# Question b1cb9

Aug 22, 2016

Do you mean calcium oxide and water, by any chance?

#### Explanation:

I don't think that calcium oxide, $\text{CaO}$, reacts with hydrogen gas, ${\text{H}}_{2}$, so I'm going to assume that you want to know about the reaction between calcium oxide and water, $\text{H"_2"O}$.

Calcium oxide, also called quicklime, will react with water to form calcium hydroxide, "Ca"("OH")_2, also called slacked lime.

"CaO"_ ((s)) + "H"_ 2"O"_ ((l)) -> "Ca"("OH")_ (2(s))#

Calcium hydroxide is relatively soluble in water, but the amount that does dissolve dissociates completely to produce a basic solution of $\text{pH} \approx 12$.

It's worth mentioning that this reaction is quite exothermic, meaning that heat is being given off as calcium hydroxide is produced by the reaction.