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Understanding Stoichiometry Conversions in Chemistry

Apr 25, 2025

Introduction to Stoichiometry

Types of Conversions in Chemical Reactions

  1. Moles of Substance A to Moles of Substance B

    • Identify the mole ratio (M ratio).
    • Single-step conversion.

  2. Moles of Substance A to Grams of Substance B

    • Or Grams of Substance A to Moles of Substance B.
    • Two-step conversion.

  3. Grams of Substance A to Grams of Substance B

    • Three-step conversion.

Example Problems

Problem 1: Sulfur Dioxide and Sulfur Trioxide

  • Reaction: SO₂ + O₂ → SO₃
  • Balanced Equation: 2 SO₂ + O₂ → 2 SO₃

Part A: Convert Moles of SO₂ to Moles of SO₃

  • Given: 3.4 moles of SO₂
  • M ratio: 2:2
  • Result: 3.4 moles of SO₃

Part B: Convert Moles of SO₂ to Moles of O₂

  • Given: 4.7 moles of SO₂
  • M ratio: 2:1
  • Result: 2.35 moles of O₂

Problem 2: Propane and Carbon Dioxide

  • Reaction: C₃H₈ + O₂ → CO₂ + H₂O
  • Balanced Equation: C₃H₈ + 5 O₂ → 3 CO₂ + 4 H₂O

Part A: Convert Moles of Propane to Grams of CO₂

  • Given: 2.8 moles of C₃H₈
  • M ratio: 1:3
  • Molar Mass of CO₂: 44.01 g/mol
  • Result: 369.5 grams of CO₂

Part B: Convert Moles of Propane to Grams of O₂

  • Given: 3.8 moles of C₃H₈
  • M ratio: 1:5
  • Molar Mass of O₂: 32 g/mol
  • Result: 608 grams of O₂

Part C: Convert Grams of Propane to Moles of H₂O

  • Given: 25 grams of C₃H₈
  • Molar Mass of C₃H₈: 44.094 g/mol
  • M ratio: 1:4
  • Result: 2.27 moles of H₂O

Part D: Convert Grams of H₂O to Moles of CO₂

  • Given: 38 grams of H₂O
  • Molar Mass of H₂O: 18.016 g/mol
  • M ratio: 4:3
  • Result: 1.58 moles of CO₂

Problem 3: Aluminum and Chlorine

  • Reaction: Al + Cl₂ → AlCl₃
  • Balanced Equation: 2 Al + 3 Cl₂ → 2 AlCl₃

Part A: Convert Grams of Al to Grams of AlCl₃

  • Given: 35 grams of Al
  • Molar Mass of Al: 26.98 g/mol
  • Molar Mass of AlCl₃: 133.33 g/mol
  • Result: 172.96 grams of AlCl₃

Part B: Convert Grams of Al to Grams of Cl₂

  • Given: 42.8 grams of Al
  • Molar Mass of Cl₂: 70.9 g/mol
  • M ratio: 2:3
  • Result: 168.75 grams of Cl₂

Summary

  • Mole-to-Mole Conversions: Conversion of moles between substances.
  • Mole-to-Gram/Gram-to-Mole Conversions: Conversion between moles and grams.
  • Gram-to-Gram Conversions: Conversion of grams between different substances.

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