Question

___ H2 + ___ O2 → ___ H2O

Answer 1

Your answer mate:

2H2+O2--->2H2O

Answer 2

Answer:

Step-by-step explanation:

With  O 2 on the left side the right side will need to have an even multiple of H 2 O  to balance the oxygen.

This means that there will be 4 times some multiple of hydrogen on the right side.

The simplest way to to have 4 times a multiple of hydrogen from the let side using H 2  is with 2 H 2.