Question

Which of the following statements is incorrect regarding lattice energy?

• A. Lattice energy is inversely proportional to the size of an ion.
• B. Greater is the charge on the ions, more is the lattice energy.
• C. Lattice energy for $KCl$ is greater than $CaC{l}_2$.
• D. Formation of ionic bond depends upon the ionisation energy of cation, electron gain energy of anion and lattice energy.

Answer 1

The correct option is C Lattice energy for $KCl$ is greater than $CaC{l}_2$.

$L.E=\frac{k.q_1.q_2}{r}$
where, $k$ = proportionality constant,
$q_1,q_2$ are the charges on the ions and
$r$ is the shortest distance between the centers of cations and anions.

So, lattice energy is proportional to the charge on the ions and inversely proportional to the size of ions. Also, between charge and size, charge is the dominating factor.

Lattice energy of $CaC{l}_2$ is greater than $KCl$. Anion is same in both the compounds. So, the deciding factor here becomes the charge. Calcium ion carries a charge of $+2$ while potassium,charge of $+1$.