The balanced chemical equation for the reaction of hydrogen chloride gas with oxygen to produce water and chlorine gas is:

4 HCl (g) + O₂ (g) → 2 H₂O (g) + 2 Cl₂ (g)

Here's a breakdown of the equation:

* HCl (g) represents hydrogen chloride gas.

* O₂ (g) represents oxygen gas.

* H₂O (g) represents water vapor.

* Cl₂ (g) represents chlorine gas.

This equation is balanced because there are the same number of atoms of each element on both sides of the equation:

* Hydrogen (H): 4 on both sides.

* Chlorine (Cl): 4 on both sides.

* Oxygen (O): 2 on both sides.