Question

Consider a gaseous mixture consisting of 5 kmol of H2 and 3 kmol of O2. Determine the H2 and O2 mole fractions, the molecular weight of the mixture, and the H2 and O2 mass fractions

Answer 1

Answer:

Mole fraction H2: 0.625

Mole fraction O2: 0.375

Molecular weight: 13.25g/mol

Mass fraction H2: 0.094

Mass fraction O2: 0.906

Explanation:

Moles fraction is defined as the ratio between moles of a substance and total moles presents in a mixture:

Mole fraction H2 = 5kmol / (5kmol + 3kmol) = 0.625

Mole fraction O2 = 3kmol / (5kmol + 3kmol) = 0.375

Molecular weight is defined as the mass per mole of substance:

Mass H2 = 5kmol * (2kg / kmol) = 10kg

Mass O2 = 3kmol * (32kg / kmol) = 96kg

Molecular weight:

106kg / 8kmol = 13.25g/mol

In the same way, mass fraction is the ratio between mass of a substance and total mass of the mixture:

Mass fraction H2 = 10kg / (10kg + 96kg) = 0.094

Mass fraction O2 = 96kg / (10kg + 96kg) = 0.906