9 public questions tagged with this topic.
Kjeldahl’s method involves heating the compound with H₂SO₄ to form (NH₄)₂SO₄, followed by ammonia liberation and titration.
Ref: NCERT Class 11 Chemistry > Chapter 8: Organic Chemistry - Some Basic Principles and Techniques > Topic: Qualitative and Quantitative Analysis - Lassaigne Test and Estimation
Kjeldahl’s method fails for nitro compounds (-NO₂) as nitrogen is not easily converted to NH₃; Dumas method is preferred.
Ref: NCERT Class 11 Chemistry > Chapter 8: Organic Chemistry - Some Basic Principles and Techniques > Topic: Qualitative and Quantitative Analysis - Lassaigne Test and Estimation
Mass of N = (28/22400) × 112 = 0.14 g. Percentage = (0.14/0.5) × 100 = 28%.
Ref: NCERT Class 11 Chemistry > Chapter 8: Organic Chemistry - Some Basic Principles and Techniques > Topic: Qualitative and Quantitative Analysis - Lassaigne Test and Estimation
Volume of N₂ at STP = 60 mL. Mass of N = (28/22400) × 60 = 0.075 g. Percentage = (0.075/0.4) × 100 = 18.75%.
Ref: NCERT Class 11 Chemistry > Chapter 8: Organic Chemistry - Some Basic Principles and Techniques > Topic: Qualitative and Quantitative Analysis - Lassaigne Test and Estimation
The Dumas method involves heating the compound to release nitrogen gas (N₂), which is collected and measured at STP.
Ref: NCERT Class 11 Chemistry > Chapter 8: Organic Chemistry - Some Basic Principles and Techniques > Topic: Qualitative and Quantitative Analysis - Lassaigne Test and Estimation
Mass of N = (28/22400) × 50 = 0.0625 g. Percentage = (0.0625/0.25) × 100 = 25%.
Ref: NCERT Class 11 Chemistry > Chapter 8: Organic Chemistry - Some Basic Principles and Techniques > Topic: Qualitative and Quantitative Analysis - Lassaigne Test and Estimation
Mass of N = (28/22400) × 80 = 0.1 g. Percentage = (0.1/0.32) × 100 = 31.25% ≈ 31%.
Ref: NCERT Class 11 Chemistry > Chapter 8: Organic Chemistry - Some Basic Principles and Techniques > Topic: Qualitative and Quantitative Analysis - Lassaigne Test and Estimation
Mass of N = (28/22400) × 90 = 0.1125 g. Percentage = (0.1125/0.35) × 100 = 32.14% ≈ 32%. Carius data is for bromine, not relevant here.
Ref: NCERT Class 11 Chemistry > Chapter 8: Organic Chemistry - Some Basic Principles and Techniques > Topic: Qualitative and Quantitative Analysis - Lassaigne Test and Estimation
Moles of H₂SO₄ = 0.02 × 0.1 = 0.002. Moles of NH₃ = 0.004 (2H per H₂SO₄). Mass of N = 0.004 × 14 = 0.056 g. Percentage = (0.056/0.5) × 100 = 11.2%.
Ref: NCERT Class 11 Chemistry > Chapter 8: Organic Chemistry - Some Basic Principles and Techniques > Topic: Isomerism - Structural Isomerism - Chain Position Functional Metamerism
