Question

1. one step in making para - aminobenzoic acid, paba, an ingredient in some suntan lotions, involves replacing one of the hydrogen atoms in a toluene molecule with an $-no_{2}$ group, directly opposite the $-ch_{3}$ group. calculate the percent yield if 550 g of toluene added to an excess of nitric acid provides 305 g of the nitrotoluene product.

Explanation:

Step1: Find molar mass of toluene

Toluene formula: $\text{C}_7\text{H}_8$. Molar mass = $7(12.01) + 8(1.008) = 92.14$ g/mol.

Step2: Calculate moles of toluene

Moles = $\frac{\text{mass}}{\text{molar mass}} = \frac{550\ \text{g}}{92.14\ \text{g/mol}} \approx 5.97\ \text{mol}$.

Step3: Find molar mass of nitrotoluene

Nitrotoluene (para): $\text{C}_7\text{H}_7\text{NO}_2$. Molar mass = $7(12.01) +7(1.008)+14.01+2(16.00)=137.14$ g/mol.

Step4: Calculate theoretical yield

Theoretical yield = $5.97\ \text{mol} \times 137.14\ \text{g/mol} \approx 819\ \text{g}$.

Step5: Compute percent yield

Percent yield = $\frac{\text{actual yield}}{\text{theoretical yield}} \times 100\% = \frac{305\ \text{g}}{819\ \text{g}} \times 100\% \approx 37.2\%$.

Answer:

37.2%