Identify the oxidant and reductant in the following reactions:
`10H^(+)(aq)+4Zn(s)+NO_3^(-) (aq)to4Zn^(2+) (aq)+NH_4^(+) +3H_2O(l)`

Explanation

Writing the oxidation number of all the atoms above their symbols, we have
`overset(+1) 10H^(+)(aq)+overset0 4Z(s)+overset(+5)(NO_3^(-))(aq) to overset(+2)(4Zn^(2+))(aq)+overset(-3)(NH_4^(+))+overset(+1)(3H_2) overset(-2)O(l)`
Oxidation number of Zn changes from zero in Zn to +2 in `Zn^(2+)` and therefore, it is oxidized and hence Zn acts as a reductant.
THe oxidation number of N decrease from +5 in `NO_3^(-)` to -3 to `NO_4^(+)` and therefore, it is reduced and hence `NO_3^(-)` acts as the oxidant.