AQA A-level CHEMISTRY 7405/3 Paper 3 Question Paper + Mark scheme [MERGED] June 2022 *JUN* IB/M/Jun22/E16 7405/3 For Examiner’s Use Question Mark 1

AQA A-level CHEMISTRY 7405/3 Paper 3 Question Paper + Mark scheme [MERGED] June 2022 *JUN* IB/M/Jun22/E16 7405/3 For Examiner’s Use Question Mark 1 2 3 4 5 Section B TOTAL Time allowed: 2 hours Materials For this paper you must have: • the Periodic Table/Data Booklet, provided as an insert (enclosed) • a ruler with millimetre measurements • a scientific calculator, which you are expected to use where appropriate. Instructions • Use black ink or black ball-point pen. • Fill in the boxes at the top of this page. • Answer all questions. • You must answer the questions in the spaces provided. Do not write outside the box around each page or on blank pages. • If you need extra space for your answer(s), use the lined pages at the end of this book. Write the question number against your answer(s). • All working must be shown. • Do all rough work in this book. Cross through any work you do not want to be marked. Information • The marks for questions are shown in brackets. • The maximum mark for this paper is 90. Advice • You are advised to spend 70 minutes on Section A and 50 minutes on Section B. Please write clearly in block capitals. Centre number Candidate number Surname Forename(s) Candidate signature I declare this is my own work. A-level CHEMISTRY Paper 3 2 *02* IB/M/Jun22/7405/3 Do not write outside the There are no questions printed on this page box DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED 3 *03* Turn over ► IB/M/Jun22/7405/3 Do not write outside the Section A box Answer all questions in this section. 0 1 A value for enthalpy of solution can be determined in two ways: • from a cycle, using lattice enthalpy and enthalpies of hydration • from the results of a calorimetry experiment. 0 1 . 1 Define the term enthalpy of lattice dissociation. [2 marks] 0 1 . 2 The enthalpy of solution for ammonium nitrate is the enthalpy change for the reaction shown. NH4NO3(s) + aq → NH4 + (aq) + NO3 − (aq) ∆H = +26 kJ mol−1 Table 1 NH4 + (g) NO3 − (g) Enthalpy of hydration hydH/ kJ mol 1 −307 −314 Draw a suitably labelled cycle and use it, with data from Table 1, to calculate the enthalpy of lattice dissociation for ammonium nitrate. [3 marks] Enthalpy of lattice dissociation kJ mol−1 4 *04* IB/M/Jun22/7405/3 Do not write outside the box 0 1 . 3 A student does an experiment to determine a value for the enthalpy of solution for ammonium nitrate. The student uses this method. • Measure 25.0 cm3 of distilled water in a measuring cylinder. • Pour the water into a beaker. • Record the temperature of the water in the beaker. • Add 4.00 g of solid NH4NO3 to the water in the beaker. • Stir the solution and record the lowest temperature reached. Table 2 shows the student’s results. Table 2 Initial temperature / °C 20.2 Lowest temperature / °C 12.2 Calculate the enthalpy of solution, in kJ mol−1, for ammonium nitrate in this experiment. Assume that the specific heat capacity of the solution, c = 4.18 JK−1 g−1 Assume that the density of the solution = 1.00 gcm−3 [3 marks] Enthalpy of solution kJ mol−1 5 *05* Turn over ► IB/M/Jun22/7405/3 Do not write outside the box 0 1 . 4 The uncertainty in each of the temperature readings from the thermometer used in this experiment is ±0.1°C Calculate the percentage uncertainty in the temperature change in this experiment. [1 mark] Percentage uncertainty 0 1 . 5 Suggest a change to the student’s method, using the same apparatus, that would reduce the percentage uncertainty in the temperature change. Give a reason for your answer. [2 marks] Change Reason 0 1 . 6 Another student obtained a value of +15 kJ mol−1 using the same method. Suggest the main reason for the difference between this experimental value for the enthalpy of solution and the correct value of +26 kJ mol−1 [1 mark] Question 1 continues on the next page 6 *06* IB/M/Jun22/7405/3 Do not write outside the box 0 1 . 7 Table 3 shows some entropy data at 298 K Table 3 Entropy S/ JK 1mol 1 NH4NO3(s) 151 NH4 + (aq) 113 NO3 − (aq) 146 Calculate a value for the Gibbs free-energy change (∆G), at 298 K, for the reaction when ammonium nitrate dissolves in water. NH4NO3(s) + aq → NH4 + (aq) + NO3 − (aq) ∆H = +26 kJ mol−1 Use data from Table 3 and the value of ∆H from the equation. Assume for the solvent, water, that the entropy change, ∆S = 0 Explain what the calculated value of ∆G indicates abo