Question

What scale is used for measuring the quality of gasoline?

Answer 1

Gasoline is a derivative product of crude oil/petroleum. It is also known as petrol in some countries. It is derived from the fractional distillation process of crude oil and has a translucent liquid form. It can be found in various varieties and in this solution we will see how the quality of gasoline is measured.

Complete answer:
Gasoline is a derivative product of crude oil/petroleum. It is also known as petrol in some countries. It is derived from the fractional distillation process of crude oil and has a translucent liquid form.
So, now we need to understand the term “knocking”. In an internal combustion engine, knocking is defined as the noise caused due to the premature combustion of a compressed mixture of air and fuel.
Now, to measure the quality of gasoline, a scale has been set which is known as octane scale or octane number. Octane number is the measure of fuel’s ability to resist knocking during combustion.
This scale was proposed with two hydrocarbons: isooctane and n-heptane. Isooctane, we know that, it is a branched hydrocarbon and it burns smoothly with a little knocking so it is given the number $100$ on octane scale while n-heptane is a straight chain hydrocarbon and it produces a lot of knocking, so it is given a number $0$ on the octane scale.
Therefore, greater the octane number, better will be the quality of gasoline and vice versa.

Note:
On the basis of octane number, gasoline can be classified in three categories such as Regular (Antiknock index between $85 - 88$ ), Midgrade (Antiknock index between $88 - 90$ ) and Premium (Antiknock index greater than $90$ ). So, in this way we can measure the quality of gasoline on the basis of its octane number.