Question

Indicate which of the substance/ion in the following reaction is an oxidising agent and which is a reducing agent?
$2C{u}^{2+}+4I^{-}\to 2CuI+I_2$.

Answer 1

$2C{u}^{2+}+4I^{-}\to 2CuI+I_2$.
Oxidising agent- $C{u}^{2+}$ The oxidation number of Cu decreases from +2 to +1. Thus, Cu itself is reduced.
Reducing agent- $I^{-}$. The oxidation number of I increases from -1 to 0. Thus, I itself is oxidised.

Note:
Any species that is oxidised acts as reducing agent.
Any species that is reduced acts as oxidising agent.