Question

The enthalpy of solution of sodium chloride is `4 kJ mol^(-1)` and its enthalpy of hydration of ion is `-784 kJ mol^(-1)`. Then the lattice enthalpy of `NaCl` (in `kJ mol^(-1)`) is
A. `+788`
B. `+4`
C. `+398`
D. `+780`

Answer 1

Correct Answer - A
`DeltaH_("solution")=DeltaH_("Lattice")+Delta_("Hydration")`
or `+4=DeltaH_("lattice")+(-784)`
or `DeltaH_("lattice")=788 kJ mol^(-1)`