Enthalpy of Dilution
The enthalpy change when a solution is diluted from one concentration to another by adding solvent.
Formula / equation
ΔH_dil
Unit
kJ/mol
In depth
Dilution alters the extent of ion solvation and ion–ion interaction, releasing or absorbing heat. For concentrated acids the effect is large and strongly exothermic, which is why sulfuric acid must always be poured into water rather than water into acid.
Examples in the real world
Diluting concentrated H₂SO₄ releases enough heat to boil the water locally and spit acid if done incorrectly.