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.)
Answer in units of grams
% w/v; for 21.6% that means 21.6g/100 mL.
(g/20) = 0.216
Solve for grams.
To find the mass of ethanol in 20.0 mL of Listerine mouthwash, we need to multiply the volume of mouthwash by its alcohol concentration and the density of ethanol.
1. First, convert the volume of mouthwash from milliliters (mL) to liters (L). Since 1 L is equal to 1000 mL, divide 20.0 mL by 1000 to get:
20.0 mL ÷ 1000 = 0.0200 L
2. Now, multiply the converted volume (0.0200 L) by the alcohol concentration (21.6%) to find the volume of ethanol present in the mouthwash:
0.0200 L × 21.6% = 0.00432 L
3. Next, we need to find the mass of ethanol by multiplying the volume (0.00432 L) by the density of ethanol (0.789 g/mL):
0.00432 L × 0.789 g/mL = 0.00340 g
Therefore, the mass of ethanol contained in 20.0 mL of Listerine mouthwash is 0.00340 grams.