Question: Which reaction is this? \[CaO+{{H}_{2}}O\to Ca{{(OH)}_{2}}\]...

Question

Which reaction is this?
$CaO+{{H}_{2}}O\to Ca{{(OH)}_{2}}$

Answer 1

Solution

The reactions in which energy is absorbed in the form of heat is known as endothermic reaction. On the other hand, converse of this, the reactions in which heat is released is known as exothermic reaction.
A combination reaction is the one or more reactants form a single product while a decomposition reaction is the one in which a single compound breaks into simpler products.

Complete step by step answer:
The given reaction is a combination reaction as it can be clearly seen that the two reactants are forming a single product.
Also it is known that the following reaction releases heat, and hence it is an exothermic reaction.
Thus the given reaction is a combination and exothermic reaction.

Additional Information
$CaO$ is called as quicklime or burnt lime, it is a dense white powder. It is dissolved in wall dry paints. When it is hydrolysed, that is reacted with water, it forms an alkaline caustic solution known as slaked lime $Ca{{(OH)}_{2}}$ .
This slaked lime is formed when dry paint is mixed with water (in whitewash paints) and when it is applied to walls, it reacts with carbon dioxide in air to produce limestone $CaC{{O}_{3}}$ that gives shiny finish to walls.
$CaO+{{H}_{2}}O\to Ca{{(OH)}_{2}}$
$Ca{{(OH)}_{2}}+C{{O}_{2}}\to CaC{{O}_{3}}$ (limestone)
When $CaO$ is put in excess in the paint, it leads to powdery walls which is undesirable.

Note:
$CaO$ is called as quicklime or burnt lime, it is a dense white powder. It is dissolved in wall dry paints. When it is hydrolysed, that is reacted with water, it forms an alkaline caustic solution known as slaked lime $Ca{{(OH)}_{2}}$ .
This slaked lime is formed when dry paint is mixed with water (in whitewash paints) and when it is applied to walls, it reacts with carbon dioxide in air to produce limestone $CaC{{O}_{3}}$ that gives shiny finish to walls.
$CaO+{{H}_{2}}O\to Ca{{(OH)}_{2}}$
$Ca{{(OH)}_{2}}+C{{O}_{2}}\to CaC{{O}_{3}}$ (limestone)
When $CaO$ is put in excess in the paint, it leads to powdery walls which is undesirable.