1a3 marks
Chlorine and iodine are in the same group in the Periodic Table.
i)
Complete the electronic configuration of chlorine using the s, p, d notation.
(1)
1s2 ..................................................
ii)
Explain why iodine and chlorine have many similar chemical reactions.
(2)
1b7 marks
Members of the same group sometimes react in different ways.
Iodine and chlorine react differently with thiosulfate ions, S2O32−.
Iodine gives S4O62−, whilst chlorine gives SO42−.
i)
Complete the table by identifying the oxidation numbers of sulfur in the three sulfur-containing ions.
| Ion | Oxidation number of sulfur |
| S2O32− | |
| SO42− | |
| S4O62− |
(2)
ii)
The equation for the reaction of iodine with thiosulfate ions is
2S2O32− + I2 → 2I− + S4O62−
State, in terms of electrons, why iodine is classified as an oxidising agent in this reaction.
(1)
iii)
Use your answer to b(i) to show that chlorine is a stronger oxidising agent than iodine.
(1)
iv)
Chlorine reacts in aqueous solution with S2O32− to give SO42−.
The ionic half-equation for the reaction of chlorine is
Cl2 + 2e− → 2Cl−
Write the ionic half-equation for the reaction of aqueous S2O32− to give SO42−.
State symbols are not required.
(2)
v)
Use your answer to (b)(iv) and the half-equation for chlorine, to write the overall ionic equation for the reaction between chlorine and thiosulfate ions.
State symbols are not required.
(1)
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