Simplified Normality Calculation Techniques

Oct 16, 2024

Lecture Notes: Simplified Calculation of Normality

Overview

  • The lecture discusses a simplified method for calculating the normality of a solution.
  • A formula is introduced to provide a quick way to get to the answer, contrasting with a longer method presented in a previous video.

Key Formula for Normality

  • Normality (N) =
    [ N = \frac{(\text{mass of solute in grams}) \times n}{(V \times \text{molecular weight of solute})} ]
    • Where:
      • mass of solute (M) = in grams
      • n = number of H⁺ ions (for acids) or OH⁻ ions (for bases) per formula unit
      • V = volume of the solution in liters
      • molecular weight = molar mass of the solute

Example Calculation: H₂SO₄

  1. Identify components
    • For H₂SO₄:
      • 2 H⁺ ions (n=2)
      • Mass (M) = 50 grams
      • Calculate molecular weight:
        • H: 2 × 1.008 = 2.016
        • S: 1 × 32.06 = 32.06
        • O: 4 × 16 = 64
        • Total = 98.076 grams/mole
  2. Apply formula
    • Normality = (50 g × 2) / (0.015 L × 98.076 g/mole)
    • Calculation:
      • = 100 / 1.47114
      • = 0.06797 N

Additional Resources

  • A formula sheet for various concentration formulas (normality, molarity, molality, etc.) will be available in the description.

Example Calculation: Calcium Hydroxide (Ca(OH)₂)

  1. Identify components
    • For Ca(OH)₂:
      • 2 OH⁻ ions (n=2)
      • Mass (M) = 1.5 grams
      • Calculate molecular weight:
        • Ca: 1 × 40.08 = 40.08
        • H: 2 × 1.008 = 2.016
        • O: 2 × 16 = 32
        • Total = 74.096 grams/mole
  2. Volume Conversion
    • Given: 850 mL = 0.85 L
  3. Apply formula
    • Normality = (1.5 g × 2) / (0.85 L × 74.096 g/mole)
    • Calculation:
      • = 3 / 63.9816
      • = 0.04763 N

Deriving the Formula for Normality

  1. Basic Definition
    • Normality = (grams equivalent weight of solute) / (liters of solution)
  2. Equivalent Weight (EW)
    • EW = (molecular weight) / n
  3. Rearranging the Formula
    • Normality = (M / EW) / V
    • Substitute EW with (molecular weight / n)
    • Final derived formula:
      [ N = \frac{(\text{mass of solute}) \times n}{(V \times \text{molecular weight})} ]

Conclusion

  • The derived formula simplifies the calculation of normality for both acids and bases.
  • Encouraged to refer to the older video for a longer method and to download the formula sheet for further study.

Full transcript