Tag: petroleum and natural gas

Octane number expresses the knocking characteristics of petrol. n-heptane (a constituent of petrol) knocks very badly, so its anti-knock value has been given zero. On the other hand, iso-octane (also a constituent of petrol) gives very little knocking, so its anti-knock value has been given 100
The higher the octane number, the more compression the fuel can withstand before detonating (igniting) i.e fuels with a higher octane rating are used in high-performance gasoline engines that require higher compression ratios and with lower octane numbers are ideal for diesel engines,as diesel engines do not compress the fuel, but rather compress only air and then inject fuel into the air which was heated by compression.

A motor fuel is said to have an octane number of 80 when it is as good as a mixture of 20% n-heptane and 80% of iso-octane.
The octane number of gasoline is defined as the percentage of iso-octane present in a mixture of iso-octane and n-heptane, when the mixture has the same knocking in the engine, as the gasoline under examination.

The octane number of gasoline is defined as the percentage of iso-octane present in a mixture of iso-octane and n-heptane, when the mixture has the same knocking in the engine, as the gasoline under examination.

The hydrocarbon iso-octane which has good resistance to knocking even in highest compression motors is arbitrarily given an octane number of 100. Whereas n-heptane which knocks the maximum is arbitrarily given the value of 0.

Cetane number is the percentage of cetane (hexa-decane) in a given diesel sample.

Ferric oxide is used as a catalyst in the manufacture of synthetic petrol by Bergius method.

Octane number can be increased by any of the following methods:
(1) Increasing the percentage of branched or cycloalkanes.
(2) By addition of BTX or TEL.
(3) By addition of powder alcohol (ethanol).

Octane number is the percentage by volume of iso-octane present in a mixture of iso-octane and heptane which has the same knocking performance as the sample fuel. For eg - octane number of triptane is 125. Hence, the answer is D.

Cyclic alkanes have relatively higher value of octane number.

Aviation gasoline has octane number of 100 or more. Aviation gasoline is the fuel used in aeroplanes. Use of gasoline with lower octane number may lead to the problem of engine knocking.