A compound X' of sodium is used as an antacid and it decomposes on strong heating. Give one use of compound X' besides being an antacid.

As we know that;

1. Antacids are the compounds that are used to neutralize hydrochloric acid (HCl) in gastric secretions.
2. The compounds which are used as antacids are sodium hydrogen carbonate$\left({\mathrm{NaHCO}}_3\right)$, aluminum hydroxide$\left(\mathrm{Al}{\left(\mathrm{OH}\right)}_3\right)$, calcium carbonate$\left({\mathrm{CaCO}}_3\right)$, etc.
3. The compound that decomposes on strong heating is Sodium Bicarbonate $\left({\mathrm{NaHCO}}_3\right)$
4. Therefore, the compound ‘X’ is Sodium Bicarbonate which is also known as baking soda.

Reaction involved:

$\underset{\mathrm{Sodium}\mathrm{bicarbonate}}{2{\mathrm{NaHCO}}_3(\mathrm{s}})\stackrel{\mathrm{\Delta }}{\to }\underset{\left(\mathrm{Sodium}\mathrm{carbonate}\right)}{{\mathrm{Na}}_2{\mathrm{CO}}_3\left(\mathrm{s}\right)}+\underset{\left(\mathrm{Water}\right)}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}+\underset{\left(\mathrm{Carbon}\mathrm{dioxide}\right)}{{\mathrm{CO}}_2\left(\mathrm{g}\right)}$

Use of the compound ‘X’:

It can be used as a fire extinguisher because the sulphuric acid present in the cylinder mixes with sodium hydrogen carbonate solution to produce carbon dioxide gas which acts as a blanket around the burning substance that cuts off the air supply(O₂) to the burning substance and fire gets extinguished.

Therefore, the use of the compound ‘X’ besides being an antacid is a fire extinguisher.