Question

Is the reaction $CaC{O_3}(s) \to CaO(s) + C{O_2}(g)$ an exothermic reaction?

Answer 1

In order to answer this question, to know whether the given reaction is an exothermic reaction or not, first we should know about the exothermic reaction. And then we will cross examine the reaction, whether it releases the heat or it absorbs the heat. Then we can decide the given reaction is exothermic or endothermic.

Complete answer:
No, the given reaction is not an exothermic reaction, it is an endothermic reaction.
This is the decomposition of limestone to calcium oxide (quicklime) and carbon dioxide on heating.
A decomposition reaction is a chemical reaction in which a single compound breaks down into two or more elements or new compounds. Hence, it is an example of a decomposition reaction.
$*$ Increasing the temperature favours the decomposition of calcium carbonate. The forward reaction is endothermic and absorbs heat – the system is trying to minimise the temperature increase.
$*$ Decreasing the temperature favours the formation of calcium carbonate. The backward reaction is exothermic, so more heat is released – the system is trying to minimise the temperature decrease.
Difference between Endothermic and Exothermic Reactions. Such chemical reactions in which the energy is absorbed in the form of heat is known as the endothermic reaction, while such chemical reactions in which energy is released or evolved in the form of heat is known as the exothermic reaction.

Note:
In exothermic reactions, energy is released from the system. The final products are stable in exothermic reactions. Endothermic reactions are reactions that require external energy, usually in the form of heat, for the reaction to Proceed. Given that they absorb heat from their surroundings, they tend to cool down their environments.