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General Principles and processes of Isolation of Elements
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When $ZnS$ and $PbS$ minerals are present together, then $NaCN$ is added to separate them in the froth floatation process as a depressant, because
A
$Pb(CN)_2$ is precipitated while no effect on $ZnS$
B
$ZnS$ forms soluble complex $Na_2[Zn\,(CN)_4]$
C
$PbS$ forms soluble complex $Na_2[Pb\,(CN)_4]$
D
They cannot be separated by adding $NaCN$
Solution
$ZnS\, + \,4NaCN\, \rightleftharpoons \,4N{a^ + }\, + \,\mathop {{{\left[ {Zn{{\left( {CN} \right)}_4}} \right]}^{2 – }}}\limits_{{\text{water soluble}}} + {S^{2 – }}$
Standard 12
Chemistry
