Transition metal and their compounds are used as catalysts in industry and in biological system. For example, in the Contact Process, vanadium compounds in the + 5 state `(V_2O_5 or VO_3^(-))` are used to oxidise `SO_(2) " to "SO_3 : SO_(2) + 1/2O_2 overset(v_2o_5) rarr SO_(3)`
It is thought that the actual oxidation process takes place in two stages. In the first step, `V^(5+)` in the presence of oxide ions converts `SO_(2)"to " SO_3` ' At the same time, `V^(5+)` is reduced to `V^(4+)`
`2V^(5+) + O^(2-) + SO_(2) rarr 2V^(4+) + SO_(3)`
In the second step `V^(5+_` is regenerated from `V^(4+)` by oxygen : `2V^(4+) + 1/2 O_(2) rarr 2V^(5+) +O^(2-)`
The overall process is, of course, the sum of these two step : `SO_(2) + 1/2 O_(2) rarr SO_(3)`
Catalytic activity of transition metals depends on

Options

A. their ability to exist in different oxidation states
B. the size of the metal atoms
C. the number of empty atomic orbitals available
D. none of these

Answer

A

Explanation

d-block elements show catalytic property due to variable oxidation states