The lattice energy of solid NaCl is 180 kcal/mol. The dissolution of the solid in water in the form of ions is endothermic to the extent of 1 kcal/mol. If the hydration energies of Na + and Cl - are in the ratio 6 : 5, what is the enthalpy of hydration of Na + ion ?

Question

The lattice energy of solid NaCl is 180 kcal/mol. The dissolution of the solid in water in the form of ions is endothermic to the extent of 1 kcal/mol. If the hydration energies of Na + and Cl - are in the ratio 6 : 5, what is the enthalpy of hydration of Na + ion ?, - 8.5 kcal mol -1, - 97.64 kcal mol -1, + 82.6 kcal mol -1, + 100 kcal mol -1

MARKS App · Accepted Answer

Δ H solu = Δ H hydration + Δ H Lattice 1 = Δ H hydration + 1 8 0 Δ H hydration = - 1 7 9 kcal mol - 1 Δ H hyd Na + + Δ H hyd cl - = -1 7 9 kcal mol - 1 Δ H hyd Na + = - 1 7 9 × 6 1 1 = - 9 7 · 6 4 kcal mol - 1

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