Final answer:
To find the mass of 20.00 moles of water, multiply the number of moles by the molar mass of water (18.015 g/mol), resulting in 360.3 grams. The closest answer is 360.0 grams.
Step-by-step explanation:
To calculate the mass of 20.00 moles of water (H2O), we use the molar mass of water as a conversion factor. The molar mass of water is approximately 18.015 g/mol, calculated by adding the atomic masses of hydrogen and oxygen (2 x 1.0079 + 15.9994 = 18.0152 g/mol).
Using this molar mass, we can convert moles to grams:
20.00 moles H2O x 18.015 g/mol = 360.3 grams
Therefore, 20.00 moles of water is equivalent to 360.3 grams, which we can round to 360.3 g for simplicity. Thus, the answer closest to this calculation would be option (A) 360.0 g, as it is the typical practice to report the mass to one decimal place when dealing with measurements on this scale.