Important Features of Solid Catalysts
- Activity of a catalyst refers to the capacity of the catalyst to increase the speed of the chemical reaction. The activity depends upon the extent of chemisorption.
- The adsorption should be reasonably strong but not so strong that the adsorbed molecules become immobile and there is no place for other reactants to get adsorbed. Example- Combination of H2 and O2 in the presence of Platinum(catalyst) to form water is an explosive reaction.
- But in the absence of catalyst, H2 and O2 do not react and can be stored like that for a very long period of time.
2H2(g) + O2(g) --> 2H2O(l)
- Selectivity of a catalyst refers to its ability to direct the reaction to form particular products excluding others.
- Example- CO and H2 form different products in the presence of different catalysts
Note- Catalysts are very specific and selective in their action. So a substance which acts as a catalyst in one reaction may fail to catalyse another reaction