Describe the combustion of ethanol

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Combustion of Ethanol - IGCSE Chemistry

Combustion of Ethanol

Objective

Describe the combustion of ethanol.

Chemical Equation

The combustion of ethanol (C2H5OH) is a chemical reaction with oxygen (O2) to produce carbon dioxide (CO2) and water (H2O), releasing energy in the form of heat and light.

The balanced chemical equation for this reaction is:

$$C_2H_5OH(g) + 3O_2(g) \rightarrow 2CO_2(g) + 3H_2O(g)$$

Conditions for Combustion

For ethanol to burn, three things are necessary:

  • Fuel: Ethanol (C2H5OH)
  • Oxidising Agent: Oxygen (O2)
  • Ignition: A source of heat to initiate the reaction (e.g., a Bunsen burner flame). The ignition temperature of ethanol is approximately 363 °C.

Observations during Combustion

When ethanol is combusted, the following observations can be made:

  • Flame: A clean, blue flame is produced. This indicates complete combustion.
  • Luminous Flame: If there is insufficient oxygen, the flame may be pale or yellow-orange. This indicates incomplete combustion.
  • Heat Release: A significant amount of heat is released, which can be felt.
  • Formation of Products: The products, carbon dioxide and water, are produced as gases.

Complete vs. Incomplete Combustion

Complete Combustion: Occurs when there is a sufficient supply of oxygen. All the carbon in ethanol is converted to carbon dioxide, and all the hydrogen is converted to water.

Incomplete Combustion: Occurs when there is a limited supply of oxygen. This results in the formation of carbon monoxide (CO) in addition to carbon dioxide and water. Carbon monoxide is a poisonous gas.

Products of Combustion

The main products of the complete combustion of ethanol are:

  • Carbon Dioxide (CO2): A greenhouse gas.
  • Water (H2O): A gas at the combustion temperature.
  • Heat: Released as energy.

The products of incomplete combustion include:

  • Carbon Dioxide (CO2)
  • Water (H2O)
  • Carbon Monoxide (CO): A poisonous, colourless gas.
  • Soot (C): Unburnt carbon particles.

Diagram of Ethanol Combustion

Suggested diagram: A diagram showing ethanol vapour reacting with oxygen in the presence of a flame, producing carbon dioxide and water. Arrows indicate the flow of reactants and products.

Summary Table

Aspect Description
Reactants Ethanol (C2H5OH) and Oxygen (O2)
Products (Complete Combustion) Carbon Dioxide (CO2) and Water (H2O)
Products (Incomplete Combustion) Carbon Dioxide (CO2), Water (H2O), Carbon Monoxide (CO), Soot (C)
Conditions Required Fuel (Ethanol), Oxidising Agent (Oxygen), Ignition Source
Observations Clean blue flame (complete), Pale/yellow-orange flame (incomplete), Heat release, Formation of gases