Question

rank the following compounds according to their heat of combustion. compound compound name heat of combustion 2 - methylheptane select 2 - methylhexane select nonane select octane select

Explanation:

Step1: Recall heat - of - combustion principle

The heat of combustion of hydrocarbons increases with the number of carbon atoms. For isomers, the more branched - out isomer has a lower heat of combustion due to greater stability.

Step2: Count carbon atoms

Nonane ($C_9H_{20}$) has 9 carbon atoms, octane ($C_8H_{18}$) has 8 carbon atoms, 2 - methylheptane ($C_8H_{18}$) has 8 carbon atoms, and 2 - methylhexane ($C_7H_{16}$) has 7 carbon atoms.

Step3: Compare isomers

Among octane and 2 - methylheptane (both with 8 carbon atoms), 2 - methylheptane is branched and more stable, so it has a lower heat of combustion than octane.

Answer:

Nonane > Octane > 2 - methylheptane > 2 - methylhexane