Question

the h2 is highly combustible gas and o2 is use for burn and how they formed h2O water

Answer 1

Answer:

when hydrogen and oxygen combine by electrolysis at high temperature and pressure they form water

Answer 2

Explanation:

This is a basic fact, that the properties of a compound are different from the properties of its component elements. This can be seen from the example of water. While Hydrogen burns with a pop sound, and Oxygen is a supporter of combustion, after they combine, they form the compound water, which is used for extinguishing fire.