Account for reducing nature of Formic acid.

Explanation

(i) Formic acid (HCOOH) is unique because it contains both an aldehyde group and carboxyl group also.

(ii) Hence it can act as a reducing agent. It reduces Fehling's solution Tollen's reagent and decolourises pink coloured `KMnO_(4)` solution.
(iii) Whereas in acetic acid, there is no aldehyde group and it cannot act as reducing agent.
(iv) Formic acid reduces ammoniacal silver nitrate solution (Tollen's reagent) to metallic silver.
`HCOOH+Ag_(2)OtoH_(2)O+CO_(2)+2Agdarr` (metallic silver)
(v) Formic acid reduces Fehling's solution. It reduces blue coloured cupric ions to red coloured cuprous ions.
`HCOO^(-)+underset(("blue"))(2Cu^(2+))+5OH^(-)toCO_(3)^(2-)+underset("(red)")(Cu_(2)O)+3H_(2)O`