Question

Which of the following is produced by incomplete combustion of gasoline?
A) \[\text{N}{{\text{O}}_{\text{2}}}\]
B) \[\text{CO}\]
C) \[\text{C}{{\text{O}}_{\text{2}}}\]
D) \[\text{S}{{\text{O}}_{\text{2}}}\]

Answer 1

Hint: Gasoline or the fuel are hydrocarbon compounds with the general formula${{\text{C}}_{\text{x}}}{{\text{H}}_{\text{y}}}$. The gasoline undergoes the combustion reaction in presence of oxygen. The insufficient supply of oxygen causes incomplete combustion of fuel. It generates pure carbon also called soot and carbon monoxide.

Complete answer:
Gasoline is hydrocarbons. They are made of carbon and hydrogen atoms. During the combustion reaction, the carbon from the gasoline combines with the oxygen from the air and produces the carbon dioxide $\text{(C}{{\text{O}}_{\text{2}}}\text{)}$ . The additional weight to the compounds comes from the oxygen.
In gasoline, the carbon $\text{(C)}$atoms are bonded to the hydrogens to form hydrocarbon molecules. The general formula for the gasoline is${{\text{C}}_{\text{x}}}{{\text{H}}_{\text{y}}}$. Here stands for the total number of carbon in the chain and y for the hydrogen-bonded to the carbons.
We know that the air is primarily composed of nitrogen $\text{(N)}$ and oxygen $\text{(}{{\text{O}}_{\text{2}}}\text{)}$ .
When the hydrocarbons are exposed to the oxygen in the air the hydrocarbons undergo the combustion. The reaction of the combustion of the fuel is expressed as follows:
\[\text{Hydrocarbon + oxygen }\to \text{ carbon dioxide + water}\]
Let’s consider a complete combustion of methane.
$\text{C}{{\text{H}}_{4}}\text{+ 2}{{\text{O}}_{\text{2}}}\text{+ spark}\to \text{C}{{\text{O}}_{\text{2}}}\text{+ 2}{{\text{H}}_{\text{2}}}\text{O + Heat}$
In this combustion reaction, we observe that the hydrogen from the gasoline combines with the oxygen from the air and produces the water molecule. Similarly, the carbon from the fuel combines with oxygen from the air to produce carbon dioxide. Along with the water molecules and the carbon dioxide the heat is produced. This is called the complete combustion of gasoline. The complete combustion is characterized by the blue coloured flame.
This heat energy is used as mechanical energy to propel the vehicles.
However, in a poor supply of air or oxygen, the fuel undergoes incomplete combustion. It produces the water but carbon reacts incompletely with the oxygen and forms the carbon monoxide $\text{(CO)}$ instead of$\text{C}{{\text{O}}_{\text{2}}}$.
\[\text{Hydrocarbon + oxygen (Insufficient) }\to \text{ carbon monoxide + carbon + water}\]
The carbon release is pure carbon which is a black substance called soot. The carbon monoxide formed is a poisonous gas. This is why the complete combustion of gasoline of hydrocarbons is preferred over incomplete combustion.
Let's consider an example of incomplete combustion of methane:
\[\text{4C}{{\text{H}}_{\text{4}}}\text{ + 5}{{\text{O}}_{\text{2}}}\to \text{2CO + 8}{{\text{H}}_{\text{2}}}\text{O + 2C}\]
The incomplete combustion is often unwanted as it releases less energy than the complete combustion. The soot is messy and can build up in the equipment i.e. chimneys. The incomplete combustion of fuel is characterized by the orange flame.
Here, we can conclude that the incomplete combustion of gasoline produces carbon monoxide$\text{(CO)}$.

Hence, (C) is the correct option.

Note:
In insufficient supply of air hydrocarbon lack oxygen and thus the carbon remains unreacted.in the incomplete combustion the product which is unburnt and contaminates the smoke in diesel or petrol engines. These partially oxidised compounds are of concern.