Which of the following cannot function as an oxidising agent?

Identify the reducing agent in the following chemical equations:
$4Ag(s) + 8CN^{-}(aq) + 2H_{2}O(aq) + O_{2}(g) \rightarrow 4[Ag(CN)_{2}]^{-}(aq) + 4OH^{-}(aq)$
$2[Ag(CN)_{2}]^{-}(aq) + Zn(s) \rightarrow [Zn(CN)_{4}]^{2-}(aq) + 2Ag(s)$

$HNO_2$ acts both as a reductant and an oxidant,while $HNO_3$ acts only as an oxidant. This is due to their:

For the given reaction,which of the following is not used to change the colour of the solution from orange to green?
$K_2Cr_2O_7 / H^{+} + y \to Cr^{+3} + \text{Others}$
$(\text{orange}) \quad \quad \quad (\text{green})$

In the reaction $Ag_2O + H_2O_2 \to 2Ag + H_2O + O_2$,the $H_2O_2$ acts as

The oxidant which is used as an antiseptic is: