Question

Why is hydrated barium peroxide used in the preparation of hydrogen peroxide instead of anhydrous barium peroxide? Explain.

Answer 1

It cannot be used since the precipitated BaSO4 forms a protective layer around the interacted barium peroxide there by preventing the further reaction

Answer 2

Initially the following reaction takes place when anhydrous barium peroxide is treated with $H_2SO_4$ but further reaction stops.

This implies that the reaction is feasible but there is something that prevents the further reaction.

In this reaction $BaSO_4$ precipitate is formed. This insoluble product covers the unreacted $BaO_2$ forming a protective layer which stops further reaction.

$BaO_2 .8H_2O(s)+ H_2SO_4 (aq)\rightarrow BaSO_4 (s) + H_2O_2 (aq)+ 8H_2O(l)$

Hydrated barium peroxide ($BaO_2 .8H_2O$) paste is prepared in ice cold water making sure that the paste is thin and slowly poured into a 20% solution of ice cold $H_2SO_4$ to make the reaction proceed without hindrance.