The equation for the reaction between oxygen and hydrogen to form water is:

2 H₂ + O₂ → 2 H₂O

This means:

* 2 molecules of hydrogen (H₂) react with 1 molecule of oxygen (O₂) to produce 2 molecules of water (H₂O).

This is a highly exothermic reaction, meaning it releases a lot of energy in the form of heat and light. This is why it is often used in rocket engines.