1. Weighing of the Ferrous Ammonium Sulphate:
- Weigh 39.212 grams of ferrous ammonium sulphate hexahydrate (Fe(NH4)2(SO4)2 6H2O) using an analytical balance.
2. Dissolving and Transferring:
- Dissolve the weighed ferrous ammonium sulphate in a small amount (about 50 mL) of deionized water in a beaker. Stir until it dissolves completely.
- Transfer the dissolved solution quantitatively to a 1000 mL volumetric flask.
3. Adding Deionized Water:
- Add more deionized water to the volumetric flask until the solution reaches the 1000 mL mark.
- Swirl gently to ensure thorough mixing.
Note: It's crucial to use deionized water throughout the preparation process to minimize any potential interference or reactions from impurities present in regular tap water.
Standardization/Checking the Normality:
To verify the exact normality of your prepared 0.1N ferrous ammonium sulphate solution, you can perform a standardization process. This involves titrating the solution against a standard potassium permanganate (KMnO4) solution of known concentration (for example, 0.1N). The steps involved are:
- Using a burette, add a known volume (e.g., 20 mL) of the prepared 0.1N ferrous ammonium sulphate solution to a conical flask.
- Add a few drops of concentrated sulphuric acid to the flask to provide an acidic environment.
- Start adding the 0.1N potassium permanganate solution slowly from the burette, constantly swirling the flask and observing the color change.
- Continue adding the permanganate solution until the solution changes from colorless to a pale pink color that persists for at least 30 seconds.
- Note the volume of potassium permanganate used.
- Calculate the exact normality of your 0.1N ferrous ammonium sulphate solution using the formula:
Normality (N) of Ferrous Ammonium Sulphate = (N of KMnO4 × Vol. of KMnO4) / Vol. of Ferrous Ammonium Sulphate
By adjusting the concentration if necessary (by adding more deionized water or ferrous ammonium sulphate), you can ensure the accuracy of your 0.1N ferrous ammonium sulphate solution.
Remember to use appropriate safety precautions while handling chemicals and wear proper lab attire.
