The energy profile for a reaction is shown below. Which of the following is a fully correct statement about this energy level profile?

Answer:

22) D

Let us start by identifying what the letters are.

The reaction is endothermic (energy is absorbed during the reaction) since products have more energy than reactants.

• U represents the energy of the reactants
• Z represents the energy of the products
• V + W = activation energy
• V represents the difference in energy between products and reactants
• W is the part of the activation energy.
• Y represents the activation energy needed if a catalyst was used.
• X shows the route taken without a catalyst.

A:
Reaction is endothermic – Correct
V is the heat of reaction – Correct
X is the activation energy – Wrong
So, A is wrong.

B:
Products (Z) have more energy than the reactants (U) – Correct
X shows the route taken when a catalyst is present – Wrong
W is the activation energy – Wrong
So B is wrong. 

C: 
Y is the route taken when a catalyst is present – Correct
V is the heat of reaction – Correct
The reaction is exothermic overall – Wrong
Hence C is wrong

D:
X shows the route taken without a catalyst: Correct
V + W is the activation energy: Correct
V (the heat of reaction) has a positive sign: Correct
So, D is correct.