1. 1
   A technician sets out three labelled gas jars for a school demonstration on the halogens. Jar 1 contains chlorine, Jar 2 contains bromine and Jar 3 contains iodine. The technician records the colour and physical state of each substance at room temperature, then bubbles chlorine gas through separate aqueous solutions of potassium bromide and potassium iodide to observe any colour changes.

   (a)

   What is the physical state of chlorine, bromine and iodine, respectively, at room temperature?

   [1 mark]

   • AChlorine is a gas, bromine is a liquid, iodine is a solid
   • BChlorine is a liquid, bromine is a gas, iodine is a solid
   • CChlorine is a solid, bromine is a liquid, iodine is a gas
   • DChlorine, bromine and iodine are all gases

   (b)

   When chlorine gas is bubbled through aqueous potassium iodide solution, the solution turns from colourless to brown. What does this observation show?

   [1 mark]

   • AChlorine has dissolved in the water without reacting with the potassium iodide
   • BIodine has displaced chlorine from the solution because iodine is more reactive than chlorine
   • CNo reaction has occurred and the colour change is due to the potassium ions
   • DChlorine has displaced iodine from potassium iodide because chlorine is more reactive than iodine

   (c)

   Predict, with a reason, what would happen if the technician bubbled bromine gas through an aqueous solution of potassium iodide.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student investigates the reactions of chlorine gas as part of a coursework task. She first tests a sample of the gas with damp litmus paper. She then reacts separate samples of chlorine gas with heated sodium metal and with heated iron wool, collecting and naming the solid products formed in each case.

   (a)

   A student holds a piece of damp blue litmus paper at the mouth of a test tube containing chlorine gas. What is the correct chemical test result for chlorine?

   [1 mark]

   • AThe litmus paper turns from blue to red and stays red
   • BThe litmus paper turns white/is bleached
   • CThe litmus paper produces a 'pop' sound
   • DThe litmus paper turns from blue to green

   (b)

   When chlorine gas reacts with heated sodium metal, which product is formed?

   [1 mark]

   • ASodium oxide
   • BSodium chlorate
   • CSodium chloride
   • DSodium hydroxide

   (c)

   Name the product formed when chlorine gas reacts with heated iron wool, and describe how this reaction supports the general pattern of halogen reactions with metals.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A group of students studies the hydrogen halides formed by the halogens. They react hydrogen gas separately with chlorine, bromine and iodine to form hydrogen chloride, hydrogen bromide and hydrogen iodide, then dissolve each product in water and test the resulting solutions with universal indicator. They also compare these results with data on the reactivity of the three halogens in displacement reactions with halide salts.

   (a)

   A student reacts hydrogen gas with chlorine gas to form hydrogen chloride, which is then dissolved in water. Describe what type of solution is formed and explain why, in terms of the type of compound formed.

   [3 marks]

   (b)

   Astatine is a halogen below iodine in Group 7 that the students have not been able to test directly. Using the trend in reactivity shown by chlorine, bromine and iodine, predict how astatine would react in a displacement reaction with sodium chloride solution, and explain your prediction in terms of electronic configuration.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A technician carries out a series of displacement reactions to compare the reactivity of the halogens. She adds chlorine water to separate aqueous solutions of potassium bromide and potassium iodide, and observes colour changes in both cases. She records her observations and then asks a group of students to explain the results in terms of electron transfer and relative reactivity.

   (a)

   A technician adds chlorine water to an aqueous solution of potassium bromide. A colour change from colourless to orange is observed, showing that bromine has been displaced. Explain, in terms of electron transfer, why this is described as a redox reaction, identifying clearly which species is oxidised and which is reduced, and write an ionic equation for the reaction.

   [6 marks]

   (b)

   The technician repeats the experiment but adds iodine water to an aqueous solution of potassium chloride, and observes no colour change or reaction. Explain this result fully in terms of the relative reactivity of the halogens and their electronic configurations, and describe how the pattern in reactivity down Group 7 could be used to predict the outcome of a reaction between fluorine and potassium chloride solution.

   [6 marks]

   Total for question 4: 12 marks

End of questions