3 3
(i) When a person exercises vigorously the concentration of carbon dioxide (aq)
in the blood increases.
Explain how this increase in the concentration of carbon dioxide affects the
pH of the blood.
Refer to the equilibria in your answer. No calculation is required.
(2)
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(ii) Explain how the carbonic acid–hydrogencarbonate buffer system in
Equilibrium 2 acts to restore the pH of the blood after a person has exercised.
(2)
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(Total for Question 4 = 14 marks)
Question
Mathematics
Edexcel2024
(1)
IO− + I− + H+ → 3I +
Question
Mathematics
Edexcel2024
2 3 2 2
Standard molar entropy
101.7 135.0 213.6 69.9
/ J K−1 mol−1
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(b) Calculate the minimum temperature, in degrees Celsius (°C), at which an oven
should be set for this reaction to be thermodynamically feasible.
(2)
Minimum temperature = °C
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(Total for Question 9 = 5 marks)
*P76895A02428*
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Question
Mathematics
Edexcel2024
0 cm3 of the vitamin C tablet solution from Step 1 was added to the conical
flask from Step 2 to react with the iodine produced, as shown in the equation.
C H O (aq) + I (aq) → C H O (aq) + 2HI(aq)
................ ................ 2 ...............................
(ii) Show, by calculation, that 7.50 × 10−4 moles of iodine were produced in
the flask.
(2)
(c) Step 3 Titrating with sodium thiosulfate solution.
Question
Mathematics
Edexcel2024
p(cid:31)SO (cid:30)
D 3 atm−½
p(cid:31)SO (cid:30)p(cid:31)O (cid:30)½
Question
Mathematics
Edexcel2024
2 3 2 2 r
(3)
Compound NaHCO (s) Na CO (s) CO (g) H O(l)
Question
Mathematics
Edexcel2024
*P76895A0328*
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Question
Mathematics
Edexcel2024
This question is about compounds and their chemical analysis.
Three containers of soluble white solids have lost their labels but are known to be
calcium bromide, calcium iodide and potassium sulfate.
(a) (i) Describe how to carry out a flame test on these samples.
(3)
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(ii) Give the expected observation for each of the flame tests.
(2)
calcium bromide
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calcium iodide
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potassium sulfate
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(b) Separate aqueous solutions of calcium bromide and of calcium iodide reacted
with acidified silver nitrate to produce a precipitate.
Concentrated aqueous ammonia was added to each precipitate.
Complete the table.
(2)
Formula of Observation with
Colour of precipitate
Solution precipitate with concentrated
with silver nitrate
silver nitrate aqueous ammonia
calcium bromide(aq)
calcium iodide(aq)
(c) Describe a chemical test for the sulfate ion giving the positive result.
(2)
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(d) What mass of potassium sulfate (K SO ) would be needed to prepare 250 cm3 of a
Question
Mathematics
Edexcel2024
p(cid:31)SO (cid:30)p(cid:31)O (cid:30)½
C 2 2 atm−½
p(cid:31)SO (cid:30)
Question
Mathematics
Edexcel2024
2 3
(a) (i) What are the expression and the units for the equilibrium constant (K ) for
p
this reaction?
(1)
Expression Units
p(cid:31)SO (cid:30)
A 3 atm2
p(cid:31)SO (cid:30)p(cid:31)O (cid:30)½
Question
Mathematics
Edexcel2024
2 2 3
Equilibrium 2 H CO (aq) H+(aq) + HCO−(aq)
Question
Mathematics
Edexcel2024
2 3
(3)
*P76895A01028*
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(e) The relevant equilibria that maintain the pH of blood are shown.
Equilibrium 1 CO (aq) + H O(l) H CO (aq)
Question
Mathematics
Edexcel2024
10
Question
Physics
CAIE2024
Fig. 5.1 shows a pendulum consisting of a metal sphere suspended by a thin string.
thin string
metal sphere
oscillations
Fig. 5.1 (not to scale)
The sphere undergoes small oscillations about its equilibrium position. The oscillations may be
considered to be simple harmonic.
Fig. 5.2 shows the variation with time t of the displacement x of the sphere from its
equilibrium position.
Question
Mathematics
Edexcel2023
The following reversible reaction is used in industry to make methanol, CH OH:
Question
Mathematics
Edexcel2023
4 4
Stage 2: HSO – (aq) H+(aq) + SO 2–(aq)
Question
Mathematics
Edexcel2023
7 2
Equilibrium 2
Cl (aq) + 2e– 2Cl–(aq) Ed = +1.36 V
Question
Mathematics
Edexcel2023
7
agent made the statement shown.
‘Standard electrode potential data shows that it is never feasible
for a 1.00 mol dm–3 solution of potassium dichromate(VI) to oxidise
the chloride ions in hydrochloric acid.’
Comment on this statement using the data and equilibria shown.
Equilibrium 1
Cr O2–(aq) + 14H+(aq) + 6e– 2Cr3+(aq) + 7H O(l) Ed = +1.33 V
Question
Mathematics
Edexcel2023
6
(i) State the colour of this complex ion.
(1)
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(ii) Explain why the aqueous solution of this complex ion has an acidic pH by
considering the interaction between the metal ion and the ligands.
(2)
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800 mol dm–3 of sodium hydroxide solution.
This resulted in a temperature rise of 2.9 °C.
Calculate the standard enthalpy change of neutralisation, Δ Hd, of
neut
quinic acid in kJ mol–1.
[Assume the density of both solutions is 1.0 g cm–3.
specific heat capacity of solution formed = 4.18 J g–1 °C–1]
(3)
Question
Mathematics
Edexcel2023
*P71912A01028*
PMT
(b) What happens to the position of the equilibrium and the colour of the mixture
when the pressure is increased?
The volume of the system remains constant.
N O (g) 2NO (g)
Question
Mathematics
Edexcel2023
4 3 2 3 4
Which statement about this equilibrium is correct?
(1)
A HNO and H NO + are a conjugate acid-base pair
Question
Mathematics
Edexcel2023
This question is about the decomposition of dinitrogen tetroxide.
The reaction eventually reaches equilibrium.
N O (g) 2NO (g)
Question
Mathematics
Edexcel2023
6 2 4
What is the most likely numerical value of K for this equilibrium?
c
(1)
A 1.0 × 106
B 5.0 × 103
C 1.0
D 5.0 × 10–3
(Total for Question 3 = 9 marks)
Question
Mathematics
Edexcel2023
Acids can be classified as weak or strong acids.
(a) A mixture of concentrated sulfuric and nitric acids is used in the nitration of benzene.
The following equilibrium is set up:
H SO + HNO H NO + + HSO –
Question
Mathematics
Edexcel2023
2 dm3 at a temperature of 500 K and a pressure of 100 atmospheres and allowed to
reach equilibrium.
The equilibrium mixture is found to contain 0.086 mol of CH OH(g).
Question
Mathematics
Edexcel2023
6
I Cl ICl+ + ICl–
Question
Mathematics
Edexcel2023
(1)
A octahedral
B square planar
C tetrahedral
D trigonal bipyramidal
(iii) The equilibrium position for the dissociation of molten I Cl lies to the left.
Question
Mathematics
Edexcel2023
6 2 4
(i) Draw a labelled diagram of a simple experiment to confirm this dissociation
has occurred, stating the positive result.
(2)
Result
..................................................................................................................................................................................................................................................................
(ii) What is the shape of the ICl– ion?
Question
Mathematics
Edexcel2023
6
When molten, it is suggested that it breaks down as shown.
I Cl ICl+ + ICl–
Na Mg Al Si P
Elements in Period 3
Explain the variations in melting temperature across the period in terms of the
structure and bonding in these elements.
(6)
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Question
Mathematics
Edexcel2023
Chemists often use the term ‘orbital’ when considering atomic structure.
(a) State what is meant by the term orbital.
(2)
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(b) Draw diagrams to show the shape of an s and a p orbital.
(2)
s orbital p orbital
(c) What is the electronic configuration of a copper atom?
(1)
A [Ar]4s13d10
B [Ar]4s23d9
C [Ar]4s24p13d8
D [Ar]4s24p23d7
(Total for Question 2 = 5 marks)
Question
Mathematics
Edexcel2023
4 2
colourless brown
(a) The table shows values of ΔG at different temperatures for this reaction.
Temperature / K ΔG / kJ mol–1
350 –4.0
400 –13
450 –22
500 –31
550 –40
(i) Plot a graph of ΔG against temperature.
(2)
ΔG / kJ mol–1
Temperature / K
Question
Mathematics
Edexcel2023
3
Ionisation
energy
Question
Mathematics
Edexcel2023
4 2
colourless brown
(1)
Position of equilibrium Change in colour
A moves to the right mixture gets lighter
B moves to the right mixture gets darker
C moves to the left mixture gets lighter
D moves to the left mixture gets darker
(Total for Question 5 = 7 marks)
Question
Mathematics
Edexcel2023
*P71912A0228*
PMT
Answer ALL questions.
Some questions must be answered with a cross in a box . If you change your mind about an
answer, put a line through the box and then mark your new answer with a cross .
Question
Mathematics
Edexcel2023
4 3
complex ion [Cr(H O) ]3+(aq).
Question
Mathematics
Edexcel2023
3
(a) Which change would affect both the value of the equilibrium constant, K , and the
c
proportion of methanol present in an equilibrium mixture of the three gases?
(1)
A adding a catalyst
B changing the temperature
C increasing the concentration of carbon monoxide
D increasing the pressure
(b) The expression for the equilibrium constant, K , for this reaction is
c
[CH OH(g)]
Question
Mathematics
Edexcel2023
K =
c 2
[CO(g)][H (g)]
Question
Chemistry
CAIE2023
The Haber process produces ammonia by the reversible reaction:
N₂(g) + 3H₂(g) ⇌ 2NH₃(g) ΔH = −92 kJ mol⁻¹
(a) State Le Chatelier's principle.
(b) Predict and explain the effect on the equilibrium yield of ammonia if:
(i) the pressure is increased
(ii) the temperature is increased
(c) Explain why a catalyst is used in the Haber process even though it does not change the equilibrium yield.