When potassium hydroxide (KOH) and calcium carbonate (CaCO₃) are mixed, the following reaction occurs:

2KOH + CaCO₃ → K₂CO₃ + Ca(OH)₂ + H₂O

The gas produced in this reaction is carbon dioxide (CO₂) .

Here's a breakdown:

* Potassium hydroxide (KOH) is a strong base.

* Calcium carbonate (CaCO₃) is a carbonate salt.

* Potassium carbonate (K₂CO₃) and calcium hydroxide (Ca(OH)₂) are the products formed.

* Water (H₂O) is also produced.

The reaction is a double displacement reaction, and the CO₂ gas is released as a byproduct of the reaction.