A sealed 5.0L container initially holds diatomic hydrogen gas at 1000K and 2.0atm. At this temperature, 40% of the H2 molecules dissociate into atomic hydrogen according to H2→2H. The temperature remains constant. What is the final pressure in the container?
a) 1.2atm
b) 3.6atm
c) 2.8atm
d) 2.0atm