Ass7[1]

# Ass7[1] - ASSIGNMENT 7 Practice drawing Born-Haber cycles...

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ASSIGNMENT 7 Practice drawing Born-Haber cycles for forming CsI, Aluminum sulfide, Aluminum iodide, magnesium oxide. Sodium sulfate, calcium bromide etc .You should be able to explain why certain compounds will not be formed using the central idea of Born Haber cycle. Some useful data from my file; delta H Formation (kJ/mol) Solid Li) *0 Gas (Li) *159.3 ± Li + (g) 687.163 Li + (aq) -278.46 Solid Na 0(kJ/mol) Na(g) 107.6 Na + (g) 609.83 Na + (aq) -239.6 Solid Al 0 Al(g) 334 Al 3+ (g) you should look this up in your Notes Delta H hydration (Al) -4680 kJ/mol Solid Ag 0 Ag(g) 289.2 Ag + (g) 731 Delta H (hyd) 468 Solid Mg 0 Mg(g) 150 Mg 2+ (g) 2351 Mg 2+ (aq) -461.96 . Solid Cs 0 Cs(g) 76.7 Cs + (g) 458.5 Cs + (aq) -248 The following web site is useful to obtain all sorts of data; Explore; http://www.webelements.com/

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1. Consider the hypothetical ionic compound NeCl. Construct a Born-Haber Cycle which will enable you to calculate the standard enthalpy of formation of this compound. Calculate a reasonable value for the heat of formation and explain all the assumptions you have made. From your calculations would you expect this compound to exist? The Ne - ion has been predicted to have a radius similar to that of I - and there fore the crystal lattice energy should be similar. Use the approx values below to calculate the heat of formation of CsNe. Heat of sublimation of iodine solid = +62 kJ/mol Bond energy of iodine = 45 kJ/mol EA of iodine = -295 kJ/mol EA of neon = +31 kJ/mol Heat of formation of CsI = -347 kJ/mol Heat of formation of Cs(Solid) = 0 Heat of formation fo Cs(g) = 76.5 kJ/mol IE(1) of Cs = 375.7 kJ/mol 1b). The value of ΔS 0 for the reaction: M(s) + X(g) M n+ X n- (s) are similar for many reaction at -142
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Ass7[1] - ASSIGNMENT 7 Practice drawing Born-Haber cycles...

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