CHM4 Further Physical and Organic Chemistry

Size: px

Start display at page:

Download "CHM4 Further Physical and Organic Chemistry"

Mervin Cannon
9 years ago
Views:

1 GE 005 January Series abc Mark Scheme hemistry M4 Further Physical and rganic hemistry 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.

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.

2 Further copies of this Mark Scheme are available to download from the AQA Website: opyright 005 AQA and its licensors. All rights reserved. PYIGT 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 6447 and a registered charity number 074. egistered address AQA, Devas Street, Manchester. M5 6EX. Dr Michael resswell Director General

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

3 Mark Scheme Advanced Subsidiary / Advanced - hemistry Guidance on the award of the mark for Quality of Written ommunication Quality of Written ommunication assessment requires candidates to: select and use a form and style of writing appropriate to purpose and complex subject matter; organise relevant information clearly and coherently, using specialist vocabulary when appropriate; and ensure text is legible, and spelling, grammar and punctuation are accurate, so that meaning is clear. For a candidate to be awarded mark for quality of written communication on the question identified as assessing QW in a unit test, the minimum acceptable standard of performance should be: the longer parts (worth 4 marks or more) should be structured in a reasonably logical way, appropriate and relevant to the question asked; ideas and concepts should be explained sufficiently clearly to be readily understood. ontinuous prose should be used and sentences should be generally be complete and constructed grammatically. owever, minor errors of punctuation or style should not disqualify; appropriate AS/A level terminology should be used. andidates should not use such phrases as fighting disease, messages passing along nerves, enzymes being killed etc, but a single lapse would not necessarily disqualify. Technical terms should be spelled correctly, especially where confusion might occur, e.g. mitosis/meiosis, glycogen/glucagon. The Quality of Written ommunication mark is intended as a recognition of competence in written English. Award of the mark should be based on overall impression of performance on the question identified on the paper as assessing QW. Perfection is not required, and typical slips resulting from exam pressure such as of for off should not be penalised. Good performance in one area may outweigh poorer performance in another. are should be taken not to disqualify candidates whose lack of knowledge relating to certain parts of a question hampers their ability to write a clear and coherent answer; in such cases positive achievement on other questions might still be creditworthy. No allowance should be made in the award of this mark for candidates who appear to suffer from dyslexia or for whom English is a second language. ther procedures will be used by the Board for such candidates. Examiners should record or 0 at the end of the paper in the Quality of Written ommunication lozenge. This mark should then be transferred to the designated box on the cover of the script.

text is legible, and spelling, grammar and punctuation are accurate, so that meaning is clear.

4 hemistry Advanced Subsidiary / Advanced Mark Scheme M 4 Further Physical and rganic hemistry SETIN A Question (a) (i) conc N conc S 4 allow for both acids if either conc missing N + S 4 N S 4 or N + S 4 N S 4 (ii) electrophilic substitution M structure M N N M arrow horseshoe must not extend beyond to 6 but can be smaller + must not be too close to (b) Sn or Fe / l (conc or dil or neither) or Ni / not NaB 4 / LiAl 4 (c) (i) N Use an excess of ammonia (ii) nucleophilic substitution M for structure M 6 5 l 6 5 N N M M4 N 4 (d) lone pair on N less available (in correct context) delocalised into the ring (Q of L) (e) N Br ignore Br + must be on N or outside a square bracket (f) N Total 9 4

not be too close to (b) Sn or Fe / l (conc or dil or neither) or Ni / not NaB 4 / LiAl 4 (c) (i) N Use an excess of ammonia (ii) nucleophilic substitution M for structure M 6 5

5 Mark Scheme Advanced Subsidiary / Advanced - hemistry Question (a) (i) penalise + N or + on once per paper N zwitterion (ii) N (b) N ignore n, but allow one drawn out repeating unit only condensation or (nucleophilic) addition-elimination (c) -methylpent--ene Total 6 Question (a) A any 5 alkene B etc penalise (b) or or or D or (c) E 5

repeating unit only condensation or (nucleophilic) addition-elimination (c)

6 hemistry Advanced Subsidiary / Advanced Mark Scheme F (allow 5 ) (d) G l l l or l l l or l (e) I J (allow 5 ) NT hex--ene Total 0 Question 4 (a) order with respect to P is order with respect to Q is (b) (i) rate = k[][s] (if wrong expression, no further marks) rate = ( ) = (mol dm - s - ) ignore units even if wrong (ii) 5 rate 8.x0 k = = [][S] 0.76 x 0.98 =. 0-4 * (iii) T * If calculated value for k > , then answer to (iii) is T Total 8 6

expression, no further marks) rate = (4. 0-4 ) 0.6 0.84 = 4.

7 Mark Scheme Advanced Subsidiary / Advanced - hemistry Question 5 (a) (i) moles of F = 0.40 mark independently from l moles of l = 0.80 not consequential (ii) K c = [ F4 ][l] wrong K c means they can only score for units in (iii) consequ on their K c [lf ] (iii) K c = ( 0.40 /8.5)(0.80 /8.5) (0.0 /8.5) = 0.5 mol dm (b) (i) increase (ii) decrease (c) addition or radical Question 6 Total 9 (a) butanoyl chloride (b) (i) l has (two) isotopes or 5 l and 7 l (ii) 06 and 08 (c) (nucleophilic) addition-elimination, penalise electrophilic not esterification M l M allow 7 M for structure M4 for arrows and lone pair (only allow for correct M or close) M not allowed independent of M, but allow M for correct attack on + if M shown as independent first. l 4 Total 8 7

5 mol dm (b) (i) increase (ii) decrease (c) addition or radical Question 6 Total 9 (a) butanoyl chloride (b) (i) l has (two) isotopes or 5 l and 7 l (ii) 06 and 08 (c) (nucleophilic)

8 hemistry Advanced Subsidiary / Advanced Mark Scheme Section B Question 7 (a) (i) eagent Tollens Fehlings or Benedicts K r 7 / + KMn 4 / + I /Na or acidified Propanal silver red ppt or goes red goes green goes colourless no (mirror) (not red solution) reaction Propanone no no reaction no reaction no reaction yellow reaction (ppt) (penalise incomplete reagent e.g. K r 7 or r - 7 / + then mark on) (ii) propanal peaks ignore splitting even if wrong propanone peak Total for (a) 5 Marks (b) X is or propanoic acid if both name and formula given, both must be correct, but Y is () or propan--ol allow propanol with correct formula Mark the type of reaction and reagent/condition independently. The reagent must be correct or close to score condition Step xidation K r 7 / + or other oxidation methods as above allow r - 7 / + if penalised above (ecf) reflux (not Tollens/Fehlings) or heat or warm Step reduction or nucleophilic reduction or reduction or addition nucleophilic addition hydrogenation NaB 4 LiAl 4 in (m)ethanol or water or ether or dry ether or dry Ni / Pt etc Step esterification or (nucleophilic) addition-elimination or condensation (conc) S 4 or l warm (allow without acid reagent if X and Y given as reagents) or reflux or heat max 8/9 Total for (b) 0 marks Total for question 5 8

(ii) propanal peaks ignore splitting even if wrong propanone peak Total for (a) 5 Marks (b) X is or propanoic acid if both name and formula given, both must be correct, but Y is () or propan--ol

9 Mark Scheme Advanced Subsidiary / Advanced - hemistry Question 8 (a) p = log[ + ] + [ ] K a = or [ + ] = [A - ] [] [ + ] = (or.6 0 ) p =.79 (penalise dp or more than dp once in the qu) (b) (i) Solution which resists change in p /maintains p despite the addition of (small amounts of) acid/base (or dilution) (ii) + + must show an equation full or ionic in which ethanoate ions are converted to ethanoic acid (c) (i) [ + ] = K a [ [ ] ] if rearrangement incorrect, no further marks = ( = ) p = 4.58 (ii) M moles + added = = 0.0 M moles ethanoic acid after addition = = 0.6 M moles ethanoate ions after addition = = 0.09 M4 [ + ] = K a [ [ ] ( = ) ] = / V 0.09 / V M5 p = 4.5 The essential part of this calculation is addition/subtraction of 0.0 moles to gain marks M and M. If both of these are missing, only mark M is available. Thereafter treat each mark independently, except if the expression in M4 is wrong, in which case both M4 and M5 are lost. Total 5 alternative scheme for part (c)(i) [] p = pk a log [ ] pk a = p = (4.76 log ) = alternative for penultimate mark of part (c)(ii) 0. 6 p = 4.76 log

equation full or ionic in which ethanoate ions are converted to ethanoic acid (c) (i) [ + ] = K a [ [ ] ] if rearrangement incorrect, no further marks =.74 0 5 0.5 0.0 ( =.6 0 5 ) p = 4.

10 hemistry Advanced Subsidiary / Advanced Mark Scheme GENEAL GANI PINTS F MAKING M4. urly arrows These must show the movement of a pair of electrons, i.e. from a bond or a lone pair either to an atom (example ) or to the space between two atoms (example ) Example correct Example correct N Br N Br urly arrows never start at an atom e.g. the right hand arrow in example is wrong Example wrong N Br. Incorrect Structures which are generally penalised once per paper: a) Sticks, i.e. bonds without (hydrogen) atoms on their ends, e.g. b) Incorrectly bonded functional groups e.g. correct N wrong Alkyl groups, however, can be written in several different ways The following alkyl group arrangements are allowed as correct.: N c) cyclohexane for benzene penalised once per paper d) -N + or + N- penalised once per paper 0

g. correct N wrong Alkyl groups, however, can be written in several different ways The following alkyl group arrangements are allowed as correct.

CHM1 Atomic Structure, Bonding and Periodicity

CHM1 Atomic Structure, Bonding and Periodicity GCE 2005 January Series abc Mark Scheme Chemistry CM Atomic Structure, Bonding and Periodicity Mark schemes are prepared by the Principal Examiner and considered, together with the relevant questions,