A quantity of liquid methanol, CH3OH, is introduced into a rigid 3 L vessel, the vessel is sealed, and the temperature is raised to 500K. At this temperature, the methanol vaporizes and decomposes according to the reaction
CH3OH(g) <=> CO(g) + 2 H2(g) Kc= 6.90 x 10-2.
If the concentration of CO in the equilibrium mixture is 0.2 M, what mass of methanol was initially introduced into the vessel?