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A Level Chemistry > Elements of Group 7 - Inorganic chemistry > Flashcards

Elements of Group 7 - Inorganic chemistry Flashcards

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1
Q

What is fluorine’s appearance at room temperature?

A

Pale yellow gas

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2
Q

What is colour is fluorine in aqueous solution?

A

Colourless

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3
Q

What is the colour of fluorine in hydrocarbon solution (e.g. hexane)?

A

Colourless

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4
Q

What is chlorine’s appearance at room temperature?

A

Pale green gas

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5
Q

What colour is chlorine in aqueous solution?

A

Pale green

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6
Q

What colour is chlorine in hydrocarbon solution (e.g. hexane)?

A

Pale green

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7
Q

What is bromine’s appearance at room temperature?

A

Dark red/brown liquid

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8
Q

What colour is bromine in aqueous solution?

A

Orange

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9
Q

What colour is bromine in hydrocarbon solution (e.g. hexane)?

A

Orange

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10
Q

What is iodine’s appearance at room temperature?

A

Grey (shiny) solid

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11
Q

What colour is iodine in aqueous solution?

A

Brown

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12
Q

What colour is iodine in hydrocarbon solution (e.g. hexane)?

A

Purple

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13
Q

What colour is iodine in the vapour state?

A

Violet

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14
Q

How do the boiling points of the halogens change down the group and why does this change occur?

A

Melting and boiling points increase down the group. This is because the number of electrons in the molecule increases down the group and so strength of London dispersion forces increases, meaning more energy is required to separate the molecules from each other and so the melting point and boiling point increase.

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15
Q

How does the first ionisation energy of the halogens change down the group and why does this change occur?

A

It decreases/becomes less endothermic down the group because atomic radius increases, as does the number of shielding shells, outweighing the increase in nuclear charge, so the force of attraction on the outer electrons is less, and so they are lost more easily.

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16
Q

How does the first electron affinity of the halogens change down the group and why does this change occur?

A

The first electron affinity decreases down the group/ becomes less endothermic as the incoming electron is further from the nucleus and has a greater shielding effect between it and the nucleus, and so the attraction for the incoming electron decreases down the group

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17
Q

How do the bond energies of the halogens change down the group?

A

Generally, bond energies decrease as the bond lengths increase. The atoms increase in size and so overlap between orbitals forming the bonds is less effective, causing the sigma bond to become longer and weaker.
The F-F bond is anomalous as the extremely short bond length brings the lone pairs of electrons closer together and the repulsion between them then causes the bond to be longer

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18
Q

Reaction of halogens with metals

A

Cl2 + Na -> 2NaCl

X2 + 2e- -> 2X-

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19
Q

Reaction of chlorine and hydrogen

A

H2 + Cl2 -> 2HCl
(Hydrogen loses 2 electrons and is oxidised, chlorine gains 2 and is reduced)
When a mixture is kept in the dark, nothing happens, but when it is illuminated then the gas explodes

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20
Q

Reaction of bromine and hydrogen

A

H2 + Br2 -> 2HBr

Requires 300°C and a platinum catalyst

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21
Q

Reaction of iodine and hydrogen

A

H2 +I2 -> 2HI

Requires 300°C and a platinum catalyst and still only reacts slowly and partially

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22
Q

Reaction of fluorine and hydrogen

A

H2 +F2 -> 2HF

Reacts explosively

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23
Q

Reaction as chlorine dissolves in water

A

Cl2 +H2O -> HCl + HOCl

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24
Q

What is a disproportionation reaction?

A

A reaction in which the same element (in the same species) is simultaneously oxidised and reduced

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25
Q

How does the reaction of chlorine and water explain the bleaching properties of chlorine water?

A

ClO- ions are the main ingredient in bleach as they kill bacteria

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26
Q

Dissociation of HCl (from chlorine dissolving in water)

A

HCl + H2O -> H3O+ + Cl -

Hydrochloric acid is fully dissociated into ions

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27
Q

Dissociation of HOCl (from chlorine dissolving in water)

A

HOCl + H2O -> H3O+ + OCl-

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28
Q

Ionisation of strong acid

A

Complete ionisation (more H+)

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29
Q

Ionisation of weak acid

A

Partial ionisation (less H+)

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30
Q

Decomposition of chloric acid (HOCl)

A

2HOCl -> 2HCl + O2

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31
Q

Chemical test for chlorine

A

Cl2 + H2O -> HCl + HOCl
Rapidly bleaches damp blue litmus paper (paper needs to be damp in order for chlorine to react with the water to form ClO-)

32
Q

Chemical test for bromine (litmus paper)

A

Br2 +H2O -> HBr + HOBr

Brown fuming liquid/gas that slowly bleaches damp blue litmus paper

33
Q

Chemical test for bromine (excess potassium iodide)

A

Br2 + 2I- -> I2 + 2Br-
Add bromine to potassium iodide, the colourless solution turns deep red-brown. Iodine is liberated, then reacts with excess I- ions to form red-brown I^3- ion

34
Q

Chemical test for iodine

A

Turns blue-black with starch solution

35
Q

Oxidation states of chlorine

A

-1 (Cl-), 0 (Cl2), +1 (ClO-), +3 (ClO2-), +5 (ClO3-), +7 (ClO4-)

36
Q

Reaction of chlorine with cold (15°C), dilute alkali

A

Cl2 + 2NaOH -> NaOCl + NaCl + H2O

- disproportionation

37
Q

Reaction when NaOCl (solution formed in reaction of chlorine with cold alkali) is warmed to 60°C

A

3OCl- -> 2Cl- + ClO3-

- disproportionation

38
Q

Reaction of chlorine with hot (60°C), dilute alkali

A

3Cl2 + 6NaOH -> NaClO3 + 5NaCl + 3H2O

39
Q

Uses of chlorates

A 
Sodium chlorate (I) - used in household bleach (hypochlorite bleach)
Sodium chlorate (V) - used in weed killer
40
Q

Heating solid potassium chlorate (V)

A

4KClO3 -> KCl + 3KClO4
- disproportionation
KClO4 -> KCl +O2
- chlorine is reduced

41
Q

Reaction of bromine with alkalis

A

Behaves like chlorine but disproportionates more easily, so both reactions occur rapidly at 15°C and temperature needs to be lowered to 0°C to stop the decomposition of the BrO- ion

42
Q

Reaction of iodine with alkalis

A

Behaves like chlorine but disproportionates more easily, so both reactions occur rapidly even at 0°C so it is difficult to separate the different products

43
Q

Test for chloride ions

A

Add silver nitrate and dilute nitric acid (to prevent precipitation of other ions such as carbonate) and a white precipitate will form that is soluble in both dilute and concentrated aqueous ammonia

44
Q

Test for bromide ions

A

Add silver nitrate and dilute nitric acid (to prevent precipitation of other ions such as carbonate) and a cream precipitate will form that is insoluble in dilute aqueous ammonia but soluble in concentrated aqueous ammonia

45
Q

Test for iodide ions

A

Add silver nitrate and dilute nitric acid (to prevent precipitation of other ions such as carbonate) and a yellow precipitate will form that is insoluble in both dilute and concentrated aqueous ammonia

46
Q

Effect of light on silver halides

A

Decomposes to form metallic silver in visible light which is used in things like black and white photography

47
Q

Colours of the solutions when bromide solution is mixed with chlorine water

A

Aqueous solution turns orange

Hexane layer turns orange

48
Q

Colours of the solutions when iodide solution is mixed with chlorine water

A

Aqueous solution turns brown

Hexane layer turns purple

49
Q

Reaction of sodium chloride and concentrated sulfuric acid

A

NaCl (s) + H2SO4 (aq) -> HCl (g) + NaHSO4 (aq)

The HCl causes steamy fumes and fizzing as it reacts with water in the air

50
Q

Test for hydrogen chloride

A

HCl + NH3 -> NH4Cl (solid - smoke)

Put near stopper of ammonia etc to form a white smoke

51
Q

Reaction of chlorine and bromide ions

A

Cl2 + 2Br- -> 2Cl- + Br2
(g) (aq) (aq) (aq)
Brown colour of liberated bromine can be seen

52
Q

Reaction of chlorine and iodide ions

A

Cl2 + 2I- -> 2Cl- + I2
(g) (aq) (aq) (aq)
Either a brown solution of iodine or a dark grey precipitate of iodine will be seen

53
Q

Reaction of bromine and iodide ions

A

Br2 + 2I- -> 2Br + I2

aq) (aq) (aq) (aq

54
Q

Why is hexane added when testing for halide ions using other halogens?

A

It makes the reaction easier to see. Hexane is immiscible with water and bromine and iodine turn the hexane layer very different colours and they are more soluble in hexane than in water

55
Q

Reaction of sodium bromide and concentrated sulfuric acid (full equations)

A

1) NaBr + H2SO4 -> HBr + NaHSO4
2) 2HBr (g) + H2SO4 (aq) -> Br2 (l) + SO2 (g) + 2H2O (l)
Gaseous HBr is a better reducing agent than HCland so it reduces the sulfuric acid to sulfur dioxide (but it is a colourless gas so cannot be seen)

56
Q

Reaction of bromine and concentrated sulfuric acid (half equations for 2nd reaction)

A

2Br- - 2e- -> Br2
H2SO4 + 2H+ + 2e- -> SO2 + H2O
Sulfur receives 2 electrons from bromine, which is something chlorine and fluorine cannot give

57
Q

Reaction of sodium iodide and concentrated sulfuric acid - 1st reaction

A

1) NaI + H2SO4 -> HI + NaHSO4

58
Q

Reaction of sodium iodide and concentrated sulfuric acid - 2nd reaction

A

2) 2HI + H2SO4 -> SO2 + 2H2O + I2

59
Q

Reaction of sodium iodide and concentrated sulfuric acid - 3rd reaction

A

3) 6HI + H2SO4 -> 3I2 + S + 4H2O

60
Q

Reaction of sodium iodide and concentrated sulfuric acid - 4th reaction

A

4) 8HI + H2SO4 -> 4I2 + H2S + 4H2O

61
Q

Production of hydrogen halides using ‘syrupy’ phosphoric acid

A

H3PO4 + 3NaI -> Na3PO4 + 3HI

62
Q

Reactions of hydrogen halides with water

A

HX (g) + H2O (l) -> H3O+ + X-

H3O+ ion makes the solution formed acidic

63
Q

Why does HF only form a weak acid in water?

A

H-F bond is shorter and much stronger so it does not ionise fully

64
Q

What apparatus would be used to prepare hydrochloric acid from sodium chloride?

A

Funnel, dropping funnel, Büchner flask, delivery tube, round-bottomed flask (HCl is more dense than air, so it will go straight into the flask from the delivery tube)

65
Q

Trends of group 7: Physical state at room temperaure

A

Fluorine - gas
Astatine - solid
London forces increase down group

66
Q

Trends of group 7: Radioactivity

A

Fluorine - no

Astatine - yes

67
Q

Trends of group 7: Ionisation energy

A

Fluorine - high

Astatine - low

68
Q

Trends of group 7: Electron affinity

A

Fluorine - very exothermic

Astatine - less exothermic

69
Q

Trends of group 7: Electronegativity

A

Fluorine - high

Astatine - low

70
Q

Trends of group 7: Oxidation states

A

Fluorine - one (-1)

Astatine - many (-1, +1, +3, +5, +7)

71
Q

Trends of group 7: Compounds with other halides

A

Fluorine - does form

Astatine - does form

72
Q

Trends of group 7: Reactions with metals

A

Fluorine - yes, reacts vigorously

Astatine - Reacts slowly, if at all

73
Q

Trends of group 7: Reactions with H2

A

Fluorine - yes, vigorous, exothermic reaction

Astatine - reacts slowly

74
Q

Trends of group 7: Reactions with non-metals

A

Fluorine - yes, reacts vigorously

Astatine - reacts slowly

75
Q

Trends of group 7: Reaction with water

A

Fluorine - yes, to produce HF

Astatine - yes, to produce HAt and HOAt

76
Q

Trends of group 7: Reactions of alkali

A

Fluorine - no reaction, NaOF cannot form as fluorine cannot have a +1 oxidation state
Astatine - cold alkali: At2 + 2NaOH -> NaAt + NaOAt +H2O (disproportionation), hot alkali: 3At2 + 6NaOH -> NaAtO3 + 5NaAt + 3H2O

A Level Chemistry (25 decks)

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