AQA AS CHEMISTRY Paper 2 Organic and Physical Chemistry for MAY 2023

AQA AS CHEMISTRY Paper 2 Organic and Physical Chemistry Tuesday 23 May 2023 Morning Time allowed: 1 hour 30 minutes Materials For this paper you must have: • the Periodic Table/Data Sheet, 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 80. Advice You are advised to spend about 65 minutes on Section A and 25 minutes on Section B. Section A Answer all questions in this section. box This question is about the analysis of organic compounds. For each pair of compounds in Questions 01.1 and 01.2, give a reagent (or combination of reagents) that could be added separately to each compound in a single reaction to distinguish between them. State what is observed in each case. . CH3CH2CH2CHO and CH3CH2CH(OH)CH3 [3 marks] Reagent(s) Observation with CH3CH2CH2CHO Observation with CH3CH2CH(OH)CH3 . Cyclohexane and cyclohexene [3 marks] Reagent(s) Observation with cyclohexane Observation with cyclohexene . Table 1 gives the precise relative molecular masses (Mr) of some organic compounds measured using high resolution mass spectrometry. Table 1 Molecular formula C5H12 C5H10 C6H6 Mr 72.1416 70.1260 to be calculated Turn over ► box This question is about fuels. box . Crude oil is separated into fractions by fractional distillation. State the meaning of the term ‘fraction’ in this context. [1 mark] . Petrol for cars contains branched and cyclic alkanes produced by catalytic cracking. Identify the catalyst used in this process. [1 mark] . 3-Ethyl-4-methylhexane is a branched alkane in petrol. Draw the skeletal formula of this alkane. [1 mark] . Give the equation for the complete combustion of 3-ethyl-4-methylhexane. Use the molecular formula for 3-ethyl-4-methylhexane in your equation. [2 marks] Turn over ► box This question is about reactions of halogenoalkanes with hydroxide ions. box . Outline the mechanism for the nucleophilic substitution reaction of 1-bromobutane with sodium hydroxide. [2 marks] A student investigated the rate of nucleophilic substitution of halogenoalkanes with hydroxide ions. Identical concentrations of 1-bromobutane and 1-iodobutane were reacted separately with sodium hydroxide solution under the same conditions. The concentration of halide ions was monitored during each experiment. Figure 1 shows the student’s results. Figure 1 . State how Figure 1 shows that the rate of reaction of 1-iodobutane is faster than the rate of reaction of 1-bromobutane. box State why the rates are different. [2 marks] Turn over for the next question *07* Turn over ► 0 4 1-Methylcyclohexene and limonene are cyclic alkenes with a citrus smell. 1-Methylcyclohexene is manufactured and used in the chemical industry. Limonene is found naturally in orange peel. box 0 4 . 2 Draw the skeletal formula of the minor product formed in the reaction in Question 04.1. Explain why the products are formed in different amounts. [4 marks] Skeletal formula Explanation . Draw the structure of the major product when an excess of HBr reacts with limonene. [1 mark] Turn over for the next question Turn over ► 0 5 A student is provided with a 0.0300 mol sample of an alcohol. The student decides to identify the alcohol using an experiment to determine its enthalpy of combustion. Figure 2 shows the apparatus used. Figure 2 . The student finds that when all the alcohol is burned, the temperature of the water increases from 18.9 °C to 78.1 °C Calculate the enthalpy of combustion, in kJ mol–1, for the alcohol. The specific heat capacity of water, c = 4.18 J g–1 K–1 [3 marks] Enthalpy of combustion kJ mol–1 . Table 2 shows the enthalpies of combustion of some alcohols. Table 2 Alcohol Enthalpy of combustion / kJ mol–1 Ethanol –1367 Propan-1-ol –2021 Butan-1-ol –2676 Explain how your answer to Question 05.1 suggests that the alcohol is butan-1-ol. (If you have been unable to obtain an answer for Question 05.1, assume that the answer is –2120 kJ mol–1) box [2 marks] Question 5 continues on the next page Turn over ► . The equation for the complete combustion of gaseous pentan-1-ol is shown. CH3(CH2)3CH2OH(g) + 71 O2(g) → 5 CO2(g) + 6 H2O(g) ΔH= –3388 kJ mol–1 2 Table 3 shows some bond enthalpy data. Table 3 box C–H C–O O–H C=O O=O Bond enthalpy / kJ mol –1 412 360 463 805 496 Use data from Table 3 to calculate a value for the mean C–C bond enthalpy in pentan-1-ol. [3 marks] C–C bond enthalpy kJ mol–1 . The energy stored in fuels can be compared using energy density values measured in kJ dm–3 Calculate the energy density of butan-1-ol. enthalpy of combustion of butan-1-ol = –2676 kJ mol–1 density of butan-1-ol = 0.810 kg dm–3 relative molecular mass (Mr) of butan-1-ol = 74.0 [2 marks] box Energy density kJ dm–3 Turn over for the next question Turn over ►