Question

Consider an ionic compound, MX, composed of generic metal M and generic, gaseous halogen X. The enthalpy of formation of MXis ΔH∘f=−427kJ/mol. The enthalpy of sublimation of Mis ΔHsub=135kJ/mol. The ionization energy of Mis IE=433kJ/mol. The electron affinity of Xis ΔHEA=−307kJ/mol. (Refer to the hint). The bond energy of X2is BE=175kJ/mol. Determine the lattice energy of MX.

Answer 1

The lattice energy of MX is -523.5 kJ/mol.

Step-by-step explanation:

`M(s)+(1)/(2)X_2(g)\rightarrow MX(s),\Delta H_f=-427kJ/mol`....[1]

`M(s)\rightarrow M(g),\Delta H_(sub)=135kJ/mol`....[2]

`M(g)\rightarrow M^+(g)+1e^-,I.E=433kJ/mol`....[3]

`X(g)+e^-\rightarrow X^-(g),E.A=-307kJ/mol`....[4]

`X_2(g)\rightarrow 2X(g), \Delta H_(X-X)=175kJ/mol`....[5]

`M^+(g)+X^-(g)\rightarrow MX(s),L.E=?`....[6]

[1] = [2] + (1/2)[5] + [6] - [3] - [4]

`-427kJ/mol = 135kJ/mol +(1)/(2)* 175kJ/mol+L.E- (433kJ/mol) - (-307kJ/mol)`

`-427kJ/mol=96.5 kJ/mol+L.E`

`L.E=-523.5 kJ/mol`

The lattice energy of MX is -523.5 kJ/mol.