Question

Solubility product helps to predict the precipitation of salts from solution. 

1. Find the relation between solubility (S) and solubility product (K_sp) of calcium fluoride and zirconium phosphate. 

2. The solubility product of two sparingly soluble salts XY₂ and AB are 4 × 10^-15 and 1.2 × 10^-16 respectively. Which salt is more soluble? Explain.

Answer 1

1. The equilibrium in the saturated solution of calcium fluoride can be represented as,

CaF₂(s) ⇌ Ca²⁺(aq) + 2F^- (aq) 

K_sp = [Ca²⁺][F^-]² = S.(2S)₂ = 4S³ 

The equilibrium in the saturated solution of zirconium phosphate can be represented as,

Zr₃ (PO₄)₄(s) ⇌ 3Zr⁴⁺ (aq) + 4PO₄^3- (aq) 

K_sp = [Zr⁴⁺ ]³ [PO₄^3- ]⁴ = (3S)³ .(4S)⁴ = 6912 S⁷

2. XY₂ is more soluble than AB.