Gokul43201 said:
A redox reaction is a type of chemical reaction where there is a transfer of electrons between reactants, resulting in the oxidation of one substance and the reduction of another substance.
KMnO4, or potassium permanganate, is a strong oxidizing agent. It is used in this reaction to oxidize the iron(II) ions in ammonium iron(II) sulfate to iron(III) ions.
Adding excess acidified KMnO4 ensures that there is enough oxidizing agent to fully oxidize all of the iron(II) ions present in the ammonium iron(II) sulfate. The excess KMnO4 also helps to maintain an acidic environment, which is necessary for the reaction to occur.
At the beginning of the reaction, the ammonium iron(II) sulfate solution is colorless. As the iron(II) ions are oxidized to iron(III) ions, the solution turns a pale yellow color. When all of the iron(II) ions have been oxidized, the solution will turn a dark brown color due to the presence of excess KMnO4.
Ammonium iron(II) sulfate, also known as Mohr's salt, is used as the reducing agent in this reaction. It provides the iron(II) ions that are necessary for the KMnO4 to oxidize. It also helps to maintain the acidic environment needed for the reaction to occur.