Group 7(17), the halogensAQA A-Level Chemistry: Topic test

20 questions, 54 marks

AQA A-Level Chemistry

Group 7(17), the halogens topic test

Total 54 marks

Name

Class

Date

1
The Group 7 elements exist as diatomic molecules. A molecule of F₂ has 18 electrons, Cl₂ has 34, Br₂ has 70 and I₂ has 106.
(a)
Which statement correctly explains why the boiling points increase from F₂ to I₂?
[1 mark]
AThe covalent bond within the molecule becomes stronger down the group
BThe London forces between molecules become stronger as the number of electrons increases
CPermanent dipole-dipole forces between molecules become stronger
DThe molecules become more polar down the group
(b)
Which halide ion is the strongest reducing agent?
[1 mark]
AF⁻
BCl⁻
CBr⁻
DI⁻
(c)
Explain why fluorine is more electronegative than iodine.
[2 marks]
Total for question 1: 4 marks
2
A student adds concentrated sulfuric acid to solid sodium iodide in a fume cupboard. A black solid and purple fumes form, a yellow solid appears on the wall of the tube, and a smell of bad eggs is detected.
(a)
Which substance is responsible for the smell of bad eggs?
[1 mark]
ASO₂
BHI
CH₂S
DI₂
(b)
Which statement explains why iodide ions reduce concentrated sulfuric acid to hydrogen sulfide, whereas chloride ions do not reduce it?
[1 mark]
AIodide ions are better reducing agents because their outer electron is further from the nucleus and more shielded
BIodide ions are better reducing agents because they are smaller than chloride ions
CChloride ions are better reducing agents because they are smaller
DHydrogen iodide is more stable than hydrogen chloride
(c)
Write a half-equation for the oxidation of iodide ions to iodine and state the role of the concentrated sulfuric acid in these reactions.
[2 marks]
Total for question 2: 4 marks
3
A textile factory makes a bleaching solution by bubbling 7.20 dm³ of chlorine gas, measured at room temperature and pressure, into an excess of cold dilute aqueous sodium hydroxide. Take the molar volume as 24.0 dm³ mol⁻¹. Relative atomic masses: O 16.0, Na 23.0, Cl 35.5.
(a)
Write an equation for the reaction and calculate the mass of sodium chlorate(I), NaClO, formed.
[3 marks]
(b)
The sodium chlorate(I) is made up to 500 cm³ of solution. Calculate its concentration in mol dm⁻³, state one use of the solution and explain why it is effective for that use.
[4 marks]
Total for question 3: 7 marks
4
A swimming pool is sanitised with chlorine. The mains water used to fill it contains traces of bromide ions. A chemist also tests a stock solution of a sodium halide that may be contaminated with sodium carbonate. She adds acidified silver nitrate solution to the stock solution and obtains a cream precipitate that is insoluble in dilute ammonia solution but dissolves in concentrated ammonia solution.
(a)
Identify the halide ion in the stock solution. Explain why silver nitrate is used, why it is acidified with nitric acid, and how ammonia solution allows the halide ion to be identified. Include an ionic equation.
[6 marks]
(b)
Explain what happens when chlorine is added to the pool water, including the reaction with water and the effect on the bromide ions. Evaluate whether chlorine is a suitable sanitiser for this pool.
[6 marks]
Total for question 4: 12 marks
5
Astatine is the radioactive Group 7 element below iodine, with proton number 85. Chemists predict its properties by extending the trends seen down the group.
(a)
Which prediction about astatine is consistent with the trends in Group 7?
[1 mark]
AA solid, with a lower electronegativity than iodine
BA gas, with a higher electronegativity than iodine
CA liquid, with a lower electronegativity than iodine
DA solid, with a higher electronegativity than iodine
(b)
Which statement about the astatide ion, At⁻, is correct?
[1 mark]
AIt is a weaker reducing agent than I⁻
BIt is a weaker reducing agent than Cl⁻
CIt is a stronger reducing agent than I⁻
DIt is the same strength as I⁻ because both are halide ions
(c)
Predict whether astatine would displace bromine from aqueous sodium bromide. Explain your answer.
[2 marks]
Total for question 5: 4 marks
6
A student leaves a bucket of chlorinated tap water standing in strong sunlight. The smell of chlorine disappears and the disinfecting power of the water falls. In water, chlorine reacts to form chloride ions and chlorate(I) ions. In sunlight, chlorine also reacts with water to form chloride ions and oxygen.
(a)
Which equation represents the reaction of chlorine with water in sunlight?
[1 mark]
ACl₂ + H₂O → HCl + HClO
BCl₂ + H₂O → 2HCl + O₂
C2Cl₂ + H₂O → 4HCl + O₂
D2Cl₂ + 2H₂O → 4H⁺ + 4Cl⁻ + O₂
(b)
What is the name of the ClO⁻ ion?
[1 mark]
AChloride
BChlorate(I)
CChlorate(III)
DChlorate(V)
(c)
Explain why the water becomes acidic when chlorine dissolves in it.
[2 marks]
Total for question 6: 4 marks
7
A student adds excess acidified silver nitrate solution to 25.0 cm³ of 0.200 mol dm⁻³ aqueous sodium bromide. Relative atomic masses: Ag 107.9, Br 79.9.
(a)
Write an ionic equation, including state symbols, for the reaction, state the colour of the precipitate and calculate the amount of bromide ions, in mol, in the sample.
[3 marks]
(b)
Calculate the mass of silver bromide formed and the minimum volume, in cm³, of 0.100 mol dm⁻³ silver nitrate solution needed to precipitate all of the bromide ions.
[4 marks]
Total for question 7: 7 marks
8
A student's notes on the halogens include two statements. Statement 1: 'Chlorine is a stronger oxidising agent than bromine and iodine, so chlorine water oxidises bromide ions and iodide ions, but iodine cannot oxidise chloride ions.' Statement 2: 'When chlorine reacts with cold dilute sodium hydroxide, chlorine is only reduced, forming sodium chloride and water.'
(a)
Evaluate Statement 1, explaining the trend in oxidising ability and including equations for the reactions that occur.
[6 marks]
(b)
Evaluate Statement 2, giving the equation for the reaction and a use of the solution formed.
[6 marks]
Total for question 8: 12 marks

End of questions

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).