Kjeldahl’s method was used for the estimation of nitrogen in an organic compound. The ammonia evolve — Practical Organic Chemistry and Purification Chemistry Question
Question
Kjeldahl’s method was used for the estimation of nitrogen in an organic compound. The ammonia evolved from 0.55 g of the compound neutralised 12.5 mL of 1 M H SO solution. The percentage of nitrogen in the compound is_____. (Nearest integer) 2 4
💡 Solution & Explanation
**Step 1: Determine moles of H₂SO₄ used** Moles of H₂SO₄ = Molarity × Volume (L) = 1 M × 0.0125 L = 0.0125 mol **Step 2: Find moles of NH₃ neutralized** The neutralization reaction is: 2NH₃ + H₂SO₄ → (NH₄)₂SO₄ From stoichiometry: 1 mol H₂SO₄ neutralizes 2 mol NH₃ Moles of NH₃ = 2 × 0.0125 = 0.025 mol **Step 3: Calculate moles of nitrogen** Since each NH₃ molecule contains 1 nitrogen atom: Moles of N = 0.025 mol **Step 4: Convert moles of N to mass** Atomic mass of N = 14 g/mol Mass of N = 0.025 mol × 14 g/mol = 0.35 g **Step 5: Calculate percentage of nitrogen** Percentage of N = (Mass of N / Mass of compound) × 100 = (0.35 / 0.55) × 100 = 63.64% ≈ 64% Therefore, the answer is 64.00.