OCR_A level_Chemistry_Paper 3_2020 | SPS F108 12.3_Carbonyl Compounds, Carboxylic Acids, Esters & Polyesters

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SPS F108 12.3_Carbonyl Compounds, Carboxylic Acids, Esters & Polyesters_A level_OCR_Chemistry_Paper 3 Carbonyl Compounds, Carboxylic Acids, Esters & Polyesters Question Paper 3 Level A Level Exam... Board OCR Sub-Topic Time Allowed: 78 minutes Score: /65 Percentage: /100 Grade Boundaries: A* A B C D E U >85% 77.5% 70% 62.5% 57.5% 45% <45% 1 A chemist prepares and analyses some esters. (a) The chemist prepares an ester of propan-2-ol, CH3CH(OH)CH3, by reacting CH3CH(OH)CH3 with ethanoic anhydride, (CH3CO)2O. Using structural formulae, write an equation for the reaction of propan-2-ol and ethanoic anhydride. [2] (b) A sample contains a mixture of two esters contaminated with an alkane and an alcohol. The chemist attempts to separate the four organic compounds in the mixture using gas chromatography, GC. The column in the gas chromatograph contains a liquid alkane which acts as the stationary phase. (i) How does a liquid stationary phase separate the organic compounds in a mixture? ........................................................................................................................................ ...................................................................................................................................... [1] (ii) Suggest how well these four compounds would be separated using the alkane stationary phase. In your answer, include some indication of the length of the retention times. Explain your answer. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ...................................................................................................................................... [2] (c) GC is often used together with other techniques, such as mass spectrometry, MS, and NMR spectroscopy, to provide a far more powerful analytical tool than GC alone. One of the esters in a perfume is separated by GC and then analysed. The results are shown below. Elemental analysis by mass C, 66.63%; H, 11.18%; O, 22.19% Mass spectrum 100 80 relative 60 intensity 40 20 0 0 25 50 75 100 125 150 m / z Proton NMR spectrum The numbers by each peak are the relative peak areas. 5 4 δ / ppm Use the results to identify the ester. Show all your reasoning. - - - - [Show More]

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