Question
When 1 g of compound ( X ) is subjected to Kjeldahl's method for estimation of nitrogen, 15 mL 1 M H _ 2 SO _ 4 was neutralized by ammonia evolved. The percentage of nitrogen in compound ( X ) is :
JEE Main
Chemistry
General Organic Chemistry
2026
JEE Main 2026 (22 January Shift 2)
JEE Main Chemistry Question (2026) — Solution
Options
- A. 0.21
- B. 21
- C. 42
- D. 0.42
Answer
C. 42
Step-by-step solution
In Kjeldahl's method, nitrogen in the compound is converted to NH₃. The ammonia is absorbed and reacts with H₂SO₄ according to: 2NH_3 + H_2SO_4 (NH_4)_2SO_4. Given that 15 mL of 1 M H₂SO₄ was neutralized: Moles of H₂SO₄ = 15 × 10⁻³ mol. From stoichiometry, 1 mol H₂SO₄ reacts with 2 mol NH₃. Therefore, moles of NH₃ = 2 × 15 × 10⁻³ = 0.030 mol. Since each NH₃ contains 1 nitrogen atom: Moles of N = 0.030 mol. Mass of N = 0.030 × 14 = 0.42 g. Percentage of N in compound = (0.42/1) × 100 = 42%.
Related: Chemistry — General Organic Chemistry · All PYQ Banks