Question

lattice energy sodium chloride is 'x'kJ. Assuming the same interionic distance what will be the lattice energy of magnesium sulfide

Answer 1

The charge magnitudes of ion is NaCl are 1 and 1 respectively.

The product of q1 and q2 = 1 × 1 = 1

The charge magnitudes of ions in magnesium sulphide are 2 and 2 respectively.

The product of q1 and q2 = 2 × 2 = 4

Hence lattice energy in MgS = 4x kJ.

Answer 2

Hence the lattice energy of MgS is x KJ.

Given:

The lattice energy of sodium chloride is 'x'kJ.

To find:

Assuming the same interionic distance the lattice energy of magnesium sulfide.

Solution:

The lattice energy is given as follows-

U=kq1×q2/r.

Where k is the constant, q1 and q2 are charges of cation and anion respectively.

r is the interionic distance.

Thus NaCl dissociate as-

$NaCl\rightarrow Na^++Cl^-$.

Thus MgS dissociate as-

$MgS\rightarrow Mg^{+2}+S^{2-}$.

For NaCl, we can write-

Ub=k×1×1/r

k/r=x as Ub=x.

For MgS, we can write-

Ua=k×2×2/r

So, we can write-

Ua=4×k/r

Ua=4×x.

Hence the lattice energy of MgS is x KJ.