Question

Multiple Choice ( Select 1 out of 4 options, for the question below.)Arrange n-heptane, isooctane and naphthalene in increasing order of their knocking tendencyOptionsNaphthalene < iso-octane < n-heptaneIsooctane < n-heptane < naphthaleneOOOn-heptane <naphthalene <iso-octaneO Naphthalene <n-heptane < isooctane​

Answer 1

Answer:

Fuels are the materials that, either on combustion with oxygen or by nuclear reaction (fission or fusion), release useful heat energy which can be harnessed for usage in various fields. A good fuel must have moderate ignition temperature and high calorific value.

Knocking refers to rattle like sound which is produced in an internal combustion engine when the fuel-air mixture gets ignited incompletely and unburnt particles are left.

Answer 2

Answer: Naphthalene < Isooctane​< n-heptane

Explanation:

Knocking : The metallic sound that is made during working of an internal combustion engine is known as knocking.

“The greater is the compression greater will be the efficiency of engine.” Fuel that has less knocking property is preferred always.

The knocking tendency follows the given order : Straight chain alkanes > branched chain alkanes > olefins > Cyclo-alkanes > aromatic hydrocarbons.

Naphthalene is an aromatic hydrocarbon, isooctane is branched chain alkane and n-heptane is straight chain hydrocarbon.

Therefore the increasing order of knocking tendency for the given options is:

Naphthalene < Isooctane​< n-heptane

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