How many moles of O2 are produced when 0.86 moles of H2O is reacted?

I'm learning about the periodic tables and what each subject's configuration is. for example, hydrogen is 1s^1, but i don't understand how you get that. can someone me understand how to figure out how to figure this out? sorry if the question makes no sense, but it would really a lot if you could me understand! you so much if you can!

Which three statements represent the benefits of performing experiments using computer simulations?

Gasoline has a density of 0.740 g/ml. if you have 328 grams of gasoline, what is the volume in milliliters?