Question

When CNG undergoes complete combustion, the products formed are:
A. ${\rm{C}}{{\rm{O}}_{\rm{2}}}$ and ${{\rm{H}}_{\rm{2}}}{\rm{O}}$
B. ${\rm{C}}{{\rm{O}}_{\rm{2}}}$, ${\rm{S}}{{\rm{O}}_{\rm{2}}}$ and ${{\rm{H}}_{\rm{2}}}{\rm{O}}$
C. ${\rm{C}}{{\rm{O}}_{\rm{2}}}$ only
D. ${\rm{C}}{{\rm{O}}_{\rm{2}}}$, ${\rm{CO}}$ and ${{\rm{H}}_{\rm{2}}}{\rm{O}}$

Answer 1

We know that combustion is the process where a substance undergoes burning in presence of oxygen to result in light and heat. The substances which can undergo combustion are termed as combustible substances. All hydrocarbons (fuels) are combustible substances.

Complete step by step answer:
Let’s discuss CNG in detail. The full form of CNG is Compressed Natural Gas. It is predominately methane. The chemical formula of methane is ${\rm{C}}{{\rm{H}}_{\rm{4}}}$. The nature of CNG is colorless, odourless and non-toxic. This gas is lighter than air.

We know that, when a hydrocarbon undergoes combustion reaction carbon dioxide and water forms. Here, methane $\left( {{\rm{C}}{{\rm{H}}_{\rm{4}}}} \right)$
is a hydrocarbon. And we know, in complete combustion reaction hydrocarbons undergo reaction in excess air. The excess air means that there is enough oxygen to cause the conversion of all carbons to carbon dioxide. So, the complete combustion of CNG produces water and carbon dioxide.

The reaction is,

${\rm{C}}{{\rm{H}}_{\rm{4}}} + 2{{\rm{O}}_{\rm{2}}} \to {\rm{C}}{{\rm{O}}_{\rm{2}}} + 2{{\rm{H}}_{\rm{2}}}{\rm{O}} + {\rm{energy}}$

So, the correct answer is Option A.

Additional Information:
The combustion requires the oxidation (donates electrons) of fuel. Oxidizers are the molecule that can accept electrons. Oxygen is a great oxidizer because of its higher electronegativity. Therefore, oxygen is necessary for combustion reaction. We can prevent combustion reactions by cutting down the supply of oxygen to the combustible material as without oxygen combustion reaction will not take place.

Note: Combustion reactions are very important kinds of chemical reactions. These reactions have an important impact on our daily life. When oxygen and fuel react, heat or fire and light are produced. Combustion of fossil fuels generates heat and this heat is used in operation of machines such as engines, boilers etc.