Ceric Ammonium Nitrate Preparation and Standardization

🧪 Preparation of 0.1 M Ceric Ammonium Nitrate

The solution is prepared as follows:

1. Dissolve about 54.82 grams of Ceric Ammonium Nitrate (AR Grade) in the first step.
2. Heat 56 ml of concentrated H2​SO4​ (sulfuric acid) in 500 ml of water.
3. Combine the dissolved Ceric Ammonium Nitrate with the heated sulfuric acid mixture.
4. Cool the solution and filter if it appears turbid.
5. Dilute the clear solution with distilled water to a final volume of 1000 ml.
6. Allow the preparation to stand one day before proceeding to standardization.

🔬 Standardization of 0.1 M Ceric Ammonium Nitrate

The Ceric Ammonium Nitrate solution is standardized against Arsenic Trioxide (As2​O3​), a primary standard.

Standardization Procedure

1. Weigh accurately about 0.2 gm of Arsenic Trioxide (As2​O3​), which has been previously dried at 105∘C for 1 hour.
2. Transfer the weighed As2​O3​ to a conical flask.
3. Wash down the inner walls of the flask with 25 ml of a 8.0% w/v solution of Sodium Hydroxide (NaOH).
4. Swirl the flask to dissolve the arsenic trioxide completely.
5. Add 100 ml of water and mix.
6. Add 30 ml of dilute H2​SO4​ (sulfuric acid).
7. Add 0.15 ml of Osmic Acid solution and 0.1 ml of Ferroin Sulfate solution (indicator).
8. Titrate with the prepared Ceric Ammonium Nitrate solution until the pink color changes to a very pale blue (the endpoint).

Calculation

The molarity of the Ceric Ammonium Nitrate solution can be calculated using the titration data and the weight of the primary standard, As2​O3​.

The fundamental relationship is:

Volume of Ce(IV)×Molarity of Ce(IV)×Factor=Weight of As2​O3​

Or, specifically:

Molarity (M)=Volume of Ce(IV) used in ml×0.004946Weight of As2​O3​ in grams​

Where 0.004946 grams is the weight of As2​O3​ equivalent to 1 ml of 0.1 M Ceric Ammonium Nitrate.

The reaction that occurs during the titration is a redox reaction where Ce(IV) oxidizes As(III) to As(V). The osmic acid acts as a catalyst, and the ferroin sulfate complex acts as the visual indicator for the endpoint.