A BRIEF LOOK AT CATALYSTS

We all have heard of catalysts. In lay terms we know that catalysts speed up reactions. But the question is how do they accomplish this Consider the formal definition of a catalyst. 

A catalyst is a chemical substance that can increase the rate of a reaction. Even if the catalyst is involved in the reaction, by the end of the reaction you will get the catalyst intact. In other words, the catalyst retains its identity. If a substance changes its identity and does not have the original nature after the reaction has occurred, it is not a catalyst, but a reactant. 

Catalysts are often classified on the basis of the phases (solid, liquid, and gas) in which they exist during a chemical reaction. If a catalyst exists in the same phase as the reactants of a reaction, then it is called a homogeneous catalyst. If a catalyst s phase is different from that of the reactants of a reaction, then it is called a heterogeneous catalyst. 

Many reactions are reversible. Reversible reactions are reactions in which there are both forward and backward reactions. Consider an experiment in which two reactants have been mixed. At first, the reaction proceeds with considerable rate in the forward direction (forward reaction favored). Before the reaction goes on to completion, the backward reaction takes place. Then again the forward reaction takes place, followed by the backward reaction and so on. These uneven back-and-forth directional changes take place until the reaction mixture reaches the equilibrium. At the equilibrium, the rate will be the same for both forward and backward reactions. 

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