Overview
This lecture explains how to use the dilution formula to find the missing volume when preparing solutions from a stock concentration.
Dilution Formula Basics
- The dilution formula is Q₁ × C₁ = Q₂ × C₂, where Q = volume, C = concentration.
- This formula allows calculation of unknown volumes or concentrations required for dilutions.
Example 1: Calculating Stock Solution Volume
- Given: 10% stock solution, 500 mL target volume, 2.5% desired concentration.
- Use formula: Q₁ × 10 = 500 × 2.5.
- Solve for Q₁: Q₁ = (500 × 2.5) / 10 = 125 mL.
- 125 mL of 10% stock is needed to make 500 mL of 2.5% solution.
Example 2: Practice Problem
- Given: 15% stock solution, 1000 mL target volume, 3% desired concentration.
- Use formula: Q₁ × 15 = 1000 × 3.
- Solve for Q₁: Q₁ = (1000 × 3) / 15 = 200 mL.
Example 3: Additional Practice
- Given: 20% stock solution, 800 mL target volume, 4% desired concentration.
- Use formula: Q₁ × 20 = 800 × 4.
- Solve for Q₁: Q₁ = (800 × 4) / 20 = 160 mL.
Key Terms & Definitions
- Dilution Formula — An equation used to calculate concentrations or volumes needed for diluting solutions: Q₁ × C₁ = Q₂ × C₂.
- Stock Solution — A concentrated solution used to prepare dilutions.
- Target Solution — The final, less concentrated solution to be prepared.
Action Items / Next Steps
- Practice solving dilution problems using the formula.
- Complete any provided questions to test your understanding.
- Review steps to ensure accurate medication preparation.