The equilibrium: `2Cu^(1) Leftrightarrow Cu^0+ Cu^(u)` in aqueous medium at `25^@C` shifts towards the left in the presence of

Options

A. ` NO^(-)`
B. `Cl^(-)`
C. `SCN^(-)`
D. `CN^(-)`

Answer

B, C, D

Explanation

Cu (I) forms insouble compounds CuCl, CuCN and CuSCN. Hence , in the presence of `C1^(-) , CN^(-) and SCN^(-)` , the equilibrium shifts in the back direction .
In fact, `Cu^(2+) " ions combine with " CH^(-) and SCN^(-)` to form compunds which are not stable and disociate to form `Cu^(+)` compounds/ complexes
` Cu^(2+) + 2 CN^(-) to Cu(CN)^(2)` ltbr ` Cu(CN)_(2) to 2 CuCN + (CN)_(2)`
` CuCN + 3 CN^(-) to [Cu (CN)_(4)]^(3-)`
` Cu^(2) + 4 SCN^(-) to [Cu(SCN)_(4) ]^(2-)`
Similarly , `Cu^(2+) ` also combines with `Cl^(-)` ions to form `CuCl_(2)` which reacts with Cu to form CuCl, therby , shifting the equilibrium in the backward direction `CuCl_(2) + Cu to 2 CuCl`