Question

A solution is prepared by adding 60 g of methyl alcohol to 120 g of water. Calculate the total mole fraction of methanol.

Answer 1

Mass of methanol $=$ 60 g
Moles of methanol $=\frac{60}{32}=1.875$
(molar mass $=$ 32)
Mass of water $=$ 120 g
Moles of water $=\frac{120}{18}=6.667$
(Molar mass $=$ 18)
Total number of moles $=$ 1.875+6.667
$=$ 8.542
Mole fraction of methanol
$=\frac{1.875}{8.542}=0.220$
Mole fraction of water
$=\frac{6.667}{8.542}=0.780$