To find the molar mass, what we do is to follow the steps:
1. Make use of the chemical formula to determine the number of atoms of each element in the compound.
2. Multiply the molar mass of each element with its number of atoms present in the compound.
3. Add up all and assign unit as grams/mole.
In this problem, the molecule of water contains 2 atoms of Hydrogen and 1 atom of Oxygen.
The molar mass of Hydrogen is about 1g/mol and the molar mass of Oxygen is about 16g/mol, so:
Therefore, the answer is 18 g/mol.