Question

The equilibrium $C{u}^0+C{u}^{II}\rightleftharpoons 2C{u}^I$
In aqueous medium at $25^{\circ }C$ shifts towards the left in the presence of
$1.C{l}^{-}2.C{N}^{-}3.SC{N}^{-}4.N{O}_3^{-}$

• A. $1,2$
• B. $2,3$
• C. $1,2,3$
• D. $2,3,4$

Answer 1

Answer: (C)

$C{u}^{2+}$ ions will react with $C{N}^{-}$and $SC{N}^{-}$ forming $[Cu(CN{)}_4{]}^{3-}$ and $[Cu(SCN{)}_4{]}^{3-}$ leading the reaction in the backward direction.
$C{u}^{2+}+2C{N}^{-}\to Cu(CN{)}_2$
$2Cu(CN{)}_2\to 2CuCN+(CN{)}_2$
$CuCN+3C{N}^{-}\to [Cu(CN{]}^{3-}$
$C{u}^{2+}+4SC{N}^{-}\to [Cu(SCN{]}^{3-}$
$C{u}^{2+}$ also combines with $CuC{l}_2$ which reacts with $Cu$ to produce $CuCl$ pushing the reaction in the backward direction.
$CuC{l}_2+Cu\to 2CuCl\downarrow$