Question

Write the balanced chemical equations for the below reaction and identify the type of reaction in the case: Ethanol is burnt in air to form carbon dioxide, water and releases heat.

Answer 1

Balancing chemical reaction:

• The process of balancing the stoichiometric values on the involved in the reaction and outputs sides of a chemical equation.
• This is required because the chemical equation follows the principles of mass and momentum conservation.

Reaction when ethanol is burned in the air:

• Ethanol is categorized as a hydrocarbon because it contains a covalent link between hydrogen and carbon atoms.
• Carbon dioxide and water molecules are produced when a hydrocarbon is burnt in the presence of air.
• This is known as the combustion reaction.

Step 1: Write the chemical representation of reaction

• ${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\left(\mathrm{l}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to {\mathrm{CO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)+\mathrm{Heat}$

Step 2:Now balance the number of carbon atoms:

• ${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\left(\mathrm{l}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2{\mathrm{CO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)+\mathrm{Heat}$

Step 3: Now balance no. of hydrogen atoms on both sides:

• ${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\left(\mathrm{l}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2{\mathrm{CO}}_2\left(\mathrm{g}\right)+3{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)+\mathrm{Heat}$

Step 4:Now balance no. of oxygen atoms on both sides:

• ${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\left(\mathrm{l}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2{\mathrm{CO}}_2\left(\mathrm{g}\right)+3{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)+\mathrm{Heat}$
• Since the no. of atoms of all elements in both the product and reactant side is equal.

So the balanced equation is: ${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\left(\mathrm{l}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2{\mathrm{CO}}_2\left(\mathrm{g}\right)+3{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)+\mathrm{Heat}$

Combustion reaction :

• Combustion is a chemical process in which any fuel reacts with air (oxidant) to yield heat energy.
• The combustion exothermic reaction can be stated as follows:

$\mathrm{Hydrocarbon}+\mathrm{Oxygen}\to \mathrm{Carbon}\mathrm{Dioxide}+\mathrm{Water}+\mathrm{Heat}\mathrm{Energy}$

Examples of combustion :

• Wood or coal burning for domestic purposes
• Using petrol or diesel to power vehicles such as an automobile