The heat of sublimation of potassium is 98kJ/mol. The heat of dissociation of bromine gas is 192.5 kJ/mol. The ionization energy of K is 414 kJ/mol. The electron affinity of Br -334.7kJ/mol and the heat of formation of KBr is -405.8 kJ/mol. Calculate the lattice energy of KBr
Correct answer: A. -679.3
- A. -679.3
- B. -669.5
- C. 669.5
- D. 679.3
Explanation
By applying Hess's lawΔHf=ΔHsubl+ΔHdiss+ΔHIE+ΔHEA+U (U is the lattice energy)The lattice energy of KBr is approximately 679.35 kJ/mol (the negative sign indicates that energy is released when the lattice forms).
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About Thermochemistry and Energetics of Chemical Reactions
Thermochemistry measures energy changes in chemical reactions and distinguishes exothermic from endothermic processes. Work covers systems, surroundings and state functions, internal energy, the first law of thermodynamics, enthalpy and Hess's law, including the sign conventions used when heat enters or leaves a system.
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