A student prepares 600cm3 of a buffer solution by mixing 400cm3 of0.500mol dm–3
ethanoic acid solution with 200cm3 of 0.500moldm–3 sodium ethanoate solution,
CH COONa.
Question
Mathematics
Edexcel2021
This question is about acids and buffer solutions.
(a) Ethanoic acid, CH COOH, is a monobasic acid.
Question
Mathematics
Edexcel2019
*P58306A0228*
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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
Edexcel2019
This question is about some redox reactions of chlorine, bromine and iodine.
(a) An excess of aqueous potassium bromide was added to chlorine water and the
solution turned orange.
(i) Write an equation for this reaction. State symbols are not required.
(1)
(ii) Silver nitrate solution was added to the mixture in (a) and excess
dilute ammonia solution was then added to the precipitate formed.
Only some of the precipitate dissolved.
Deduce why only some of the precipitate dissolved.
(3)
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(iii) Aqueous potassium bromide was added to aqueous iodine, instead of
chlorine water. There was no reaction.
Give a reason why no reaction occurred.
(1)
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Question
Mathematics
Edexcel2019
8 2 4
(i) Give a reason why the reaction between iodide ions and peroxodisulfate ions
has a high activation energy and is therefore very slow without a catalyst.
(1)
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(ii) Explain, with the aid of two equations, how the iron(II) ions catalyse this
reaction. State symbols are not required.
(3)
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(b) The oxidation of sulfate(IV) ions to sulfate(VI) ions is catalysed by cobalt(II) ions in
acidic solution. The role of cobalt(II) ions is similar to that of iron(II) ions in (a).
Co2+
SO2– + ½O (cid:127)(cid:111) SO2–
Question
Mathematics
Edexcel2019
B H +
C Mn 2+
D MnO –
Question
Mathematics
Edexcel2019
First ionisation energy of sodium
+496 kJ mol–1
Na(g) + ½H (g)
Question
Mathematics
Edexcel2019
The expression for the ionic product of water is
K = [H+(aq)] [OH–(aq)]
w
The value of K at 310 K is 2.40 × 10–14 mol2 dm–6
w
(i) Calculate the pH of water at 310 K.
Give your answer to two decimal places.
(2)
(ii) Predict, with a reason, whether water is acidic, alkaline or neutral at 310 K.
(2)
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(iii) Predict, with a reason, the sign of the enthalpy change for the ionisation of water.
(1)
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(Total for Question 6 = 15 marks)
Question
Mathematics
Edexcel2019
Enthalpy change of atomisation Lattice energy
of sodium of sodium –804 kJ mol–1
+107 kJ mol–1
hydride
Na(s) + ½H (g)
Question
Mathematics
Edexcel2019
Enthalpy change of formation
of sodium hydride –56 kJ mol–1
NaH(s)
(i) Identify and correct the two errors in this Born-Haber cycle.
(2)
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(ii) Calculate the first electron affinity, in kJ mol–1, of hydrogen, using the values
given in the cycle.
(1)
Question
Mathematics
Edexcel2019
f
The standard entropy change of the system, (cid:168)S , for this reaction is
system
–76.5 J K–1 mol–1.
(i) Deduce the feasibility of this reaction at 298 K by calculating the free energy
change, (cid:168)G.
(2)
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(ii) Calculate the temperature at which (cid:168)G = 0.
(1)
Question
Mathematics
Edexcel2019
2 2
In an alkaline fuel cell the oxidation half-equation is
H (g) + 2OH–(aq) (cid:111) 2H O(l) + 2e– 2 2
Deduce the reduction half-equation for the alkaline fuel cell.
State symbols are not required.
(1)
(d) Lattice energies provide an indication of ionic bond strength.
Which are the lattice energies of the hydrides NaH, KH and MgH ?
Question
Mathematics
Edexcel2019
(1)
Lattice energy / kJ mol–1
Sodium hydride, NaH Potassium hydride, KH Magnesium hydride, MgH
Question
Mathematics
Edexcel2019
A –804 –711 –1018
B –804 –711 –2718
C –804 –911 –1018
D –804 –911 –2718
(Total for Question 8 = 8 marks)
Question
Mathematics
Edexcel2019
This is a question about buffer solutions.
(a) A buffer solution always
(1)
A keeps the pH less than 7.
B contains equimolar amounts of acid and its conjugate base.
C keeps the pH constant if small quantities of acid or base are added.
D resists changes in pH if small quantities of acid or base are added.
(b) A buffer solution with a pH of 3.90 is required.
Calculate the mass, in grams, of sodium ethanoate that should be added to
Question
Mathematics
Edexcel2019
3 3
Explain how this buffer system helps to control the pH of blood when extra
carbon dioxide is present due to strenuous exercise.
(3)
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Question
Mathematics
Edexcel2019
2 3
The composition of an equilibrium mixture at 698 K and a total pressure of
Question
Mathematics
Edexcel2019
40 atm is shown in the table.
Substance SO (g) O (g) SO (g)
Question
Mathematics
Edexcel2019
2 3
Number of moles /mol 0.0160 0.0120 0.772
(i) Calculate the value of K at this temperature.
p
Include units, if appropriate.
(5)
(ii) Calculate the number of sulfur dioxide molecules present in this equilibrium mixture.
(1)
Question
Mathematics
Edexcel2019
[H O]4
D K = 2
c
[H ]4
Question
Mathematics
Edexcel2019
(Total for Question 10 = 11 marks)
TOTAL FOR PAPER = 90 MARKS
Question
Mathematics
Edexcel2017
This question is about buffer solutions.
(a) A buffer solution is formed from disodium hydrogenphosphate, containing HPO2– ions,