The reaction of hydrogen gas ( ext{H}_2) with oxygen gas ( ext{O}_2) to form liquid water ( ext{H}_2 ext{O}) can be represented by the following balanced chemical equation:
2 H2 + O2 → 2 H2O
This equation indicates that two moles of hydrogen gas react with one mole of oxygen gas to produce two moles of liquid water. It is important to note that this reaction is exothermic, meaning it releases heat, but the energy term has been excluded in this representation as per your request.