Examine the reversible reaction. 2so2 + o2 ⇌ 2so3 if the reaction is at chemical equilibrium, what will be the effect of adding more molecules of so3? the rate of the forward reaction will increase, which will cause reactants to form faster and the balance of the system to shift to the left. the rate of the reverse reaction will increase, which will cause reactants to form faster and the balance of the system to shift to the left. the rate of the forward reaction will increase, which will cause products to form faster and the balance of the system to shift to the right. the rate of the reverse reaction will increase, which will cause products to form faster and the balance of the system to shift to the right.