Question

The ${\text{L}}{{\text{i}}_{\text{2}}}{\text{O}}$ is more stable than ${\text{L}}{{\text{i}}_{\text{2}}}{\text{C}}{{\text{O}}_{\text{3}}}$.
State whether the statement is true or false.

Answer 1

Hint: We will determine the thermodynamic stability of the lithium oxide and lithium carbonate. Thermodynamics stability is directly proportional to the lattice energy. Lattice energy is directly proportional to the charge and inversely proportional to the size.

Complete answer :
The thermodynamics stability of the oxides and carbonated depends upon the lattice energy. On increasing the lattice energy thermodynamics stability increases.

Thermodynamics stability $ \propto $ Lattice energy.

Lattice energy depends upon the charge and size. On increasing the charge of the metal lattice energy increases. On increasing the size of the negative ion the lattice energy decreases.
Lattice energy $ \propto $ Charge of the metal
Lattice energy $ \propto $ $\dfrac {1}{ Size\;of\;the\;anion}$

The charge on the lithium metal is the same in both ${\text{L}}{{\text{i}}_{\text{2}}}{\text{O}}$ oxide and ${\text{L}}{{\text{i}}_{\text{2}}}{\text{C}}{{\text{O}}_{\text{3}}}$. The size of carbonate ${\text{CO}}_3^{2 - }$ is more than the size of oxide ${{\text{O}}^{2 - }}$ so, the lattice energy of the lithium oxide will be high than the lattice energy of lithium carbonate. So, the thermodynamics stability of lithium oxide will be more than the thermodynamics stability of lithium carbonate.

So, ${\text{L}}{{\text{i}}_{\text{2}}}{\text{O}}$ is more stable than ${\text{L}}{{\text{i}}_{\text{2}}}{\text{C}}{{\text{O}}_{\text{3}}}$.

Therefore, the statement is true.

Note: Thermodynamic stability is directly proportional to the ionic character. Thermodynamic stability is inversely proportional to the covalent character. The covalent character in ionic compounds is determined by using Fajan’s rule. According to Fajan’s rule, the covalent character in ionic compounds are directly proportional to the polarizing power of the cation and inversely proportional to the polarizability of the anion. The polarizing power of the cation is high if the size is small and the charge is maximum. The polarizability of the anion will be high if the size is large and the charge is maximum.