Which expression is Ksp for dissolution of solid PbCl₂ in water?

A) moles of solid / liter of water

B) 1 / ([Pb²⁺][Cl⁻]²)

C) [Pb²⁺][Cl⁻]²

D) [Pb²⁺][Cl⁻]

Answer: C

Explanation: Write dissolved-ion concentrations multiplied with exponents from the dissolution stoichiometry. The pure solid has constant activity and does not appear in Ksp.