Question

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.

Answer 1

The equilibrium position will shift to left (reactant side). Because more SO3 molecules will collide and become O2 and SO2. The Qc value is larger than the Kc value, thus it shifts to left until Qc=Kc.

Answer 2

Answer is: 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.

According to Le Chatelier's Principle the position of equilibrium moves to counteract the change.

According to Le Chatelier's principle: if the concentration is changed, that will shift the equilibrium to the side that would reduce that change in concentration.

The equilibrium shift to the left, so more reactants will be produced.