Question

Which of the following is an endothermic reaction?
(A) Bond formation by two unstable atoms at a certain condition
(B) Combustion reaction.
(C) Conversion of more stable allotrope to less stable allotropic element.
(D) Condensation of the vapor to its liquid state.

Answer 1

Hint: In order to answer the question, we must first have an idea about what an endothermic reaction is. An endothermic reaction is said to be a reaction in which the reactants will be absorbing heat energy from the surrounding in order to form a product.

Complete step by step answer:
Let us first understand the endothermic reaction. An endothermic reaction is said to be a reaction in which the reactants will be absorbing heat energy from the surrounding in order to form a product. During this process, the temperature of the surrounding surface will be lowered thereby producing a cooling effect.
Let us now move to the given question.
Option (A) The formation of a bond by two unstable atoms is found to be an exothermic process because this process will lose its energy in the form of heat. Therefore, this is an incorrect option.
Option (B) Combustion reaction is found to be an exothermic reaction because this process will lose its energy in the form of heat. Therefore, it is an incorrect option.
Option (C) In order to convert a more stable allotrope to less stable allotropic elements will take place when a certain amount of heat is being supplied. Therefore, it is an endothermic reaction and hence it is a correct option.
Option (D) Condensation of the vapor to its liquid state will involve loss of energy in the form of heat and hence it is an exothermic reaction. Therefore, this is an incorrect option So, the correct answer is “Option C”.

Note: We have to remember that the endothermic reaction is different from the exothermic reaction. An exothermic reaction is said to be a reaction in which the reactants will be releasing the heat energy from the system, during the formation of the product.