Which catalyst is used in polymerization of ethylene?

The catalyst used in the polymerisation of olefin is

The catalyst used for the polymerisation of olefine

In contact process some amount of H_2SO_4 is used to dissolve SO_3 explain which catalyst is used for the preparation of SO_3 ?

Which catalyst is used to convert alkyne into alkene in one step ?

Catalyst used in dimerisation of acetylene to prepare chloroprene is :

Which catalyst is used in contact process of manufacturing of H_2SO_4 ?

Ethylene is used for

The catalyst used in the above conversion is

A catalyst is a substance which