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

learn more… | top users | synonyms (2)

0
votes
0answers
23 views

Gas Pressure in Industrial processes

Can anybody please help with the following? Ammonia is produced by the Haber process where nitrogen and hydrogen combine to form ammonia according to the equation: N2 + 3H2 == 2NH3 If 1 mole of N2 is ...
-1
votes
0answers
24 views

Balancing an equation [on hold]

I had an exam today and I havn't be able to find an answer to the question asking to balance this reaction equation, about oxalic and permanganate. Could you balance it or is it just impossible ? ...
3
votes
1answer
82 views

Physical distribution of salt anions and cations during electrophoresis

If I have a volume of $L$ liters of salt water at a concentration of $\approx N$ mM NaCl and I pour it into an electrophoretic apparatus (like this one: ). Once we turn the apparatus on, and set the ...
1
vote
0answers
32 views

Square of velocity = 2 times temperature times specific heat capacity ; seems too tidy [on hold]

So I did some algebra and came up with the following $v^2 = 2Tc$ where $ v = $ average velocity of the particles $ T = $ tempreture $ c = $ specific heat capacity but this seems too tidy
3
votes
1answer
129 views

Force field for Calcium ions, potassium ions and water in molecular dynamics

I want to adapt my existing MD simulation so that it can handle these three species. For the interactions of the ions I thought that I would use the coulomb potential, but I don't know what sort of ...
0
votes
0answers
17 views

Organisation in Periodic table [migrated]

Why We find big spaces left in the periods of the Periodic Table between H and He; Be and B, or Mg and Al? What is the logic of such organization of the periods?
2
votes
0answers
32 views

Why is the water diamagnetic?

I checked using my permanent magnet that water is diamagnetic. But why is it like that? Does this have any important consequence for life?
1
vote
1answer
22 views

Whats the maximum number of electrons that can fit into the outer shell of boron?

Whats the maximum number of electrons that can fit into the outer shell of boron? Like silicon has 4 electrons in the outer shell but the maximum it can hold is 8 electrons so whats the maximum number ...
0
votes
0answers
17 views

Spectral reflectance identification of types of iron rust [migrated]

According to the Wikipedia page about rust, there are red and green types of rust that occur on iron. Red rust is the reaction with oxygen and water and the green with chlorine (in oxygen poor ...
1
vote
1answer
86 views

Does O$^{2-}$ really exist?

In chemistry it is common sense that we have O$^{2-}$. But from a physical point of view, does O$^{2-}$ really exist as a negative ion? I mean, as an isolated ion. It is not apparent that a neutral ...
11
votes
2answers
769 views

How is the number of electrons in an atom found?

I was wondering, what type of experiments were held to identify the number of electrons in an atom? (For example, how do we say that carbon has 6 electrons and magnesium 12.) I would like someone to ...
0
votes
0answers
40 views

How can I create particle-in-a-box diagrams in LaTeX? [migrated]

Interested in creating particle in box diagrams at various energy levels and dimensions. Does anyone have source code to do so or suggestions of good packages to use?
0
votes
1answer
127 views

What happens to gas molecules after ionization?

I know that gas molecules conduct electricity after they get ionized but what will happen if we keep increasing the voltage even after ionization? Will it explode? If it will then how much energy ...
0
votes
1answer
23 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 ...
1
vote
1answer
97 views

reactions in molecular dynamics simulations

EDIT: Apparently this is called reactive molecular dynamics. It seems that the ReaxFF potential function is used for some reactions like this. I am interested in adding support for reactions to a ...
0
votes
1answer
78 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\\ ...
0
votes
1answer
47 views

Have scientists always known that the Sun was not a fuel+air system?

Astronomy is far older than nuclear physics. So there was a long time in which fire was a reasonable explanation for the sun burning. Has any scientist figured out the sun cannot possibly be a normal ...
1
vote
5answers
5k views

Why does burning magnesium explode when sprinkled with water?

Magnesium powder burns extremely well and reaches temperatures of 2500°C. However, attempts to extinguish such a magnesium fire with conventional water (e.g. from a garden hose) only make it worse: ...
6
votes
1answer
314 views

Donors/Acceptors in Metal Oxides

Can anyone explain to me why most articles describe chromium as an acceptor in titanium dioxide? In TiO2, titanium has the charge state Ti$^{4+}$ and oxygen has the charge state O$^{2-}$. When Cr ...
0
votes
1answer
52 views

What happens if a free radical is placed in absolute vacuum?

I'd like to know what happens if a free radical has no material around to interact with. I have asked many people but I am not satisfied with their answer. I know there is nothing like absolute ...
0
votes
1answer
34 views

Chemical reaction A+B$\leftrightarrow$C. Equilibrium VS Non Equilibrium

Could you please confirm or say why I am wrong? Let us consider the steady state of the chemical reaction $A+B \leftrightarrow^{k_+}_{k_-} C$, with $k_+$ and $k_-$ the forward and backward rates. ...
1
vote
0answers
22 views

Given the Pair Correlation Functions for a Multi-component Fluid, is There a Simple Way to Obtain the Helmholtz Free Energy?

I think it may not be possible. Given all the pair correlation functions (e.g. calculated from Ornstein Zernike theory), it seems possible to obtain the internal energy (assuming different species ...
17
votes
6answers
3k views

Where should a physicist go to learn chemistry?

I took an introductory chemistry course long ago, but the rules seemed arbitrary, and I've forgotten most of what I learned. Now that I have an undergraduate education in physics, I should be able to ...
0
votes
1answer
47 views

Is Boltzmann constant $k_B$ constant?

I heard in a lecture that Boltzmann constant $k_B$ is not constant in some special cases. Do you know the title of the article which contains this one? Do you think this idea is true?
44
votes
4answers
62k views

Why do grapes in a microwave oven produce plasma?

Some of you may know this experience (Grape + Microwave oven = Plasma video link): take a grape that you almost split in two parts, letting just a tiny piece of skin making a link between each ...
0
votes
1answer
40 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? ...
3
votes
1answer
652 views

Why does NaCl (aq) conduct electricity but NaCl (s) does not?

Why does sodium choloride in its solid state not conduct electricity, but in its aqueous solution state it conducts electricity easily?
1
vote
2answers
524 views

Gas viscosity at high pressure, high temperature

EDIT 1 PER COMMENTS I am wanting to model nitrogen gas viscosity as a function of pressure and temperature OR learn of an existing equation that models nitrogen viscosity for the pressure and ...
17
votes
4answers
3k views

Boiling water and salt

I would like to have a good understanding of what is happening when you add salt to boiling water. My understanding is that the boiling point will be higher, thus lengthening the process (obtaining ...
0
votes
0answers
34 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 ...
2
votes
3answers
79 views
0
votes
1answer
37 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 ...
0
votes
0answers
32 views

Isothermal Expansion in Real Gases

I understand that for a ideal gas in the case of reversible isothermal expansion, $\Delta U=0$ and $-Q=W$ but in case of a real or van der Waal gases, how can I find $Q$, $\Delta U$ and $\Delta S$?
0
votes
1answer
40 views

How to thermodynamically understand process of burning a piece of coal?

Let's imagine that I have a match in hand and nugget of coal on my desk. Then I light up the match and place it for few seconds near the coal so a tiny piece of nugget catches fire. Then another piece ...
4
votes
1answer
5k views

How to know what materials are good conductors of electricity?

I'm not asking a question like "Is the wood conductive?". No. I'm asking what properties do they have to have to be good conductors. Theoretically I mean. Thanks.
7
votes
3answers
2k views

What is the quantum mechanical explanation of the octet rule?

What is the quantum mechanical explanation of the octet rule? In other words, what makes the octet rule be true from a quantum mechanical view? How we explain what makes some atoms don't follow the ...
0
votes
0answers
47 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 ...
1
vote
0answers
141 views

Confusing Chemical potential of mixtures

I feel that there are very few textbook that treat the chemical potential of mixtures in an understandable clear way, which is why I wanted to ask here about certain things? Although I do not have a ...
0
votes
0answers
33 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.
4
votes
1answer
146 views

Can ice freeze? [closed]

We know that ice is already the frozen (solid) form of water. The question is more like: Can this frozen form freeze further? Or can it become more solid? (for example, by exposing to colder ...
3
votes
1answer
80 views

Why is the objective function used in Nudged Elastic Band method reasonable?

In Nudged Elastic Band (NEB) method, which is used to find reaction pathways when both initial and final states are know, an objective function is first constructed and then minimized to find reaction ...
1
vote
1answer
80 views

Increase in Solubility of a Gas with an Increase in Temperature

On the UC Davis ChemWiki I read, "some gases have an increase in solubility with an increase in temperature." I understand why this is applicable to solids in liquids such as water, but why is it ...
-1
votes
1answer
37 views

How does gas pressure increase the lifespan of Halogen tungsten lamps in the Halogen Cycle?

I am curious about this passage "Since quartz is very strong, the gas pressure can be higher,[5] which reduces the rate of evaporation of the filament, permitting it to run a higher temperature (and ...
4
votes
0answers
39 views

What is the argument for detailed balance in chemistry?

Detailed balance is an important property of many classes of physical systems. It can be written as $$ \frac{p_{i \to j}}{p_{j \to i}} = e^{\frac{\Delta G}{k_B T}},\tag{1} $$ where $i$ and $j$ ...
1
vote
3answers
363 views

Melting and Boiling Points of Odd Materials

In Chemistry, I was taught that there are three main states of matter: solid, liquid, and gas, and that heat and pressure determine that state. For some substances, the line is blurry between them. ...
8
votes
3answers
2k views

How are the calories in food calculated?

This is intended to be a fun question. Calorimetry used for calculating the heat generated from chemical changes has been around for centuries, however, I suspect the process for calculating food ...
4
votes
3answers
212 views

Why does a pitcher with lemon juice have foam, while one with pure water does not?

Whenever I pour water into lemon juice (pouring directly from the tap into the pitcher, not quietly along its edge) I get a foam on top: The same pitcher with water (same water tap, pitcher, time ...
0
votes
2answers
15 views

Exothermic heat release mechanism in gases

How is heat released when bond formation occurs in gases? For example, when atomic oxygen and molecular oxygen combine to form ozone?
0
votes
2answers
61 views

Could we describe acids and bases using electromagnetism?

Why don't we use Maxwell's equations in acids and base theory? Surely the interaction between two charged species is readily described by this. The theory I have so far come across is HASB theory. ...
4
votes
3answers
720 views

How much heat from a fire actually warms your home?

A fire in a hearth disperses heat to, I guess, three places: the bricks of the chimney out the hearth (where the person tending the fire is standing) out the chimney, above the house How would you ...