Question

When hydrochloric gas is passed over calcium carbonate, the gas evolved is

• A. Carbon monoxide
• B. Carbon dioxide
• C. Hydrogen

Answer 1

The correct option is B

Carbon dioxide

The explanation for the correct option

Option B Carbon dioxide:

• There is a release of carbon dioxide gas with brisk effervescence.
• In the chemical reaction between hydrochloric acid and calcium carbonate, there is a formation of calcium chloride, carbon dioxide gas, and water; ${\mathrm{CaCO}}_3+2\mathrm{HCl}\to {\mathrm{CaCl}}_2+{\mathrm{H}}_2\mathrm{O}+{\mathrm{CO}}_2\uparrow$
• There is a release of carbon dioxide gas with brisk effervescence.

The explanation for incorrect options

Option A: Carbon monoxide forms with the formation of incomplete combustion of substance in the presence of less oxygen.

Option C: Hydrogen gas is released when metals react with acids. The hydrogen gas produces a pop sound when passes through a burning match stick.
Hence, the correct option is option B Carbon Dioxide.