Question

What evolves $CO_2$ when Hydrochloric acid is added to it?

Answer 1

An acid is any hydrogen-containing substance that's capable of donating a proton (hydrogen ion) to a different substance. A base may be a molecule or ion ready to accept a proton from an acid. Acidic substances are usually identified by their sour taste. Acids are known to show blue litmus red.

Complete answer:
Carbon dioxide is evolved when acid is added to carbonate.
Carbon dioxide is the gas that evolves when acid and carbonate react. Carbonate may be a metal carbonate that reacts with Hydrochloric acid.
The solubility of $CO_2$ in aqueous Hydrochloric acid and $NaHCO_3$ solutions has been determined by the coulo-metric technique at ambient pressure and at 278, 283, 287, and 298 K. The error in Carbon dioxide solubility in Hydrochloric acid solutions estimated from parallel experiments was about 0.3%.
When an acid reacts with a metal carbonate a salt, Carbon dioxide and water are formed. Acid reacts with carbonate to make salt, carbon dioxide and water.
Carbon being non-metallic features a tendency to simply accept electrons. It's unable to displace hydrogen present in acid. Thus, it doesn't react with dilute acid.

Note:
Bubble the gas through lime water. The foremost effective test for carbon dioxide is to bubble the gas through "lime water", a diluted solution of lime (slaked lime). Once you bubble carbon dioxide through the answer, it forms a solid precipitate of carbonate – chalk or limestone.