[Roger]

Given reaction Gibbs energy, Δ_rG, for a specified temperature, how can I find the total pressure of the reaction that had to be used to get this value of Δ_rG?
 
I am given the chemical reaction, and can compute, if necessary, Δ_rG^θ, Δ_rH^θ, and Δ_rS^θ. What are the steps I need to take to compute the total reaction pressure, what is the relationship between Δ_rG and total reaction pressure? Thanks very much.

[Hunt]

I think you're still trying to solve that ammonia synthesis problem you posted earlier , aren't you ? There is a way to establish delta G^o as a function of the total pressure. This isn't what you need though .

e^{-deltaG^o/RT} = K_x / P^2 ( where the standard pressure = 1 bar ... )

K_x = eq mol fractions of species
P = total pressure

For your previous problem you need to look at the graphs given to you inorder to find the total pressure at a specific temp.

The problem states , "Isotherms of ΔrG(T, p) in the pressure range 100atm <= p <= 400atm are needed to derive the answer."