Q. $H_{2}S$ is passed into one $dm^{3}$ of a solution containing $0.1\ mole\ of\ Zn^{3}\ and\ 0.01\ mole\ of\ Cu^{2}$ till the sulphide ion concentration reaches $8.1\ \ 10^{10}$ moles. Which one of the following statements is true? [$K_{sp}\ of\ Zn\ and\ CuS\ are\ 3\ \ 10^{22}\ and\ 8\ \ 10^{36}\$ $respectively\rbrack$
A) Only $ZnS$ precipitates
B) Both $CuS\ and\ ZnS\ precipitates$
C) $Only\ CuS\ precipitates$
D) No precipitation occurs
Explanation
(b)
$\left\lbrack Zn^{2 +} \right\rbrack\left\lbrack S^{2 -} \right\rbrack = 10^{- 1} \times 8.1 \times 10^{- 19} = 8.1 \times 10^{- 20} > K_{sp}of\ ZnS\ (3 \times 10^{- 22})$
$\left\lbrack {Cu}^{2 +} \right\rbrack\left\lbrack S^{2 -} \right\rbrack = 10^{- 2} \times 8.1 \times 10^{- 19} = 8.1 \times 10^{- 21} > K_{sp}of\ CuS\ (8 \times 10^{- 36})\$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.