Find out the %age purity of FeSO4. The given solution contains 1g/50ml. You are provided with 0.0166 K2Cr2O7 solution.

 

Theory

Chemicals

K₂Cr₂O₇ soln.(50ml), FeSO₄ soln (50ml), Diphenylamine

Apparatus

Burette, pipette, funnel, conical flask, burette stand, beaker, weight balance

Principle:

Redox titration

Indicator

Diphenylamine

End point

Violet Blue Colour

Chemical Equation

K₂Cr₂O₇  + 7H₂SO₄  +   6 FeSO₄     ---------->    K₂SO₄ + 3Fe₂(SO₄)₃ + Cr₂(SO₄)₃ + 7H₂O   

Mole ratio

K₂Cr₂O₇      :      FeSO₄

1        :           6

Procedure

Prepare 50ml solution of FeSO₄ by taking 1g of FeSO₄ and dissolving it to 50 ml of distilled water

Prepare 50ml solution of K₂Cr₂O₇ by taking 2g of K₂Cr₂O₇ and dilute up to 50ml with distilled water

Prepare indicator by adding 0.5g of diphenylamine in 90% H₂SO₄

Prepare the sample solution by taking 10ml of FeSO₄ solution in titration flask and add 2ml H₃PO₄ and 2 drops of indicator.

Take K₂Cr₂O₇ in burette and titrate against 10ml FeSO₄ solution in the flask till we get violet blue colouration

Result

The %age purity of FeSO₄ is ……….