Below is a list of enthalpy changes for the Born-Haber cycle for the formation of solid LiF from Li(s) and F(g). Use these data to determine the lattice energy for the formation LiF(s). Li(s) → Li(g) ΔH1 = +162 kJ/mol Li(g) → Li+(g) + e- ΔH2 = +520.2 kJ/mol F2(g) → 2F(g) ΔH3 = 154 kJ/mol F(g) + e- → F-(g) ΔH4 = -328 kJ/mol Li(s) + 1/2F2(g) → LiF(s) ΔHf = -612 kJ/mol Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a. 1371 kJ/mol b. -1371 kJ/mol c. 1043 kJ/mol d. -1043 kJ/mol
Thermochemistry
Thermochemistry can be considered as a branch of thermodynamics that deals with the connections between warmth, work, and various types of energy, formed because of different synthetic and actual cycles. Thermochemistry describes the energy changes that occur as a result of reactions or chemical changes in a substance.
Exergonic Reaction
The term exergonic is derived from the Greek word in which ‘ergon’ means work and exergonic means ‘work outside’. Exergonic reactions releases work energy. Exergonic reactions are different from exothermic reactions, the one that releases only heat energy during the course of the reaction. So, exothermic reaction is one type of exergonic reaction. Exergonic reaction releases work energy in different forms like heat, light or sound. For example, a glow stick releases light making that an exergonic reaction and not an exothermic reaction since no heat is released. Even endothermic reactions at very high temperature are exergonic.
Li(s) → Li(g) ΔH1 = +162 kJ/mol
Li(g) → Li+(g) + e- ΔH2 = +520.2 kJ/mol
F2(g) → 2F(g) ΔH3 = 154 kJ/mol
F(g) + e- → F-(g) ΔH4 = -328 kJ/mol
Li(s) + 1/2F2(g) → LiF(s) ΔHf = -612 kJ/mol
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