H_{2} + O_{2} -> H_{2}O 2H_{2} + O_{2} -> 2H_{2}O 4H + O_{2} -> 2H_{2}O H_{2} + O -> H_{2}O
I gave my students this multiple choice question: Which equation is correctly balanced for hydrogen and oxygen reacting to form water?

Only one answer is correct among these 4 choices:
- H_{2} + O_{2} -> H_{2}O
- 2H_{2} + O_{2} -> 2H_{2}O
- 4H + O_{2} -> 2H_{2}O
- H_{2} + O -> H_{2}O

Could you tell me which one is correct?

2H_{2} + O_{2} -> 2H_{2}O