The first IE of lithium is 5.41eV and first electron affinity of Cl is 3.61eV. Calculate ΔH (nearest integer value) in kJmol−1 for the reaction Li(g)+Cl(g)⟶Li+(g)+Cl−(g)
[Take nearest integer]
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Solution
ΔHmolecule of Li+\ Cl−=IE1Li+Ega1Cl=5.41−3.61=1.80eV ∵Li⟶Li++e;IE1=−ve and Cl+e⟶Cl−;Ega1=−ve ∴ΔH/mol=1.8×6.023×1023eV=1.8×6.023×1023×1.602×10−19J =1.8×6.023×1023×1.602×10−19×10−3kJ =173.7kJ