AQA A-level CHEMISTRY 7405/2 Paper 2 Organic and Physical Chemistry Version: 1.0 Final *Jun* IB/M/Jun23/E8 7405/2// QUESTION PAPER & MARKING SCHEME/ [MERGED] Marl( scheme June 2023

AQA A-level CHEMISTRY 7405/2 Paper 2 Organic and Physical Chemistry Version: 1.0 Final *Jun* IB/M/Jun23/E8 7405/2 For Examiner’s Use Question Mark 1 2 3 4 5 6 7 8 9 TOTAL Monday 19 June 2023 Afternoon 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 105. 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 2 Organic and Physical Chemistry 2 *02* IB/M/Jun23/7405/2 Do not write outside the Answer all questions in the spaces provided. box 0 1 This question is about rates of reaction. Figure 1 shows apparatus used to measure the rate of reaction when an acid reacts with an excess of solid sodium hydrogencarbonate, NaHCO3 When different monoprotic organic acids are used, the rates at which gas escapes can be used to compare the strengths of the acids. A timer is started when the NaHCO3 is added to the acid and the mass of CO2 gas lost is recorded at regular intervals. (It is assumed that any change in mass is due to the loss of CO2) Figure 1 0 1 . 1 Suggest a reason why using a conical flask instead of a beaker would give more accurate results in this experiment. [1 mark] 3 *03* Turn over ► IB/M/Jun23/7405/2 Do not write outside the Figure 2 shows the results of this experiment when 25.0 cm3 of a box 2.23 mol dm–3 solution of ethanoic acid reacts with an excess of NaHCO3 Figure 2 0 1 . 2 Use Figure 2 to calculate the rate of reaction at 2 minutes. Deduce the units of your calculated rate. [3 marks] Rate Units 0 1 . 3 Chloroethanoic acid is a stronger acid than ethanoic acid. Sketch, on Figure 2, the curve you would expect when 25.0 cm3 of a 2.23 mol dm–3 solution of chloroethanoic acid reacts with an excess of NaHCO3 Suggest why chloroethanoic acid is a stronger acid than ethanoic acid. [3 marks] 7 4 *04* IB/M/Jun23/7405/2 Do not write outside the box 0 2 A and B react together in the presence of an acid catalyst. A(aq) + 2B(aq) → C(aq) + D(aq) The rate equation for this reaction is rate = k[B]2[H+] Table 1 shows how the values of the relative initial rate vary with different concentrations of each reagent at the same temperature. Table 1 Experiment [A] / mol dm–3 [B] / mol dm–3 [H+] / mol dm–3 Relative initial rate 1 0.40 0.20 0.10 1.00 2 0.50 0.20 0.10 3 0.40 0.10 0.64 4 0.50 0.30 0.06 0 2 . 1 Complete Table 1 by calculating the missing values. [3 marks] 0 2 . 2 A suggested mechanism for the reaction is shown. Step 1 B + H+ → BH+ Step 2 BH+ + B → B2H+ Step 3 B2H+ + A → C + D Deduce the rate-determining step for this reaction. Give a reason for your answer. [2 marks] Rate-determining step Reason 5 5 *05* Turn over ► IB/M/Jun23/7405/2 Do not write outside the Turn over for the next question box DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED 6 *06* IB/M/Jun23/7405/2 Do not write outside the box 0 3 This question is about intermediates in reaction mechanisms. 0 3 . 1 Figure 3 shows an intermediate formed in the first step of a nucleophilic addition–elimination mechanism. Figure 3 Complete Figure 3 to show the structures of the two reactant species with curly arrows and relevant lone pairs of electrons involved in the formation of the intermediate. Draw curly arrows and relevant lone pairs of electrons on the intermediate to show how the final products are formed. [4 marks] 7 *07* Turn over ► IB/M/Jun23/7405/2 Do not write outside the box 0 3 . 2 Figure 4 shows an intermediate formed in the first step of a reaction mechanism of methylbenzene. Figure 4 Complete Figure 4 to show the reactant species and any curly arrows involved in the formation of the intermediate. Draw a curly arrow on the intermediate to show how the product is formed. Give the name of the reaction mechanism. [4 marks] Name of mechanism 0 3 . 3 Figure 5 shows the reactant species involved in the first step of a mechanism. Figure 5 Complete Figure 5 to show the structure of the intermediate formed with curly arrows involved in its formation. Give the name of the reaction mechanism.