The lattice energy of cesium chloride is the energy required for the following r

Question

The lattice energy of cesium chloride is the energy required for the following reaction. CsCI(s)rightarrow Cs^+ (g) + Cl^-(g) delta H_rxn =delta H_lattice Use the Born-Haber cycle to calculate delta| H_lattice for CsCl(s) from the information given below. kJ/mol Equation 1: 2 Cs (s) + Cl_2 (g) rightarrow 2 CsCl (s) delta H_1 = -885 kJ/mol Equation 2: Cs (s) rightarrow Cs (g) delta H_2 = 77 kJ/mol Equation 3: Cl_2 (g) rightarrow 2 Cl (g) delta H_3 = 243 kJ/mol Equation 4: Cs (g) rightarrow Cs^+ (g) + e^- delta H_4 = 376 kJ/mol Equation 5: Cl (g) + e^- rightarrow Cl^- (g) delta H_5 = -348 kJ/mol

Explanation / Answer

Required reaction CsCl (s) ---------------> Cs+ (g) + Cl- (g)

Reverse the equation (1) and divide with coefficient 2 :

Cs+ (g) + Cl- (g) -------------> Cs(s) + 1/2 Cl2 (g) new H1 = + 885/2 kJ/mol = + 442.5 kJ/mol

Write equation 2 same as given :

Cs (s) -----------> Cs(g)    H2 = 77 kJ/mol

Divide the equation 3 with coefficient 2:

1/2 Cl2 (g) ----------> Cl (g)     new H3 = 243/2 kJ/mol = 121.5 kJ/mol

Write equation 4 same as given :

Cs(g) ------------> Cs(g) + e-    H4 = 376 kJ/mol

Write equation 5 same as given :

Cl(g) + e- ------------> Cl- (g) H5 = -348 kJ/mol

Hence,

Reverse the equation (1)/2 + eq (2) + eq (3)/2 + eq (4) + eq(5) gives

CsCl (s) ---------------> Cs+ (g) + Cl- (g)

  Hrxn =  new H1 + H2 + new H3 + H4 + H5

   = + 442.5 kJ/mol + 77 kJ/mol + 121.5 kJ/mol + 376 kJ/mol - 348 kJ/mol

= + 669 kJ/mol

Therefore,

Lattice energy of CsCl = + 669 kJ/mol

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