A student completed an experiment to determine the enthalpy of neutralisation for the reaction between propanedioic acid solution (HOOCCH2COOH\text{HOOCCH}_2\text{COOH}HOOCCH2COOH) and sodium hydroxide solution.
The student added 30 cm330\text{ cm}^330 cm3 of 0.50 mol dm−30.50\text{ mol dm}^{-3}0.50 mol dm−3 propanedioic acid solution to 70 cm370\text{ cm}^370 cm3 of 0.50 mol dm−30.50\text{ mol dm}^{-3}0.50 mol dm−3 sodium hydroxide solution. The temperature increased by 2.5 ∘C2.5\ ^\circ\text{C}2.5 ∘C.
Give an equation for the reaction between propanedioic acid solution and sodium hydroxide solution.
Calculate the enthalpy change (ΔH\Delta HΔH) per mole of water formed in this reaction. Assume that the specific heat capacity of the reaction 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 reaction mixture is 1.00 g cm−31.00\text{ g cm}^{-3}1.00 g cm−3.
In a similar experiment, the enthalpy of neutralisation for the reaction between hydrochloric acid and sodium hydroxide solution was found to be −57.1 kJ mol−1-57.1\text{ kJ mol}^{-1}−57.1 kJ mol−1 per mole of water formed. Suggest an explanation for the difference between this value and your calculated value.
34 exam-style questions on AQA A Level Chemistry Energetics, covering Enthalpy change, Calorimetry, Applications of Hess's law, and Bond enthalpies. Each one has a worked solution and a mark scheme showing where the marks go.