Question

2H2O = 2H2+O2, How many moles of O2 will form when 1 mol of H2O reacts?

Answer 1

                                   2H2O = 2H2+O2
from reaction            2 mol               1 mol
from problem           1 mol              x mol

x=1*1/2= 0.5 mol O2 is formed when 1 mol of H2O reacts