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

Which of the following is oxidised by $SO_2$?

$A$ mixture of potassium chlorate,oxalic acid,and sulphuric acid is heated. During the reaction,which element undergoes the maximum change in its oxidation number?

Which of the following combinations of reagents does not undergo a redox reaction in an aqueous medium?

Which of the following processes does not involve oxidation of iron?

$K_2Cr_2O_7$ paper acidified with dilute $H_2SO_4$ turns green when exposed to