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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
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
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)
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
Volume Conversion
Given: 850 mL = 0.85 L
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
Basic Definition
Normality = (grams equivalent weight of solute) / (liters of solution)
Equivalent Weight (EW)
EW = (molecular weight) / n
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.
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