123. Solving a chemistry problem

1 mol of NO2 gas was placed in a reaction vessel and heated until the equilibrium NO2(g) ↔ NO(g) 1/2O2(g) was established at a total pressure of 1 atm. At temperatures of 700 and 800 K, the equilibrium ratios of partial pressures pNO/pNO2 were found to be 0.872 and 2.50, respectively. Calculate the equilibrium constant Kp and the Gibbs energy ΔG0 at these temperatures. Calculate also the enthalpy of the reaction.