Final answer:
The expression for Kp for the given reaction is Kp = (p[Fe₃O₄])*(p[H₂]⁴) / (p[H₂O]⁴).
Step-by-step explanation:
The expression for Kp for the given reaction can be determined by writing the equilibrium constant expression as the ratio of the partial pressures of the products and reactants, each raised to its coefficient in the balanced equation.
3 Fe(s) + 4 H₂O(g) ↔ Fe₃O₄(s) + 4 H₂(g)
The expression for Kp is:
Kp = (p[Fe₃O₄])*(p[H₂]⁴) / (p[H₂O]⁴)