Question

For the theoretically perfect reaction 2H2 + O2 -----> 2H2O, if you react 300 molecules of hydrogen and 200 molecules of oxygen, how many oxygen molecules will you have that do not engage in the reaction?

Answer 1

Since the ratio of H2 to O2 is 2:1, only 150 molecules of O2 will get in the chemical reaction while 50 molecules will remain as excess.