Complete Combustion of Alcohol

The aim of this experiment is to study the combustion reaction of an alcohol.

Alcohol undergoes oxidation upon burning in the presence of excess oxygen. This process is known as combustion.

An oxidation process involves the gain of oxygen by elements or compounds. During combustion, the carbon of ethanol gets oxidised to carbon dioxide. This gas can be confirmed by passing it over freshly prepared lime water, which turns milky.

The combustion reaction of ethanol can be represented as:

C₂H₅OH (l) + 3O₂ (g) → 2CO₂ (g) + 3H₂O (g)

Apparatus and materials are required

Apparatus

• Beaker
• Spirit lamp
• Lighter
• Funnel 
• Rubber tube
• Jet
• Retort stand

Chemicals

• Ethanol
• Freshly prepared lime water

To perform this experiment, steps to be followed in the following manner:

Procedure

• Take ethanol as the fuel in a spirit lamp. 
• Burn the lamp and cover it with an inverted funnel. 
• Fix the stem of the inverted funnel with a rubber tubing, which is attached to a jet on the other end. 
• Pass the evolved vapours through freshly prepared lime water. 
• Observe any condensation of water vapour on the inner surface of the inverted funnel. 
• Observe the colour change in the lime water.

In this experiment, we learnt that

• Ethanol, on burning in the presence of oxygen, forms carbon dioxide and water.  
• The carbon dioxide gas was confirmed by passing it through the lime water. It turns milky due to the formation of calcium carbonate.
• The condensation of water can be seen in the inner walls of the funnel.
• This oxidation reaction is known as combustion.

C₂H₅OH (l)+3O₂ (g)2CO₂ (g)+3H₂O (g)

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