Question

The diagram shows the potential energy changes for a reaction pathway.

Answer 1

Answer:

The change in enthalpy is given by the difference between the enthalpy of the reactants and the enthalpy of the products and it is denoted by the symbol ΔH

For the given reaction, we have;

ΔH = C - A

The activation energy, is the minimum energy that must be supplied in the reaction for the reaction to take place and for the products to be formed

In the diagram, the activation energy, Eₐ, is given by the the difference between the threshold energy, $E_{TH}$, B and the heat content of the reactants, A

∴ Eₐ = B - A

Given that the enthalpy of the products, C is larger than the enthalpy of the reactants, A, the total change in enthalpy, ΔH is positive. Similarly, the activation energy, Eₐ, is positive, given that the threshold energy, B, is larger than the heat content of the reactants

Part 2

An exothermic reaction is a reaction that involves the release of energy by the reactants in order to form the products. Exothermic reactions have a negative total change in enthalpy, therefore, for an exothermic reaction, we get;

The total potential energy in the reactants, A > The total potential energy in the products, B

Therefore, on the curve for an exothermic reaction, A, will be higher than B and ΔH will be negative (ΔH = A - B = Negative where A > B)

Explanation: