How would an energy diagram for a reaction that used a catalyst differ from an energy diagram without a catalyst?
the reactants will be at a higher potential energy.
the products will be at a higher potential energy.
the barrier for activation energy will be lower.
the barrier for activation energy will be higher.

               The barrier for activation energy will be lower.

Explanation:

                      As we know the minimum amount of energy required by the reactants to convert into products is called as Activation energy. Until this energy is attained the reactants fail to transform into products. Also, the lower the activation energy is, the greater will be the rate of reaction. Hence, a catalyst is employed in order decrease the activation energy.

Catalyst through different mechanism lowers the activation energy. Some of which are listed as,

                         1) By weaknening the bonds of reactants

                         2) By providing different pathway

                         3) By providing surface area

                         4) By holding close together the reactants

Below is a energy diagram of same reaction carried out in the presence of catalyst (Red) and absence of catalyst (Blue).