A mouthwash is 38.1% ethanol by mass. If each bottle contains 1.040 pints of mouthwash with a density of 0.851 g/mL, how many kilograms of ethanol are in 160 bottles of the mouthwash

Total mass of mouthwash = volume*density

1 pint is 568.261 mL therefore 1.040 pints = 591.0 mL (4 significant figures)

Therefore mouthwash mass in a bottle = 591.0 mL * 0.851 g/mL = 503 g (3 s. f.)

In 160 bottles, ethanol mass = 509 g * 160 * 0.381 = 30700 g = 30.7 kg