7.3 Enthalpy Stoichiometry

Enthalpy Stoichiometry

Enthalpy stoichiometry is the process of analyzing the heat transfer in a reaction with certain amounts. The enthalpy of a reaction, or ΔH, is usually given in units of kJ/mol.

${A + 2B → AB_2}$, {ΔH = –30 kJ/mol}.

This means with every 2 moles of B used, there is an energy change of –30kJ in the system. With 1 mol of B used, the energy change would be –15kJ.

If the reaction is reversed, the sign of enthalpy is reversed as well. For example, if 2 moles of AB2 decomposed, the energy change would be +60kJ, meaning the reverse reaction is endothermic.