Step-by-step explanation:
Calcium oxide absorbed moisture (water vapors ) from the air and forms calcium hydroxide as a product which why it is stored in dry place in a chemistry laboratory.
The chemical reaction between calcium oxide and moisture is given as:
![CaO+H_2O\rightarrow Ca(OH)_2](https://img.qammunity.org/2020/formulas/chemistry/college/615fj9xtwok54dsriauw6oyygyvlyck8kc.png)
According to stoichiometry, 1 mole of calcium oxide reacts with 1 mole of water vapors to give 1 mole of calcium hydroxide.