Group 7 - chemical reaction

Question 1

How does the oxidising ability of halogen change going down the group

Answer 1

decreases

Question 2

How do halogen act as oxidising agents?

Answer 2

gain 2 electrons to produce 2 negatively charged ions

e.g.

2Cl₂ + 2e^- → 2Cl^-

Question 3

How do displacement reactions occur in halogens?

Answer 3

halogen will react with metal halides in solution in such a way that the halide in the compound will be displaced by a more reactive one

e.g. chlroine will displace bromide ions, but iodine will not

Question 4

What is the ionic equation for the reaction with chlorine with sodium bromide? What is the colour change?

Answer 4

Cl₂ (aq) + 2NaBr^-1 (aq) → Br₂ (aq) + 2NaCl_-1 (aq)

Cl₂ (aq) + 2Na⁺ (aq) + 2Br^- (aq) → Br₂ (aq) + 2Na⁺ (aq) + 2Cl^-

sodium ions are spectator ions

the two colourless starting materials react to produce the red-brown colour of bromine

Question 5

What is the oxidising agent in the reaction of sodium bromide and chlorine?

Answer 5

chlorine is the oxidising agent by removing electrons from Br^- to Br²

oxidation number increases from -1 to 0

Question 6

Why can’t you investigate fluorine in an aqueous solution?

Answer 6

it reacts with water

Question 7

How is bromine extracted from water?

Answer 7

oxidation of a halide by a halogen

seawater contains small amounts of bromide ions which can be oxidised by chlorine

Question 8

How is iodine extracted from kelp?

Answer 8

burning seaweed

washing with water

residue is heated with maganese dioxide and concentrated sulfuric acid and the iodine is liberated

Question 9

What observation is made when chlorine reacts with bromide ions in soln

Answer 9

• colourless to orange