Two compounds are considered as isomers if they have
a) same molecular formula or same structure
b) different molecular formula and same structure
c) same molecular formula and same structure
d) different molecular formula and different structure

In chemistry, isomers are compounds that have the same molecular formula but may differ in structure. This is common in the orientation of sugars. The answer is not in the choices.

The correct one should be same molecular formula, different in chemical structure.

Answerδh > 0explanationc₆h₆  (s)  → c₆h₆ (l)if you are changing it from a solid to a liquid, you are pretty much melting the solid. this requires heat energy. therefore, the reaction is endothermic (takes in energy); the system enthalpy increases as the reaction proceeds: δh > 0.

Ithink the answer is b.