In a 55.0-g aqueous solution of methanol, CH4O, the mole fraction of methanol is 0.320. What is the mass of each component?

Answer 1

Mole fraction CH3OH = 0.320

Mole fraction H2O = 0.680

Now convert to mass fraction or mass %

mass CH3OH = 0.320 x 32 g/mol = 10.2 g CH3OH

mass H2O = 0.680 x 18 g/mol = 12.2 g H2O

Total mass = 10.2 g + 12.2 g = 22.4 g

Mass fraction CH3OH = 10.2 g / 22.4 g = 0.455

Mass fraction H2O = 12.2 g / 22.4 g = 0.545

Mass CH3OH = 0.455 x 55.0 g = 25.0 g CH3OH

Mass H2O = 0.545 x 55.0 g = 30.0 g H2O