Question

A solution is 40% ethanol (density = 0.789 g/mL) by volume and 60% water (density = 1.00 g/mL). If Tom Titan has 750.0 mL of the solution, what is the mass of ethanol in solution?

Answer 1

% ethanol (v/v) = volume of ethanol * 100 / volume of solution

40 = volume of ethanol * 100 / 750.0 mL

volume of ethanol = 300 mL

volume of water = volume of solution - volume of ethanol

= 750 mL - 300 mL

= 450 mL

density of ethanol = 0.789 g/mL

So,

mass of ethanol =density of ethanol* volume of ethanol

= 0.789 g/mL * 300 mL

= 236.7 g

density of water = 1.00 g/mL

So,

mass of water =density of water* volume of water

= 1.00 g/mL * 450 mL

= 450 g

total mass of solution = mass of ethanol + mass of water

= 236.7 g + 450 g

= 687 g

Answer: 687 g