How many moles of $H_2SO_3$ are required to reduce one mole of $KMnO_4$ in an acidic medium?

Why do the following reactions proceed differently? $Pb_{3}O_{4} + 8HCl \rightarrow 3PbCl_{2} + Cl_{2} + 4H_{2}O$ and $Pb_{3}O_{4} + 4HNO_{3} \rightarrow 2Pb(NO_{3})_{2} + PbO_{2} + 2H_{2}O$

Which of the following is not a redox reaction?

The autocatalyst in the redox reaction involving acidified potassium permanganate and oxalic acid is

In order to oxidize a mixture of one mole of each of $FeC_2O_4$,$Fe_2(C_2O_4)_3$,$FeSO_4$ and $Fe_2(SO_4)_3$ in acidic medium,the number of moles of $KMnO_4$ required is

Oxalic acid when treated with potassium permanganate in the presence of an acid,produces