Answer: The mass of water required will be 18 grams.
Step-by-step explanation:
For the given chemical reaction:

By Stoichiometry of the reaction:
1 mole of calcium oxide reacts with 1 mole of water.
So, 1 mole of calcium oxide will react with =
mole of water.
To calculate the mass of water required, we use the equation:

We are given:
Moles of water = 1 mole
Molar mass of water = 18 g/mol
Putting values in above equation, we get:

Hence, the mass of water required will be 18 grams.