The total heat content of a system at constant pressure is equivalent to the internal energy (E) plus the PV energy.
Representation
Enthalpy of the system is represented by the symbol ‘H’
Equation
Enthalpy is defined by the equation:
H = E + PV
where, P and V are the pressure and volume of the system.
Equation
If H1 and H2 are the enthalpies of the system in the initial and final states,
This equation is the most general definition of ΔH.
Equation
When the pressure remains constant throughout the process, then
Enthalpy of Formation
The enthalpy of formation of a compound is defined as the change in enthalpy of the system when one mole of the compound is formed from its elements. It is denoted by ΔHf.
Enthalpy of Formation
For example:
The heat of formation of SO2 is -70.96 kCals.
Enthalpy of Neutralization
The enthalpy of neutralization of an acid at a given temperature is defined as the change in enthalpy (ΔH) accompanying the neutralization of one gram equivalent of the acid by a base or vice-versa in dilute solution at that temperature.
Enthalpy of Vaporization
defined as the heat change or enthalpy change when one mole of a liquid is converted into vapors or a gaseous state at its boiling point.
Enthalpy of Vaporization
For example, When one mole of water is converted into steam at 1000C or 373 K, the heat absorbed is 9.71kCal, which is the heat of vaporization of water. The change can be represented as
How to calculate enthalpy change?
The mass of your reactants, s, the specific heat of your product, and ∆T, the temperature change from your reaction, you are prepared to find the enthalpy of reaction using the formula ∆H = m x s x ∆T.