Question

Can KMnO4 react as oxidizing agent in absence of acid?​

Answer 1

consider KMnO4 to be a strong oxidizing agent under any conditions. But let's look at the following reactions:

Acidic solution: MnO4- + 8 H+ + 5 e- ---> Mn(2+) + 4 H2O.

Neutral solution: MnO4- + 4 H+ + 3 e- ---> MnO2 + 2H2O.

Basic solution: MnO4- + e- ---> MnO4(2-).

You will notice that:

(1) You get more electrons per MnO4- ion in acidic solution > neutral solution > basic solution.

(2) The acidic-solution reaction consumes more H+ ions, implying that a lower pH favors the reaction (Le Chatelier's Principle). The same can be said for the neutral-solution reaction.

For these reasons, KMnO4 is a stronger oxidizing agent in acidic v. neutral v. basic solution