Question

Hydrogen gas for fuel can be made through the catalyzed reaction of methane gas and steam. Calculate the minimum temperature required for this reaction to achieve an equilibrium constant of unity (K = 1) using only the following information:

A) ∆H˚rxn - can be calculated from bond energy (bond enthalpy) values as given in the following table of data:

Bond Bond Energy (kJ mol-1)

H-H 436

H-C 414

H-O 464

C=O 799

B) ∆S˚rxn for this reaction can be calculated from the following ∆S˚ values (J K-1) at 298K:

C(s, graphite) + 2H2(g) -> CH4(g) ∆S˚ = -80.8

C(s, graphite) + O2(g) -> CO2(g) ∆S˚ = 2.9

H2(g) + 1/2O2(g) -> H2O(g) ∆S˚ = -44.5

C) Using the above two values, calculate ∆G˚ for this reaction, and the corresponding reaction equilibrium constant at 298K.

D) Assuming that ∆H˚rxn and ∆S˚rxn are independent of temperature, calculate the temperature (in K) required for this reaction to have K = 1.

I have done part A and B and I found that ∆H˚rxn is 170 kJ/mol. ∆S˚rxn is 11.1 J/K. ∆G˚ is 166.5 kJ/mol. I just can't figure out the constant, k, for the reaction which is CH4 + 2H2O -> 4H2 + CO2

Answer 1