Procedure
Preparation of Solutions:
- Preparation of Standard Potassium Dichromate Solution:
Dissolve an accurately weighed amount of Potassium Dichromate
(K2Cr2O7) in distilled water and
dilute to 1000 mL in a volumetric flask to make a 0.1 N solution.
- 2. Preparation of Ferrous Ammonium Sulfate (FAS) Solution:
Weigh accurately about 3.92 g of FAS, dissolve in a minimum amount of distilled water, add 10 mL of
dilute H2SO4, and dilute to 100 mL in a volumetric flask.
Process
- Connect the potentiometer to the indicator electrode (platinum electrode) and the reference
electrode (calomel or silver/silver chloride electrode).
- Place the electrodes in the beaker containing the FAS solution.
- Transfer 25 centiliters of ferrous ammonium sulphate using a pipette into a beaker. Pour in two
test tubes filled with diluted sulfuric acid.
- Put the platinum electrode assembly and calomel inside of it.
- Measure the potential by connecting the platinum and calomel electrode to a potentiometer.
- Add 0.5 N potassium dichromate solution to the burette.
- To the beaker, add 0.5 cm3 of potassium dichromate.
- Mix the mixture and record the potential.
Proceed with the process until the potential
exhibits a tendency to rise quickly.
- Add potassium dichromate now, measuring the potential after each addition in 0.5 cm3 increments.
- Plot the equivalency point of ∆E/∆V against the volume of potassium dichromate to create a graph.
- Calculate the normality and weight of ferrous ammonium sulphate in the given solution.
