Measured values are verified and go under a series of experiments before being accepted as the norm. Accepted values are unanimously accepted values, seen as the norm by a qualified group of individuals (scientists or the people of the intellectual sphere).
To find the amount of moles in a molecule you divide the grams of the substance by the molar mass.
molar mass of CO2 = 44.01 g
22g / 44.01 = 0.50 moles CO2
True. But it is not entirely fool proof.