$[K_{sp}\, BaSO_4 = 10^{-11}, K_{sp}\, CaSO_4 = 10^{-6}, K_{sp}\,Ag_2SO_4 = 10^{-5}]$
${H_2}{O_2}\, + \,{H_2}O\, \rightleftharpoons \,{H_3}{O^ + }\, + \,HO_2^ - $