Then, use the Born–Haber cycle to obtain the value of lattice energy for PbS. You will need the following data following data : ΔH Pb(g) = 196 kJ/mol; ΔHf PbS = –98 kJ/mol; electron affinities for S(g)→S- (g) is -201 kJ/mol; ) S- (g) →S2-(g) is 640kJ/mol. Ionization energies for Pb are listed in Resourc
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.
Use Born-Mayer equation to calculate the lattice energy for PbS (it crystallizes in the
NaCl structure). Then, use the Born–Haber cycle to obtain the value of lattice energy for PbS.
You will need the following data following data : ΔH Pb(g) = 196 kJ/mol; ΔHf PbS = –98
kJ/mol;
energies for Pb are listed in Resource section 2, p.903. Remember that enthalpies of formation
are calculated beginning with the elements in their standard states (S8 for sulfur). Diatomic
sulfur, S2, is formed from S8 (ΔHf: S2 (g) = 535 kJ/mol.
Can you just do the Born-Haber part?
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