How to Calculate the Mass & Mole Fractions of Methanol

Locate each of the elements that compose methanol on the periodic table, and record their molar masses. The molar mass of carbon is 12.01 g / mol, hydrogen is 1.008 g / mol, and oxygen is 16.00 g / mol.

Multiply the molar mass by the number of moles in the chemical formula. Since there is only one mole of carbon and one mole of oxygen in methanol, or CH3OH, then their molar masses can stay as they are. However, there are four moles of hydrogen, so multiply

1.008 g / mol by four. This gives you 4.032 g / mol.

Add the molar masses of the elements together. To find the mass of methanol, add

12.01 g / mol, 4.032 g / mol, and 16.00 g / mol. This gives you an answer of 32.04 g / mol.

Make ratios that relate the number of moles of each element to the moles of methanol. The mole fraction for carbon is 1 mole C / 1 mole CH3OH. The mole fraction of hydrogen is

4 moles H / 1 mole CH3OH. The mole fraction for oxygen is 1 mole O / 1 mole CH3OH.