Question

Solubility product constants (K_sp) of salts of types MX, MX₂, M₃X at temperature T are 4 × 10^–8, 3.2 × 10^–14 and 2.7 × 10^–15 respectively. Solubility (moldm^–3) of the salts at temperature T are in the order –

• A. MX > MX₂> M₃X
• B. M₃X > MX₂> MX
• C. MX₂> M₃X > MX
• D. MX > M₃X > MX₂

Answer 1

Answer: (D)

MX > M₃X > MX₂

Answer 2

Solubility (S₁) of

MX = $\sqrt { \mathrm { K } _ { \mathrm { sp } } } = \sqrt { 4 \times 10 ^ { - 8 } }$ = 2 × 10^–4 M

Solubility (S₂) of

MX₂ = $\left( \frac { \mathrm { K } _ { \mathrm { sp } } } { 4 } \right) ^ { 1 / 3 } = \left( \frac { 3.2 \times 10 ^ { - 14 } } { 4 } \right) ^ { 1 / 3 }$ = 2 × 10^–5 M

Solubility (S₃) of

M₃X = $\left( \frac { \mathrm { K } _ { \mathrm { sp } } } { 27 } \right) ^ { 1 / 4 } = \left( \frac { 2.7 \times 10 ^ { - 15 } } { 27 } \right) ^ { 1 / 4 }$ = 10^–4 M

\ S₁ > S₃ > S₂