OCR A Jan 2013 Paper 2 Q8 (with explained solutions) |

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OCR A Jan 2013 Paper 2 Q8

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18 8 Compound X is a saturated compound that contains carbon, hydrogen and oxygen only. A scientist analyses a 1.00 g sample of compound X and finds it contains 0.133 g of hydrogen and 0.600 g of carbon. The scientist also analyses compound X using mass spectrometry and infrared spectroscopy. mass spectrum of X 100 80 60 40 20 0.0 10 100 80 60 40 20 20 30 40 m /z 50 60 70 IR spectrum of X 4000 3500 3000 2500 2000 1500 1000 500 wavenumber / cm1 relative abundance (%) transmittance (%)OCR 2013<br />
19 The scientist finds that compound X reacts with ethanoic acid in the presence of a concentrated sulfuric acid catalyst to make compound Y. Compound Y has the molecular formula C5H10O2. Using all the information, show the structures of compounds X and Y. Include an equation for the reaction of compound X with ethanoic acid to make compound Y. In your answer you should link the evidence with your explanation.OCR 2013 Turn over<br />
20[10]OCR 2013 END OF QUESTION PAPER [Total: 10]<br />

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F322/01 Question 8 Mark Scheme January 2013 Answer IR spectrum (absorbance between) 32003550 cm1 indicates OH AND X is an alcohol (cid:57) Marks Formula mole ratio C : H : O 267 .0 600 .0 16 12 133 .0 0.1 OR 0.0500 :0.133 : 0.0167 (cid:57) .0 .0 0167 0167 .0 133 0167 .0 OR 3 : 8 : 1 OR C3H8O (cid:57) 05.0 .0 0167 Candidate links C3H8O to 60 such as C3H8O has Mr 60 OR C3H8O has m/z = 60 (cid:57) Guidance LOOK ON THE SPECTRUM for labelled absorbance which can be given credit ALLOW an absorbance within the range 3100 to 3700cm-1 from the spectrum. Answer must give OH and alcohol for the mark. IGNORE phenol DO NOT ALLOW carboxylic acid (there is no carbonyl group present in the spectrum) Must be a clear link between the formula and the Mr OR m/z ALLOW evidence of Mr , eg (12 x 3) + (8 x 1) + 16; ALLOW alternative approach for empirical formula and evidence that 60 is equal to C3H8O Mr = 60 Carbon Hydrogen 6060 = 36 6013.3 = 8 100 100 36/12 = 3 C 8/1 = 8H 36 + 8 = 44 6044 = 16 so 1 O C3H8O 36 + 8 + 16 = 60 28<br />
F322/01 Question 8 Mark Scheme January 2013 Marks Answer Identification and equation X is CH3CH2CH2OH OR CH3CHOHCH3 OR either CH3CH2CH2OH or CH3CHOHCH3 (cid:57) QWC Stated in words that Y must be an ester because it is made from the reaction of a carboxylic acid AND X (propan-1-ol OR propan-2-ol OR an alcohol) (cid:57) Y is CH3COOCH2CH2CH3 OR CH3COOCH(CH3)2 OR either CH3COOCH2CH2CH3 or CH3COOCH(CH3)2 (cid:57) Must be consistent with a structure of alcohol X m/z = 31 is CH2OH+ (cid:57) QWC m/z = 31 or CH2OH indicates that X must be CH3CH2CH2OH OR cannot be CH3CH(OH)CH3 OR shows that X is the primary alcohol (cid:57) C3H8O + C2H4O2 (cid:198) C5H10O2 + H2O (cid:57) Total 10 29 Guidance ALLOW correct structural OR displayed OR skeletal formula OR mixture of the above (as long as unambiguous) IGNORE names ALLOW a carboxylic acid reacts with an alcohol to give an ester. IGNORE ethanoic acid (as this is stated in the question) ALLOW correct structural OR displayed OR skeletal formula OR mixture of the above (as long as unambiguous) If no structure of X is provided one mark can be awarded for a correct structure of CH3COOCH2CH2CH3 OR CH3COOCH(CH3)2 DO NOT ALLOW CH3O+ QWC must link the evidence to the structure of propan-1-ol. In equation ALLOW correct structural OR displayed OR skeletal formula OR mixture of the above<br />

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