Group 7

Question 1

What are the characteristics of fluorine?

Answer 1

Colour- pale yellow
Physical state- gas
highly reactive

Question 2

What are the characteristics of chlorine?

Answer 2

Colour- green
Physical state - gas
poisonous in high concentrations

Question 3

What are the characteristics of bromine?

Answer 3

Colour- red-brown
Physical state- liquid
produces dense brown/orange poisonous fumes

Question 4

What are the characteristics of iodine?

Answer 4

Colour- grey
Physical state-solid
produces purple gas

Question 5

What is the trend of boiling points down the group?

Answer 5

The boiling points increase

Question 6

Why do the boiling points increase down the group?

Answer 6

Down the group, the molecules are larger
There are more electrons
Therefore, there are stronger van der Waals forces
More energy is required to break the forces

Question 7

What is the trend of electronegativity up the group?

Answer 7

The electronegativity increases

Question 8

Why does the electronegativity increase up the group?

Answer 8

The atomic radius decreases
there is less shielding
there is a stronger force of attraction on the electrons

Question 9

What is electronegativity?

Answer 9

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

Question 10

Why is fluorine the most electronegative element?

Answer 10

It is the smallest atom with the most need to fill its shell

it has the least number of electrons and shells

Question 11

What happens when a halogen reacts with a halide in a solution?

Answer 11

A halogen will displace a halide from the solution if the halide is below the halogen in the periodic table

Question 12

What is the trend of oxidising strength down the group?

Answer 12

The oxidising strength decreases down the group

Question 13

What happens when potassium chloride reacts with chlorine?

Answer 13

No reaction

Remains green

Question 14

What happens when potassium chloride reacts with bromine?

Answer 14

No reaction

Remains orange

Question 15

What happens when potassium chloride reacts with iodine?

Answer 15

No reaction

Remains brown

Question 16

What happens when potassium bromide reacts with chlorine?

Answer 16

Orange solution formed

Chlorine has been displaced by bromine

Question 17

What happens when potassium bromide reacts with bromine?

Answer 17

No reaction

Remains orange

Question 18

What happens when potassium bromide reacts with iodine?

Answer 18

No reaction

Remains brown

Question 19

What happens when potassium iodide reacts with chlorine?

Answer 19

Brown solution formed

Chlorine displaced by iodine

Question 20

What happens when potassium iodide reacts with bromine?

Answer 20

Brown solution formed

Bromine displaced by iodine

Question 21

What happens when potassium iodide reacts with iodine?

Answer 21

No reaction

Question 22

What is the trend of the reducing power of the halides down the group?

Answer 22

The reducing power increases down the group

Question 23

Why does the reducing power increase down the group?

Answer 23

• the ions get bigger down the group
• the further away the outer electrons are from the nucleus
• there is more shielding
• weaker force of attraction

Question 24

What happens when the reducing power increases down the group?

Answer 24

The greater the reducing power
the greater the reactivity
the faster the reduction reactions take place

Question 25

What happens when fluoride reacts with concentrated sulfuric acid?

Answer 25

NaF(s) + H2SO4(aq) → NaHSO4(s) + HF(g)

Question 26

What happens when chloride reacts with concentrated sulfuric acid?

Answer 26

NaCl(s) + H2SO4(aq) → NaHSO4(s) + HCl(g)

Question 27

Why are the reactions between fluoride and chloride with concentrated sulfuric acid not redox reactions?

Answer 27

HF and HCl aren't strong enough reducing agents to reduce the sulfuric acid The oxidation states of the halide and sulfur remain the same

Question 28

What happens when bromide reacts with concentrated sulfuric acid?

Answer 28

NaBr(s) + H2SO4(aq) → NaHSO4(s) + HBr(g) | 2HBr(aq) + H2SO4(aq) → Br2(g) + SO2(g) + 2H2O(l)

Question 29

What happens when iodide reacts with concentrated sulfuric acid?

Answer 29

NaI(s) + H2SO4(aq) → NaHSO4(s) + HI(g) 2HI(g) + H2SO4(aq) → I2(s) + SO2(g) + 2H2O(l) 6HI(g) + SO2(aq) → 3I2(s) + H2S(g) + 2H2O(l)

Question 30

What observations can be made when bromide reacts with concentrated sulfuric acid?

Answer 30

steamy fumes of HBr are produced Red fumes of Br2 colourless, acidic gas, SO2

Question 31

What observations can be made when iodide reacts with concentrated sulfuric acid?

Answer 31

``` steamy fumes of HI are produced black solid and purple fumes of I2 colourless acidic gas, SO2 yellow solid, sulfur toxic, rotten egg smell, H2S ```

Question 32

What observations can be made when iodide reacts with concentrated sulfuric acid?

Answer 32

``` steamy fumes of HI are produced black solid and purple fumes of I2 colourless acidic gas, SO2 yellow solid, sulfur toxic, rotten egg smell, H2S ```

Question 33

How would you test for halides using silver nitrate

Answer 33

Add nitric acid to the solution to remove ions which may give a false positive result Add a few drops of silver nitrate solution A precipitate is formed The colour of the precipitate will determine the halide present

Question 34

What is the colour of the precipitate when silver nitrate is used to test chlorides?

Answer 34

White precipitate

Question 35

What is the colour of the precipitate when silver nitrate is used to test bromides?

Answer 35

Cream precipitate

Question 36

What is the colour of the precipitate when silver nitrate is used to test iodides?

Answer 36

Yellow precipitate

Question 37

What is the trend of solubility of silver halides in ammonia?

Answer 37

The solubility decreases down the group

Question 38

What observations would be made when ammonia is added to silver chloride?

Answer 38

White precipitate | Silver chloride dissolves in dilute ammonia

Question 39

What observations would be made when ammonia is added to silver bromide?

Answer 39

Cream precipitate | Silver bromide dissolves in concentrated ammonia

Question 40

What observations would be made when ammonia is added to silver iodide?

Answer 40

Yellow precipitate | Insoluble in both dilute and concentrated ammonia

Question 41

Why is chlorine used in water?

Answer 41

It kills bacteria

Question 42

What happens when chlorine reacts with water?

Answer 42

It undergoes disproportionation

Question 43

What is disproportionation?

Answer 43

A reaction where an is element simultaneously oxidised and reduced

Question 44

What happens when chlorine reacts with water?

Answer 44

Cl2(g) + H2O(l) → 2H+(aq) + Cl-(aq) + ClO(aq)

Question 45

What happens when chlorine reacts with water in sunlight?

Answer 45

2Cl2(g) + 2H2O(l) → 4H+(aq) + 4Cl-(aq) + O2(g)

Question 46

What are the disadvantages of using chlorine for water treatment?

Answer 46

- chlorine gas is harmful - liquid chlorine causes severe burns - chlorine reacts with organic compounds in water forming chlorinated hydrocarbons which are carcinogenic

Question 47

Why is chlorine still used in water treatment?

Answer 47

The benefits to health of water treatment by chlorine outweighs its toxic effects

Question 48

What happens chlorine reacts with cold, dilute aqueous NaOH?

Answer 48

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

Question 49

What is sodium chlorate(NaClO) used for?

Answer 49

bleach