Question

What type of reaction is the reaction of quick lime with water?

Answer 1

Calcium oxide ($CaO$ ) which is commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline, crystalline solid at room temperature. The compound has very strong ionic and covalent bonds between the calcium and oxygen atoms and when these bonds are hydrolyzed, they release a huge amount of heat energy as the reaction is exothermic in nature.

Complete step by step answer:
When quick lime is reacted with water, it releases a huge amount of energy because of the hydrolysis of calcium oxide in which the bond stabilizing energy is high and the bond is almost ionic. The calcium oxide on dissociation with water releases two ions. One is the calcium divalent cation ($C{a^{2 + }}$ ) and other is the oxygen divalent anion (${O^{2 - }}$ ). The calcium oxide has rigid lattice structure with a high amount of lattice energy. But on hydrolyzing it, the solvation energy is way much greater than the lattice energy of calcium oxide and it dissolves in the water to give calcium hydroxide or slaked lime ($Ca{(OH)_2}$). The reaction is written as:
$CaO + {H_2}O \to Ca{(OH)_2} + \Delta$
The $'\Delta '$ symbol is denoted for heat and the reaction can be explained as an exothermic reaction.

Note: For a compound to have a higher value of lattice energy the size of the cation should be less and the charge on the cation should be more. Thus, higher the polarization value of the compound, higher will be the lattice energy and thus, higher will be the hydration energy required to break the bonds and dissolve the compound.