Preparation and standardization of molar and normal solutions of Sulphuric acid
Sulfuric acid (H2SO4) is a strong acid and can be used to prepare both molar and normal solutions. Here is a general procedure for the preparation and standardization of a 0.1 M sulfuric acid solution and a 0.1 N sulfuric acid solution:
Preparation of 0.1 M sulfuric acid solution:
- Determine the amount of sulfuric acid needed to prepare the solution. The molar mass of sulfuric acid is 98.08 g/mol, so for a 1-liter solution, 9.81 g of sulfuric acid is required.
- Add the required amount of sulfuric acid to a 1-liter volumetric flask.
- Add about 800 mL of distilled water to the flask and swirl gently to dissolve the sulfuric acid.
- Once the sulfuric acid is completely dissolved, add more distilled water until the solution reaches the 1-liter mark on the flask.
- Cap the flask and mix the solution thoroughly to ensure uniformity.
Standardization of 0.1 M sulfuric acid solution:
- Weigh about 0.1 g of primary standard sodium carbonate (Na2CO3) using an analytical balance and transfer it to a clean, dry Erlenmeyer flask.
- Add about 50 mL of distilled water to the flask and swirl gently to dissolve the Na2CO3.
- Add a few drops of phenolphthalein indicator to the solution.
- Titrate the Na2CO3 solution with the 0.1 M sulfuric acid solution until the pink color disappears.
- Record the volume of the sulfuric acid solution used for the titration.
Calculation:
The molar mass of Na2CO3 is 105.99 g/mol. The equation for the reaction between Na2CO3 and sulfuric acid is:
Na2CO3 + H2SO4 → Na2SO4 + H2O + CO2
From the balanced equation, we know that 1 mole of Na2CO3 reacts with 1 mole of H2SO4. Therefore, the number of moles of H2SO4 can be calculated from the volume of sulfuric acid solution used in the titration and the molarity of the solution.
The weight of Na2CO3 used in the titration can also be used to calculate the molarity of the sulfuric acid solution.
Standardization of 0.1 N sulfuric acid solution:
- Weigh about 0.63 g of primary standard potassium hydrogen phthalate (KHP) using an analytical balance and transfer it to a clean, dry Erlenmeyer flask.
- Add about 50 mL of distilled water to the flask and swirl gently to dissolve the KHP.
- Add a few drops of phenolphthalein indicator to the solution.
- Titrate the KHP solution with the 0.1 N sulfuric acid solution until the pink color disappears.
- Record the volume of the sulfuric acid solution used for the titration.
Calculation:
The molar mass of KHP is 204.23 g/mol. The equation for the reaction between KHP and sulfuric acid is:
KHP + H2SO4 → KHSO4 + H2O + CO2
From the balanced equation, we know that 1 mole of KHP reacts with 1 mole of H2SO4. Therefore, the number of moles of H2SO4 can be calculated from the volume of sulfuric acid solution used in the titration and the normality of the solution.
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