(a)
$K_{p} = K_{c}(RT)^{\mathrm{\Delta}n_{g}}$
Here, $\mathrm{\Delta}n_{g} = 2 - 4 = - 2$
$\therefore K_{p} = 6 \times 10^{- 2} \times (0.0821 \times 773)^{- 2}$
or, $K_{p} = \frac{6 \times 10^{- 2}}{(0.0821 \times 773)^{2}} = 1.5 \times 10^{- 5}$