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Chemistry > Group 7 > Flashcards

Group 7 Flashcards

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1
Q

How does reactivity change as you go down group 7?

A

reactivity decreases down the group as it is harder to attract an electron due to atomic radius increasing so attracting an electron is harder as the positive attraction of the nucleus is weakened by additional shielding

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2
Q

How does the atomic radius change as you go down group 7?

A

increases down the group due to additional electron shells

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3
Q

How does the first ionisation energy change down group 7?

A

generally decreases down the group due to a greater atomic radius and increased amount of shielding

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4
Q

What is the reaction of sodium fluoride and sulfuric acid?

A

NaF + H2SO4 -> NaHSO4 + HF

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5
Q

What is the reaction of sodium chloride with sulfuric acid?

A

NaCl + H2SO4 -> NaHSO4 + HCl

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6
Q

What is the reaction of sodium bromide with sulfuric acid?

A

NaBr + H2SO4 -> NaHSO4 + HBr

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7
Q

What is the reaction of hydrogen bromide with sulfuric acid?

A

2HBr + H2SO4 -> Br2 + SO2 + 2H2O

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8
Q

What is the reaction of sodium iodide with sulfuric acid?

A

NaI + H2SO4 -> NaHSO4 + HI

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9
Q

What is the reaction of hydrogen iodide with sulfuric acid?

A

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

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10
Q

What is the reaction of hydrogen iodide with sulfur dioxide?

A

6HI + SO2 -> H2S + 3I2 + 2H2O

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11
Q

At room temp. what is the physical appearance of fluorine?

A

a very pale yellow gas

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12
Q

At room temp. what is the physical appearance of chlorine?

A

a greenish gas

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13
Q

At room temp. what is the physical appearance of bromine?

A

orange/brown liquid which vaporises easily into an orange gas

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14
Q

At room temp. what is the physical appearance of iodine?

A

a black solid which vaporises on heating to a purple gas

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15
Q

Do the elements tend to get lighter or darker going down the group?

A

darker

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16
Q

Do the elements tend to get lighter or denser going down the group?

A

denser

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17
Q

What is electronegativity?

A

the ability of an atom to withdraw electron density from a covalent bond

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18
Q

What does electronegativity depend on?

A
  • a greater nuclear charge will withdraw electrons more strongly
  • a shorter atomic radius will also help withdraw electrons more strongly
  • the more shielding will however reduce the amount of electrons that can be withdrawn
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19
Q

What is the general trend of electronegativity as you go down group 7?

A

decreases

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20
Q

Are halogens polar or non-polar molecules?

A

non-polar

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21
Q

What are the only intermolecular forces existing between halogen molecules?

A

Van der Waals forces

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22
Q

The strength of the Van der Waals forces between halogen molecules is dependent on what?

A

the size of the molecule/how many electrons it has

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23
Q

What is the general trend in melting and boiling point as you go down the group (7)?

A

increases as Van der Waals forces increase

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24
Q

What state is fluorine at room temp.?

A

gas

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25
Q

What state is chlorine at room temp.?

A

gas

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26
Q

What state is bromine at room temp.?

A

liquid

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27
Q

What state is iodine at room temp.?

A

solid

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28
Q

Are halogens oxidising or reducing agents?

A

oxidising agents

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29
Q

What is the trend in oxidising power of halogens as you go down group 7?

A

decreases

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30
Q

During a halogen displacement reaction the halogen highest up group 7 should form what?

A

a halide ion

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31
Q

During a halogen displacement reaction, the halogen lowest down group 7 should form a what?

A

halogen molecule

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32
Q

Are halide ions oxidising or reducing agents?

A

reducing agents

33
Q

What is the trend in reducing power of halides as you go down group 7?

A

increases

34
Q

What is the equation of sodium fluoride reacting with sulfuric acid? (F- is not a powerful enough reducing agent so will undergo an acid-base reaction)

A

NaF(s) + H2SO4(aq) -> NaH2SO4(s) + HF(g)

35
Q

What are the observations of sodium fluoride reacting with sulfuric acid?

A
  • sodium hydrogen sulfate is the solid product formed
  • steamy fumes of hydrogen fluoride gas is released
36
Q

Is hydrogen fluoride gas safe?

A

it is extremely dangerous

37
Q

What is hydrogen fluoride gas used for?

A

to etch glass

38
Q

What is the equation of sodium chloride reacting with sulfuric acid? (Cl- is not a powerful enough reducing agent so will undergo an acid-base reaction)

A

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

39
Q

What are the observations of the reaction between sodium chloride and sulfuric acid?

A
  • sodium hydrogen sulfate is the solid product formed
  • steamy fumes of hydrogen chloride gas is released
40
Q

Is a bromide ion a good reducing agent?

A

yes

41
Q

How will bromide ions react with sulfuric acid?

A
  • initially it will undergo an acid-base reaction with H2SO4:
    NaBr(s) + H2SO4(aq) -> NaHSO4(s) + HBr(g)
  • the bromide ions in HBr will then react further, reducing sulfur:
    2H+ + H2SO4 + 2Br- -> SO2 + 2H2O + Br2
42
Q

What are the observations of sodium bromide reacting with sulfuric acid? (at the end)

A
  • an acidic gas forms
  • brown fumes of bromine gas appear
43
Q

Is I- a good reducing agent?

A

It is an excellent reducing agent

44
Q

What is the equation for the initial acid-base reaction of iodide ions with sulfuric acid?

A

NaI(s) + H2SO4(aq) -> NaHSO4(s) + HI(g)

45
Q

After an initial acid-base reaction of iodide ions with sulfuric acid, what are the three ways the iodide ions now in HI can react?

A

1, iodide ions can reduce the sulfur from (VI) in H2SO4 to (IV) in SO2(g)
2, iodide ions can reduce sulfur from (VI) in H2SO4 to (0) in S(s)
3, iodide ions can reduce sulfur from (VI) in H2SO4 to (-2) in H2S(g)

46
Q

What is the equation of iodide ions (from HI) reducing the sulfur from (+6) in H2SO4 to (+4) in SO2? And what are the observations?

A

2H+ + H2SO4 + 2I- -> SO2 + 2H2O + I2
an acidic gas forms and a black solid of iodine forms

47
Q

What is the equation of iodide ions (from HI) reducing sulfur from (+6) in H2SO4 to (0) in the element S? And what are the observations?

A

6H+ + H2SO4 + 6I- -> S + 4H2O + 3I2
Yellow solid sulfur produced and black solid of iodine forms

48
Q

What is the equation of iodide ions (from HI) reducing sulfur from (+6) in H2SO4 to (-2) in the H2S(g)? And what are the observations?

A

8H+ + H2SO4 + 8I- -> H2S + 4H2O + 4I2
Gas smelling of bad eggs and black solid of iodine forms

49
Q

What is the equation of silver ions reacting with fluoride ions?

A

Ag+(aq) + F-(aq) -> AgF(aq)

50
Q

When silver ions react with fluoride ions, what is the observation?

A

a clear and colourless solution

51
Q

What is the equation of silver ions reacting with chloride ions?

A

Ag+(aq) + Cl-(aq) -> AgCl(aq)

52
Q

When chloride ions react with silver ions, what is the observation?

A

a white precipitate

53
Q

What is the equation of silver ions reacting with bromide ions?

A

Ag+(aq) + Br-(aq) -> AgBr(aq)

54
Q

When silver ions react with bromide ions, what is the observation?

A

a cream precipitate

55
Q

What is the equation for the reaction of silver ions with iodide ions?

A

Ag+(aq) + I-(aq) -> AgI(aq)

56
Q

When silver ions react with iodide ions, what is the observation?

A

a yellow precipitate

57
Q

What are the steps if you have an unknown substance and wish to test for the presence of halide ions?

A

1, to the unknown sample, add a few drops of nitric acid (HNO3) - this is needed to remove any carbonate ions which may be present in the sample and can alter the results
2, add a few drops of silver nitrate solution (AgNO3) and use the observation to draw your conclusion

58
Q

What does no precipitate indicate in a test for halide ions?

A

no halides are present or fluoride is present

59
Q

What does a white precipitate indicate in a test for halide ions?

A

the presence of chloride ions

60
Q

What does a cream precipitate indicate in a test for halide ions?

A

the presence of bromide ions

61
Q

What does a yellow precipitate indicate in a test for halide ions?

A

the presence of iodide ions

62
Q

What reagent should you add if you want to confirm the results of the halide ions test?

A

ammonia

63
Q

What are the results when confirming halide ions presence with ammonia and what do they mean?

A
  • the white ppt. for chloride ions will dissolve easily in dilute ammonia
  • the cream ppt. for bromide ions won’t dissolve in dilute ammonia but will dissolve in conc. ammonia
  • the yellow ppt. for iodide ions is completely insoluble even in conc. ammonia
64
Q

If chlorine is a gas, can it dissolve in water?

A

Yes

65
Q

What is the hazard surrounding chlorine?

A

it is poisonous and can be extremely dangerous in high concentrations

66
Q

What are some common uses of chlorine and why?

A

used in the treatment of drinking water and swimming pools as in very low concentrations chlorine and its derivatives are perfectly safe for humans, but can kill bacteria

67
Q

When chlorine reacts with water, what products are formed?

A

chloric (I) acid and hydrochloric acid

68
Q

What is the equation for the reversible reaction between chlorine and water?

A

Cl2(g) + H2O(l) <-> HClO(aq) + HCl(aq)

69
Q

What is special about the reaction of chlorine with water?

A

It is a disproportionation reaction

70
Q

Why is the reaction of chlorine with water a disproportionation reaction?

A

the chlorine starts off in a zero oxidation state but gets reduced down to -1 in HCl and oxidised up to +1 in HClO at the same time

71
Q

When does the disproportionation reaction between chlorine and water occur and why is it useful?

A

when chlorine is used to treat drinking water as well as used to keep swimming pools clean - the chloric acid (HClO) is an oxidising agent and kills bacteria by oxidising them and HClO is also a bleach

72
Q

What is the reaction of chlorine with water in the presence of bright sunlight (UV light)? What is the colour change?

A

2Cl2(g) + 2H2O(l) -> 4HCl(aq) + O2(aq)
pale green (the chlorine) to colourless (the hydrochloric acid)

73
Q

Why is the reaction of chlorine with water in the presence of UV light a problem?

A

because of this reaction, chlorine is rapidly lost from outdoor swimming pools and so needs to be constantly added

74
Q

What is an alternative to direct chlorination of swimming pools?

A

add solid sodium chlorate (NaClO) or calcium chlorate (Ca(ClO)2) as these both dissolve in water to form chloric acid in a reversible reaction:
NaClO(s) + H2O(l) <-> Na+(aq) + OH- (aq) + HClO(aq)
In alkaline solution the equilibrium above moves to the left which means HClO is converted to ClO- ions and for this reason swimming pool water is kept slightly acidic

75
Q

When chlorine reacts with cold dilute sodium hydroxide, what products are formed?

A

sodium chlorate

76
Q

What is the equation for the reaction of chlorine with cold dilute sodium hydroxide?

A

Cl2(g) + 2NaOH(aq) -> NaClO(aq) + NaCl(aq) + H2O(l)

77
Q

What is sodium chlorate?

A

an oxidising agent and a component of household bleach

78
Q

Is the reaction of chlorine with cold dilute sodium hydroxide a disproportionation reaction?

A

yes

Chemistry (16 decks)

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