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AQA A Level Inorganic Chemistry > 3. Group 7, the halogens > Flashcards

3. Group 7, the halogens Flashcards

1
Q

What is electronegativity?

A

The power of an atom to attract the electrons in a covalent bond

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2
Q

What happens to electronegativity down group 7?

A

It decreases

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3
Q

Why does electronegativity decrease down group 7?

A
  • atoms get larger down group so outer electrons are further from nucleus
  • outer electrons are more shielded
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4
Q

What happens to boiling point down group 7?

A

It increases

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5
Q

Why does boiling point increase down group 7?

A
  • halogens are simple molecular so held together by VDWs

* strength of VDWs ↑ as size of the molecule ↑ (i.e. number of electrons within the molecule ↑)

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6
Q

Why do larger molecules have stronger VDWs forces?

A

More electrons present, so greater asymmetrical distribution of charge

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7
Q

What is oxidising ability?

A

The ability for elements to accept an electron to become ions

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8
Q

What is the oxidising ability of halogens?

A

The ability of the halogens to accept an electron to become halide ions

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9
Q

Are halogens good oxidising agents?

A

Yes

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10
Q

Why are halogens good oxidising agents?

A

They have the ability to accept an electron to become halide ions

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11
Q

What happens to oxidising power down group 7?

A

It decreases

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12
Q

Why does the oxidising power of the halogens decrease down group 7?

A
  • atomic radius ↑
  • more shielding
  • therefore worse at gaining an electron due to ↓ nuclear attraction
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13
Q

Where can the trend that the oxidising power of the halogens decreases down the group be seen?

A

In the reactions of halogens with halide ions in solution where the more reactive halogen will displace the less reactive halogen from the solution

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14
Q

Why can’t the oxidising ability of fluorine be shown in the reaction of halogens with halide ions in solution?

A

F2 reacts with water so cannot be investigated this way

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15
Q

What is the difference between a halide and a halogen in terms of how they react?

A

Halogens are reduced; halides are oxidised

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16
Q

What does ‘the reducing ability of the halides’ mean?

A

The ability to cause other atoms to gain electrons

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17
Q

What happens to the reducing ability of the halides down group 7?

A

It increases

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18
Q

Why does the reducing ability of the halides increase down group 7?

A
  • larger halide ion so easier to donate electrons
  • outermost electrons further from attraction of nucleus and more shielded by outer electrons
  • therefore attraction for the outermost electrons → weaker
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19
Q

What are the observations when a solid metal chloride is added to sulphuric acid?

A

White misty fume

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20
Q

What are the observations when a solid metal bromide is added to sulphuric acid?

A
  • white misty fume
  • orange/brown fume
  • sodium dichromate paper → green
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21
Q

What are the observations when a solid metal iodide is added to sulphric acid?

A
  • white misty fume
  • purple fumes
  • sodium dichromate paper → green
  • yellow solid
  • rotten egg smell or lead ethanoate paper → black in presence of H₂S
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22
Q

What is the product when sulphuric acid has been added to a solid metal chloride?

A

HCl

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23
Q

What are the products when sulphuric acid has been added to a solid metal bromide?

A
  • HBr
  • Br₂
  • SO₂
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24
Q

What are the products when sulphuric acid has been added to a solid metal iodide?

A
  • HI
  • I₂
  • SO₂
  • S
  • H₂S
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25
Q

What produces the white misty fume when sulphuric acid is added to a solid metal chloride/bromide/iodide?

A

HCl/HBr/HI

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26
Q

What produces the orange/brown fume when sulphuric acid is added to a solid metal bromide?

A

Br2

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27
Q

What makes potassium dichromate paper go green when sulphuric acid is added to a solid metal bromide/iodide?

A

SO2

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28
Q

What produces a purple fume when sulphuric acid is added to a solid metal iodide?

A

I2

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29
Q

What produces the yellow solid when sulphuric acid is added to a solid metal iodide?

A

S

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30
Q

What produces the rotten egg smell, or can turn lead ethanoate paper black when sulphuric acid is added to a solid metal iodide?

A

H2S

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31
Q

What is the reaction type when a white misty fume is formed from the reaction of sulphuric acid with a solid metal halide?

A

Acid-base (produce HCl, HBr or HI)

32
Q

What is the reaction type when an orange/brown fume is formed from the reaction of sulphuric acid with a solid metal bromide ?

A

Oxidation (produce Br2)

33
Q

What is the reaction type when a potassium dichromate paper turns green from the reaction of sulphuric acid with a solid metal bromide/iodide?

A

Reduction (produce SO2)

34
Q

What is the reaction type when a purple fume is formed from the reaction of sulphuric acid with a solid metal iodide?

A

Oxidation (produce I2)

35
Q

What is the reaction type when a yellow solid is formed from the reaction of sulphuric acid with a solid metal iodide?

A

Reduction (produce S)

36
Q

What is the reaction type when a rotten egg smell/lead ethanoate paper turns black from the reaction of sulphuric acid with a solid metal iodide?

A

Reduction (produce H2S)

37
Q

Equation for when a solid metal chloride reacts with sulphuric acid to form a white misty fume?

A

NaCl + H₂SO₄ → NaHSO₄ + HCl

38
Q

Equation for when a solid metal bromide reacts with sulphuric acid to form a white misty fume?

A

NaBr + H₂SO₄ → NaHSO₄ + HBr

39
Q

Equation for when a solid metal iodide reacts with sulphuric acid to form a white misty fume?

A

NaI + H₂SO₄ → NaHSO₄ + HI

40
Q

Equation for when a solid metal bromide reacts with sulphuric acid to form an orange/brown fume?

A

2Br⁻ → Br₂ + 2e⁻

41
Q

Equation for when a solid metal bromide reacts with sulphuric acid to turn potassium dichromate paper green?

A

H₂SO₄ → SO₂

H₂SO₄ + 2H⁺ + 2e⁻ → SO₂ + H₂O

42
Q

Equation for when a solid metal iodide reacts with sulphuric acid to form a purple fume?

A

2I⁻ → I₂ + 2e⁻

43
Q

Equation for when a solid metal iodide reacts with sulphuric acid to turn potassium dichromate paper green?

A

H₂SO₄ → SO₂

H₂SO₄ + 2H⁺ + 2e⁻ → SO₂ + H₂O

44
Q

Equation for when a solid metal iodide reacts with sulphuric acid to form a yellow solid?

A

6H⁺ + 6e⁻ + H₂SO₄ → S + 4H₂O

45
Q

Equation for when a solid metal iodide reacts with sulphuric acid to form a rotten egg smell?

A

8H⁺ + 8e⁻ + H₂SO₄ → H₂S + 4H₂O

46
Q

Are silver halides insoluble?

47
Q

Do silver halides have different levels of solubility in ammonia solution?

48
Q

When identifying halide ions using silver nitrate, why is nitric acid added?

A

Removes any other ions that could give a precipitate with silver nitrate

(e.g. CO₃²⁺ + 2H⁺ → CO₂ + H₂O)

49
Q

When identifying halide ions using silver nitrate, why is silver nitrate added?

A

Produces a precipitate for Cl⁻, Br⁻ and I⁻ ions

50
Q

When identifying halide ions using silver nitrate, why is ammonia (dilute and concentrated) added?

A

To see if the precipitates re-dissolve to help confirm their identity

51
Q

How is the silver nitrate test carried out?

A
  • add nitric acid
  • add silver nitrate
  • add ammonia
52
Q

What does a white precipitate indicate in the silver nitrate test?

53
Q

What does a cream precipitate indicate in the silver nitrate test?

54
Q

What does a yellow precipitate indicate in the silver nitrate test?

55
Q

What happens when silver nitrate is added to chloride ions?

A

White precipitate

56
Q

What happens when silver nitrate is added to bromide ions?

A

Cream precipitate

57
Q

What happens when silver nitrate is added to iodide ions?

A

Yellow precipitate

58
Q

What happens when dilute ammonia is added to chloride ions?

A

Dissolves completely - as Cl is very soluble

59
Q

What happens when concentrated ammonia is added to chloride ions?

A

Dissolves completely

60
Q

What happens when dilute ammonia is added to bromide ions?

A

Partially dissolves

61
Q

What happens when concentrated ammonia is added to bromide ions?

A

Dissolves - Only dissolves in concentrated ammonia

62
Q

What happens when dilute ammonia is added to iodide ions?

A

Doesn’t dissolve

63
Q

What happens when concentrated ammonia is added to iodide ions?

A

Doesn’t dissolve

64
Q

Why doesn’t AgF form a precipitate with AgNO3?

A

It is soluble

65
Q

What happens to the solubility of the silver halides down group 7?

66
Q

What is chlorine used for?

A
  • to purify drinking water

* in swimming pools to kill bacteria

67
Q

What is formed when chlorine is added to water?

A

Hydrochloric acid and chloric acid (hence chloride and chlorate (I) ions

68
Q

When chlorine is added to water, what kind of reaction occurs?

A

Disproportionation - chlorine undergoes both oxidation and reduction

69
Q

In the reaction between chlorine and water, is chloric acid a reduction or oxidising agent?

A

Oxidising - kills bacteria through oxidation

70
Q

What does chloric acid do?

A

Kills bacteria through oxidation, also a bleach

71
Q

What is the safety issue with chlorine gas?

A
  • highly toxic - so an alternative to direct chlorination must be used
  • involves using solid chlorine containing compounds that produce chloric acid in water

(e.g. NaClO + H2O → NaOH + HClO)

72
Q

Why are swimming pools kept slightly acidic?

A

To prevent the equilibrium shifting to the left (e.g. in NaClO + H2O → NaOH + HClO)

73
Q

In sunlight, what happens when chlorine is added to water?

A

Cl2 + H20 → 2HCl + 1/2 O2

74
Q

Why is a more frequent addition of chlorine required in swimming pools that are positioned in sunlight?

A

In sunlight, Cl2 + H20 → 2HCl + 1/2 O2. This would reduce the chlorate (I) produced

75
Q

What is formed when chlorine is added to cold dilute sodium hydroxide solution?

A

Sodium chlorate (I)

76
Q

What is the equation for when chlorine is added to cold dilute sodium hydroxide solution?

A

Cl2 + 2NaOH → NaClO + NaCl + H2O

77
Q

Uses of sodium chlorate (II)?

A
  • common household bleach
  • water treatment to kill bacteria
  • to bleach paper or textiles

AQA A Level Inorganic Chemistry (6 decks)

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