When ammonium chloride (NH₄Cl) and sodium nitrate (NaNO₃) are heated together, the gas evolved is nitrogen monoxide (NO), also known as nitric oxide.

Here's the balanced chemical equation for the reaction:

NH₄Cl + NaNO₃ → NaCl + 2H₂O + NO

The reaction is a redox reaction where ammonium chloride acts as a reducing agent and sodium nitrate acts as an oxidizing agent.

Explanation:

* Ammonium chloride (NH₄Cl) decomposes into ammonia (NH₃) and hydrogen chloride (HCl) upon heating.

* Sodium nitrate (NaNO₃) decomposes into sodium nitrite (NaNO₂) and oxygen (O₂).

* The ammonia (NH₃) reacts with the oxygen (O₂) to form nitrogen monoxide (NO) and water (H₂O).

* The hydrogen chloride (HCl) reacts with the sodium nitrite (NaNO₂) to form sodium chloride (NaCl) and nitrous acid (HNO₂).

Note: The reaction is complex and may produce other products depending on the reaction conditions.