The word chemical equation for the reaction between ammonia gas and oxygen to produce nitrogen monoxide and water can be written as follows:
Ammonia gas + Oxygen gas → Nitrogen monoxide gas + Water vapor
In a more structured format, it can be presented as:
Ammonia + Oxygen → Nitrogen monoxide + Water
If you need the balanced chemical equation as well, it would be:
\[ 4 \text{NH}_3(g) + 3 \text{O}_2(g) \rightarrow 2 \text{NO}(g) + 6 \text{H}_2\text{O}(g) \]
This shows the stoichiometry of the reaction.