Final answer:
The octane number of gasoline is a measure of its ability to burn without knocking or pinging. It is determined by comparing observed knocking to specific mixtures of two pure compounds: n-heptane and isooctane.
Step-by-step explanation:
The octane number of gasoline is a measure of its ability to burn in a combustion engine without knocking or pinging, which are indications of premature combustion. The octane scale was established using two pure compounds: n-heptane and isooctane. n-Heptane, which causes knocking, has an octane rating of 0, whereas isooctane, a smooth-burning fuel, has an octane rating of 100.
Chemists assign octane ratings to different blends of gasoline by comparing the observed knocking to specific mixtures of n-heptane and isooctane. For example, a blend of 89% isooctane and 11% n-heptane has an octane rating of 89, and gasoline with similar performance is assigned an octane rating of 89.
Gasoline with higher octane ratings burns more smoothly in an engine and is less likely to cause knocking or pinging. Regular gasoline typically has an octane rating of 87, while premium gasoline has a rating of 93 or higher.