Question

Consider the reaction:

Find the number of moles of benzene formed if the efficiency of reaction is 60%.

• A. 0.05
• B. 0.06
• C. 0.03
• D. 0.04

Answer 1

The Correct Option is C

Step 1: Write the reaction and identify the mole ratio.
Phenol reacts with zinc dust to form benzene. The balanced reaction shows that \(1\) mole of phenol produces \(1\) mole of benzene. Therefore, the mole ratio of phenol to benzene is \(1:1\).
Step 2: Calculate the moles of phenol given.
The molar mass of phenol \(\left(\text{C}_6\text{H}_5\text{OH}\right)\) is: \[ 6 \times 12 + 6 \times 1 + 16 = 72 + 6 + 16 = 94 \, \text{g mol}^{-1} \] Given mass of phenol \(= 4.7 \, \text{g}\) \[ \text{Moles of phenol} = \frac{4.7}{94} = 0.05 \, \text{mol} \] So, theoretical moles of benzene formed \(= 0.05\) mol.
Step 3: Apply the reaction efficiency.
The efficiency of the reaction is \(60%\). Hence, the actual moles of benzene formed will be: \[ \text{Actual moles of benzene} = \frac{60}{100} \times 0.05 \] \[ = 0.6 \times 0.05 = 0.03 \, \text{mol} \] Step 4: Compare with the given options.

• (A) 0.05: Incorrect. This is the theoretical yield, not the actual yield.
• (B) 0.06: Incorrect. This is greater than the theoretical yield.
• (C) 0.03: Correct. This is the actual yield at \(60%\) efficiency.
• (D) 0.04: Incorrect. This does not match the yield calculation.

Step 5: Conclusion.
Thus, the number of moles of benzene formed is \(0.03\) mol.
Final Answer:} 0.03 mol.