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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761 views

Are valence electrons in nonpolar molecules localized/delocalized?

Are valence electrons in non-polar molecules localized or delocalized? I'm quite confused about the whole electron localization and delocalization business. I'd love a simplified explanation that a ...
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1answer
99 views

Calculate the required water for humidity [closed]

I'm not sure if this is the right place to ask. I have a humidifier, and a closed room. Basically, I want to know the required water to reach a certain level of humidity. My room volume is 42 meter ...
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1answer
130 views

How fair is it to say that all chemistry arises from failures of the ideal gas law?

I was reading here about how the ideal gas law assumes point masses and non-interaction. Is it fair to say that all chemistry arises from failures of that? Of course, such a sweeping generalization ...
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623 views

Chemical Equilibrium - Why do changes in pressure cause a shift in the ratio of products and reactants?

I understand Le Chatelier's principle and how every change to an equilibrium system causes an opposing reaction from the system. I also understand how, when pressure is increased, the equilibrium ...
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474 views

What's the vapor pressure and evaporation enthalpy of a saline solution?

Suppose you dissolve an amount of salt in water. Because of the attraction between the ions and the water molecules, you'd expect lower vapor pressure and higher enthalpie, both depending on the ...
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60 views

Action on Lard Oil

If water is mixed with lard oil and heated (creating some super-critical liquid with water), how does this affect the volatility of the mixture in comparison with its purity..? So, My question is: ...
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55 views

Is it possible to make use of paper/bill permeate by chemical compound to became a paper-made bullet-proof vest?

Is it possible to make use of paper/bill permeate by chemical compound to became a paper-made bullet-proof vest? This is inspired by Greece and Italy tend to have more riot than rest of the Europe ...
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351 views

Circulate smoke in a closed system

Hey i am by no means a scientist but i have a idea for a art work using smoke. Basically what i want to know is whether it is possible to circulate smoke by means of a pump through a transparent box. ...
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13 views

How strong is the HCN Union when modelling with springs

I'm modeling the HCN Molecule with springs, giving the bounds between H and C the name k1 and between C and N k2. Is there any information of how strong is the bound? We were asked to get the ...
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15 views

breaking bonds with light

Light, for instance green light (532 nm = 2.33 eV) has an energy comparable to that of many chemical bonds (C-C bond dissociation energy is about 3.6-3.7 eV). So how is it that I'm not being burned ...
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6 views

Butler-Volmer Anodic and Cathodic Activation Constant Proof

In the Butler-Volmer Equations, I have often seen the activation constant at the anode and cathode related by: $$ a_a=1-a_c $$ This is the relation used, for example, on plots of this equation on ...
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26 views

How did scientists calculate the number of atoms in one mole of a substance? [duplicate]

Please explain me about the basic methods about how can we calculate that 1 mole of a substance contains 6.022140857 × 10 23 molecules? Tell how the modern scientists calculated it and how Avogadro ...
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25 views

What would be the best material to reflect radio waves?

I was thinking about what would be needed to build a parabolic dish and I inevitably came to what material to use. From what I could gather after a quick search on the internet, it would seem that any ...
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16 views

Copper vs Tungsten (Diffusion)

I've been studying on how to compare the activation energy for (void-) diffusivity of Copper versus Tungsten. I ended up finding $E_a[cu] = 1.1[eV]$ and $E_a[W] = 5.2[eV]$ in literature where the ...
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25 views

Humidification Problem [closed]

Humidification Imagine that water is evaporating into initially dry air in the closed vessel shown schematically in Fig. 8.1-1(a). The vessel is isothermal at 25 C, so the water’s vapor ...
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35 views

calculating with quantum numbers and shape of nodal shells

I'm attending in a chemistry course now, and in the beginning we scratch the surface of the quantum physics, which have led me to some problems. Mostly I understand all what we get until now, but ...
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29 views

What happens when a semipermeable membrane allows only one solute to pass through?

I'm essentially a medical student where we deal a lot with osmosis. But when we are taught, it is done generally with only a single solute in consideration. What if two different solutes are used on ...
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20 views

Gibbs isotherm and calculating interfacial tension change from first principles

Question: Is it possible for a solid particle to change the surface tension between two phases? (or: Does a solid particle have a chemical potential?) This question stems from the more ...
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57 views

Calculate how many photons hitting a sample that are absorbed

In the determination of the quantum yield of a photoisomerization, $\Phi,$ the following is needed $$ \Phi = \frac{\mbox{Number of "reactions"}}{\mbox{Number of absorbed photons}} $$ The photon flux ...
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32 views

How can we use conductivity measurements of water to find hydrogen ion concentration of water?

How can we use conductivity measurements of water to find the hydrogen ion ($\mathrm{H}^+$) concentration in water?
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28 views

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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28 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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24 views

Ionization Through Atomic Collisions - Any Reason(s) for Its being Unimportant?

The dominant processes which contribute to the ionisation of a gas (which is possibly hot and dense) are often deemed to be electron-impact ionization ($A + e^- \rightarrow A^+ + e^- + e^-$) and ...
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23 views

Charge Transport Mechanicsm of Organic Semiconductors

I understand the general concept behind inorganic semiconductors. Start with Silicon, dope the material to add an electron or a hole, and now these are free to move about in the material, creating ...
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31 views

Difference between “chemical master equation” and “master equation”

Is there any mathematical difference between "master equations" and "chemical master equations"? Is the chemical master equation in any way more specific than the master equation? I see the former ...
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146 views

Gibbs free energy + maximum work

The Gibbs free energy is the maximum amount of non-expansion work that can be extracted from a closed system; this maximum can be attained only in a completely reversible process. This maximum work is ...
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53 views

Difficulty in understanding Maxwell Boltzmann distribution in case on ions in a field

I learned that the velocity of molecules obey Maxwell Boltzmann (MB) distribution at a Temperature T. If I have ions of mass 'M' accelerated to 2eV in a specific region. As the ions are not ...
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507 views

How does the dissolution of salt affect the solution density?

Suppose you have a container of water as a solvent and you a certain amount of salt as a solute sitting at the bottom of the container that has yet to start dissolving. Supposing temperature and ...
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20 views

Why does carbon help with electron transfer in a dye sensitized solar cell?

what property of carbon(soot) makes it easier for electron transfer within a dye sensitized solar cell?
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45 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 ...
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44 views

Heat Retention of Wine

This may seem odd and lengthy but I am going to attempt to consolidate my thoughts as much as possible. I'm sorry in advance for the length of my post and if this is confusing. I am currently ...
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62 views

Virial equation - Taylor expansion

I don't get how Taylor expansion over $ \frac{1}{\overline{V}} $ of Virial equation of state is carried: $Z = \frac{P\overline{V}}{RT} $ which yields $$ Z = 1 + \frac{B_{2V}(T)}{\overline{V}} + ...
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26 views

Maxwell relations | U goes down pressure?

Differentiating Helmholtz function $ A = U - TS $ with respect to $V$ we get: $$ (\frac{\partial A}{\partial V})_{\scriptscriptstyle T} = (\frac{\partial U}{\partial V})_{\scriptscriptstyle T} ...
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95 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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50 views

Does a fixed amount of gas have slighty more mass when at a higher temperature?

According to relativity, energy and mass are equivalent. Does this mean that the energy added to a fixed amount of gas when it is heated adds slightly to the mass of the gas? The difference would be ...
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43 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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102 views

Question regarding NaCl equilibrium separation

So I am tutoring someone later and one of the problems is from Eisberg/Resnick Ch 12. The potential energy $V$ of NaCl can be described emperically by $$V = \frac{-e^2}{4\pi\epsilon_0 ...
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53 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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137 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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91 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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128 views

What's the relation between molecular orbitals and electron density?

The way molecular orbitals are drawn represent the "encapsulated" space in which the wave function has a significant amplitude. How do I obtain from this the electron density? Is there a fundamental ...
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60 views

Calculating the heat transfer into CO$_2$ gas at a constant pressure

I am having trouble with a homework question and I am just not sure how to attack it. We have not covered how to deal with non-ideal gases yet, and we are expected to answer this question without that ...
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238 views

Why do aromatic rings absorb in UV?

Why do aromatic rings absorb in UV? I think that the whole molecule absorb light which causes transition of an electron to another molecule orbital.
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73 views

(Chemistry) Dimensionless heat transfer coefficient

I'm trying to reproduce in Matlab the model of a continuous stirred tank reactor (CSTR) that I've gotten for a project. The model is written in the state space and uses some dimensionless values, ...
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226 views

Milk-First School

I have always been struck by the huge amount of different arguments about the issue: When you make a cup of tea, the milk should be poured first or added to the cup after the tea? Wikipedia, ...
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1answer
113 views

On Thermodynamics of Spontaneity of the Reduction-Oxidation Chemical Reactions

According to the first and second law for a closed system containing different chemicals we have \begin{align} &\delta Q - \delta W = dU = T dS - p dV +\sum_i \mu_i d N_i\\ ...
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132 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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89 views

In what sense can an object in outer space be “on fire”?

The famous "Tears in rain" soliloquy in Blade Runner goes like this: I've... seen things you people wouldn't believe... [contemptuous laugh] Attack ships on fire off the shoulder of Orion. I ...
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379 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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50 views

Specific Gravity vs. Pore Space in Chromatography Column

Wondering if we can apply molecular specific gravity to elucidate average time required to pass through a column given porespace, distance and viscosity? This would eliminate the need for special ...