What is the chemical potential of a diatomic gas in equilibrium?

In summary, the conversation discusses finding the chemical potential of atoms and molecules, using the equation $$\mu_{A_2}+\mu_{A}=0$$ and the Gibb's condition. It is determined that the relation between the chemical potentials of atoms and diatomic molecules is $$2\mu_{A}=\mu_{A_2}$$.
  • #1
Diracobama2181
75
2
Homework Statement
Consider the formation of diatomic molecules $$A_2$$ out of atoms $$A$$. Assume that the binding energy of the molecule is $$I$$, i.e., the difference in internal energy between a molecule and a pair of atoms is $$−I$$. Show that in the limit when the atoms and molecules may be regarded as classical ideal gases, except for the formation of the molecules, the equilibrium densities of the atoms and molecules satisfy $$\frac{nA_2}{n_ A^2} = √ 8λ 3 Ae I kT $$.
Relevant Equations
$$\mu_{A_2}+\mu_{A}=0$$
It is my assumption that I need to find the chemical potential of the atoms $$\mu_A$$ and for the molecules $$\mu_{A_2}$$,
then use $$\mu_{A_2}+\mu_{A}=0$$ to arrive at the given identity. For $$\mu_A$$, I found that $$\mu_A=k_BTln(n_A\lambda ^3)$$, where
$$n_a=\frac{N_a}{V}$$ and $$\lambda$$ is the thermal wavelength. My question is, how would I go about find $$\mu_{A_2}$$? I know I can find it using the partition function. But I am unsure what that would be in this case. Any advice helps. Thanks
 
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  • #2
8λ3AeIkT

I suspect some sub/superscripts were needed here?
 
  • #3
I don't understand your question. You have an equation relating ##\mu_A## and ##\mu_{A_2}##.

Note however that that equation is incorrect.
 
  • #4
Yes, the equation should actually read $$\frac{n_{A2}}{(n_A)^2}=√8λ^3e^{\frac{I}{kT}} $$. Apologies.
 
  • #5
DrClaude said:
I don't understand your question. You have an equation relating ##\mu_A## and ##\mu_{A_2}##.

Note however that that equation is incorrect.
I'm essentially trying to use the Gibb's condition ($$dG=0$$) to find how the chemical potential of the diatomic molecules relates to that of the atoms.
 
  • #6
Diracobama2181 said:
I'm essentially trying to use the Gibb's condition ($$dG=0$$) to find how the chemical potential of the diatomic molecules relates to that of the atoms.

What is the stoichiometry of the reaction?
 
  • #7
DrClaude said:
What is the stoichiometry of the reaction?
Two atoms create one molecule. So would the relation be $$2\mu_{A}=\mu_{A_2}$$?
 
  • #8
Diracobama2181 said:
Two atoms create one molecule. So would the relation be $$2\mu_{A}=\mu_{A_2}$$?
Yes.
 

Related to What is the chemical potential of a diatomic gas in equilibrium?

1. What is a diatomic gas?

A diatomic gas is a type of gas molecule that consists of two atoms of the same element bonded together. Examples include oxygen (O2), nitrogen (N2), and hydrogen (H2).

2. How does a diatomic gas reach equilibrium?

A diatomic gas reaches equilibrium when the rate of forward reactions (dissociation into individual atoms) is equal to the rate of reverse reactions (recombination into diatomic molecules). This results in a constant concentration of both diatomic molecules and individual atoms.

3. What factors affect the equilibrium of a diatomic gas?

The equilibrium of a diatomic gas can be affected by changes in temperature, pressure, and the presence of catalysts. An increase in temperature or pressure will shift the equilibrium towards the dissociation of diatomic molecules, while a decrease in temperature or pressure will shift the equilibrium towards recombination. Catalysts can also affect the rate of both forward and reverse reactions, thus altering the equilibrium.

4. What is the significance of diatomic gas equilibrium in industrial processes?

Diatomic gas equilibrium is important in many industrial processes, such as combustion, chemical synthesis, and gas separation. Understanding and controlling the equilibrium allows for the optimization of these processes, resulting in higher efficiency and yield.

5. How is diatomic gas equilibrium represented mathematically?

The equilibrium of a diatomic gas can be represented by the equilibrium constant, K. For a general reaction of A2 <=> 2A, the equilibrium constant is defined as [A]^2 / [A2], where [A] represents the concentration of individual atoms and [A2] represents the concentration of diatomic molecules. A larger K value indicates a higher concentration of diatomic molecules at equilibrium, while a smaller K value indicates a higher concentration of individual atoms.

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