Question

In which medium oxidizing power of \[KMn{{O}_{4}}\] is maximum?
a.) Acidic
b.) Basic
c.) Neutral
d.) a or b depending upon concentration.

Answer 1

Hint: Oxidizing power is the tendency of an atom to gain electrons. \[KMn{{O}_{4}}\] is termed as a strong oxidizing agent known by the name potassium permanganate.

Complete step by step answer:
Potassium permanganate is an inorganic compound having the chemical formula \[KMn{{O}_{4}}\]. It is composed of \[{{K}^{+}}\]and\[Mn{{O}_{4}}^{-}\]. It is a purple-black crystalline solid that dissolves in water to give pink or purple solutions.
Oxidizing power is the tendency of an element to accept electrons. The greater is its ability, greater will be its oxidizing power. Oxidizing power depends upon the effective nuclear charge it decreases down the group and increases across the period.

\[KMn{{O}_{4}}\] is a strong oxidizing agent under any conditions but we get more electrons per \[Mn{{O}_{4}}^{-}\] ion in acidic medium as compared to basic or neutral which can be shown as:
\[Mn{{O}_{4}}^{-}+8{{H}^{+}}+5{{e}^{-}}\to M{{n}^{2+}}+4{{H}_{2}}O\] (In acidic media)
\[Mn{{O}_{4}}^{-}+{{e}^{-}}\to Mn{{O}_{4}}^{2-}\] (In basic media)
\[Mn{{O}_{4}}^{-}+4{{H}^{+}}+3{{e}^{-}}\to Mn{{O}_{2}}+2{{H}_{2}}O\] (In neutral solution)

The acidic solution absorbs more \[{{H}^{+}}\] ions which implies that a lower pH favors the reaction. For these two reasons we can say that \[KMn{{O}_{4}}\] has maximum oxidizing power in an acidic medium.
So, the correct answer is “Option A”.

Note: The atoms which have greater tendency to accept electrons have greater stability. Oxidizing power is based on the effective nuclear charge which can be defined as the charge felt by the outermost (valence) electrons of an atom after taking into account the number of shielding electrons that surround the nucleus.