How many of the following reagents is useful to distinguish between formic acid and acetic acid `NaHCO_3`, NaOH, Tollen's reagent, Fehlings solution , alk, `KMnO_4` , Metallic sodium , `I_2//NaOH`

Answer

3

Explanation

Due to presence of aldehyde group in formic acid `(H-overset(O)overset(||)C-OH)` it reduce tollens reagent , Fehling soln & Alkaline `KMnO_4` so, these three reagent are useful distinguishing of formic acid & acetic acid
`HCOO overset(KMnO_4)to CO_2, HCOOh overset(T.R)to ` White ppt, `HCOOH `overset(F.S)to ` red ppt