ES1: Halogens Flashcards

1
Q

What group are the halogens in?

A

Group 7

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2
Q

What block are the halogens in?

A

P block

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3
Q

What electronic configuration do all the halogens have?

A

ns2np5

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4
Q

Why are halogens not found as elements on their own?

A

Too reactive

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5
Q

What three ways do halogens exist naturally?

A
  • Exist as ionic compounds
  • Exist as separate covalently bonded diatomic molecules
  • By sharing an electron from another metal atom
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6
Q

What’s fluorine’s appearance at room temperature?

A

Pale yellow gas

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7
Q

What’s chlorine’s appearance at room temperature?

A

Green gas

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8
Q

What’s bromine’s appearance at room temperature?

A

Dark red liquid

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9
Q

What’s iodine’s appearance at room temperature?

A

Shiny grey/black solid

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10
Q

What’s chlorine’s appearance in water?

A

Virtually colourless

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11
Q

What’s bromine’s appearance in water?

A

Yellow/orange

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12
Q

What’s iodine’s appearance in water?

A

Brown

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13
Q

What’s chlorine’s appearance in hexane?

A

Virtually colourless

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14
Q

What’s bromine’s appearance in hexane?

A

Orange/red

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15
Q

What’s iodine’s appearance in hexane?

A

Pink/violet

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16
Q

How does the reducing ability of the halogens change down the group?

A

Increases

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17
Q

How does the oxidising ability of the halogens change down the group?

A

Decreases

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18
Q

Why does the reducing ability of the halogens increase down the group?(4)

A
  • Increased atomic radius
  • Increased electron shells between the nucleus and the outer shell of electrons
  • More electron shielding means less of an attraction between the nucleus and the outer shell
  • Harder to attract an electron towards it
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19
Q

How does the volatility of the halogens change down the group?

A

Decreases

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20
Q

What is volatility?

A

The ease with which an element evaporates into a gas

21
Q

Why does the volatility of the halogens decrease down the group? (4)

A
  • Increased atomic radius: larger molecule
  • Larger electron cloud
  • Stronger instantaneous dipole-induced dipole bonds
  • Harder to break these strong intermolecular bonds to change state into a gas
22
Q

How does the electronegativity of the halogens change down the group?

A

Decreases

23
Q

How soluble are halogens in water?

A

Low solubility

24
Q

Why do halogens have a low solubility in water?

A

They form covalent and non polar molecules

25
Q

What substances do halogens dissolve more easily in than water?

A

Organic solvents e.g hexane

26
Q

Why is it useful to dissolve halogens in hexane?

A

They have more distinctive colours when dissolved in hexane so are easier to tell apart

27
Q

How do halogens react?

A

By gaining an electron (being reduced) and oxidising another substance

28
Q

Are halogens stronger oxidising agents or reducing agents?

A

Oxidising agents

29
Q

What is the general formula for a halogen reacting?

A

X + e- ===> X-

30
Q

What happens in a displacement reaction with halogens?

A

A more reactive halogen will displace a less reactive halide in a solution

31
Q

Give the formula for a displacement reaction with chlorine and potassium iodide.

A

Cl2 (aq) + 2KI(aq) ====> 2KCl (aq) + I2 (aq)

32
Q

What colour change would you observe in a displacement reaction with chlorine and potassium iodide?

A

The solution would turn from pale green to brown

33
Q

How could a clearer colour change be observed in a displacement reaction?

A

By shaking the solution with hexane

34
Q

What does chlorine do in a displacement reaction with chlorine and potassium iodide? Give the half equation.

A
  • Chlorine displaces iodine and gets reduced

- Cl2 + 2e- ====> 2Cl-

35
Q

What does iodine do in a displacement reaction with chlorine and potassium iodide? Give the half equation.

A
  • Iodine is displaced by chlorine and gets oxidised

- 2I-====> I2 + 2e-

36
Q

How do you write an ionic equation?

A

Cancel out the unchanged ions

37
Q

What reacts with halide ions to form a precipitate?

A

Silver ions

38
Q

Give the general formula of a precipitation reaction with silver ions and halide ions.

A

Ag+ (aq) + X- (aq) ====> AgX(s)

39
Q

How do you test for halides? (2)

A
  • Add dilute nitric acid

- Add silver nitrate solution

40
Q

Why do you add dilute nitric acid when testing for halides?

A

To remove other ions that could interfere in the reaction

41
Q

What colour precipitate forms with fluorine after reacting with silver ions?

A

No precipitate forms (trick question :-P)

42
Q

What colour precipitate forms with chlorine after reacting with silver ions?

A

White

43
Q

What colour precipitate forms with bromine after reacting with silver ions?

A

Cream

44
Q

What colour precipitate forms with iodine after reacting with silver ions?

A

Yellow

45
Q

How do you further distinguish between the silver halides?

A

By adding ammonia solutions of different concentrations

46
Q

What happens when you add ammonia solution to AgCl?

A

Dissolves in dilute ammonia solution to form a colourless solution

47
Q

What happens when you add ammonia solution to AgBr? (2)

A
  • Does not dissolve in dilute ammonia solution

- Dissolves in concentrated ammonia solution to form a colourless solution

48
Q

What happens when you add ammonia solution to AgI?

A

Never dissolves