- Enthalpy Change(H)
- Enthalpy Change
- The heat content of a chemical reaction is called the enthalpy (symbol: H)
- The enthalpy change (H) is the amount of heat released or absorbed when a chemical reaction occurs at constant pressure.
- H = H(products) - H(reactants)
- The units are usually given as kJ mol-1 (kJ/mol) or sometimes as kcal mol-1 (kcal/mol)1 calorie (1 cal) = 4.184 joules (4.184 J)
- Standard enthalpy change(H);Energy changes for any reaction which are measured under standard conditions of temperature and pressure25oC (298K) - 101.3 kPa (1 atmosphere) - 1 mol dm-3