A compound ‘A’ is used in the manufacture of cement. When dissolved in water, it evolves a large amount of heat and forms compound ‘B’. $\left(\mathrm{i}\right)$ Identify A and B. $\left(\mathrm{ii}\right)$ Write the chemical equation for the reaction of A with water. $\left(\mathrm{iii}\right)$ List two types of reaction in which this reaction may be classified.

Identification of the compound A and B:

• Here the compound ‘A’ which is given to be used in the manufacture of cement dissolves in water, evolves a large amount of heat and forms compound ‘B’.
• The given compound can be: A as Calcium Oxide $\left(\mathrm{CaO}\right)$and B as Calcium hydroxide $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$
• Calcium oxide $\left(\mathrm{CaO}\right)$is mostly known to be used in the manufacture of cement and when it dissolves in water it forms the compound calcium hydroxide $\mathrm{Ca}\left(\mathrm{OH}\right)2.$ with the evolutions of a large amount of heat.

The chemical equation for the reaction of A with water :

• The compound A, which is determined to be calcium oxide $\left(\mathrm{CaO}\right)$undergoes the reaction with water and produces calcium hydroxide $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$along with evolving a large amount of heat.
• The chemical equation for the given reaction can be given as:

$\underset{\left(\mathrm{Calcium}\mathrm{Oxide}\right)}{\mathrm{CaO}\left(\mathrm{s}\right)}+\underset{\left(\mathrm{Water}\right)}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}\to \underset{(\mathrm{Calcium}\mathrm{hydroxide})}{\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{s}\right)+\mathrm{Heat}}$

Two types of reaction in which this reaction may be classified:

• As in the above mention reaction compound, A is reacting with water to give compound B, the reaction can be classified as a hydrolysis reaction.
• Also, during the reaction there exist the evolution of heat hence, the reaction can also be classified as an exothermic reaction.