Question

Question 46: The lattice energy of${\mathbf{FeCI}}_{\mathbf{3}}\mathbf{,}{\mathbf{FeCI}}_{\mathbf{2}}$and${\mathbf{Fe}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{2}}$are (in no particular order) -2631KJ/mol, -5339KJ/mol and -14,774KJ/mol match the appropriate formula to each lattice energy.

Short answer

Lattice energy: -The energy released when the requisite number of positive and negative ions are condensed into the crystal to form one mole of the compound is called lattice energy. The higher the lattice energy greater will be the ease of forming an ionic compound.

Step-by-step solution

The greater charged ions form a compound with higher exothermic energy than the smaller charged ion.

The given compound are formed by the following ions

$$\begin{gathered} {\mathrm{FeCI}}_3\to {\mathrm{Fe}}^{3+}+3{\mathrm{CI}}^{-} \\ {\mathrm{FeCI}}_2\to {\mathrm{Fe}}^{2+}+2{\mathrm{CI}}^{-} \\ {\mathrm{Fe}}_2{\mathrm{O}}_3\to 2{\mathrm{Fe}}^{3+}+3{\mathrm{O}}^{2-} \end{gathered}$$

The compound${\mathrm{Fe}}_2{\mathrm{O}}_3$ is most exothermic because it has $2{\mathrm{Fe}}^{3+}$and$+3{\mathrm{O}}^{2-}$ .

The cation and anionic charges on the compound FeCI3,FeCI2and Fe2O2 are (+3, -1), (+2, -1), (+6, -6)

Therefore

${\mathrm{FeCI}}_3$will have lattice energy $\to$-5339 KJ/mol

${\mathrm{FeCI}}_2$will have lattice energy $\to$-2631 KJ/mol

${\mathrm{Fe}}_2{\mathrm{O}}_3$will have lattice energy $\to$-14774 KJ/mol