Dear Sir/ Madam,In question 113 of 1994, the reason for the decolourization of acidic KMnO4 is taken as SO2’s acidity. Isn’t this incorrect? Shouldn’t the reason be the reducing power of SO2, because for instance, CO2 is acidic, but that doesn’t mean that it can decolourize KMnO4 right?Please help. Thank you.

in this question the acidity of so2 and so2 does not matter .What matter is the reducing prropoerties of both the gases.As co2 is a oxidating agent and it is totally oxidised(here the oxidation number of carbon is 4 which is the highest ox no of C )it will reduce the kmno4 solution.so it does not decolourises the soln.But as so2 is not totally oxidised(its highest oxidation no is 6 and here its oxidation no is 4)it will react with kmno4 and will reduce it.