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 (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
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This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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