(\textbf{r})$ and this normal vector itself on an undulating 2D surface ...
0
votes
1answer
54 views

Definition of angle as a difference between two derivatives

In the physical chemistry paper De Gennes and Taupin - Microemulsions and the flexibility of oil/water interfaces, at some point the following definition of a squared angle is given (referred to as &...
1
vote
0answers
26 views

Free Energy in Cahn-Hilliard Equation

i have got a question regarding the derivation of the Cahn-Hilliard equation. I am espacially referring to the following paper: https://aip.scitation.org/doi/10.1063/1.1695731 In this paper he defines ...
0
votes
0answers
13 views

Calculating Enthalpy of formation versus Calculating Enthalpy of a reaction not occurring at standard conditions

My understanding of Hess's law and its use in determining the change of enthalpy of a reaction has been challenged recently. Up until recently, I thought that the only way to calculate a chemical ...
0
votes
1answer
28 views

Why does a gunpowder makes sound when it burns but not like a candle?

My class teacher asked this question, when a fire-cracker ( which has gunpowder in it) burns, it explodes and make a sound while when a candle is burnt it doesn't, and I also want to know why does ...
0
votes
2answers
64 views

Why light comes from fire?

We know that light is produced when a charge particle accelerate. Fire doesn't have electric and magnetic field so how do light comes from fire
3
votes
1answer
51 views

What steps are exact in Born-Oppenheimer and adiabatic approximation?

I am reading about adiabatic and Born-Oppenheimer approximation and I can't understand what steps are exact and what steps are approximations. Both these approximations are based on the idea that as ...
0
votes
1answer
55 views

What is the allowed $k$ values in nearly free electron model?

One explanation on bandgap formation uses nearly free electron theory and Bragg reflection. The diagram used for the explanation appears: taken from here. I also learnt that in free electron theory, ...
4
votes
2answers
141 views

Can you superheat coffee?

As far as I know, heating clean water can lead to superheating to over 100 degrees but how clean does it have to be? Coffee is almost all water but is it clean enough to lead to superheating? What ...
2
votes
1answer
77 views

Persistence length by De Gennes: how to make sense of the definitional equation?

I want to understand how De Gennes comes up with the concept of persistence length in microemulsions, and in particular a convenient equation that relates this persistence length to the thickness of ...
0
votes
1answer
52 views

How does salt lowers the freezing point of water?

At 0 degree Celsius, water molecules slow down enough to bond with each other and ice starts to form. By adding more salt or sodium chloride the freezing point of water becomes even lower, why is that?...
1
vote
1answer
15 views

Spectroscopy of mixed material

If there is an unknown sample $X$ consisting of various molecules, is there a general method to determine the molecules making up the sample using spectroscopy? Details. This is my naive guess on how ...
2
votes
1answer
150 views

What causes the "screaming" sound from sausages when cooking them?

I saw this Youtube clip and wondered what's causing the screaming sounds? https://www.youtube.com/watch?v=2Qz_8zxEGho&ab_channel=perhoskoira Something to do with the cooking oil and how it reacts ...
2
votes
1answer
31 views

Absorption spectroscopy - transmittance (normalized)

In the absorption spectroscopy we can calculate transmittance $T$ of a given sample by comparing how the intensity of the incident beam $I_{0}$ is decreased with the distance (Lambert-Beer Law). $A = -...
2
votes
2answers
101 views

Do noble gases attract each other?

When 2 atoms come close enough, the nucleus and the electron cloud attract each other, the electron clouds are pulled between the the nuclei's until an equilibrium distance is reached. Why doesn't ...
-1
votes
1answer
26 views

Is it possible to make methane visible?

:) It is just a curiosity question. Under the right conditions, I could clearly see a shadow of warm/cold air. But methane won't create any such shadows. Is there any tool/method that I could use to ...
0
votes
2answers
37 views

Differences in Diamond and Polyethylene despite both having carbon atoms?

Diamond and Polyethylene both have Carbon atoms joined by strong covalent bonds. But their properties are different, with Diamond being very hard and has a high melting temperature, and Polyethylene ...
-1
votes
3answers
80 views

Why is the burning temperature of different species of wood so different? [closed]

If you have read Farenheit 451, you may have the idea that paper (or perhaps wood in general) burns at 451F. However, in fact, different species of wood burn at widely different temperatures. Here is ...
0
votes
2answers
62 views

How much oxygen does it take to burn a log of wood?

How much oxygen does it take to burn a log of wood? This is kind of a complex question because the wood itself contains oxygen, so it is not as simple to just compute how much carbon is in the wood ...
0
votes
0answers
14 views

Is my book's method of using Graham's law of effusion correct?

Problem: Let the container which contains NH3 gas be A, and which contains HCl gas is B. If both the stopcocks are opened at the same time, then determine the distance from container A at which white ...
0
votes
0answers
9 views

Translation of reduced units to real units for Lennard-Jones system and the Law of Corresponding States

I am struggling to completely make sense of a few sentences I came across in Frenkel and Smit (pg. 41): One may wonder why it is convenient to introduce reduced units. The most important reason is ...
0
votes
1answer
68 views

Difficulty understanding molar volume

Suppose I am at STP and I am dealing with an ideal gas and I have a 22.4L container (with a movable piston attached on top) filled with 1 mol gas. Now, I will try to change the molar volume in two ...
1
vote
1answer
40 views

How does molar volume change as the number of moles of gaseous mixture increase in same volume?

Consider this reaction: $$PCl_5<=>PCl_3+Cl_2$$ Suppose, I have a closed chamber filled with only PCl5 gas. Now, after some time, PCl3 and Cl2 will be produced. Now, the total mole number of the ...
0
votes
0answers
18 views

Can Lennard-Jones parameters (epsilon) be zero?

I was told that very often, intermolecular potential parameters (e.g. Lennard-Jones or Moorse etc.) are determined empirically via manual adjustment to reproduce experimental properties such as ...
0
votes
3answers
31 views

Why is Energy change occurring during the reaction at constant temperature and constant volume given by internal energy change?

When volume and temperature are kept constant, shouldn't internal energy remain constant (as it's a state function depending on state variables)? When heat is supplied, why does the internal energy ...
0
votes
1answer
42 views

Derivative of the osmotic pressure with respect to the chemical potential via Gibbs-Duhem

So I was reading through Atkins "Physical chemistry" 10th edition and was wondering something. Suppose you have an athermal system of $k$ particles, let us define the Gibbs-Duhem equation ...
1
vote
0answers
29 views

Does charged Li-on battery burn more than discharged one if damaged? [closed]

I am wandering if a charged Li-on battery burns more than discharged one if damaged, considering that the charged one has more energy in it. Thanks.
0
votes
0answers
29 views

Gibbs free energy of mixing

If we have to ideal gases A and B in two chambers divided by a thin wall. $n_A$,$n_B$ are the number of moles for each gas. I need to find the gibbs free energy of mixing when I remove the barrier. So ...
0
votes
1answer
32 views

Can Brownian motion explain why white smoke moves around in the air?

Can Brownian motion explain why white smoke (fume) generated by chemical reactions moves around in the air?
4
votes
0answers
28 views

Stern Gerlach experiment vs Zeeman effect

In the Stern-Gerlach experiment, we discover that electrons have an intrinsic angular momentum, that we happen to call "spin". They applied a magnetic field to a source of atoms (originally, ...
1
vote
0answers
19 views

How come the vapour pressure of mercury is so low, when its melting point is also relatively low?

I originally found my way to this by looking into why mercury has such a low melting point for a metal, and the explanation I got was that due to its electron configuration, it acts almost like a &...
0
votes
0answers
20 views

Form of second-order expansion terms in classical linear response theory

I am studying the linear response theory from this [1] reference which basically tries to calculate how a system in equilibrium responds when a force is applied. I understand for the first-order we ...
2
votes
1answer
46 views

Does salting water make it less diamagnetic?

I read some where that adding salt to water makes it less diamagnetic, but I've checked and water, sodium and chlorine ions are all diamagnetic. If salt water really is less diamagnetic, how is it so?...
0
votes
0answers
21 views

Ionic driving force through a channel: how to represent local concentrations

Essentially, I am not sure whether driving force equations (such as V-E_{ion}, based on Nernst equation) care about how ions are distributed locally within a cell. I have a situation when we want to ...
20
votes
1answer
1k views

Why the surface of wet paper deforms after drying?

When I use liquid glue to stick one sheet of paper on the other then why it's surface becomes zig-zag/deformed (I couldn't find very good word for it). First I thought that it's because of the air ...
10
votes
3answers
964 views

Why are diyas kept in water before pouring oil in them? What makes diyas absorb less oil after they are being soaked in water?

My mother had to light up diyas 🪔 (made like earthen pot in which we poured oil, dipped cotton and lit it). So before she poured oil in diyas, she submerged all diyas in water for a long time and ...
0
votes
1answer
21 views

How does the temperature expansion behave in a vacuum? (Electron beam evaporation)

In an electron beam evaporation process, the samples can be placed in two different positions. Position 1 is very close to the target, position 2 further away. Can we also conclude in vacuum that the ...
1
vote
1answer
47 views

Reverse shielding effect?

It is known that shielding effect causes a reduction in nuclear attraction of electrons,then wont the valence electrons cause a repulsive force on the inner shell electrons and cause a stronger '...
0
votes
0answers
35 views

What do chi ($χ$), psi ($ψ$), and capital gamma ($Γ$) stand for in these equations about molecular geometry (combination bands and overtones)?

Special case If one of the symmetries is doubly degenerate in the excited state a recursion formula is required to determine the symmetry of the $v$th wave function, given by, $$\chi _{v}(R) = \frac{1}...
1
vote
0answers
46 views

Is this a valid interpretation of the mean relative speed/collision rate of particles in a Maxwell-Boltzmann distribution?

In textbooks, the collision frequency $Z_{ab}$ between two species "a" and "b" is always given as something like: $$Z_{ab} = n_an_b\sigma_{ab} \Bigg(\frac{8 k T}{\pi \mu}\Bigg)^{1/...
1
vote
0answers
31 views

Marangoni Effect and the Navier-Stokes Equations

A quite well-known phenomena, oftenly treated in recreational physics, is the Marangoni Effect. Roughly speaking, we have a flux caused by a gradient of surface tension. You can look up YouTube, and ...
0
votes
3answers
83 views

Example of a body that receives heat but the temperature of the body decreases?

I am brushing up on my thermodynamics knowledge at the minute and am wondering if there is a process or circumstance in which a body receives heat but the temperature of the body decreases? In an ...
0
votes
1answer
35 views

Heating curve of water

If I am heating water in an open container with constant rate of heat supply (q) (water initially at 30°C ) until entire water converts to steam, the temperature (T) vs time (t) graph in sensible ...
3
votes
1answer
37 views

Does burning something with higher temperature make the burning faster?

Like if I burn wood at 500 C, or 1000 C, is there a relationship? Any equation that model this? Thanks
2
votes
2answers
53 views

What would happen if 63 $\rm TJ$ in form of superheated plasma would released abrutly?

Suppose that we managed to heat a some gas Xenon so that it contains 63 TJ of energy in the form of superheated plasma. What would happen if it is released abruptly of their contention chamber? Is of ...

1
2 3 4 5
22