Question

Give one chemical test each to distinguish between the following pairs of compounds:
(1) Ethanol and acetic acid
(2) Acetaldehyde and benzaldehyde

Answer 1

(i)Acetic acid being acidic reacts with carbonates or bicarbonates to give brisk effervescence due to the evolution of carbondioxide whereas ethanol does not react.

$C{H}_{3}COOH+{Na}_{2}C{O}_3\to C{H}_{3}COONa+H_{2}O+C{O}_2\uparrow$

(ii) Fehling's solution test is used to distinguish between acetaldehyde and benzaldehyde as:

acetaldehyde gives red precipitate of cuprous oxide while benzaldehyde does not.

$C{H}_{3}CHO+{5OH}^{-}+2{Cu}^{2+}\to C{H}_{3}CO{O}^{-}+{Cu}_{2}O\downarrow +3H_{2}O$