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JEE Main levelSingle correct optionDifficulty 2 of 3qc013

$Zn X^{2 +}$ is not precipitated when $H X_{2} S$ is passed into a solution containing dilute $HCl$ , because

A $Zn X^{2 +}$ is reduced to $Zn$ by $H X_{2} S$
B $ZnS$ has a smaller $K_{s p}$ than $CuS$
Cthe ionic product $[Zn X^{2 +}] [S X^{2 -}]$ remains below $K_{s p}$ of $ZnS$ at the low $[S X^{2 -}]$ in acid
D $Zn X^{2 +}$ forms a stable chloro-complex that does not react with $H X_{2} S$

Answer: C

The

[S X^{2 -}]

is suppressed by

H X^{+}

, and

ZnS

has a comparatively large

K_{s p}

so the ionic product stays below it.

CuS

has a far smaller

K_{s p}

, so the third option is wrong, and

Zn X^{2 +}

is not reduced by

H X_{2} S

.

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