find molality and mass percent?

Question

A bottle of wine contains 12.3% ethanol by volume. The density of ethanol (C2H5OH) is 0.789 g/cm3. Calculate the concentration of ethanol in wine in terms of mass percent and molality.

mass percent?

molality?

Answer 1

Assume that there is no volume change by mixing water and ethanol at this specific ratio.
For 1 L of this wine, it contains:
12.3%*1000ml = 123 ml of ethanol, or
123ml * 0.789 g/cm3 = 97.0 g of ethanol, or
97.0g/(46.0684g/mol) = 2.11 mole of ethanol, and:
877ml or 877g of water
So the mass percent is: 97.0g /(97.0g + 877g) = 9.96%
And the molality: 2.11*(1000/877) = 2.40 m