Question

$CaO + {H_2}O \to Ca{(OH)_2}$ is an example of a ______ reaction.

Answer 1

Hint : A combination reaction is a type of reaction in which two or more reactants react (combine) to form a single new compound which has different chemical properties than reactants. Also the chemical reaction in which heat is released is known as exothermic reaction while a chemical reaction in which heat is absorbed is known as endothermic reaction.

Complete Step By Step Answer:
The given chemical reaction is:
$CaO + {H_2}O \to Ca{(OH)_2}$
Here, $CaO$ is the chemical formula of Calcium oxide which is also known as Quick lime.
${H_2}O$ is the formula for water.
And, $Ca{(OH)_2}$ is a chemical formula of Calcium hydroxide which is also known as Slaked lime.
In the above reaction, we can see that two molecules or reactants ( $CaO$ and ${H_2}O$ ) are combining (reacting) together to form a single new compound $Ca{(OH)_2}$ . So, we know that, when two or more reactants react (combine) to form a single new compound which has different chemical properties than the initial reactants is known as combination reaction.
Also, when quick lime (calcium oxide) reacts with water to form slaked lime (Calcium hydroxide), it releases heat and hence it is an exothermic reaction.
So, we can conclude that the above reaction is an example of combination reaction as well as exothermic reaction.

Note :
There are mainly five types of reactions which are – Combination reaction, Decomposition reaction, Displacement reaction, Double- displacement reaction and oxidation-reduction reaction (also known as redox reaction). Out of the above mentioned chemical reactions Decomposition reaction is the reverse of combination reaction as in decomposition reaction a single compound breaks into smaller compounds in presence of heat or electricity.