8 (c) (i) H 2 /Ni or H 2 /Pt or Sn/HCl or Fe/HCl (conc or dil or neither) allow dil H 2 SO 4 ignore mention of NaOH

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1 Polymers Answers

2 EM4 - AQA GE hemistry Mark Scheme 200 January series 8 (c) (i) 2 /i or 2 /Pt or Sn/l or e/l (conc or dil or neither) allow dil 2 S 4 ignore mention of a ot ab 4 ot LiAl 4 ot a/ 2 5 not conc 2 S 4 or any [] r 6 2 allow 6 4 ( 2 ) 2 etc, allow 2 2 i.e. be lenient on structures, the mark is for balancing equ 8 (c) (ii) allow - ignore [ ] n as in polymer st mark for correct peptide link 2 nd mark for the rest correct including trailing bonds 8 (c) (iii) M Kevlar is biodegradeable but polyalkenes not M2 Kevlar has polar bonds / is a (poly) amide / has peptide link M3 can be hydrolysed/attacked by nucleophiles/acids/bases/enzymes M4 polyalkenes non polar /has non-polar bonds 2 allow Kevlar is more biodegradeable comment on structure of Kevlar comment on structure of polyalkenes but not just strong bonds 4

3 Mark Scheme General ertificate of Education (A-level) hemistry Unit 4: Kinetics, Equilibria and rganic hemistry January 202 Question Marking Guidance Mark omments 8(a)(i) (As a) soap Allow washing, cleaning, degreasing, detergents 8(a)(ii) (Bio)diesel or biofuel or fuel for cars/lorries Allow to make soap 8(a)(iii) (ationic) surfactant /detergent /fabric softener /germicide / shampoos /(hair) conditioners /spermicidal jelly Allow cleaning 8(b)(i) (Poly)ester Terylene R PET Allow polyester 8(b)(ii) (Poly)amide Kevlar R nylons Ignore numbers with nylons Allow polyamide(e) 8(b)(iii) (Independent marks) ydrogen bonding in b(ii) Imfs in (b)(ii) are stronger R bonding stronger than dipole-dipole/van der Waals/ dispersion/london forces in b(i) E = 0 3

4 Mark Scheme General ertificate of Education (A-level) hemistry Unit 4: Kinetics, Equilibria and rganic hemistry June 203 5(c)(i) 3 () a 3 ()a 2 R 3 () 3 () 2 ot ambiguous mol formulae for product - must show a or 2 a or or 2 5(c)(ii) [ ] = K a R p = pk a p = 3.86 Allow more than 2 decimal places but not fewer. 5(c)(iii) M buffer Ignore acidic but penalise alkaline or basic. Any two out of the three marks M2, M3 & M4 M2 Large lactate concentration in buffer R sodium lactate completely ionised M3 added acid reacts with/is removed by lactate ion or A or sodium lactate or salt R equation A A Max 2 Ignore reaction of with Ignore reference to equilibrium unless it is shown. M4 ratio [A]/[A - ] stays almost constant Ignore or p remains constant. 5(d)(i) 3 3 o marks if ester link missing B orrect answer scores 2 R 3 3 orrect ester link allow All rest correct with trailing bonds Ignore n here (compare with 5(d)(iv). Ignore brackets. If or on either or both ends, lose one, ie dimer scores If more than two repeating units, lose 5(d)(ii) (Poly)ester ie allow ester ot terylene. Ignore spaces and brackets in answer.

5 Mark Scheme General ertificate of Education (A-level) hemistry Unit 4: Kinetics, Equilibria and rganic hemistry June 203 5(d)(iii) 3 Allow any cyclic (d)(iv) 2 R Penalise n here (compare with 5(d)(i) Ignore brackets. ot allow Ph for phenyl. 5(d)(v) In landfill, no air or UV, to assist decay R not enough water or moisture (to hydrolyse polyester) Allow landfill has/contains: no or few bacteria / micro-organisms / enzymes compared with compost heap R less oxygen R lower temperature. 2

6 Mark Scheme General ertificate of Education (A-level) hemistry Unit 4: Kinetics, Equilibria and rganic hemistry January 203 Question Marking Guidance Mark omments 4(a)(i) ( 2 ) 4 These four only 4(a)(ii) 3 3 Allow 3 and 3 4(a)(iii) 2-amino-3-hydroxybutanoic acid Do not penalise commas or missing hyphens Ignore in butan--oic acid Penalise other numbers 4(a)(iv) Allow 3 and 3 3 ( 2 ) 4 3 7

7 Mark Scheme General ertificate of Education (A-level) hemistry Unit 4: Kinetics, Equilibria and rganic hemistry January 203 4(b)(i) ondensation Allow polyester 4(b)(ii) propane-,3-diol Must have e Allow,3-propanediol 4(c)(i) Addition ot additional 4(c)(ii) R and and 3 3 for each structure within each pair Allow monomers drawn either way round Allow bond to in 3 4(d) c If wrong, E = 0 - or - bonds too strong 8

8 MARK SEME A-LEVEL EMISTRY EM4 JUE 204 Question Marking Guidance Mark omments 4(a) ydrogen bond(ing) Allow bonding. Penalise mention of any other type of bond. 4(b)(i) Ammonia is a nucleophile Allow ammonia has a lone pair. Benzene repels nucleophiles Allow (benzene) attracts/reacts with electrophiles. R benzene repels electron rich species or lone pairs R l bond is short / strong / weakly polar 4(b)(ii) 2 /i R 2 /Pt R Sn/l R e/l Ignore dil/conc of l Ignore the term catalyst. Allow 2 S 4 with Sn and e but not conc. Ignore a following correct answer. ot ab 4 nor LiAl 4 9 of 3

9 MARK SEME A-LEVEL EMISTRY EM4 JUE 204 4(b)(iii) conc 3 conc 2 S S S 4 R using two equations 3 2 S S 4 If either or both conc missed can score for both acids Allow : equation 3 2 S S of 3

10 MARK SEME A-LEVEL EMISTRY EM4 JUE 204 4(b)(iv) Electrophilic substitution Ignore position or absence of l in M but must be in correct position for M2 l R M 2 M l M 2 M3 M M arrow from within hexagon to or on Allow 2 in mechanism. Bond to 2 must be to for structure mark M2 Gap in horseshoe must be centered around correct carbon (). in intermediate not too close to (allow on or below a line from 2 to 6). M3 arrow into hexagon unless Kekule. Allow M3 arrow independent of M2 structure. Ignore base removing in M3 2 2 on in intermediate loses M2 not M3 l l M2 of 3

11 MARK SEME A- LEVEL EMISTRY EM4 JUE 205 Question Marking Guidance Mark omments 7(a)(i) Allow 2 and 2 7(a)(ii) TE Two marks for this clip M for alanine section bonded through M M2 M2 for alanine section bonded through But penalise error in proline ring Allow MAX for correct tripeptide in polymer structure 7(b)(i) 3-methylpent-2-ene Ignore E-Z, commas, spaces or missing hyphens 7(b)(ii) 4-amino-3-methylbutanoic acid Ignore commas, spaces or missing hyphens 3 of 28

12 MARK SEME A- LEVEL EMISTRY EM4 JUE 205 7(b)(iii) or any polyamide section containing 8 carbons plus two = plus two -, such as Trailing bonds are required 7(b)(iv) on polar R no polar groups/bonds (for attack by water / acids / alkalis / nucleophiles or for hydrolysis) - bonds are strong 4 of 28