Agallon 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

210. moles To determine the number of moles of a substance you have, simply divide the mass of the substance you have by its molar mass. So 3.79 kg / 18.02 g/mol = 3790 g / 18.02 g/mol = 210.3218646 mol Since we only have 3 significant figures, the answer should be rounded to 3 figures, giving 210. as the result. Notice that the decimal point is required. If you state the number of moles is 210, then that answer will only have 2 significant figures. But the value of 210. has 3 significant figures.

The population of unionid mussels decreased after zebra mussels were introduced. zebra mussels competed with the unionid mussels for food. the zebra mussels were able to displace the unionid mussels, allowing the zebra mussel population to increase  over the years. the unionid mussel population decreased because  of lack of food.