Understanding the Redox Reaction between Iron(II) and Permanganate Ions in Acidic Solution

In the realm of redox chemistry, understanding the balance of half-reactions is crucial. This article will guide you through the process of balancing the redox reaction between iron(II) ions (Fe2 ) and permanganate ions (MnO4-) in an acidic environment. We will also explore the stoichiometry involved in the reaction and calculate how many moles of Fe2 can be oxidized by a given amount of permanganate ions.

Step-by-Step Balancing of Redox Half-Reactions

Let's begin by establishing the individual half-reactions for the oxidation and reduction processes.

Oxidation Half-Reaction

The oxidation of iron(II) to iron(III) can be written as:

Fe2 → Fe3 e-

Reduction Half-Reaction

The reduction of permanganate in acidic solution to manganese(II) can be represented as:

MnO4- 8H 5e- → Mn2 4H2O

Stoichiometric Adjustment for Electron Balance

To combine these half-reactions, we need to ensure the number of electrons transferred is equal. The oxidation reaction produces 1 electron, while the reduction reaction consumes 5 electrons.

Therefore, we multiply the oxidation half-reaction by 5 to balance the electrons:

5Fe2 → 5Fe3 5e-

Combining Half-Reactions

Now, we add the balanced half-reactions together:

5Fe2 MnO4- 8H 5e- → 5Fe3 Mn2 4H2O 5e-

Cancelling the electrons gives us the final balanced equation:

5Fe2 MnO4- 8H → 5Fe3 Mn2 4H2O

Conclusion: Calculating the Moles of Reactants and Products

The balanced equation for the reaction between Fe2 and MnO4- in acidic solution is:

5Fe2 MnO4- 8H → 5Fe3 Mn2 4H2O

To find how many moles of Fe2 can be oxidized by 0.067 moles of MnO4-, we use the stoichiometry of the reaction:

Moles of Fe2 5 × Moles of MnO4-

Moles of Fe2 5 × 0.067 0.335 moles

Therefore, 0.067 moles of MnO4- can oxidize 0.335 moles of Fe2 to Fe3 .

Additional Considerations

When dealing with redox reactions in practical applications, it is important to consider the presence of reasonable counterions. For instance, in aqueous solutions of FeCl2, K2MnO4, and HCl, the reaction would proceed as:

5FeCl2(aq) K2MnO4(aq) 8HCl(aq) → 5FeCl3(aq) 2MnCl2(aq) 8H2O KCl(aq)

This equation represents the complete reaction in a typical experimental setup.