#### Answer

355 mL of mouthwash has 79.9 mL of alcohol

#### Work Step by Step

$22.5\%$ (v/v) $ alcohol $ solution : $$ 22.5 \space mL \space alcohol = 100 \space mL \space solution$$
$$355 \space mL \space solution \times \frac{22.5 \space mL \space alcohol}{100 \space mL \space solution} = 79.9 \space mL \space alcohol $$