The Halogens

Question 1

What is the colour of fluorine molecules?

Answer 1

Pale yellow

Question 2

Physical state of fluorine?

Answer 2

Gas

Question 3

Colour of chlorine?

Answer 3

Green

Question 4

Physical state of chlorine

Answer 4

Gas

Question 5

Colour of bromine

Answer 5

Red-brown

Question 6

Physical state of bromine

Answer 6

Liquid

Question 7

Iodine colour

Answer 7

Grey

Question 8

Iodine physical state

Answer 8

Solid

Question 9

How do their melting and boiling pints change?

Answer 9

Melting and boiling points increase down the group due to increased strength of London forces as the size and relative mass of the atoms increases

Question 10

What happens volatility down the group?

Answer 10

It decreases

Question 11

Are halogens oxidising or reducing agents?

Answer 11

Oxidising agents

Question 12

Why are halogens less reactive down the group?

Answer 12

Atomic radii increases
More shielding
Harder for larger atoms to attract the electron needed to form an ion

Question 13

What happens in displacement reactions?

Answer 13

The colour changes

Question 14

How can you see the colour changes of displacement reactions?

Answer 14

Shake the reaction mixture with an organic solvent like hexane

Question 15

Which layer is on top the organic solvent or the aqueous solution?

Answer 15

The organic solvent

Question 16

Does iodine react with KBr?

Answer 16

No

Question 17

Does iodine react with KCl?

Answer 17

No

Question 18

What colour is iodine in aqueous solution?

Answer 18

Brown/ orange

Question 19

What colour is iodine in organic solution?

Answer 19

Purple

Question 20

Does bromine react with KCl?

Answer 20

No

Question 21

What colour is bromine in aqueous solution?

Answer 21

Yellow

Question 22

What colour is bromine water in organic solution?

Answer 22

Orange

Question 23

What colour is bromine when it displaces iodine in aqueous solution?

Answer 23

Orange/brown from the I2

Question 24

What colour is bromine when it displaces iodine in organic solution?

Answer 24

Purple due to I2

Question 25

What colour is chlorine water?

Answer 25

Colourless

Question 26

What colour is chlorine water when it displaces bromine in aqueous solution?

Answer 26

Yellow due to the Br2

Question 27

What colour is chlorine when it displaces bromine in organic solution?

Answer 27

Orange due to the Br2

Question 28

What colour is chlorine when it displaces iodine in aqueous solution?

Answer 28

Orange/ brown due to I2

Question 29

What colour is chlorine when it displaces iodine in organic solution?

Answer 29

Purple due to the I2

Question 30

What colour is KI?

Answer 30

Colourless

Question 31

What colour is KBr?

Answer 31

Colourless

Question 32

What colour is KCl?

Answer 32

Colourless

Question 33

What colour is chlorine water?

Answer 33

Colourless

Question 34

What colour is bromine water?

Answer 34

Yellow

Question 35

What colour is iodine solution?

Answer 35

Orange/brown

Question 36

What will chlorine displace?

Answer 36

Bromide and iodide

Question 37

What will bromine displace?

Answer 37

Iodide

Question 38

What is used to test for halides?

Answer 38

Silver nitrate solution | AgNO3

Question 39

Is chloride soluble in aqueous ammonia?

Answer 39

Soluble in dilute ammonia

Question 40

Is bromide soluble in aqueous ammonia?

Answer 40

Soluble in concentrated ammonia

Question 41

Is iodide soluble in aqueous ammonia?

Answer 41

Insoluble in concentrated and dilute ammonia

Question 42

What do halogens undergo disproportionation reactions with?

Answer 42

Cold dilute alkali solutions

Question 43

What is the ratio of halogen to alkali in disproportionation reactions?

Answer 43

1 Halogen molecule for one mole of alkali

Question 44

What species is both oxidised and reduced?

Answer 44

The halogen

Question 45

What happens if you mix chlorine gas with cold, dilute aqueous sodium hydroxide?

Answer 45

``` Sodium chlorate (I) solution forms which is NaClO Known as household bleach ```

Question 46

What happens when you mix chlorine with water?

Answer 46

It undergoes disproportionation

Question 47

What are the products when chlorine reacts with water?

Answer 47

Chloric(I) acid and HCl

Question 48

What does aqueous chloric(I) acid do?

Answer 48

It ionises to form chlorate(I) ions | ClO-

Question 49

What do chlorate (I) ions do?

Answer 49

Kill bacteria

Question 50

Advantages of using chlorine as water treatment?

Answer 50

Kills disease-causing microorganisms Some chlorine remains in the water and prevents reinfection further down the supply Prevents the growth of algae Eliminates bad tastes and smells Removes discolouration caused by organic compounds

Question 51

Disadvantages of using chlorine to treat water

Answer 51

Chlorine gas is harmful if breathes in Liquid chlorine can cause severe chemical burns Chlorine reacts with organic compounds in water to form chlorinated hydrocarbons which can be carcinogenic People don’t have a choice but to drink it

Question 52

Alternatives to chlorine in water treatment

Answer 52

Ozone which is a strong oxidising agent that kills microorganisms however it’s expensive to produce and has a short half life meaning the water treatment isn’t permanent UV light damages the DNA of microorganisms and kills them but is ineffective in cloudy water and doesn’t stop water being contaminated further down the line