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CHEMISTRY (AS) > Group 7 > Flashcards

Group 7 Flashcards

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1
Q

What form are group 7 elements usually found at? (1 mark)

A

⦾ Molecules (1)

⦾ F2 ⦾ Cl2 ⦾ Br2 ⦾ I2

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2
Q

What is the general trend in electronegativity down group 7? (1 mark)

A

⦾ Decrease (1)

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3
Q

Explain why the elctronegativities decrease down group 7? (3 marks)

A

⦾ Atoms get bigger (1)
⦾ Bigger attract e- less than smaller (1)
⦾ Outer e- further from nucleus (1)
⦾ And more shielded (with inner e-s) (1)

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4
Q

What is the general trend in boiling points down group 7? (1 mark)

A

⦾ Increase (1)

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5
Q

Explain why the melting points increase down group 7?

2 marks

A

⦾ Size + Ar increase (1)

⦾ Therefore increased strength of VWFs (1)

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6
Q

Why are halogens [O]? (1 mark)

A

⦾ React to gain e- (1)

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7
Q

What is the general trend in reactivity down group 7?

1 mark

A

⦾ Decrease (1)

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8
Q

Explain why the reactivities decrease down group 7?

2 marks

A

⦾ Atoms get larger (1)

⦾ Outer e- further from nucleus (1)

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9
Q

What does [O] ability depend on? (1 mark)

A

⦾ Reactivity (1)

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10
Q

Do halogens become more or less oxidising down the group? (1 mark)

A

⦾ Less [O] (1)

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11
Q

Explain what a displacement reaction in group 7 elements is? (2 marks)

A

⦾ Halogen displaces halide from (aq) (1)

⦾ If halide’s below it in periodic table (1)

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12
Q
  1. What is a halogen? (1 mark)
  2. What is a halide? (1 mark)

(Use X)

A
  1. X or X2

2. X-

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13
Q

For a displacement experiment, you should add a few drops of aqueous halogen to solution containing halide ions.

What shows a reactions occured? (1 mark)

A

⦾ Colour change (1)

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14
Q

What is the order of displacement? (1 mark)

A 
F
↓
Cl
↓
Br2
↓
I2            (1)
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15
Q

What happens when you:

Add Chlorine water to Potassium Bromide solution?

(2 marks)

A

⦾ Displaces (1)

⦾ Colourless → Orange (1)

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16
Q
  1. What is the equation for the the reaction of Chlorine water with Potassium Bromide? (1 mark)
  2. What is the ionic equation for the the reaction of Chlorine water with Potassium Bromide? (1 mark)
A
  1. Cl2(aq) + 2KBr(aq) → 2KCl(aq) + Br2(aq) (1)

2. Cl2(aq) + 2Br-(aq) → 2Cl-(aq) + Br2(aq) (1)

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17
Q

What happens when you:

Add Chlorine water to Potassium Iodide solution?

(2 marks)

A

⦾ Displaces (1)

⦾ Colourless → Brown (1)

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18
Q
  1. What is the equation for the the reaction of Chlorine water with Potassium Iodide? (1 mark)
  2. What is the ionic equation for the the reaction of Chlorine water with Potassium Iodide? (1 mark)
A
  1. Cl2(aq) + 2KI(aq) → 2KCl(aq) + I2(aq) (1)

2. Cl2(aq) + 2I-(aq) → 2Cl-(aq) + I2(aq) (1)

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19
Q

What happens when you:

Add Bromine water to Potassium Iodidie solution?

(2 marks)

A

⦾ Displaces (1)

⦾ Orange → Brown (1)

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20
Q
  1. What is the equation for the the reaction of Bromine water with Potassium Iodide? (1 mark)
  2. What is the ionic equation for the the reaction of Bromine water with Potassium Iodide? (1 mark)
A
  1. Br2(aq) + 2KI(aq) → 2KBr(aq) + I2(aq)

2. Br2(aq) + 2I-(aq) → 2Br-(aq) + I2(aq)

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21
Q

What happens when you:

  1. Add Bromine water to Potassium Chloride solution?
    (1 mark)
  2. And why? (1 mark)
A
  1. No reaction (1)

2. Cl more reactive than Br - Above in periodic table (1)

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22
Q

Explain why iodine won’t displace Bromine or Chlorine? (2 marks)

A

⦾ Less reactive (1)

⦾ Below both halides on periodic table (1)

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23
Q

How would Fluorine react in these displacement reactions? (1 mark)

A

⦾ Oxidises water instead (1)

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24
Q

What is a disproportionation reaction? (1 mark)

A

⦾ Element is both oxidised and reduced (1 mark)

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25
Q
  1. How do you make bleach? (1 mark)

2. What is the formula for bleach (1 mark)

A
  1. Mix Chlorine gas with cold, dilute Sodium Hydroxide solution at room temp (1)
  2. Get: Sodium chlorate(I)solution (1)
26
Q

What is the full equation for the disproportionation reaction for the formation of bleach? (2 marks)

A

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

27
Q

What is the type of reaction when Chlorine is mixed with Water? (1 mark)

A

⦾ Disproportionation (1)

28
Q

What is the full equation when Chlorine and Water mix?

2 marks

A

⦾ Cl2(g) + H2O(l) ⇌ 2H+(aq) + Cl-(aq) + ClO-(aq) (2)

29
Q
  1. In sunlight, what can Chlorine decompose Water to form? (2 marks)
  2. Whats in full equation for this? (2 marks)
A
  1. Chloride ions + Oxygen (2)

2. Cl2(g) + H2O(l) → 2H+(aq) + 2Cl-(aq) + 1/2O2(g) (2)

30
Q

Water treatment

A

⦾

31
Q

What do halide ions do when they take part in a redox reaction? (2 marks)

A

⦾ Reduces something (1)

⦾ Oxidises itself (1)

32
Q

How are halides able to reduce something? (1 mark)

A

⦾ Lose an e- (1)

33
Q

What is the trend in reducing power of halides down group 7? (1 mark)

A

⦾ Increases (1)

34
Q

Explain why the reducing power of halides increases down group 7? (4 marks)

A

⦾ (down group) attraction between nucleus + outer e- decreases (1)
⦾ (because) ions get bigger (1)
⦾ (so) e- get further from +ve nucleus (1)
⦾ shielding effect from inner e- shells (1)

35
Q

What is the general equation for the initial reaction of halides with concentrated sulfuric acid?

  • Write an equation using ‘X’ to represent halide (1 mark)
  • (Use Sodium halide)
A

⦾ NaX + H2SO4 → NaHSO4 + HX (1)

36
Q

What can happen next? (after the halide’s initial reaction with concentrated sulfuric acid) (2 marks)

A

⦾ Some halide ions strong enough reducing agents (1)

⦾ (so) can reduce H2SO4 to H2O and SO2 (1)

37
Q

What does the second reaction of a halide with concentrated sulfuric acid depend on? (1 mark)

A

⦾ If halide ion’s strong enough reducing agent (1)

38
Q

What is the general equation for the second reaction of halides with concentrated sulfuric acid?

  • Write an equation using ‘X’ to represent halide (1 mark)
  • (Use first reaction product)
  • Balance (1 mark)
A

⦾ 2HX + H2SO4 → X2 + SO2 + H2O (2 marks)

39
Q

Which is oxidised or reduced from the halide and the sulfuric acid? (2 marks)

A

⦾ Halide - Oxidised (1)

⦾ Sulfuric acid - Reduced (1)

40
Q

What are the 2 half equations for the halide and sulfuric acid? (2 marks)

⦾ 2HX + H2SO4 → X2 + SO2 + H2O

A

⦾ Halide: 2X-(g) → X2(s) + 2e- (oxidised) (1)

⦾ Sulfuric acid: H2SO4 + 2H+ + 2e- → SO2 + 2H2O (reduced) (1)

41
Q

Iodide is a very strong reducing agent.

What is it able to reduce the SO2 product to? (1 mark)

A

⦾ H2S or S (1)

42
Q

What is equation for the reaction of Sodium Fluoride with sulfuric acid? (1 mark)

A

⦾ NaF(s) + H2SO4(l) → NaHSO4(s) + HF(g) (1)

43
Q

What is the equation for the reaction of Sodium Chloride with sulfuric acid? (1 mark)

A

⦾ NaCl(s) + H2SO4(l) → NaHSO4(s) + HCl(g) (1)

44
Q

What can be observed in the reaction of NaF or NaCl with sulfuric acid? (1 mark)

A

⦾ Misty fumes (1)

45
Q

Explain why NaF or NaCl’s reaction with sulfuric acid stops there? (1 mark)

A

⦾ Neither strong enough reducing agents to reduce H2SO4 (1)

46
Q
  1. Why are these not redox reactions? (1 mark)
  2. What are the oxidation states of the halide and sulfur? (1 mark)

⦾ NaF(s) + H2SO4(l) → NaHSO4(s) + HF(g) (1)
⦾ NaCl(s) + H2SO4(l) → NaHSO4(s) + HCl(g) (1)

A
  1. Oxidation states of halide and sulfur stay same (1)

2. (-1 and +6) (1)

47
Q

What are the equations for the reaction of Sodium Bromide with sulfuric acid? (2 marks)

A

⦾ NaBr(s) + H2SO4 → NaHSO4(s) + HBr(g) (1)

⦾ 2HBr(aq) + H2SO4(l) → Br2(g) + SO2(g) + 2H2O(l) (1)

48
Q

What can be observed in the first reaction of NaBr with sulfuric acid? (1 mark)

A

⦾ misty fumes (1)

49
Q

What does the reaction below produce? (2 marks)

⦾ 2HBr(aq) + H2SO4(l) → Br2(g) + SO2(g) + 2H2O(l)

A

⦾ Choking fumes - SO2 (1)

⦾ Orange fumes - Br2 (1)

50
Q

What are the equations for the reaction of Sodium Iodide with sulfuric acid? (3 marks)

A

⦾ NaI(s) + H2SO4(l) → NaHSO4(s) + HI(g) (1)

⦾ 2HI + H2SO4 → I2(s) + SO2(g) + 2H2O(l) (1)

⦾ 6HI + SO2(g) → H2S(g) + 3I2(s) + 2H2O(l) (1)

51
Q

What can be observed in the reaction of Sodium Iodide with sulfuric acid? (1 mark)

A

⦾ H2S fumes (toxic + eggy) (1)

⦾ solid grey iodine (1)

52
Q

What colour are halide? (1 mark)

A

⦾ Colourless (1)

53
Q

What test can be used to test for halides?

A

⦾ Silver Nitrate test

54
Q

What is the method for testing for halides with silver nitrate? (3 marks)

A
  1. Add dilute nitric acid (1)
  2. few drops silver nitrate solution (AgNO3(aq)) (1)
  3. silver halide prec. forms (1)
55
Q

Why was dilute nitric acid added? (1 mark)

A

⦾ Remove ions that may interfere with test (1)

56
Q

Why can’t you use hydrochloric acid instead of nitric acid when testing for halides? (1 mark)

A

⦾ Silver nitrate would react with Cl- ions (from HCl) (1)

57
Q

What is the general ionic equation for the reaction of silver nitrate with a halide? (1 mark)

(Use X as the halide)

A

⦾ Ag+(aq) + X-(aq) → AgX(s) (1)

58
Q

What do the following ions produce when tested for with the silver nitrate? (4 marks)

⦾ Fluoride ⦾ Chloride ⦾ Bromide ⦾ Iodide

A

⦾ Fluoride - No prec. (1)
⦾ Chloride - white prec. (1)
⦾ Bromide - cream prec. (1)
⦾ Iodide - yellow prec. (1)

59
Q

Why do Fluroide produce no precipitate?

A

⦾ Silver fluoride soluble in water (1)

60
Q

What other test can be taken following the silver nitrate test with halides? (2 marks)

A

⦾ Add ammonia solution (1)

⦾ (as) each silver halide has different solubilty in ammonia (1)

61
Q

What does the Ammonia solution test result in for the:

⦾ Chloride prec. (1 mark)
⦾ Bromide prec. (1 mark)
⦾ Iodide prec. (1 mark)

A

⦾ Cl- prec. dissolves in dilute NH3(aq) (1)
⦾ Br- prec. dissolves in conc. NH3(aq) (1)
⦾ I- prec. insoluble in conc. NH3(aq) (1)

CHEMISTRY (AS) (24 decks)

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