Question

Can we make water by adding hydrogen and oxyzen? If yes then why there is a scarcity of water.

Answer 1

Yes, we can prepare water by adding O₂ and H₂ but for this we required presence of free hydrogen gas in atmosphere.
H₂ does not found in our environment because H₂ gas is very light and earth's gravitational force is not that strong to keep it in earth's environment. However, water can be prepared through various other technique but these methods are quite expensive and will not be economically beneficial for industry or government.