The volume of  0.1M permanganate solution required to oxidise 300 ml of 0.1 M thiosulphate solution in faintly alkaline medium to form sulphate ion is

Mole ratio = 8:3;8Mn+7O4-+3S+22O3-2+H2O→8Mn+4O2+6S+6O4-2+2OH-;M1V1n1=M2V2n2 0.1×V18=300×0.13 =800 ml; Alternate method; Decrease in ox.no/mole of  KMnO4=3; Increase in ox.no/mole of Na2S2O3=8;          V1N1=V2N2; V10.1M3=3000.18;               V1=800 ml;