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AQA A-Level Inorganic Chemistry > 2.3 Group 7 > Flashcards

2.3 Group 7 Flashcards

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1
Q

What does halogen mean?

A 
Halo = salt
Gen = maker/producer
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2
Q

What are the physical appearances of the halogens at room temperature?

A

Fluorine - yellow gas
Chlorine - green gas
Bromine - orange liquid
Iodine - grey/black solid

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3
Q

What is the trend for atomic radius of the halogens?

A

Atomic radius increases down the group

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4
Q

Why does the atomic radius increase down the group?

A

There are more principal energy levels = larger atomic radius

Because of more electrons

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5
Q

What is the trend for boiling points of the halogens?

A

Boiling point increase going down the group

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6
Q

Why does the boiling point increase down the group?

A

Atomic radius increases due to increased number of electrons therefore greater van der Waals forces which require more energy to overcome

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7
Q

What are some physical properties of halogens?

A

Similar electronic structure
Non-metals
Diatomic molecules
Toxic coloured vapours

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8
Q

What is the trend of electronegativity in the halogens?

A

Electronegativity decreases down group 7

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9
Q

Why does electronegativity decrease down the group?

A

Because…
Nuclear charge increases
Atomic radius increases
Electron shielding increases

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10
Q

What is the trend in the halogens oxidising ability?

A

As you go down group 7 oxidising ability decreases

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11
Q

Which halogen is the most powerful oxidising agent? Why don’t we look at it?

A

Fluorine

It reacts with water therefore the reactions in solutions can’t be easily investigated

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12
Q

What does displacement reactions of halogens include?

A

Salt solution: Potassium chloride, bromide, iodide (doesn’t have to be potassium- any spectator ion)

Halogen solution: Cl2, Br2, I2 (aq)

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13
Q

What are the colours of the halogen solutions used in displacement reactions?

A

Chlorine - colourless
Bromine - yellow
Iodine - brown

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14
Q

What can’t happen in a displacement reaction?

A

Chlorine can’t oxidise itself
Bromine can’t oxidise itself
Iodine can’t oxidise itself

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15
Q

What are the only displacement reactions that can happen?

A

Chlorine oxidises bromide
Chlorine oxidises iodide
Bromine oxidises iodide

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16
Q

Which halogen seems to work best in the displacement reactions? Why?

A

Chlorine

It has the smallest atomic radius
Therefore the electron being accepted is closer to the nucleus - and more strongly attracted

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17
Q

What are the colour changes in the displacement reactions?

A

Chlorine oxidises Bromide
Colourless to yellow

Chlorine oxidises Iodide
Colourless to brown

Bromine oxidises Iodine
Yellow to brown

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18
Q

What is the trend in halogens for reducing ability? Why?

A

Reducing power increases down the group

Ionic radius increases therefore electrons are lost more easily

19
Q

What halides are used in the reactions with concentrated sulphuric acid?

A

(Sodium)
Fluoride, chloride, bromide, iodide

(Sodium doesn’t matter as only a spectator ion is required)

20
Q

What are the reaction products produced when reacting concentrated sulphuric acid with Sodium Chloride/Fluoride? Observations?

A

HCl/HF - Misty fumes

21
Q

What are the reaction products produced when reacting concentrated sulphuric acid with sodium bromide? Observations?

A

HBr - Misty fumes
Br2 - Brown fumes (temperature dependent)
SO2 - colourless, choking gas

22
Q

What are the reaction products produced when reacting concentrated sulphuric acid with sodium iodide? Observations?

A 
HI - Misty fumes
I2 - Purple fumes + black solid
SO2 - colourless, choking gas
S - yellow solid
H2S - colourless gas, bad egg smell
23
Q

What test can you tell HF/HCl/HBr/HI is produced?

A

Turns Universal indicator paper red

24
Q

What test can you tell SO2 is produced?

A

Turns acidified Potassium dichromate (VI) from orange to green

25
Q

What test can you tell H2S is produced?

A

Turns lead (II) nitrate black

26
Q

Is the reaction between (spectator ion) Chloride and sulphuric acid a redox reaction? Equation using K?

A

No
Cl- can’t reduce H2SO4

KCl + H2SO4 -> KHSO4 + HCl

(Can replace with F and makes no difference)

27
Q

What happens in the (spectator ion) Bromide reacting with sulphuric acid reaction? Equation with K?

A

KBr + H2SO4 -> KHSO2 + HBr

The HBr produced reacts again with the H2SO4
The bromide ion is therefore capable of reducing the H2SO4

(The initial reaction is still the same)

28
Q

What are the reactants and products in the half equations for the reaction between (spectator ion) Bromide and sulphuric acid?

A

2Br- -> Br2

H2SO4 -> SO2

29
Q

What happens in the (spectator ion) Iodide reacting with sulphuric acid reaction? Equation with K?

A

KI + H2SO4 -> KHSO2 + HI

The HI produced reacts again with the H2SO4
The iodide ion are oxidised to iodine
The sulphuric acid is reduced to sulphur dioxide, sulphur and hydrogen sulfide

(The initial reaction is still the same)

30
Q

What are the reactants and products in the half equations for the reaction between (spectator ion) iodide and sulphuric acid?

A

I- -> I2

H2SO4 -> SO2

H2SO4 -> S

H2SO4 -> H2S

31
Q

What is the other tests for halide ions?

A

The halogen ion
Add dilute nitric acid
Then silver nitrate

Or
Dilute ammonia solution
Or
Concentrated ammonia solution

32
Q

What is the result of each of the halogen tests for fluoride? (Silver nitrate, dilute and concentrated ammonia solution)

A

NVC for all

33
Q

What is the result of each of the halogen tests for chloride? (Silver nitrate, dilute and concentrated ammonia solution)

A

Silver nitrate - white precipitate
Dilute NH3 - redissolves = colourless solution
Concentrated NH3 - redissolves = colourless solution

34
Q

What is the result of each of the halogen tests for bromide? (Silver nitrate, dilute and concentrated ammonia solution)

A

Silver nitrate - cream precipitate
Dilute NH3 - NVC
Concentrated NH3 - redissolves = colourless solution

35
Q

What is the result of each of the halogen tests for iodide? (Silver nitrate, dilute and concentrated ammonia solution)

A

Silver nitrate - yellow precipitate
Dilute NH3 - NVC
Concentrated NH3 - NVC

36
Q

Why do you have to add dilute nitric acid before silver nitrate when testing for halide ions?

A

It removes interfering ions: like carbonate and hydroxide

Can’t use HCl = false positive for chloride ions
Can’t use H2SO4 - silver sulphate produced would hide the results

37
Q

How would you form an equation to show the reaction of halide ions with silver nitrate?

A

KCl (aq) + AgNO3 (aq) —>
AgCl (s) + KNO3 (aq)

Solid shows you know it is a precipitate

38
Q

How do we acquire chlorine?

A

From electrolysis of NaCl

NaCl is found in the sea

39
Q

What does chlorine react with cold water to form?

A

Cl2 + H2O ⇌ HClO + HCl

HClO = useful
Bleaches indicator paper

HCl - turns Universal Indicator paper red

40
Q

In a reaction between chlorine and water what is significant?

A

Chlorine has three different oxidation states

It gets oxidised and reduced

This is called disproportionation

41
Q

What is HClO used for? Is it safe for humans?

A

Kills bacteria in water

It doesn’t harm humans

There are some risks as chlorine is toxic but the benefits of clean water outweigh the risks

42
Q

What can chlorine react with?

A

Water

Sodium hydroxide

43
Q

What are the equations for chlorine reacting with water (UV light)? Sodium hydroxide?

A

Chlorine + water —>
Hydrochloric acid + oxygen

Chlorine + sodium hydroxide —>
NaClO + NaCl + water

44
Q

What are the conditions for each chlorine and water reaction?

A

To produce HClO + HCl
Just cold water

To produce HCl + O2
UV light is needed

AQA A-Level Inorganic Chemistry (6 decks)

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