Allow CONH- or - COHN - 1(a)(i) Mark two halves separately

Transcription

1 ERRY ILL TUITIN AQA EMISTRY A2 PAPER 27 MARK SEME Question Marking Guidance (a)(i) 2 2 N N 2 Mark Allow N- or - N - N 6 Mark two halves separately 2 N 6 omments lose each for missing trailing bonds at one or both ends or error in peptide link or either or both of or on ends Not allow (62) Ignore n (a)(ii) M in polyamides - bonding M2 in polyalkenes - van der Waals forces M3 Stronger forces (of attraction) in polyamides r bonding is stronger (must be a comparison of correct forces to score M3) Penalise forces between atoms or van der Waals bonds Do not award if refer to stronger bonds

2 ERRY ILL TUITIN AQA EMISTRY A2 PAPER 27 MARK SEME (b)(i) (nucleophilic) addition elimination M2 Minus sign on N2 loses M 4 M2 not allowed independent of M, but allow M for correct attack on + + rather than + on = loses M2 M3 ( l 3 (3)-N2 N l 32 If l lost with = breaking, max for M N 3 M3 for correct structure with charges but lp on is part of M4 only allow M4 after correct/ very close M3 For M4, ignore N3 removing + but lose M4 for l removing + in mechanism, M M4 for 3 arrows and lp Not allow N 2 (b)(ii) N-methylpropanamide (c) 2S 2N (d)(i) but ignore l as a product 3 N Not N-methylpropaneamide Allow N- or - N - 2-amino-3-hydroxypropanoic acid 2 2

3 ERRY ILL TUITIN AQA EMISTRY A2 PAPER 27 MARK SEME (d)(ii) 2 or N 2 N 2 2 allow 2 or 2 allow N2 N 2 Must be salts of aspartic acid (d)(iii) allow 2 Penalise use of aspartic acid once in d(iii) and d(iv) 2 N 3 (d)(iv) allow 2 2 don t penalize position of + on N3 (l ) Penalise use of aspartic acid once in d(iii) and d(iv) allow +N3 must show -N bond don t penalize position of + on N(3)3 N( 3)3 (Br ) 3 3

4 ERRY ILL TUITIN AQA EMISTRY A2 PAPER 27 MARK SEME Question 2(a) Marking Guidance Benzene-,2-dicarboxylic acid 2(b) 2(c)(i) Mark l 2(c)(iii) Allow,2-benzenedicarboxylic acid Must show all bonds including trailing bonds Ignore n (c)(ii) omments 6 or six NB Two ethanols but only one water 2 3 Ignore overlap with to the left or to the right, but must only include this one carbon. either or allow both (as they are identical)

5 ERRY ILL TUITIN AQA EMISTRY A2 PAPER 27 MARK SEME 2(d) 2 3 LS 2 3 R 2(e)(i) Rate = k[dep] 2(e)(ii) Any two of [244]+ Allow + on or in [DEP] [093]+ + [25]. Dot must be on in radical RS Must have brackets but can be ( ) 2 Max experiment repeated/continued over a long period Not just repetition repeated by independent body/other scientists/avoiding bias investigate breakdown products Ignore animal testing results made public 5 5

6 ERRY ILL TUITIN AQA EMISTRY A2 PAPER 27 MARK SEME Question 3(a)(i) Marking Guidance Single reagent Mark omments If wrong single reagent, E = zero Incomplete single reagent (e.g. carbonate) or wrong formula (e.g.na3) loses reagent mark, but mark on For no reaction allow nothing Different reagents E ester F acid If different tests on E and F; both reagents and any follow on chemistry must be correct for first (reagent) mark. Reagent must react: i.e. not allow Tollens on G (ketone) no reaction. Second and third marks are for correct observations. i.e. for different tests on E and F, if one reagent is correct and one wrong, can score max for correct observation with correct reagent. Na23/Na3 named carbonate metal e.g.mg no reaction no reaction named indicator Pl5 Pl3 Sl2 No reaction no effect Effervescence or 2 Effervescence or 2 acid colour 6 fumes 6

7 ERRY ILL TUITIN AQA EMISTRY A2 PAPER 27 MARK SEME 3(a)(ii) Single reagent If wrong single reagent, E = zero Incomplete single reagent (e.g. carbonate) or wrong formula (e.g.na3) loses reagent mark, but mark on For no reaction allow nothing If different tests on E and F; both reagents and any follow on chemistry must be correct for first (reagent) mark. Reagent must react: i.e. not allow Tollens on G (ketone) no reaction. Different Second and third marks are for correct observations. reagents i.e. for different tests on E and F, if one reagent is correct and one wrong, can score max for correct observation with correct reagent. AgN3 Na23/Na3 named carbonate water named indicator G ketone no reaction no reaction no reaction no effect Acyl chloride (white) ppt Effervescence or 2 or fumes or exothermic fumes acid colour Named alcohol Named amine or ammonia no reaction no reaction Smell or fumes fumes Allow iodoform test or Brady s reagent (2,4,dnph) test (both positive for G) 7 7

8 ERRY ILL TUITIN AQA EMISTRY A2 PAPER 27 MARK SEME 3(a)(iii) Single reagent If wrong single reagent, E = zero Incomplete single reagent (e.g. carbonate) or wrong formula (e.g.na3) loses reagent mark, but mark on For no reaction allow nothing Different reagents If different tests on E and F; both reagents and any follow on chemistry must be correct for first (reagent) mark. Reagent must react: i.e. not allow Tollens on G (ketone) no reaction. Second and third marks are for correct observations. i.e. for different tests on E and F, if one reagent is correct and one wrong, can score max for correct observation with correct reagent. K2r27/ KMn4/ Lucas test (Znl2/l) goes green decolourised / goes brown No cloudiness no reaction no reaction Rapid cloudiness + J Primary alcohol K Tertiary alcohol + Penalise missing + but mark on If uses subsequent tests e.g. Tollens/Fehlings, test must be on product of oxidation 8 8

9 ERRY ILL TUITIN AQA EMISTRY A2 PAPER 27 MARK SEME 3(b)(i) 3(b)(ii) 3,3-dimethylbutan--ol 4 Triplet or three 2-methylpentan-2-ol 5 Singlet or one or no splitting 9 Allow 3,3-dimethyl--butanol Allow 2-methyl-2-pentanol 9

10 ERRY ILL TUITIN AQA EMISTRY A2 PAPER 27 MARK SEME Question 4(a) Marking Guidance Mark M Benzene is more stable than cyclohexatriene omments more stable than cyclohexatriene must be stated or implied If benzene more stable than cyclohexene, then penalise M but mark on If benzene less stable: can score M2 only M2 Expected o hydrogenation of 66 is 3( 20) Allow in words e.g. expected o hydrog is three times the o hydrog of cyclohexene Ignore energy needed = 360 kj mol- M3 Actual o hydrogenation of benzene is 52 kj mol- (less exothermic) or 52 kj mol- different from expected M4 Because of delocalisation or electrons spread out or resonance 0 0

11 ERRY ILL TUITIN AQA EMISTRY A2 PAPER 27 MARK SEME 4(b) No mark for name of mechanism onc N3 If either or both conc missing, allow one; onc 2S4 this one mark can be gained in equation Allow + anywhere on N2+ 3 M arrow from within hexagon to N or + on N 2 2S4 + N3 2 S4 + N R 2S4 + N3 S4 + N R via two equations 2S4 + N3 S4 + 2N3+ 2N3+ N M M3 N 2 Allow N2+ in mechanism horseshoe must not extend beyond 2 to 6 but can be smaller N 2 + not too close to M2 M3 arrow into hexagon unless Kekule R M allow M3 arrow independent of M2 structure ignore base removing in M3 N 2 + on in intermediate loses M2 not M3 M3 + N 2 M2

12 ERRY ILL TUITIN AQA EMISTRY A2 PAPER 27 MARK SEME 4(c) If intermediate compound V is wrong or not shown, max 4 for 8(c) Br or l M or chlorocyclohexane or bromocyclohexane Reaction 3 M2 Br M3 Electrophilic addition Reaction 4 4(d) Allow M2 and M3 independent of each other Allow M4 and M6 independent of each other M4 Ammonia if wrong do not gain M5 M5 Excess ammonia or sealed in a tube or under pressure M6 Nucleophilic substitution If E e.g. acid conditions, lose M4 and M5 Lone or electron pair on N Delocalised or spread into ring in U Less available (to accept protons) or less able to donate (to +) No marks if reference to lone pair on N missing, Question 5: N/A UMS conversion calculator 2 2

13 ERRY ILL TUITIN AQA EMISTRY A2 PAPER 27 MARK SEME Question 6(a) 6(b)(i) Marking Guidance alcohols 6(b)(ii) Ignore any group on RS n LS, penalise or or 2 or 3 Ignore all groups on RS.2 3 Must clearly indicate relevant two on a next to = Ignore missing trailing bonds or attached R groups Must clearly indicate relevant three on next to = Ignore missing trailing bonds or attached R group 6(b)(iii) omments Mark 3 r in words: two equivalent 3 groups Must clearly indicate two equivalent methyl groups. Ignore missing trailing bonds or attached R groups Penalise attached 3 6(b)(iv)

14 ERRY ILL TUITIN AQA EMISTRY A2 PAPER 27 MARK SEME Question 7(a) Marking Guidance Mark eating speeds up (hydrolysis / breaking of peptide bonds) omments R forms non-sweet (amino acids) 7(b) (2-)aminobutanedioic acid R (2-)aminobutane(-,4-)dioic acid 7(c),4 not necessary but penalise other numbers and,4 must be in correct place (QoL) 2N 2 not necessary but penalise other numbers at start allow 2 allow N2 2 7(d) N3 2 allow +N3 don t penalize position of + on N3 7(e)(i) ompounds/molecules with same structural formula But with bonds/atoms/groups arranged differently in space or in 3D 7(e)(ii) allow 2 M Independent marks M2 (Plane) polarised light Rotated in opposite directions Not just structure Allow -with different spatial arrangement of atom/bond/group Not bent or turned or twisted; not different directions (QoL) 4

15 ERRY ILL TUITIN AQA EMISTRY A2 PAPER 27 MARK SEME 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 (Poly)amide Kevlar R nylons 8(b)(ii) 8(b)(iii) (Independent marks) Allow polyester Ignore numbers with nylons Allow polyamide(e) E = 0 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) 5

16 ERRY ILL TUITIN AQA EMISTRY A2 PAPER 27 MARK SEME Question 9(a)(i) Marking Guidance Mark omments onc N3 If either or both conc missing, allow one; onc 2S4 this one mark can be gained in equation` 2 2S4 + N3 2 S4 + N R 2S4 + N3 S4 + N R via two equations Allow + anywhere on N2+ 2S4 + N3 S4 + 2N3+ 2N3+ N (a)(ii) M 3 M3 N2 3 3 M2 R M N2 5 M arrow from within hexagon to N or + on N Allow N2+ in mechanism Bond to N2 must be to N horseshoe must not extend beyond 2 to 6 but can be smaller + not too close to M3 arrow into hexagon unless Kekule allow M3 arrow independent of M2 structure ignore base removing in M3 + on in intermediate loses M2 not M3 M3 + 9(b) ignore position or absence of methyl group in M but must be in correct position for M2 N2 3 N2 3 M2 6

17 ERRY ILL TUITIN AQA EMISTRY A2 PAPER 27 MARK SEME 9(c) 2 9(d) 275N N r halved 7