Final answer:
The equilibrium constant expression for the reaction is Kc = [Pb²+][Cl⁻]².
Step-by-step explanation:
The equilibrium constant expression for the given reaction is Kc = [Pb²+][Cl⁻]². The equation represents the molarities of the species involved in the reaction at equilibrium. The coefficient in front of Cl⁻ is 2 because it is produced in a 1:2 ratio with Pb²+.