Write the expression for the equilibrium constant Kp for the following reaction. (Enclose pressures in parentheses and do NOT write the chemical formula as a subscript. For example, enter (PNH3)2 as (P NH3)2. If either the numerator or denominator is 1, please enter 1.) PCl5(g) ↔ PCl3(g) Cl2(g)

Answer and Explanation:

For the following balanced reaction:

PCl₅(g) ↔ PCl₃(g) + Cl₂(g)

We can see that all reactants and products are gases, so it is an homogeneous equilibrium. The expression for the equilibrium constant Kp can be written from the partial pressures (P) of reactants and products as follows:

Where PPCl₃ is the partial pressure of PCl₃ (reactant), PCl₂ is the partial pressure of Cl₂ (reactant) and PPCl₅ is the partial pressure of PCl₅ (product).