Isomers are molecules that have the same chemical formula but different arrangements of atoms, as shown here for two isomers of pentane, C₅H₁₂.
(a) Do you expect a significant difference in the enthalpy of combustion of the two isomers? Explain.

Key Concepts

Isomerism

Isomerism refers to the phenomenon where two or more compounds have the same molecular formula but differ in the arrangement of atoms. This can lead to variations in physical and chemical properties, including boiling points, melting points, and reactivity. In the case of pentane, the two isomers, n-pentane and isopentane, illustrate how structural differences can influence the behavior of molecules.

Enthalpy of Combustion

The enthalpy of combustion is the heat released when one mole of a substance is completely burned in oxygen. It is a crucial measure in thermodynamics, reflecting the energy content of fuels. Different isomers can have varying enthalpies of combustion due to differences in their molecular structure, which affects the stability of the reactants and products formed during combustion.

Thermodynamic Stability

Thermodynamic stability refers to the relative energy levels of different molecular structures. More stable isomers typically have lower enthalpy values, meaning they release less energy upon combustion. The stability of isomers can influence their enthalpy of combustion, as less stable isomers may release more energy when they undergo combustion due to the greater energy difference between reactants and products.