Question

If salicylic acid ( $138 \text{ u}$ ) reacts with acetic anhydride ( $102 \text{ u}$ ) to from aspirin ( $180 \text{ u}$ ) calculate % atom economy.

• A. 25%
• B. 50%
• C. 65%
• D. 75%

Hint:

Atom economy is about "how much reactant mass was actually used?" Just divide product mass by total reactant mass.

Answer 1

The Correct Option is D

Step 1: Concept
% Atom Economy is calculated as: $\frac{\text{Formula Weight of Desired Product}}{\text{Total Formula Weight of all Reactants}} \times 100$.

Step 2: Meaning
It measures the efficiency of a chemical reaction in terms of atoms from reactants ending up in the product.

Step 3: Analysis
- Desired Product (Aspirin) Mass $= 180 \text{ u}$. - Total Reactant Mass $= 138 (\text{Salicylic acid}) + 102 (\text{Acetic anhydride}) = 240 \text{ u}$. - % Atom Economy $= (180 / 240) \times 100$.

Step 4: Conclusion
$(180 / 240) = 3/4 = 0.75$, so 75%. Final Answer: (D)