Medium INTEGER +4 / -1 PYQ · JEE Mains 2021

The solubility product of PbI2 is 8.0 $\times$ 10$-$9. The solubility of lead iodide in 0.1 molar solution of lead nitrate is x $\times$ 10$-$6. mol/L. The value of x is __________. (Rounded off to the nearest integer) [Given $\sqrt 2$ = 1.41]

Answer (integer) 141

Solution

Given, ${[{K_{sp}}]_{Pb{l_2}}} = 8 \times {10^{ - 9}}$<br/><br/>To calculate solubility of Pbl<sub>2</sub> in 0.1 M solution of Pb(NO<sub>3</sub>)<sub>2</sub>,<br/><br/>(I) $$\mathop {Pb{{(N{O_3})}_2}}\limits_{0. 1 M} \to \mathop {P{b^{2 + }}(aq)}\limits_{0.1 M} + \mathop {2NO_3^ - (aq)}\limits_{0. 2 M} $$<br/><br/>(II) $Pb{I_2}(s)$ $\rightleftharpoons$ $\mathop {P{b^{2 + }}(aq)}\limits_S + \mathop {2{I^ - }(aq)}\limits_{2S}$<br/><br/>$\therefore$ [Pb<sup>2+</sup>] = S + 0.1 $\approx$ 0.1<br/><br/>$\because$ S < < 0.1<br/><br/>Now, K<sub>sp</sub> = 8 $\times$ 10<sup>$-$9</sup><br/><br/>[Pb<sup>2</sup>] [I<sup>$-$</sup>]<sup>2</sup> = 8 $\times$ 10<sup>$-$9</sup><br/><br/>0.1 $\times$ (2S)<sup>2</sup> = 8 $\times$ 10<sup>$-$9</sup><br/><br/>4S<sup>2</sup> = 8 $\times$ 10<sup>$-$8</sup> $\Rightarrow$ S = 141 $\times$ 10<sup>$-$6</sup> M<br/><br/>$\therefore$ x = 141

About this question

Subject: Chemistry · Chapter: Equilibrium · Topic: Chemical Equilibrium and Kc, Kp

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