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Title: Edexcel as level chemistry question paper 2 june 2024 + mark scheme
Description: Mark Scheme (Results) Summer 2024 Pearson Edexcel GCE In Chemistry (8CH0) Paper 02: Core Organic and Physical Chemistry
Description: Mark Scheme (Results) Summer 2024 Pearson Edexcel GCE In Chemistry (8CH0) Paper 02: Core Organic and Physical Chemistry
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Edexcel as level
chemistry question
paper 2 june 2024 +
mark scheme
Please check the examination details below before entering your candidate information
Candidate surname
Centre Number
Other names
Candidate Number
Pearson Edexcel Level 3 GCE
Tuesday 21 May 2024
Morning (Time: 1 hour 30 minutes)
Chemistry
Paper
reference
8CH0/02
Advanced Subsidiary
PAPER 2: Core Organic and Physical Chemistry
You must have:
Scientific calculator, Data Booklet, ruler
Total Marks
Instructions
Use black ink or ball‑point pen
...
• IfFillpencil
boxes at the top of this page with your name,
• centrein the
number and candidate number
...
• Answer
Answer
the questions in the spaces provided
• – there may
be more space than you need
...
• The
The
for each question are shown in brackets
• – usemarks
this as a guide as to how much time to spend on each question
...
A Periodic Table is printed on the back cover of this paper
...
• Read
all your working in calculations and include units where appropriate
...
P76894A
©2024 Pearson Education Ltd
...
The acid, which can be represented as H2A, was dissolved in
deionised water and the solution made up to 250 cm3
...
100 mol dm–3 sodium hydroxide solution was added to a burette
...
0 cm3 portion of the acid solution
...
What is the initial burette reading for this titration?
(1)
2
...
0
A
2
...
45 cm3
C
3
...
60 cm3
2
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Some questions must be answered with a cross in a box
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Answer ALL questions
...
50 cm3
...
(iii) Describe how you would use the rough titration value when carrying out the
accurate titrations
...
...
...
...
H2A(aq) + 2NaOH(aq) → Na2A(aq) + 2H2O(l)
The acid solution was pipetted into a conical flask and titrated
...
The following results were recorded for the accurate titrations
...
80
24
...
60
Burette reading (initial) / cm3
24
...
00
24
...
30
23
...
25
(i) Calculate the mean titre for these accurate titrations
...
4
*P76894A0432*
(1)
(1)
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(c) 25
...
100 mol dm–3 sodium hydroxide solution
...
54 g
...
You must show your working
...
An equilibrium forms as shown
...
(3)
...
...
...
...
...
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(b) A gas syringe contains a mixture of the gases nitrogen dioxide (NO2) and
dinitrogen tetroxide (N2O4)
...
The mixture is allowed to reach equilibrium at room temperature
...
The mixture is left to stand until equilibrium is reached again
...
(3)
...
...
...
...
...
The contents of the syringe become a darker brown
...
(2)
...
...
...
(Total for Question 2 = 9 marks)
*P76894A0732*
7
Turn over
Structural formula
but‑1‑ene
CH3CH2CH CH2
but‑2‑ene
CH3CH CHCH3
methylpropene
(CH3)2C CH2
(a) Give the molecular formula and empirical formula of but‑1‑ene
...
Empirical formula
...
(i) What is the name and type of the mechanism of this reaction?
A
electrophilic addition
(1)
B
nucleophilic addition
C
electrophilic substitution
D
nucleophilic substitution
8
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Name
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3 But‑1‑ene, but‑2‑ene and methylpropene are three isomeric alkenes
...
Include curly arrows, and any relevant charges, dipoles and lone pairs
...
Justify why this minor product is formed in smaller amounts
...
(3)
...
...
...
(1)
...
*P76894A0932*
9
Turn over
(c) But‑2‑ene exists as two stereoisomers
...
(2)
Isomer 1
Isomer 2
Name
...
(ii) Explain how the presence of the double bond in but‑2‑ene results in these
two isomers
...
...
...
10
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(d) One of the three alkenes can be hydrated to form a tertiary alcohol
...
(2)
...
...
...
(Total for Question 3 = 17 marks)
*P76894A01132*
11
Turn over
(a) Cyclobutane can be made by the dimerisation of ethene
...
Bond
Mean bond enthalpy / kJ mol–1
C H
413
C C
347
C C
612
Calculate the enthalpy change of this dimerisation by selecting appropriate
data from the table
...
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(ii) A different value for the enthalpy change of the reaction can be calculated
using bond enthalpies instead of mean bond enthalpies
...
Explain why the use of bond enthalpies gives a more accurate enthalpy
change value
...
...
...
...
Value / kJ mol–1
Enthalpy change of combustion of cyclobutane
–2721
Enthalpy change of formation of carbon dioxide
–394
Enthalpy change of formation of water
–286
(i) Complete the enthalpy cycle using Hess’s Law
...
ΔfH
...
...
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Enthalpy change
...
(ii) Calculate the enthalpy change of formation of cyclobutane
...
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Procedure
Step 1 In a fume cupboard, 10 g of sodium bromide, 10 cm3 of deionised water and
7
...
Step 2 1
0 cm3 of concentrated sulfuric acid is dripped slowly from a tap funnel into
the reaction mixture in the pear‑shaped flask
...
The flask and condenser are taken out of the ice‑water bath
...
Step 4 T he apparatus is then rearranged for distillation and the distillate of
1‑bromobutane and water is collected in a small beaker, forming two layers
...
Step 6 T he 1‑bromobutane layer is washed with concentrated hydrochloric acid to
remove any unreacted butan‑1‑ol, and then separated
...
Step 8 A drying agent is added to the 1‑bromobutane
...
The 1‑bromobutane is distilled again and collected between 101 °C and 103 °C
...
The ice helps to prevent side reactions
...
(i) Give one reason for the presence of the condenser and one reason for the
still head in Steps 1 and 2
...
...
...
...
(2)
Inorganic product
...
(iv) Give a reason why ice helps to prevent the formation of these redox products
...
...
(b) Describe how the apparatus is rearranged for distillation, including the name of
any additional apparatus required
...
...
...
...
...
18
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(1)
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(c) The method of separation of the aqueous and organic layers in Step 5 is different
from that used in Steps 6 and 7
...
[Density of water = 1
...
28 g cm–3]
(1)
(ii) Describe how the aqueous layer can be removed from the beaker in Step 5
...
...
...
(1)
...
A student carried out an investigation to determine the effect of the concentration of
sodium thiosulfate on the rate of the reaction
...
Step 2 Place the flask on a piece of paper with a black cross marked on it
...
Step 4 L ook down through the solution at the black cross and record the time taken
for the cross to no longer be visible through the solution
...
Step 6 C
hange the concentration of sodium thiosulfate by repeating
Steps 1–5 using different volumes of the sodium thiosulfate solution and
deionised water
...
(1)
...
...
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(b) A student carried out the investigation using five different concentrations of
sodium thiosulfate solution
...
03
0
...
09
0
...
15
Concentration of Na2S2O3 immediately after
adding the acid in Step 3 / mol dm–3
(i) What was the concentration, in mol dm–3, of the original solution of
sodium thiosulfate?
(1)
A
0
...
15
C
0
...
71
(ii) State why water is added in Experiments 1 to 4, but not in Experiment 5
...
...
*P76894A02132*
21
Turn over
(c) The student plotted a graph of 1/ time against concentration of
sodium thiosulfate
...
04
0
...
02
0
...
00
0
...
02
0
...
06
0
...
10
0
...
14
0
...
10 mol dm–3
...
(1)
(1)
...
...
05
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(d) Which will decrease the accuracy of the experiment?
(1)
A
rinsing the flask with deionised water before each new experiment
B
stirring the solution throughout each experiment
C
using a different 50 cm3 measuring cylinder for each solution
D
using the same piece of paper in each experiment
(e) Experiment 1 is repeated at the same temperature, but using a 100 cm3
conical flask in place of the 200 cm3 flask
...
•
increasing temperature at constant pressure
•
increasing pressure at constant temperature
(6)
...
...
...
...
...
...
...
...
...
...
24
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CO2(g) + 3H2(g) CH3OH(g) + H2O(g)
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*7 Methanol can be produced by reacting carbon dioxide and hydrogen in the
exothermic reaction shown
...
...
...
...
...
...
...
...
...
...
...
...
...
(Total for Question 7 = 6 marks)
*P76894A02532*
25
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Diagram
thermometer
beaker
water
spirit burner
methanol
Student’s results
Measurement
Value
Mass of spirit burner and methanol before combustion
152
...
2 g
Mass of water in the beaker
200
...
5 °C
Temperature of water after heating
52
...
18 J g–1 °C–1
Molar mass of methanol = 32
...
Include state symbols
...
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(ii) Calculate the expected final temperature of the water in the student’s
experiment, assuming no experimental errors
...
*P76894A02732*
(4)
(1)
27
Turn over
Explain whether or not the student would have been better to wait for the
balance with greater precision to give a final answer with greater accuracy
...
...
...
...
(Total for Question 8 = 9 marks)
TOTAL FOR PAPER = 80 MARKS
28
*P76894A02832*
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(b) Instead of waiting in a queue for a balance which recorded the mass of the
spirit burner to 2 decimal places, the student used a balance which recorded the
mass to 1 decimal place
...
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Examiners
must mark the first candidate in exactly the same way as they
mark the last
...
Candidates must be
rewarded for what they have shown they can do rather than
penalised for omissions
...
•
There is no ceiling on achievement
...
•
All the marks on the mark scheme are designed to be awarded
...
e
...
Examiners should also be
prepared to award zero marks if the candidate’s response is not
worthy of credit according to the mark scheme
...
•
When examiners are in doubt regarding the application of the
mark scheme to a candidate’s response, the team leader must
be consulted
...
Using the Mark Scheme
Examiners should look for qualities to reward rather than faults to penalise
...
Examiners should therefore read carefully and consider every response: even if it is not what is expected it may be
worthy of credit
...
/ means that the responses are alternatives and either answer should receive full credit
...
Phrases/words in bold indicate that the meaning of the phrase or the actual word is essential to the answer
...
Candidates must make their meaning clear to the examiner to gain the mark
...
Do not give
credit for correct words/phrases which are put together in a meaningless manner
...
Quality of Written Communication
Questions which involve the writing of continuous prose will expect candidates to:
• write legibly, with accurate use of spelling, grammar and punctuation in order to make the meaning clear
• select and use a form and style of writing appropriate to purpose and to complex subject matter
• organise information clearly and coherently, using specialist vocabulary when appropriate
...
Questions where QWC is likely to be particularly important are indicated (QWC) in the mark scheme, but this does not preclude
others
...
45 cm3)
Answer
Mark
(1)
A is not correct because the volume must be measured from the bottom of the meniscus
C is not correct because this is the volume reading from the bottom of the burette, not the top
D is not correct because this is reading from the bottom and not using the bottom of the meniscus
Question
Number
1(b)(ii)
Answer
Additional Guidance
Example of calculation
•
calculation of volume by subtracting the answer to (b)(i)
from 26
...
50 ‒ 2
...
05 (cm3)
Allow TE on incorrect answers to (b)(i)
Mark
(1)
Question
Answer
Number
1(b)(iii)
An answer that makes reference to the following point:
•
Question
Number
1(c)(i)
Additional Guidance
(1)
sodium hydroxide solution can be added rapidly / not
drop by drop to a volume a little below that of the
rough titration (making the titration quicker)
Allow add acid dropwise / slow down as it gets close to /
before the rough titration value / value in (b)(ii)
Allow added rapidly to the volume given in (b)(ii) minus
about 2 cm3 or so
Do not award slow down when you get to the rough
titration value
Do not award the rough titration is a value that you try to
get as close to as possible
Answer
Additional Guidance
Example of calculation
•
calculation of mean titre
Mark
Mark
(1)
(23
...
35 + 23
...
3(0) (cm3)
Correct answer with no working scores 1
Question
Number
1(c)(ii)
Answer
Additional Guidance
Example of calculation
•
calculation of number of moles
(23
...
100) ÷ 1000 = 0
...
33 × 10‒3 (mol)
Allow TE on (c)(i)
Mark
(1)
Question
Number
1(c)(iii)
Answer
Additional Guidance
Example of calculation
Mark
(3)
•
calculation of number of moles of H2A in 25
...
001165 / 1
...
54 ÷ 10) ÷ moles of H2A in 25
...
188/ 132
...
g
...
g
...
(3)
thermometer
still head
condenser
pear-shaped
flask
(1)
Allow a stopper / bung in place of a thermometer, but
must be named
Do not penalise a second collecting vessel (e
...
21)
Additional Guidance
Mark
(1)
Allow sulfur forms a yellow solid / comes out of solution /
does not dissolve
Allow just ‘sulfur is formed’
Answer
Mark
(1)
A is not correct because this is the concentration in the first experiment which is diluted with water and acid
B is not correct because this is the concentration in the most concentrated of the experiments and is diluted with acid
D is not correct because this is the ratio of the volumes of thiosulfate and total volume in the reaction = 5/7
Question
Answer
Number
6(b)(ii)
An answer that makes reference to the following point:
•
so that the total volume of the reaction mixture
is kept constant / 70 cm3
Additional Guidance
Mark
(1)
Accept the volume of sodium thiosulfate and water is kept
constant / 50 cm3
Allow the same volume of 70 cm3 / 50 cm3
Question
Number
6(c)(i)
Answer
Additional Guidance
Example of calculation
•
find the value of 1/time for the concentration of
0
...
03 (s‒1)
time = 1 ÷ 0
...
3 / 33
...
0305 = 32
...
8 (s)
Question
Answer
Number
6(c)(ii)
An answer that makes reference to the following point:
•
(directly) proportional
and
because the graph is a straight line (which passes
through the origin)
Additional Guidance
(1)
Allow just directly proportional
Allow as concentration doubles rate doubles
Allow linear
Ignore increasing concentration increases rate
Question
Answer
Number
6(d)
The only correct answer is A (rinsing the flask with deionised water before each new experiment)
B is not correct because any effect on the rate of the reaction will be equal in each case
C is not correct because each cylinder is the same size so will measure with the same accuracy
D is not correct because this will not affect the rate of the reaction
Mark
Mark
(1)
Question
Answer
Number
6(e)
The only correct answer is B (the time taken will decrease using the 100 cm3 flask)
Mark
(1)
A is not correct because the depth of the solution has increased so more solid is between the eye and the cross
C is not correct because the depth of the solution has increased so more solid is between the eye and the cross
D is not correct because the depth of the solution has increased so more solid is between the eye and the cross
(Total for Question 6 = 7 marks)
Question
Acceptable Answer
Number
This question assesses a student’s ability to show a coherent and
*7
logically structured answer with linkages and fully-sustained
reasoning
...
The following table shows how the marks should be awarded for
indicative content
...
Answer shows a coherent and
logical structure with linkages and
fully sustained lines of reasoning
demonstrated throughout
...
Answer has no linkages between
points and is unstructured
...
For example, an answer with five indicative marking points, which is
partially structured with some linkages and lines of reasoning, scores
4 marks (3 marks for indicative content and 1 mark for partial
structure and some linkages and lines of reasoning)
...
In general it would be expected
that 5 or 6 indicative points would get 2 reasoning marks, and 3 or 4
indicative points would get 1 mark
for reasoning, and 0, 1 or 2
indicative points would score zero marks for reasoning
...
5O2(g) → CO2(g) + 2H2O(l)
•
state symbols and balancing
(1) Do not award multiples
Question
Number
8(a)(ii)
Answer
Additional Guidance
Example of calculation
•
calculation of moles of methanol burnt
(1)
(152
...
2) ÷ 32
...
0625 (mol)
•
calculation of expected energy transferred
by multiplying by number of moles
and
scaling to match units
(1)
726 × 0
...
375 (kJ)
•
calculation of temperature change by
dividing by 836
Award
726 000 × (ans 1) = 45 375 (J)
(1)
45
...
00418) = 54
...
3 (ºC)
/ 45
...
836 = 5 4
...
3 (ºC)
Award
45 375 ÷ (200 × 4
...
276 / 54
...
276 / 54
...
5
54
...
5 = 74
...
5 ‒ 20
...
3) ÷ 54
...
068 / (‒) 41%
32 – 54
...
3
22
...
3 × 100 = (‒) 41
...
3 ‒ (52
...
5)) ÷ 54
...
068 / 41%
Allow TE on temperature rise from (a)(ii)
Ignore SF except 1SF
Mark
(1)
Question
Number
Answer
Additional Guidance
An answer that makes reference to the following points:
•
•
(there is no need to use a balance with greater precision because)
the uncertainty of the 1 dp balance is very small (compared to the
percentage error)
(in thermochemistry experiments the random error associated with)
the heat lost to the surrounding causes a much bigger uncertainty in
the final value (than the balance)
or
the increased precision will not lead to greater accuracy /
the accuracy of the experiment is poor so a high degree of precision
will not give a better result
Mark
(2)
(1)
Allow the perentage error in the
temperature change is so high it would not
(1) lead to greater accuracy
(Total for Question 8 = 9 marks)
TOTAL FOR PAPER = 80 MARKS
Pearson Education Limited
Title: Edexcel as level chemistry question paper 2 june 2024 + mark scheme
Description: Mark Scheme (Results) Summer 2024 Pearson Edexcel GCE In Chemistry (8CH0) Paper 02: Core Organic and Physical Chemistry
Description: Mark Scheme (Results) Summer 2024 Pearson Edexcel GCE In Chemistry (8CH0) Paper 02: Core Organic and Physical Chemistry