Ammonium carbonate when heated to 2000C gives a mixture of NH3 and CO2 vapour with a density of 13.0. What is the degree of dissociation of ammonium carbonate?

NH2COONH4 ⇌  2NH3 + CO2α = D-dn -1d  where d is the density (initial)D=vapour density=mol.wt2 = 782 = 39n =Total no. of moles of products= 3, d = final densityα = 39-133 -113=1,  so  α=1