What Is the Law of Mass Action in Thermal Physics?

[WWCY]

Homework Statement

Hi all, I am having issues with the following problem. Assistance is greatly appreciated!

Homework Equations

The Attempt at a Solution

a) The "law of mass action" I know of is just the equilibrium constant, which I wrote in terms of partial pressures at equiilbrium
$$K = \frac{P_{N_2}^2 P_{H_2 0}^6 }{ P_{std} P_{NH_3}^4 P_{O_2}^3 }$$

b) I don't understand the problem here, what does it mean to "find all the constituents"?

c) I was thinking of attempting to obtain an expression for partial pressures at equilibrium, in terms of the individual partition functions. However, I don't think this is at all an efficient way of working it out. There is another equation
$$K = e^{-\Delta _r G_0 / RT}$$
but the change in molar Gibbs function at standard temperature and pressure is given by a sum over chemical potentials evaluated at standard and pressure (with some coefficients), which when expressed as partition functions seem rather complicated.

 

[haruspex]

what does it mean to "find all the constituents"?

Just a guess, but could it mean to include intermediate products?

 

[WWCY]

Just a guess, but could it mean to include intermediate products?

What does it mean to include intermediate products? Apologies but I'm not familiar with chemical reactions

 

[Chestermiller]

Pstd should be in the numerator, not the denominator.

 

[WWCY]

Would it be alright if perhaps someone assisted me with c) instead of b)? I'll have to get my instructor to tell me what's going on in part b.

Thanks!

 

[Chestermiller]

Would it be alright if perhaps someone assisted me with c) instead of b)? I'll have to get my instructor to tell me what's going on in part b.

Thanks!

I can help you with part b. Suppose you had a mixture of the four species that was not at equilibrium, and you knew the total pressure and the mole fractions of the four species in this initial state. Assuming that the reaction took place at constant total pressure, would you be able to determine the mole fractions (or partial pressures) of the four species when equilibrium was attained?

 

[Borek]

what does it mean to "find all the constituents"?

Find amounts (concentrations, partial pressures, whatever) of all substances present.

 

[WWCY]

Thanks for the replies, I'll have to give this a bit of a think as I'm not well acquainted with the topic yet.