Which action would help reduce global warming

If 1.8 l of water is added to 2.5l of a 7.0 m koh solution, what is the molarity of the new solution

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!

If 16.00g of hydrogen gas reacts with 126.73g of oxygen, how many grams of water are yielded? (both reactants are completely consumed in the reaction.)