Enthalpy of Solution / Dissolution Calculator
Calculate the heat released or absorbed when a solute dissolves in water.
Find the temperature change in a coffee-cup calorimeter setup.
Enthalpy of Solution
Enthalpy of solution (ΔH_soln) is the heat change when one mole of a solute dissolves in a solvent.
Heat released or absorbed by dissolution:
q = n × ΔH_soln
Where n = moles of solute = mass / molar mass.
Temperature change of the solution:
ΔT = q / (m_solution × Cp_solution)
For dilute aqueous solutions, Cp ≈ 4.18 J/g·°C (same as water). m_solution = mass of solvent + mass of solute.
Common ΔH_soln values at 25°C:
| Compound | ΔH_soln (kJ/mol) | Type |
|---|---|---|
| NaCl (table salt) | +3.9 | Endothermic (slightly absorbs heat) |
| NaOH | −44.5 | Exothermic (dissolves vigorously, gets HOT) |
| KOH | −57.1 | Exothermic |
| NH₄NO₃ | +25.7 | Endothermic (used in instant cold packs) |
| NH₄Cl | +14.8 | Endothermic |
| LiCl | −37.0 | Exothermic |
| CaCl₂ | −81.3 | Exothermic (road de-icer, hand warmers) |
| KNO₃ | +34.9 | Endothermic |
| MgSO₄ (Epsom salt) | −91.2 | Exothermic |
| Glucose | +10.6 | Endothermic |
| Urea | +15.4 | Endothermic |
Practical applications:
- Instant cold packs: ammonium nitrate dissolving in water (endothermic, absorbs heat)
- Chemical hand warmers: calcium chloride or sodium acetate (exothermic, releases heat)
- Safety note: NaOH dissolution is highly exothermic — always add solid to water, never add water to solid