Question

Name the gas evolved when dilute HCl reacts with sodium hydrogen carbonate. How is it recognised?

Answer 1

• When dilute hydrochloric acid reacts with sodium hydrogen carbonate, carbon dioxide gas is evolved.
• The reaction is as follows:

$NaHC{O}_3+HCl\to NaCl+H_{2}O+C{O}_2$

• On passing $C{O}_2$ through lime water, it turns milky.

$Ca{\left(OH\right)}_2\left(aq\right)+C{O}_2\left(g\right)⟶CaC{O}_3\left(s\right)+H_{2}O\left(aq\right)$

• Hence, the gas evolved is carbon dioxide.