[randall]

-Slowly add sodium hydrogen sulphite solution to potassium permanganate solution until a brown precipitate of MnO2 has formed...
  -suppose sodium hydrogen sulphate was used instead of sodium hydrogen sulphite. Why is no reaction observed?

[Karakth]

You will need to post more than just a question: What have you attempted so far, and where are you getting stuck? Do you have any suspicions of the answer?

Also, on a somewhat unrelated note: New nomenclature rules say that for clearness' sake, we should write sulfate and sulfite with an f. Not my preference, but most chemists are Americans and Americans write it with an f.

[oldddog]

Determine the oxidation state of manganese in the reactant and then in the product. Is it oxidised or reduced. It is one or the other - then it must be that the sulfite takes on the other part of the Redox reaction. Now look at the sulfate and see if you can work out why it wont participate in the reaction.