Question

46 g ethanol is dissolved in 54 g water. Calculate mole fraction of ethanol and water.

Hint:

Mole fractions always add up to 1, and they are dimensionless quantities.

Answer 1

Moles of ethanol: \[ \text{Moles of ethanol} = \frac{\text{Mass}}{\text{Molar mass}} = \frac{46}{46} = 1 \, \text{mol}. \] Moles of water: \[ \text{Moles of water} = \frac{54}{18} = 3 \, \text{mol}. \] Mole fraction of ethanol: \[ \text{Mole fraction of ethanol} = \frac{\text{Moles of ethanol}}{\text{Total moles}} = \frac{1}{1+3} = 0.25. \] Mole fraction of water: \[ \text{Mole fraction of water} = 1 - 0.25 = 0.75. \]