Question

Find out the solubility product of CaF₂ if solubility of CaF₂ is 2.34 g/100 mL

(a) 0.108 (mol/L)³

(b) 0.072 (mol/L)³

(c) 0.036 (mol/L)³

(d) 0.032 (mol/L)³

Answer 1

(a) 0.108 (mol/L)³

Solubility = 2.34/100 g/ml

Molar mass of CaF₂ = 40 + 19 + 19 = 78 g/ml

Solubility in (mol/L = 2.34/78 x 1000/100 mol/L = 0.3mol / L

CaF₂ \(\rightleftharpoons\) Ca²⁺ + 2F^-

s   2s

K_sp = s x (2s)² = 4 s³

K_sp = 4 x (0.3)³ = 0.108 (mol/L)³