Consider the following hypothetical balanced reaction, which occurs at 400°C when 5.20 mol of AB2 is placed in a 1.25 L flask, and equilibrium is established at 400°C. It was found that 2.40 mol of AB2 had dissociated. Calculate the equilibrium constant, Keq, for the reaction at 400°C.
a) 1.45
b) 2.17
c) 3.42
d) 4.38