Answer
$$K_c = 3.5 \times 10^{-7} $$
Work Step by Step
1. Calculate $\Delta n$ (n is the amount of moles of gases):
$$\Delta n = n_{products} - n_{reactants} = 3 - 2 = 1 $$
2. Convert the temperature to Kelvin:
$$T/K = 350 + 273.15 = 623.15 $$
3. Calculate Kc:
$$K_c = \frac{K_p}{(RT)^{\Delta n}} = \frac{( 1.8 \times 10^{-5} )}{(0.0821 \times 623.15 )^{ 1 }}$$
$$K_c = 3.5 \times 10^{-7} $$
