JEE MAIN - Chemistry (2021 - 1st September Evening Shift - No. 15)

The molar solubility of Zn(OH)2 in 0.1 M NaOH solution is x $$\times$$ 10$$-$$18 M. The value of x is _________ (Nearest integer)

(Given : The solubility product of Zn(OH)2 is 2 $$\times$$ 10$$-$$20)
Answer
2

Explanation

JEE Main 2021 (Online) 1st September Evening Shift Chemistry - Ionic Equilibrium Question 50 English Explanation

Due to common-ion effect (presence of NaOH) the concentration of OH$$-$$ will be (2S + 0.1) $$\approx$$ 0.1

($$\because$$ 0.1 > > 2 S)

$$\therefore$$ Solubility of product,

$${K_{sp}} = {(0.1)^2} \times S$$

$$2 \times {10^{ - 20}} = 0.01 \times S$$

$$ \Rightarrow S = {{2 \times {{10}^{ - 20}}} \over {0.01}} = 2 \times {10^{ - 18}}$$

$$\therefore$$ x = 2

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