The number of sp2 hybrid orbitals in a molecule of benzene is:

Step 1: Structure of Benzene

Benzene ($\ce{C6H6}$): 6 carbon atoms, all $\text{sp}^2$ hybridized, each with 1 H.

Step 2: Count sp2 Orbitals per Carbon

Each $\text{sp}^2$ carbon has 3 $\text{sp}^2$ orbitals:

• 2 form sigma bonds with adjacent carbons (C-C)
• 1 forms sigma bond with H (C-H)

So each carbon contributes 3 $\text{sp}^2$ orbitals. Step 3: Total sp2 Orbitals

$6\,\text{carbons} \times 3\,\text{sp}^2\,\text{orbitals/carbon} = 18\,\text{sp}^2\,\text{orbitals}$

Note: H atoms do NOT have $\text{sp}^2$ orbitals (they are 1s).

Answer = 18 (option b)