Question

Which gas is liberated when dilute hydrochloric acid reacts with sodium carbonate? How will you test for the presence of this gas?

Answer 1

When dilute hydrochloric acid reacts with sodium carbonate, then sodium chloride, carbon dioxide and water are formed.

\[\ce{\underset{Sodium carbonate}{Na2CO3_{(s)}} + \underset{Hydrochloric acid}{2HCl_{(aq)}} -> \underset{Sodium chloride}{2NaCl_{(aq)}} + \underset{dioxide}{\underset{Carbon}{CO2_{(g)}}} + \underset{Water}{H2O_{(l)}}}\]

The reaction between dilute hydrochloric acid and sodium carbonate can be performed as follows:

1. Take a boiling tube and put about 0.5 g of sodium carbonate in it.
2. Add about 2 mL of dilute hydrochloric acid to the boiling tube (through a thistle funnel as shown in the figure).
3. We will observe brisk effervescence of a gas.
4. Pass the gas through lime water. The lime water turns milky (showing that it is carbon dioxide gas).
5. Keep passing carbon dioxide gas through milky lime water for a little longer. The lime water becomes clear again. This shows that the white precipitate of calcium carbonate dissolves on passing an excess of carbon dioxide gas.