Select reaction in which oxidation number of copper is not changed in final product:

Options

A. `CuSO_(4)` solution `overset(NaCN(aq)("Excess"))rarr`
B. `CuSO_(4)` solution `overset(KI ("Solution"))rarr`
C. `CuSO_(4)` solution `overset(S_(2)O_(3)^(2-)(aq) ("Excess"))rarr`
D. `CuSO_(4)` solution `overset(KOH ("Excess"))rarr`

Answer

D

Explanation

`Cu^(+2) +S_(2)O_(3)^(2-)rarr Cu^(+) + S_(4)O_(6)^(2-)`
`{:(Cu^(+)+S_(2)O_(3)^(2-)rarr,Cu_(2)S_(2)O_(3)darr("White ppt")),(," "darrExcess Na_(2)S_(2)O_(3)),(,underset(("Soluble and colourless"))([Cu_(6)(S_(2)O_(3))_(5)]^(-4)]):}`