Final answer:
To calculate equilibrium constants (K) for reactions, one must consider the concentrations of the involved substances. If gases are involved, K can also be expressed in terms of partial pressures (Kp). For solids and liquids, their concentrations are included in the equilibrium constant as they remain constant.
Step-by-step explanation:
The question pertains to writing the equilibrium constant expressions for different chemical reactions. When dealing with equilibrium reactions, the equilibrium constant K is calculated by taking the product of the concentrations of the products, each raised to the power of its stoichiometric coefficient, and dividing by the product of the concentrations of the reactants, also raised to the power of their respective coefficients. The equilibrium constant for gas phases can also be expressed in terms of partial pressures, and this is represented by Kp. For solid and liquid phases, their concentrations are considered constant and amalgamated into K or Kp.
- For reaction PCl3(l) + Cl2(g) = PCl5(s), the expression for K would be K = [PCl5] / ([PCl3] x [Cl2]), where [x] denotes concentration; however, for solids, their concentration is constant and typically amalgamated into K, simplifying this to K = 1 / ([PCl3] x [Cl2]).
- For reaction Fe3O4(s) + 4H2(g) = 3Fe(s) + 4H2O(g), the expression for K is K = ([Fe]^3 x [H2O]^4) / ([H2]^4), where for solids, the concentration is constant and included in K.