Question

4.7 g of phenol is heated with Zn to give product X. If this reaction goes to 60% completion then the number of moles of compound X formed will be ________ $\times 10^{-2}$. (Nearest Integer)
(Given molar mass in $\text{g mol}^{-1}$ : H:1, C:12, O:16)

Hint:

Reduction of phenol with Zn dust gives benzene. Calculate moles of phenol first, then apply the 60% yield factor.

Answer 1

Correct Answer: 3

This question involves the reduction of phenol using zinc dust. When phenol ($C_6H_5OH$) is heated with zinc, it undergoes reduction to form benzene ($C_6H_6$) and zinc oxide ($ZnO$).

Step 1: Write the balanced chemical equation.
$$C_6H_5OH + Zn \xrightarrow{\Delta} C_6H_6 + ZnO$$
From the stoichiometry, 1 mole of phenol produces 1 mole of benzene (product X).

Step 2: Calculate the molar mass of phenol ($C_6H_5OH$).
Molar mass $= (6 \times 12) + (6 \times 1) + (1 \times 16) = 72 + 6 + 16 = 94\text{ g mol}^{-1}$

Step 3: Calculate the initial moles of phenol.
$$\text{Moles of phenol} = \frac{\text{Given mass}}{\text{Molar mass}} = \frac{4.7\text{ g}}{94\text{ g mol}^{-1}} = 0.05\text{ moles}$$

Step 4: Calculate the actual moles of product X formed.
Since the reaction goes to 60% completion:
$$\text{Moles of product X} = 0.05 \times \frac{60}{100} = 0.03\text{ moles}$$

Step 5: Express the answer in the requested format ($n \times 10^{-2}$).
$$0.03 = 3 \times 10^{-2}$$
The value of $n$ is $3$.