⚗️

Basics of Stoichiometry and Conversions

May 22, 2025

View transcript

Introduction to Stoichiometry

Types of Conversions

  • Mole-to-Mole Conversion: Convert moles of substance A to moles of substance B using the mole ratio from the balanced equation.
  • Mole-to-Gram or Gram-to-Mole Conversion: Convert moles of substance A to grams of substance B or grams of substance A to moles of substance B.
  • Gram-to-Gram Conversion: Convert grams of substance A to grams of substance B, involving three steps.

Problem Examples

Problem 1: Sulfur Dioxide and Oxygen Reaction

  • Reaction: [\text{SO}_2 + \text{O}_2 \rightarrow \text{SO}_3]
  • Balanced Equation: [2\text{SO}_2 + \text{O}_2 \rightarrow 2\text{SO}_3]
  • Example A: Convert 3.4 moles of (\text{SO}_2) to moles of (\text{SO}_3).
    • Mole ratio: 2:2, answer = 3.4 moles (\text{SO}_3).
  • Example B: Convert 4.7 moles of (\text{SO}_2) to moles of (\text{O}_2).
    • Mole ratio: 2:1, answer = 2.35 moles (\text{O}_2).

Problem 2: Propane and Oxygen Reaction

  • Reaction: [\text{C}_3\text{H}_8 + \text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O}]
  • Balanced Equation: [\text{C}_3\text{H}_8 + 5\text{O}_2 \rightarrow 3\text{CO}_2 + 4\text{H}_2\text{O}]
  • Example A: Convert 2.8 moles of propane to grams of (\text{CO}_2).
    • Steps: Convert moles (\text{C}_3\text{H}_8) to moles (\text{CO}_2), then moles (\text{CO}_2) to grams.
    • Answer: 369.5 grams (\text{CO}_2).
  • Example B: Convert 3.8 moles of propane to grams of (\text{O}_2).
    • Steps: Convert to moles (\text{O}_2), then to grams.
    • Answer: 608 grams (\text{O}_2).
  • Example C: Convert 25 grams of (\text{C}_3\text{H}_8) to moles of (\text{H}_2\text{O}).
    • Answer: 2.27 moles (\text{H}_2\text{O}).
  • Example D: Convert 38 grams of (\text{H}_2\text{O}) to moles of (\text{CO}_2).
    • Answer: 1.58 moles (\text{CO}_2).

Problem 3: Aluminum and Chlorine Reaction

  • Reaction: [\text{Al} + \text{Cl}_2 \rightarrow \text{AlCl}_3]
  • Balanced Equation: [2\text{Al} + 3\text{Cl}_2 \rightarrow 2\text{AlCl}_3]
  • Example A: Convert 35 grams of aluminum to grams of (\text{AlCl}_3).
    • Steps: Grams to moles, moles of (\text{AlCl}_3), moles to grams.
    • Answer: 172.96 grams (\text{AlCl}_3).
  • Example B: Convert 42.8 grams of aluminum to grams of (\text{Cl}_2).
    • Steps: Grams to moles (\text{Al}), moles (\text{Cl}_2), moles to grams.
    • Answer: 168.75 grams (\text{Cl}_2).

Key Concepts

  • Mole Ratios: Derived from coefficients in balanced equations, used to convert between substances.
  • Molar Mass: Used to convert between grams and moles.
  • Stoichiometry: Critical for understanding chemical reactions and conversions between different substances.

Conclusion: Understanding stoichiometry is essential for solving common chemistry problems involving conversions between moles and grams of substances.

Full transcript