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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Why higher FAT level implies more signal in XPS analysis?

In XPS analysis, the FAT (Fixed Analyzer Transmission) parameter controls the electrostatic field of an emispheric analyzer, called Pass Energy $E_P$. The FWHM of a peak of signal is given by $$\...
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81 views

Bonding Two Cationic Hydrogen Isotopes (protium) yields H2 or He?

If you have two hydrogen atoms. And they are the isotope form "Protium" (1 neutron removed) and they are also cationized +1 (1 electron removed) then you have (in a sense) a single proton (two of them ...
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96 views

Visible wavelengths of air fluorescence data - needed for school demo laser telephone design

I'm seeking information about fluorescence in visible wavelengths (390-700nm) of any of the main constituents of air ( $ N_2, O_2, CO_2, H_2O, CO, etc. $) that can be excited with a (hopefully low-...
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313 views

Electrolysis boat engine

Would it be possible to create a submersible boat engine using the combined principles of electrolysis of water, ramjet propulsion, and hydrogen-oxygen combustion similar to that used in rocket ...
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122 views

Filling an empty box with ambient air

A rigid box has a volume of $V_1$ and is thermally isolated so that it exchanges no heat with its environment. Initially the box is empty, and the air around it has a pressure of $P_0$ and a ...
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149 views

Reaction Energy

Is the energy involved in exothermic and endothermic chemical reactions positive, negative, neutral, or something else? As in, what does it affect/come from (neutrons, protons, electrons)? Does it ...
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1answer
404 views

Why does the rate of melting of an ice block vary in different methods?

I saw that an ice block melts faster when it is placed in a microwave rather than when it is exposed to flame. Could it be because the flame creates a layer of water vapor between the flame and ice? ...
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417 views

Bandwidth-Pulse Duration Relationship

Assuming Gaussian pulse, the relationship between pulse duration and bandwidth is given by: $$\Delta \nu \cdot \tau \geq 0.441$$ If the rms bandwidth and rms pulse duration are used, then the ...
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588 views

Solar still and how it works

I use a solar still that holds 182 cubic feet of water. Here is how it works: There is an insulator on both sides of the metal bowl. On the outside it covers the whole thing. on the inside it covers ...
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938 views

Saddle point and transition state of a molecule

During a transition of a molecule from one state to another, it pass through a transition state. This transition state, mathematically speaking, is a saddle point. That means, the second derivative ...
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2k views

Calculating molal depression constant from latent heat of fusion

Calculate molal depression constant of water if latent heat of fusion of ice at $0^\circ \text C$ is $80 \text{ cal/g}$. All I could find was the equation $K_f=\frac{0.002T^2}{L_f(\text{in cal/g})}$ ...
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106 views

What is the physical property of metal nanoparticles?

I am a Math student but now I have to deal with gold nanoparticles in aqueous solution. Now I was wondering whether the physical properties of gold nanoparticles are the same as the properties of gold ...
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1k views

Difference between Non-Polar and Dipole moment $\vec\mu$=0

Is there any difference between a molecule having $\vec\mu=0$ and being Non-Polar?
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167 views

How to measure electrical resistance?

Is it possible to theoretically measure the resistance of passing of electrical current through liquid electrolyte (distilled water + NaOH) ?
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245 views

Which bonds are the cross-links and which are secondary bonds (in elastomers)? [closed]

Elastomeres are "defined" as: "linear-chain polymers with widely spaced cross-links attaching each molecule to its neighbours" Now I found sentences (talking about glass transition): "This means ...
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1answer
72 views

Selection rules in rotational spectroscopy- water molecule

The University of Liverpool maintains a ChemTube 3D page, where it says http://www.chemtube3d.com/spectrorotcd0-CE-TEST-ROTATE-ALL.html *> Highly symmetric polyatomic molecules, such as carbon ...
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69 views

What are some molecular systems which have quantum states that are measurably incompatible?

What I'm looking for is a molecular system, which we can produce in a lab, that is, A discrete variable system (ie, a finite dimensional hilbert space) It has observables that are incompatible with ...
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74 views

Geometric Condensation Patterns on Windshield

I noticed these patterns in the condensation on the inner surface of my car's windshield when I turned on the defroster. Usually when I see lines like these on condensation I assume it's because of ...
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2answers
1k views

Carbon in the form of graphite a conductor?

Well, it happens a I have a glucose test strip (One Touch Ultra) which has three electrodes (Counter, Working and Reference) and I'm guessing this electrodes are made from graphite mixed with a binder....
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228 views

Why are helium and lithium so different, while lithium and beryllium are similar?

How is it possible that helium, having 2 protons, and lithium, having 3 protons, are so different in terms of their physical properties? How come one is a gas at room temperature and the other is a ...
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1answer
38 views

Equivalent in wood/coal/methane of one litre of petrol

I want to create a visual comparison between different sources of energy. I would like to show how much wood, coal, methane, water+level difference, etc. could potentially generate the same energy of ...
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2answers
1k views

Conservation of energy when we drive a car

When we drive a car, we use gasoline as the source of energy. When we arrive at the destination, we lose some of the gasoline, used to move the car from one point to another. Then how energy is ...
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3answers
532 views

Why is grass green? [closed]

How come grass isn't blue or pink, but apparently, it is according to this scientist it is every color but green. I also got told by my teacher that grass is only green and no other color. So I am ...
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2answers
186 views

Is there any non-metallic oxide that remains in solid state at room temperature?

Except for metallic and semimetallic oxides, is there any oxide (non-metallic oxide) which remains in the solid state at room temperature?
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75 views

What does “energy required to make room for the system mean”?

I read the answers to What does enthalpy mean? and both answerers mentioned that it's the energy required to "make room for the system". What does this mean? How do we provide that energy and how does ...
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70 views

Isothermal process [closed]

Internal energy is made up of the potential and kinetic energies,explain in molecular terms why the change in the internal energy of an ideal gas as the volume changes at constant temperature is ...
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36 views

Why don't ion thusters Directly use exothermic reactions to heat up plasma and Ionize gas?

Ion thrusters require a lot of energy, because of their high exhaust velocities. But why can they just pump a mixture off hydrogen and xenon into the chamber and mix it oxygen and burn it up. Doesn't ...
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94 views

What is this form of notation called?

$$^{14}_6C \rightarrow ^{14}_7N + E^{-} + \bar{\nu}_e$$ Just curious!
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1answer
43 views

Why is an electrodes standard reduction potential does not depend on amount of chemicals?

The standard reduction potential is fixed for the type of chemical reaction. Why is it so? Why is an emf of a cell or an electrode's Standard reduction potential does not depend on say, quantity of ...
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2answers
681 views

Methods to convert nitrogen nuclei to oxygen nuclei?

Are there any "safe" method that allows converting the nitrogen into oxygen? There's Ernest Rutherford that uses alpha particles aimed at the nitrogen to create oxygen and hydrogen. But are there ...
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1answer
2k views

Any metal or chemical or any thing which repels Iron

I on a project, i required a metal/chemically treated metal/Chemical/anything which repels iron and steel like two same side magents do. I searched in the internet and didn't found anything which ...
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1answer
64 views

How much energy does a particle need to evaporate?

If i had a container of water at approximately room temperature, how would I work out how much energy an individual molecule needs in order to evaporate? Obviously water is far too complicated to ...
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1answer
2k views

Difference in viscosity-concentration and reduced viscosity-concentration graphs

I prepared 3 different polymer solutions with varying concentration of 100, 50 and 25 ppm in order to measure their viscosity . When I plot concentration vs viscosity graph in the excel, I have a ...
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45 views

Can someone explain how this occurs? [closed]

Initial spillage of a liquefied gas from a pressure vessel behaves differently to that described above. In this case the liquid, on escape, is at a temperature close to ambient. However, the high ...
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44 views

Constant pressure

When we refer to constant pressure like in Charles law what is this pressure? The pressure of the gas or the pressure that the container (the piston maybe) exert on the gas? Also does atmospheric ...
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1answer
29 views

Hydrogen oxygen fuel cells

In hydrogen - oxygen fuel cell, the electrode used is carbon electrode.Hydrogen is passed through through the anode compartment where it is oxidised. Oxygen is passed through the cathode compartment ...
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2answers
250 views

What happens if Jupiter is ignited?

I was wondering, what would happen if there was a large amount of oxygen released into Jupiter's atmosphere, than igniting it? Because Jupiter is 90% gas, therefore being a big fire waiting to happen (...
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1answer
223 views

Will all water evaporate before oils and fats start to evaporate?

Water starts evaporating at 100c and oils and fats have a smoking point (equivalent form of evaporation) which is a lot higher and will vary depending on the purity of the oil and fat. If you are ...
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73 views

What is implied when the spectrum of a star has deep absorption lines at the frequency of a level 1 hydrogen transition line?

I think this means that their are many adsorptions occurring at the lower wavelengths. But why could this be? What does this say about the star? What I was thinking is that it could imply that the ...
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1answer
4k views

Why do molecules have $3N-5$ or $3N-6$ degrees of freedom?

In linear molecule, it has $3N-5$ degree of freedom in vibration mode and $3N-6$ in non-linear molecule. I can get idea about $5$ and $6$ which is related to translation and rotation but I cannot ...
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2answers
3k views

Physical reason of adding salt when we're cooking rice (osmosis)

Why do we add salt when we're cooking rice? I know one reason is related to the boiling point of water but someone said it is also related to "Osmosis". What is the relation between adding salt and ...
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102 views

Anatomy of combustion

I don't understand how energy is released in combustion. We have a reaction of a combustible material with oxygen and this releases energy. In what form is this energy released? It should be some ...
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136 views

Can $CO_2$ be separated into $C$ and $ O_2$?

I'm doing a little bit of research for an experiment that I want to conduct in science and it relies on that one question. So, Is it possible to separate a $CO_2$ molecule into a $C$ and $O_2$? Has ...
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3answers
66 views

Is it possible to power a car with chemiluminescence? [closed]

Chemiluminescence means substances that in a reaction emit light. I wonder if such a reaction would be possible to power an electric car using an photovoltaic panel lighted by the chemical reaction?
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101 views

How fast will I get if I burn a comet? [closed]

Assuming I have a spacecraft which is $30,000\,\mathrm{kg}$ (roughly the size of the Apollo spacecraft). If I take a comet and (theoretically) electrolize it perfectly to hydrogen and oxygen. I know ...
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1answer
67 views

Where is the extra heating value of coal compared to the original wood coming from?

My question is about the formation of coal seeming to break the laws of the conservation of energy (that energy can neither be created nor destroyed but instead transferred from one thing to another). ...
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1answer
30 views

Nucleus in the wires

Can someone explain why we consider the electrons to move through a wire and not the nucleus? Couldnt atoms get ionised with losing a proton?
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616 views

If Planck’s constant were larger would photons of light of the same frequency be more energetic or less energetic?

If Planck’s constant were larger would photons of light that have the same frequency be more energetic or less energetic?
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why do microscopic cracks happen?

2 weeks ago i asked a question about " Gas permeation through solid metal? " i have got a very good answer here .but microscopic crack was mentioned in the answer. i searched in Internet but i didnt ...
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508 views

Exothermic vs. endothermic reactions

An exothermic reaction is a chemical reaction that releases energy by light or heat. Does this mean that if I mix two chemicals in a test tube when the reaction between them is endothermic then the ...