Gravimetric analysis is a technique for determining the quantity of an analyte based on the mass of a solid. To estimate sulfate ions (SO₄²⁻) as barium sulfate (BaSO₄) gravimetrically, follow these steps:
### Safety Precautions
1. **Safety Gear**: Wear appropriate personal protective equipment like lab coat, safety goggles, and gloves.
2. **Ventilation**: Ensure the workspace is well-ventilated.
### Materials Required
1. Sample containing SO₄²⁻ ions
2. Barium chloride (BaCl₂) solution
3. Dilute hydrochloric acid (HCl)
4. Distilled or deionized water
5. Analytical balance
6. Beakers, filtration apparatus, and crucibles
7. Hot plate or burner
### Procedure
#### 1. Preparation of Sample Solution
- Dissolve a known mass of the sample containing sulfate ions in distilled water.
- Transfer the solution into a 250 mL beaker. If necessary, slightly acidify with dilute HCl to prevent the formation of interfering precipitates.
#### 2. Precipitation of BaSO₄
- Heat the sample solution to near boiling.
- Slowly add a slight excess of warm BaCl₂ solution with continuous stirring. The chemical reaction is:
\[
\text{Ba}^{2+} + \text{SO}_4^{2-} \rightarrow \text{BaSO}_4 \text{(s)}
\]
- Allow the mixture to stand in a warm place for at least 30 minutes to ensure complete precipitation. Continue to stir occasionally.
#### 3. Digestion
- Digest the precipitate by keeping the beaker warm (but not boiling) for an additional hour. This helps in forming larger BaSO₄ particles, which are easier to filter.
#### 4. Filtration
- Weigh a clean, dry filter paper or a pre-weighed Gooch crucible with a filter mat.
- Filter the BaSO₄ precipitate through the filter paper or the crucible using a Büchner funnel.
- Rinse the beaker and the precipitate several times with hot distilled water to remove soluble impurities.
#### 5. Washing the Precipitate
- Wash the precipitate with dilute HCl followed by several washings with hot distilled water to ensure complete removal of chloride ions and other impurities.
#### 6. Drying
- Dry the filter paper with BaSO₄ precipitate in an oven at 105-110°C until constant weight is achieved. If using a Gooch crucible, dry the crucible with the precipitate.
- Cool the dried precipitate in a desiccator to room temperature.
#### 7. Weighing
- Weigh the filter paper or crucible with the dried BaSO₄ precipitate using an analytical balance.
- Calculate the mass of the BaSO₄ by subtracting the mass of the empty filter paper or crucible from the total mass.
### Calculation
- Use the mass of BaSO₄ to calculate the mass of SO₄²⁻ based on the molar mass of sulfate and barium sulfate. The molar masses are approximately: BaSO₄ = 233.39 g/mol and SO₄²⁻ = 96.06 g/mol.
\[
\text{Mass of SO}_4^{2-} = \left(\frac{\text{Mass of BaSO}_4 \, (g)}{\text{Molar mass of BaSO}_4 \, (g/mol)} \right) \times \text{Molar mass of SO}_4^{2-} \, (g/mol)
\]
### Notes
- Ensure the BaSO₄ precipitate is pure and dry to get accurate results.
- Avoiding contamination and loss of precipitate during filtration and transfer processes is crucial for precise measurements.
This method provides an accurate and reliable estimation of sulfate ions in a sample by measuring the mass of the formed barium sulfate precipitate.
Explain the steps involving the estimation of so2-4 as a baso4 gravimetrically
1 answer