14. What is the mass of 3.5 moles of water?

To answer this you need to know the molar mass of water:

H = 1.0g/mol

O = 16.0g/mol

H2O (water) = 18.0g/mol

Then just multiply the molar mass by the number of moles to get the mass in grams.

Therefore 3.5 moles of water = 63.0g