1. The total number of structural isomers possible for the substituted benzene derivatives with the molecular formula C₉ H₁₂ is

2. The total number of acyclic structural isomers possible for compound with molecular formula C₄H₁₀O is

3. The number of isomers for the compound with molecular formula  is C₂BrClFI

4. Total number of possible isomers (both structural as well as stereoisomers) of cyclic ethers of molecular formula  is :

The ether with 2 chiral carbons has a plane of symmetry in Cis-configuration. Therefore, it will have 3 stereo-isomers. Total isomers = 1+2+1+2+3+1=10