Enthalpy is defined as the heat of reaction at constant pressure. So it is equivalent to heat as long as pressure remains unchanged.
The symbol for enthalpy is “H” and the units remain in Joules (J) or kilojoules (kJ) just like heat.
THUS: H= qp or enthalpy= heat @ constant pressure.
Notation of Enthalpy:
The enthalpy for a reaction, or ∆H, tells whether the reaction was exothermic (- ∆H) or endothermic (+ ∆H).
- Enthalpy Notation at End of Equations
The ∆H can be written at the end of the chemical equation to signify the amount of heat AND whether it was absorbed (+∆H) or released (-∆H).CH4 (g) + 2O2 —> CO2 (g) + 2H2O (l) ΔH= -890.4 kJ H2O (s) —-> H2O (l) ΔH= +6.01 kJ
- Enthalpy Notation Within the Equation
CH4 (g) + 2O2 —> CO2 (g) + 2H2O (l) + 890.4 kJ