A gallon of water has a mass of 3.79 kg. how many moles of water (18.02 g/mol) is this?

First, we will convert the mass of the gallon to grams:

a gallon of water has a mass of 3.79 * 1000 = 3790 grams of water

number of moles can be calculated using the following rule:

number of moles = mass / molar mass

Therefore,

number of moles = 3790 / 18.02 = 210.32 moles