You are studying the formation of HI(g) from its gaseous elements H2(g) and I2(g). The free energy of formation of HI(g) is –10.10 kJ/mol at 500 K. When the free energy change of the process at 500 K is zero, the reaction mixture shows partial pressures of HI and I2 as 10.0 atm and 0.001 atm, respectively. What must be the partial pressure of H2 at this time?

Answer 1

I would do this.
dG = -RTlnK
Substitute and solve for K.

Then K = p^2HI/pH2*pI2
Substitute and solve for pH2

Answer 2

Okay, I did the equation and I got P H2 : 881.06 atm. That seems very high. Where did I make a mistake?

Thank you for your help.