Concentration Measurement Methods

Importance of Conventions in Measurement

• Goal: Report values neatly without decimals or extraneous exponents.
• Example: pH scale
  • Reports hydronium concentrations as small integers (e.g., 7) rather than tiny numbers with inconvenient exponents.

Reporting Tiny Concentrations

• Essential for health and safety.
• Pollutants: Present in air and water at minuscule amounts.
  • Requires special concentration units like PPM (parts per million) and PPB (parts per billion).

Understanding PPM and PPB

• PPM: 1 gram of solute per 1 million grams of solution.
• PPB: 1 gram of solute per 1 billion grams of solution.

Example: Sulfur Dioxide in the Atmosphere

• Scenario: Sulfur dioxide concentration at 2 PPM.
• Calculation to find volume of atmosphere containing 1 gram of sulfur dioxide:
  1. If 2 grams of SO2 in 1 million grams of air, then 1 gram is in 500,000 grams.
  2. Given air density of 0.0012 g/cm³:
     • Volume = (500,000 \text{ g} \times \frac{1 \text{ cm}^3}{0.0012 \text{ g}} = 4.17 \times 10^9 \text{ cm}^3)
     • Convert to cubic meters: ≈ 4,170 m³
     • Corresponds to a cubic area with side length ≈ 16m (longer than a school bus).

Relevance of PPM and PPB

• Provide a practical way to express small concentrations.
• Example: Lead concentration in water
  • Maximum level before action is required: 15 PPB
  • Expressed as 15 PPB, it's a manageable number compared to other concentration units.

Conclusion

• PPM and PPB help in reporting tiny, yet relevant concentrations for health and environmental safety.
• Understanding these units is crucial for evaluating pollutant levels and ensuring water and air quality.