Question

Use the graph to answer the questions.

Energy > - - - - - - - - - - - - - - - - - - - - to - - - - - - - - - - - - - - - - -- - Time

Which part of the graph represents activation energy?

A

C

E

B

D

Which one choose the best definition for activation energy?

1. energy produced by an object in motion

2. energy that must be added to start a reaction

3. energy released during a chemical reaction

4. energy difference between reactants and products in a reaction

5. energy that is stored in chemical bonds

Answer 1

The D in the graph represents activation energy.

Activation energy can be defined as the energy that must be added to start a reaction.

Explanation:

The above graph is a typical example of an exothermic reaction. The reactants from their initial state A, need an external energy D to reach the transition state. The transition state is the peak of the curve and the external energy required to reach the transition state is called activation energy. The reaction flows from the transition state to the final state B, which is lower than the initial energy state A, thus releasing an extra energy E. When the energy state of the final product is lower than the initial state and when excess energy is released during a reaction, then the reaction is called exothermic reaction.