What is the mass of `0.5` mole of water `(H_(2)O)`.
(Atomic masses : `H = 1 u, O = 16 u`)

Explanation

In order to solve this problem, we should know the mass of 1 mole of water. This can be obtained by using the given values of the atomic masses of hydrogen and oxygen as follows :
`1` mole of water ` (H_(2)O)` = Molecular mass of `H_(2)O` in grams
= Mass of 2H atoms + Mass of H atom
`= 2 xx 1 + 16`
`= 2 + 16`
`= 18` grams
Thus, the mass of 1 mole of water is 18 grams.
Now, Mass of 1 mole of water `= 18` g
So, Mass of `0.5` mole of water `= 18 xx 0.5 g`
`= 9 g`
Thus, the mass of 0.5 mole of water `(H_(2)O)` is `9` grams.