Answer
$$K_c = 81.9$$
Work Step by Step
$$K_p = K_c (RT)^{\Delta n}$$
$\Delta n = n(products) - n(reactants) = (2) - (1 + 1) = 0$
$R = 0.08206 $
$T = 298$
$K_p = 81.9$
$$K_c = \frac{K_p}{(RT)^{\Delta n}} = \frac{81.9}{(0.08206 \times 298)^0 } = 81.9$$
