Question

Which one of these ionic salts has the lowest molar solubility in water?

(a) CdCO3 (Ksp = 1.8x10–14)

(b) HgBr2 (Ksp = 1.3x10–19)

(c) Ce(OH)3 (Ksp = 6x10–22)

(d) La2(C2O4)3 (Ksp = 1x10–25)

(e) ThF4 (Ksp = 2.5x10–31)

Answer 1

answer : (a) CdCO3 (Ksp = 1.8x10–14)

solution :

(a) CdCO3 (Ksp = 1.8x10–14)

Ksp   = S^2

1.8 x 10^-14 = S^2

S = 1.34 x 10^-7 M

(b) HgBr2 (Ksp = 1.3x10–19)

Ksp = 4 S^3

1.3 x 10^-19 = 4 S^3

S = 3.19 x 10^-7 M

(c) Ce(OH)3 (Ksp = 6x10–22)

Ksp = 27 S^4

6 x 10^-22 = 27 S^4

S = 2.17 x 10^-6 M

(d) La2(C2O4)3 (Ksp = 1x10–25)

Ksp = 108 S^5

1 x 10^-25 = 108 S^5

S = 3.92 x 10^-6 M

(e) ThF4 (Ksp = 2.5x10–31)

Ksp = 256 S^5

2.5 x 10^-31 = 256 S^5

S = 2.5 x 10^-7 M