Question

“To pour water on calcium oxide.” Which is another way to classify this reaction? Explain.

Answer 1

Calcium oxide is also known as quicklime. When we add water to it, the reaction moves forward by releasing heat. Such a process has a specific name in chemistry. Use this to answer the given question.

Complete step by step Answer: We know that calcium oxide is a widely used chemical compound. It is white in colour and crystalline at room temperature. It is alkaline in nature at room temperature.
We also know it by the name quicklime or burnt lime.
We know that based upon the heat required or released during the reaction, a reaction can be classified either as endothermic or exothermic. Let us discuss these two processes before answering the question.
When we add two reactants to get a particular product out of it, there is a reaction taking place between the reactants. This reaction is either endothermic i.e. to move forward and give us the product it will require some sort of energy which is generally in the form of heat or sometimes light if not endothermic, the reaction is exothermic which means it proceeds forward by releasing energy in the surrounding. This energy is released in the form of heat.
When we add water to calcium oxide, we get calcium hydroxide and heat. Calcium hydroxide is also known as slaked lime. Calcium oxide is the base anhydride of calcium hydroxide. We can write the reaction as:
$CaO+{{H}_{2}}O\to Ca{{\left( OH \right)}_{2}}+Heat$
As we can see that it releases heat therefore, this reaction is exothermic.
Therefore, another way to classify this reaction is as an exothermic reaction and this is the required answer.

Note: Quick lime is generally produced as the thermal decomposition product of substances containing calcium carbonate.
$CaC{{O}_{3}}\to CaO+{{H}_{2}}O$
The quick lime is not stable and when cooled it reacts with carbon dioxide to give back calcium carbonate unless it is set with water to form lime plaster or lime mortar.