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OCR A Jun 2015 Paper 2 Q7
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![L, M, N and P are straight-chain organic compounds containing C, H and O only. The flowchart shows reactions involving these compounds. 20 elimination of H2O polymer P Mr ~ 10,000 H+/Cr2O7 2 reflux dicarboxylic acid, M Analysis of compound L shows the following.Relative molecular mass of 90.0.The infrared spectrum below. Percentage composition by mass: C, 40.00%; H, 6.67%; O, 53.33%. IR spectrum of L 100 e c n a t t i m s n a r t 50 0 4000 3000 2000 wavenumber / cm1 1500 1000 500 (a) Calculate the empirical and molecular formulae of compound L. Show your working.[3]OCR 2015<br />
(b) Analyse the information and spectrum to determine the structures of L and M. Include an equation for the reaction of L to form M. 21[5] (c) Determine the structures of compounds N and P. Estimate the number of repeat units in polymer P and write the equation for the formation of P from N.[4] [Total: 12]OCR 2015 END OF QUESTION PAPER<br />](https://learnah.org/wp-content/uploads/2018/08/OCR_2_QP_JUN15_question_7-0.jpg)
![F322 Question 7 (a) Answer Mole ratio C : H : O is 3.33 : 6.67 : 3.33 (cid:57)(cid:3) Empirical formula is CH2O (cid:57)(cid:3) Molecular formula is C3H6O3 AND use of 90 OR 330 (cid:57)(cid:3) Mark Scheme June 2015 Mark Guidance : 6.67 1.0 : 53.33 16.0 ALLOW 40.00 12.0 ALLOW mass of C = 0.400 x 90 or 36 AND mass of H = 0.06677 x 90 or 6 AND mass of O = 0.5333 x 90 or 48 27<br />
F322 Question (b) Mark Scheme June 2015 (1 mark) (1 mark) (2 marks) Answer Evidence of carboxylic acid IR: 15501800 cm1 AND C=O/carbonyl AND 23003700 cm1 AND OH in carboxylic acid (cid:57)(cid:3) Evidence of alcohol (broad) 32003700 cm 1 linked to OH in alcohol OR (is a primary) alcohol as oxidised (to a COOH) OR is an alcohol as it forms a carboxylic acid OR is an alcohol as water is eliminated. (cid:57)(cid:3) Identifications L: M: Equation C3H6O3 + 2[O]C3H4O4 + H2O (cid:57)(cid:3) HOOC COOH COOH (cid:57)(cid:3) HO (cid:57)(cid:3) (1 mark) Mark Guidance ANNOTATE ANSWER WITH TICKS AND CROSSES ETC LOOK ON THE SPECTRUM for labelled peaks which can be given credit ALLOW ranges from Data Sheet: C=O within range 16401750 cm1; (broad) OH within range 25003300 cm1 (broad) OH within range 32003550 cm1 For ALL structures: ALLOW correct structural OR skeletal OR displayed formula OR mixture of the above IGNORE namesFOR M: ALLOW 1 mark for HOOC AS ECF from L as either HO OH HO COOH (cid:57)(cid:3) OH OR Equation: C3H6O3 + 4[O]C3H2O5 + 2H2O (cid:57)(cid:3)ALLOW correct structural OR displayed OR skeletal formula OR mixture of the above in equation 28<br />
F322 Question (c) Mark Scheme June 2015 Answer Monomer N: H COOH (1 mark) (cid:57)(cid:3) H (1 mark) Polymer P: Section showing at least one repeat unit of a polymer formed from N with side links (cid:57)(cid:3) e.g. COOH 29 Mark Guidance For ALL structures: ALLOW correct structural OR skeletal OR displayed formula OR mixture of the above IGNORE names ALLOW 1 mark for either HO CHO CHO AS ECF from L: OH OR OH HOFor P: ALLOW ECF from an alkene with molecular formula C3H4O2 ALLOW one or more repeat units but has to have a whole number of repeat units ALLOW repeat unit with no brackets and absence of n<br />
Mark Scheme June 2015 Mark Guidance MUST be a whole number. ALLOW 138 OR140For equation, ALLOW molecular OR structural OR skeletal OR displayed formulae OR mixture of the above e.g. ALLOW nC3H4O2(C 3H4O2)n n on LHS can be at any height to the left of formula AND n on the RHS must be a subscript (essentially below the side link if displayed/skeletal formula is used) ALLOW use of calculated value for n in equation e.g. 139C3H4O2(C 3H4O2)139 F322 Question Answer (1 mark) Repeat units n = 10000/72 = 139 (cid:57)(cid:3) Equation Balanced equation for formation of P from N(cid:57)(cid:3) e.g. n COOH (1 mark) COOH Total 12 30<br />](https://learnah.org/wp-content/uploads/2018/08/OCR_2_QP_JUN15_answer_7-0.jpg)
