Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

A Level - Chemistry > 4B: Elements of group 7 > Flashcards

4B: Elements of group 7 Flashcards

(66 cards)

Start Studying
1
Q

How does electronegativity of elements change going down the group?

A

Electronegativity decreases going down the group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the physical state of the group 7 elements?

A

F2 - gas
Cl2 - gas
Br2 - liquid
I2 - solid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the colour of the group 7 elements?

A

F2- pale yellow
Cl2 - green
Br2 - red-brown
I2 - grey

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the solubility of halogens?

A

Low solubility in water as non-polar

Soluble in organic compounds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What colour do halogens go in water?

A

Cl2 - virtually colourless
Br2 - yellow/orange
I2 - brown

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What colour do halogens go in organic solvents?

A

Cl2 - virtually colourless
Br2 - orange/red
I2 - pink/violet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How does reactivity change going down the group?

A

Becomes less reactive going down the group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What do halogens do in redox reactions?

A

Reduced - gains electrons

Oxidising agents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Why do halogens become less reactive going down the group?

A

Atom size increases therefore shielding increases

Makes it harder for larger atoms to attract other electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How does the melting and boiling points change going down the group?

A

Mp/bp increases going down the group

Due to increasing London forces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Why is fluorine difficult to study?

A

It is a toxic gas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why is astatine difficult to study?

A

Highly radioactive and decays quickly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the rule for the displacement of halide ions?

A

More reactive halogen can displace less reactive halide ion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the usual oxidation number of a halide ion?

A

-1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Give an example when halide ions have a positive oxidation number?

A

When in a compound with oxygen as it has a higher electronegativity (except F)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How are the halogen elements usually formed?

A

Oxidation of the halide ions in a redox reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How can you tell if there has been a displacement of the halides?

A 
Colour change 
(orange for bromine, brown for iodine)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How can you make the colour change more apparent in halide displacement?

A

Mix end solution with organic solvent like hexane

Produces distinct layer of colour

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How do halogens react with group 1 metals?

A

2M + X2 -> 2MX
M = metal, X = halogen
M = oxidised, X = reduced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How do halogens react with group 2 metals?

A

M + X2 -> MX2
M = metal, X = halogen
M = oxidised, X = reduced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What happens when a halogen interacts with a cold alkali?

A

Disproportionation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the equation for the disproportionation of halogens in cold alkali?

A

X2 + 2NaOH -> NaOX + NaX + H20

X = halogen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the chemical formula of bleach?

A 
NaClO
Sodium Chlorite (I)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the reaction to form bleach?

A

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

Disproportionation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What is the use of sodium chlorite?
Water treatment | Bleach textiles and paper
26
What is a XO- ion? | X = halogen
Halate(I) ion
27
At what temperature is an alkali said to be hot?
Over 60C
28
What is the reaction between a halogen and a hot alkali?
3X2 + 6NaOH -> NaXO3 + 5NaX + 3H2O
29
What should be done when chlorine is produced in a reaction?
Carry the experiment out in a fume cupboard as its toxic
30
Why does fluorine have so little uses?
Extremely reactive
31
What is the use of sodium fluoride?
Strengthen enamel (found in fluoride toothpaste)
32
What is the compound polytetrafluoroethene (PTFE)?
Used in non-stick surfaces like on frying pans
33
What is the use of chlorine?
Kills bacteria in water | Polyvinlychloride (PVC)
34
What is the reaction which causes chlorine to kill bacteria?
Cl2 + H2O -> HCl (aq) + HClO (aq) HClO + H2O ClO- + H3O+ ClO- kills bacteria
35
What is the name of the substance HClO?
Hypochlorous acid
36
What is the use of PVC?
Plastic used for doors and windows
37
What is the use of sodium chlorate(V)?
Powerful weed-killer
38
Why does elemental bromine not have many uses?
It is a very corrosive liquid
39
What is the use of potassium bromide?
A sedative
40
What is the use of iodine?
Important antiseptic
41
What is the use of potassium iodide?
Sometimes added to salt | Lack of iodine leads to the disease goitre
42
How does the reducing power of halides change down the group?
Reducing power increases | loses electron easier
43
Why does reducing power increase going down the group?
Easier to lose electron as: Electrons further away from nucleus Extra shells means increased shielding Effective nuclear charge doesn't change
44
What is the product when a halide reacts with sulphuric acid?
Hydrogen halide
45
What are the reactions of KF/KCl with H2SO4? | K = unspecified ion
KF/Cl (s) + H2SO4 (l) -> KHSO4 (s) + HF/Cl (g)
46
When a hydrogen halide is produced what is observed?
Misty fumes are produced
47
When F-/Cl- ions react with H2SO4 is it a redox reaction?
No - oxidation numbers of halide and sulphur stay the same
48
When F-/Cl- ions react with H2SO4 why is there not another reaction?
F-/Cl- ions aren't strong enough to reduce the sulphuric acid
49
What is the reaction between KBr and H2SO4? | K = unspecified ion
KBr (s) + H2SO4 (l) -> KHSO4 (s) + HBr (g) 2HBr + H2SO4 -> Br2 (g) +SO2 (g) + 2H2O (l)
50
Why can the second step happen when KBr reacts with H2SO4?
Br- is a stronger reducing agent than Cl- | Reacts with H2SO4 in a redox reaction
51
What would you observe if bromine gas is produced?
Orange fumes
52
What is noteworthy about SO2?
They are choking fumes | Experiments with thus as a product should be done in a fume cupboard
53
What is the reaction between KI and H2SO4? | K = unspecified ion
KI (s) + H2SO4 (l) -> KHSO4 (s) + HI (g) 2HI + H2SO4 -> I2 (g) +SO2 (g) + 2H2O (l) 6HI + SO2 -> H2S + 3I2 +2H2O
54
Why can the second & third step happen when KI reacts with H2SO4?
As very strong reducing agent | It can reduce SO2 whereas Br- cannot
55
What is noteworthy about the gas H2S?
Toxic gas that smells of rotten eggs
56
What colour are hydrogen halides?
Colourless
57
What happens when hydrogen halides dissolve in water? | X = halide
HX + H20 -> H3O+ +X- Ionic: HCl -> H+ + Cl- This is the formation of a hydrohalide acid
58
How do hydrogen halides react with ammonia gas?
NH3 + HX -> NH4X (s) | Produces white fumes
59
What is the test for halides?
Add dilute nitric acid to remove other ions Add silver nitrate (AgNO3) Precipitate of silver halide formed
60
What is the ionic equation for the test for halides?
Ag+ (aq) + X- (aq) -> AgX (s)
61
What colour precipitate is formed for each halide in the standard halide test?
``` F- = No precipitate (AgF is soluble) Cl- = White Br- = Cream I- = Yellow ```
62
What can be done to identify the halide ion after the silver nitrate test?
Adding ammonia solution | If it dissolves then it will go colourless
63
What occurs when ammonia solution is added after the silver nitrate test?
``` Cl- = Precipitate dissolves in dilute ammonia Br- = Dissolves in conc. ammonia, not in dilute I- = precipitate will not dissolve ```
64
What is the test for SO2?
Potassium dichromate paper turns from orange to green
65
What is the test for H2S?
Turns lead ethanoate paper from white to black
66
What is the affect of light after the silver nitrate test?
``` Cl- = Purple Br- = Green I- = No change ```

A Level - Chemistry (26 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions