Question

The mass of benzanilide obtained from the benzoylation reaction of \(5.8 \, \text{g}\) of aniline, if yield of product is \(82%\), is ______________ g (nearest integer).
(Given molar mass in g mol\(^{-1}\): H : 1, C : 12, N : 14, O : 16)

Hint:

In yield-based problems, always calculate the theoretical yield first using stoichiometry, then multiply by percentage yield to obtain the actual product mass.

Answer 1

Correct Answer: 10

Step 1: Write the reaction stoichiometry.
Aniline reacts with benzoyl chloride to form benzanilide in a \(1:1\) molar ratio.

Step 2: Calculate molar mass of aniline.
Aniline: \( \mathrm{C_6H_5NH_2} = \mathrm{C_6H_7N} \)
\[ \text{Molar mass of aniline} = (6 \times 12) + (7 \times 1) + 14 = 93 \, \text{g mol}^{-1} \]
Step 3: Calculate number of moles of aniline.
\[ \text{Moles of aniline} = \frac{5.8}{93} \approx 0.062 \, \text{mol} \]
Step 4: Calculate molar mass of benzanilide.
Benzanilide: \( \mathrm{C_{13}H_{11}NO} \)
\[ \text{Molar mass} = (13 \times 12) + (11 \times 1) + 14 + 16 = 197 \, \text{g mol}^{-1} \]
Step 5: Calculate theoretical mass of benzanilide.
\[ \text{Theoretical mass} = 0.062 \times 197 \approx 12.2 \, \text{g} \]
Step 6: Apply percentage yield.
\[ \text{Actual mass} = \frac{82}{100} \times 12.2 \approx 10.0 \, \text{g} \]
Final Answer: \[ \boxed{10} \]