Question

Incomplete combustion of petrol or diesel in automobile engine produces:
A. $\text{CO and }{{\text{H}}_{2}}\text{O}$ vapours
B. $\text{CO and N}{{\text{O}}_{2}}$
C. $\text{CO}$
D. $\text{S}{{\text{O}}_{2}}$

Answer 1

Hint: Petrol or diesel is the long chain of hydrocarbons only, composed of carbon and hydrogen. Combustion is a high-temperature process and an exothermic redox reaction between fuels and oxidants like atmospheric oxygen that produces gaseous products or smoke.

Complete answer:
Let us first know what incomplete combustion is; by writing the differences between incomplete combustion and complete combustion:

COMPLETE COMBUSTION	INCOMPLETE COMBUSTION
Involves complete oxidation of fuels.	Involves incomplete or partial oxidation of fuels.
Occurs when there is enough oxygen is present.	Occurs when there isn’t enough oxygen is present.
Produces a large amount of energy.	Produces low amounts of energy.
Burns with a blue coloured flame.	Burns with a yellow coloured flame.
Produces carbon dioxide and water as major as products.	Produces carbon monoxide, carbon dust and water as major as products.

The chemical formula of petrol is ${{\text{C}}_{8}}{{\text{H}}_{18}}$. In fact, it is a source of petroleum. In complete combustion, the reactant or hydrocarbon reacts with oxygen; the products formed are carbon dioxide and water. The reaction of petrol with oxygen under complete combustion is $\text{2}{{\text{C}}_{8}}{{\text{H}}_{18}}\left( \text{l} \right)+25{{\text{O}}_{2}}\left( \text{g} \right)\to 16\text{C}{{\text{O}}_{2}}\left( \text{g} \right)+18{{\text{H}}_{2}}\text{O}\left( \text{g} \right)$.
When hydrocarbon reacts with less amount of oxygen, the products formed are carbon monoxide and water. The reaction of petrol with oxygen (incomplete combustion) is $\text{2}{{\text{C}}_{8}}{{\text{H}}_{18}}\left( \text{l} \right)+17{{\text{O}}_{2}}\left( \text{g} \right)\to 16\text{CO}\left( \text{g} \right)+18{{\text{H}}_{2}}\text{O}\left( \text{g} \right)$.

The correct answer to this question is option ‘a’; the products formed when incomplete combustion of petrol occurs are $\text{CO and }{{\text{H}}_{2}}\text{O}$ vapours.

Note:
Carbon monoxide is an inhibitor to oxygen. Carbon monoxide is 250 times more likely to bind to the heme group of haemoglobin than oxygen which is due to higher affinity of carbon monoxide. When haemoglobin will be able to release the oxygen to the tissues, this can lead to suffocation or carbon monoxide poisoning. It is a result of carbon monoxide molecules binding to the heme group and preventing other oxygen molecules from binding. This also decreases the oxygen-carrying capacity of the haemoglobin.