Questions tagged [chemistry]

Questions related to mathematical chemistry which include application of mathematics to problems in chemistry and the development of mathematical methods suitable for such applications and for the formulation of chemical theories

200 questions
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(Organic) Chemistry for Mathematicians

Recently I've been reading "The Wild Book" which applies semigroup theory to, among other things, chemical reactions. If I google for mathematics and chemistry together, most of the results are to do with physical chemistry: cond-mat, fluids, QM of…
27
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4 answers

Balance chemical equations without trial and error?

In my AP chemistry class, I often have to balance chemical equations like the following: $$ \mathrm{Al} + \text O_2 \to \mathrm{Al}_2 \mathrm O_3 $$ The goal is to make both side of the arrow have the same amount of atoms by adding compounds in the…
Chao Xu
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Why can't we remove the sqrt from rms?

In chemistry, we define the root-mean-square speed as $\sqrt{\bar{u^2}}$ = $\sqrt{\frac{3\text{RT}}{\text{M}}}$ A student asked me why we can't just remove the square root symbol. And aside from "because this is how we define it", I didn't actually…
J M
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An application of the Inclusion Principle to Chemistry? (Proof Verification)

Background I’m taking chemistry and one thing they have us do is draw Lewis structures for molecules. Guessing if there are going to be double or triple bonds is kind of annoying. I’d like to be able to come up with a formula to predict the total…
10
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1 answer

Why is $\arccos(-\frac 13)$ the optimal angle between bonds in a methane ($\rm CH_4$) molecule?

Background: In a CH4 molecule, there are 4 C-H bonds that repel each other. Essentially the mathematical problem is how to distribute 4 points on a unit sphere where the points have maximal mutual distance - or, how to distribute 4 position vectors…
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Application of Combinatorics/Graph Theory to Organic Chemistry?

Recently, I have been self-teaching graph theory and having an organic chemistry course at school. When I was learning isomer enumeration I found great resemblance between organic molecules and graphs. Every atom can be regarded as a vertex, with…
Colescu
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Asimov quote about "eight million trillion" arrangements of amino acids

A friend of mine is subediting a book whose author died in 1999. The author, at some point, uses the word "trillion" which is, unfortunately, an ambiguous word in the UK: when I was at school it used to mean $10^{18}$ but nowadays it means…
Kevin Buzzard
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7
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Solving two electron integral

During one of my practical courses we had to do the Hartree-Fock-method "by hand". Part of that was to calculate the occurring two electron integrals. With $$\chi_i(r) = 2 \cdot \alpha_i^{3/2} e^{-\alpha_i r} Y_0^0$$ we were given the following…
6
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mathematics of chemical stoichiometry

I would like to better understand the mathematical description of chemical stoichiometry and thermodynamic chemical equilibrium. This problem has many features and I know my description might be too vague. There are generally two approaches to the…
6
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Deconvolution of distribution of diffraction reflexes

I'm a chemist stuck in a mathematical problem. Please bear with me as I'm trying to express myself in Math language. Let me explain in short terms the experimental method I'm using: X-ray diffraction. For this method, atoms in a solid can be viewed…
6
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1 answer

Determining whether or not a system of equations has positive integer solutions

Consider the chemical reaction: $$ \mathrm{ClO_3} + \text I_2 \to \mathrm{Cl} + \mathrm {IO_3} $$ When given the reaction in a test, I did not know whether I was meant to balance it by manipulating the coefficients or to balance it using chemical…
Fouad Saffar
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6
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How many different isomers of $C_3 H_4 Cl_2 F_2$ exist?

I was on my high school chemistry class when I came across this problem, which, I think, belongs to group theory. The problem is that it is not possible to label the carbons as reflection should not be counted twice. (That is,…
5
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1 answer

Geometry and chemistry

There's a really obvious geometric reason why the cosine of the bond angle in graphite is $-1/2$: the stuff consists of sheets shaped like honeycombs. There's also a really obvious geometric reason why the cosine of the bond angle in methane is…
Michael Hardy
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Balancing chemical equations - Matrix determinant is zero for specific reaction

I am currently working on a program which takes a chemical equation as input and returns the balanced chemical equation instead. It finds the appropiate chemical coefficients with matrix operations, using the formula $x = A^{-1}b$. I am using JAMA…
5
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3 answers

What happen to units when we take Ln?

What happens to units when we take the Ln of the both side of the equation? For example for an equation $PV^k = C$ (which becomes $\ln P = -k \ln V + \ln C$), how can we find the units of $k$ and $C$? -->(the unit of $P$ is mmHg and the unit of $V$…
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