A chemical reaction begins with 356kJ of energy and ends with 456kJ of energy.
What is the enthalpy of the reaction? Was the reaction endothermic or exothermic?

The enthalpy of the reaction is 100 kJ and the reaction is endothermic in nature.

Explanation:

Enthalpy of any chemical reaction is the measure of the difference in the energy utilized for performing a reaction. As in the present case, it is stated that the initially, a chemical reaction has 356 kJ of energy and after ending the chemical reaction has 456 kJ of energy.

This means the energy is increased after the chemical reaction. So the heat energy is absorbed during the reaction. This kind of chemical reaction where the products are formed by absorbing energy from the surrounding is termed as endothermic reaction.

Enthalpy = Energy absorbed = 456-356 =100 kJ.

So, the enthalpy of the reaction is 100 kJ. And as the enthalpy is positive which means the energy is absorbed from the surroundings, so the reaction is endothermic in nature.