A catalyst lowers the activation energy of a reaction from 85.0 kJ/mol to 60.0 kJ/mol…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A catalyst lowers the activation energy of a reaction from to . The pre-exponential factor stays the same. Find the power of ten by which the rate constant is multiplied at . A step takes minutes without the catalyst. How long does it take with it?
Need a reminder? The key ideaShow
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.
The worked solution
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. The drop in barrier. .
Step 2. The power of ten. .
Step 3. The factor. , about twelve thousand times faster.
Step 4. The time. , and .
Check. A drop of is about a quarter of the original barrier, and the speed-up is of the order of ten thousand. This is how big a catalyst effect can be.
Answer: the rate constant is multiplied by , and the step takes .
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