Question

Consider the following information. The lattice energy of CsCl is Δ H lattice = − 657 kJ/mol. The enthalpy of sublimation of Cs is Δ H sub = 76.5 kJ/mol. The first ionization energy of Cs is IE 1 = 376 kJ/mol. The electron affinity of Cl is Δ H EA = − 349 kJ/mol. The bond energy of Cl 2 is BE = 243 kJ/mol. Determine the enthalpy of formation, Δ H f , for CsCl ( s ) .

Answer 1

Answer:

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Explanation:

Answer 2

Answer:

-310.5 kJ/mol

Explanation:

The CsCl(s) will be formed by steps:

• The metal (Cs) will be made gaseous by a sublimation → ΔHsub = 76.5 kJ/mol;

• The metal gains energy to ionize → IE = 376 kJ/mol;
• The nonmetal (Cl) loses energy to ionizes → EA = -349 kJ/mol;
• The nonmetal is bonded → BE = 243 kJ/mol;
• The lattice is formed → ΔHlattice = -657 kJ/mol.

The enthanlpy of formation is the sum of all the energies involved in the steps:

ΔHf = 76.5 + 376 -349 + 243 -657

ΔHf = -310.5 kJ/mol