Pharmaceutical Chemistry
Heat of Neutralization Calculator
Acid–base calorimetry: works out the heat released when an acid and a base are mixed, from their masses and the temperature rise.
Heat change (ΔQ)
5434.00J
Exothermic · Large heat change – heat released to surroundings.
Experimental data
Mass of the acid solution. 100 mL of dilute solution ≈ 100 g.
Mass of the base solution.
Default 4.18 for dilute aqueous solutions.
Temperature of the solutions before mixing.
Highest temperature reached. Both share one unit.
Display heat in
Working
Masses converted to grams and temperatures to °C, then substituted.
ΔQ = 200.0 g × 4.18 J/g·°C × 6.50 °C
= 5434.00 J
Typical neutralization enthalpies
Values at 25 °C. Negative = exothermic.
| Reaction | Note | ΔH (kJ/mol) |
|---|---|---|
| HCl + NaOH | Strong–strong | −57.9 |
| H₂SO₄ + NaOH | Per mol H⁺ | −57.1 |
| CH₃COOH + NaOH | Weak acid | −55.8 |
| HCl + NH₃ | Weak base | −51.6 |
ΔQ = (m_acid + m_base) × c × ΔT
ΔH = ΔQ (kJ) ÷ moles of limiting reactant
ΔQ — heat absorbed/released (J). m_acid, m_base — masses of the acid and base solutions (g). c — specific heat capacity (J/g·°C). ΔT — temperature change (T₂ − T₁). ΔH — ΔQ in kJ divided by the moles of the limiting reactant.
A temperature change in kelvin is the same size as in °C, so K inputs give the same ΔT.
Common questions
After mixing, the whole solution absorbs the heat, so the heat capacity is that of the combined mass. For dilute solutions 1 mL is taken as about 1 g, so 50 mL acid + 50 mL base is 100 g.
Multiply concentration (mol/L) by volume (L) for each reactant; the smaller number is limiting. 50 mL of 1.0 M HCl is 0.050 mol.
Some heat escapes to the cup, thermometer and air, and weak acids or bases use energy to ionise first. Both make the measured value smaller than for a strong acid with a strong base.
By convention, yes — neutralization is exothermic, so ΔH is written with a minus sign (for example −57.9 kJ/mol). This calculator follows the sign of ΔT, so a warming mixture gives a positive number — add the minus sign when you write it up.
Prepared by the PharmaWallah student team. Verify results with your textbook or instructor. Report an error · Editorial policy