OCR AS Level Chemistry A Past Paper PDF 2023

Oxford Cambridge and RSA Tuesday 16 May 2023 – Morning AS Level Chemistry A H032/01 Breadth in chemistry Time allowed: 1 hour 30 minutes You must have:...

Oxford Cambridge and RSA Tuesday 16 May 2023 – Morning AS Level Chemistry A H032/01 Breadth in chemistry Time allowed: 1 hour 30 minutes You must have: * 9 8 8 0 6 2 3 6 5 1 * the Data Sheet for Chemistry A You can use: a scientific or graphical calculator an HB pencil * H 0 3 2 0 1 * Please write clearly in black ink. Do not write in the barcodes. Centre number Candidate number First name(s) Last name INSTRUCTIONS Use black ink. You can use an HB pencil, but only for graphs and diagrams. Write your answer to each question in the space provided. If you need extra space use the lined pages at the end of this booklet. The question numbers must be clearly shown. Answer all the questions. Where appropriate, your answer should be supported with working. Marks might be given for using a correct method, even if your answer is wrong. INFORMATION The total mark for this paper is 70. The marks for each question are shown in brackets [ ]. This document has 24 pages. ADVICE Read each question carefully before you start your answer. © OCR 2023 [601/5256/4] OCR is an exempt Charity DC (RW/CT) 315826/4 Turn over  2 SECTION A You should spend a maximum of 25 minutes on this section. Write your answer to each question in the box provided. 1 Which statement explains the trend in boiling points down the halogens group? A Covalent bonds become stronger. B Induced dipole–dipole interactions (London forces) become stronger. C Ionic bonds become stronger. D Permanent dipole–dipole interactions become stronger. Your answer 2 A hydrocarbon contains 85.71% carbon by mass. What is the empirical formula of the hydrocarbon? A CH B CH2 C CH4 D C 2H 4 Your answer 3 Hydrogen can be prepared industrially by the reaction of methane with steam. The equation is shown below. CH4(g) + 2H2O(g) 4H2(g) + CO2(g) What is the atom economy of hydrogen for this process? A 3.8% B 4.3% C 15.4% D 17.4% Your answer © OCR 2023  3 4 How many p-orbitals are occupied by electrons in a sulfur atom? A 2 B 4 C 6 D 10 Your answer 5 Which substance has the lowest oxidation number for sulfur? A Na2SO4 B S8 C SF2 D SO2 Your answer 6 Successive ionisation energies, in kJ mol–1, of an element in Period 3 of the periodic table are shown below. 1st 2nd 3rd 4th 5th 6th 7th 8th 9th 578 1817 2745 11578 14831 18378 23296 27460 31862 What is the formula of the oxide of the Period 3 element? A Na2O B MgO C Al 2O3 D SiO2 Your answer © OCR 2023 Turn over  4 7 How many oxygen atoms are in 120.2 g of SiO2? A 3.01 × 1023 B 1.20 × 1024 C 2.41 × 1024 D 3.61 × 1024 Your answer 8 Magnesium nitrate, Mg(NO3)2, decomposes when heated: Mg(NO3)2(s) MgO(s) + 2NO2(g) + ½O2(g) 0.00250 mol of Mg(NO3)2 is decomposed. What is the volume of gas produced, measured at RTP? A 30 cm3 B 60 cm3 C 120 cm3 D 150 cm3 Your answer 9 Zinc reacts with aqueous silver nitrate, as shown in the equation: Zn(s) + 2AgNO3(aq) 2Ag(s) + Zn(NO3)2(aq) 0.10 g of zinc is added to 15 cm3 of 0.25 mol dm–3 aqueous silver nitrate. What is the mass of silver metal that would be formed? A 0.16 g B 0.20 g C 0.33 g D 0.40 g Your answer © OCR 2023  5 10 15.00 cm3 of 18.0 mol dm–3 concentrated hydrochloric acid is diluted with water to prepare 250 cm3 of dilute hydrochloric acid. What is the concentration, in mol dm–3, of the dilute hydrochloric acid? A 0.0675 B 0.270 C 0.300 D 1.08 Your answer 11 The standard enthalpy change of formation of water is –286 kJ mol–1. Which statement or equation is correct? A H2(g) + ½O2(g) H2O(l) ΔH o = –143 kJ mol–1 B 2H2(g) + O2(g) 2H2O(l) ΔH o = –286 kJ mol–1 C The O–H bond enthalpy is –143 kJ mol–1. D The standard enthalpy change of combustion of hydrogen is –286 kJ mol–1. Your answer 12 Which statement about energy changes is correct? A Combustion of an alkane is endothermic. B In an exothermic reaction, more energy is needed to break bonds than is given out when bonds are made. C The activation energy is a negative value. D The enthalpy change for the condensation of a gas to a liquid is a negative value. Your answer © OCR 2023 Turn over  6 13 The Boltzmann distribution showing the activation energy, Ea, for an uncatalysed reaction is shown below. number of molecules Ea energy What is the difference for the catalysed reaction? A The activation energy shifts to the left. B The activation energy shifts to the right. C The curve flattens. D The curve shifts to the right. Your answer © OCR 2023  7 14 A student measures how the OH– concentration changes over time for a reaction. The student plots the graph below. 0.20 0.15 [OH–(aq)] / mol dm–3 0.10 0.05 0.00 0 100 200 300 400 500 600 time / s What is the rate of reaction, in mol dm–3 s–1, at 200 s? A 2.2 × 10–4 B 2.8 × 10–4 C 1.8 × 10–3 D 4.4 × 10–2 Your answer © OCR 2023 Turn over  8 15 Which formula does not represent 3-methylbut-1-ene? A CH3CHCH3CHCH2 B CH2CHCH(CH3)2 C D Your answer 16 How many structural isomers have the molecular formula C4H9Cl ? A 2 B 3 C 4 D 5 Your answer © OCR 2023  9 17 3-Methylcyclohexanol is reacted with NaBr and H2SO4. What is the organic product? Br Br Br A Br Br Br B C D Your answer © OCR 2023 Turn over  10 18 A student has planned the two-stage synthesis shown below. H 3C H OH OH C C Intermediate H 3C C C H H 3C H CH3 H Which compound could be the intermediate for this synthesis? H H H H H H A H 3C H C H C H H 3C C C H H 3C C C H H 3C C CH3 C H H CH3 H CH3 H CH3 H Br H Br H Br H H 3C Br C H C H B H 3C C C H H 3C C C H H 3C C CH3 C H H CH3 H CH3 H CH3 H OH H OH H OH H H 3C OH C H C H H 3C C C H C H 3C C C H H 3C C CH3 C H H CH3 H CH3 H CH3 H Br Br Br Br Br Br H 3C Br C Br C H H 3C C C H H 3C C C H D H 3C C CH3 C H H CH H CH33 H CH3 H Your answer © OCR 2023  11 19 An organic compound produces the infrared spectrum below. 100 transmittance 50 (%) 0 4000 3000 2000 1500 1000 500 wavenumber / cm–1 Which compound could have produced this IR spectrum? A CH3CH2CH=CH2 B CH3CHOHCH2CH3 C CH3CH2COCH3 D (CH3)2CHCOOH Your answer 20 Pentan-2-ol and pentan-3-ol are structural isomers with the molecular formula C5H12O and Mr = 88. The isomers can be distinguished from the fragment ions in their mass spectra. Which fragment ion would you expect to be present in only one of these isomers? A m/z = 29 B m/z = 45 C m/z = 59 D m/z = 73 Your answer © OCR 2023 Turn over  12 SECTION B 21 This question is about NF3 and BF3 molecules. (a) NF3 and BF3 contain covalent bonds. (i) What is meant by a covalent bond?...................................................................................................................................... (ii) Draw ‘dot-and-cross’ diagrams for NF3 and BF3. Show outer electrons only. NF3 BF3 (b) Molecules of NF3 and BF3 have different shapes and bond angles. (i) Predict the different shapes of, and bond angles in, NF3 and BF3 molecules. Bond angle Name of shape NF3 BF3 (ii) Explain why NF3 and BF3 molecules have different shapes and bond angles......................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... © OCR 2023  13 22 This question is about reactions involving acids. (a) Hydrochloric acid and nitric acid are classified as strong acids. What is meant by a strong acid?................................................................................................................................................................................................................................................................................................. (b) Write equations for the reactions below. State symbols are not required. (i) The reaction of copper(II) oxide with dilute hydrochloric acid....................................................................................................................................... (ii) The reaction of ammonium carbonate with dilute nitric acid....................................................................................................................................... © OCR 2023 Turn over  14 (c) A student carries out an investigation to identify an unknown Group 1 metal M. The student reacts 2.62 g of the Group 1 metal, M, with water. A solution of the alkali, MOH(aq), is formed. The student makes this solution of MOH(aq) up to 250.0 cm3 with water. The student pipettes 25.0 cm3 of this MOH(aq) solution into a conical flask. The student titrates this 25.0 cm3 volume of MOH(aq) with 0.165 mol dm–3 H2SO4(aq). The equation is shown below. 2MOH(aq) + H2SO4(aq) M2SO4(aq) + 2H2O(l) (i) Name the type of flask that the student should use to make up the 250.0 cm3 solution of MOH(aq)....................................... flask (ii) The student takes burette readings to the nearest 0.05 cm3. The student’s readings are shown in the table. The rough titre has been omitted. Complete the table below. Final reading 20.25 40.85 25.85 / cm3 Initial reading 0.00 20.25 5.50 / cm3 Titre / cm3................................................................................................ (iii) Calculate the mean titre of H2SO4, to the nearest 0.05 cm3, that the student should use to analyse the results. mean titre =................................................... cm3 © OCR 2023  15 (iv) Calculate the amount, in mol, of MOH in 25.0 cm3 of solution and determine the identity of the Group 1 metal M. metal M =.......................................................... © OCR 2023 Turn over  16 23 This question is about enthalpy changes. (a) In a petrol engine, alkanes undergo combustion. (i) Heptane is one of the alkanes in petrol. Write the equation for the complete combustion of heptane. State symbols are not required....................................................................................................................................... (ii) In a petrol engine, polluting gases such as CO and NO are formed. These are mostly removed before being emitted from the exhaust. The equation for the removal of CO and NO is shown below. 2CO(g) + 2NO(g) 2CO2(g) + N2(g) ΔH = –746 kJ mol–1 Complete the enthalpy profile diagram in Fig. 23.1 for this reaction. On your diagram: Label the enthalpy change of reaction, ΔH. Include the formulae of the reactants and products. Label the activation energy, Ea. Fig. 23.1 enthalpy progress of reaction © OCR 2023  17 (iii) CO and NO are removed by use of a catalyst. Explain the role of the catalyst. Refer to your enthalpy profile diagram in Fig. 23.1 in your answer........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ (b) Iron(III) oxide reacts with carbon monoxide as shown: Fe2O3(s) + 3CO(g) 2Fe(s) + 3CO2(g) ΔH = –25 kJ mol–1 Standard enthalpy changes of formation, Δ f H o, are given in the table. Substance Δ f H o / kJ mol–1 Fe2O3(s) –824 CO(g) –111 (i) State the conditions of temperature and pressure for standard enthalpy changes. Temperature...................................................................................................................... Pressure....................................................................................................................... (ii) Calculate the standard enthalpy change of formation for CO2(g). Δ f H o (CO2(g)) =............................................ kJ mol–1 © OCR 2023 Turn over  18 24 The reaction between sulfur dioxide, SO2(g) and oxygen, O2(g), to form sulfur trioxide, SO3(g), is a key step in the industrial manufacture of sulfuric acid. This is a reversible reaction, shown in Equilibrium 24.1: 2SO2(g) + O2(g) 2SO3(g) ΔH = –197 kJ mol–1 Equilibrium 24.1 (a) Why is Equilibrium 24.1 a homogeneous equilibrium?................................................................................................................................................................................................................................................................................................. (b) Le Chatelier’s principle can be used to predict how different conditions affect the equilibrium position in Equilibrium 24.1. Explain how changing pressure, temperature and using a catalyst affect the equilibrium yield of SO3. In your answer, use le Chatelier’s principle and other chemical concepts, where appropriate............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................. © OCR 2023  19 (c) A mixture of SO2(g) and O2(g) is allowed to reach equilibrium at a constant temperature. The equilibrium concentrations are shown in the table. Equilibrium concentration Substance / mol dm–3 SO2(g) 3.0 × 10–3 O2(g) 3.5 × 10–3 SO3(g) 5.0 × 10–2 (i) Write the expression for Kc and calculate the numerical value for Kc in Equilibrium 24.1 at this constant temperature. Give your answer to an appropriate number of significant figures and in standard form. Kc =......................................... dm3 mol–1 (ii) In the industrial production of SO3, an excess of O2(g) is used rather than a 2:1 proportion of SO2(g) to O2(g) which would match the stochiometry in Equilibrium 24.1. Suggest, in terms of equilibrium, why an excess of O2(g) is used industrially............................................................................................................................................................................................................................................................................................................................................................................................................................. © OCR 2023 Turn over  20 25 This question is about hydrocarbons. (a) The boiling points of 2 hydrocarbons are shown below. Hydrocarbon Boiling point / °C butane 0 pentane 36 Explain the difference in the boiling points of butane and pentane........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... (b) Butane reacts with bromine by radical substitution to form a mixture of organic products. The reaction needs UV radiation for the initiation stage. Write equations for the propagation stage that follows to form 2-bromobutane. Use skeletal formulae and ‘dots’ ( ) to show the position of any radicals. Propagation © OCR 2023  21 (c) Alkenes are used in organic synthesis. Three reactions of an alkene are shown in the flowchart. Complete the flowchart to show the missing reagents, catalysts and the structures of organic products. H H H 3C C C CH3 H H alkane Reagent........................................ Catalyst......................................... H 3C CH3 HBr C C H H bromoalkane Reagent........................................ Catalyst......................................... alcohol © OCR 2023 Turn over  22 26 This question is about the oxidation of two alcohols that are structural isomers of C3H8O. Compare the oxidation of these two structural isomers using different reaction conditions. For each reaction include: the reaction conditions the functional group of any organic product a balanced equation. In your equations, use [O] to represent the oxidising agent and show any organic compounds as structures.................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................. END OF QUESTION PAPER © OCR 2023  23 ADDITIONAL ANSWER SPACE If additional space is required, you should use the following lined page(s). 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