Question

What is the octane number of $n$ -Heptane?

Answer 1

Hint: $n$ -Heptane is the straight chain alkane with the chemical formula $C_7{H}_{16}$ and is one of the main components of gasoline. It is a lighter component in gasoline, burns more explosively, causing engine pre-ignition (knocking) in its pure form.

Complete answer:
Octane number also known as octane rating is a measurement of the quality or performance of gasoline. The higher the number, the better the fuel burns within the engine of the vehicle. Fuels with a higher octane rating are used in high performance gasoline engines while fuels with lower octane numbers are ideal for diesel engines.
The octane rating of a specific gasoline mixture is based on the ratio of two compounds in the gasoline- iso-octane, a compound with the same chemical formula as octane and normal heptane. The octane number of iso-octane is $100$ and n-heptane has octane number zero.
$n$ -heptane has zero octane number because of very poor knock resistance, whereas iso-octane exhibits excellent knock resistance, and is thus assigned a value of $100$. Octane isomers opposite to , $n$ -heptane which burns more slowly and give less knocking. It was originally chosen as a zero point of the scale because of the availability of very high purity $n$ -heptane, unmixed with other isomers of heptane or other alkane.
The higher the octane number, the more compression from the piston the gasoline can withstand before ignition in the engine. The ability for gasoline to withstand being compressed is most important for vehicles that run on traditional gasoline.

Note:
There are two different performance-based tests used to determine the octane number of a fuel. The motor octane number (MON) and the research octane number (RON) both represent how a gasoline product performs under specific test conditions. These performances then are compared with a mixture of varying ratios of standard reference fuels.