The portal has been deactivated. Please contact your portal admin.

Question Video: Determining How Catalysts Affect the Energy Changes during a Chemical Reaction Chemistry • 10th Grade

Some substances are able to reduce the activation energy. How would this affect the energy changes during a chemical reaction?

03:13

Video Transcript

Some substances are able to reduce the activation energy. How would this affect the energy changes during a chemical reaction? (A) More energy would be required for the reaction to proceed. (B) Less energy would be required for the reaction to proceed. (C) There would be an increase in the total enthalpy change of the reaction. (D) There would be a decrease in the total enthalpy change of the reaction. (E) The reaction would release energy to the surroundings, instead of absorbing energy.

This question is asking us about activation energy. We can best understand activation energy by looking at a reaction profile, which shows the energy level of the molecules in the reaction from beginning to end. In the reaction profile, the activation energy is the difference between the energy level of the reactants and the energy level of the high-energy transition state in the middle of the reaction. The activation energy is the minimum amount of energy required for a reaction to occur. If less energy than this is added, the reaction will not proceed.

As the question indicates, some substances are able to reduce the activation energy. We call these substances catalysts. In the presence of a catalyst, the activation energy is reduced. In other words, the energy barrier that the reaction needs to reach in order to proceed is lowered. Looking at our answer choices, this description matches answer choice (B): less energy would be required for the reaction to proceed. The catalyst changes the energetics of the reaction and allows it to happen using less energy.

To be thorough, let’s eliminate the other answer choices as well. Answer choice (A) is incorrect, as it is the opposite of the observed effect of the catalyst. Answer choices (C) and (D) are incorrect as well. The total enthalpy change, or Δ𝐻, is the difference in energy between the reactants and the products. Since the catalyst only changes the energy of the transition state, it does not affect the total enthalpy change from the beginning to the end of the reaction.

Lastly, choice (E) is incorrect as well. As we just noted, the catalyst does not change the energy levels of the reactants or products, so it would not affect whether the reaction gains or loses energy. Catalysts can be simple molecules or complex biological structures. Vanadium oxide is a simple molecule that is used as a catalyst in a variety of industrial processes, while amylase is an example of a biological catalyst, or enzyme, that our bodies use to more efficiently carry out necessary chemical reactions.

So, how would this affect the energy changes during a chemical reaction? (B) Less energy would be required for the reaction to proceed.

Nagwa uses cookies to ensure you get the best experience on our website. Learn more about our Privacy Policy.