E

Enthalpy of Solution

ΔH_sol = ΔH_lattice + ΔH_hydration; can be + or −
Quick Reference
Formula / NotationΔH_sol = ΔH_lattice + ΔH_hydration; can be + or −
Also Known AsHeat of solution, integral enthalpy of solution, ΔH_sol, molar enthalpy of dissolution

What is Enthalpy of Solution?

The heat change when one mole of a solute dissolves in a large excess of solvent at constant pressure and temperature. It combines the lattice enthalpy of the solute and the hydration enthalpy of the ions. Can be positive or negative depending on the substance.

Formula & Notation

ΔH_sol = ΔH_lattice + ΔH_hydration; can be + or −

Other Names / Synonyms: Heat of solution, integral enthalpy of solution, ΔH_sol, molar enthalpy of dissolution

Properties & Characteristics

The enthalpy of solution (heat of solution) is the heat change when one mole of solute dissolves in a specified solvent (usually water) to form a solution. It can be exothermic (NaOH: ΔH_sol = −44.5 kJ/mol) or endothermic (NH₄NO₃: ΔH_sol = +25.7 kJ/mol). It equals lattice energy + hydration energy for ionic compounds. The enthalpy of dilution is the additional heat change upon further diluting a solution.

Uses & Applications

Enthalpies of solution are used in designing instant hot packs (exothermic dissolution: CaCl₂) and cold packs (endothermic: NH₄NO₃), in determining thermodynamic properties of electrolyte solutions, and in pharmaceutical solubility studies.

Safety Information

Dissolving highly exothermic solutes (CaO, concentrated H₂SO₄, NaOH) in water generates intense heat. Always add solute to solvent (never solvent to solid) gradually with stirring. Use ice baths for highly exothermic dissolutions. Wear face shield and acid-resistant gloves.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Enthalpy of Solution
Formula ΔH_sol = ΔH_lattice + ΔH_hydration; can be + or −
Synonyms Heat of solution, integral enthalpy of solution, ΔH_sol, molar enthalpy of dissolution

Frequently Asked Questions

The heat change when one mole of a solute dissolves in a large excess of solvent at constant pressure and temperature. It combines the lattice enthalpy of the solute and the hydration enthalpy of the ions. Can be positive or negative depending on the substance.

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