The enthalpy of dilution (also called heat of dilution) is the enthalpy change associated with the dilution of a component in a solution at constant pressure. It represents the heat released or absorbed when a solution is diluted by adding more solvent. The enthalpy of dilution can be expressed as energy per mole or mass of substance, commonly in units of kJ/mol or J/mol. There are two main perspectives for enthalpy of dilution:
- Differential enthalpy of dilution: the enthalpy change when a very small amount of solvent is added to a large amount of solution, causing negligible concentration change.
- Integral enthalpy of dilution: the enthalpy change when a certain amount of solution is diluted from an initial concentration to a final concentration, normalized per mole of solute.
At infinite dilution (adding an infinite amount of solvent), the enthalpy of dilution reaches a limiting value called the integral enthalpy of dilution to infinite dilution. The enthalpy of dilution is also equal to the enthalpy of dissolution if the initial state is a pure liquid component being dissolved into the solution.
