Group 7: the halogensEdexcel A-Level Chemistry: Mind map

Exam questions on Group 7: the halogens

1. A technician compares the Group 7 elements chlorine, bromine and iodine in a fume cupboard at room temperature (about 20 °C).
   Explain why iodine has a higher boiling temperature than chlorine.2 marks
2. A student investigates displacement reactions of the halogens. She has aqueous solutions of potassium chloride, potassium bromide and potassium iodide, together with chlorine water, bromine water, aqueous iodine and the organic solvent cyclohexane, which is less dense than water and immiscible with it.
   The student adds aqueous iodine to potassium bromide solution and sees no reaction. Explain this, referring to the relative oxidising power of bromine and iodine.2 marks
3. A water company treats drinking water with chlorine to kill bacteria. A separate factory makes household bleach by passing chlorine into sodium hydroxide solution.
   Chlorine reacts with water as it dissolves. Write an equation for the reaction and explain, in terms of oxidation numbers, why it is a disproportionation reaction.3 marks