What do you mean by activity and selectivity of catalysts ?

Explanation

Important features of solid catalyst:
(a) Activity: The activity of a catalyst is its ability to accelerate chemical reaction. It depends upon the strength of chemisoprtion to a large extent. The catalytic activity of a metal for hydrogen increases as we move from Group 5 metals to Group 11. The maximum activity is show by metals of Group 7,8 and 9
(b) Selectivity. The selectivity of a catalyst it its ability to direct to yield a particular product. it mean a substance which acts as a catalyst in one reaction may not act as a catalyst in other reaction e., we get different products when we use different catalysts in the reaction between `H_(2)` and `CO`.