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asked in NEET by (48 points)

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The heat of formation or heat of combustion of an alkane depends on the number of C-C bonds and C-H bonds present in its molecule as well as on the overall distribution of charges (of nucleus and electron clouds) in the molecule. So these also depend on number C and H atoms. So  with increase of molar mass the heat of combustion or heat of formation will Increase.

So isomers of butane will have less heat of formation or heat of combustion than any isomer of pentane.

Again amongst the isomers of pentane the isomers with more branching will have less heat of formation or heat of combustion.As in more branching situation the molecular system is stabilised more in respect of distribution of charges.

So in our case the order of heat of combustion becomes

n-pentane>isopentane >neopentane> isobutane

Hence n-pentane will have maximum heat of combustion.

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