Question

The lattice energy of $NaCl$ is $788 \,kJ \, mol^{-1}$. This means that $788\, kJ$ of energy is required

• A. to separate one mole of solid NaCl into one mole of $Na_{(g)}$ and one mole of $Cl_{(g)}$ to infinite distance
• B. to separate one mole of solid $NaCl$ into one mole of $Na_{(g)}^{+}$ and one mole of $Cl_{(g)}^{-}$ to infinite distance
• C. to convert one mole of solid $NaCl$ into one mole of gaseous $NaCl$
• D. to convert one mole of gaseous $NaCl$ into one mole of solid $NaCl$

Answer 1

Answer: (B)

Lattice energy is that amount of energy which is required to separate one mole of a solid into its constituents gaseous ions at infinite distances.

Since the lattice energy of $NaCl$ is $788\, kJ\, mol ^{-1}$, it meas that $788\, kJ$ of energy is required to separate one mole of solid $NaCl$ into one mole of $Na ^{+}(g)$ and one mole of $Cl ^{-}(g)$ to infinite distance.