Which changes occur when o2(g) is added to this system? given the system at equilibrium: 2pocl3(g) + energy < --> 2pcl3(g) + o2(g).

a.) the equilibrium shifts to the right and the concentration of pcl3(g) increases.
b.) the equilibrium shifts to the right and the concentration of pcl3(g) decreases.
c.) the equilibrium shifts to the left and the concentration of pcl3(g) increases.
d.) the equilibrium shifts to the left and the concentration of pcl3(g) decreases.