Question

Formic acid and acetic acid are distinguished by

• A. ${\mathrm{NaHCO}}_3$
• B. ${\mathrm{FeCl}}_3$
• C. Victor Mayer test
• D. Tollen's reagent

Answer 1

The correct option is D

Tollen's reagent

The explanation for the correct answer

Option (D) Tollen's reagent

• Tollen's reagent is used for the identification of aldehydes.
• Formic acid ($\mathrm{HCOOH}$) and acetic acid (${\mathrm{CH}}_3\mathrm{COOH}$) can be distinguished by Tollen's reagent.
• In formic acid, there is a presence of the aldehyde group.
  
• The reaction of formic acid and Tollen's reagent
  $\underset{\mathrm{Formic}\mathrm{acid}}{\mathrm{HCOOH}}+\underset{\mathrm{Tollen}\text{'}\mathrm{s}\mathrm{reagent}}{[\mathrm{Ag}{\left({\mathrm{NH}}_3\right)}_2{]}^{+}}+\underset{\mathrm{Hydroxide}\mathrm{ion}}{2{\mathrm{OH}}^{-}}\to 2\underset{\mathrm{Silver}\mathrm{Mirror}}{\mathrm{Ag}}+\underset{\mathrm{Carbon}\mathrm{dioxde}}{{\mathrm{CO}}_2}+\underset{\mathrm{Water}}{2{\mathrm{H}}_2\mathrm{O}}+\underset{\mathrm{Ammonia}}{4{\mathrm{NH}}_3}$
• Aldehyde group reduces Tollen's reagent to silver mirror
• In acetic acid, there is the presence of the carboxylic group and the carboxylic group is not able to reduce Tollen's reagent.

The explanation for the incorrect answer
Option (A) ${\mathrm{NaHCO}}_3$

Both formic acid and acetic acid can react with ${\mathrm{NaHCO}}_3$ in a similar manner.

Option (B) ${\mathrm{FeCl}}_3$

Both formic acid and acetic acid can react with ${\mathrm{FeCl}}_3$in a similar manner.

Option (C) Victor Mayer test

Victor Mayer test is for the identification of alcohol.

Hence, to distinguish between acetic acid and formic acid Tollen's reagent is used.