Group 7

Question 1

What are the 1st 5 halogens their colour and state and RTP?

Answer 1

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

Question 2

What is the trend of boiling point down the group?

Answer 2

Increases down a group as the London forces strength increases due to more electrons.

Question 3

What is the trend of reactivity down the group and why?

Answer 3

Decrease in reactivity as there is more shielding and decreasing attraction due to a larger atomic radii, making it harder to attract the electron

Question 4

What is the trend in strength of oxidising agent as you go down the group?

Answer 4

Decreases

Question 5

What are the properties of a halogen?

Answer 5

Low melting and boiling points
Diatomic molecules which are:
Non polar (as same element)
And have Weak London forces between the molecules

Question 6

What compounds do they form and what colour are they?

Answer 6

Ionic compounds

White solids

Question 7

What is a group 7 redox half equation?

Answer 7

X2 + 2e- -> 2X-

Question 8

How does a halogens oxidation number change in a redox reaction and what does this suggest?

Answer 8

X(0) -> X(-1)

Means they are reduced and acts as the oxidising agent

Question 9

Which is the strongest halogen and why?

Answer 9

Fluorine as it forms the negative F- ion the easiest

Question 10

What is a displacement reaction?

Answer 10

The more reactive halogen will displace the less reactive halogen, it will oxidise the halide ion of a less reactive halogen.

Question 11

What are the colours of the halogens in:

1. Water
2. Cyclohexane

Answer 11

Fluorine:

1. Yellow/green
2. Colourless

Chlorine:

1. Pale green
2. Pale green

Bromine:

1. Orange
2. Orange

Iodine:

1. Brown
2. Violet

Question 12

Why may chlorine be dangerous?

Answer 12

1. Toxic gas
2. Environmentalists suspect when in water it reacts with organic matter forming chlorinated hydrocarbons which may cause cancer

Question 13

Why can chlorine be useful?

Answer 13

When dissolved in water it is a powerful disinfectant so makes the water safe to drink which will improve public health by reducing water borne diseases like cholera.

Question 14

What is disproportionation?

Answer 14

A redox reaction where the same element is simultaneously oxidised and reduced

Question 15

What is the reaction equation of the disproportionation of chlorine with water?
And what are the oxidation numbers?

Answer 15

Cl2 + H2O HCl + HClO

Cl(0) -> Cl(+1) oxidised (HClO)
Cl(0) -> Cl(-1) reduced (HCl)

Question 16

What does a ClO- ion do?

Answer 16

Bleaches- removes colour, whitens or disinfects often by oxidation

Question 17

What is the reaction equation of the disproportionation reaction of chlorine with cold dilute NaOH (aq)?
What are the oxidation numbers?

Answer 17

Cl2 + 2NaOH -> NaCl + NaClO + H2O

Cl(0) -> Cl(-1) reduced in NaCl
Cl(0) -> Cl(+1) oxidised in NaClO