Answer
$$K_c = 2.56 \times 10^{-23}$$
Work Step by Step
$$K_p = K_c (RT)^{\Delta n}$$
$\Delta n = n(products) - n(reactants) = 2 - 1 = 1$
$R = 0.08206 $
$T = 298$
$K_p = 6.26 \times 10^{-22}$
$$K_c = \frac{K_p}{(RT)^{\Delta n}} = \frac{6.26 \times 10^{-22}}{(0.08206 \times 298)^1 } = 2.56 \times 10^{-23}$$
