Identify the redox reaction out of the following reactions and identify the oxidising and reducing agents in them.
(a) `3HCl_((aq))+HNO_(3(aq))toCl_(2(g))+NOCl_((g))+2H_(2)O_((l))`
(b) `HgCl_(2(aq))+2KI_((aq))toHgI_(2(s))+2KCl_((aq))`
( c) `Fe_(2)O_(3(s))+3CO_((g))overset(Delta)to2Fe_((s))+3CO_(2(g))`
(d) `PCl_((l))+3H_(2)O_((l))to3HCl_((aq))+H_(2)PO_(3(aq))`
(e) `4NH_(3(aq))+3O_(2(g))to2N_(2(g))+6H_(2)O_((g))`

Explanation

(a) `overset(-1)(3HCl_((aq)))+overset(+5)(HNO_(3(aq)))tooverset(0)(Cl_(2(g)))+overset(+3)(NOCl_((g)))+2H_(2)O_((l))`
Oxidation number of elements are change so this is redox reaction. HCl is reducing agent and `HNO_(3)` is oxidising agnet.
(b) `Hgoverset(-1)(Cl_(2(aq)))+overset(-1)(2KI_((aq)))toHgoverset(-1)(I_(2(s)))+2Koverset(-1)(Cl_((aq)))`
This is not redox reaction.
( c) `overset(+3)(Fe_(2))O_(3(s))+overset(+2)(3CO_((g)))tooverset(0)(2Fe_((s)))+overset(+4)(3CO_(2(g)))`
Oxidation number of oxygen is changed so this is redox reaction. CO is reducing agent and `Fe_(2)O_(3)` is oxidising agnet.
(d) `overset(+3)(P)overset(-1)(Cl_(3(l)))+3H_(2)O_((l))to3Hoverset(-1)(Cl_((aq)))+H_(2)overset(+3)(PO_(3(aq)))`
This reaction is not redox reaction.
(e) `overset(+3)(4NH_(3(aq)))+overset(0)(3O_(2(g)))tooverset(0)(2N_(2(g)))+6H_(2)overset(-2)(O_((g)))`
This is redox reaction. `O_(2)` is oxidising agnet `NH_(3)` is reducing agent.