Video Transcript
In the following two diagrams,
which two letters indicate reaction pathways that have been catalyzed?
The question provides us with two
energy level diagrams. An energy level diagram shows how
the total potential energy changes as reactants turn into products during a chemical
reaction. The flat line on the left side of
the graph represents the potential energy of the reactants. The flat line on the right side of
the graph represents the potential energy of the products. We can see that over the course of
each reaction, the reactants need to gain a minimum amount of energy in order to
turn into the products. The minimum amount of energy
required by reactant particles to collide and react with one another is called the
activation energy.
Each graph shows two reaction
pathways that each have a different activation energy. We want to know which of these
pathways indicates a reaction that has been catalyzed. A catalyst is a substance that
increases the rate of a chemical reaction without undergoing a permanent chemical
change. Catalysts increase the rate of a
chemical reaction by reducing the amount of activation energy needed for a
successful collision between reactant molecules.
Looking at the graph on the left,
we can see that reaction pathways A and B have the same reactants and products. But reaction pathway B has a lower
activation energy. As reaction pathway B produces the
same products as reaction pathway A but requires less activation energy, this
pathway must have been catalyzed. Looking at the graph on the right,
we can see that reaction pathways C and D have the same reactants and products, but
reaction pathway D has a lower activation energy. This indicates that reaction
pathway D must have been catalyzed. Therefore, the two letters that
indicate reaction pathways that have been catalyzed are B and D.
