Question

Write a chemical test to distinguish between the following pair of compounds:

Acetic acid and benzaldehyde

Answer 1

1. Sodium Bicarbonate (NaHCO₃) Test: Acetic acid (a carboxylic acid) reacts with sodium bicarbonate to produce brisk effervescence due to the evolution of carbon dioxide gas. Benzaldehyde (an aldehyde) does not react.

\[\ce{CH3COOH + NaHCO3 -> CH3COON + H2O + \underset{effervescence}{\underset{Brisk}{CO2}}}\]

2. Tollen’s Test (Silver Mirror Test): Benzaldehyde reacts with Tollen’s reagent to form a shiny silver mirror on the inner walls of the test tube. Acetic acid does not react.

\[\ce{C6H5CHO + 2[Ag(NH3)2]^+ + 3OH^- -> C6H5COO^- + \underset{Silver Mirror}{2Ag↓} + 4NH3 + 2H2O}\]