Introduction to Stoichiometry

Key Concepts:

• Stoichiometry involves three main types of conversions in chemical reactions:
  1. Moles of A to Moles of B
     • Requires the mole ratio from the balanced equation.
  2. Moles of A to Grams of B or Grams of A to Moles of B
     • Involves conversion using molar mass.
  3. Grams of A to Grams of B
     • Typically a three-step process involving conversion to moles and using mole ratios.

Problem 1: Sulfur Dioxide and Oxygen Reaction

Part A:

• Reaction: ( 2SO_2 + O_2 \rightarrow 2SO_3 )
• Given: 3.4 moles of ( SO_2 )
• Find: Moles of ( SO_3 )
• Mole Ratio: 2:2 (( SO_2 ) to ( SO_3 ))
• Calculation: ( 3.4 \text{ moles of } SO_3 )

Part B:

• Given: 4.7 moles of ( SO_2 )
• Find: Moles of ( O_2 )
• Mole Ratio: 2:1 (( SO_2 ) to ( O_2 ))
• Calculation: ( 2.35 \text{ moles of } O_2 )

Problem 2: Propane and Oxygen Reaction

Part A:

• Reaction: ( C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O )
• Given: 2.8 moles of propane
• Find: Grams of ( CO_2 )
• Steps:
  1. Convert moles ( C_3H_8 ) to moles ( CO_2 ) using mole ratio (1:3)
  2. Convert moles ( CO_2 ) to grams using molar mass (44.01 g/mol)
• Result: 369.5 grams of ( CO_2 )

Part B:

• Given: 3.8 moles of propane
• Find: Grams of ( O_2 )
• Steps:
  1. Convert moles ( C_3H_8 ) to moles ( O_2 ) using mole ratio (1:5)
  2. Convert moles ( O_2 ) to grams using molar mass (32 g/mol)
• Result: 608 grams of ( O_2 )

Part C:

• Given: 25 grams of propane
• Find: Moles of ( H_2O )
• Steps:
  1. Convert grams ( C_3H_8 ) to moles using molar mass (44.094 g/mol)
  2. Use mole ratio (1:4) to convert to moles ( H_2O )
• Result: 2.27 moles ( H_2O )

Part D:

• Given: 38 grams of ( H_2O )
• Find: Moles of ( CO_2 )
• Steps:
  1. Convert grams ( H_2O ) to moles using molar mass (18.016 g/mol)
  2. Use mole ratio (3:4) to convert to moles ( CO_2 )
• Result: 1.58 moles ( CO_2 )

Problem 3: Aluminum and Chlorine Reaction

Part A:

• Reaction: ( 2Al + 3Cl_2 \rightarrow 2AlCl_3 )
• Given: 35 grams of ( Al )
• Find: Grams of ( AlCl_3 )
• Steps:
  1. Convert grams ( Al ) to moles using molar mass (26.98 g/mol)
  2. Use mole ratio (2:2) to convert to moles ( AlCl_3 )
  3. Convert to grams ( AlCl_3 ) using molar mass (133.33 g/mol)
• Result: 172.96 grams of ( AlCl_3 )

Part B:

• Given: 42.8 grams of ( Al )
• Find: Grams of ( Cl_2 )
• Steps:
  1. Convert grams ( Al ) to moles
  2. Use mole ratio (2:3) to convert to moles ( Cl_2 )
  3. Convert to grams ( Cl_2 ) using molar mass (70.9 g/mol)
• Result: 168.75 grams ( Cl_2 )

Conclusion:

• Learned how to perform basic stoichiometry conversions in chemistry.
• Covered molar conversions and mass-mass conversions in typical reactions.