What is enthalpy change in a chemical reaction?

Enthalpy change in a chemical reaction refers to the energy difference between the products and the reactants. It is a measure of the heat content of a system at constant pressure and is essential for understanding the energy dynamics in chemical transformations. When a reaction occurs, the reactants can either absorb energy from the surroundings (endothermic reaction) or release energy into the surroundings (exothermic reaction). The enthalpy change quantifies this energy difference, indicating whether the process has resulted in a net gain or loss of energy.

This concept is critical in predicting the favorability of reactions and understanding their mechanisms. For instance, if the enthalpy change is negative, it suggests that the products are at a lower energy state than the reactants, rendering the reaction more likely to proceed spontaneously. Conversely, a positive enthalpy change indicates that energy has been absorbed, which may require additional input of energy to occur.

The other options present various misconceptions. While the difference in temperature might relate to energy changes in some specific contexts, it does not define enthalpy change directly as the focus is on energy content, not temperature. Option C restricts enthalpy change to only exothermic reactions, which overlooks the important aspect of endothermic