Chemistry help..what is she saying?

Question

My teacher is telling me to adjust both sides of the equation. For example: a) there are 2 H and 2 O --> there are 2 H and 1 O to make this equation balanced you would have to have 4H and 2O on the left side --> which make 2 H2O.

My answer was H2 + O2  ---> H2O ---> 2H2O. And it was incorrect, where do I put the 4 ?

Answer 1

She means that both sides of the equation must be balanced.

H2 + O2 ---> H2O

Note that there are 2 oxygens on the reactant side, but only one on the product side. Therefore, put a 2 in front of the H2O.

H2 + O2 ---> 2H2O

Now, the oxygens are balanced. However, there are 4 hydrogens on the product side and only 2 on the reactant side. Thus, put a 2 in front of the H2 to give 4 hydrogens.

2H2 + O2 ---> 2H2O

If you notice, everything is now balanced! 4 hydrogens and 2 oxygens on both sides.

Hope I helped! :)