The mass of water is 18.87kg.
1st) It is necessary to convert the 5.00 gal into mL, knowing that 1 gal is equal to 1 qt, and 1 L is equal to 1.057 qt. Then we convert the L into mL:
2nd) Now, with the formula of density, we can calculate the mass of water replacing the values:
3rd) Finally, it is necessary to convert the grams into kg:
So, the mass of water is 18.87kg.