Final answer:
The equilibrium constant expression depends on the states of the reactants and products; solids and liquids do not appear in the expression. Kc and Kp are calculated using concentrations and partial pressures of gaseous and aqueous species, respectively, raised to the power of their coefficients.
Step-by-step explanation:
The equilibrium constant expression, Kc, for the reaction PC1₃ (l) + Cl₂ (g) — PCl₅ (s) is
Kc = [PCl₅] / ([PCl₃] * [Cl₂])
However, in this case, since PCl₅ is a solid, its concentration does not appear in the expression. Therefore, the expression would simply be Kc = 1/([PCl₃] * [Cl₂]).
For the second reaction, Fe₃O₄ (s) + 4H₂ (g) — 3Fe (s) + 4H₂O (g), the equilibrium constant expression in terms of partial pressures (Kp) is:
Kp = (P_H₂O)^4 / (P_H₂)^4
Again, solids such as Fe₃O₄ and Fe do not appear in the equilibrium expression.
To find K or Kp for the above reactions, we write the equilibrium constant expression as the ratio of the concentrations (Kc) or partial pressures (Kp) of the products over reactants, each raised to the power of their stoichiometric coefficient in the balanced chemical equation.