Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
A reaction has a forward activation energy of and . A catalyst lowers the forward barrier to . Find the reverse barrier without and with the catalyst, and with the catalyst. Does the equilibrium constant change?
A catalyst lowers the barrier by in both directions. If stays the same, . and the equilibrium constant do not change. In a mechanism, a catalyst is used in one step and made again in a later one.
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Without the catalyst. .
Step 2. With the catalyst. . The reverse barrier fell by , the same as the forward barrier.
Step 3. The enthalpy change. The reactants and the products are the same, so is still .
Step 4. The equilibrium. The forward and the reverse reactions are speeded up by the same factor. So the equilibrium constant does not change.
Answer: and , and . The equilibrium constant is unchanged.
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