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Chemistry Year 12 > group 7 3.2.3 > Flashcards

group 7 3.2.3 Flashcards

1
Q

what colour does fluorine gas produce

A

Pale yellow gas

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2
Q

what colour is chlorine gas

A

Pale green gas

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3
Q

what’s the colour for bromine

A

a brown- orange liquid

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4
Q

what colour is iodine solid

A

greblack
solid

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5
Q

what’s the trend in boiling and melting point down g7

A

increases down the group
- molecules become larger so have more electrons and have larger van de waals forces
- as intermolecular forces gets larger more energy is needed to overcome the forces

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6
Q

what’s the trend in states from the top of the group to the bottom

A

gas at the top (F)
solid at the bottom (I)

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7
Q

what is electronegativity

A

the relative tendency of an atom in a molecule to attract electrons in a covalent bond to itself

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8
Q

what’s the trend in electronegativity down the group

A

Decreases
•The atomic radii increases due to increasing number of shells.
• The nucleus is less able to attract the bonding pair of electrons

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9
Q

as we go down the group are the halogens more or less oxidising

A

less oxidising

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10
Q

which halogen does chlorine displace

A

Both bromide and iodine ions

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11
Q

which halogen does bromide displace

A

iodide ions

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12
Q

which halogen will iodide displace

A

None

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13
Q

what’s the colour of chlorine solution

A

Colourless

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14
Q

what’s the colour of bromine solution

A

yellow solution

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15
Q

what’s the colour of iodine solution

A

brown solution

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16
Q

what’s the reaction and colour change when chlorine displaces potassium bromide solution

A

yellow solution is made , Cl has displaced Br
Cl2 + 2Br- => 2Cl- + Br2

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17
Q

what’s the reaction and colour change when chlorine displaces potassium iodide

A

brown solution , Cl has displaced I
Cl2(aq) + 2I- => 2Cl-(aq) + I2 (aq)

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18
Q

what’s the reaction and colour change when bromine displaces potassium iodide

A

brown solution , Br has displaced I
Br2 (aq) + 2I-(aq) => 2Br-(aq) + I2(aq)

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19
Q

what is a disproportionation reaction

A

An element simultaneously oxidises and reduces

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20
Q

what type of reaction is used to make bleach ( NaClO)

A

Disproportionation

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21
Q

what’s the reaction to make bleach

A

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

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22
Q

what are the uses of bleach

A
  • treating water
  • bleaching paper and fabrics
  • cleaning agents
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23
Q

why is chlorine added to water

A
  • to kill bacteria
  • used to treat drinking water and the water in swimming pools
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24
Q

why is chlorine added to water even though it’s toxic

A

the benefits to health of water treatment by chlorine outweigh its toxic effects

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25
what’s the reaction of chlorine and water
2Cl2 + 2H2O => 4HCl + O2
26
what’s the reaction of chlorine with water and sunlight
2Cl2(g)+ 2H2O(l) => 4H+(aq) +4Cl-(aq) + O2(g) + 4HCl
27
what are the advantages of chlorinating drinking water
- destroys microorganisms that cause disease - long lasting so reduces bacteria build up further down the supply - reduces the growth of algae that discolours water and gives it a bad taste and smell
28
what are the disadvantages of chlorinating drinking water
- chlorine gas is toxic and irritates the respiratory system - liquid chlorine causes severe chemical burns to the skin - chlorine can react with organic compounds present in the water to make chloroalkanes which link with causing cancer
29
what are two tests with halide ions
1) halide reactions with sulfuric acid 2) halide reactions with silver nitrate solution
30
Why are halide ions stronger reducing agents as we go down the group
• halide ions lose an electron in reactions - as we go down the group the ionic radius increases - the distance between the nucleus and outer electrons becomes larger are there is more shielding so the attractive force gets weaker . - the outer electron is lost more readily and this is why I- is a more powerful reducing agent than F-
31
what role does H2SO4 play in reacting with halide ions in acid base reactions
Proton donor
32
why doesn’t a redox reaction occur when H2SO4 reacts with fluoride and chloride ions
H2SO4 is not strong enough an oxidising reagent to oxidise the chloride and the fluoride ions . Only acid-base reactions occur
33
what is the acid base reaction of H2SO4 and NaF and the observation
NaF(s) + H2SO4(l) => NaHSO4(s) + HF(g) White steamy fumes of HF are evolved
34
what is the acid base reaction of H2SO4 and NaCl and the observation
NaCl(s) + H2SO4(l) => NaHSO4(s) + HCl(g) White steamy fumes of HCl are evolved
35
why is a redox reaction taken place with Bromide ions and h2so4
Br- ions are stronger reducing agents than Cl- and F- and after the initial acid - base reaction reduce the sulfur in H2SO4 from +6 to +4 in SO2
36
what is the reaction of H2SO4 and NaBr and the observation
2NaBr(s) + 2H2SO4 (l) => Na2SO4 (s) + SO2 + Br2 + 2H2O orange fumes
37
what is the oxidation half equation for bromine
2Br- => Br2 + 2e-
38
what is the oxidation half reaction for H2SO4
H2SO4 + 2H+ +2e- => SO2 + 2H2O
39
what’s the redox reaction of HBr (product from acid base reaction )reacting with H2SO4
2HBr + H2SO4 => Br2(g) + SO2(g) + 2H2O(l)
40
what are the observations of Bromide ions reacting with H2sO4
White steamy fumes of HBr are evolved Orange fumes of bromine are also evolved and a colourless acidic gas of SO2
41
why do redox reactions occur in the reaction of iodide ions and h2so4
Iodide ions are the strongest halide reducing agents . They can reduce sulfur from +6 to +4 in So2 to 0 in S to -2 In H2S
42
what are the reactions between NaI and H2SO4
Acid base reaction : 1) 2NaI(s) + 2H2SO4(l) => Na2SO4 + I2 + SO2 + 2H2O Redox reaction : 2) 2H+ + 2I- + H2SO4 => I2(s) + SO2(g) + 2H2O(l) 3) 6H+ + 6I- + H2SO4 => 3I2 + S(s) + 4H2O(l) 4) 8H+ + 8I- + H2SO4 => 4I2(s) + H2S(g) + 4H2O (l)
43
what is the oxidation half equation for Iodide
2I- => I2 + 2e-
44
what are the reduction half equations for H2SO4 for I-
1) H2SO4 + 2H+ + 2e- => SO2 + 2H2O 2) H2SO4 + 6H+ + 6e- => S + 4H2O 3) H2SO4 + 8H+ + 8e- => H2S + 4H2O
45
what is the role of H2SO4 in the acid base reactions with iodide
Role of an acid (proton donor)
46
what’s the role of h2So4 when in the three redox reactions with Iodide
Oxidising agent
47
what are the observations of h2So4 reacting with iodide ions
- white steamy fumes of HI evolved - Black solid and purple fumes of iodine are also evolved - A colourless acidic gas of SO2 - a yellow solid of sulfur - H2S , a gas with a bad egg smell
48
how do you test for halide ions
Add dilute nitric acid (HNO3) then silver nitrate solution ( AgNO3) . The colour of the precipitate will help you identify the halide ion
49
what’s the reaction and observation of chloride ions with AgNO3
Chlorides produce a white ppt Ag+ (aq) + Cl-(aq) => AgCl(s)
50
what’s the reaction and observation of bromide ions with AgNO3
Cream ppt Ag+(aq) + Br-(aq) => AgBr(s)
51
what’s the reaction and observation of iodide ions with AgNO3
Pale yellow ppt Ag+(aq) + I-(aq) => AgI(s)
52
why is ammonia solution used after reacting halide ions with AgNO3 to help identity the halide ion
The silver halide ppt can be treated with ammonia solution to help differentiate between them if the colours look similar
53
what’s the observation with AgCl (s) and aqueous ammonia
Dissolves
54
what’s the observation with AgCl (s) and concentrated ammonia
Dissolves
55
what’s the observation with AgBr (s) and aqueous ammonia
Does not dissolve
56
what’s the observation with AgBr (s) and concentrated ammonia
dissolves
57
what’s the observation with AgI (s) and aqueous ammonia
does not dissolve
58
what’s the observation with AgI (s) and concentrated ammonia
does not dissolve
59
in what order does the solubility of the silver halides in ammonia decrease
AgF> AgCl> AgBr> AgI
60
what is the reaction of silver chloride (AgCl) and DILUTE ammonia to produce a complex ion
AgCl(s) +2NH3(aq) => Ag(NH3)2 +(aq) +Cl- (aq)
61
what’s the reaction between silver bromide (agbr) with concentrated ammonia to form a complex ion
AgBr(s) + 2NH3(aq) =>Ag(NH3)2 +(aq) + Br-(aq)
62
EQ : Chlorine has a weak bp because the forces between the molecules are weak . Explain how these forces arise between molecules of chlorine (3)
- Imbalance of electron density in chlorine - induced a dipole in the neighbouring molecule - temporary dipoles attract
63
why is HNO3 added to test for halide ions
- removed ions that may give other ppt with AgNo3
64
why is silver nitrate solution used to test for halide ions
produces a precipitate with chloride , iodide and bromide ions
65
what’s the reaction of chlorine with water containing two acids
2Cl2 + 2H2O => HCl + HClO
67
EQ : Explain why chlorine is used to kill bacteria in swimming pools even though chlorine is toxic (2)
- only added in small amounts - health benefits of adding chlorine outweighs the risk
68
EQ : explain why bromide ions react differently from chloride ions when reacted with conc sulfuric acid (2)
- Bromide ions are bigger than chloride ions - therefore bromide ions are more easily oxidised / lose an electron more easily
69
EQ : A colourless solution contains a mixture of sodium chloride and sodium bromide . Using aq AgNO3 and any other reagents , develop a procedure to prepare a sample of silver bromide from this mixture , use equations (6)
- add silver nitrate - to form ppt of AgCl and AgBr - AgNO3 + NaCl => AgCl + NaNO3 - AgNO3 + NaBr => AgBr + NaNO3 - add excess of dilute ammonia to mixture of ppt - silver chloride ppt dissolves - AgCl + 2NH3 => Ag(NH3)2+ + Cl- - filter off remaining silver bromide ppt - wash to remove soluble compounds - dry to remove water
70
EQ : 2Cl2 + 2H2O (reverse sign ) HCl + HOCl Maintains water at a pH slightly greater than 7 Explain how this affects equilibrium established when chlorine is added to water (2)
- Hydroxide ions react with the acids -Equilibirum shifts to the right

Chemistry Year 12 (26 decks)

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