Question

0.2 g of an organic compound was subjected to estimation of nitrogen by Duma’s method in which volume of N2 evolved (at STP) was found to be 22.400 mL. The percentage of nitrogen in the compound is _____. [nearest integer] 
(Given : Molar mass of N₂ is 28 g mol^–1, Molar volume of N₂ at STP : 22.4L)

Answer 1

Correct Answer: 14

The problem involves calculating the percentage of nitrogen in an organic compound using data derived from Duma's method. To solve this, follow these steps:

1. **Determine Moles of N₂ Evolved**:
Using the given volume of N₂ (22.400 mL or 0.0224 L at STP), and the known molar volume of N₂ at STP (22.4 L/mol), the moles of N₂ can be calculated as follows:

n = Volume of N₂ / Molar volume of N₂ at STP
n = 0.0224 L / 22.4 L/mol = 0.001 mol

2. **Calculate Mass of Nitrogen in N₂**:
Moles of N₂ can be converted to mass. Since each molecule of N₂ contains two nitrogen atoms, the molar mass of N₂ is 28 g/mol. Thus:

Mass of N₂ = Moles of N₂ × Molar mass of N₂
Mass of N₂ = 0.001 mol × 28 g/mol = 0.028 g

3. **Calculate Percentage of Nitrogen in the Compound**:
The percentage of nitrogen in the organic compound is calculated by dividing the mass of nitrogen by the mass of the compound and multiplying by 100:

Percentage of N = (Mass of N₂ / Mass of compound) × 100
Percentage of N = (0.028 g / 0.2 g) × 100 = 14%

The computed percentage of nitrogen is 14%, which falls within the given range of 14 to 14, confirming the accuracy of the solution.