Combustion Reactions Lecture

Overview

• Combustion Reactions: Typically involves hydrocarbons and oxygen.
• Products: Carbon dioxide (CO2) and water (H2O) are the primary products if complete combustion occurs.
• Complete Combustion: Occurs with excess oxygen, resulting in only CO2 and H2O.
• Incomplete Combustion: May produce carbon monoxide (CO) if oxygen is limited.

Example Reactions

Methane Combustion

1. Reactants: Methane (CH4) and oxygen (O2).
2. Products: CO2 and H2O.
3. Balancing:
   • Carbon: 1 C on both sides.
   • Hydrogen: 4 H on left, needs 2 moles of H2O on right.
   • Oxygen: 4 O on right, 2 O2 needed on left.

Propane Combustion

1. Reactants: Propane (C3H8) and O2.
2. Products: CO2 and H2O.
3. Balancing:
   • Carbon: 3 C on left, 3 CO2 on right.
   • Hydrogen: 8 H on left, 4 H2O on right.
   • Oxygen: 10 O on right, 5 O2 on left.

Ethane Combustion

1. Reactants: Ethane (C2H6) and O2.
2. Products: CO2 and H2O.
3. Balancing:
   • Carbon: 2 C on left, 2 CO2 on right.
   • Hydrogen: 6 H on left, 3 H2O on right.
   • Oxygen: Balancing gives a fraction (7/2 O2), multiply entire equation by 2 to clear fraction.
   • Final: 2 C2H6 + 7 O2 → 4 CO2 + 6 H2O.

Butane Combustion

1. Reactants: Butane (C4H10) and O2.
2. Products: CO2 and H2O.
3. Balancing:
   • Carbon: 4 C on left, 4 CO2 on right.
   • Hydrogen: 10 H on left, 5 H2O on right.
   • Oxygen: Initial fraction (13/2 O2), clear by multiplying entire equation by 2.
   • Final: 2 C4H10 + 13 O2 → 8 CO2 + 10 H2O.

Complex Hydrocarbon (C, H, O) Combustion

1. Reactants: Hydrocarbon with C, H, and O components.
2. Products: Always CO2 and H2O.
3. Balancing:
   • Follow similar steps: Balance C first, then H, and adjust O as needed.
   • Use fractions if necessary, and multiply entire equation to clear fractions.

Propanol Combustion

1. Reactants: Propanol (contains C, H, O) and O2.
2. Products: CO2 and H2O.
3. Balancing:
   • Carbon: 3 C on left, 3 CO2 on right.
   • Hydrogen: 8 H on left, 4 H2O on right.
   • Oxygen: Results in fraction (9/2 O2), multiply entire equation to clear fraction.
   • Final: 2 C3H8O + 9 O2 → 6 CO2 + 8 H2O.

Key Takeaways

• Balancing Steps:
  1. Balance carbon atoms first.
  2. Then balance hydrogen atoms.
  3. Balance oxygen atoms last.
  4. Use fractions if needed and clear by multiplying.
• Practice: Essential for mastering combustion reactions.