Question

Differentiate between an exothermic and an endothermic reaction.
1. Endothermic releases heat and exothermic absorbs energy
2. Exothermic releases heat and endothermic absorbs energy
3. Hydrogen gas is evolved in exothermic but not in endothermic
4. Hydrogen gas is evolved in endothermic but not in exothermic

Answer 1

This question gives the knowledge about the exothermic and endothermic reactions. The exothermic reactions are the reactions in which emission of heat energy takes place. This type of reaction generally takes place in rusting of iron and cleaving of chemical bonds.

Complete step-by-step answer: The difference between exothermic reactions and endothermic reactions is as follows:

Exothermic reactions	Endothermic reactions
The exothermic reactions are the reactions in which emission of heat energy takes place.This type of reaction generally takes place in rusting of iron, breaking of chemical bonds and so forth.	The endothermic reactions are the reactions in which absorption of heat energy takes place.This type of reaction generally takes place in melting of ice, in cooking, during photosynthesis and so forth.

Therefore, option $2$ is the correct option.

Additional information: The exothermic reactions are the reactions in which emission of heat energy takes place. This type of reaction generally takes place in rusting of iron, breaking of chemical bonds and so forth.

Characteristics of exothermic reactions are as follows:

1.In exothermic reactions, the energy is generally emitted from the system.
2.In energy profile diagrams of exothermic reactions, the enthalpy of products is lower than the enthalpy of products.
3.The change in enthalpy possesses negative value.
4.The temperature increases as the reaction moves forward.

The endothermic reactions are the reactions in which absorption of heat energy takes place. This type of reaction generally takes place in melting of ice, in cooking, during photosynthesis and so forth.

Characteristics of endothermic reactions are as follows:

1.In endothermic reactions, the energy is generally absorbed by the system.
2.In energy profile diagrams of endothermic reactions, the enthalpy of products is higher than the enthalpy of products.
3.The change in enthalpy possesses positive value.
4.The temperature decreases as the reaction moves forward.

Note: In exothermic reactions, the activation energy is very low whereas in endothermic reactions the activation energy is very high. Activation energy is inversely proportional to the temperature. So, if the temperature increases then activation energy will decrease.