AQA AS Chemistry

Topic Questions

2.3 Group 7 (17), the Halogens

11 mark

The halogens exist as diatomic molecules, X2.

Which statement is correct?

  • The boiling points of the halogens decrease down the group

  • The oxidising power of the halogens increases down the group

  • The electronegativity of X increases down the group

  • The number of electrons in each X2 molecule increases down the group

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21 mark

A scientist compares the properties of chlorine, iodine and their compounds.

Property X for iodine is bigger than for chlorine. 

What is property X?

  • Solubility of the silver halide in dilute NH3 (aq)

  • Reducing ability of the element

  • Strength of C-X bond 

  • Oxidising ability 

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31 mark

When chlorine reacts with cold sodium hydroxide the following reaction occurs

Cl2 (aq) + 2NaOH (aq) → NaCl (aq) + NaClO (aq) + H2O (l)

Which of the following statements is correct?

  • The chlorine has only been oxidised 

  • The oxidation number of Cl in NaClO is 0

  • The chlorine is simultaneously oxidised and reduced 

  • The oxidation number of Cl in Cl2 is -1 

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41 mark

A student added a solution of bromine to a solution of sodium iodide. 

Which statement is not correct?

  • The iodide ions are oxidised

  • Bromine is reduced

  • Bromine acts as the reducing agent

  • A brown solution is observed

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51 mark

When chlorine reacts with hot sodium hydroxide the following reaction occurs.

3Cl2 (g) + 6NaOH (aq) → 5NaCl (aq) + NaClO3 (aq) + 3H2O (l)

Which row shows the correct oxidation state of chlorine in each ion?

 

Cl2

NaCl

NaClO3

A

B

C

D

0

0

0

0

-1

+1

+1

-1

+5

-5

-3

+3

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61 mark

What are the correct observations for the reaction of solid sodium bromide and concentrated sulfuric acid?

  • White fumes

  • Reddish brown gas and yellow solid produced

  • Yellow solid produced

  • Reddish-brown gas and pungent odour

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71 mark

What is the correct chemical test and observation for the presence of an iodide ion?

 

Chemical test

Observation 

A

Acidified silver nitrate

Yellow precipitate insoluble in concentrated ammonia

B

Acidified barium chloride 

White precipitate insoluble in hydrochloric acid

C

Acidified potassium nitrate

Yellow precipitate insoluble in concentrated ammonia

D

Bromine water 

Brown solution changes to colourless solution

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81 mark

Which of the following equations involving chlorine is not correct?

  • Cl2 (aq) + H2O (l) → HCl (aq) + HClO (aq)

  • Cl2 (aq) + 2KBr (aq) → 2KCl (aq) + Br2 (aq) 

  • HClO (aq) ⇌ H+ (aq) + ClO- (aq)

  • I2 (aq) + 2KCl (aq) → 2KI (aq) + Cl2 (aq)

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91 mark

Why does the oxidising power of the halogens decrease as the group is descended?

  • Shielding increases down the group therefore it is more difficult to accept an extra electron 

  • Atomic radius decreases down the group  

  • Shielding increases down the group therefore it is easier to donate an electron

  • The halogens become more electronegative down the group

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101 mark

Which of the following statements about hydrogen halides, HX, is not correct?

  • The bond length of the H-X bonds increase down the group 

  • The reaction between fluorine and hydrogen is explosive

  • Hydrogen fluoride can form hydrogen bonds

  • The reaction between bromine and hydrogen is a vigorous reaction

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11 mark

Which of the following is the best oxidising agent?

  • Cl-

  • Br2

  • Br-

  • Cl2

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21 mark

Which of the following statements is not correct?

  • Silver bromide is soluble in concentrated ammonia 

  • Bromine is liberated when chlorine is added to sodium bromide 

  • Sulfur dioxide is produced when solid sodium chloride is added to concentrated sulfuric acid 

  • A purple colour can be observed when solid sodium iodide is added to concentrated sulfuric acid 

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31 mark

Astatine is a halogen which is found at the bottom of Group 7.

Solid sodium astatide, NaAt reacts in a similar way as sodium iodide, NaI when added to concentrated sulfuric acid.

What are some of the possible redox products formed in this reaction?

 

Na2SO4

SO2

At2

HAt

H2S

A

B

C

D

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41 mark

Hydrogen halides, H-X, are formed from the reaction of hydrogen and a halogen, X2. Which of the following statements correctly explains why HBr (aq) is a stronger acid than HF (aq)?

  • HF (aq) releases more H+ ions 

  • HF dissociates more readily than HBr when dissolved in solution 

  • The H-Br bond has the greatest bond dissociation energy 

  • The H-F bond is stronger so does not break as easily 

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51 mark

Dichlorine hexoxide, Cl2O6 is a dark red liquid at 298 K and is prepared by the reaction between ozone and ClO2, chlorine dioxide.

2ClO2 + 2O3 → Cl2O6 + 2O2

Which of the following statements is correct about this reaction?

  • Chlorine is reduced in this reaction 

  • The oxidation number of chlorine does not change 

  • The overall change in the oxidation number of chlorine is +2

  • The oxidation state of chlorine in Cl2O6 is +4

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61 mark

Chloric acid, HClO3, is a strong acid and can be prepared by the following reaction.

Ba(ClO3)2 (aq) + H2SO4 (aq) → BaSO4 (s) + 2HClO3 (aq)

What is the overall change in oxidation state of chlorine?

  • 0

  • +1

  • +2

  • +3

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71 mark

What is the reducing agent in this reaction?

Br- + 3HClO + 3OH- → BrO3- + 3Cl- + 3H2O

  • OH-

  • HClO

  • Br-

  • BrO3-

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81 mark

Chlorine gas can be prepared by oxidising concentrated hydrochloric acid with potassium permanganate. This reaction is carried out in a fume hood.

___HCl + ___KMnO4  →  ___Cl2 + ___KCl + ___MnCl2 + ___H2O

Which whole number stoichiometric coefficients are correct to balance the equation?

 

HCl

KMnO4

Cl2

KCl

MnCl2

H2O

A

8

2

3

4

4

2

B

8

2

3

2

2

4

C

16

4

5

4

2

8

D

16

2

5

2

2

8

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91 mark

Which of the following equations occurs between concentrated sulfuric acid and solid potassium bromide is correct

  • Br2 + 2e- → 2Br-

  • H2SO4 + 2HBr → Br2 + SO2 + 2H2O

  • SO42- + 10H+ + 8e- → H2S + 4H2O

  • H2SO4 + 6HBr → 3Br2 + S + 4H2O

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101 mark

A few drops of sodium chlorate (I) solution is added to potassium bromide solution. A red-brown gas is produced along with sodium chloride solution.

Which of the following statements is correct?

  • The oxidation state of chlorine in NaClO is +5

  • Chlorine gas is produced

  • Bromide ions are oxidised in this reaction  

  • NaClO is the reducing agent 

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11 mark

The following report appeared in a newspaper:

Barrels of bromine broke open after a vehicle collision on the motorway. Traffic was diverted as brown, bromine gas drifted over the surface of the road (as bromine is less dense than air), causing irritation to drivers’ eyes. Firemen sprayed water over the scene of the accident, dissolving the bromine and washing it away.

Which of the following observations is incorrect in the report?

  • bromine is not brown

  • bromine does not vaporise readily

  • bromine is less dense than air

  • bromine does not dissolve in water

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21 mark

Which list of the products from the reaction of potassium bromide with concentrated sulfuric acid is correct?

  • potassium hydrogensulfate, sulfur, hydrogen bromide, bromine and water 

  • potassium hydrogen sulfate, hydrogen bromide, bromine, water and sulfur dioxide 

  • potassium hydrogen sulfate, hydrogen bromide and bromine

  • potassium hydrogen sulfate, hydrogen bromide and hydrogen sulfide

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31 mark

Which graph correctly illustrates a trend found in Group 7?

zNITPn5~_4

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41 mark

The chemistry of the Group 7 elements often involves redox processes.

Which of the following statements is correct?

  • In reactions with water in the absence of sunlight, chlorine is oxidised and reduced simultaneously

  • Iodide ions are the strongest oxidising agent of the first four Group 7 ions

  • Iodine can oxidise bromide ions

  • Fluorine is a weaker oxidising agent than chlorine

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51 mark

When sulfuric acid and sodium iodide react, one of the reactions that takes place is shown by the equation below:

8NaI  +  9H2SO4  →  8NaHSO4  +  4I2  +  H2S  +  4H2O

Which species has been oxidised in this reaction?

  • H+

  • S

  • Na+

  • I-

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61 mark

A student analysed a solution containing a halide ion which was kept in an unlabelled bottle in the laboratory. Their tests and observations were recorded in the table below.

Test

Chemical test

Observation

1

Addition of chlorine water and cyclohexane

Organic layer colour change from colourless to brown

2

Addition of hydrochloric acid and silver nitrate

Off-white precipitate

Give the most likely halide ion or combination of halide ions present in the solution from the student’s results.

  • Iodide and bromide

  • Iodide

  • Chloride

  • Bromide

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71 mark

2-chloropropane, 2-bromopropane and 2-iodopropane are reacted separately with aqueous potassium hydroxide and acidified silver nitrate.

The reaction containing 2-iodopropane produces a precipitate the quickest. 2-chloropropane, 2-bromopropane and 2-iodopropane are reacted separately with aqueous potassium hydroxide and acidified silver nitrate.

The reaction containing 2-iodopropane produces a precipitate the quickest.

Which statement explains this most accurately?

  • The C-Br bond is more polar that the C-I bond

  • The C-Cl bond is the most polar and therefore strongest

  • The C-Cl bond is the shortest

  • The C-I bond is the longest

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81 mark

Which is the correct equation for the reaction of hot, dilute aqueous sodium hydroxide, NaOH, and chlorine, Cl2?

  • Cl2 + 2NaOH → NaCl + NaClO + H2O

  • 1 halfCl2 + 2OH- → ClO- + H2O + e-

  • begin mathsize 16px style 1 half end styleCl2 + 6OH- → ClO3- + 3H2O + e-

  • 3Cl2 + 6NaOH → 3NaCl + 3NaClO3 + H2O

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91 mark

What is the change in oxidation state of sulfur in the following reaction:

8KI  +  5H2SO4  →  4K2SO4  +  H2S  +  4I 2  +  4H2O

  • 6

  • 8

  • 10

  • 4

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101 mark

Why does the electronegativity of the halogens decrease down Group 7?

  • The atomic radii of the halogens decrease down the group.
    Therefore, the outer shell is further away from the nucleus so the oxidising power of the halogens decreases.

  • The atomic radii of the halogens increase down the group.
    Therefore the outer shell is further away from the nucleus so the ability to accept an electron decreases.

  • The atomic radii of the halogens increase down the group.
    Therefore the outer shell is further away from the nucleus so the reducing ability decreases.

  • The atomic radii of the halogens increases down the group.
    Therefore, the outer shell is further away from the nucleus so the oxidising power of the halogens increases.

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