When a hydrocarbon A undergoes combustion in the presence of air, it requires 9.5 equivalents of oxygen and produces 3 equivalents of water. What is the molecular formula of A?

Options

A. `C_(9)H_(6)`
B. `C_(6)H_(6)`
C. `C_(8)H_(6)`
D. `C_(9)H_(9)`

Answer

To find the molecular formula of the hydrocarbon A, we will use the information provided about the combustion reaction.

### Step-by-Step Solution:

1. **Understand the Combustion Reaction**:
The general combustion reaction for a hydrocarbon (CnHm) can be written as:
\[ C_nH_m + \left( n + \frac{m}{4} \right) O_2 \rightarrow n CO_2 + \frac{m}{2} H_2O \]
Here, \(n\) is the number of carbon atoms and \(m\) is the number of hydrogen atoms in the hydrocarbon.

2. **Set Up the Equations**:
From the problem, we know:
- The amount of oxygen used is 9.5 equivalents:
\[ n + \frac{m}{4} = 9.5 \]
- The amount of water produced is 3 equivalents:
\[ \frac{m}{2} = 3 \]

3. **Solve for \(m\)**:
From the second equation, we can solve for \(m\):
\[ \frac{m}{2} = 3 \implies m = 6 \]

4. **Substitute \(m\) into the First Equation**:
Now substitute \(m = 6\) into the first equation:
\[ n + \frac{6}{4} = 9.5 \]
Simplifying this gives:
\[ n + 1.5 = 9.5 \implies n = 9.5 - 1.5 = 8 \]

5. **Determine the Molecular Formula**:
Now that we have \(n = 8\) and \(m = 6\), we can write the molecular formula of the hydrocarbon A:
\[ C_8H_6 \]

### Final Answer:
The molecular formula of hydrocarbon A is \(C_8H_6\).