Question

The reaction of 122 g of benzaldehyde with 108 g of phenylhydrazine gave 157 g of the product

The yield of the product is _________%. (round off to the nearest integer)

Answer 1

Correct Answer: 80

To calculate the yield of the product, we need to follow these steps:

1. Determine the theoretical mass of the product based on the limiting reagent.
2. Calculate the percentage yield using the actual and theoretical masses.

Step 1: Find the limiting reagent

The molar mass of benzaldehyde (C₇H₆O) is approximately 106 g/mol, and for phenylhydrazine (C₆H₅NHNH₂), it is approximately 108 g/mol.

Moles of benzaldehyde = ¹²²/₁₀₆ ≈ 1.15 mol
Moles of phenylhydrazine = ¹⁰⁸/₁₀₈ = 1.00 mol

Benzaldehyde is the excess reagent; phenylhydrazine is the limiting reagent.

Step 2: Calculate the theoretical yield

In the reaction, the molar ratio is 1:1. Thus, theoretical moles of product = moles of phenylhydrazine = 1.00 mol.

Molar mass of the product, C₁₃H₁₂N₂ = 196 g/mol

Theoretical mass of the product = 1.00 mol × 196 g/mol = 196 g

Step 3: Calculate the percentage yield

Actual mass of product = 157 g

Percentage yield = (^Actual/_Theoretical) × 100 = (¹⁵⁷/₁₉₆) × 100 ≈ 80.10%

Rounded to the nearest integer, the yield of the product is 80%