Observe the figure and answer the following questions :[Figure: a big test tube on a stand with a two-holed cork; a thistle funnel enters it and reaches the sodium carbonate placed at the bottom; a gas delivery tube carries the gas to a small test tu…

Answer: (a) Carbon dioxide (CO₂); (b) lime water turns milky; (c) \(\mathrm{2CH_3COOH + Na_2CO_3 \rightarrow 2CH_3COONa + H_2O + CO_2\uparrow}\).

(a) Acetic acid reacts with sodium carbonate and carbon dioxide gas is released, which is seen as brisk effervescence in the big test tube.

(b) The gas passes into freshly prepared lime water, which turns milky because insoluble calcium carbonate is formed: \(\mathrm{Ca(OH)_2 + CO_2 \rightarrow CaCO_3\downarrow + H_2O}\).

(c) Balanced equation for the reaction in the big test tube:

\[\mathrm{2CH_3COOH + Na_2CO_3 \rightarrow 2CH_3COONa + H_2O + CO_2\uparrow}\]

(acetic acid + sodium carbonate → sodium acetate + water + carbon dioxide)