Rate of diffusion $\propto (1 / M)$
$M =$ molecular mass
$M \left( CO _{2}\right)=44 \,\,\,\,\,\,\,\,\, M \left( N _{2}\right)=28$
$M \left( NH _{3}\right)=17 \,\,\,\,\,\,\,\,\,\, M \left( O _{2}\right)=32$
Therefore, rate of $NH _{3}$ diffusion is greater than other.