Answer
$$K_p= 2.0$$
Work Step by Step
Since this reaction produces 2 moles of DH:
$\Delta H^o_{rxn} = 2 \times 0.32 \space kJ = 0.64 \space kJ = 640 \space J$
Van't Hoff's equation:
$$ln \space \frac{K_1}{K_2} = -\frac{\Delta H^o_{rxn}}{R}\Bigg(\frac {1}{T_2} - \frac{1}{T_1} \Bigg)$$
$$ln \space \frac{1.80}{K_2} = -\frac{640}{8.314}\Bigg(\frac {1}{298} - \frac{1}{500.} \Bigg)$$
$$ln \space \frac{1.80}{K_2} = -0.10436$$
$$\frac{1.80}{K_2} = e^{-0.10436} = 0.9009$$
$$K_2 = \frac{1.80}{0.9009} = 2.0$$
