Edexcel Jan 2015 (IAL) Paper 4 Q24

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SECTION C Answer ALL the questions. Write your answers in the spaces provided. 24 (a) Ethanoic acid and ethanol react together to form the ester ethyl ethanoate, CH3COOC2H5, and water. CH3COOH(l) + CH3CH2OH(l) (cid:85) CH3COOCH2CH3(l) + H2O(l) (cid:507)H = 3.5 kJ mol1 (i) Give the expression for the equilibrium constant, Kc, for this reaction. (ii) By considering the effect of temperature on the entropy change of the surroundings, suggest why changing the temperature has little effect on this equilibrium. (1) (3)22 *P45044A02228*<br /> *(iii) An experiment was carried out to determine the value of Kc for this reaction. (cid:404) 0.120 mol of ethanoic acid was added to 0.220 mol of ethanol. (cid:404) 5.00 cm 3 of 1.00 mol dm3 hydrochloric acid was added as a catalyst. This contains 0.278 mol of water. (cid:404) The mixture was left to reach equilibrium. (cid:404) The mixture was titrated with 1.00 mol dm 3 sodium hydroxide, which reacted with both of the acids. (cid:404) The titre was 45.0 cm 3. Use these data to determine the value for Kc. (6) *P45044A02328* 23 Turn over<br /> (2) (2) (b) Ethanoic acid reacts with another alcohol, Y, to produce an ester Z. (i) Alcohol Y has molar mass 74 g mol1 and the following composition by mass: carbon, C = 64.9% hydrogen, H = 13.5% oxygen, O = 21.6%. Use all these data to confirm that the molecular formula for Y is C4H10O. Show your working. (ii) Draw the displayed formulae of the four possible structures of alcohol Y. Alcohol 1 Alcohol 2 Alcohol 3 Alcohol 4 24 *P45044A02428*<br /> (iii) The mass spectrum of alcohol Y has a major peak at m/e = 45. Suggest the structures of two species that could give this peak. (iv) Use your answers to (b)(ii) and (b)(iii) to identify which two of the alcohols you have drawn in (b)(ii) could be alcohol Y. (v) Complete the displayed formulae for the two possible esters that could be Z. (2) (1) (1) *P45044A02528* 25 Turn over<br /> *(vi) The high resolution proton nmr spectrum of ester Z is shown below. Chemical shift, (cid:303)(cid:3)/ ppm The relative number of protons causing the peaks shown are: A = 1, B = 3, C = 2, D = 3 and E = 3. Use the nmr spectrum to determine the structural formula for ester Z that is consistent with this data. Draw your formula below and on it label the protons responsible for the peaks A to E. Explain the splitting patterns of the spectrum. (5) Structure 26 *P45044A02628*<br /> Explanation of splitting patterns(Total for Question 24 = 23 marks) TOTAL FOR SECTION C = 23 MARKS TOTAL FOR PAPER = 90 MARKS *P45044A02728* 27<br />

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