Which of the following is affected by a catalyst?

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What is affected by a catalyst?
What is the effect of catalysis?
Which of following is affected by addition of catalyst?
Does Delta H is affected by catalyst?

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To increase the rate of a reaction you need to increase the number of successful collisions. One possible way of doing this is to provide an alternative way for the reaction to happen which has a lower activation energy.

In other words, to move the activation energy on the graph like this:

As before, particles which don't have enough energy at a particular time will at some time in the future gain energy from random collisions, just as other particles will lose energy. You mustn't get the idea that those particles in the blue area of the graph can never react - given time they will.

Adding a catalyst has exactly this effect of shifting the activation energy. A catalyst provides an alternative route for the reaction. That alternative route has a lower activation energy. Showing this on an energy profile:

A word of caution!

Be very careful if you are asked about this in an exam. The correct form of words is

"A catalyst provides an alternative route for the reaction with a lower activation energy."

It does not "lower the activation energy of the reaction". There is a subtle difference between the two statements that is easily illustrated with a simple analogy.

Suppose you have a mountain between two valleys so that the only way for people to get from one valley to the other is over the mountain. Only the most active people will manage to get from one valley to the other.

Now suppose a tunnel is cut through the mountain. Many more people will now manage to get from one valley to the other by this easier route. You could say that the tunnel route has a lower activation energy than going over the mountain.

But you haven't lowered the mountain! The tunnel has provided an alternative route but hasn't lowered the original one. The original mountain is still there, and some people will still choose to climb it.

In the chemistry case, if particles collide with enough energy they can still react in exactly the same way as if the catalyst wasn't there. It is simply that the majority of particles will react via the easier catalysed route.

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What is affected by a catalyst?

A catalyst is a substance that speeds up a chemical reaction, or lowers the temperature or pressure needed to start one, without itself being consumed during the reaction. Catalysis is the process of adding a catalyst to facilitate a reaction.

What is the effect of catalysis?

The rate of a reaction can be increased by adding a suitable catalyst. A catalyst is a substance which increases the rate of a chemical reaction but it is not used up (remains chemically unchanged at the end). It provides an alternative reaction pathway of lower activation energy.