A student completed an experimental investigation using a simple calorimeter to determine the enthalpy of neutralisation for the reaction between butanedioic acid solution (HOOC(CH2)2COOH\text{HOOC(CH}_2)_2\text{COOH}HOOC(CH2)2COOH) and sodium hydroxide solution.
The student mixed 40 cm340\text{ cm}^340 cm3 of 0.40 mol dm−30.40\text{ mol dm}^{-3}0.40 mol dm−3 butanedioic acid solution with 80 cm380\text{ cm}^380 cm3 of 0.50 mol dm−30.50\text{ mol dm}^{-3}0.50 mol dm−3 sodium hydroxide solution. The recorded temperature rise of the reaction mixture was 2.8 ∘C2.8\ ^\circ\text{C}2.8 ∘C.
Write a balanced chemical equation for the reaction that occurs between aqueous butanedioic acid and aqueous sodium hydroxide.
Calculate the enthalpy change of neutralisation, ΔH\Delta HΔH, per mole of water formed during this reaction.
Assume that the specific heat capacity of the final mixture is 4.2 J K−1 g−14.2\text{ J K}^{-1}\text{ g}^{-1}4.2 J K−1 g−1 and that the density of the mixture is 1.00 g cm−31.00\text{ g cm}^{-3}1.00 g cm−3.
In a separate experiment, the enthalpy of neutralisation for the reaction between aqueous nitric acid and aqueous potassium hydroxide was determined to be −57.3 kJ mol−1-57.3\text{ kJ mol}^{-1}−57.3 kJ mol−1 per mole of water formed. Suggest an explanation for why the calculated value for butanedioic acid in part (b) is different from this value.