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Effect of Catalyst on Rate of Reaction (Class 12)

 

Investigatory Project on Effect of Catalyst on Rate of Reaction (Class 12)

Principle: A catalyst is a substance which alters the rate of a reaction without it is being consumed in the reaction. A catalyst may speed up a reaction and then it will be called a positive catalyst. It may slow down a reaction and then it will be called a negative catalyst. Their functions can be illustrated by studying the decomposition of hydrogen peroxide in the presence of various substances.


2H2O2 --> 2H2O + O2


Aim: The aim of the investigatory project is to study the influence of catalysts on the rate of reaction.


Materials Required: Hydrogen peroxide, MnO2, HCl, NaOH, Al powder, Test tubes


Procedure:


Pour 10mL portions of 20 volume hydrogen peroxide into four test-tubes. To each of the test tube add the following substances and note the rates at which bubbles evolve in each case.


1. 5 drops of 2M NaOH

2. 5 drops of 2M HCl

3. About 10 mg of MnO2

4. About 10 mg of Aluminium powder


Except in the case of adding HCl, in all other cases effervescence is seen. The briskness of the effervescence may be taken as a measure of the effectiveness of the catalyst in decomposing hydrogen peroxide. It becomes evident that while HCl acts as a negative catalyst, the other three act as positive catalysts.


Conclusion:


It is concluded from the experiment that the rate of reaction increases with a positive catalyst and decreases with a negative catalyst.


Viva Questions with Answers


1. What is a catalyst?


Ans: A substance which alters the rate of a reaction without itself undergoing any permanent chemical change is called a catalyst.


2. What is a positive catalyst?


Ans: A catalyst which increases the rate of a reaction is called a positive catalyst.


3. Give the example of a positive catalyst?


Ans: MnO2 in the dissociation of hydrogen peroxide to produce O2 and water.


4. What is a negative catalyst?


Ans: A catalyst which decreases the rate of a reaction is called a negative catalyst.


5. Give the example of a negative catalyst.


Ans: Hydrochloric acid in the dissociation of hydrogen peroxide.

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