June 2022: AS Paper 2, Depth in chemistry

Mark scheme

Examiner's comment

Most candidates scored this mark. Some candidates referred to acids having or containing H+ ions rather than indicating that H+ ions are donated or released. A small number of candidates gave simplistic responses in terms of pH only.

Notes from the mark scheme and report

• releases H+ ions/proton donor

Mark scheme

Examiner's comment

Again, this was well answered by most candidates. A few candidates gave responses in terms of pH or indicated that there were more OH- ions present.

Notes from the mark scheme and report

• partially dissociates/ionises
• IGNORE 'poor proton donor' and 'doesn't easily dissociate'
• Some candidates described a solution with a low concentration of H+ ions, demonstrating a confusion between concepts of weak and dilute in reference to acids. Visual picture cards can be very helpful in assessing understanding of these concepts. This topic is covered at GCSE and resources can be found here: http://www.ocr.org.uk/Images/363946-ph-scale-lesson- element.doc

Mark scheme

Examiner's comment

Although most candidates gained some marks here, there were a significant number who did not gain all 4 marks. Some candidates need to practice reading burettes and recording their values – this can be checked during practical work. The most common errors included not recording values to 2 decimal places (especially if final number was 0), readings recorded the wrong way round in the table, and misreading 0.05 as 0.5. Most candidates were able to identify concordant results, but some still calculated the mean from all values. This led to an average that needed to be rounded to the nearest 0.05, as asked for in the question, resulting in them losing both the mean titre mark and mark for accuracy. Some had errors which lead to values which weren’t concordant – this should be a flag to students that they have made a mistake.

Notes from the mark scheme and report

• all six burette readings correct
• mean from concordant titres 27.30 and 27.40 only (27.35)
• all values to 2 d.p. ending in 0 or 5
• ALLOW ECF from incorrect readings but mean must use closest titres

Skills: M1.1 Use an appropriate number of significant figures; M1.2 Find arithmetic means; PAG2 Acid–base titration

Mark scheme

Examiner's comment

Most candidates managed to gain at least 1 mark for this question. The most common mark lost was for not multiplying by 10, having missed that only 25cm3 of 250 cm3 citric acid solution was used in the titration. Another mark that was often lost was for not dividing by 2 to find mass in 1 lime rather than the 2 used in experiment. Some candidates used 25cm3 to calculate their moles of NaOH rather than the titre value from (i). It is vital that candidates are given the opportunity to practice more complex multi-step calculations of this type, with modelling given for lower-attaining candidates. Identifying which information goes with each reactant is vital. All steps in the calculation should be separate and clearly labelled to help avoid confusion. Encourage candidates to keep full values in their calculators to avoid intermediate step rounding. When writing down intermediate values, ideally write down the full calculator value or where this is not possible the value must be given to at least 3 significant figures (correctly rounded). It is helpful to the examiner to know if calculator values are used and this could be indicated by using truncated answers followed by … , for example 0.00729… for n(A). The exemplar shows a response where each step of the calculation is shown clearly. The candidate has also used pictures to aid them, recognising that the NaOH is in the burette and lime juice in the conical flask. All values are identified and there is no intermediate rounding. All 5 marks are given here.

Notes from the mark scheme and report

• 1:3 ratio citric acid:NaOH
• ×10 scale-up from 25.0 to 250 cm3
• ÷2 because two limes used
• ALLOW ECF from titre in (b)(i) and through all steps

Skills: M0.0 Recognise and make use of appropriate units in calculations; M0.2 Use ratios, fractions and percentages; M2.3 Substitute numerical values into algebraic equations using appropriate units for physical quantities; PAG2 Acid–base titration

Mark scheme

Examiner's comment

A very challenging question with very few candidates scoring both marks. The response needed a clear indication of how the method would be altered and a justification for why this would work. Lots of candidates recognised the need to dilute the citric acid to obtain the correct titre but were not able to give a method of how to do this or any indication of quantities needed. Some candidates said to use a larger volume of NaOH – not recognising that this would be the titre value, e.g. “in order to keep the same titre but lower concentration of NaOH the student should titre more NaOH”. Some gave the method of how to dilute the NaOH or even just said to add water. A few suggested using a higher concentration of lime juice. Candidates need to be given opportunities to plan practical work to fully appreciate the impact that any changes will have (specification 1.1.1).

Notes from the mark scheme and report

• use half a lime or make up juice in 1 dm3 volumetric flask
• justified by factor of 4 (NaOH 4 times more dilute)
• ALLOW any feasible method giving dilution factor of 4
• Further information about practical skills assessed on written exams can be found in section 3 of the practical skills handbook - https://www.ocr.org.uk/Images/208932-chemistry-practical- skills-handbook.pdf. If using our suggested practicals, then encourage candidates to answer the extension opportunity questions to help develop a deeper understanding in preparation for written assessments.

Skills: M0.2 Use ratios, fractions and percentages; PAG2 Acid–base titration

Mark scheme

Examiner's comment

Despite oxidation of alcohols being a topic that has been assessed many times, candidates found this question very tricky with a majority failing to score any marks. Candidates needed to correctly identify this as a secondary alcohol which, when oxidised, will become a ketone. A wide range of errors were seen, including the following: Other errors included forming C=C or removing COOH. Approximately half of those that got the correct structure were also able to balance the equation gaining both marks. Some forgot that another product was formed or gave H2 instead. Candidates were given the structure and told to use [O] to represent the oxidising agent. However, some attempted to use structural or molecular formula and/or adding in dichromate to their answers.

Notes from the mark scheme and report

• secondary alcohol group oxidised to ketone HOOCCH2COCOOH
• COOH groups unchanged

Mark scheme

Examiner's comment

Around half of all candidates did not score this mark. The most common error was giving SrO as the product rather than the hydroxide. Other errors included incorrect balancing (missing 2 on H2O, SrOH as the formula of the hydroxide and no hydrogen formed (often giving H2O instead)).

Notes from the mark scheme and report

• Sr + 2H2O → Sr(OH)2 + H2
• IGNORE state symbols
• Regular practice writing formulae and balancing chemical equations will help to consolidate these concepts, avoiding basic errors such as giving formula of group 2 hydroxide as SrOH.

Mark scheme

Examiner's comment

Most candidates managed to score at least 1 mark for this question. The most common reason for losing a mark, despite demonstrating a good understanding of redox, was stating that H changed from +2 to 0 (need to give oxidation number per atom). Other errors seen included only giving change for Sr, descriptions in terms of electrons rather than oxidation numbers, Sr change from 0 to +1 (linked to SrOH), oxygen being reduced rather than H and mixing up oxidation/reduction or not specifying.

Notes from the mark scheme and report

• Sr 0 to +2 oxidation, H +1 to 0 reduction
• '+' sign required
• 1 mark if all numbers correct but oxidation/reduction reversed or not given

Mark scheme

Examiner's comment

Most candidates gained some marks here although a significant proportion were unable to score all 3 marks covering atomic radius, shielding, nuclear attraction/IE. The mark most often missed was for shielding. Some candidates did not answer the question asked and gave the trend down the group so could not be given marks unless they made it clear Sr is below Ca in the group. Care must be taken to answer question asked not similar questions they have seen before. The best responses were those with direct comparative statements, e.g. “Ca has a smaller atomic radius than Sr”. It is worth noting that harder/easier to lose electrons didn’t gain marks, but was seen fairly frequently, as response needs to be in terms of energy required or linked to nuclear attraction.

Notes from the mark scheme and report

• comparison needed for each mark
• Ca smaller radius/fewer shells, less shielding, greater nuclear attraction/higher ionisation energy
• IGNORE nuclear charge
• IGNORE fewer orbitals/sub-shells

Mark scheme

Examiner's comment

Most candidates gained this mark. The most common incorrect response was pH 7 with a few giving a pH value of less than 7.

Notes from the mark scheme and report

• any value in range 8–14

Mark scheme

Examiner's comment

Most candidates were able to give the formula of the barium compound as BaSO4. However, they did not recognise that this would cause a white ppt to be seen, presumably as not in the context of qualitative ions testing. Many candidates said they would see bubbling/fizzing. Some gave a colour change as they were possibly considering what would be seen if an indicator is present. Others mentioned a precipitate but with no colour given. Some candidates gave the incorrect formula, such as Ba2SO4 or Ba(SO4)2, again showing the importance of practising writing formulae. In addition, some candidates wrote out the whole equation for the reaction.

Notes from the mark scheme and report

• white precipitate
• BaSO4
• We have produced a topic support pack to assist with learning about the reaction of group 2 elements and their compounds: http://www.ocr.org.uk/Images/364103-chemistry-of-group- 2.docx

Skills: PAG4 Qualitative analysis of ions

Mark scheme

Examiner's comment

Only a small number of candidates managed to score all 3 marks for this question. Lots began their response describing why the rate is high at the start. This often filled the space available with marks being gained only in the last sentence. Very few gave descriptions with this specific reaction in mind, such as recognising that the HCl was the limiting reagent so gets used up, leaving some MgCO3 remaining. Common errors included referring to “fewer collisions” but without any indication of time, or “less reactant” without considering the volume of the reaction. We have produced a delivery guide on rates with some useful resources to help consolidate ideas and avoid misconceptions such as these: https://www.ocr.org.uk/Images/231742-rates-delivery-guide.pdf

Notes from the mark scheme and report

• acid CONCENTRATION decreases (IGNORE amount)
• fewer collisions per second/less frequent ('fewer collisions' alone not linked to rate)
• stops when acid/limiting reagent used up
• Many candidates described a decrease in energy in the reaction or gave responses related to activation energy. For example: “lose energy and start to collide less often”, “reactants have less kinetic energy” and “only a certain number of particles which have enough energy above the activation energy…over time energy will decrease and less particles have enough energy”.

Skills: M3.1 Translate information between graphical, numerical and algebraic forms

Mark scheme

Examiner's comment

Most candidates recognised that they needed to draw a tangent. Candidates need to be instructed to draw their line clearly and make sure that it covers several large squares on the graph – preferably extending to the axes. The range given for the calculated rate from the gradient of the tangent was generous, however some did not realise that the y-axis started at 91.0 so incorrectly calculated their gradient. Some candidates used interpolation so gained no marks.

Notes from the mark scheme and report

• tangent drawn at t = 50 s (±10 s)
• DO NOT ALLOW interpolation/direct reading - must be a gradient
• range 5.7 × 10^-3 to 6.9 × 10^-3
• IGNORE units and sign
• ALLOW ECF from incorrect tangent
• M3 section of the Maths Skills handbook contains useful information on use of graphs in chemistry, including M3.5 on drawing and using the slope of the tangent to a curve as a measure of a rate of change: https://www.ocr.org.uk/Images/295468-chemistry-mathematical- skills-handbook.pdf

Skills: M3.1 Translate information between graphical, numerical and algebraic forms; M3.5 Draw and use the slope of a tangent to a curve as a measure of rate of change; PAG9 Rates of reaction – continuous monitoring

Mark scheme

Examiner's comment

About a third of candidates didn’t score any marks here. Some did not follow the instructions to add their curve to the previous graph. The sketches produced in the blank space then usually lacked any scales on the axes so could not be given marks. Lines added were often inaccurately drawn with lines often extending below 91.55g before returning to this mass at the end. It was often difficult to interpret if a graph levelled off before the original with lots tracking the same curve with a very slightly steeper slope. Some gave a slower rate but did manage to gain marks for finishing at 91.55g.

Notes from the mark scheme and report

• steeper slope AND levels off earlier
• same loss in mass - levels off at about 91.55 g

Skills: M3.1 Translate information between graphical, numerical and algebraic forms; PAG9 Rates of reaction – continuous monitoring

Mark scheme

Examiner's comment

Candidates found this question very challenging. Most recognised that the addition of the catalyst would speed up the reaction but could not translate this into observations for this specific practical. For example, “reacts faster”, “releases more hydrogen” or “stops reacting quicker”. Giving candidates the opportunity to observe a range of both familiar and unfamiliar reactions, noting qualitative observations can help to improve their skills here. Many just noted that one tube would be blue and the other colourless rather than considering the reaction taking place. Some indicated that only 1 tube would react and the other would not. A few candidates recognised that a competing displacement reaction would take place between Zn and CuSO4 so were given marks for this.

Notes from the mark scheme and report

• more vigorous bubbling
• zinc dissolves more quickly
• one alternative mark for Cu displacement (red/brown solid or blue solution turns colourless)

Mark scheme

Examiner's comment

Less than half of all candidates managed to gain all 3 marks giving the correct enthalpy profile diagram. Many demonstrated a lack of understanding about what an enthalpy profile diagram shows as seen by labelling of curves for Ea/Ec rather than the enthalpy change or arrows for ∆H extending to the x-axis. Other errors also seen included, -ΔH, double headed ΔH arrow, activation energy lines starting at products, endothermic profiles, Ea and Ec the wrong way round and missing or incorrect labels. Some candidates found it tricky to give activation lines for both catalysed and uncatalysed reactions on the same diagram, these often overlapped or did not extend to the top of the energy barrier.

Notes from the mark scheme and report

• products below reactants with ∆H arrow downwards (DO NOT ALLOW –∆H or double-headed arrow)
• Ea and Ec arrows from reactant level to top of curve, Ec < Ea
• ECF for Ea/Ec on endothermic diagram

Skills: M3.1 Translate information between graphical, numerical and algebraic forms

Mark scheme, with the levels and indicative points

Examiner's comment

Only a small number of candidates were given all 6 marks for their response. Many responses made little or no reference to equilibrium, considering only the rate of reaction. A clear understanding of the difference between rate and equilibrium was essential to scoring highly on this question. Excellent descriptions were given regarding the role of the catalyst on the rate of reaction, possibly influenced by the previous question. Some gave detailed responses in terms of the impact of both pressure and temperature on the equilibrium position but then did not give the changes made by industry such as reducing temperature due to energy demand or increasing pressure to increase rate. Some candidates indicated that 15atm was a low pressure including reference to it being “lower than normal atmospheric pressure” which suggested that they did not understand either the measurement in atmospheres and/or scale of pressure. A common incorrect response was to suggest that a higher pressure gives increased yield as more moles on right/products. Some stated that the reaction was exothermic, clearly confusing the enthalpy change signs. Some also described the “endothermic side” demonstrating a lack of understanding that enthalpy changes require a difference between products and reactants. Many did not correctly consider the use of excess of steam to increase concentration of reactant and shift equilibrium to products/right but talked in terms of limiting reagents, e.g. “This is used so all of the methane is reacted” or increased collisions. Many were prone generalisations, e.g. “These conditions are used industrially to achieve the most hydrogen efficiently with the least amount of undesired (waste) products”. Candidates need to be encouraged to plan their answers, even using subheadings to organise information and follow the key approach: point, evidence, explain. Candidates should also be encouraged to re-read their answers to check communication is clear and accurate without any contradictory statements. Many included irrelevant or inaccurate information such as describing the toxicity of carbon monoxide, so reducing yield of that being beneficial, or “using a catalyst improves atom economy”. This exemplar shows a candidate who achieved L3 with all 6 marks given. They have considered both the effect of temperature and pressure on equilibrium and potential compromises used industrially. They have also considered the impact of using a catalyst. Their response is logically structured and has a clear line of reasoning.

Notes from the mark scheme and report

• endothermic so high temperature shifts right
• 2 mol gas to 4 mol so low pressure favours products but reduces rate
• compromise pressure
• high temperature costs energy
• catalyst increases rate without changing equilibrium position
• excess steam shifts right
• This question was good at highlighting candidates understanding of the impact of different conditions on equilibrium reactions. We have produced a delivery guide to help with teaching about equilibrium: https://www.ocr.org.uk/Images/261544-equilibrium.pdf

Mark scheme

Examiner's comment

This question was well answered with most candidates scoring both marks. Common errors seen included: inverse Kc expression, final answer not to 3 significant figures, adding rather than multiplying concentrations, calculator error ([H2]2 instead of [H2]3) or transcription errors (e.g. using 0.11 rather than 0.111).

Notes from the mark scheme and report

• 3 SF (24.1)
• ALLOW ECF to 3 SF only from inverted expression (0.0414)
• DO NOT ALLOW + signs in expression
• IGNORE units

Skills: M0.2 Use ratios, fractions and percentages; M1.1 Use an appropriate number of significant figures; M2.3 Substitute numerical values into algebraic equations using appropriate units for physical quantities

Mark scheme

Examiner's comment

Despite the structures being drawn out with displayed formula, a significant number of candidates did not correctly count all the bonds. Common errors included missing C-C from ethanol or O-H bonds in water. Most candidates set out their working clearly, so it was easy to identify any errors in calculation steps and award ECF appropriately. Some also had the calculation the wrong way round (made – broken) missing the essential idea that energy is needed to break bonds and released to make bonds, as well as link to endothermic changes being positive and exothermic changes being negative.

Notes from the mark scheme and report

• common errors for 2 marks: –198 (cycle reversed), –149 (missed C–C), –2586 (missed 6 O–H from 3H2O)
• DO NOT ALLOW – sign on final answer
• It is important to evaluate candidates understanding of enthalpy changes and build on prior knowledge from KS4. We have produced a transition guide for KS4 to KS5 on enthalpy: https://www.ocr.org.uk/Images/361305-enthalpy-changes-ks4-ks5.pdf. This includes a checkpoint task which is very useful for checking understanding of this topic, including the difference between endothermic and exothermic reaction, drawing profile diagrams, and calculating enthalpy changes from bond enthalpies.

Skills: M0.2 Use ratios, fractions and percentages; M2.3 Substitute numerical values into algebraic equations using appropriate units for physical quantities

Mark scheme

Examiner's comment

Candidates continue to find understanding of shapes of molecules a very challenging topic to grasp. Very few were able to gain all 4 marks, with most gaining little or no marks. The most common mark given was for lone pairs repelling more than bonding pairs. Many only stated a lone pair decreases bond angle by 2.5o but did not explain that this was caused by increased repulsion. The most common error was stating that CO2 has 2 bonding pairs – it doesn’t, as it has 4 bonding pairs which are arranged as 2 double bonds. They could also state that it has 2 bonding regions. Lots stated CO2 has no lone pairs and H2O has 2 lone pairs but without reference to bonding pairs of electrons so lost out on 2 marks. In fact, it was fairly common that candidates indicated that only lone pairs cause repulsion, e.g. stating no repulsion in CO2 “no lone pairs so there will be no repulsion”. Though these two molecules are ones candidates will have prior knowledge of before A Level, a range of bond angles were suggested. The most successful candidates drew out dot cross diagrams and/or displayed formula to be able to count pairs of electrons around the central atom.

Notes from the mark scheme and report

• 180° and 104.5° (ALLOW 104–105)
• CO2 two bonding regions/double bonds
• H2O two bonded pairs AND two lone pairs
• lone pairs repel more
• IGNORE names of shapes
• DO NOT ALLOW atoms repel

Skills: M4.1 Use angles and shapes in regular 2-D and 3-D structures

Mark scheme

Examiner's comment

Most candidates gave the correct response to this question. Incorrect responses included use of high temperatures and/or catalyst.

Notes from the mark scheme and report

• UV
• ALLOW sunlight
• IGNORE temperature

Mark scheme

Examiner's comment

Candidates always find radical mechanisms tricky and this one had the added complexity of forming 2- bromo isomer. However, a majority of students still gained marks. Many candidates formed the incorrect radical removing H from C-1 i.e. CH3CH2CH2CH2• therefore scoring only 1 mark. Some responses were a little messy making it very easy to miss off a dot or H or Br. Many candidates reacted with Br• in the first step but added Br to the radical intermediate (as well as forming HBr). Candidates should always check equations so that they balance in terms of atoms.

Notes from the mark scheme and report

• radical must be CH3CH2•CHCH3 (1 mark if CH3CH2CH2CH2• used or both equations correct with molecular formulae)
• dots required

Mark scheme

Examiner's comment

Candidates found this question very challenging and few scored both marks. Many responses considered only the formation of HBr (other product) and/or general statements about other products with no indication of how they were formed. Some described losses due to the purification method or incomplete reaction (due to conditions such as T and P) or low atom economy. Some referred to the stability of the radical intermediate, showing possible confusion with electrophilic addition. Candidates who understood the mechanism were more confident in answering this question, at least recognising that further substitution was possible.

Notes from the mark scheme and report

• further substitution/di- and tribromobutanes or other termination products
• substitution at a different position (1-bromobutane)

Mark scheme

Examiner's comment

Despite the question asking for calculations to be included, many candidates didn’t include them and so lost both marks. Some gained one mark as recognised that 5.1 has 100% atom economy but either didn't or incorrectly calculated for 5.2 (30% was seen frequently). Care needs to be taken with rounding of final values.

Notes from the mark scheme and report

• Reaction 5.1 atom economy 136.9/217.8 × 100 = 62.9%
• Reaction 5.2 is 100% (addition, one product)

Skills: M0.2 Use ratios, fractions and percentages

Mark scheme

Examiner's comment

The most common errors were omitting the yield or inverting the yield, as given on mark scheme, resulting in 2 marks. Clear working was vital here to help marks to be given even if the final answer was incorrect. Many candidates did not gain the final mark due to incorrect significant figures. As with other multi-step calculations, rounding of intermediate values could also cause marks to be lost.

Notes from the mark scheme and report

• common errors for 2 marks: 5.41 g (no % yield), 3.62 g (yield inverted)
• 3 SF required (8.07
• 8.06 accepted from intermediate rounding)

Skills: M0.2 Use ratios, fractions and percentages; M1.1 Use an appropriate number of significant figures; M2.2 Change the subject of an equation; M2.3 Substitute numerical values into algebraic equations using appropriate units for physical quantities

Mark scheme

Examiner's comment

This question was not answered well with over half the candidates failing to score any marks. While some candidates seemed familiar with the techniques required, describing the process to separate the layers, they often struggled to name the separating funnel. Common approaches were to attempt to ‘filter’ the layers or to use heat (via evaporation or distillation) to drive off the water. Some attempted to use Na2CO3 or NaOH to dry the organic layer – perhaps confusing neutralisation of any remaining acid. Although distillation appeared frequently many did not give the temperature so did not gain marks. The order of the procedure was also not always clear with distillation before using a drying agent. Some described attempts to crystallise the organic layer. The range of answers suggests students may need more practical experience with separating organic liquids.

Notes from the mark scheme and report

• separating funnel to separate layers
• dry organic layer with anhydrous salt (MgSO4, CaCl2)
• distil and collect fraction at 91 °C

Skills: PAG5 Synthesis of an organic liquid

Mark scheme, with the levels and indicative points

Examiner's comment

About a third of candidates were given Level 3 for this question. The key to answering this style of question well is to make sure all the information provided is used and to avoid contradictory statements, e.g. “structure contains carboxylic acid from IR” but then not present in final structure drawn, or a structure that doesn’t match the molecular formula given. A significant number of candidates did not include C=C despite being told in the question that it was “unsaturated and is a trans stereoisomer”, plus the C=C bond is shown in the IR and molecular formula needed unsaturation. The M+1 peak did confuse some candidates who then tried to add an extra H to final structure. It is very important that any structure given is feasible in terms of bonding; many candidates gave structures with C with 5 bonds (with both C=C and C=O attached), limiting them to achieving only L1. Some candidates gave a cis structure rather than trans. Other candidates ignored the O-H peak (from the carboxylic acid) in the IR spectrum, attributing this to a C-H bond as it was not as smooth or as prominent as they may have seen in other spectra. Some listed the bonds observed in the IR without linking to their position – this can easily be done by annotating the spectra. Many candidates had messy answers with lots of rough working which was then not crossed out – this made their answer very confusing. Note that no marks were given for just the empirical formula calculation and some attempted to produce a structure from the empirical formula without determining the Mr from the M+ peak in mass spectrum. This is an example of a good response which achieved L3 6 marks. Empirical and molecular formula are determined. Spectra have been annotated to aid their interpretation, but they have also included the key IR peaks as well as a MS fragment in their response. The correct structure for A is clearly drawn out. The response is clear and concise, with all information presented being relevant. If any of your students’ results are not as expected, you may wish to consider one of our post-results services. For full information about the options available visit the OCR website. We send a weekly roundup to tell you about important updates. You can also sign up for your subject specific updates. If you haven’t already, sign up here. Attend one of our popular CPD courses to hear directly from a senior assessor or drop in to a Q&A session. Most of our courses are delivered live via an online platform, so you can attend from any location. Please find details for all our courses on the relevant subject page on our website or visit OCR professional development. ExamBuilder is the question builder platform for a range of our GCSE, A Level, Cambridge Nationals and Cambridge Technicals qualifications. Find out more. ExamBuilder is free for all OCR centres with an Interchange account and gives you unlimited users per centre. We need an Interchange username to validate the identity of your centre's first user account for ExamBuilder. If you do not have an Interchange account please contact your centre administrator (usually the Exams Officer) to request a username, or nominate an existing Interchange user in your department. Review students' exam performance with our free online results analysis tool. It is available for all GCSEs, AS and A Levels and Cambridge Nationals. It allows you to: • review and run analysis reports on exam performance • analyse results at question and/or topic level • compare your centre with OCR national averages • identify trends across the centre • facilitate effective planning and delivery of courses • identify areas of the curriculum where students excel or struggle • help pinpoint strengths and weaknesses of students and teaching departments. Find out more. Post-results services Keep up-to-date OCR Professional Development Signed up for ExamBuilder?

Notes from the mark scheme and report

• empirical formula C2H3O, M+ 86 so C4H6O2
• broad O–H 2500–3300 and C=O 1630–1820 so carboxylic acid
• peak at 41 from loss of COOH
• CH3CH=CHCOOH drawn as trans isomer with justification (cis or trans accepted for structure)
• We have put together a range of online resources to support teaching of organic chemistry: https://www.ocr.org.uk/qualifications/as-a-level-gce-chemistry-a-h032-h432-from-2015/delivery- guide/module-cam04-module-4-core-organic-chemistry/delivery-guide-cadg012-organic- chemistry-as

Skills: M0.2 Use ratios, fractions and percentages; M3.1 Translate information between graphical, numerical and algebraic forms; M4.2 Visualise and represent 2-D and 3-D forms including 2-D representations of 3-D objects