Question

what is equation to show how water is formed from its constituent elements

Answer 1

Answer:

2 H$_{2}$ + 0$_{2}$ ----> 2 H$_{2}$O  

The above is the balanced equation for the reaction of hydrogen and oxygen to form water.

Answer 2

Explanation:

2 H2 + O2 gives 2H2O

Verification:

The left hand side contains 4 Hydrogen and 2 oxygen molecules in total and the same on the right hand side