Video Transcript
Which of the following is shown by
the red arrow in the sketch graph? (A) The heat loss, (B) the
exothermic change, (C) the endothermic change, (D) the activation energy, or (E) the
enthalpy change.
The figure shown is a generic
energy level diagram that shows the energy of reactants and products during a
chemical reaction process. The flat line on the left side
describes the energy of the reactants, while the flat line on the right is the
energy of the products. The curved line between reactants
and products describes the energy evolution as reactants become products.
You’ll notice that the 𝑥-axis has
the title “Reaction Progression” and the 𝑦-axis has the title “Energy.” The reaction progression proceeds
from reactants to products, from left to right. In any reaction, there will be an
energy barrier between the starting materials and products, represented by an area
where the energy is higher than the starting material.
In some systems, the energy barrier
will be very high, making it nearly impossible for the reaction to proceed under the
given conditions. When a catalyst is added, this
energy barrier becomes significantly smaller, allowing the reaction to proceed via a
different path. And this energy barrier that must
be overcome in order for a reaction to proceed is called the activation energy. Or, more formally, the activation
energy is the minimal amount of energy required for a reaction to occur.
With this information, we can
revisit and answer the question. Which of the following is shown by
the red arrow in the sketch graph? And the correct answer is (D), the
activation energy.
