Estimation of Ferrous Sulphate

VOLUMETRIC ANALYSIS

Estimation of Ferrous Sulphate (Fe²⁺)

Aim :

To estimate the amount of ferrous sulphate dissolved in 750 ml of the given unknown solution volumetrically. For this you are given with a standard solution of ferrous ammonium sulphate (FAS) of normality 0.1102 N and potassium permanganate solution as link solution.

Principle:

During these titrations, Fe²⁺ ions (from ferrous salts) are oxidised to MnO₄^- ions and MnO₄^- ion (from Mn²⁺) is reduced to Mn²⁺ ion.

Oxidation   :        5 Fe²⁺          → 5 Fe³⁺ + 5e⁻

Reduction   : 

Overall reaction:

5Fe²⁺ + MnO₄^- + 8H → 5Fe³⁺ + Mn²⁺ + 4H₂O

Short procedure :

Procedure :

Titration–I

(Link KMnO₄)Vs (Standard FAS)

Burette is washed with water, rinsed with KMnO₄ solution and filled with same KMnO₄ solution up to the zero mark. Exactly 20 ml of standard FAS solution is pipetted out into the clean, washed conical flask. To this FAS solution, approximately 20ml of 2N sulphuric acid is added. This mixture is titrated against KMnO₄ Link solution from the burette. KMnO ₄ is added drop wise till the appearance of permanent pale pink colour. Burette reading is noted, and the same procedure is repeated to get concordant values.

Titration –I

(Link KMnO₄ )Vs (Standard FAS)

Calculation :

Volume of KMnO₄ (link) solution (V₁) = ----------ml

Normality KMnO₄ (link) solution (N₁) =-----------N

Volume of standard FAS solution (V₂) = 20 ml

Normality of standard FAS solution (N₂) = 0.1102 N

According to normality equation: V₁× N₁ = V₂ × N₂

N₁ = V₂ × N₂ /  V₁

Normality of KMnO4 (link) solution (N₁) = ----------------- X N

Titration–II

(Unknown FeSO₄ ) Vs (Link KMnO₄)

Burette is washed with water, rinsed with KMnO₄ solution and filled with same KMnO₄ solution up to the zero mark. Exactly 20 ml of unknown FeSO₄ solution is pipetted out into the clean, washed conical flask. To this FeSO₄ solution approximately 20ml of 2N sulphuric acid is added. This mixture is titrated against KMnO₄ Link solution from the burette. KMnO₄ is added drop wise till the appearance of permanent pale pink colour. Burette reading is noted and the same procedure is repeated to get concordant values.

Titration –II

(Link FeSO₄ )Vs (Unknown FeSO₄ solution)

Calculation :

Volume of Unknown FeSO₄  solution V₁ = 20 ml

Normality of Unknown FeSO₄ solution N₁ = ? N

Volume of KMnO₄ (link) solution V₂ = ml

Normality KMnO₄  (link) solution N₂ = X N

According to normality equation: V₁× N₁ = V₂ × N₂

 N₁ = V₂ × N₂  / V₁

N₁= --------Y--------- N

The normality of unknown FeSO₄  solution = ________________ N

Weight calculation:

The amount of FeSO₄ dissolved in 1 lit of the solution = (Normality) x (equivalent weight)

The amount of FeSO₄ dissolved in 750 ml of the solution  = Normality x equivalentweight x 750 / 1000

Report :

The amount of FeSO₄ dissolved in 750 ml of the solution  =  ---g