The equivalent factor used to convert molecules of oxygen to moles of oxygen is Avogadro's number which is 6.022 x10^23. We divide the given number of molecules by Avogadro's number to get the number of moles. In this case, 4.28 * 10^19 molecules divided by 6.022 x10^23 is equal to 7.11 x10^-5 moles.
