Estimation of Ferrous Ammonium Sulphate (FAS)

Estimation of Ferrous Ammonium Sulphate (FAS)

Aim :

To estimate the amount of ferrous ammonium sulphate (FAS) dissolved in 1500 ml of the given unknown solution volumetrically. For this you are given with a standard solution of ferrous sulphate ( FeSO₄ )of normality 0.1024 N and potassium permanganate solution as link solution.

Principle:

Oxidation : 5 Fe²⁺  → 5 Fe³⁺ + 5e⁻

Reduction: 5Fe²⁺ + MnO₄⁻ + 8H⁺  → 5Fe³⁺ + Mn²⁺ + 4H₂O

Overall reaction: 5Fe²⁺ + MnO₄⁻ + 8H⁺     → 5Fe³⁺ + Mn²⁺ + 4H₂O

Short procedure:

Procedure :

Titration–I

(Link KMnO₄)Vs (Standard FeSO₄ )

Burette is washed with water, rinsed with KMnO₄ solution and filled with same solution up to the zero mark. Exactly 20 ml of standard FeSO₄ solution is pipetted out into the clean, washed conical flask. To this 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 are noted, the same procedure is repeated to get concordant values.

Titration –I

(Link KMnO₄)Vs (Standard FeSO₄ )

Calculation :

Volume of KMnO₄ (link) solution  V₁ =     ml

Normality KMnO₄ (link) solution     N₁      =       ?N

Volume of standard FeSO₄ solution V₂      =       20 ml

Normality of standard FeSO₄ solution       N₂      =       0.1024 N

According to normality equation:

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

N₁ = V₂ × N₂ / V₁

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

Titration–II

(Unknown FAS) 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 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. 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 KMnO₄)Vs (Unknown FAS)

Calculation :

Volume of Unknown FAS solution V₁  = 20ml

Normality of Unknown FAS solution N₁ = N

Volume of KMnO₄ (link) solution V₂ = ml

Normality KMnO₄ (link) solution

According to normality equation: V₁× N₁ = V₂ ×

N₂ N₁ = V₂  × N₂ / V₁

N₁= ------------------------ N

The normality of unknown FAS solution   = --------Y---N

Weight calculation:

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

The amount of FAS dissolved in 1500 ml of the solution = Normality × equivalentweight × 1500 / 1000

= Y × 392  × 1500 / 1000

= g

Report :

The amount of FAS dissolved in 1500 ml of the solution = g