On addition to a small amount of KMnO₄ to concentrated H₂SO₄, a green oily compound is obtained which is highly explosive in nature. Identify the compound from the following.

1. Mn₂O₇

2. MnO₂

3. MnSO₄

4. Mn₂O₃

When $KMn{O}_4$ solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because

1.  $C{O}_2$ is formed as the product

2.  Reaction is exothermic

3.  $Mn{O}_4^{-}$ catalyses the reaction

4.  $M{n}^{2+}$ acts as autocatalyst

$KMn{O}_4$ acts as an oxidizing agent in an acidic medium. The number of moles of $KMn{O}_4$ that will be needed to react with one mole of sulphide ions in an acidic solution is$\mathrm{:}$

KMnO₄ acts as an oxidising agent in alkaline medium. When alkaline KMnO₄ is treated with KI, iodide ion is oxidised to .........

Why is HCl not used to make the medium acidic in oxidation reactions of $KMn{O}_4$ in acidic medium?