Phosphoric acid is preferred over sulphuric acid in preparing hydrogen peroxide from peroxides. Why?
H2SO4 can act as a catalyst and can activate the decomposition of H2O2.
Thus, weaker acids such as H3PO4 are preferred over H2SO4, in preparation of H2O2 from peroxides.
For example – In preparation of H2O2 from barium peroxide (BaO2), instead of H2SO4, we use phosphoric acid such that all heavy metal impurities are removed as insoluble phosphates and decomposition of H2O2 can be prevented.