Concentrated hydrogen peroxide solutions are explosively decomposed by traces of transition metal ions (such as Mn or Fe): 2H₂O₂(aq) ---> 2H₂O(l) + O₂(g)

What volume of pure O₂(g), collected at 27C and 746 torr, would be generated by decomposition of 125 g of a 50.0% by mass hydrogen peroxide solution?