A pupil mixes 50.0 cm³ of 1.00 mol dm⁻³ hydrochloric acid with 50.0 cm³ of 1.00 mol dm⁻³ sodium hydroxide. Both solutions start at 20.0 °C and the highest temperature is 26.5 °C. Assume the mixture has a mass of 100.0 g and a specific heat capacity of 4.18 J g⁻¹ K⁻¹. Calculate the heat transferred to the mixture using q = mcΔT.

Use the experimental data to calculate the enthalpy change of neutralisation, in kJ mol⁻¹, for the formation of one mole of water. Include the correct sign.

The accepted enthalpy change of neutralisation has a larger negative magnitude than the pupil’s result. Explain one limitation of this procedure and suggest one specific improvement that would reduce its effect.