Acceptable Answers Reject Mark. Acceptable Answers Reject Mark

Transcription

1 (a) n n+ IGNE where n=,, 3 etc or where n is greater than (b)(i) 0 + 0½O 0O + O [O] ALLOW / O ALLOW any correct multiples IGNE state symbols, even if incorrect (b)(ii) Any statement that makes it clear there is not enough air or oxygen e. Limited supply of air / limited supply of oxygen / not enough air / not enough oxygen / lack of oxygen / little amount of oxygen/ small amount of oxygen IGNE it is not completely oxidized

2 (c) First mark Dative pair of e - between S and righthand O () 3 Second mark Two bond pairs between S and lefthand O () Third mark Two lone pairs on left-hand O, one lone pair on central S and three lone pairs on right-hand O atom () If double bonds between sulfur and each oxygen then the third mark can be given for two lone pairs on both oxygens and one lone pair on central S X X X O X S X O X NOTE ALLOW dots and crosses that have been reversed Lone pair electrons can be shown as separated (rather than having to be paired up) it is the total number of electrons in each outer shell that matters Stand alone marks If molecule shown as charged then max

3 (d)(i) benzene ring (d)(ii) Formulae other than molecular formulae ALLOW 6 3 IGNE state symbols, even if incorrect Any other structural or displayed formulae (d) (iii) Any ONE of: (a cyclic alkane) has more efficient combustion allows smoother burning increases octane number Less pollution / reduce waste igh atom economy Produces useful products / hydrogen reduces knocking / less likely to produce pre-ignition is a more efficient fuel burns better / easier to burn /combusts more easily / improves combustion Used to make polymers Produces substances in higher demand / more valuable IGNE (a cyclic alkane): increases the volatility of a fuel ignites more easily is a better fuel burns more cleanly IGNE (a cyclic alkane) has a lower boiling point mentions of viscosity safer fuel

4 (e)(i),-dimethylpentane -dimethylpentane IGNE missing hyphen/missing comma (e)(ii) () () IGNE names even if incorrect IGNE different length bonds IGNE direction of methyl groups (f)(i) U.V. / U.V.light / light / sunlight ALLOW high temperature heat alone (f)(ii) l l + l / l l IGNE any curly arrows, even if incorrect IGNE 4 0 given on both sides

5 (f)(iii) (f)(iv omolytic (fission) IGNE any formulae and arrows Photolysis (fission) / free radical (fission) propagation step) l l () (Second propagation step) l 4 9 l + l () Any reactions involving ydrogen radicals scores zero Reverse of first reaction Formulae can be displayed dots can be anywhere on free radical but no dots at all scores zero ALLOW in either order Incorrect alkane / halogenoalkane but two correct propagation steps scores out of (f)(v) Any ONE of: l 4 9 l l + l l

6 orrect Answer Reject Mark (a)(i) Easier to transport / easier to store / less space / less volume needed for storage / easier to handle / easier to transfer IGNE references to safety Accept Denser/cheaper to transport OWTTE Just cost orrect Answer Reject Mark (a)(ii) skeletal formula () 4 Name: butane () Stand alone skeletal formula () Name: methylpropane -methylpropane () IGNE incorrect punctuation [e.g. extra/missing hyphens, etc.] Stand alone IGNE displayed formulae if also given with skeletal formulae if correct displayed formulae are given max out of for the structures

7 orrect Answer Reject Mark (a)(iii) (Structural) isomers (b)(i) orrect Answer Reject Mark l l + l / l l () (U.V.) light / sunlight () heat alone Must show the dots IGNE any subsequent propagation steps in (b)(i) (b)(ii) orrect Answer Reject Mark l l () l 3 7 l + l () Must show the dots (b)(iii) orrect Answer Reject Mark l 3 7 l l + l l Must show dots in termination step orrect Answer Reject Mark (c)(i) Alkene / triene Accept Diene arbon-carbon double bond

8 orrect Answer Reject Mark (c)(ii) From: Red / brown / orange / yellow or combinations of these colours To: colourless both colours needed clear instead of colourless orrect Answer Reject Mark (c)(iii) Electrophilic () addition () orrect Answer Reject Mark (c)(iv) alculation: 0.0 mol myrcene reacts with 0.03 mol mol myrcene reacts with 3 mol () Structural formula: ( 3 ) ( ) 3 ( 3 ) () Accept Fully displayed formula/skeletal formula Mark calculation and structural formula independently.

9 (d) orrect Answer Reject Mark repeat unit () continuation bonds shown (but these bonds do not have to cut through the brackets) () n not essential IGNE the position of n relative to the repeat unit (e.g. can be written as a superscript)

10 3(a) 6 (g) + 3½O (g) O (g) + 3 O(l) Formulae and states () Balancing of correct entities () Multiples 3(b) Notice the first mark is for the equation and there are 3 separate additional marks for the calculation l-l ---l + -l () heck all bonds displayed especially l-l and - alculation marks: () ( )( ) () Incorrect / no sign and / or incorrect units 656 () ( ) 778 () = (kj mol - ) () Fully correct answer to calculation with no working (3) Extra 5x43 and 347 may be included on both sides, giving 3068 and (-)390 Allow other same values(s) missing from both sides Bonds breaking Bonds making () () Incorrect units loses this mark [Bonds breaking - bonds making] to give correct answer with sign ()

11 3 (c)(i) Initiation () Allow homolysis / atomization / homolytic (fission) Free radical substitution alone Ignore any reference to free radical substitution Photolysis UV / (sun)light () Ignore reference to high temperature

12 3 (c)(ii) 3 + l-l 3 l + l l-l 5 l + l Both products correct including dot () Two half headed arrows showing homolytic breaking of l-l bond () alf headed arrow from radical to pair with a l arrow One arrow from chlorine bond clearly to ethyl radical () Arrows must be single-headed The two dots in the covalent bond do not have to be shown

13 3 (c)(iii) l + l l () / 4 0 () l 3 l () Penalise missing dots once Allow 5 for 3 Di and tri substitution steps 3 (d) Allow (e) Any two from: (It) produces (more) petrol / gasoline / diesel / jet fuel / LPG / liquid petroleum gas / fuel () Short chain alkanes / lighter fractions are more useful products () Points based on atom economy / renewable fuels alone Easier to transport / store Demand is greater for shorter chain alkanes / lighter fractions / smaller molecules converts surplus of low demand fractions () It produces ethane / short chain alkenes for making poly(ethene) / ethane-,-diol / ethanol / plastics / polymers () Smaller alkanes give less pollution/burn more efficiently () Recycles waste products () Short chain alkenes / ethene more useful alone Recycles alone As a source of hydrogen () NB examiners need to look carefully at the vowel in the middle of alkane / alkene / ethane / ethene if not clear do not give BOD

14 4(a)(i) 4(a)(ii) l 3 + l 3 + l 3 l + l 3 + l 3 l + l l 3 + l N.B. different answers for (i) and (ii) needed 4(a)(iii) l 3 l l + l l 4(a)(iv) 3 + l 3 l N.B. different answers for (iii) and (iv) needed

15 4(b) First mark: Structural formula (enough to see the structure) of any polyhalogenated ethane derivative any polyhalogenated methane derivative Butane / 4 0 / 3 3 / chlorobutane / hexane / chloromethane ALLOW correct displayed or skeletal formula () Second mark: If first mark awarded the name must be consequentially correct IGNE any missing or incorrect numbering in name (e.g. dichloroethane scores the mark) IGNE missing or incorrect hyphens If first mark NOT awarded then only ALLOW correct name of any polyhalogenated ethane or polyhalogenated methane derivative ()

16 4(c)(i) st mark for AZARD: This mark is for the idea of: (substance or procedure that) can cause harm/may cause harm/has the potential to do harm/can be dangerous Just causes harm /just is a danger ALLOW references to specific hazards such as toxic/flammable /harmful/ irritant /corrosive /oxidizing/ carcinogenic for the mark () nd mark for RISK: This mark is for the idea of likelihood/probability/chance that harm will result (from the use of a substance or a procedure) () 4(c)(ii) fume cupboard gloves u.v. goggles Just open windows /Just well-ventilated lab/just gas mask /Just use of smaller quantities /close d system/closed experiment