Question

Catalytic converters made of palladium (Pd) reduce automobile pollution by catalyzing the reaction between unburned hydrocarbons and oxygen. How does Pd increase the rate of this reaction?
A: By cooling the reactants
B: By splitting the oxygen atoms
C: By giving the hydrocarbons a negative charge
D: By decreasing the activation energy

Answer 1

Answer: D: By decreasing the activation energy

Explanation: A catalyst is a substance which increases the rate of a reaction by taking the reaction through a different path which involves lower activation energy and thus more molecules can cross the energy barrier and convert to products.

Activation energy is the extra energy that must be supplied to reactants in order to cross the energy barrier and thus convert to products.

The catalyst itself does not take part in the chemical reaction and is regenerated as such at the end.

Answer 2

Almost all catalysts work by lowering the activation energy of the reaction with no change in the free energy of the reaction 

- So in this case we can say that palladium  reduce automobile pollution by catalyzing the reaction between un-burned hydrocarbons and oxygen :

D. by decreasing the activation energy