Question

How many moles of Oxygen are needed to create 4.2 moles of water and you have excess Hydrogen?
O2 + 2H 2 -> 2H20

Answer 1

extremely simple according to the eq.
2 moles of water require only one mole of O2 thus
4.2 moles of water will require O2= 4.2*1/2 =2.1


thus 2.1 moles of O2 are required