1. Find the Molecular Weight:
The molecular weight of KH₂PO₄ is approximately:
* K (Potassium): 39.10 g/mol
* H (Hydrogen): 1.01 g/mol x 2 = 2.02 g/mol
* P (Phosphorus): 30.97 g/mol
* O (Oxygen): 16.00 g/mol x 4 = 64.00 g/mol
Total Molecular Weight ≈ 39.10 + 2.02 + 30.97 + 64.00 = 136.09 g/mol
2. Calculate the mass needed for 1N solution:
A 1 Normal solution contains 1 equivalent weight of solute per liter of solution. Since the equivalent weight of KH₂PO₄ is equal to its molecular weight in this case, you need 136.09 grams of KH₂PO₄ per liter of solution.
3. Preparation:
1. Weigh out: Accurately weigh 136.09 grams of KH₂PO₄ using an analytical balance.
2. Dissolve: Carefully add the weighed KH₂PO₄ to a clean 1-liter volumetric flask. Add a small amount of distilled water (about 500 mL) to dissolve the KH₂PO₄ completely. Swirl gently to aid dissolution.
3. Fill to the mark: Once the KH₂PO₄ is fully dissolved, carefully add more distilled water to bring the total volume up to the 1-liter mark on the volumetric flask.
4. Mix thoroughly: Stopper the flask and invert it several times to ensure a homogenous solution.
Important Considerations:
* Purity: Use KH₂PO₄ of known high purity. The calculation assumes 100% purity; impurities will affect the actual normality.
* Accuracy: Use an analytical balance for accurate weighing. The accuracy of the normality depends on the accuracy of the weighing and volume measurement.
* Water: Use high-purity distilled or deionized water.
* Temperature: The volume of solutions can change with temperature. Prepare the solution at the desired working temperature.
This procedure will yield approximately a 1N solution of KH₂PO₄. For very precise work, you might need to standardize the solution against a primary standard.