The solubility product of Mg(OH)2 is 1.0× 10-12. Concentrated aqueous NaOH solution is added to a 0.01 M aqueous solution of MgCl2. The pH at which precpitation occurs is

Question

The solubility product of Mg(OH)2 is 1.0× 10-12. Concentrated aqueous NaOH solution is added to a 0.01 M aqueous solution of MgCl2. The pH at which precpitation occurs is (A) 7.2 (B) 7.8 (C) 8.0 (D) 9.0

Tardigrade Admin · Accepted Answer

For the reaction, Mg(OH)2 leftharpoons Mg2+ + 2OH- Ksp=[Mg2+][OH-]2 10-12=(0.01)[OH-]2 (10-12/10-2)=[OH-]2 ∴ [OH-]=10-5 ⇒ pOH=+5 Also, pH + pOH = 14 pH = 14 - pOH 14 - 5 = 9

Q. The solubility product of $M g (O H)_{2}$ is $1.0 \times 1 0^{- 12}$ . Concentrated aqueous $N a O H$ solution is added to a $0.01 M$ aqueous solution of $M g C l_{2}$ . The $p H$ at which precpitation occurs is

7.2

7.8

8.0

9.0

For the reaction,
$M g (O H)_{2} ⇌ M g^{2 +} + 2 O H^{-}$
$K_{s p} = [M g^{2 +}] [O H^{-}]^{2}$
$1 0^{- 12} = (0.01) [O H^{-}]^{2}$
$\frac{1 0 ^{- 12}}{1 0 ^{- 2}} = [O H^{-}]^{2}$
$∴ [O H^{-}] = 1 0^{- 5}$
$\Rightarrow pO H = + 5$
Also, $p H + pO H = 14$
$p H = 14 - pO H$
$14 - 5 = 9$

Q. The solubility product of Mg(OH)2​ is 1.0×10−12. Concentrated aqueous NaOH solution is added to a 0.01M aqueous solution of MgCl2​. The pH at which precpitation occurs is

7.2

7.8

8.0

9.0

For the reaction, Mg(OH)2​⇌Mg2++2OH− Ksp​=[Mg2+][OH−]2 10−12=(0.01)[OH−]2 10−210−12​=[OH−]2 ∴[OH−]=10−5 ⇒pOH=+5 Also, pH+pOH=14 pH=14−pOH 14−5=9

Q. The solubility product of $M g (O H)_{2}$ is $1.0 \times 1 0^{- 12}$ . Concentrated aqueous $N a O H$ solution is added to a $0.01 M$ aqueous solution of $M g C l_{2}$ . The $p H$ at which precpitation occurs is

For the reaction,
$M g (O H)_{2} ⇌ M g^{2 +} + 2 O H^{-}$
$K_{s p} = [M g^{2 +}] [O H^{-}]^{2}$
$1 0^{- 12} = (0.01) [O H^{-}]^{2}$
$\frac{1 0 ^{- 12}}{1 0 ^{- 2}} = [O H^{-}]^{2}$
$∴ [O H^{-}] = 1 0^{- 5}$
$\Rightarrow pO H = + 5$
Also, $p H + pO H = 14$
$p H = 14 - pO H$
$14 - 5 = 9$