Question

1.86 g of aniline completely reacts to form acetanilide. 10% of the product is lost during purification. Amount of acetanilide obtained after purification (in g) is _________ × 10⁻².

Hint:

Acylation of amines is often used to "protect" the amino group or to reduce its activating power in aromatic substitution.

Answer 1

Correct Answer: 243

Step 1: Reaction: $C_6H_5NH_2 \xrightarrow{Ac_2O} C_6H_5NHCOCH_3$.
Step 2: Molar mass Aniline $= 93 \text{ g/mol}$; Molar mass Acetanilide $= 135 \text{ g/mol}$.
Step 3: Moles of Aniline $= \frac{1.86}{93} = 0.02 \text{ mol}$.
Step 4: Theoretical yield of Acetanilide $= 0.02 \times 135 = 2.70 \text{ g}$.
Step 5: 10% loss $\to$ 90% remains. $2.70 \times 0.90 = 2.43 \text{ g}$.
Step 6: $2.43 \text{ g} = 243 \times 10^{-2} \text{ g}$. Thus, answer is 243.