CalorimetryAQA A-Level Chemistry: Mind map

Exam questions on Calorimetry

1. A student mixes 25.0 cm³ of 1.00 mol dm⁻³ hydrochloric acid with 25.0 cm³ of 1.00 mol dm⁻³ sodium hydroxide solution in a polystyrene cup. The initial temperature of both solutions is 20.5 °C and the highest temperature reached is 27.3 °C. Assume that the density of the solution is 1.00 g cm⁻³ and that its specific heat capacity is 4.18 J g⁻¹ K⁻¹.
   Calculate the molar enthalpy change of neutralisation, in kJ mol⁻¹, for this reaction. Include the sign.2 marks
2. A student measures the enthalpy of combustion of ethanol using a spirit burner to heat 100 g of water in a copper calorimeter. The mass of the burner and ethanol falls from 215.30 g to 214.84 g during the experiment, and the temperature of the water rises from 19.0 °C to 38.0 °C. The specific heat capacity of water is 4.18 J g⁻¹ K⁻¹ and the data book value for the enthalpy of combustion of ethanol is −1367 kJ mol⁻¹. The relative formula mass, Mr, of ethanol is 46.0.
   The experimental value is much less exothermic than the data book value. Suggest two reasons for this.2 marks
3. A student adds excess zinc powder to 50.0 cm³ of 0.500 mol dm⁻³ copper(II) sulfate solution in a polystyrene cup fitted with a lid. The temperature rises from 19.5 °C to 45.0 °C. The thermometer has an uncertainty of ±0.1 °C on each reading. Assume that the solution has a density of 1.00 g cm⁻³ and a specific heat capacity of 4.18 J g⁻¹ K⁻¹. The equation for the reaction is Zn + CuSO₄ → ZnSO₄ + Cu.
   Calculate the molar enthalpy change for this reaction, in kJ mol⁻¹, per mole of copper(II) sulfate.3 marks