Ammonium carbonate when heated to 200°C gives a mixture of ${\mathrm{NH}}_{3( \mathrm{g})},{\mathrm{CO}}_{2( \mathrm{g})}$ ,  and ${\mathrm{H}}_2\mathrm{O}$-vapour with a density of 13.0. The degree of dissociation of ammonium carbonate is

${\left({\mathrm{NH}}_4\right)}_2{\mathrm{CO}}_{3( \mathrm{g})}\rightleftharpoons {}^{200°\mathrm{C}}⟶2{\mathrm{NH}}_{3( \mathrm{g})}+{\mathrm{CO}}_{2( \mathrm{g})}+{\mathrm{H}}_2{\mathrm{O}}_{\left(\mathrm{g}\right)}$

Vapour density of Ammonium carboante  $\text{ (D) }=\frac{\text{ Mol. mass of }{\left(N{H}_4\right)}_{2}C{O}_3}{2}$

$\begin{array}{l}=\frac{96}{2}\\ =48\end{array}$

Vapour density of the mixture (d) =13

n(no. of moles of gaseous products from 1 mole of reactant) =4

Degree of dissociation,

$$\begin{gathered} x=\frac{D-d}{d(y-1)} \\ =\frac{48-13}{13(4-1)} \\ =\frac{35}{13\times 3} \\ =0.89 \end{gathered}$$