1. 1
   A leisure centre adds chlorine gas to swimming pool water to kill harmful bacteria, and a maintenance worker also tests the water by adding it to solutions containing other halide ions to check for contamination.

   (a)

   At room temperature, what is the colour and physical state of chlorine?

   [1 mark]

   • AA dense orange-brown liquid
   • BA pale green-yellow gas
   • CA dark grey solid
   • DA colourless gas

   (b)

   The maintenance worker adds a small amount of chlorine water to a colourless solution of potassium bromide and the solution turns orange. Which type of reaction has occurred?

   [1 mark]

   • AA precipitation reaction forming solid potassium chloride
   • BA displacement reaction, in which bromine displaces chlorine from potassium bromide
   • CA neutralisation reaction between chlorine and potassium bromide
   • DA displacement reaction, in which chlorine displaces bromine from potassium bromide

   (c)

   Write a word equation for the reaction between chlorine and potassium bromide solution, and explain why this reaction takes place in terms of the relative reactivity of chlorine and bromine.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A laboratory technician handles a sample of bromine in a fume cupboard, since it gives off harmful, choking fumes, and later tests its reaction with a solution of potassium iodide.

   (a)

   A laboratory technician handles bromine in a fume cupboard because it gives off harmful, choking fumes. At room temperature, what is bromine's physical state and colour?

   [1 mark]

   • AA dark grey, shiny solid
   • BA pale green-yellow gas
   • CA dense, red-brown liquid
   • DA colourless liquid

   (b)

   The technician adds bromine water to a colourless solution of potassium iodide and the solution turns dark brown/black. Which statement correctly explains this observation?

   [1 mark]

   • AIodine is more reactive than bromine, so it displaces bromine from potassium iodide
   • BBromine is more reactive than iodine, so it displaces iodine from potassium iodide, forming iodine and potassium bromide
   • CBromine and iodine do not react, and the colour change is caused by evaporation of the water
   • DPotassium iodide decomposes on its own when bromine water is added, releasing potassium metal

   (c)

   Write a word equation for the reaction between bromine and potassium iodide solution, and explain in terms of electronic configuration why bromine is more reactive than iodine.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student carries out a series of displacement tests, adding chlorine water, bromine water and iodine solution in turn to separate samples of potassium chloride, potassium bromide and potassium iodide solutions, and records which combinations produce a colour change.

   (a)

   Explain how the pattern of results from these tests can be used as evidence for the trend in reactivity down Group 7.

   [3 marks]

   (b)

   The student then predicts what would happen if iodine solution were added to potassium chloride solution. Predict the result of this test and explain your reasoning in terms of the reactivity trend and electronic configuration.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A chemistry teacher asks students to predict the physical state, colour and relative reactivity of astatine, a Group 7 element that lies below iodine, without carrying out any experiments, since astatine is extremely rare and highly radioactive.

   (a)

   Using the trends observed across chlorine, bromine and iodine, predict and explain the properties you would expect astatine to have.

   [6 marks]

   (b)

   The teacher then asks students to explain why all the halogens react in broadly similar ways with metals, despite their differing reactivities, and to describe how this relates to their position in the Periodic Table. Use ideas about electronic configuration in your answer.

   [6 marks]

   Total for question 4: 12 marks

End of questions