Listerine mouthwash is 21.6% ethyl alcohol by volume. What mass of ethanol is contained in 20.0 mL of mouthwash? (The density of ethanol is 0.789 g/mL.)

Question

Answer in units of grams

Answer 1

21.6% EtOH means 21.6 g EtOH/100 mL solution; therefore, 20 mL will contain
21.6g x (20 mL/100 mL) = about 4 mL EtOH but you should be more accurate than that.
Then mass = volume x density.
You have volume and density, solve for mass.