Question

A dark violet colour mixture in presence of dil. $HCl$ changes to pale yellow solution. Mixture may contain:
(A). $MnO_4^ - ,F{e^{2 + }}$
(B). $MnO_4^ - ,{C_2}O_4^{2 - }$
(C). ${I^ - },C{r_2}O_7^{2 - }$
(D). none is correct

Answer 1

Hint: In chemistry, oxidizing agent is that reactant that removes electrons from other reactants during a redox reaction. The oxidizing agent typically takes electrons from itself and thus (these) gaining electrons and then being reduced. Moreover, it is thus an electrons acceptor. Talking about reducing agents, an element that loses or donates an electron to an oxidizing agent in a redox chemical reaction. A reducing agent is thus oxidized when it loses electrons in the redox reaction.

Complete step by step answer:
As redox reactions are carried out in aqueous solution. When the concentration of ${H^ + }$ is more in the solution that means it is acidic in nature. So we call it an acidic medium. When the concentration of $O{H^ - }$ is more in the solution that means they are basic in nature. So we call it basic medium.
In an acidic medium, $MnO_4^ - $ acts as a strong oxidizing agent and itself is reduced to $Mn\left( {11} \right)$ ions. Moreover, in an acidic medium, $F{e^{2 + }}$ acts as a reducing agent and itself is oxidized to $F{e^{3 + }}$ . Hence, the colour changes from dark violet to light yellow when dilute $HCl$ is added to a mixture of $MnO_4^ - $ and $F{e^{2 + }}$.

So, the correct answer is Option A .

Additional Information:
$MnO_4^ - $ Is a strong oxidizing agent because elements become more electronegative as the oxidation state of their atoms increase. Moreover, the permanganate in potassium permanganate has the anion $MnO_4^ - $. That is the reason for its strong oxidizing properties. The permanganate ion removes electrons from oxalic acid molecules and thereby it oxidizes the oxalic acid. Thus the $MnO_4^ - $ ion acts as an oxidizing agent in this reaction.

Note:
Potassium Permanganate is a salt of permanganic acid. It is neither an acid nor a base. It is natural. It is a salt as the ${K^ + }$ ions are from $KOH$ which is a strong base and $Mn{O_4}$ ions from $HMn{O_4}$ which is an acid. Thus it is neither salt nor base but neutralized product like salt.