Version 1.1 : 07/07 abc General ertificate of Education hemistry 641 M4 Further Physical and rganic hemistry Mark Scheme 007 examination - June series
Mark schemes are prepared by the Principal Examiner and considered, together with the relevant questions, by a panel of subject teachers. This mark scheme includes any amendments made at the standardisation meeting attended by all examiners and is the scheme which was used by them in this examination. The standardisation meeting ensures that the mark scheme covers the candidates responses to questions and that every examiner understands and applies it in the same correct way. As preparation for the standardisation meeting each examiner analyses a number of candidates scripts: alternative answers not already covered by the mark scheme are discussed at the meeting and legislated for. If, after this meeting, examiners encounter unusual answers which have not been discussed at the meeting they are required to refer these to the Principal Examiner. It must be stressed that a mark scheme is a working document, in many cases further developed and expanded on the basis of candidates reactions to a particular paper. Assumptions about future mark schemes on the basis of one year s document should be avoided; whilst the guiding principles of assessment remain constant, details will change, depending on the content of a particular examination paper. Further copies of this Mark Scheme are available to download from the AQA Website: www.aqa.org.uk opyright 007 AQA and its licensors. All rights reserved. PYRIGT AQA retains the copyright on all its publications. owever, registered centres for AQA are permitted to copy material from this booklet for their own internal use, with the following important exception: AQA cannot give permission to centres to photocopy any material that is acknowledged to a third party even for internal use within the centre. Set and published by the Assessment and Qualifications Alliance. The Assessment and Qualifications Alliance (AQA) is a company limited by guarantee registered in England and Wales (company number 364473) and a registered charity (registered charity number 1073334). Registered address: AQA, Devas Street, Manchester M15 6EX Dr Michael resswell Director General
M 4 Question 1 (a) (i) kpa -1 not 1/kPa (ii) p = = ( p ( p ) S 3 S ) K p 90.8 10.6 x 1.4 one mark for correct rearrangement of expression to give p =. one mark for insertion of correct numbers into acorrect expression These can be in either order = 51.7 (allow 51.6 51.9) (b) (i) increase equilibrium moves to fewer gas moles or fewer moles on RS (ii) none (iii) T equilibrium moves in endothermic direction or to LS or forward reaction is exothermic (c) (i) 0.08 (T 0.085) (ii) pp = mole fraction total pressure (iii) mark consequentially on (i) R one mark for correct rearrangement of (mol fn S expression to give P =. 3) x P K p = [(mol fn S ) x P ][(mol fn ) x P] must specify substances P = 0.17 0.75 x 0.08 x 1.4 one mark for insertion of correct numbers into a correct expression These steps can be in either order Question = 171 (kpa) (a) (i) p = -log[ + 1 ] must be [ ] allow log + [ ] (ii) 0.437 or 0.44 Total 14 (b) (i) 3 + + 3 ignore spectator ions 3 + + + R 3 3
(ii) metacresol purple bromophenol blue (iii) 40 3 0.150 = 6.0 10 10 (iv) mol l = 1.0 10 (consequential on (iii)) must score this to gain nd mark) 1.0 x 10 conc = 50.0 x 10 = 0.4 mol dm Total 9 Question 3 penalise p with decimal places once per paper (a) + [ ] K a = [ 3 ] 5.13 (if miss square root) [ + ] = (1.35 10-5 0.55) =.7 10 3 gets p =.56 or.57 (b) (i) 30.0 10 3 0.55 = 1.65 10 or 0.017 ( at least sig figs) (ii) 10.0 10 3 0.3 =.30 10 3 or 0.003 ( at least sig figs) (iii) (1.65 10 ) - (.30 10 3 ) = 1.4 10 i.e. (i) (ii) above if addition not subtraction, also penalise first mark gained in (iv) (iv) if any mention of [ + ] /[A] max 1 for moles of salt mol 3 a =.30 10 3 (may be scored in the expression) [ + ] = or = Ka x [ 3 ] - [ ] 3 (1.35 x 10-5 ) (.3 x 10 (1.4 x 10 /V) - /V) * (1.4 x 10-5 ) (1.4 x 10 (.3 x 10 /V) - /V) = 8.33 10 5 = 8.5 10 5 p = 4.08 p = 4.07 Total 9 * expression may be p = pka + log[salt/acid] or pka log[acid/salt] if addition, 3.96.97 gets two in part (iv) 4
Question 4 (a) (i) k = 0. 65 ( 0. 15)( 0. 4) if k upside down, max 1 for consequential units = 75.3 to 74.7 mol dm -6 s (+ mol - dm 6 s -1 (ii) 0.081 (min sig. figs required) (ignore wrong units) may be consequential on their k i.e. (1.08 10 ) their k (b) (i) (ii) 0 Total 6 5
Question 5 (a) (i) 3 3 (ii) 3 3 3 a ot allow covalent -a 3 3 (b) 3 ( ) 4 3 (c) allow and zwitterions and dipeptide cyclic(- ) Total 6 allow but not 6
Question 6 (a) (i) -methylbutan-1-ol (numbers essential) (ii) optical (b) (i) elimination not nucleophilic nor any other qualification not just dehydration (ii) 3 3 penalise 3 each time addition or radical (QL) i.e. not additional (iii) or 3 3 3 3 allow 5 = 3 (iv) (c) (i) 3 3 allow 5 5 (ii) reflux (QL) (d) I M II J III K IV L (e) (i) 400 1500 cm -1 allow range from [0-600] to [100 1500] (ii) M1 compare with spectrum of known compound / database M1 must be gained to score M M exact match or fingerprint unique Total 16 7
Question 7 (a) conc 3 if both conc missing can score one for both acids conc S 4 if omitted can score one for reagents in the equation ignore temp/reflux etc 3 + S 4 + + 3 + - + S 4 or 3 + S 4 + - + + S 4 or 3 + + + + (or in two equations) + 3 + + or or + or 6 6 or 6 5 electrophilic substitution M1 M structure M1 arrow from within hexagon to or to + on don t penalise position of + on of + (3) horseshoe must not extend beyond M3 arrow to 6 but can be smaller + not too close to 1 M3 arrow into hexagon unless Kekule (b) 1,4-dinitrobenzene Sn or Fe/l (conc or dil or neither) ignore extra a Sn or Fe/ S 4 (dil or neither) not 3 at all or /i not ab 4 / LiAl 4 or a/ 5 + 1[] + 4 allow 6 4 ( ) and 6 4 ( ) allow 6 lone pair or electron pair on in Y delocalised into ring (QL) less available for protonation than lp in Z (c) not 4 8 4 ignore [ ] or n () but must have trailing bonds allow -- () Total 16 8
Question 8 (a) (i) -methylpropanamide nucleophilic addition-elimination M 3 M1 3 l 3 3 l M3 for structure M4 for 3 arrows and lone pair (4) R must show a bond to - to gain M1 penalise :l - attacking in M4 (ii) 3 3 allow 5 so minimum is ( 5 ) +. (iii) 3 3 3 + + 3. (3) * or 4 9 +. be lenient on position of + and dot (b) Reaction 1 ucleophilic addition 3 Reaction /i a/ethanol or LiAl 4 hydrogenation or reduction reduction * if you suspect erratum sheet was not circulated, 3 + is 57 +. allow 3 3 3 +.. + 3 or 4 Total 14 9