10 5 This question is about the reactions of the halogens and halide ions. (a) (i) When chlorine gas is bubbled through an aqueous solution of potassium iodide, the reaction involves (1) A oxidation only B reduction only C redox D disproportionation (ii) Cyclohexane was added to the resulting solution from (a)(i). The mixture was shaken and then allowed to stand for a few minutes. Two layers were formed. [ Density: aqueous layer solution = 1.10 g cm–3, cyclohexane layer = 0.78 g cm–3] The colour of the lower layer was (1) A pale yellow B purple C red D pale green (b) Concentrated sulfuric acid was added to a small quantity of solid potassium iodide in a test tube. (i) In this exothermic reaction, which of the following mixtures of gases would be produced? (1) A hydrogen iodide and sulfur dioxide only B hydrogen iodide and hydrogen sulfide only C hydrogen iodide, sulfur dioxide and hydrogen sulfide D hydrogen iodide, hydrogen sulfide and iodine 11 Turn over (ii) Hydrogen iodide is a gas which reacts in a similar way to hydrogen chloride. State the observation when the hydrogen iodide gas is passed over the mouth of an open bottle of concentrated ammonia solution. Write an equation, including state symbols, for the reaction. (3) Observation ................................................................................................................................................................................................................................................. Equation (c) Potassium iodate(V) can be prepared by adding solid iodine to a hot aqueous solution of potassium hydroxide. The equation for the reaction is 3I2 + 6KOH → KIO3 + 5KI + 3H2O Potassium iodate(V) can be separated from the other reaction product using their differing solubilities in water. Solubility in water at 25 °C / mol dm–3 KI 8.92 KIO3 0.43 (i) Outline a procedure that you could use to obtain a sample of dry, solid potassium iodate(V) from the reaction mixture. (3) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... 12 (ii) Describe how you would show that iodide ions are present in an aqueous solution of potassium iodide. (2) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (d) Fluorine is an element in Group 7. Group 7 includes the elements chlorine, bromine and iodine. Some information about the melting and boiling temperatures of Group 7 elements is shown in the table. Element Melting temperature / K Boiling temperature / K chlorine 172 238 bromine 266 332 iodine 387 457 Which is the expected boiling temperature of fluorine, in kelvin, K? (1) A 4 B 85 C 575 D 610 (Total for Question 5 = 12 marks) 13 Turn over BLANK PAGE