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Chem A-level > 3.2.3 Group 7 Knowledge > Flashcards

3.2.3 Group 7 Knowledge Flashcards

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1
Q

explain the trend in atomic radius down group 7

A
  • atomic radius increases down the group
  • increased number of electron shells
  • electrons repel each other
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2
Q

explain the trend in oxidising ability down group 7

A
  • oxidising ability decreases down the group
  • larger atomic radius and increased shielding (offsetting the effect of the greater nuclear charge)
  • weaker attraction between nucleus and incoming electron
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3
Q

describe what occurs in a halogen displacement reaction

A

a halogen higher in the group can oxidise the ions of one lower down and displace it from its compound

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4
Q

what element is an exception from halogen displacement reactions?

A

Fluorine

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5
Q

why is fluorine an exception from halogen displacement reactions?

A
  • it is too strong an oxidising agent
  • Fluorine oxidises water to oxygen and so it is impossible to do simple solution reactions with it.
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6
Q

explain the trend in reducing ability down group 7

A
  • reducing strength increases down group
  • ionic radius increases
  • there is a weaker attraction between the outermost electron and nucleus
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7
Q

what is this type of reaction: Fluorine + Sulfuric acid

A

acid-base reaction

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8
Q

why does fluorine undergo an acid-base reaction with sulfuric acid?

A

fluorine is too weak as a reducing agent to reduce sulfuric acid, so it undergoes an acid-base reaction instead

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9
Q

what is the word equation for the reaction between fluorine and sulfuric acid?

A

Sodium Fluoride + Sulfuric acid ⇒ Sodium Bisulphate + Hydrogen Fluoride

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10
Q

what is the symbol equation for the reaction between fluorine and sulfuric acid?

A

NaCl + H₂SO₄ ⇒ NaHSO₄ + HF

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11
Q

what is the half equation for the reaction between fluorine and sulfuric acid?

A

H⁺ + F⁻ ⇒ HF

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12
Q

what is the observation for the reaction between fluorine and sulfuric acid?

A

misty/steamy fumes of hydrogen fluoride

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13
Q

what is this type of reaction: chlorine + Sulfuric acid

A

acid-base reaction

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14
Q

why does chlorine undergo an acid-base reaction with sulfuric acid?

A

chlorine is too weak as a reducing agent to reduce sulfuric acid, so it undergoes an acid-base reaction instead

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15
Q

what is the word equation for the reaction between chlorine and sulfuric acid?

A

Sodium Chloride + Sulfuric acid ⇒ Sodium Bisulphate + Hydrogen Chloride

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16
Q

what is the symbol equation for the reaction between chlorine and sulfuric acid?

A

NaCl + H₂SO₄ ⇒ NaHSO₄ + HCl

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17
Q

what is the half equation for the reaction between chlorine and sulfuric acid?

A

H⁺ + Cl⁻ ⇒ HCl

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18
Q

what is the observation for the reaction between chlorine and sulfuric acid?

A

misty/steamy fumes of hydrogen chloride gas

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19
Q

what type of reaction occurs between bromine and sulfuric acid?

A

acid-base or redox

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20
Q

what is the word equation for the acid-base reaction between bromine and sulfuric acid?

A

Sodium Bromide + Sulfuric Acid ⇒ Sodium Bisulphate + Hydrogen Bromide

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21
Q

what is the word equation for the redox reaction between bromine and sulfuric acid?

A

Sodium Bromide + Sulfuric Acid ⇒ Sulfur Dioxide + Water + Bromine

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22
Q

what is the symbol equation for the acid-base reaction between bromine and sulfuric acid?

A

NaBr + H₂SO₄ ⇒ NaHSO₄ + HBr

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23
Q

what is the symbol equation for the redox reaction between bromine and sulfuric acid?

A

H2SO4 + 2H+ + 2Br- ⇒ Br2 + SO2 + 2H2O

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24
Q

what is the half equation for the acid-base reaction between bromine and sulfuric acid?

A

H⁺ + Br⁻ ⇒ HBr

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25
Q

what are the half equations for the redox reaction between bromine and sulfuric acid?

A
  • 2Br⁻ ⇒ Br₂ + 2e⁻
  • 2e⁻ + 2H⁺ + H₂SO₄ ⇒ SO₂ + 2H₂O
26
Q

what is the observation for the acid-base reaction between bromine and sulfuric acid?

A

misty/steamy fumes of hydrogen bromide

27
Q

what is the observation for the redox reaction between bromine and sulfuric acid?

A

brown fumes and acidic/toxic gas

28
Q

what type of reaction occurs between iodine and sulfuric acid?

A

acid-base or redox

29
Q

what is the word equation for the acid-base reaction between iodine and sulfuric acid?

A

Sodium Iodide + Sulfuric Acid ⇒ Sodium Bisulphate + Hydrogen Iodide

30
Q

what is the symbol equation for the acid-base reaction between iodine and sulfuric acid?

A

NaI + H₂SO₄ ⇒ NaHSO₄ + HI

31
Q

what is the half equation for the acid-base reaction between iodine and sulfuric acid?

A

H⁺ + I⁻ ⇒ HI

31
Q

what is the observation for the acid-base reaction between iodine and sulfuric acid?

A

misty/steamy fumes of hydrogen iodide

32
Q

what is the word equation for the first redox reaction between iodine and sulfuric acid?

A

Sodium Iodide + Sulfuric Acid ⇒ Sulfur Dioxide + Water + Iodine

33
Q

what is the word equation for the second redox reaction between iodine and sulfuric acid?

A

Sodium Iodide + Sulfuric Acid ⇒ Sulfur + Water + Iodine

34
Q

what is the word equation for the third redox reaction between iodine and sulfuric acid?

A

Sodium Iodide + Sulfuric Acid ⇒ Hydrogen Sulfide + Water + Iodine

35
Q

what is the symbol equation for the first redox reaction between iodine and sulfuric acid?

A

2H+ + 2I- + H2SO4 ⇒ SO2 + 2H2O + I2

36
Q

what is the symbol equation for the second redox reaction between iodine and sulfuric acid?

A

6H+ + 6I- + H2SO4 ⇒ S + 4H2O + 3I2

37
Q

what is the symbol equation for the third redox reaction between iodine and sulfuric acid?

A

8H+ + 8I- + H2SO4 ⇒ H2S + 4H2O + 4I2

38
Q

what are the half equations for the first redox reaction between iodine and sulfuric acid?

A
  • 2I⁻ ⇒ I₂ + 2e⁻
  • 2e⁻ + 2H⁺ + H₂SO₄ ⇒ SO₂ + 2H₂O
39
Q

what are the half equations for the second redox reaction between iodine and sulfuric acid?

A
  • (2I⁻ ⇒ I₂ + 2e⁻) x3
  • 6e⁻ + 6H⁺ + H₂SO₄ ⇒ S + 4H₂O
40
Q

what are the half equations for the third redox reaction between iodine and sulfuric acid?

A
  • (2I⁻ ⇒ I₂ + 2e⁻) x4
  • 8e⁻ + 8H⁺ + H₂SO₄ ⇒ H₂S + 4H₂O
41
Q

what are the observations for the third redox reaction between iodine and sulfuric acid?

A

forming hydrogen sulfide: black solid, bad egg smell

42
Q

what are the half equations for the second redox reaction between iodine and sulfuric acid?

A

forming sulfur: black and yellow solids

43
Q

what are the half equations for the first redox reaction between iodine and sulfuric acid?

A

forming sulfur dioxide: black solid, acidic gas

44
Q

describe the process of the halide test

A
  1. dissolve sample in water (if not already an aqueous solution)
  2. Add HNO₃
  3. Add AgNO₃ (aq) solution
  4. Add dilute NH₃ to the sample
  5. Add concentrated NH₃ to the sample
45
Q

why is HNO₃ added before AgNO₃ in the halide test?

A

used to remove any possible CO₃²⁻ impurities which would give a false positive

46
Q

what acids should not be used before AgNO₃ in the halide test? and why?

A

HCl (as it contains a halide) or H₂SO₄ (it will undergo redox or acid-base reactions)

47
Q

what is a positive result for fluoride in the halide test?

A

no ppt

48
Q

what is a positive result for chloride in the halide test?

A

white ppt which dissolves in dilute ammonia solution

49
Q

what is a positive result for bromide in the halide test?

A

cream ppt which dissolves in concentrated ammonia solution

50
Q

what is a positive result for iodide in the halide test?

A

yellow ppt which does not dissolve in any ammonia solution

51
Q

what is the fluoride precipitate formed in the halide test?

A

Ag⁺ (aq) + F⁻ (aq) ⇒ AgF (aq)

52
Q

what is the chloride precipitate formed in the halide test?

A

Ag⁺ (aq) + Cl⁻ (aq) ⇒ AgCl (s) [white]

53
Q

what is the bromide precipitate formed in the halide test?

A

Ag⁺ (aq) + Br⁻ (aq) ⇒ AgBr (s) [cream]

54
Q

what is the iodide precipitate formed in the halide test?

A

Ag⁺ (aq) + I⁻ (aq) ⇒ AgI (s) [yellow]

55
Q

give the half equation for the reaction between ammonia and a silver halide ppt in the halide test

A

Ag⁺ (aq) + 2NH₃ (aq) ⇐⇒ [Ag(NH₃)₂]⁺ (aq)

56
Q

why is chlorine added to water?

A

it sterilises it by killing bacteria

57
Q

why must the chlorine added to water be a low concentration?

A

chlorine is toxic

58
Q

give the symbol equation for the reaction between chlorine and water

A

Cl₂ + H₂O ⇄ HCl + HClO

59
Q

what type of reaction is the reaction between chlorine and water

A

disproportionation [Cl₂ is reduced to HCl (oxidation state change: 0 to -1)
Cl₂ is oxidised to HClO (hypochlorous acid) (oxidation state change: 0 to +1)]

Chem A-level (10 decks)

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