Introduction to Stoichiometry

Types of Stoichiometry Conversions

1. Moles to Moles
   • Conversion from moles of substance A to moles of substance B using the mole ratio from the balanced equation.
2. Moles to Grams or Grams to Moles
   • Converting moles of substance A to grams of substance B or vice versa.
3. Grams to Grams
   • Converting grams of substance A to grams of substance B, involving three steps.

Example Problems and Solutions

Problem 1: SO2 + O2 → SO3

• Balanced Chemical Equation: 2 SO2 + O2 → 2 SO3
• Part A: 3.4 moles of SO2 forms 3.4 moles of SO3 due to a 1:1 mole ratio.
• Part B: 4.7 moles of SO2 requires 2.35 moles of O2 (using a 2:1 molar ratio).

Problem 2: C3H8 + O2 → CO2 + H2O

Part A

• Balanced Chemical Equation: C3H8 + 5 O2 → 3 CO2 + 4 H2O
• Conversion: 2.8 moles of C3H8 to grams of CO2.
  • Molar mass of CO2 is 44.01 g/mol.
  • Result: 369.5 grams of CO2.

Part B

• Conversion: 3.8 moles of C3H8 to grams of O2.
  • Molar mass of O2 is 32 g/mol.
  • Result: 608 grams of O2.

Part C

• Conversion: 25 grams of C3H8 to moles of H2O.
  • Molar mass of C3H8 is 44.094 g/mol.
  • Result: 2.27 moles of H2O.

Part D

• Conversion: 38 grams of H2O to moles of CO2.
  • Molar mass of H2O is 18.016 g/mol.
  • Result: 1.58 moles of CO2.

Problem 3: Al + Cl2 → AlCl3

Part A

• Balanced Chemical Equation: 2 Al + 3 Cl2 → 2 AlCl3
• Conversion: 35 grams of Al to grams of AlCl3.
  • Molar mass of AlCl3 is 133.33 g/mol.
  • Result: 172.96 grams of AlCl3.

Part B

• Conversion: 42.8 grams of Al to grams of Cl2.
  • Molar mass of Cl2 is 70.9 g/mol.
  • Result: 168.75 grams of Cl2.

Key Concepts

• Mole Ratio: Derived from the coefficients of a balanced chemical equation.
• Molar Mass: Used to convert between grams and moles.
• Stoichiometry: Essential for predicting the amount of products/reactants in chemistry.

These examples cover the common stoichiometry problems encountered in chemistry, showcasing conversions between moles and grams for different substances.