Group 7

Question 1

Why are the halogens considered to be p-block elements?

Answer 1

Their highest energy electron can be found in a p-sub shell

Question 2

What does the term volatility mean?

Answer 2

How easily a substance turns from a liquid into a gas

Question 3

Why does the boiling points increases down group 7?

Answer 3

They become less volatile as you go down the group

Question 4

What happens to the intermolecular forces between the molecules as we descend group seven?

Answer 4

Increases

Question 5

Why do the induced dipole dipole interactions increase between the molecules?

Answer 5

The molecules contain more electrons

Question 6

What sort of energy is required to break the induced dipole dipole interactions between molecules of the halogens?

Answer 6

High amounts of energy

Question 7

What is the bond type in the halogen molecule?

Answer 7

Covalent

Question 8

What do group 7 molecules exist as?

Answer 8

Diatomic molecules

Question 9

What is the structure of the halogens?

Answer 9

Simple molecular

Question 10

Does the volatility increase or decrease down the group?

Answer 10

Decrease

Question 11

Does the boiling point increase or decrease down the group?

Answer 11

Increase

Question 12

Does the intensity of the colour of the halogens increase or decrease down the group?

Answer 12

Increases

Question 13

State & explain the trend in boiling points of chlorine, bromine and iodine

Answer 13

Going down the group, boiling points increase
Molecules become bigger = more electrons and greater surface contact
Greater induced dipole dipole forces between molecules
More energy is required to overcome these forces

Question 14

Why would astatine be expected to react similarly to other halogens?

Answer 14

Same number of valence electrons in its outer shell
So similar chemical properties

Question 15

How many electrons do halogens have in their outer shell?

Answer 15

7 electrons

Question 16

When a halogen atom readily accepts an electron what does it form?

Answer 16

Halide ion
Full outer shell of electrons
Results in a stable arrangement

Question 17

What do all halogens act as?

Answer 17

Oxidising agents

Question 18

What is the most powerful oxidising agent out of the halogens?

Answer 18

Fluorine

Question 19

What is oxidation the loss of?

Answer 19

Electrons

Question 20

Does the oxidising agent itself get reduced or oxidised?

Answer 20

Reduced

Question 21

Does the oxidation agent gain or loss electrons?

Answer 21

Gain electrons

Question 22

What is reduction the gain of?

Answer 22

Electrons

Question 23

Does the reducing agent itself get reduced or oxidised?

Answer 23

Oxidised

Question 24

Does the reducing agent gain or loss electrons?

Answer 24

Loss electrons

Question 25

State and explain the trend in oxidising power down group 7

Answer 25

Number of protons/nuclear charge increases down the group Atomic radius increases down the group Shielding increases down the group Nuclear attraction decreases down the group It becomes more difficult to gain electron and ability to oxidise decreases down the group

Question 26

What is a displacement reaction?

Answer 26

A reaction in which a more reactive element displaces a less reactive element from an aqueous solution of the latter’s ions

Question 27

How can the decrease in reactivity of the halogens be demonstrated?

Answer 27

Displacement reactions of the aqueous halides using chlorine, bromine and iodine

Question 28

What is observed when you react chlorine water with chloride ions?

Answer 28

N/A

Question 29

What is observed when you react chlorine water with bromide ions?

Answer 29

Pale green to orange solution

Question 30

What is observed when you react chlorine water with iodide ions?

Answer 30

Pale green to brown

Question 31

What is observed when you react bromine water with chloride ions?

Answer 31

No observable reaction - stays orange

Question 32

What is observed when you react bromine water with bromide ions?

Answer 32

N/A

Question 33

What is observed when you react bromine water with iodide ions?

Answer 33

Orange to brown

Question 34

What is observed when you react iodine water with chloride ions?

Answer 34

No observable reaction - stays brown

Question 35

What is observed when you react iodine water with bromide ions?

Answer 35

No observable reaction - stays brown

Question 36

What is observed when you react iodine water with iodide ions?

Answer 36

N/A

Question 37

What happens when an organic solvent is added to an aqueous halogen?

Answer 37

Molecules are extracted into the organic layer (the top) A more vivid colour is present

Question 38

What is observed when you react chlorine with an organic solvent?

Answer 38

Both layers are pale green

Question 39

What is observed when you react bromine with an organic solvent?

Answer 39

Both layers are orange

Question 40

What is observed when you react iodine with an organic solvent?

Answer 40

Top layer - purple Bottom layer - brown

Question 41

What does the term disproportionation mean?

Answer 41

When an element is being both oxidised and reduced in a redox reaction

Question 42

Write the balanced equation for the reaction between sodium hydroxide and chlorine

Answer 42

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

Question 43

What are the conditions for the disproportionation reaction between sodium hydroxide and chlorine?

Answer 43

Cold dilute alkali

Question 44

What does the disproportionation reaction between sodium hydroxide and chlorine give us?

Answer 44

Chloride Chlorate ions (present in bleach)

Question 45

What is the reaction between chlorine and water used in?

Answer 45

Water purification

Question 46

What does the chlorate ion (OCl-) kill?

Answer 46

Bacteria Acts as a weak bleach

Question 47

What is formed between chlorine and water during a disproportionation reaction?

Answer 47

Hydrochloric acid Chloric acid (I)

Question 48

How can the acidic nature and the bleaching effect of chlorine in water be seen?

Answer 48

Adding blue litmus indicator into aqueous chlorine

Question 49

What happens to the blue litmus indicator after being added to the aqueous chlorine?

Answer 49

Blue litmus indicator will turn red (due to the acid) then colourless (due to the bleach)

Question 50

Why should we not put chlorine in drinking water?

Answer 50

Chlorine is toxic in excess Chlorine can react with hydrocarbons to form chlorinated hydrocarbons which are carcinogens