Question

MY and NY₃, are insoluble salts and have the same K_sp values of 6.2 × 10⁻¹³ at room temperature. Which statement would be true with regard to MY and NY?

Options

• The salts MY and NY₃ are more soluble in 0.5 M KY than in pure water

• The addition of the salt of KY to the suspension of MY and NY₃ will have no effect on their solubility’s

• The molar solubilities of MY and NY₃ in water are identical

• The molar solubility of MY in water is less than that of NY₃

Answer 1

The molar solubility of MY in water is less than that of NY₃

Explanation:

Addition of salt KY (having a common ion Y^–) decreases the solubility of MY and NY₃ due to common ion effect.

Option (a) and (b) are wrong.

For salt MY,

\[\ce{MY ⇌ M^+ + Y^-}\]

K_sp = (s) (s)

6.2 × 10⁻¹³ = s²

∴ s = `sqrt(6.2 xx 10^-13)` ≃ 10⁻⁷

for salt NY₃,

\[\ce{NY3 ⇌ N^{3+} + 3Y^-}\]

K_sp = (s) (3s)³

K_sp = 27s⁴

s = `((6.2 xx 10^-13)/27)^(1/4)`

s ≃ 10⁻⁴

The molar solubility of MY in water is less than of NY₃