Question

What is the chemical equation to show the combustion reaction of ethanol?

Answer 1

Hint As we know that combustion reaction of ethanol is a type of redox reaction, during which electrons are transferred between two reactants participating in it. We can identify this transfer of electrons by observing the changes in the oxidation states of the reacting species.

Complete answer:

Let us firstly discuss the combustion reaction. A combustion reaction is the reaction in which a substance responds with oxygen gas. And energy is delivered as light. In combustion reaction oxygen is one of the reactants.
When ethanol is reacted with oxygen, then carbon dioxide gas is released along with water. We can say that this reaction is a redox reaction. The combustion reaction of ethanol can be written as:
${{C}_{2}}{{H}_{5}}OH\left( l \right)+3{{O}_{2}}\left( g \right)\to 2C{{O}_{2}}\left( g \right)+3{{H}_{2}}O\left( l \right)+heat$
As we know that redox reactions have mainly two parts. These are oxidised half and reduced half. It is found that the oxidised half of the reaction loses electrons and hence the oxidation number of the species increases. Whereas, the reduced half of the reaction accepts electrons and hence the oxidation number of the species decreases.

Hence, we can write the chemical equation to show the combustion reaction of ethanol as:
${{C}_{2}}{{H}_{5}}OH\left( l \right)+3{{O}_{2}}\left( g \right)\to 2C{{O}_{2}}\left( g \right)+3{{H}_{2}}O\left( l \right)+heat$

Note: As we know that in an oxidation reaction, the electrons are lost from an atom. An oxidizing agent is one which gains electrons. Whereas, in reduction reaction, the electrons are gained from an atom. A reducing agent is one which loses electrons.