A gaseous mixture contains 68% by mass of NH₃ and remaining is H₂. Identify the correct statement from the following?

Number of moles of NH₃ = $\frac{68}{17}$=4

Number of moles of H₂ = $\frac{32}{2}$= 16

Average molar mass = $\frac{\mathrm{Total} \mathrm{mass} \mathrm{of} \mathrm{the} \mathrm{mixture}}{\mathrm{Total} \mathrm{moles} \mathrm{of} \mathrm{the} \mathrm{mixture}}$

= $\frac{100}{4+16}$=5

Vapour density = $\frac{\mathrm{Molar} \mathrm{mass} }{2}=\frac{5}{2}$=2.5