One mole of A and two moles of B are placed in a container. At equilibrium, the density of the gas mixture is 0.312 g/L at 0.2 atm and 500 K. What is…

One mole of A and two moles of B are placed in a container. At equilibrium, the density of the gas mixture is 0.312 g/L at 0.2 atm and 500 K. What is the value of Kc in units of (mol/L)?