KMnO4, with ferrous sulphate, FeSO4. MnO^-4(aq) + Fe^(2+)(aq) ⟶ Mn^(2+)(aq) + Fe^(3+)(aq)

Question

Using the oxidation number method write the net ionic equation for the reaction of potassium permanganate, KMnO₄, with ferrous sulphate, FeSO₄.

MnO^-_4(aq) + Fe²⁺_(aq) ⟶ Mn²⁺_(aq) + Fe³⁺_(aq)

Answer 1

Step 1 : 

Write skeletal equation and balance the elements other than O and H.

MnO^-_4(aq) + Fe²⁺_(aq) ⟶ Mn²⁺_(aq) + Fe³⁺_(aq)

Step 2 : 

Assign oxidation number to Mn and Fe, and calculate the increase and decrease in the oxidation number and make them equal.

To make the net increase and dicrease equal, we must take 5 atoms of Fe²⁺

MnO^-_4(aq) + 5Fe²⁺_(aq) ⟶ Mn²⁺_(aq) + 5Fe³⁺_(aq)

Step 3 : 

Balance the ‘O’ atoms by adding 4H₂O to the right-hand side.

MnO^-_4(aq) + 5Fe²⁺_(aq) ⟶ Mn²⁺_(aq) + 5Fe³⁺_(aq) + 4H₂O_(l)

Step 4 : 

The medium is acidic. 

To make the charges and hydrogen atoms on the two sides equal, add 8H⁺ on the left-hand side.

MnO^-_4(aq) + 5Fe²⁺_(aq)+ 8H⁺_(aq) ⟶ Mn²⁺_(aq) + 5Fe³⁺_(aq) + 4H₂O_(l)

Step 5 : 

Check the two sides for balance of charges and atoms. The net ionic equation obtained in step 4 is the balanced equation. 

Hence, balanced equation :

MnO^-_4(aq) + 5Fe²⁺_(aq)+ 8H⁺_(aq) ⟶ Mn²⁺_(aq) + 5Fe³⁺_(aq) + 4H₂O_(l)