The equilibrium concentration of PCl5 will increase PCl3 is added.
What is equilibrium?
A reversible reaction is said to be in equilibrium when the rates of the forward and the backward reaction are equal.
According to a law of reaction, when a reaction is in equilibrium and one of the constraints that affect the rate of reaction is applied, the equilibrium will shift so as to annul the effects of the constraint introduced.
Thus, in this case, in order for more PCl5 (a reactant) to be formed, PCl3 (a product) would have to be added.
More on equilibrium can be found here: https://brainly.com/question/11114490
