Potasium Dichromate Titration 424x4g

Experiment Estimation of Ferrous iron using External Indicator Aim

: Estimate the amount of ferrous iron in the whole of the given ferrous solution using external indicator

Principle : The estimation in based on the oxidation of Ferrous iron to ferric iron by potassium dichromate in acid medium K₂Cr₂O₇ + 4H₂SO₄ 4H₂O + [O]

→ K₂SO₄ → Cr₂ (SO₄)₃ +

2FeSO₄ + H₂SO₄ + [O]

→ Fe (SO₄)₃ + H₂O

The External Indicator Potassium Ferricyanide will give blue colour with Fe²⁺ only. So at the

end point the solution does not give a bluish colourisation with potassium Ferricyanide. Procedure a)Preparation dichromate

of

Standard

Potassium

Weighed about 0.65g of K₂Cr₂O₇ is accurately transferred into a 250ml standard flask. It is dissolved in water and made upto the mark. b)Estimation of Ferrous iron The given solution is made up to 100ml. 20ml of the made up to 100 ml 20 ml of the made up solution in pipetted out in to a clean beaker about 20 ml Dilute sulphuric acid in added it in then diluted to 150 ml and titrated Again standerd potassium dichromate solution taken in the buretted Drops of the solution from the beaker are mix periodically with indicator drops placed on a porcelain plate or tile the procedure in continued till a

Drop from the beaker does not give blue colour then the range in noted

The beaker is then washed and another 20ml quantity of solution taken In to the black with vigorous shaking up to the minimum of the range already noted. Subsequently 2 drops at a time are added and the solution in the beaker is checked for the completion of the reaction. The procedure in continued till a drop from the beaker does not give tile or green colour with the indicator drop titration are repeated till concordant values are attained .from the titer value the amount of ferrous iron in the what of the solution can be calculated knowing that the equivalent wt off ferrous iron in 55-85 Result Weight of Fe²⁺ in the whale of the given solution=---------g

Observation and calculations Weighing of K₂Cr₂O₇

Item to Weight Weig be added ht weighed g mg Positio MSD SSD due to n R/L rider Weighing bottle + K₂Cr₂O₇ Weighing bottle after transferri ng K₂Cr₂O₇

Total weig ht (g)