Titration Calculations Lecture Notes

Introduction

• Refresher: If you need to refresh your memory on how to carry out titrations, refer to part 1.
• Part 2 covers titration calculations.
• Purpose: Determine the concentration of an unknown solution.

Example 1

• Given:
  • 25 cubic centimeters (cm³) of unknown solution in a conical flask.
  • 20 cm³ of a known solution with a concentration of 0.5 mol/dm³.
• Steps:
  1. Convert volumes to cubic decimeters:
     • 25 cm³ = 0.025 dm³
     • 20 cm³ = 0.02 dm³
  2. Calculate moles of known solution:
     • Moles = Concentration × Volume
     • 0.5 mol/dm³ × 0.02 dm³ = 0.01 mole
  3. Calculate concentration of unknown solution:
     • Concentration = Moles/Volume
     • 0.01 mole/0.025 dm³ = 0.04 mol/dm³

Formula for Quick Calculation

• Equation:
  • Concentration of unknown = (Concentration of known × Volume of known) / Volume of unknown
  • Example calculation: 0.5 × 20 / 25 = 0.4 mol/dm³
• Note: Using this formula may not demonstrate understanding of the concepts.

Example 2 with Balanced Equation

• Balanced Equation: 2 NaOH + H₂SO₄ → Na₂SO₄ + 2 H₂O
• Steps:
  1. Convert volumes to cubic decimeters:
     • 20 cm³ NaOH = 0.02 dm³
     • 40 cm³ H₂SO₄ = 0.04 dm³
  2. Calculate moles of NaOH:
     • 0.5 mol/dm³ × 0.02 dm³ = 0.01 mole
  3. Calculate concentration of H₂SO₄:
     • 0.01 mole/0.04 dm³ = 0.25 mol/dm³
  4. Adjust for reaction stoichiometry (2:1 ratio):
     • 0.25 mol/dm³ divided by 2 = 0.125 mol/dm³

Practice Problem

• Try calculating yourself. Expected result: 0.3 mol/dm³

Conclusion

• Titration calculations help determine the exact concentration of an unknown solution.
• Requirements:
  • Complete a titration to obtain known solution's volume and concentration.
  • Know the volume of the unknown solution to compute its concentration.