CIE Jun 2014 v3 Paper 2 Q4

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PMT The halogens and their compounds have a wide variety of uses and the chemical and physical properties of the elements show regular patterns related to their positions in Group VII. (a) Chlorine, bromine and iodine all react with hydrogen. (i) State the trend in the reactivities of the halogens with hydrogen.[1] (ii) Explain this trend in terms of bond energies.[2] (b) In the laboratory it is not very convenient to prepare hydrogen halides from their elements. Hydrogen halides can be prepared from their salts. (i) Write an equation for the reaction of calcium chloride, CaCl 2, with concentrated sulfuric acid.[1] (ii) Explain why hydrogen iodide is not prepared in this way.[1] (iii) When potassium bromide, KBr, reacts with concentrated sulfuric acid, sulfur dioxide, SO2, is produced. State what you would see and write an equation for this reaction.[3]UCLES 2014 9701/23/M/J/14<br /> (c) (i) Give the structures of the four structural isomers of C4H9Br and identify each as primary, secondary or tertiary. PMT[4] (ii) Name the isomer of C4H9Br that contains a chiral centre and draw the three-dimensional structures of the two optical isomers. namestructures [3] (d) Aqueous silver nitrate solution was added to separate tubes containing chloroethane, bromoethane and iodoethane. The tubes were heated in a water bath. A yellow precipitate appearedrst in the tube containing iodoethane, followed by a cream precipitate in the tube containing bromoethane andnally a white precipitate appeared in the tube containing chloroethane. Explain these observations.[2]UCLES 2014 9701/23/M/J/14 [Turn over<br /> PMT 10 (e) (i) Give the full name of the mechanism for the reaction between aqueous sodium hydroxide and bromoethane.[2] (ii) Complete the diagram below to represent this mechanism. Include all necessary curly arrows, partial charges and lone pairs. Br OH + BrHO [2] (f) In the past, CFCs such as CF3Cl were widely used as refrigerants. (i) State a property of CFCs which makes them suitable for use as refrigerants.[1] (ii) State the damaging effect of CFCs in the upper atmosphere.Explain your answer.[2] [Total: 24]UCLES 2014 9701/23/M/J/14<br />

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