Question

The enthalpy of solution of sodium chloride is $4\, kJ\, mol^{-1}$ and its enthalpy of hydration of ions is $ -784\, kJ \,mol^{-1}$. What will be the lattice enthalpy of sodium chloride?

• A. $+780 \,kJ\, mol^{-1}$
• B. $+394\,kJ\, mol^{-1}$
• C. $+788\,kJ\, mol^{-1}$
• D. $+398\,kJ\, mol^{-1}$

Answer 1

Answer: (C)

$\Delta H_{sol} = \Delta H_{lattice}+\Delta H_{hyd}$
$4 = \Delta H_{lattice} + \left(-784\right)$
$\Delta H_{lattice} = 4-\left(-784\right)$
$= + 788\,kJ\,mol^{-1}$