The study of chemical systems using the laws and concepts of physics. This usually requires the techniques of thermodynamics, statistical mechanics and quantum mechanics.

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2
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2answers
42 views

Fitting parameters of Lennard-Jones potential to properties of real materials

I'm using the Lennard-Jones potential for some (very simple) protein docking simulation* and couldn't find parameters for different materials (like $\ce{C}$, $\ce{N}$, $\ce{O}$, …). Does it even make ...
5
votes
0answers
39 views

How to simulate surface tension?

I am trying to create a water drop simulation for measuring hydrophobicity of surface. I don't know how to simulate the contact angle which is related by younges equation to the surface tensions for ...
6
votes
2answers
346 views

When I heat up a balloon, does the air inside increase in pressure as well as volume?

When I heat up a balloon, does the air inside the balloon increase in pressure as well as volume? I thought pressure and volume were inversely proportional? Or does pressure and volume increase as ...
1
vote
0answers
23 views

What is the Difference between difference between Standard Electrode Potentials and Standard Reduction Potentials?

As the question suggests I am wondering the difference between standard electrode potentials and standard reduction potentials. I know that they are both a measure of the Voltage from certain ...
1
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0answers
40 views

Molecules from atoms [on hold]

Why do two oxygen atoms combine to form a molecule and not 3 or 4? Also, why does one sodium and one chlorine atom combine to form $\ce{NaCl}$ while two chlorine atoms are required to combine with one ...
-1
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0answers
17 views

Should I use the formula for ideal gases?

What did the question means actually? Should I use the formula for ideal gases? Isn't it the number of mole in the hydrogen gas and isotopes should be the same?
14
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5answers
495 views

Why does HCN boil at a higher temperature than NH3?

The boiling point of ammonia is −33 °C while that of $\ce{HCN}$ is 25 °C. In a recent AP (Advanced Placement) Chemistry test, a free response question asked why this is the case. Can someone shine ...
1
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0answers
38 views

How to determine if a compound is likely to become a solid at room temperature?

Reasoning: My guess would have to be that it has to do with the strength of the intermolecular forces between each molecules. Take for example, molecular compounds that have a very low molar mass like ...
6
votes
2answers
113 views

Is there any other way of solving this problem than trial and error

I have a wave number question which I have partially solved The question is:- What transition in He+ ion shall have the same wavenumber as the first line in Balmer series of H atom? (a) 7->5 (b) ...
4
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1answer
64 views

Theoretical versus empirical equations

I'm familiar with the fact that theoretical formulae are based on already known theory and are very frequently simplified (some equations don't include interactions between molecules for example) ...
0
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1answer
22 views

ionising atom(s) with gamma rays

if a gamma ray hits an electron and transfers energy, does it hit that electron (ionising the atom), transfer all its energy and stop or does it pass through multiple electrons, transferring a portion ...
13
votes
1answer
799 views

Are there any known chemical properties of tritium water that make it unusually different from protium water?

I suppose the first question supporting the main question is, has tritium water ever been synthesized in sufficient quantity to test chemical properties? If so, and apart from the obvious radioactive ...
-2
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0answers
70 views

How clean do I need to be to not be able to conduct electricity?

We all know about capacitive touch screens, I was wondering, how clean does my finger need to be, so that no electrical current can pass into my body when I touch the indium tin oxide surface? Clean ...
0
votes
1answer
61 views

Out of the various states of matter, which one is the most used?

Apart from the what everyone knows about, solids, liquids, gasses, plasma, BEC. What are the other states of matter and what are they used for? I would like an explanation as well as an example of ...
0
votes
1answer
44 views

Percentage purity of H2O2 after reaction [closed]

$10\:\mathrm{cm^3}\:\ce{H2O2}$ solution when reacted with $\ce{KI}$ solution produced $0.5\:\mathrm{g}$ of $\ce{I2}$. What is the percentage purity of $\ce{H2O2}$? Firstly, I don't understand the ...
0
votes
1answer
29 views

Equations for internal energy and their relevance to the derivation of the equation for entropy for perfect gases

My lecture handout proves derives an expression for entropy thus: For a perfect gas $U=U(T)$ (i.e. is not dependent on volume; only temperature). Therefore, $(\frac{\partial U}{\partial V})_T=0$ ...
24
votes
3answers
2k views

Why is fresh ice sticky?

Fresh ice cubes are almost instantly sticky and easily cling on to fabric and other similarly rough surfaces. A few minutes later, however, the effect almost completely disappears. What is the ...
4
votes
3answers
81 views

Liquid-Liquid phase separation

Consider a container that contains a mixture of many liquids. Can two of these liquids phase separate without having any significant effect on other liquids inside the container? Is there a feasible ...
0
votes
2answers
35 views

What are some general tests that would determine an unknown compound?

I know a little bit about unknown compounds but I am still new to the topic here. I know that you could use filtration, chromatography and distillation. You can also combine the unknown with others to ...
6
votes
1answer
66 views

Fluoroscence vs. Phosphoroscence

Not in an atomic aspect, I learned that fluoroscence is the emission of light from substances until the source of light dissapears (there is no emittion in the dark), on the other hand ...
3
votes
1answer
29 views

Which unit cell do we obtain if spheres are arranged in ABABAB type in 2D and then that 2D layer is arranged in AAAAAA type in 3D?

Arranging spheres ABABAB type in 2D gives us close packing. Now, this layer if arranged in ABABAB (in 3D) gives us HCP and if arranged in ABCABC (in 3D) gives us FCC. What do we get if we arrange ...
4
votes
1answer
39 views

Expansion of a gas, calculating new volume

Hi I was reading this while studying for an exam and wondered how you would go about calculating it, I’m a bit confused. $\mathrm{5~mol}$ of a gas is confined in a piston (volume $\mathrm{100~cm^3}$) ...
5
votes
2answers
47 views

Predicting melting points of substances based on their molecular/atomic structure

Wouldn't it be great to be able to predict the melting point of a metal based on the atomic number and not by looking in some table for the value that was measured experimentally by someone else? Or ...
3
votes
1answer
107 views

Lambert Beer's law coeficient

While the Beer's law equation is $A=a \cdot b \cdot c$, according to my book, $a$ is a coefficient which is: a characteristic property of the analyte in a specific solvent, and its values will ...
0
votes
0answers
21 views

Is a negative pH value possible? [duplicate]

Is a negative pH value possible in room temperature...teachers don't tend to teach about the pH of acid or base solutions which are higher than 1M.
4
votes
2answers
92 views

Chemical kinetics of a reversible reaction

I am having trouble with the following question: Consider the following reversible reaction in which the reaction is first order in both directions: $$\ce{[A] <=> [B]}$$ $k_a$ is the rate ...
2
votes
2answers
43 views

Entropy change in an adiabatic expansion

The following is a question on a problem sheet that I have been given; I don't know what to do: "One mole of ideal gas initially at a pressure of 1 atmosphere and T = 298 K, is expanded into a ...
2
votes
1answer
29 views

Activated complex theory vs. consecutive reactions [duplicate]

Activated complex theory, tells us that due to the collision between the molecules of the reactants, they form a transition specie before the product is formed, which is called active complex. On the ...
5
votes
1answer
204 views

Why does Thallium form TlF and TlF3 but aluminium only forms AlF3?

Does this have something to do with the inert pair effect?
4
votes
1answer
31 views

Order of reactions in kinetics

In kinetics, zero order reactions are those reactions who are independent from the concentration of the reactant or the product. So their rate is equal to the constant k. But still we build the ...
2
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0answers
24 views

Dissociation Energy for CO2 per molecule

I'm trying to calculate the energy required to dissociate a single $\ce{CO_{2}}$ molecule into its respective elements, and I'm given that it takes $ 373.6 \times 10^{3} \, \, \frac{joules}{gram} $ ...
0
votes
0answers
22 views

What is the exact size of N-Carbamoyl beta-Alanine? (MWt-132.118) (MF- C4H8N2O3) [closed]

I would like to know the exact size of N-Carbamoyl beta-Alanine? (MWt-132.118) (chemical formula - $\ce{C4H8N2O3}$).
2
votes
1answer
36 views

How important are those fields of chemistry in biotechnology and medicinal chemistry

At my university there is some fields of chemistry that i don't know if i should focus on them... How important are in biotechnology and medicinal chemistry those fields of chemistry? : Quantum ...
4
votes
1answer
27 views

Is it possible to predict the lines in the atomic emission spectrum of Na?

The atomic emission spectrum for sodium ($\ce{Na}$) is completely dominated by a line in the range of yellow, about $590~\mathrm{nm}$ (to be more precise, it's a doublet). Here is how it looks like: ...
3
votes
0answers
49 views

theoretical model for the Hydrogen bond

I am curious how from the perspective of quantum chemistry the Hydrogen bond is modeled. In particular I am interested in using such a model to estimate the amount of energy released per $\ce{H2O}$ ...
1
vote
2answers
60 views

Can chemicals change crystal structure by only touching?

Are there any known, or suspected compounds that take the crystal structure of what ever object they are touching, i.e. if it touches $\ce{NaCl}$ it would turn into a face centered cubic crystal ...
10
votes
1answer
466 views

Why can't helium be solidified at 'ordinary' pressures?

According to the UC Davis ChemWiki Chemistry of Helium, helium has a comparatively unusual property, specifically: Helium is the only element that cannot be solidified by lowering the temperature ...
4
votes
1answer
49 views

Equation for heat loss over distance?

Is there an equation to figure out what the temperature of an the area will be a certain distance from the heat source? For example, If I know there is a heat source at $0~\mathrm{m}$, and the ...
5
votes
1answer
31 views

Name for analog of salt hydrate with non-water solvents?

Salts can bind with some water to form hydrates. For example, we can call $\ce{CoCl_2\cdot 6H_2O}$ cobalt chloride hexahydrate. There is no reason that water should be the only solvent that can bind ...
3
votes
2answers
56 views

Dependence of change in entropy on temperature

The thermodynamic definition of entropy is expressed as $$dS = \frac{dq_{rev}}{T}$$ I understand that it depends on amount of heat transferred because heat transfer can be understood as the degree of ...
3
votes
1answer
40 views

Why the dilution of solvent doesn't affect the solid phase, in comparison to the liquid phase?

Dilution of the solvent adds new energy states to the liquid, but does not affect the solid phase. The above line appeared on the following page under the section "5: Colligative properties and ...
3
votes
1answer
32 views

Activation energy and temperature

It is said that activation energy does not change with temperature. But I am unable to figure out why. If we increase the temperature, the kinetic energy of the molecules will increase and they will ...
13
votes
1answer
160 views

Do only outer electron shells take part in forming chemical bonds?

Do only outer electron shells take part in forming chemical bonds? Or could an inner shell create a bond under some conditions?
2
votes
1answer
35 views

How does an electrolyte react to voltages below its electrolysis potential?

An electrolyte can be electrolysed by a voltage higher than the reverse reaction’s cell potential, while conducting a current in the process. But what happens at the electrodes when the applied ...
2
votes
1answer
64 views

Calculating pH of an unknown base, and the pKb

The percent dissociation of a base $\ce{X}$ in a $0.002\ \mathrm{M}$ solution is $4.7 \cdot 10^{-3}\ \%$. What is the pH of the solution and what is the $\mathrm{p}K_\text{b}$ of base $\ce{X}$? The ...
4
votes
1answer
31 views

When is phosphorus a polyatomic molecule?

Phosphorus is listed as a single element in the periodic table; however, I see that it is also a polyatomic molecule as $\ce{P4}$. I am trying to determine the number of atoms of phosphorus in an ...
3
votes
6answers
1k views

Why is the melting of ice a spontaneous reaction?

So here's my question: we know that melting of ice is an spontaneous reaction but is it spontaneous? We have to supply energy in the form heat for the reaction to take place.
9
votes
1answer
405 views

Why does sunlight cause colors to fade?

If you leave something outside, its colors seem to inevitably fade or bleach due to exposure. Is this due to UV absorption? What sort of mechanism causes this - is it that man-made dyes deform on a ...
0
votes
1answer
15 views

Determining enthalpy of neutralization and heat capacity of calorimeter by overlying with straight lines or “eye-o-metric method”

Below is a model example of how to interpret gathered data. Temperature on y-axis, time on x-axis. We are supposed to read (temperature change by neutralization) and (temperature change by resistive ...
4
votes
1answer
36 views

Charge consistency in fragment qm/mm methods

I'm calculating the multipole moments on several fragments of a molecule. What are some procedures to ensure that the charges etc are representative of the complete molecule? How do I ensure I'm not ...