Question

Suppose that the reaction a→products is exothermic and has an activation barrier of 75 kj/mol. What can be said about the energy change during the reaction?

1) The energy change during the reaction is positive
2) The energy change during the reaction is negative
3) The energy change during the reaction is zero
4) The energy change during the reaction cannot be determined

Answer 1

The energy change during the reaction is negative.

Step-by-step explanation:

The activation energy for a reaction is the energy barrier that must be overcome for the reaction to occur. In this case, the activation energy is 75 kJ/mol. Since the reaction is exothermic, it releases energy. Therefore, the energy change during the reaction is negative.

Answer 2

The energy change during the reaction is negative. Therefore the correct answer is option 2.

Step-by-step explanation:

In an exothermic reaction, energy is released as products form from reactants. The activation barrier of 75 kJ/mol indicates the energy required to initiate the reaction. Since the reaction is exothermic, the energy of the products is lower than that of the reactants. Therefore, as the reaction progresses, more energy is released than required to overcome the activation barrier, resulting in a negative energy change. This signifies that the overall energy of the products is lower than the initial energy of the reactants.

In this scenario, considering the exothermic nature of the reaction and the activation energy required, the energy change can be deduced as negative. The activation barrier, representing the energy hurdle to start the reaction, does not affect the direction of the energy change during the reaction itself. Instead, it represents the initial energy input needed for the reaction to proceed. Hence, despite the activation energy, the net outcome is an energy release, confirming a negative energy change during the reaction.

The exothermic nature of the reaction ensures that the energy released during the formation of products exceeds the initial energy input required (the activation energy). This characteristic defines the energy change during the reaction as negative, indicating a release of energy into the surroundings as the reaction progresses. Therefore the correct answer is option 2.