In contact process inpurities of arsenic is removed by

In contact process impurities of arsenic is removed by

In contact process impurities of arsenic are removed by

In Contact process impurities of arsenic are removed by:

Explain the following giving suitable reasons: In the manufacture of H_2SO_4 by contact process: The impurity of arsenic oxide must be removed before passing the mixture of SO_2 and air through the catalytic chamber.