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AQA A-Level Chemistry > 2.3 Group 7 > Flashcards

2.3 Group 7 Flashcards

1
Q

Trend in atomic radius down group 7

A

Increases
- Main shells and shielding increases
- Weaker nuclear attraction to the outer electrons

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2
Q

Why is the radius of halide ions greater than halogen atoms?

A
  • Ions have more electrons
  • Same number of protons
  • Weaker nuclear attraction in ions
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3
Q

Trend in boiling point down group 7

A

Increases (halogens become less volatile)
- Larger molecules, more electrons
- Stronger van der Waals forces
- More energy needed

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4
Q

Trend in electronegativity down group 7

A

Decreases
- More main shells and shielding
- Less attraction between shared pair and nucleus

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5
Q

Trend in first ionisation energy down group 7

A

Decreases
- More main shells and shielding
- Less nuclear attraction to outer electron
- Less energy needed to remove it

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6
Q

Colour of chlorine

A

Green

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7
Q

Colour of bromine

A

Red-brown

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8
Q

Colour of Iodine

A

Black

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9
Q

State of chlorine (at room temperature)

A

Gas

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10
Q

State of bromine (at room temperature)

A

Liquid

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11
Q

Colour of chlorine in aqueous solution

A

Pale green

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12
Q

Colour of bromine in aqueous solution

A

Orange

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13
Q

Colour of iodine in aqueous solution

A

Brown

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14
Q

Colour of chlorine in cyclohexane

A

Pale green

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15
Q

Colour of bromine in cyclohexane

A

Orange

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16
Q

Colour of iodine in cyclohexane

A

Pink-purple

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17
Q

What are the best solvents for halogens?

A

Non-polar solvents like cyclohexane

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18
Q

Trend in solubility down group 7

A

Solubility decreases

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19
Q

Are halogens oxidising agents or reducing agents?

A

Oxidising agents (they accept electrons to form halide ions)

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20
Q

Trend in oxidising power down group 7

A

Decreases
- More main shells and shielding
- Less nuclear attraction to electron being accepted
- Less ability to gain electrons

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21
Q

Disproportionation

A

A redox reaction in which the same element is both oxidised and reduced

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22
Q

What is formed when chlorine reacts with water?

A

HCl + HClO (HClO decomposes in sunlight to form HCl and O₂)

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23
Q

HClO

A

Chloric (I) acid

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24
Q

Colour change with litmus paper/universal indicator: HClO

A

Indicator is bleached

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25
Q

Benefits and risks of using Cl₂ in water treatment

A

Benefit: Kills bacteria at non-toxic levels
Risk: Toxic in larger quantities

26
Q

How are sodium chloride, sodium chlorate(1) and water produced from Cl₂?

A

Reacting Cl₂ with cold dilute sodium hydroxide solution

27
Q

Uses of NaCl + NaClO + H₂O solution

A
  • As a bleach
  • To kill bacteria
28
Q

Test for halide ions

A
  • Make a solution of the test substance
  • Add dilute nitric acid (to remove other ions)
  • Add silver nitrate solution
29
Q

Positive test for Cl⁻

A

White precipitate forms (AgCl)

30
Q

Positive test for Br⁻

A

Cream precipitate forms (AgBr)

31
Q

Positive test for I⁻

A

Yellow precipitate forms (AgI)

32
Q

Why do F⁻ ions not form a precipitate with silver nitrate?

A

AgF is soluble in water

33
Q

Adding dilute ammonia solution to precipitate of AgCl

A

AgCl dissolves forming colourless solution

34
Q

Adding dilute ammonia solution to precipitate of AgBr

A

AgBr is insoluble - cream solid remains

35
Q

Adding dilute ammonia solution to precipitate of AgI

A

AgI is insoluble - yellow solid remains

36
Q

Adding conc. ammonia solution to precipitate of AgCl

A

AgCl dissolves forming a colourless solution

37
Q

Adding conc. ammonia solution to precipitate of AgBr

A

AgBr dissolves forming a colourless solution

38
Q

Adding conc. ammonia solution to precipitate of AgI

A

AgI is insoluble - yellow solid remains

39
Q

Test for a reducing agent (gasses)

A

Orange acidified potassium dichromate paper turns green

40
Q

Halides are ________ agents

A

Reducing
They lose electrons to form halogens

41
Q

____________ sulfuric acid reacts with _____ halide salts

A

Concentrated, solid

42
Q

H₂SO₄
Oxidation number of S

A

+6
Sulfuric (VI) acid

43
Q

SO₂
Oxidation number of S

A

+4
Sulfur (IV) oxide / Sulfur dioxide

44
Q

S
Oxidation number

45
Q

H₂S
Oxidation number of S

A

-2
Hydrogen sulfide

46
Q

Two reactions when a solid halide salt reacts with conc. sulfuric acid

A

1. Acid-base (H₂SO₄ acts as acid)
2. Redox (H₂SO₄ acts as an oxidising agent)

47
Q

Why does NaCl + H₂SO₄ not have a reduction or oxidation product?

A

Cl⁻ is not a strong enough reducing agent

48
Q

Products of NaCl + H₂SO₄

A
  • Acid-base: HCl + NaHSO₄
49
Q

Products of NaBr + H₂SO₄

A
  • Acid-base: HBr + NaHSO₄
  • Oxidation: Br₂
  • Reduction: SO₂
50
Q

Products of NaI + HSO₄

A
  • Acid-base: HI + H₂SO₄
  • Oxidation: I₂
  • Reduction: SO₂ + S + H₂S
51
Q

Halide redox reactions
Appearance/test for: HI / HBr / HCl gasses

A

Steamy white fumes

52
Q

Halide redox reactions
Appearance/test for: Br₂

A

Orange fumes

53
Q

Halide redox reactions
Appearance/test for: I₂

A

Black solid/purple vapour

54
Q

Halide redox reactions
Appearance/test for: SO₂

A
  • Colourless gas with a choking odor
  • Orange acidified potassium dichromate paper turns green
55
Q

Halide redox reactions
Appearance/test for: S

A

Yellow solid

56
Q

Halide redox reactions
Appearance/test for: H₂S

A
  • Colourless gas
  • Lead ethanoate paper, white → black
57
Q

Why does KI + H₂SO₄ have multiple reduction products?

A

I⁻ ions are very good reducing agents so they can reduce H₂SO₄ to its lowest oxidation number (as well as all the stages in between)

58
Q

Why do halide ions act as reducing agents?

A

They lose electrons to form halogens

59
Q

Trend in reducing power of the halides down group 7

A

Increases
- More main shells and shielding
- Nuclear attraction to outer electron decreases
- Electron is more easily lost

60
Q

Strongest group 7 oxidising agent

61
Q

Strongest group 7 reducing agent

62
Q

What kind of reaction is chlorine + water?

A

Reverseable

AQA A-Level Chemistry (13 decks)

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