I am having such a hard time approaching this problem. It would be great if you can help me.

1.0 mole of CH4 react with 1.0 mole of O2 in a sealed container. (a) When the reaction is complete, what is the container? (b) How many moles of water are produced?
CH4 + 2O2 ---> CO2 + 2H2O

a) CH4 + O2 ---> CO2 + H2O