$K_P/K_C$  for the reaction at $T\left(K\right)$  is 

$CO\left(g\right)+\frac{1}{2}{O}_2\left(g\right)\underset{ }{\rightleftharpoons }C{O}_2\left(g\right)$

 $K_p=K_c{\left(RT\right)}^{\Delta n}$
[$\Delta n=$ Change in the no.  gaseous molecules from reactant to product.]
In this equation, 
 
$\Delta n=(1-1-\frac{1}{2})=-\frac{1}{2}\therefore \frac{K_p}{K_c}={\left(RT\right)}^{-\frac{1}{2}}=\frac{1}{\sqrt{RT}}$