Enthalpy of neutralisation

A/L Chemistry · G.C.E. Advanced Level · Grades 12–13

Aim

To determine the enthalpy of neutralisation between HCl and NaOH.

Apparatus

• Polystyrene cup with a lid
• 1.0 mol dm⁻³ HCl and NaOH (50 cm³ each)
• Thermometer

Method

1. Note the starting temperature of the acid and alkali.
2. Mix them in the cup and stir.
3. Record the maximum temperature and find ΔT.
4. Calculate q = mcΔT and ΔH = −q ÷ n.

Conclusion

ΔH ≈ −57 kJ mol⁻¹ (H⁺ + OH⁻ → H₂O), the same for any strong acid and base; heat loss makes the measured value slightly smaller.