Question

A dark violet colour mixture in presence of dil.$HCl$ changes to pale yellow solution. Mixture may contain :

• A. ${MnO}_4^{-},{Fe}^{2+}$
• B. ${MnO}_4^{-},C_2{O}_4^{2-}$
• C. $I^{-},{Cr}_2{O}_7^{2-}$
• D. none is correct

Answer 1

Answer: (A)

${MnO}_4^{-},{Fe}^{2+}$

In acidic medium ${MnO}_4^{-}$ acts as strong oxidizing agent and itself is reduced to Mn(II) ions. In the 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 dil HCl is added to a mixture of ${MnO}_4^{-}$ and $F{e}^{2+}$.