Inorganic chemistry: 10.2 The chemical reactions of the halogens

Question 1

How do halogens usually react?

Answer 1

They usually react by gaining electrons to become negative ions with a charge of -1.
These reactions are all redox reactions, as the halogens are oxidising agent which oxdise another species and get reduced themselves.

Question 2

Write a half equation to show how halogens react.

Answer 2

Cl2 + 2e- > 2Cl-

Each atom of the cl molecule gained 1 electron to become negatively charged ion. Hence reduction.

Question 3

What is the trend of oxidising ability going up the group?

Answer 3

Going up the group, oxidising ability increases i.e. Fluorine is the most oxidising.

Question 4

How do halogens react in displacement reactions with metal halides?

Answer 4

Halogens will react with metal halides in solution, in such a way that the halide in the compound will be displaced by a more reactive halogen but not by a less reactive one. i.e. A halogen with a strong oxidising ability will displace a halogen less oxidising.

Question 5

Write the eq for the reaction of chlorine and Sodium Bromide and oxidation state of each element that gets reduced and oxidised.

Answer 5

Cl2(aq)+ 2NaBr (aq) > Br2 (aq) + 2NaCl (aq).
Note: symbols in aq as this displacement reactions between halogens and metal halides occurs in solution.
Oxdising state:
Cl2: 0
2NaBr: Br has an oxidation state of -1 and Na: +1
Br2 has an oxidation state of 0.
2NaCl: Na is +1 and Cl is -1.

Question 6

Write the ionic equation for the reaction of Chlorine and sodium Bromide.

Answer 6

Displacement reaction.
First write out the balance eq.
Cl2 (aq)+ 2NaBr (aq) > Br2 (aq) + 2Nacl(aq).
Then write out ions.
Cl2(aq) +
2Na+ cancels out as they are spectator ions.