CIE Jun 2016 v2 Paper 2 Q2

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PMT The elements in Group 17, the halogens, and their compounds, show many similarities and trends in their properties. Some data are given for the elements fluorine to iodine. element bond energy / kJ mol1 standard enthalpy change of atomisation, / kJ mol1 boiling point of element / K boiling point of hydrogen halide / K fluorine, FF chlorine, Cl Cl bromine, BrBr iodine, II 158 242 193 151 79 121 112 107 85 238 332 457 293 188 206 238 (a) (i) Explain the meaning of the term standard enthalpy change of atomisation.[3] (ii) For fluorine and chlorine, the enthalpy changes of atomisation are half the value of the bond energies. For bromine and iodine, the enthalpy changes of atomisation are much more than half the value of the bond energies. Suggest a reason for this difference.[1] (iii) The standard enthalpy of formation of iodine monochloride, ICl, is 24.0 kJ mol1. Use this information and the bond energies of iodine and chlorine to calculate the ICl bond energy. ICl bond energy =kJ mol1 [2]UCLES 2016 9701/22/M/J/16<br /> PMT (b) (i) Explain the trend in the boiling points of the hydrogen halides, HCl, HBr and HI.[2] (ii) Suggest why the hydrogen halide HF does not follow the trend in boiling points shown by HCl, HBr and HI.[2] (c) In an experiment, two of the halogens are represented as P2 and Q2. P2 combines with hydrogen on heating to form HP, which can be easily broken down into its elements. A solution of HP in water reacts with aqueous silver ions to form a yellow precipitate that is insoluble in dilute aqueous ammonia. Q2 combines explosively with hydrogen in sunlight to form HQ, which is stable to heat. A solution of HQ in water reacts with aqueous silver ions to form a white precipitate that is soluble in dilute aqueous ammonia. (i) Identify the halogens P2 and Q2. P2 =Q2 =[1] (ii) HP readily decomposes into its elements when heated but HQ is stable to heat. Explain this with reference to bond energies.[2] (iii) Write an equation for the thermal decomposition of HP.[1]UCLES 2016 9701/22/M/J/16 [Turn over<br /> PMT (iv) Write ionic equations, including state symbols, for 1. the formation of the white precipitate on addition of aqueous silver ions to aqueous HQ,2. the subsequent dissolving of this precipitate in dilute aqueous ammonia.[2] (d) Chlorine reacts directly with many elements to form chlorides. Three such compounds are MgCl 2, Al Cl 3 and SiCl 4. (i) State and explain the pattern shown by the formulae of these three chlorides.[2] (ii) Write equations to show the behaviour of each of these chlorides when added to water. MgCl 2Al Cl 3SiCl 4[3] [Total: 21]UCLES 2016 9701/22/M/J/16<br />

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