Final answer:
Compounds with identical molecular structures are most likely the same, as they share the same arrangement of atoms and properties. Isomers, however, which also have the same molecular weight, can exhibit different characteristics due to their varied structures and polarities.
Step-by-step explanation:
The question asks which of the following compounds are most likely to be the same:
- (a) Compounds with identical molecular structures
- (b) Compounds with similar boiling points
- (c) Compounds with different molecular weights
- (d) Compounds with contrasting chemical compositions
The correct answer is (a) Compounds with identical molecular structures. These compounds are most likely the same because they have the same arrangement of atoms and the same physical and chemical properties. Isomers are examples of compounds that have the same molecular formula but different structural formulas and properties. Despite having the same molar mass, isomers can have different boiling points due to differences in polarity and strength of intermolecular forces such as dipole-dipole interactions. Because of these differences, compounds with similar boiling points or the same molecular weight are not necessarily the same compound.