A-level Chemistry PapSol Q 8-11 

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8 (b) Suggest, with an explanation, how the lattice energies of the following salts might compare in magnitude with that of calcium chloride.
 (i) calcium fluoride, CaF2 

 (ii) calcium sulfide, CaS 

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9(c) Use the following data, together with additional data from the Data Booklet, to calculate the lattice energy of CaCl 2. standard enthalpy change of formation of CaCl 2 –796 kJ mol–1 standard enthalpy change of atomisation of Ca(s) +178 kJ mol–1 electron affinity per mole of chlorine atoms –349 kJ mol–1 enthalpy Ca(s) + Cl 2(g) lattice energy = ............................................ kJ mol–1 [3]
(c) (i) Use the following data and data from the Data Booklet to construct a Born-Haber cycle and calculate the lattice energy of BaS.
Solution:
 



 lattice energy = ............................. kJ mol–1
 (ii) Explain whether the magnitude of the lattice energy of BaS is likely to be greater or less than that of BaO. .................................................................................................................................. .................................................................................................................................. [4]

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4 (a) What is meant by the term bond energy? .......................................................................................................................................... ......................................................................................................................................[2]
 (b) Describe and explain what is observed when a red-hot wire is plunged into separate samples of the gaseous hydrogen halides HCl and HI. How are bond energy values useful in interpreting these observations? .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[3]
 (c) The following reaction occurs in the gas phase. 3F2(g) + Cl 2(g) 2ClF3(g), ∆H o— r = –328 kJ mol–1 Use these and other data from the Data Booklet to calculate the average bond energy of the Cl-F bond in Cl F3. [2]


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5 (b) Calculate the lattice energy of magnesium nitride using the following data, in addition to relevant data from the Data Booklet.