Formic acid reduces Tollen's reagent, but acetic acid does not-Give reasons.

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`