Answer
$$K_c = 1.3\times 10^{22}$$
Work Step by Step
$$K_p = K_c (RT)^{\Delta n}$$
$\Delta n = n(products) - n(reactants) = (1 + 3) - (1 + 1) = 2$
$R = 0.08206 $
$T = 298$
$K_p = 7.7 \times 10^{24}$
$$K_c = \frac{K_p}{(RT)^{\Delta n}} = \frac{7.7 \times 10^{24}}{(0.08206 \times 298)^2 } = 1.3\times 10^{22}$$
