Using the following data, calculate the lattice energy of calcium chloride: Ca2+(g) + 2Cl– (g) → CaCl2(s) ΔHlattice = ? Sublimation enthalpy of calcium ΔH = 177.8 kJ/mol First ionization energy of calcium ΔH = 590.2 kJ/mol Second ionization energy of calcium ΔH = 1144.2 kJ/mol First electron affinity of chlorine ΔH = –349 kJ/mol Heat of formation of CaCl2(s) ΔH = –795.4 kJ/mol Bond energy of Cl2 (see Table 2) Use Hess’s law to calculate the lattice energy of calcium chloride. set-up must show all the chemical equations and you must show how their H values add up to give your answer.
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.
Using the following data, calculate the lattice energy of calcium chloride:
Ca2+(g) + 2Cl– (g) → CaCl2(s) ΔHlattice = ?
Sublimation enthalpy of calcium ΔH = 177.8 kJ/mol
First ionization energy of calcium ΔH = 590.2 kJ/mol
Second ionization energy of calcium ΔH = 1144.2 kJ/mol
First
Heat of formation of CaCl2(s) ΔH = –795.4 kJ/mol
Bond energy of Cl2 (see Table 2)
Use Hess’s law to calculate the lattice energy of calcium chloride. set-up must show all the chemical equations and you must show how their H values add up to give your answer.
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