Listerine mouthwash is 21.6%ethyl alcohol by

Question

volume. What mass of ethanol is contained
in 20.0 mL of mouthwash? (The density of
ethanol is 0.789 g/mL.)
Answer in units of grams

Answer 1

% w/v; for 21.6% that means 21.6g/100 mL.
(g/20) = 0.216
Solve for grams.