Question

How can I balance this equation? ____ H2 + ____ O2 ---> ____ H2O

Answer 1

The answer is:

`H_2 + 1/2O_2 -> H_2O`

Cut the equation in half:

Reactants
H - 2
O - 2

Products
H - 2
O - 1

`O_2` is one oxygen molecule - there is only one oxygen atom in `H_2O`. So, in order to balance it, put a `1/2` next ox `O_2` - half of `O_2` is `O_1` (`O`) i.e. - one oxygen atom.