Question

In an endothermic reaction, the value of $\Delta H$ is always ________.

Answer 1

$\Delta H$ is the symbol used to represent the change in enthalpy of the reaction. Based on the change in the energy there are two types of reactions: endothermic reactions and exothermic reactions.

Complete answer:
There are many types of reactions, like redox reaction, combination reaction, endothermic reaction, exothermic reaction, etc.
We know that the reactions can be categorized on the basis of many factors, so energy or heat is a factor in which the reactions are divided into two, i.e., exothermic reactions and endothermic reactions. If the reactions occur and energy or heat is released then it will be categorized as an exothermic reaction and if the reactions occur when the energy is supplied or absorbed then it will be categorized as an endothermic reaction.
So, the endothermic reactions and exothermic reactions can be distinguished by the value of $\Delta H$. $\Delta H$ is the symbol used to represent the change in enthalpy of the reaction.
The value of $\Delta H$ is always positive for the endothermic reaction and the value of $\Delta H$ is always negative for the exothermic reaction.
Endothermic reactions lower the temperature of the surrounding area, resulting in a cooling effect, and exothermic reactions higher the temperature of the surrounding area, resulting in a heating effect.
So, in an endothermic reaction, the value of $\Delta H$ is always positive.

Note:
If the value of $\Delta H$ is zero then there is no change in the energy of the reaction, i.e., neither there is a rise in the temperature nor lowering in the temperature. The heating and cooling effect can be observed in a reaction without any external factor.