Question

Which of the following statement regarding catalysts is not true
A. A catalyst remains unchanged in composition and quantity at the end of the reaction
B. A catalyst does not alter the equilibrium in a reversible reaction
C. A catalyst can initiate a reaction
D. Catalysts are sometimes very specific in respect of reaction

Answer 1

Hint: A catalyst is a chemical substance that speeds up the speed of a reaction and does not furnish a change in its quantity or chemical arrangement after the completion of the reaction. This process is called catalysis.

Complete Step by Step Answer:
The rate of a reaction normally rises when a catalyst is added.

We have to find out which of the given options is not true in the case of catalysts.
A. A catalyst remains intact in arrangement and amount at the end of the reaction.
There is no difference in the structure and amount of catalyst before and after the reaction.
So, A is true so it is incorrect.

B. A catalyst does not change the equilibrium in a reversible reaction
Catalysts do not impact or adjust the position of equilibrium in a reaction.
Putting in a catalyst brings no difference to the equilibrium as a catalyst speeds up the forward and back reaction to the same magnitude. The addition of a catalyst does not influence the rates of the two reactions.
So, B is true so it is incorrect.

C. A catalyst can start a reaction
The catalyst only increases the rate of the reaction. This reaction may be already happening unhurriedly.
The catalyst cannot start it.
So, C is not true so it is correct.

D. Catalysts are occasionally very distinctive regarding reaction.
A given catalyst can catalyse only a specific reaction.
For example, manganese dioxide can catalyse the decomposition of potassium chlorate but fails for other reactions.
So, D is true so it is incorrect.
So, option C is correct.

Note: We should see that catalysts normally do not initiate a reaction as it does not get involved in a reaction directly. It only speeds up the rate of reaction, stays intact chemically, and is specific in its action.