Question

Look at the potential energy diagram for a chemical reaction.

Which statement correctly describes the energy changes that occur in the forward reaction?

The activation energy is 10 kJ and the reaction is exothermic.

The activation energy is 10 kJ and the reaction is endothermic.

The activation energy is 50 kJ and the reaction is exothermic.

The activation energy is 50 kJ and the reaction is endothermic.

Answer 1

Answer: The activation energy is 10 kJ and the reaction is exothermic.

Explanation: Exothermic reactions are those in which heat is released and thus the energy of products is less than the energy of reactants.

Endothermic reactions are those in which heat is absorbed and thus the energy of products is more than the energy of reactants.

Activation energy is the extra amount of energy required by the reactants to cross the energy barrier to convert to products.

Given : Energy of reactants = 40kJ

Energy of activation: (50-40)=10 kJ

Energy of products = 50 kJ

Energy of products = 15 kJ

Thus Energy of products (15kJ) < Energy of reactants(40kJ), the reaction is exothermic as energy has been lost to surroundings in the form of heat.

Answer 2

Answer:

The activation energy is 10 kJ and the reaction is exothermic.

Explanation:

The difference between the start of the graph and the beginning of the reaction is 10 kJ. The reaction loses energy, so it is exothermic.