Determination of Chloride Content of Water by Argentometry

Title of Experiment: Determination of Chloride Content of Water by Argentometry

Aim

To estimate the chloride concentration in the given water sample

Apparatus Required

Burette, Burette stand, pipette, Conical flask, Beakers, Standard flask, and funnel etc.

Chemicals Required

Silver Nitrate(AgNO₃), Potassium chromate(K₂CrO₄), Distilled Water, Raw Water

Principle

The sample of water containing chlorides is titrated with silver nitrate solution.Chlorides are precipitated as white silver chlorides the potassium chromate used as indicator ,which supplies chromate ions. As the concentration of chloride ions opposes extinction the silver ion concentration increases to a level at which reddish brow precipitate of silver chromate is formed indicating the end point

Formula

Amount of chloride content present in water sample = (V₂-V₁) * 35.5 * 1000 / Volume of Sample

Where N = Normality of AgNO₃ = 0.01 N

Procedure

1. Wash all the apparatus with water thoroughly.

2. Fill the burette with silver nitrate and fix it to the burette stand.

3. Pipette out the 20ml of distilled water from beaker into a conical flask.

4. Add about 1ml of potassium chromate indicator to a solution in conical flask.

5. Titrate the solution with silvernitrate until the solution becomes reddish brown.

6. Tabulate all the readings and calculate the volume of AgNO3 consumed by using the formula.

7. Amout of chloride content is obtained in mg/lit (or) ppm.

Precautions

1. The glass apparatus used in the experiment should be washed with distilled water.
2. All the reagents should be freshly prepared.
3. The end point of the titration should be observed carefully.
4. The volume of the indicator should be small in all titrations.

Observation Table

Calculations

Amount of chloride content present in water sample = (V₂-V₁) X 35.5 X 1000/ Volume of sample

Result

The amount of total chloride content present in water sample is .............

Viva Questions and Answers

1. Define argentometry?
2. What is the indicator used in argentometry?
3. What are the units for Chloride content?
4. Define Standard solution?
5. Give the examples for Primary and Secondary standard solutions?