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...].

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1answer
31 views

Why does adding salt to the water in a humidifier increase the amount of steam it makes?

Rather than "it decreases the latent heat of vaporization", can you explain why?
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1answer
67 views

Are chemical rockets really beyond 60% efficient?

Are chemical rockets really beyond 60% efficient? https://en.wikipedia.org/wiki/Rocket_engine “Rocket engine nozzles are surprisingly efficient heat engines for generating a high speed jet, as a ...
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7 views

Do zeotropic mixtures produce less cavitation when boiling?

Zeotropic mixtures rather than having a single equilibrium temperatures for a given pressure, or vice versa (equilibrium pressure for a given temperature), have a range a of equilibriums based on the ...
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3answers
39 views

Difference between the ground-state energies of ionic and neutral particles, and its relation with the ionisation energy

I'm a little bit confused about the concept of an ionisation energy and the difference between the ground-state energies of ionic and neutral particles. Until now, I thought that they were the same, ...
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1answer
34 views

Why does a layer of rubbing alcohol increase the transparency of frosted glass?

While cleaning a piece of glass with 70% ethyl alcohol, I made the observation that after swabbing a frosted portion of the glass, the glass appears to lose the "frosted" property ...
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Gasoline has a very high molar heat capacity. Is this a good thing for its use in engines?

Wikipedia states that the molar heat capacity of gasoline is $228 \, J/mol\cdot K$ (https://en.wikipedia.org/wiki/Table_of_specific_heat_capacities). This is more than twice that of liquid water ($75....
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21 views

Planes of symmetry of a molecule [migrated]

Are we limited to use only xy, yz and zx planes to check for planes of symmetry of a molecule? Because I see a plane of symmetry in the following molecule through the two shown H atoms or OH groups. ...
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21 views

Microwave heater for heatin graphite crucible

I'm interested in melting alumina in a graphite crucible, some details here. As a tungsten heating wire apparently will oxidize rather quickly in a regular atmosphere, i was wondering if i can't heat ...
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6answers
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What happens to the mass of a burned object?

If I were to burn a pile of wood weighing a hundred kilograms and I would have a big sack hanging over the burning pile. In this sack I would catch all the smoke that came from the burning pile, if ...
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Why does changing the number of protons cause such a fundamental change in an element? [duplicate]

When we change the number of electrons in an atom of an element, it constitutes an ion. When we change the number of neutrons of an element it constitutes an isotope. But when we change the number of ...
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Why aren't common magnets made of magnetite, $\rm Fe_3O_4$? Instead of ferrite, $\rm Fe_2O_3$?

Why are common, simple, cheap magnets like refrigerator magnets made (usually) of hematite ($\rm Fe_2O_3$) in some form, like 'ferrite', instead of the more magnetic and magnetizable magnetite ($\rm ...
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23 views

What are the origins of electronegativity?

Now, this might sound to be a chemistry oriented question. Today in physics class, we discussed bonds and electronegativity, and I wondered why it does originate. I would appreciate it if someone ...
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1answer
32 views

Why does the high charge density of a proton prevent it from existing alone in a solution?

My chemistry lecture notes say that when an acid is in a solution, it can give off protons, but only when there is another molecule that can accept those protons. It is said that the reason why the ...
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21 views

Theoretical origins of optical rotation

I'm not sure if I searched this with as fine-toothed a comb as I should have, but I found nothing online. I wanted to know if someone could point me to outlets wherefrom I could learn about the ...
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1answer
134 views

How to model RNA-DNA binding as a “string matching” problem using statistical physics?

I am trying to model the binding of a guide-RNA molecule with a target-DNA strand as it occurs before the CRISPR-Cas9 protein cuts the DNA. Both the RNA ($S_1 = \Pi_i \sigma_1(i)$) and the DNA ($S_2 = ...
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1answer
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How to obtain the “anti-symmetry” state explicitly?

For a $l=1$ and $s=1/2$ system ($l$ is orbital angular momentum and $s$ is spin angular momentum), $|j=3/2, m_j=3/2\rangle$ state can be written as: $$|j=3/2, m_j=3/2\rangle=(Y_1^1)_{\uparrow}=\frac{1}...
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1answer
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Can the recoil to the nucleus induced due to radioactive decay be enough to break inter-molecular bonds?

let's say I have radioactive labelled molecule such as ${}^{99m}Tc$--Methyl diphosphonate ${}^{99m}Tc$ undergoes gamma decay and emits a photon of 140 KeV. Said molecule also forms a bond inside bones,...
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2answers
24 views

How is the ground state energy of the helium atom experimentally determined?

According to Wikipedia the ground state energy of the helium atom is −78.95 eV. From the little I understood of spectroscopy, I believe that allows us to measure the differences in energies between ...
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6answers
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What causes the bucket to launch in the air?

In this video potassium is dropped into the bucket and it reacts with the water present in the bucket causing an explosion within the bucket itself. I don't see how an internal explosion makes the ...
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1answer
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Which element is A?

Which element used to be represented by the letter A? I'm guessing sulfur but this is only a guess. It's mentioned in Gamow (1930), "Mass Defect Curve and Nuclear Constitution". Proceedings ...
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0answers
34 views

Why exactly do bonds form?

From my solid state physics class I know about all the various types of bonds and the mechanisms that cause them. Let's leave the specific physics aside for now and just accept that a bond lowers the ...
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2answers
37 views

When a car is moving at constant speed, is chemical energy in the engine still being converted to kinetic energy?

I know for the car to be moving at constant speed, the driving force equals the magnitude of all the opposing forces so kinetic energy is not increasing and net force is zero, but I was reading about ...
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Critical point for fusion curve

In phase diagram, on vaporization curve there exists a critical point beyond which a gas can not be liquifies but why does fusion curve does NOT end at a critical point and continues to infinity?
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1answer
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Which one would represent complete combustion?

Say that I want to burn some fuel, so I'm aiming for a complete combustion, hence CO = 0 So I have 2 possibilities a) CO2 quantity = maximum, CO quantity = 0 (complete combustion) and O2 quantity = ...
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14 views

What would be preferred site for $\rm N$ and $\rm B$ co-doping in the ethylcyclohexane?

I want to replace two carbon of ethylcyclohexane: one $\rm C$ with $\rm B$ and the adjacent $\rm C$ with $\rm N$ in my hydrocarbon. Could you please explain me with possible reason that where can I ...
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1answer
13 views

Is incineration of a solid fuel complete or incomplete?

If I have some solid material like biomass and incinerate it at 1000 Celsius degrees for 15 minutes in an oxidized atmosphere within an incineration oven. As an output it gives me ash. Is the ...
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6 views

Are super dielectric materials magnetic?

Alumina powder mixed with boric acid and water is a super dielectric metamaterial, would it be attracted to a magnetic field? (Is it diamagnetic or paramagnetic?)
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1answer
36 views

How the bubble size in a champagne bottle evolve?

How the bubble size in a champagne bottle evolve ? Is it fixed or is evolving with time ?
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12 views

How replacing one hydrogen in cyclohexane with one F will change the physical properties of the cyclohexane

I want to check the effect of substitution of one "F" with one "H" in a hydrocarbon ring (lets say cyclohexane) on dehydrogenation enthalpy. At the same time I am thinking that the ...
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1answer
20 views

Mass energy equivalence, binding energy and chemical reactions

I recently was nuclear physics there I learned that the the actual mass of a nucleus is less than what we expect it to be (simply adding the masses of the nucleons). It is due to the release of ...
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Is the Debye–Hückel theory always true for sufficiently dilute electrolytes?

The Debye–Hückel theory states that for sufficiently dilute electrolytes the logarithm of the mean-ionic activity coefficient $\gamma_\pm$ of electrolytes is proportional to the ionic strength $I$ to ...
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1answer
37 views

How to dilute 5000 ppmvol of $\mathrm{CO}_2$ to obtain 250 ppm with a fluxmeter?

My problem is that I have a tank, containing $\mathrm{CO}_2$ at 5000 ppmvol, Oxygen $21\%$ vol and Nitrogen the rest, connected with a mass flow controller (flux max at $150$ ml/min). And I have a ...
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2answers
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Why does porridge start steaming more after the hob is switched off?

I have noticed that when I cook porridge in a saucepan, and stir it with a spatula, it only steams a little bit. But the moment I turn off the (gas) hob underneath, and keep stirring it with a spatula,...
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19 views

Does the spin of an unpaired electron in a sub-shell affect the spin of another unpaired electron in a sub-shell next to the other sub-shell?

Does the spin of an unpaired electron in a sub-shell affect the spin of another unpaired electron in a sub-shell next to the other sub-shell? For example Si 1s2 2s2 2p6 3s2 3p2 Does the unpaired ...
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2answers
5k views

How small can a flame get?

Last time I was watching a candle die. After its wick was finished, there remained just a drop of molten wax that was still slowly burning, with a flame that became smaller and smaller, down to a ...
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1answer
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Could you survive on hydrox in at 10 atmospheres?

I was told that hydrox is incredibly dangerous, that pure oxygen will combust without any source of ignition at 3 to 4 atmospheres of pressure, and that because humans are hydrocarbons they will act ...
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0answers
62 views

Reconciling QFT with chemistry?

For background, I am not very mathematically sophisticated with QFT, but have been trying to get a conceptual grounding. In his Biggest Ideas series, Sean Carroll discusses the idea that in QFT there ...
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1answer
49 views

Calculation of work done in different processes of thermodynamics in Physics and Chemistry

I am a high school student and I am very confused in thermodynamics, My confusion is that :In physics, when we study thermodynamics, we say that we cannot find the work done in irreversible processes ...
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Why does chocolate burn if you microwave it with milk?

Chocolate Science! I melt 3 spoons of dark chocolate in microwave oven in low. It melts in 3 minutes and it's just mildly warm. I add half a spoon of milk which makes it a bit cold again. So I ...
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22 views

What is the state-of-the art of electrolyzers that convert a gas stream into a liquid product?

I previous did some researches about split water into hydrogen and oxygen, and prepare to start a new project to investigate convert gas into liquid product. I read some publications about to covert ...
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1answer
25 views

Why does heat of reaction equal the change in enthalpy for chemical reactions?

Chemists say something like "amount of heat consumed for a chemical reaction equals the change in enthalpy" but I cannot understand why this is the case. Here is my argument: Since $H = U +...
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1answer
62 views

How much does the radioactive core of a nuclear bomb shrink due to compression by conventional explosives before it goes critical?

I saw a claim online that the conventional explosions used to detonate a nuclear bomb "significantly" compress the radioactive core, but I can't find any numbers indicating by how much the ...
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May the “reaction coordinate” in a chemical “reaction coordinate diagram” be represented by a time axis?

In chemical reactions one often considers so called "reaction coordinate" diagrams like this: Is it possible to interpret the abstract "reaction coordinate" just as a simple time ...
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13 views

Edges of single crystals depends on the basis or only on the Bravais lattice?

If I am not wrong, single crystals will tend to form edges along close-packed directions. From my (very) basic knowledge of solid state physics, crystal structures can be described as a lattice and a ...
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18 views

Is there a better coordinate framework and symmetry operator for constructing molecular orbitals of molecules with higher-order geometry?

The following excerpt is taken from [1] (with a few rewording, emphasizes are mine). In an attempt to construct molecular orbital (MO) of any molecule, one needs to determine the symmetries of ...
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Is it possible to have three stable liquid phases in a binary mixture?

With this system, it would be possible to have three liquid phases and two liquid-liquid coexistence regions at various compositions. Similar behaviour is common for solids such as alloys, sometimes ...
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1answer
83 views

How long should I wait to steep my tea?

This is not a homework question, this is a real question that I have. I like to drink green tea, and I use an electric kettle which brings the water to boiling. You can purchase kettles which bring ...
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1answer
48 views

If we mix alcohol and water, then we heat them, will the temperature stop at 78 degree which is boiling point of alcohol?

I understand that if we heat alcohol only, the temperature will stop at its boiling point, which is 78 degree. Then the boiling point of water is 100 degree. What will happen to the boiling point if ...
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2answers
506 views

Why doesn't the Diffusion Equation with an initial condition of $u = x$ lead to an even distribution?

Diffusion equation, or Fick's second law states $$\frac{\partial u}{\partial t} = D\frac{\partial^2 u}{\partial^2 x} $$ where $u$ is the concentration of the molecules. My question is, say if we have ...
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1answer
32 views

Molar mass on phase transition

I want to know for a single substance in transition between liquid and gas, if the molar mass will change.

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