The elements in Group 17, the halogens, show trends in both their chemical and physical properties. The elements and their compounds have a wide variety of uses.

1. (a)(i)At room temperature fluorine and chlorine are gases, bromine is a liquid and iodine is a solid. State the trend in the volatility of the Group 17 elements down the group.[1]
2. (a)(ii)Explain this trend.[2]
3. (b)Iodine, I₂, can be displaced from NaI(aq), by chlorine, Cl₂. Write an equation for this reaction.[1]
4. (c)(i)Silver nitrate solution, AgNO3(aq), is added to separate solutions of NaI and NaCl. Precipitates form. An excess of aqueous ammonia is then added to both precipitates. Complete the table to give the colour and name of the precipitate formed in each reaction and the effect of the addition of an excess of aqueous ammonia to each of the precipitates formed.[3]
5. (c)(ii)Write an ionic equation, including state symbols, to show the reaction occurring when AgNO3(aq) is added to NaI(aq).[1]
6. (d)Solid NaI reacts with concentrated sulfuric acid to form purple fumes of I₂(g) and hydrogen sulfide gas, H₂S(g). However, when solid NaCl reacts with concentrated sulfuric acid the only gas produced is HCl(g). Explain the difference in the reactions of concentrated sulfuric acid with NaI and with NaCl. Your answer should refer to the role of the sulfuric acid in each reaction.[3]
7. (e)(i)Chlorine is commonly used in water purification. When chlorine is added to water it reacts to produce a mixture of acids, one of which is chloric(I) acid, HClO, a powerful oxidising agent. Explain the meaning of the term oxidising agent, in terms of electron transfer.[1]
8. (e)(ii)Suggest an equation for this reaction of chlorine with water.[1]
9. (e)(iii)Write an equation for the reaction of chlorine with hot aqueous sodium hydroxide. Use oxidation numbers to explain why this is a redox reaction.[2]

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