Question

Lattice energy of NaCl is 'X'. If the ionic size of A2+ is equal to that of Na+ and B2- is equal to Cl-, then lattice energy associated with the crystal AB is

Answer 1

Answer: The lattice energy of crystal AB is 4X.

Explanation: Lattice energy is the energy associated to the crystal lattice of a compound.

Mathematically,

$E_{lattice}=k\frac{Q_1Q_2}{d}$

where, k = proportionality constant

$Q_1\text{ and }Q_2$ are the charges on the ions in coulombs

d =  distance between the ion charges.

Lattice energy of NaCl = X

$E_{lattice}(NaCl)=\frac{Q_1Q_2}{d}=X$

As the ionic size remains same when AB crystal is formed, d remains same

Lattice energy of AB,

$E_{lattice}(AB)=\frac{(2Q_1)(2Q_2)}{d}$

$E_{lattice}(AB)=4\left(\frac{Q_1Q_2}{d}\right )=4X$

The lattice energy of crystal AB is 4X.

Answer 2

Explanation:

the lattice energy of crystal ab is 4X