You have to leave solids and liquids out of the equation. This leaves only product B for the product, nothing for the reactants. Initially there was no product B. At equilibrium: you determine the molarity by multiplying 2.5% by (0.5M/10L)= .00125 = which rounds to answer E) 1.3e-3 it was a trick question. Solution You have to leave solids and liquids out of the equation. This leaves only product B for the product, nothing for the reactants. Initially there was no product B. At equilibrium: you determine the molarity by multiplying 2.5% by (0.5M/10L)= .00125 = which rounds to answer E) 1.3e-3 it was a trick question..