PMT

Mark Scheme FINAL

Summer 2019

Pearson Edexcel International GCSE in

Chemistry (4CH1)
Paper 2C
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Summer 2019
Publications Code 4CH1_2C_msc_20190822
All the material in this publication is copyright
© Pearson Education Ltd 2019
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General Marking Guidance

 All candidates must receive the same treatment.

Examiners must mark the first candidate in exactly the
same way as they mark the last.
 Mark schemes should be applied positively. Candidates
must be rewarded for what they have shown they can
do rather than penalised for omissions.
 Examiners should mark according to the mark scheme
not according to their perception of where the grade
boundaries may lie.
 There is no ceiling on achievement. All marks on the
mark scheme should be used appropriately.
 All the marks on the mark scheme are designed to be
awarded. Examiners should always award full marks if
deserved, i.e. if the answer matches the mark scheme.
Examiners should also be prepared to award zero
marks if the candidate’s response is not worthy of
credit according to the mark scheme.
 Where some judgement is required, mark schemes will
provide the principles by which marks will be awarded
and exemplification may be limited.
 When examiners are in doubt regarding the
application of the mark scheme to a candidate’s
response, the team leader must be consulted.
 Crossed out work should be marked UNLESS the
candidate has replaced it with an alternative response.
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Question
Answer Additional guidance Marks
number
1 (a)
1 mark for each correct 3
answer

(b) 13 1

(c) M1 protons IGNORE electrons 2

M2 neutrons

Total 6
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Question
Answer Additional guidance Marks
number
2 (a)
2

ALLOW black
ALLOW any combination of
grey and black eg grey-black

(b) M1 (35 × 77.78) + (37 × 22.22) 3

OR 3544.44

M2 3544.44 ÷ 100 OR 35.4444 OR M1 ÷ 100 (35 × 0.7778) + (37

× 0.2222)
OR
35.4444/35.444/35.44 with
no working scores 2

M3 35.4 35.4 with no working scores

3

M3 can be ECF from an

incorrect M2
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(c) An explanation that links together the following four points:

M1 add chlorine (solution) to potassium bromide ACCEPT mix the two 4

(solution) solutions

M2 (solution) turns orange ALLOW any combination of

orange/yellow/brown
IGNORE other observations
eg bubbles

M3 bromine/Br2 is displaced ALLOW bromine/Br2 is

produced/formed

IGNORE state of bromine

REJECT bromide
IGNORE a displacement
reaction occurs
M3 can be scored by Br2 as
a product in an equation

M4 (therefore) chlorine is more reactive (than bromine) ACCEPT reverse argument

“If a reaction occurs then

chlorine is more reactive
than bromine” scores M4
Total 9
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Question number Answer Additional guidance Marks

3 (a) M1 the volume of liquid/alcohol ALLOW amount of liquid/alcohol 2
IGNORE mass
IGNORE volume of water

M2 the temperature of the water ALLOW temperature of surroundings

IGNORE references to temperature of

the alcohol

(b) alcohols/the liquids are flammable/catch fire ALLOW alcohols/the liquids can be 1
easily easily ignited
ALLOW any named alcohol from the
table
(c)
(i) M1 (64 + 63 + 60) ÷3 2

M2 = 62
ALLOW 62.3

62/62.3 with no working scores 2

ALLOW 69/69.25/69.3 for 1 mark

(ii) An explanation including the following two

points:

M1 methanol/CH3OH (evaporates most easily) 2

M2 because the time taken is the shortest ACCEPT because has lowest (mean)
time
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Question Answer Additional Guidance Marks

Number
(iii) M1 as the number of carbon atoms increases 2

M2 the ease of evaporation decreases/the less ALLOW the less volatile the alcohol
easily the alcohol evaporates
IGNORE the slower the alcohol
evaporates
IGNORE references to time taken

ALLOW correct reverse argument

Total 9
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Question
number Answer Additional guidance Marks

4 (a) C (electrostatic attraction between positively charged 1

particles and delocalised electrons) is correct as it
describes metallic bonding
A is incorrect since it describes ionic bonding not metallic
bonding
B is incorrect since it describes covalent bonding not
metallic bonding
D is incorrect since it describes interatomic or
intermolecular forces not metallic bonding

(b) Any two from the following:

M1 good conductor of heat/thermal energy 2

M2 does not react with food/affect flavour of food IGNORE non-toxic

M3 resistant to corrosion ALLOW does not corrode/rust

IGNORE unreactive/inert

M4 high melting point IGNORE references to recycling

M5 low density/lightweight/strong IGNORE light

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Question
Answer Additional guidance Marks
number
4 (c) (i) a mixture of (two or more) elements, one of which is ACCEPT a mixture of (two or 1
a metal more) metals
ALLOW combination for mixture
REJECT compound or references to
chemical bonding

(ii) An explanation that links together the following three

points:

M1 the regular arrangement of atoms is ALLOW lattice/layers/rows of 3

distorted/disrupted OWTTE atoms are disrupted/distorted
ALLOW lattice/layers/rows of
atoms less regular

M2 because magnesium atoms are larger than ALLOW magnesium and aluminium
aluminium atoms atoms are of different sizes

M3 and therefore it is more difficult for the layers to ALLOW layers cannot (as easily)
slide over one another slide over one another

IGNORE references to strength of

metallic bonds

Total 7
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Question Answer Additional guidance Marks

number
5 (a) (i) (bonds broken) 1

3861 (kJ)

(ii) (bonds made) 1

4649 (kJ)

(iii) M1 subtraction of Σ(bonds made) made and In (iii) ECF from (i) and 3
Σ(bonds broken) (ii) must be applied
Subtraction can be in any
order

M2 correct evaluation of the calculation shown in M1 IGNORE sign

M3 If Σ(bonds made) > Σ(bonds broken) final answer must

be negative
If Σ(bonds made) < Σ(bonds broken) final answer must Expected final answer is
be positive (and + sign given) ‒788 (kJ/mol)

-788 with no working

scores 3
(+) 788 scores 2
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(b) An explanation that links together the following two points:

M1 more energy is given out when the bonds are made If state/imply that energy 2
required to make bonds
OR
If state/imply that energy
released when bonds are
broken scores 0/2

M2 than is taken in when the bonds are broken

ACCEPT correct reverse
argument
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Question
Answer Additional guidance Marks
number
5 (c)
IGNORE horizontal axis 3
drawn

IGNORE enthalpy change

shown

IGNORE activation
energy shown

M1 right hand line below left hand line

M2 correct names/formulae of both reactants If only use words

reactants (on left) and
M3 correct names/formulae of both products products (on right) award
1 mark from M2 and M3

Total 10
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Question
Answer Additional guidance Marks
number
6 (a) (i) yeast IGNORE zymase 1

(ii) C (30 °C) is correct as it is the most 1

suitable temperature for fermentation
A is incorrect as at 0°C the enzymes
would not be active so not the most
suitable temperature for fermentation
B is incorrect as at 10°C the enzymes
would not be very active so not the most
suitable temperature for fermentation
D is incorrect as at 80°C the enzymes
would be denatured so not the most
suitable temperature for fermentation

(iii) An explanation using either of the

following linked pairs:

M1 oxygen in the air would react with ACCEPT ethanol would be oxidised 2
ethanol

M2 to form ethanoic acid ALLOW to form carboxylic acid

ALLOW to form vinegar
OR

M1 the fermentation/reaction/respiration
needs to be anaerobic

M2 ethanol would not be formed /CO2

and H2O would form
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(b) (i) a substance that releases thermal IGNORE energy on its own 1
energy/heat (energy) when
burned/combusted

(ii) C2H5OH + 3 O2  2 CO2 + 3 H2O ACCEPT multiples 2

M1 all formulae correct

M2 correctly balanced M2 DEP M1

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Question
Answer Additional guidance Marks
number
6 (c) M1 (temperature) 300 °C ACCEPT any value or range of values 2
between 250 and 350 °C
If no unit given assume it is Celsius
ACCEPT equivalent temperatures in other
units provided the unit is given

M2 60 ‒ 70 atm ACCEPT any value or range of values

between 60 and 70 atm
If no unit given assume it is atm
ACCEPT equivalent pressures in other units
provided the unit is given

(d) (i) (from) orange (to) green 1

(ii) IGNORE bond angles

2

scores 1 mark

(iii) CH3COONa + ½ H2 ALLOW NaCH3COO 2

M1 for both products correct

M2 for correctly balanced ACCEPT multiples

M2 DEP M1

Total 14
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Question
Answer Additional guidance Marks
number
7 (a) An explanation that links together the following
two points:

M1 reaction is taking place in both directions (at ACCEPT both forward and 2
same time) backward reactions are taking place
(at same time)
IGNORE it is a reversible reaction

M2 at equal rate M2 DEP M1

rate of the forward reaction is equal

to the rate of the backward reaction
scores 2 marks

REJECT both forward and backward

reactions occur at constant rate for
M2

ALLOW the concentrations of the

reactants and products remains
constant scores 1 mark
independently of M1
but
REJECT concentrations of the
reactants and products are
equal/the same
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(b) (i) An explanation that links together the following

two points:

M1 (the position of) equilibrium has ALLOW (position of) equilibrium 2

moved to the left has shifted in backwards direction

ALLOW (position of) equilibrium

has shifted towards the N2O4
/reactants (side)

ALLOW increasing pressure shifts

(position of) equilibrium in direction
that produces fewer moles (of gas)

IGNORE references to Le
Chatelier’s Principle eg increasing
pressure favours the side that has
fewer moles of gas / increasing
pressure favours the backwards
reaction
M2 because there are fewer moles/molecules (of ALLOW particles
gas) on the left REJECT atoms

ALLOW because there are fewer

moles of N2O4 (than NO2)
ALLOW because there are fewer
moles of reactant (than product)

ACCEPT reverse argument

(ii) the concentration of NO2 has increased ALLOW molecules/particles of NO2 1
are closer together
ALLOW molecules/particles of NO2
are in a smaller volume
REJECT more NO2 produced
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Question
Answer Additional guidance Marks
number
7 (c) (i) nitrogen/N2 reacts with oxygen/O2 (both from the IGNORE nitrogen burns/combusts 1
air) in oxygen
IGNORE nitrogen is oxidised

(ii) (they form) acid rain ACCEPT references to respiratory 1

problems
ALLOW a specified harmful effect of
acid rain
ALLOW references to smog
ALLOW references to greenhouse
gases/global warming/climate
change

(iii) 2 NO + 2 CO  N2 + 2 CO2 ACCEPT multiples and fractions 1

Total 8
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Question
Answer Additional guidance Marks
number
8 (a)
An explanation using either of the following
linked pairs:

M1 use a fume cupboard 2

M2 because chlorine is toxic/poisonous IGNORE chlorine is

dangerous/harmful/irritant
OR

M1 wear goggles/safety glasses/gloves

M2 because acid/bleach (may be)

irritant/corrosive
IGNORE laboratory coats

(b) (i) M1 60 ÷ 24 000 2

M2 0.0025 (mol) 0.0025 with no working scores 2 marks

REJECT 0.003 for M2

(ii) 0.0025 OR answer to M2 from (i) 1

(iii) M1 (0.0025 ÷ 4.00) × 1000 Mark CSQ on (b)(ii) 2

M2 0.625 (mol/dm3) ACCEPT any number of sig fig except 1

(unless ECF answer is exactly 1 sig fig

correct answer with no working

throughout (b) scores 2 marks
Total 7
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