What Do You Mean By Catalyst

As we know that all the reactions are completed in a thermodynamical way but what happened, when some foreign materials are present during these reactions. Is the reaction proceeding in a similar way as before or there may be some changes in the reaction's rate due to the presence of these foreign materials.  

In the late 1800s, it was observed that a small amounts of foreign substance could greatly affect the course of chemical reaction. This observation was indeed a profound observation which led to the hypothesis that small amounts of foreign substance could greatly affect the course of a chemical reaction. 
Subsequently, it was Oswald who actually made a clearer definition of;
What A Catalyst Is???


CATALYSTS
There are some substances that affect the rate of a reaction. They either speed up the reaction or slow it down. These rate changing substances are called Catalysts. They are neither products nor reactants. 
........"A catalyst is any substance (or material) that, when it is added to a reaction, increases or slows the rate of the reaction due to its presence in the reaction. These substances are not consumed during the reaction".......
This reaction in which a catalyst is present is called a "Catalytic Reaction". This phenomenon is called "Catalysis".

Therefore, we can say that a catalytic reaction is defined as a reaction whose rate is altered by materials that are neither reactants not products and these foreign materials are called Catalysts. They need not be present in large amounts. Even small amounts of these substances are enough to change the rate of a chemical reaction.
......"A Catalyst Is A Substance That Makes A Chemical Reaction Happen Faster"........

Catalyst can, in fact, increase the rate of any chemical reaction by changing the reaction mechanism or by reducing the activation energy. Thus, we can say that the rate of a reaction increases or decreases on adding a catalyst in it. This is done by lowering the reaction mechanism or by lowering the nature of the transition state (means lowering activation energy).

Types Of Catalyst 
Catalysts can be of two types: Homogeneous and Non-homogeneous Catalysts.
Homogeneous Catalyst
A catalyst that is in the same phase as the reactant and the product. And the process is called Homogeneous catalysis.
Non-homogeneous Catalyst
A catalyst in which the phase of the catalyst is different from that of the reactants or products. And the process is called Non-homogeneous catalysis.

Example Of Catalytic Reactions
(a) 2H₂O₂(K-MnO₄ as catalyst)➝ 2H₂O + O₂
Here, 
    A catalyst of potassium permanganate is used to increase the reaction rate.
(b) The Iron catalyst used in the Haber-Bosch process, which is the main industrial process for ammonia production.
(c) Zeolites are used as catalyst in Cracking of petroleum.
(d) Even the human body runs on many catalysts. Many proteins in our body are actually catalysts called Enzymes, which do everything from creating signals that move our limbs to helping digest our food. They are truly a fundamental part of life.
(e) A man has been obese all his life, unable to lose weight. Then a friend dies of weight related issues. The shock of it serves as a catalyst to make him completely change his lifestyle.


Point To Be Remembered
  • The first process which actually is known or at least has been recorded as a catalytic process, is the "production of Di-ethyl ether ( in presence of sulfuric acid as catalyst) in 1552"
  • First heterogeneous catalytic process which is encountered in nature, is the conversion of "Sulfur dioxide into sulfur trioxide using platinum as catalyst in 1875".
  • Nearly 90% of all industrial reactions involves 'Heterogeneous catalysis'.
  • In absence of catalyst, there will be no attenuation in the activation energy barrier and therefore the reaction will proceed in a thermodynamical way. 
  • Catalyst affects the reaction rate by changing the molecular path that the reaction actually takes in order to reach to the product, that is, product streams or product form. 
  • The action of the catalyst can be understood by "Transition state theory". According to this theory, the catalyst forms a temporary bond with the reactants by participating in a chemical reaction resulting in an intermediate package. Its existence is transient and it decomposes to give products and catalysts.
FAQs
What is a catalyst???
Catalysts are substances that change the rate of a chemical reaction without being consumed during the reaction.
How many types of catalysts are there??
There are mainly two types of catalysts: Positive catalyst & Negative catalyst. 
Such catalysts which increase the speed of the process are called positive catalysts. 
Such catalysts which slow down the rate of reaction are called negative catalysts.



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