Question

Consider the reaction pathway graph for a two-step reaction below.

Which inference does the graph best support?
Step A is endothermic, so it is faster than Step B.
Step A has a greater activation energy, so it is faster than Step B.
Step A is endothermic, so it is slower than Step B.
Step A has a greater activation energy, so it is slower than Step B.

Answer 1

Answer is: Step A has a greater activation energy, so it is slower than Step B.

Reactions occur faster (not lower) with a catalyst because they require less activation energy.

For all chemical reaction some energy is required and that energy is called activation energy (energy that needs to be absorbed for a chemical reaction to start).

There are two types of reaction: endothermic reaction (chemical reaction that absorbs more energy than it releases) and exothermic reaction (chemical reaction that releases more energy than it absorbs).

Answer 2

Answer : Option D) Step A has a greater activation energy, so it is slower than Step B.

Explanation : Here we can clearly see that when the reactants undergo step A and then forms an intermediate which goes to step B and then finally yielding products. This both the steps undergo an endothermic reaction as the energy of reactants is lower than that of products. Also we can compare the energy of activation of step A with step B and see that energy of activation of step A is higher than step B. So, step A is much slower than step B.