Chemistry (7404/2) - Science Above
ASChemistry(7404/2)Paper 2: Organic and Physical ChemistrySpecimen 2015 v0.5Session1 hour 30 minutesMaterialsFor this paper you must have: the Data Sheet, provided as an insert a ruler a calculator.Instructions Answer all questions.Show all your working.Information The maximum mark for this paper is 80.Please write clearly, in block capitals, to allow character computer recognition.Centre numberCandidate numberSurnameForename(s)Candidate signatureBarcodev0.57404/2
2Section AAnswer all questions in this section.1Compound J, known as leaf alcohol, has the structural formulaCH 3 CH 2 CH CHCH 2 CH 2 OH and is produced in small quantities by many green plants.The E isomer of J is responsible for the smell of freshly cut grass.0 1 . 1Give the structure of the E isomer of J.0 1 . 2Give the skeletal formula of the organic product formed when J is dehydrated usingconcentrated sulfuric acid.[1 mark]Barcode[1 mark]Typesetter code
30 1 . 3Another structural isomer of J is shown below.CH3CH2CH3CH2OHCCHExplain how the Cahn-Ingold-Prelog (CIP) priority rules can be used to deduce the fullIUPAC name of this compound.[6 marks]Question 1 continues on the next pageBarcodeTypesetter codeTurn over
40 1 . 4The effect of gentle heat on maleic acid is shown below.A student predicted that the yield of this reaction would be greater than 80%.In an experiment,10.0 g of maleic acid were heated and 6.53 g of organic productwere obtained.Is the student correct? Justify your answer with a calculation using these data.[2 marks]BarcodeTypesetter code
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62Figure 1 shows apparatus used in an experiment to determine the enthalpy ofcombustion of leaf alcohol.Figure 150.0 g sample of waterThe alcohol is placed in a spirit burner and weighed. The burner is lit and the alcoholallowed to burn for a few minutes. The flame is extinguished and the burner isre-weighed. The temperature of the water is recorded before and after heating.Table 1 shows the results obtained.Table 10 2 . 1BarcodeInitial mass of spirit burner and alcohol / g56.38Final mass of spirit burner and alcohol / g55.84Initial temperature of water / C20.7Final temperature of water / C40.8Write an equation for the complete combustion of leaf alcohol(CH 3 CH 2 CH CHCH 2 CH 2 OH).Typesetter code[1 mark]
70 2 . 2Use the results from Table 1 to calculate a value for the enthalpy of combustion ofleaf alcohol. Give units in your answer.–1 –1(The specific heat capacity of water is 4.18 J K g )[4 marks]Enthalpy of combustion 02 . 3Units State how your answer to Question 2.2 is likely to differ from the value quoted inreference sources.Give one reason for your answer.[2 marks]Question 2 continues on the next pageBarcodeTypesetter codeTurn over
802 . 4A 50.0 g sample of water was used in this experiment.Explain how you could measure out this mass of water without using a balance.[2 marks]BarcodeTypesetter code
932-bromo-2-methylpentane is heated with potassium hydroxide dissolved in ethanol.Two structural isomers are formed.0 3 . 1State the meaning of the term structural isomers.[1 mark]0 3 . 2Name and draw the mechanism for the formation of one of the isomers.[5 marks]Name of mechanismMechanismTurn over for the next questionBarcodeTypesetter codeTurn over
104Glucose can decompose in the presence of microorganisms to form a range ofproducts. One of these is a carboxylic acid (M r 88.0) containing 40.9% carbon and4.5% hydrogen by mass.0 4 . 1 Deduce the empirical and molecular formulas of the carboxylic acid formed.Empirical formula [4 marks]Molecular formula 0 4 . 2 Ethanol is formed by the fermentation of glucose.A student carried out this fermentation reaction in a beaker using an aqueous solutionof glucose at a temperature of 25 C in the presence of yeast.Write an equation for the reaction occurring during fermentation.[1 mark]0 4 . 3 In industry, this fermentation reaction is carried out at 35 C rather than 25 C.Suggest one advantage and one disadvantage for industry of carrying out thefermentation at this higher temperature.[2 marks]AdvantageDisadvantageBarcodeTypesetter code
110 4 . 4 The method used by the student in Question 4.2 would result in the ethanol beingcontaminated by ethanoic acid.How does this contamination occur?[1 mark]0 4 . 5 Give two differences between the infrared spectrum of a carboxylic acid and that of analcohol other than in their fingerprint regions.Use Table A on the Data Sheet.[2 marks]Difference 1Difference 2Turn over for the next questionBarcodeTypesetter codeTurn over
125CCl 4 is an effective fire extinguisher but it is no longer used because of its toxicity andits role in the depletion of the ozone layer. In the upper atmosphere, a bond in CCl 4breaks and reactive species are formed.0 5 . 1 Identify the condition that causes a bond in CCl 4 to break in the upper atmosphere.Deduce an equation for the formation of the reactive species.[2 marks]ConditionEquation0 5 . 2 One of the reactive species formed from CCl 4 acts as a catalyst in the decompositionof ozone.Write two equations to show how this species acts as a catalyst.[2 marks]Equation 1Equation 2–40 5 . 3 A small amount of the freon CF 3 Cl with a mass of 1.78 10 kg escaped from a3refrigerator, into a room of volume 100 m . Assuming that the freon is evenlydistributed throughout the air in the room, calculate the number of freon molecules in a3volume of 500 cm .Give your answer to the appropriate number of significant figures.23–1The Avogadro constant 6.02 10 mol .[3 marks]Number of molecules BarcodeTypesetter code
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146Dodecane (C 12 H 26 ) is a hydrocarbon found in the naphtha fraction of crude oil.Dodecane can be used as a starting material to produce a wide variety of usefulproducts. The scheme in Figure 2 shows how one such product, polymer Y, can beproduced from dodecane.Figure 2Reaction 1C 12 H 26C2H4C4H8 XReaction 2nC 4 H 8HCH3CCCH3 HnPolymer Y0 6 . 1 Name the homologous series that both C 2 H 4 and C 4 H 8 belong to.Draw a functional group isomer of C 4 H 8 that does not belong to this homologousseries.[2 marks]NameFunctional group isomer0 6 . 2 Identify compound X.0 6 . 3 Name polymer Y.Barcode[1 mark][1 mark]Typesetter code
150 6 . 4 Reaction 1 is an example of thermal cracking and is carried out at a temperatureof 750 C.State one other reaction condition needed.[1 mark]0 6 . 5 Reaction 2 is exothermic. A typical compromise temperature of 200 C is usedindustrially for this reaction.Explain the effect of a change of temperature on both the position of equilibrium andthe rate of reaction, and justify why a compromise temperature is used industrially.[6 marks]BarcodeTypesetter codeTurn over
167A student carried out an experiment to determine the number of C C double bonds ina molecule of a cooking oil by measuring the volume of bromine water decolourised.The student followed these instructions: 3Use a dropping pipette to add 5 drops of oil to 5.0 cm of inert organic solvent in aconical flask.Use a funnel to fill a burette with bromine water.Add bromine water from a burette to the solution in the conical flask and swirl theflask after each addition to measure the volume of bromine water that isdecolourised.The student’s results are shown in Table 2.Table 2Experiment Volume of bromine water / cm30 7 . 1139.40243.50341.20In a trial experiment, the student failed to fill the burette correctly so that the gapbetween the tap and the tip of the burette still contained air.Suggest what effect this would have on the measured volume of bromine water in thistrial. Explain your answer.[2 marks]0 7 . 2 Other than incorrect use of the burette, suggest a reason for the inconsistency in thestudent’s results.[1 mark]BarcodeTypesetter code
170 7 . 3 Outline how the student could improve this practical procedure to determine thenumber of C C double bonds in a molecule of the oil so that more consistent resultsare obtained.[4 marks]–30 7 . 4 The oil has a density of 0.92 g cm and each of the 5 drops of oil has a volume of–235.0 10 cm .The approximate M r of the oil is 885–2–3The concentration of bromine water used was 2.0 10 mol dm .Use these data and the results from experiment 1 to deduce the number of C Cdouble bonds in a molecule of the oil.Show your working.[5 marks]Number of C C double bonds BarcodeTypesetter codeTurn over
18Section BAnswer all questions in this section.Only one answer per question is allowed.For each answer completely fill in the circle alongside the appropriate answer.CORRECT METHODWRONG METHODSIf you want to change your answer you must cross out your original answer as shown.If you wish to return to an answer previously crossed out, ring the answer you now wish to selectas shown.0 8Which of these samples of gas contains the largest number of molecules?–1–1The gas constant R 8.31 J K mol .[1 mark]0 9–436–335A5.0 10 m at 1.0 10 Pa and 300 KB4.0 10 m at 2.0 10 Pa and 400 KC3.0 10 dm at 3.0 10 Pa and 500 KD2.0 10 dm at 4.0 10 Pa and 600 K134233Which of these substances has permanent dipole-dipole attractions betweenmolecules?[1 mark]BarcodeACCl 4BC2F4C(CH 3 ) 2 CODCO 2Typesetter code
191 0What is the total volume of gas remaining after 20 cm3 ethane are burned completelyin 100 cm3 oxygen? All volumes are measured at the same pressure and the sametemperature, which is above 100 C.[1 mark]1C 2 H 6 32O 21 1A40 cm3B100 cm3C120 cm3D130 cm32CO 2 3H 2 OConsider the reaction between propene and hydrogen bromide to form the majorproduct.Which species is formed in the mechanism of this reaction?[1 mark]1 2Barcode ACH 3 –C H–CH 2 BrBCH 3 –CHBr–C H 2CCH 3 –C H–CH 3DCH 3 –CH 2 –C H 2 Which of these substances reacts most rapidly to produce a silver halide precipitatewith acidified silver nitrate?[1 mark]ACH 3 BrBCH 3 ClCCH 3 FDCH 3 ITypesetter codeTurn over
201 31 41 5BarcodeWhich statement about E-1,2-dichloroethene is correct?[1 mark]AIt has the same boiling point as Z-1,2-dichloroethene.BIt forms a polymer with the same repeating unitas Z-1,2-dichloroethene.CIt has the same IR spectrum as Z-1,2-dichloroethenein the range 400–1500 cm–1.DIt has a molecular ion peak different from that ofZ-1,2-dichloroethene in its mass spectrum.Which statement about ethene is correct?[1 mark]AIt has no geometric isomers because there is free rotationaround the C C bond.BIt reacts with HBr in a nucleophilic addition reaction.CIt burns in excess oxygen to produce carbon dioxide and water.DThe C C bond is twice as strong as the C–C bond in ethane.Which statement about ethanal is correct?[1 mark]AIt reacts with Tollens’ reagent to form silver.BIt has a higher boiling point than ethanol.CIts empirical and molecular formulas are different.DIt belongs to a homologous series with general formula C n H 2n 1 OTypesetter code
211 6Which of these substances does not contribute to the greenhouse effect?[1 mark]AUnburned hydrocarbons.BCarbon dioxide.CWater vapour.DNitrogen.Questions 17 and 18 are about a method that can be used to prepare ethylamine.CH 3 CH 2 Br 2NH 31H1 7HHCCHH 2CH 3 CH 2 NH 2 NH 4 Br3NH3HBrHHHCCNHHHNH3H4Which of the curly arrows in the mechanism is not correct?[1 mark]1 8A1B2C3D4Which statement about the reaction is not correct?[1 mark]BarcodeAEthylamine is a primary amine.BThe mechanism is a nucleophilic substitution.CUsing an excess of bromoethane will prevent further reactionto form a mixture of amine products.DAmmonium bromide is an ionic compound.Typesetter codeTurn over
22Questions 19 and 20 are about the Maxwell–Boltzmann distribution of molecularenergies in a sample of a gas shown in Figure 3.Figure 3Number ofNumber ofmoleculesmoleculesAX B Y1 9ZCEnergyEnergyDWhich letter best represents the mean energy of the molecules?[1 mark]ABCD2 0What does the area under the curve represent?[1 mark]BarcodeAThe total energy of the particles.BThe total number of particles.CThe number of particles that can react with each other.DThe total number of particles that have activation energy.Typesetter code
23The apparatus in Figure 4 was set up to measure the time taken for 20.0 cm3 ofsodium thiosulfate solution to react with 5.0 cm3 of hydrochloric acid in a 100 cm3conical flask at 20 C. The timer was started when the sodium thiosulfate solution wasadded to the acid in the flask. The timer was stopped when it was no longer possibleto see the cross on the paper.Figure 42 12 2What is likely to decrease the accuracy of the experiment?[1 mark]ARinsing the flask with acid before each new experiment.BStirring the solution throughout each experiment.CUsing the same piece of paper for each experiment.DUsing different measuring cylinders to measure the volumesof acid and sodium thiosulfate.The experiment was repeated at 20 C using a 250 cm3 conical flask.Which statement is correct about the time taken for the cross to disappear when usingthe larger conical flask?[1 mark]AThe time taken will not be affected by using the larger conical flask.BThe time taken will be decreased by using the larger conical flask.CThe time taken will be increased by using the larger conical flask.DIt is impossible to predict how the time taken will be affected byusing the larger conical flask.END OF QUESTIONSBarcodeTypesetter codeTurn over
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AQA QualificationsASChemistryPaper 2 (7404/2): Organic and Physical ChemistryMark scheme7404Specimen paperVersion 0.5
MARK SCHEME – AS Chemistry – Specimen paper 2Question01.1Marking H2OH2 of 14
MARK SCHEME – AS Chemistry – Specimen paper 2Extended response01.3Maximum of 5 marks for answers which do not show asustained line of reasoning which is coherent,relevant, substantiated and logically structured.Stage 1: consider the groups joined to right hand carbon of theC C bondConsider the atomic number of the atoms attached1AO1aC has a higher atomic number than H, so CH 2 OH takes priority1AO2aBoth groups contain C atoms, so consider atoms one bond furtheraway1AO2aC, (H and H) from ethyl group has higher atomic number than H, (Hand H) from methyl group, so ethyl takes priority1AO2aThe highest priority groups, ethyl and CH 2 OH are on same side ofthe C C bond so the isomer is Z1AO2aThe rest of the IUPAC name is 3-methylpent-2-en-1-ol1AO2aM1 can be scored in stage 1 or stage 2Stage 2: consider the groups joined to LH carbon of the C C bondStage 3: conclusionAllow M5 for correct ECF conclusion using either orboth wrong priorities deduced in stages 1 and 23 of 14
MARK SCHEME – AS Chemistry – Specimen paper 201.4Moles of maleic acid 10.0/116.0 8.62 10–2AND mass of organic product expected (8.62 10–2 ) 98.0 8.45 gOr moles of organic product formed 6.53 / 98.0 6.66 10–21AO3 1a1AO3 1a% yield 100 6.53/8.45OR 100 (6.66 10–2) / (8.62 10–2) 77.294 77.3%AND statement that the student was NOT correct4 of 14
MARK SCHEME – AS Chemistry – Specimen paper 2QuestionMarking guidance1202.1C 6 H 11 OH02.2Temperature rise 20.1 8 O26CO 2 6H 2 Oq 50.0 4.18 20.1 4201 (J)MarkAO1AO2a1AO2h1AO2h1AO2h1AO1aCommentsMass of alcohol burned 0.54 g and M r alcohol 100.0 mol of alcohol n 0.54/100 0.0054Heat change per mole q/1000n OR q/n 778 kJ mol–1 OR 778 000 J mol–1ΔH –778 kJ mol–1 OR –778 000 J mol–1M4 is for answer with negative sign for exothermicreactionUnits are tied to the final answer and must match02.302.4Less negative than the reference1AO3 1bHeat loss OR incomplete combustion OR evaporation of alcoholOR heat transferred to beaker not taken into account1AO3 1bWater has a known density (of 1.0 g cm–3)1AO3 2a1AO3 2a3Therefore, a volume of 50.0 cm could be measured out5 of 14
MARK SCHEME – AS Chemistry – Specimen paper 2QuestionMarking guidanceMarkAO03.1(Compounds with the) same molecular formula but different structural /displayed / skeletal formula1AO1a03.2(basic) eliminationMechanism points:1AO1aCorrect arrow from lone pair on :OH– to H on C adjacent to C–Br1AO2aCorrect arrow from C–H bond to C–C1AO2aCorrect arrow from C–Br bond to BrStructure of chosen H3OH6 of 14
MARK SCHEME – AS Chemistry – Specimen paper 2Question04.1Marking guidanceMarkAO1AO1b1AO2b1AO2bTherefore, molecular formula is same as the empirical formula - C 3 H 4 O 31AO2bC 6 H 12 O 61AO1aPercentage of oxygen by mass 100 – 40.9 – 4.5 54.6%Divide by A rDivide by smallest CHO40.9124.5154.616 3.41 4.5 3.413.41 13.41Nearest whole number ratio 1 34.5 1.323.413.41 3.411.32 31 3Comments1 3 : 3.96 : 3Nearest integer ratio 3:4:3Empirical formula C 3 H 4 O 3Empirical formula mass 88 molecular formula mass04.22C 2 H 5 OH 2CO 27 of 14
MARK SCHEME – AS Chemistry – Specimen paper 204.3Advantage – ethanol is produced at a faster rate1AO2eDisadvantage – more energy is used / required in the reaction1AO2e04.4Air gets in / oxidation occurs1AO1a04.5Alcohol OH absorption in different place (3230–3550 cm–1) from acid OHabsorption (2500–3000 cm–1)1AO2eThe C O in acids has an absorption at 1680–1750 cm–11AO2e8 of 14
MARK SCHEME – AS Chemistry – Specimen paper 2Question05.1Marking guidanceUV lightCCl 3 CCl 405.2Cl O3ClO O 305.3 ClClO O 2Cl 2O M r of CF 3 Cl 104.5–43–3Moles freon 1.78 10 10 / 104.5 1.70 10–32321Number of molecules 1.70 10 6.02 10 1.02 1021–6Molecules in 500 cm3 (1.02 10 500 10 ) / 10015 5.10 10Allow answer in the range 5.10–5.13 1015Answer must be given to this precision9 of 14
MARK SCHEME – AS Chemistry – Specimen paper 2Question06.1Marking O1a1AO2aCorrectly drawn molecule of cyclobutane or methylcyclopropane, need not be displayed formulaAllow hexane or any other correctly named alkanewith 6 carbonsCHCHORH06.2C 6 H 14 (or correct alkane structure with 6 carbons)1AO2a06.3Poly(but-2-ene)1AO1a06.4High pressure1AO1bAllow pressure 1 MPaMention of catalyst loses the mark10 of 14
MARK SCHEME – AS Chemistry – Specimen paper 206.5This question is marked using levels of response. Refer to the MarkScheme Instructions for Examiners for guidance on how to markthis question.Level 3All stages are covered and the explanation of each5–6stage is generally correct and virtually complete.marksAnswer communicates the whole process coherentlyand shows a logical progression from stage 1 and stage2 (in either order) to stage 3.Level 23–4marksAll stages are covered but the explanation of eachstage may be incomplete or may contain inaccuraciesOR two stages are covered and the explanations aregenerally correct and virtually complete.Answer is mainly coherent and shows progression.Some steps in each stage may be out of order andincomplete.Level 11–2marksTwo stages are covered but the explanation of eachstage may be incomplete or may contain inaccuracies,OR only one stage is covered but the explanation isgenerally correct and virtually complete.Answer includes isolated statements but these are notpresented in a logical order or show confusedreasoning.Level 00 marks61 AO1aIndicative chemistry content5 AO2aStage 1: consider effect of higher temperature onyield(Or vice versa for lower temperature) Le Chatelier’s principle predicts that equilibriumshifts to oppose any increase in temperature Exothermic reaction, so equilibrium shifts inendothermic direction / to the left So a Higher T will reduce yieldStage 2: consid
Chemistry (7404/2) Paper 2: Organic and Physical Chemistry Specimen 2015 v0.5 Session 1 hour 30 minutes Materials For this paper you must have: the Data Sheet, provided as an insert a ruler a calculator. Instructions Answer all questions. Show all your working. Information The maximum mark for this paper is 80. Please write clearly, in block capitals, to allow character .
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Chemistry is the science that describes matter, its properties, the changes it undergoes, and the energy changes that accompany those processes. Inorganic chemistry Organic chemistry Physical chemistry Biochemistry Applied Chemistry: Analytical chemistry, Pharmaceutical Chemistry, . Istv an Szalai (E otv os University) Lecture 1 6 / 45
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