Answer:
10.2 g
Explanation:
A mixture of ethyl alcohol (molecular mass = 46.1 u) and water (molecular mass = 18.0 u) contains one mole of molecules.
The mixture contains 20.0 g of ethyl alcohol. The molar mass of ethyl alcohol is 46.1 g/mol. The moles of ethyl alcohol are:
20.0 g × (1 mol / 46.1 g) = 0.434 mol
The sum of the moles of ethyl alcohol and the moles of water is 1 mole.
n(ethyl alcohol) + n(water) = 1 mol
n(water) = 1 mol - n(ethyl alcohol) = 1 mol - 0.434 mol = 0.566 mol
The molar mass of water is 18.0 g/mol. The mass of water is:
0.566 mol × (18.0 g/mol) = 10.2 g
