Question

What are the values of $H$ for endothermic and exothermic reactions?

Answer 1

The thermodynamic words endothermic and exothermic relate to the energy differential between the products and reactants. These terms have very little to do with response time. The reaction rate is related to the reaction mechanism. There are two types of reactions: quick and slow endothermic reactions and fast and slow exothermic reactions.

Complete answer:
Heat is given out in exothermic processes, therefore the enthalpy of the products is less than the enthalpy of the reactants, resulting in a negative enthalpy change. Heat is absorbed in endothermic reactions, which raises the enthalpy of the products. In this situation, the reaction's enthalpy change is positive.
Enthalpy Variations:
Exothermic reactions, which release heat into the environment, have a negative $\Delta H$ by convention because the enthalpy of the products is lower than the enthalpy of the system's reactants. These reactions have enthalpies that are less than zero, making them exothermic. Because the enthalpy of the products is higher than the enthalpy of the system's reactants, a system of reactants that absorbs heat from the surroundings in an endothermic reaction has a positive $\Delta H$ .

Note:
If enthalpy is zero, all internal energy is turned into productive work, and the system is shut down completely. If the enthalpy is reduced further to negative levels in some fashion, the internal energy and, finally, the enthalpy will tend to grow and return to normal.