Preparation of 0.05 Molar Solution of Mohr's Salt
To prepare a 0.05 Molar (M) solution of Mohr's salt (Ferrous Ammonium Sulfate, (NH4)2Fe(SO4)2·6H2O), follow these steps:
- Calculate the molar mass of Mohr's salt:
- (NH4)2: 2 × 14.01 g/mol
- Fe: 55.85 g/mol
- (SO4)2: 2 × (32.07 + 4 × 16.00) g/mol
- 6H2O: 6 × 18.02 g/mol
- Total = 392.17 g/mol
- For 1 liter of 0.05 M solution:
- Required mass = Molarity × Molar mass = 0.05 mol/L × 392.17 g/mol = 19.6085 g
- Weigh 19.61 g of Mohr's salt and dissolve it in distilled water, making the volume up to 1 liter.
Determining Molarity and Strength of KMnO4 Solution
To find the molarity and strength of the given KMnO4 solution using the prepared Mohr's salt solution:
- Titration Process:
- Take a known volume (e.g., 25 mL) of the KMnO4 solution.
- Titrate it with the Mohr's salt solution. The reaction is:
- \( \text{MnO}_4^- + 5 \text{Fe}^{2+} \rightarrow \text{Mn}^{2+} + 5 \text{Fe}^{3+} \)
- Stoichiometry:
- 1 mole of KMnO4 reacts with 5 moles of Fe²⁺ from Mohr's salt.
- Calculate Molarity of KMnO4:
- If 'V' mL of Mohr's salt is used in titration, the moles of Mohr's salt:
- Moles = Volume (L) × Molarity = (V/1000) × 0.05
- Moles of KMnO4 = Moles of Mohr's salt / 5
- Calculate Strength:
- Strength (g/L) of KMnO4 can be calculated using its molar mass (158.04 g/mol):
- Strength = Moles × Molar mass
This method allows you to determine the molarity and strength of KMnO4 solution accurately.