In a vessel with a volume of 12.7 dm3 and at a certain temperature, 0.298 moles of HCONH2, 5.71 moles of NH3 and 3.43 moles of CO are present at equilibrium. The volume of the vessel is then brought to 9.20 dm3. Determine the pressure inside the reactor once equilibrium is reached. The reaction is: HCONH2 -> NH3 + CO

I tried to initially calculate the equilibrium constant, then I halved the moles for the decreasing volume ... I have problems with the equilibrium in the gas phase, I often get confused!