JEE Main · 2025 · 02 Apr 2025 · Shift 1 · Equilibrium

If equal volumes of

AB X_{2}

and XY (both are salts) aqueous solutions are mixed, which of the following combination will give a precipitate of

AY X_{2}

at 300 K?
(Given

K_{s p}

(at 300 K) for

AY X_{2} = 5.2 \times 1 0^{- 7}

)

Answer: (C)

Solution

Mixing equal volumes halves every concentration, and

AY X_{2}

precipitates once the ionic product

[A X^{2 +}] [Y X^{-}]^{2}

exceeds the solubility product

5.2 \times 1 0^{- 7}

. Taking

2.0 \times 1 0^{- 2} M

AB X_{2}

with

2.0 \times 1 0^{- 2} M

XY, the mixed concentrations are

[A X^{2 +}] = 1.0 \times 1 0^{- 2} M

and

[Y X^{-}] = 1.0 \times 1 0^{- 2} M

, so the ionic product is

(1.0 \times 1 0^{- 2}) (1.0 \times 1 0^{- 2})^{2} = 1.0 \times 1 0^{- 6}

. This exceeds the solubility product, while every other pairing falls below it, so precipitation occurs for the pair of

2.0 \times 1 0^{- 2} M

solutions.

JEE Main · 2025 · 02 Apr 2025 · Shift 1 · Single correct option