Making a Standard Solution of Sodium Carbonate

Introduction

• Objective: Prepare a standard solution of known concentration, specifically 0.1 mol/dm³ sodium carbonate.
• Equipment: 250 cm³ volumetric flask.

Steps to Prepare the Standard Solution

1. Measuring Sodium Carbonate

• Weighing by Difference:
  • Use a spatula to measure approximately 2.6 grams of anhydrous sodium carbonate.
  • Record the initial mass with the weighing boat.
  • Transfer the solid to a 100 cm³ beaker.
  • Re-weigh the empty weighing boat to calculate the exact mass of sodium carbonate.

2. Dissolving Sodium Carbonate

• Dissolution:
  • Add distilled water from a wash bottle to the beaker containing sodium carbonate.
  • Stir thoroughly until completely dissolved.

3. Transferring the Solution

• Use of Volumetric Flask:
  • Pour solution through a funnel into a 250 cm³ volumetric flask using a glass rod.
  • Ensure smooth drainage by raising the funnel.

4. Rinsing Technique

• Rinse and Transfer:
  • Rinse the beaker with distilled water and add to the flask. Repeat at least three times.
  • Rinse the funnel with distilled water to ensure complete transfer.

5. Finalizing the Solution

• Filling to the Mark:
  • Add distilled water up to the 250 cm³ mark.
  • Observe the meniscus at eye level for accuracy.
• Mixing:
  • Stopper and gently invert the flask several times to ensure uniform concentration.
• Labeling:
  • Clearly label the flask with the exact concentration of the solution.

Calculations for Concentration

• Molar Mass of Sodium Carbonate:
  • Determine the molar mass of anhydrous sodium carbonate.
• Amount of Substance:
  • Calculate using the formula:
    • ( \text{Amount of Substance} = \frac{\text{Mass of Sodium Carbonate}}{\text{Molar Mass}} )
• Concentration Calculation:
  • Use the volume of 250 cm³ (converted to dm³) to find concentration:
    • ( \text{Concentration} = \frac{\text{Amount of Substance}}{\text{Volume (dm³)}} )

Result

• Known Concentration: 0.0974 mol/dm³ sodium carbonate.