Download OCR Chemistry A Question number Answer Marks Guidance 1 a

13 Alkenes
Exam-style mark scheme
OCR Chemistry A
Question
number
1a
Answer
Marks
Guidance
Reaction 1 product
B1
Structures must be skeletal.
Reaction 2 product:
B1
1b
steam and a (phosphoric) acid catalyst
B1
Allow water if temperature over
100 ˚C also stated.
1c
cyclopentanol
B1
Ignore numbers.
1d
orange / brown to colourless
B1
Ignore clear.
Not red.
1e
Only one product made (in each reaction).
B1
Correct structure of product. Must have linking bonds
either side.
M1
Rest of equation correct, including use of n and
brackets.
A1
Allow no waste products made.
2a
2bi
2 b ii
B1
Soluble polymer has alcohol / OH groups, which can
form
B1
Not hydroxide.
B1
ORA
hydrogen bonds with water molecules.
3a
(Advantage) generates lots of heat which can (turn
water to steam which will turn turbines to generate
electricity OR not disposing of them in landfill.
B1
(Disadvantage) still using up finite resources of oil to
make more polymers OR toxic gases produced when
polymers are combusted.
B1
3b
hydrogen chloride
B1
3c
photodegradable
M1
(UV) light (can break the bonds)
A1
(Carbon neutral as) amount of carbon dioxide released
when the polymer degrades is equal to the amount of
carbon dioxide taken in by the plant (through
photosynthesis).
B1
3d
Allow hydrochloric acid.
B1
(Not carbon neutral as) harvesting crop / manufacturing
and transport of crop / polymer likely to use fossil fuels
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www.oxfordsecondary.co.uk/acknowledgements
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13 Alkenes
Exam-style mark scheme
OCR Chemistry A
Question
number
Answer
Marks
Guidance
(so more carbon dioxide emitted than absorbed).
4a
2-methylbut-2-ene
B1
4b
electrophilic
M1
addition
A1
Curly arrow from double bond to the H of H–Cl
B1
Curly arrow from H–Cl bond to the Cl AND correct
partial charges shown on the HCl
B1
Positive charge on the correct carbon atom of the
carbocation
M1
Curly arrow from a lone pair of electrons OR the
negative charge on the chloride ion to the positive
carbon.
C1
4d
A tertiary carbocation is more stable than a secondary
carbocation.
B1
4e
2-chloro-3-methylbutane
C1
4c
ECF this mark if incorrect
carbocation drawn.
Allow 3-chloro-2-methylbutane.
Allow ECF for 2-chloro-2-methyl
if curly arrow mechanism
produces minor product in part
c.
4f
Heterolytic
M1
(Double headed) curly arrow shows the movement of a
pair of electrons, so bond breaks when both electrons
move to one of the bonded atoms.
A1
Mark for showing overlap of two p-orbitals on the
carbon atoms.
B1
Mark for π-bond shown above and below the C–C
bond.
B1
5bi
trigonal planar
B1
5 b ii
Each carbon atom is surrounded by three bonds /
areas of electron density which repel equally.
B1
5c
(cannot exhibit E/Z because) each carbon of the CC
double bond does not have 2 different groups attached
to it.
B1
5a
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This resource sheet may have been changed from the original
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13 Alkenes
Exam-style mark scheme
OCR Chemistry A
Question
number
Answer
5di
5 d ii
Any 2 from:
Marks
Guidance
B1
Must be skeletal.
B1
Structures can be the E or Z
version and can be displayed or
skeletal or a mixture, as long as
they are unambiguous.
B1
Do not allow any structures
which do not exhibit E/Z
isomers, e.g. hex-1-ene,
2,3-dimethylbut-2-ene or
2-methylpent-2-ene.
5ei
E, because the highest priority groups are opposite
each other (across the CC double bond).
Cl has a higher atomic number than C AND F has a
higher atomic number than H.
5 e ii
(In order to have cis or trans isomers) each C atom of
the CC double bond must have two different
substituent groups and one of those groups must be
hydrogen.
© Oxford University Press 2015
M1
Not just E.
A1
B1
Allow AW.
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This resource sheet may have been changed from the original
3