Question

A few drops of ethanoic acid were added to solid sodium carbonate. The observation made was that :
(1) a hissing sound was produced
(2) brown fumes evolved
(3) brisk effervescence occurred
(4) a pungent smelling gas was evolved

Answer 1

When ethanoic acid reacted with solid sodium carbonate, it will give sodium carboxylate, water and carbon dioxide is eliminated. Elimination of carbon dioxide gives brisk effervescence.
$2{\mathrm{CH}}_3\mathrm{COOH}\left(\mathrm{aq}\right)+{\mathrm{Na}}_2{\mathrm{CO}}_3\left(\mathrm{s}\right)\to 2{\mathrm{CH}}_3\mathrm{COONa}\left(\mathrm{aq}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

Hence, the correct answer is option 3.