Which of the following products is formed when n - heptane is passed over `(Al_2O_3+Cr_2O_3)` catalyst at 773K?

Options

A. Benzene
B. Toluene
C. Polyheptane
D. Cycloheptane

Answer

To determine the product formed when n-heptane is passed over an `(Al_2O_3 + Cr_2O_3)` catalyst at 773 K, we need to understand the process involved.

### Step-by-Step Solution:

1. **Identify the Reactants**: The reactant in this case is n-heptane, which has the molecular formula C7H16.

2. **Understand the Reaction Conditions**: The reaction occurs in the presence of a catalyst, specifically a combination of aluminum oxide (Al2O3) and chromium trioxide (Cr2O3), at a high temperature of 773 K.

3. **Recognize the Type of Reaction**: The reaction is classified as an aromatization reaction. Aromatization is a process where aliphatic hydrocarbons (like n-heptane) are converted into aromatic hydrocarbons (like benzene and its derivatives) under specific conditions.

4. **Determine the Product**:
- When n-heptane (C7H16) undergoes aromatization, it will lose hydrogen atoms and rearrange to form an aromatic compound.
- The primary aromatic product from n-heptane is toluene (C7H8), which is a methyl-substituted benzene. This occurs because the 6-carbon chain from n-heptane can form benzene, and the remaining methyl group (from the 7th carbon) will be attached to the benzene ring.

5. **Conclude the Result**: Therefore, the product formed when n-heptane is passed over the `(Al_2O_3 + Cr_2O_3)` catalyst at 773 K is **toluene**.

### Final Answer:
The product formed is **toluene**.

---