How do you calculate the enthalpy change of a reaction?

The enthalpy change of a reaction is calculated by subtracting the total enthalpy of the reactants from that of the products.

In more detail, enthalpy change, denoted as ΔH, is a measure of the amount of energy absorbed or released by a reaction. It is a fundamental concept in thermodynamics and is particularly important in understanding energy changes in chemical reactions. The enthalpy change of a reaction is calculated using the formula ΔH = H(products) - H(reactants), where H represents the total enthalpy.

To calculate the enthalpy change, you first need to know the enthalpies of the reactants and the products. These values are usually given in kilojoules per mole (kJ/mol) and can be found in tables of standard enthalpies of formation. The standard enthalpy of formation of a compound is the change in enthalpy when one mole of the compound is formed from its constituent elements in their standard states.

Once you have these values, you can calculate the total enthalpy of the reactants and the products by multiplying the enthalpy of each substance by the number of moles of that substance in the reaction. Then, subtract the total enthalpy of the reactants from the total enthalpy of the products to find the enthalpy change.

Remember, if the enthalpy change is negative, the reaction is exothermic, meaning it releases energy. If the enthalpy change is positive, the reaction is endothermic, meaning it absorbs energy. This is a crucial aspect of understanding the behaviour of chemical reactions and their potential applications.