Mass Percent Composition and Its Application

Definition

• Mass Percent Composition: A way to describe the makeup of a molecule.
• Formula:
  • Mass percent of element X in a compound = (mass of element X / mass of compound) × 100%

Example: Sodium in Sodium Chloride

• Molecular Weights:
  • Sodium (Na) has a molar mass of 22.99 g/mol.
  • Chlorine (Cl) has a molar mass of 35.45 g/mol.
• Total Molar Mass of NaCl:
  • NaCl = 22.99 g/mol (Na) + 35.45 g/mol (Cl) = 58.44 g/mol
• Calculating Mass Percent of Sodium in NaCl:
  • Mass percent Na = (22.99 / 58.44) × 100 = 39.34%

Applications

• Utility:
  • Used in laboratories to prepare solutions.
  • Helps determine the amount of a component in larger samples for extraction or consumption analysis.

FDA Recommendations Example

• FDA Sodium Intake Recommendation:
  • The recommended consumption is less than 2,300 mg of sodium per day (note: this may be an outdated number).
• Problem Scenario:
  • If a person consumes 8 grams of NaCl, how much sodium is ingested?
  • Calculation:
    • 39.34% of 8 grams = 0.3934 × 8 = 3.1472 grams of sodium
    • Convert grams to milligrams: 3.1472 grams × 1,000 = 3,147 milligrams
  • Comparison to FDA Recommendation:
    • 3,147 mg is significantly higher than the daily recommendation (approximately 1.5 times higher).

Conclusion

• Mass percent composition is crucial for various calculations, including dietary analysis and laboratory preparations.
• Understanding this concept can help in making informed decisions regarding chemical usage and consumption.