Assertion (A): $\text{Vapour density = }\frac{\text{Density of gas}}{\text{Denstiy of hydrogen gas}}$

 Reason (R): Vapour density of oxygen molecule at STP is 8.

Vapours density is the relative quantity and it has no units.

  $\text{Vapour\hspace{0.17em}density ,V.D =}\frac{\text{Density\hspace{0.17em}of gas}}{\text{Density\hspace{0.17em}of hydrogen gas}}$

At STP, Vapour density of oxygen gas is,

   $\text{V.D\hspace{0.17em}of Oxygen =}\frac{\left(\frac{32\text{\hspace{0.17em}g\hspace{0.17em}}}{22.4\text{\hspace{0.17em}L}}\right)}{\left(\frac{2\text{\hspace{0.17em}g}}{22.4\text{\hspace{0.17em}L}}\right)}$

 Then, vapour density of oxygen gas, V.D  = 16