4 ALLOW sugar from equation

Transcription

1 Question Expected Answers Marks Additional Guidance 1 (a) method 1: fermentation of sugars or carbohydrates R reaction with yeast with sugar or carbohydrates ALLW sugar from equation ALLW 2 6 in equation ALLW correct multiples IGNRE state symbols method 2: hydration of ethene R reaction of ethene with water R reaction of steam with ethene ALLW ethene from the equation IGNRE mention of any catalyst ALLW 2 6 in equation R 2 over the arrow ALLW correct multiples IGNRE state symbols (b) (i) ( 3 ) 2 R If name and formula given both need to be correct ALLW propanone R acetone IGNRE propone NT incorrect named compound ( 3 ) 2 + [] ( 3 ) ALLW [] ALLW instead of [] ALLW correct multiples IGNRE state symbols (ii) 3 2 R propanoic acid 3 Any number or range of numbers between (cm 1 ) for = ALLW = and marks independent of compound identified i.e. stand alone marks ALLW correct bonds shown by the appropriate Any number or range of numbers between (cm 1 ) for absorption on the IR spectrum IGNRE reference to bond (c) (i) 2-methylpropan-2-ol 1 ALLW methylpropan-2-ol R tertiarybutanol

2 Question Expected Answers Marks Additional Guidance (ii) ester 1 (iii) 3 2 ( 3 ) 3 R 3 ( 3 ) 3 2 ALLW skeletal formula R displayed formula R 3 ( 3 ) 3 ester group shown ALLW ester linkage even if rest of structure is wrong rest of molecule Total 13

3 Question Expected Answers Marks Additional Guidance 2 (a) Structural isomer 11 compounds with the same molecular formula but with different structural formulae ALLW same molecular formula but different structures Second marking point is DEPENDENT on first mark Stereoisomer compounds with the same structural formula but with different arrangements in space Evidence of using M r of 70 to calculate molecular formula of 5 10 F and G are o orrect identification of the E and Z isomers is ALLW compounds with the same structure Second marking point is DEPENDENT on first mark This is the QW mark IGNRE wrong names of F, G and ALLW structural or displayed formulae for F, G and e.g. is ALLW identification using trans and cis and ALLW this marking point as identification of another example of identifying E/Z or cis and trans if not done for F and G ALLW one mark if no structures drawn but correct names given for F, G and i.e E-pent-2-ene, Z-pent-2- ene and pent-1-ene ALLW ecf on structures if wrong molecular formula used or consistent error or slip such as having just sticks E/Z happens because double bonds restricts rotation different groups on each carbon of the double bond

4 Question Expected Answers Marks Additional Guidance (b) from IR absorption, J contains R from IR J is an alcohol : : = : : R : : This is a QW mark empirical formula = 6 14 (from mass spectrum), M r = 102 evidence that it has been shown that the empirical formula is the molecular formulae e.g. M r of 6 14 = 102 so empirical formula is molecular formula ALLW two marks for correct empirical formula with no working out This is a QW mark ALLW structural or displayed formulae IGNRE incorrect names ALLW one minor slip in drawing structures e.g. one missing hydrogen but ALLW ecf for bigger slips such as showing just sticks and no hydrogen atoms ALLW bond to in ne mark for each correct structure Total 19 ALLW one mark for three isomers of 6 13 whether branched or unbranched as a catch mark if no other mark has been awarded for the structures If more than three isomers of 6 13 drawn 1 branched and 3 unbranched award two marks any other combination award one mark ALLW one mark for hexan-1-ol, hexan-2-ol and hexan- 3-ol if structures not drawn

5 Question er Marks Guidance 3 (a) Any three from: 3 Assume it refers to Process 1 Process 1 has a high atom economy R has 100% atom economy R a greater atom economy R makes only the desired product ALLW process 1 has no waste R process 1 has no coproducts R process 1 needs less separation R process 1 has fewer other products R gives only one product ALLW RA if process 2 is specified Process 1 has a very efficient conversion of reactants to products R not much waste of starting material ALLW RA if process 2 is specified high percentage yield is not sufficient D NT ALLW if percentage yield is explicitly linked to more waste (products) e.g. process 1 has a high percentage yield so makes little waste (product) scores 0 marks but process 1 makes no waste (product) and it has a high percentage yield scores 1 mark Process 1 uses a lower pressure ALLW RA if process 2 is specified Process 1 uses up toxic carbon monoxide Process 1 uses methanol which can be produced from biomass IGNRE process 2 comes from crude oil a non-renewable source ALLW process 1 starts from a renewable source if the source is specified e.g. wood, municipal waste or sewage IGNRE reference to catalyst and rate of reaction

6 Question er Marks Guidance (b) ( 5 ANNTATE ANSWER WIT TIKS AND RSSES ET ontains = bond because of absorption between 1700 and 1740 cm 1 (from the spectrum) ALLW contains a carbonyl group because of absorption within range cm 1 R contains an aldehyde, ketone or carboxylic acid because of absorption within range cm 1 Mention of only an aldehyde or a ketone is not sufficient it needs reference to the wavenumber LK FR TIS MARK N TE SPETRUM does not contain an bond ALLW not a carboxylic acid ALLW does not have any other characteristic absorbance due to other functional groups (So was a) ketone R aldehyde ALLW (so was a) carbonyl compound ALLW this mark if a structure of an aldehyde or a ketone is given even if the structure has an incorrect number of carbon atoms M r = 86 orrect structure ALLW correct structural R displayed R skeletal formula R mixture of the above (as long as unambiguous) LK FR AN ALDEYDE or KETNE with FIVE carbon atoms R a DIALDEYDE, DINE R an XALDEYDE with FUR carbon atoms a comprehensive list of correct structures is shown on page 34 IGNRE incorrect name D NT ALLW for an aldehyde

7 Question er Marks Guidance ALLW as a slip one stick with no on in a displayed formula R pentanal 3 2-methylbutanal R pentan-3-one

8 Question er Marks Guidance (b) (i orrect structure 2 ALLW correct structural R displayed R skeletal formula R mixture of the above (as long as unambiguous) All bonds and all hydrogen atoms must be shown in a displayed formula within this question Name of the structure drawn Name must correspond to the correct structure for two marks ALLW butanoic acid or 2-methylpropanoic acid if the structure drawn is incorrect There is no EF in this question ALLW R butanoic acid 3 ALLW ( 3 ) 2 2-methylpropanoic acid ALLW methylpropanoic acid

9 Question er Marks Guidance (c) Use of propan-1-ol 4 ALLW correct structural R displayed R skeletal formula R mixture of the above (as long as unambiguous) ALLW from the equation propanol R 3 7 is not sufficient orrect formulae for the ester orrectly balanced equation ALLW molecular formula R correct structural R displayed R skeletal formula R mixture of the above ALLW propan-2-ol in the equation Add 2 S 4 R acid catalyst R + ALLW conditions mark over the arrow in the equation Total 14

10 Question er Marks Guidance 4 (a) Shape tetrahedral 2 Bond angle o (b) ( Volatile R non-toxic R non-flammable R easily vaporised ALLW o 1 ALLW not carcinogenic / not an irritant / not harmful / not hazardous IGNRE cheap / not dangerous / gas / low boiling point D NT ALLW inflammable (ii) ( F or l ) bonds need a large amount of energy to break 1 ALLW (the F or l) bonds are strong / bonds have a large bond enthalpy ALLW the molecule is not polar enough / non-polar molecule is not sufficient ALLW the activation energy is too high D NT ALLW dissolves IGNRE references to hydrogen bonding (c) F 2 l 2 F 2 l + l 3 ALLW F 2 l 2 (breaks down to) produces chlorine atoms/radicals ALLW equation with any F AND ANY TW FRM l catalyses the decomposition of ozone l + 3 l + 2 l + l + 2 ALLW l + 3 l ALLW R for one mark if the two equations for the steps have not been given IGNRE other propagation equations

11 Question Answer Marks Guidance (d) Because (more) UV will reach the Earth s surface and risk of (skin) cancer increased/risk of cataracts/crop mutation increased 1 D NT ALLW global warming ALLW protects from UV which causes skin cancer etc (e) Ideas related to uses Fs are still entering the atmosphere (from disused items) R Fs are still used (for some purposes and by some countries) Ideas relating to lifetime within the atmosphere Fs have a long lifetime in the atmosphere R it takes a long time for Fs to reach upper atmosphere R Fs are inert 2 ALLW 'stratosphere' for 'upper atmosphere' ALLW Fs are still entering the ozone layer Total 10

12 Question Expected Answers Marks Additional Guidance 5 (a) (i) 2-Methylpropan-2-ol 1 ALLW methylpropan-2-ol (b) 1 Formula must be skeletal AND not include any symbol except for (c) (i) Same molecular formula but different structural formulae 1 ALLW Same molecular formula but different arrangement of atoms R Same molecular formula but different structures R Same molecular formula but different displayed formulae D NT ALLW Same molecular formula but different spatial arrangement of atoms (ii) R ( 3 ) ALLW displayed formula ALLW ALLW sticks (i.e. no shown bonded to ) R ALLW D NT ALLW shown as below sticks K and is K sticks K but is not K ALLW correct ethers

13 Question Expected Answers Marks Additional Guidance (d) as (bonds) R has hydroxyl (groups) R has hydroxy (groups) 2 ALLW marks from a diagram of hydrogen bonding IGNRE reference to alcohol functional group Forms hydrogen bonds with water (molecules) (e) mark for each ester end of molecule D NT ALLW forms hydrogen bonds 2 ALLW displayed formula R skeletal formula ALLW sticks shows one of the two ester groups and scores one mark (f) (i) D NT ALLW i.e. no E 3 (ii) E/Z 1 ALLW cis-trans IGNRE geometric (iii) 3 2 = 2 R but-1-ene 1 If but-1-ene given in part (i), ALLW but-2-ene R 3 = 3 i.e. EF from f(i) D NT ALLW methylpropene: 3 3

14 Question Expected Answers Marks Additional Guidance From the evidence, candidates may have identified compound F as propanone, propanal or propanoic acid The mark scheme for F = propanone and propanal is shown in the Expected Answers column. The mark scheme for F = propanoic acid is shown in the Additional Guidance column. If F is propanone or propanoic acid, then maximum score = 7; but if F is propanal then maximum score = 6 (g) Mark scheme for F = propanone and propanal 7 Mark scheme for F = propanoic acid mass spec of E Remember to check the spectrum Quality of Written ommunication mass spec gives M + or molecular ion of 60 R mass spec gives parent ion of 60 R highest m/z (ALLW m/e) value is 60 mass spec of E Remember to check the spectrum QW mass spec gives M + or molecular ion of 60 R mass spec gives parent ion of 60 R highest m/z (R m/e) value is 60 m/z = 45 indicates loss of 3 R m/z = 45 indicates presence of 3 R 2 2 R 2 5 IR of F Remember to check the spectrum IR shows no broad absorption between 2500 to 3300 cm 1 so no bond R no broad absorption between 2500 to 3300 cm 1 so not a carboxylic acid IR shows absorption at 1700 cm 1 due to a = bond R absorption at 1700 cm 1 indicates a ketone R aldehyde present Identification and equation F is 3 3 R propanone E is 3 3 R propan-2-ol [] If F has been incorrectly identified as propanal, mark identification and equation as EF, so max = 2 ALLW E is m/z = 45 indicates loss of 3 R m/z = 45 indicates presence of 3 R 2 2 R 2 5 IR of F Remember to check the spectrum IR shows (broad) absorption somewhere between 3500 and 2500 cm 1 suggests carboxylic acid R bond IR shows absorption at 1700 cm 1 due to = R absorption at 1700 cm 1 indicates a carboxylic acid Identification and equation F is 3 2 R propanoic acid E is R propan-1-ol [] ALLW: [] Total 19