The number of molecules of hydrogen that will be required to react completely with 0.600 mol of O2 is calculated as follows
equation for reaction
2H2+O2 = 2H2O
by use of mole ration of H2 to O2 (2:1) the moles of H2 = 0.600 x2 = 1.2 moles
by use of Avogadro law that is 1 mole = 6.02 x10^23 molecules what about 1.2 moles
= 1.2 moles x (6.02 x10^23)/ 1mole= 7.224 x10^23 molecules