What is the percentage of carbon in the product ' X ' formed in the given reaction?

• A

  85.6
• B

  80.6
• Correct answer
  C

  90.6
• D

  70.6

Solution

It is friedel craft alkylation of benzene.
Mass of C in product $(\mathrm{X})$ $=8$ atoms $\times 12.01 \mathrm{~g} / \mathrm{mol}=96.08$ Mass of Hydrogen (H) $=10$ atoms $\times 1.00=10 \mathrm{~g} / \mathrm{mol}$. Total mass $=96.08+10=106.08 \mathrm{~g} / \mathrm{mol}$ Percentage of carbon $\begin{aligned} & =\frac{\text { Mass of carbon }}{\text { Mass of ethylbenzene }} \times 100 \\ & =\frac{96.08}{106.08} \times 100=90.53 \% \approx 90.6 \% \end{aligned}$

Hence, the correct answer is option: 'C'.