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A-level Chemistry (AQA) - Inorganic Chemistry > Module 3: Group 7 (The Halogens) > Flashcards

Module 3: Group 7 (The Halogens) Flashcards

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1
Q

What is the trend in boiling points down group 7 & why?

A
  • Increases.
  • Increasing strength of Van der Waals forces as atomic radius & relative mass of molecules increases.
  • More energy is required to break the bonds.
  • Observed in changes of physical state from fluorine (gas) to iodine (solid).
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2
Q

What is the trend in electronegativity down group 7 & why?

A
  • Decreases.
  • Atom radius & shielding increases.
  • Less attraction between outer electrons & protons in the nucleus.
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3
Q

What are the four halogens?

A
  • Fluorine
  • Chlorine
  • Bromine
  • Iodine
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4
Q

What is the appearance of flourine?

A
  • Very pale yellow gas.
  • Highly reactive.
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5
Q

What is the appearance of chlorine?

A
  • Pale green gas.
  • Poisonous in high concentrations.
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6
Q

What is the appearance of bromine?

A
  • Red-brown liquid.
  • Produces dense brown or orange poisonous fumes.
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7
Q

What is the appearance of iodine?

A
  • Shiny grey solid.
  • Sublimes to a purple gas.
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8
Q

Are the halogens oxidising or reducing agents?

A
  • Oxidising.
  • They can accept electrons & be reduced.
  • E.g. F2 (g) + 2e- –> 2F- (aq)
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9
Q

What is the trend in oxidising power down group 7 & why?

A
  • Decreases.
  • Atom radius & shielding increases.
  • Outer electrons are less attracted to the nucleus.
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10
Q

What is the trend in reducing power down group 7 & why?

A
  • Increases.
  • Atomic radius & shielding increases.
  • Electrons are less attracted to the nucleus so more readily lost.
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11
Q

What is the trend in displacement reactions down group 7?

A
  • A halogen will displace a halide from solution if the halide is below it in the periodic table.
  • E.g. chlorine can displace bromide ions, but chloride ions are displaced by flourine.
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12
Q

What happens when potassium chloride reacts with iodine?

A

No visible reaction.

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13
Q

What happens when potassium bromide reacts with chlorine?

A
  • Orange solution is formed (Br2).
  • Cl has displaced Br.
  • Cl2 (aq) + 2Br- (aq) –> 2Cl- (aq) + Br2 (aq)
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14
Q

What happens when potassium bromide reacts with bromine?

A

No visible reaction.

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15
Q

What happens when potassium bromide reacts with iodine?

A

No visible reaction.

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16
Q

What happens when potassium iodide reacts with chlorine?

A
  • Brown solution is formed (I2).
  • Cl has displaced I.
  • Cl2 (aq) + 2I- (aq) –> 2Cl- (aq) + I2 (aq).
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17
Q

What happens when potassium iodide reacts with bromine?

A
  • A brown solution is formed (I2).
  • Br has displaced I.
  • Br2 (aq) + 2I- (aq) –> 2Br- (aq) + I2 (aq).
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18
Q

What happens when potassium iodide (KI) reacts with iodine?

A

No visible reaction.

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19
Q

What can H2SO4 act as?

A

An acid or an oxidising agent.

20
Q

What occurs when H2SO4 is acting as an acid?

A
  • Converts the sodium salts of the halides into hydrogen halides.
  • E.g. H2SO4 (l) + NaX (s) –> NaHSO4 (s) + HX (g)
21
Q

What occurs when H2SO4 is acting as an oxidising agent?

A
  • Sulfuric acid can be reduced to SO2, S or H2S.
  • E.g H2SO4 + 2H+ + 2e- –> SO2 + 2H2O
  • E.g. H2SO4 + 6H+ + 6e- –> S + 4H2O
  • E.g. H2SO4 + 8H+ + 8e- –> H2S + 4H2O
22
Q

What is the equation for the reaction of H2SO4 with NaF?

A

NaF (s) + H2SO4 (l) –> NaHSO4 (s) + HF (g)

23
Q

What is observed during the reaction of H2SO4 with NaF?

A

White, steamy fumes of HF.

24
Q

What is the equation for the reaction of H2SO4 with NaCl?

A

NaCl (s) + H2SO4 (l) –> NaHSO4 (s) + HCl (g)

25
Q

What is observed during the reaction of H2SO4 with NaCl?

A
  • White, steamy fumes of HCl.
26
Q

What is the equation for the reaction of H2SO4 with NaBr?

A

NaBr (s) + H2SO (l) –> NaHSO4 (s) + HBr (g)

27
Q

What is observed during the reaction of H2SO4 with NaBr?

A

White, steamy fumes of HBr.

28
Q

What is the equation for the further reaction of H2SO4 with HBr?

A

2HBr (g) + H2SO4 (l) –> Br2 (g) + SO2 (g) + 2H2O

29
Q

Why can further reduction occur after the reaction of H2SO4 with NaBr?

A

HBr is a stronger reducing agents than HCl so further reduction can occur.

30
Q

What is observed during the further reduction of H2SO4 with HBr?

A

Red fumes of bromine & SO2 (a colourless, acidic gas).

31
Q

What is the equation for the reaction of H2SO4 with NaI?

A

NaI (s) + H2SO4 (l) –> NaH (s) + HI (g)

32
Q

What is observed during the reaction of H2SO4 with NaI?

A

White, steamy fumes of HI.

33
Q

What is the equation for the further reaction of H2SO4 with HI?

A

2HI (g) + H2SO4 (l) –> I2 (s) + SO2 (g) + 2H2O (l)

34
Q

What is observed during the further reaction of H2SO4 with HI?

A

Black solid and purple fumes of iodine & SO2 gas.

35
Q

What is the equation for the further reaction of HI with SO2?

A

6HI (g) + SO2 (g) –> H2S (g) + 3I2 (s) + 2H2O (l)

36
Q

What is observed during the further reaction of HI with SO2?

A

Fumes of H2S gas with a pungent egg smell & solid iodine.

37
Q

Why can two further reductions occur after the initial reaction of H2SO4 with NaI?

A

Because HI is the strongest reducing agent so can further reduce SO2 to H2S.

38
Q

What test can be used to identify the halide solutions?

A

The silver nitrate test.

38
Q

What is the process for the silver nitrate test?

A
  • Add dilute nitric acid to the halide solution.
  • Then add a few drops of silver nitrate solution (AgNO3).
  • A precipitate of the silver is produced & the colour identifies the halide.
39
Q

Why is dilute nitric acid added to the test?

A

To remove any carbonate ions that may interfere with the test & prevent the formation of Ag2CO3 which would mask observations.

40
Q

What does the presence of a white precipitate indicate?

A

The presence of chloride ions.

41
Q

What does the presence a cream precipitate indicate?

A

The presence of bromide ions.

42
Q

What does the presence of a yellow precipitate indicate?

A

The presence of iodide ions.

43
Q

What does no precipitate indicate?

A

The presence of fluoride ions.

44
Q

Why do fluoride ions not produce a precipitate?

A

Because silver fluoride is soluble in water.

A-level Chemistry (AQA) - Inorganic Chemistry (6 decks)

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