JEE Main - Qualitative detection of N S P and halogens in organic compounds Online Test (MCQ Quiz)

1. Which method is commonly used for the qualitative detection of nitrogen in organic compounds?

A) Liebig's method B) Dumas' method C) Kjeldahl's method D) Beilstein test

2. In the Lassaigne's test for nitrogen, sodium metal is fused with the organic compound in a fusion tube. What is the primary purpose of this fusion?

A) To decompose the organic compound completely B) To convert nitrogen into sodium cyanide C) To oxidize sulfur present in the compound D) To precipitate halogens as silver halides

3. When an organic compound containing nitrogen is fused with sodium metal, and the resulting mass is extracted with water, sodium cyanide is formed. This extract is then treated with ferrous sulfate. What is the colored precipitate formed if nitrogen is present?

A) Yellow precipitate of sodium ferrocyanide B) White precipitate of iron(II) hydroxide C) Blue precipitate of Prussian blue D) Green precipitate of iron(II) hexacyanoferrate(III)

4. Which reagent is used to detect the presence of cyanide ions in the Lassaigne's extract when testing for nitrogen?

A) Ferrous sulfate B) Ferric chloride C) Silver nitrate D) Sodium hydroxide

5. If the Lassaigne's extract, after treatment with ferrous sulfate and acidification with HCl, gives a green precipitate turning blue on standing, it indicates the presence of:

A) Sulfur B) Nitrogen C) Halogens D) Phosphorus

6. Which of the following is NOT a characteristic observation for the Lassaigne's test for nitrogen?

A) Formation of Prussian blue B) A pale green solution C) Precipitation with ferrous sulfate D) Acidification with HCl

7. In the Lassaigne's test, if the organic compound contains both nitrogen and sulfur, what is formed upon fusion with sodium metal?

A) Sodium cyanide and sodium sulfide B) Sodium thiocyanate C) Sodium sulfate and sodium nitride D) Sodium carbonate and sodium sulfite

8. When testing for nitrogen using the Lassaigne's method, if the organic compound contains both nitrogen and sulfur, the addition of ferrous sulfate may lead to the formation of:

A) Prussian blue only B) Black precipitate of iron(II) sulfide C) Both Prussian blue and iron(II) sulfide D) No precipitate

9. To distinguish between the presence of nitrogen and sulfur in the Lassaigne's test when both are present, which reagent is added to the sodium fusion extract?

A) Ferrous sulfate B) Sodium nitroprusside C) Silver nitrate D) Lead acetate

10. A violet color with sodium nitroprusside in the Lassaigne's test for a compound containing both N and S indicates the presence of:

A) Nitrogen B) Sulfur C) Both Nitrogen and Sulfur D) Neither Nitrogen nor Sulfur

11. Which method is generally employed for the qualitative detection of sulfur in organic compounds?

A) Dumas' method B) Kjeldahl's method C) Sodium fusion test (Lassaigne's test) D) Beilstein test

12. In the Lassaigne's test for sulfur, the organic compound is fused with sodium metal. The resulting mass is extracted with water, forming sodium sulfide. What is the next step to detect sulfur?

A) Add ferrous sulfate solution B) Add silver nitrate solution C) Acidify with acetic acid and add sodium nitroprusside D) Add lead acetate solution

13. When sodium sulfide from the Lassaigne's extract is treated with lead acetate solution, what is the observation if sulfur is present?

A) Yellow precipitate of lead(II) sulfide B) White precipitate of lead(II) sulfate C) Black precipitate of lead(II) sulfide D) No precipitate

14. Which of the following is a characteristic observation for the detection of sulfur using the Lassaigne's test?

A) Formation of Prussian blue B) Black precipitate with lead acetate C) Red precipitate with Fehling's solution D) White precipitate with silver nitrate

15. If an organic compound contains sulfur and is subjected to the Lassaigne's test, and the sodium fusion extract is acidified with acetic acid and then treated with sodium nitroprusside, a violet color indicates the presence of:

A) Nitrogen B) Sulfur C) Halogens D) Phosphorus

16. Which reagent is used to detect sulfide ions formed in the Lassaigne's test for sulfur?

A) Ferrous sulfate B) Lead acetate C) Silver nitrate D) Sodium nitroprusside

17. The detection of phosphorus in organic compounds typically involves its oxidation to phosphate. Which method is commonly used for this purpose?

A) Dumas' method B) Kjeldahl's method C) Sodium fusion followed by oxidation D) Beilstein test

18. In the detection of phosphorus, the organic compound is fused with sodium carbonate and an oxidizing agent like sodium nitrate. What is the resulting inorganic product containing phosphorus?

A) Sodium phosphide B) Sodium phosphate C) Sodium phosphite D) Sodium hypophosphite

19. After fusing the organic compound with sodium carbonate and sodium nitrate for phosphorus detection, the fused mass is extracted with water. The aqueous extract is then acidified and treated with ammonium molybdate in the presence of nitric acid. What is the characteristic observation for phosphorus?

A) Yellow precipitate of ammonium phosphomolybdate B) Green precipitate C) Blue color D) White precipitate

20. Which reagent is used to detect the presence of phosphate ions in the qualitative analysis of phosphorus in organic compounds?

A) Silver nitrate B) Ammonium molybdate C) Lead acetate D) Ferrous sulfate

21. The yellow precipitate formed with ammonium molybdate in the test for phosphorus is chemically known as:

A) Ammonium phosphite B) Ammonium phosphate C) Ammonium phosphomolybdate D) Ammonium molybdate

22. If the organic compound contains phosphorus and halogens, the phosphorus test might be affected. To avoid interference from halogens, which acid is typically used to acidify the aqueous extract before adding ammonium molybdate?

A) Hydrochloric acid B) Sulfuric acid C) Nitric acid D) Acetic acid

23. Which of the following elements cannot be detected using the Lassaigne's test?

A) Nitrogen B) Sulfur C) Halogens D) Phosphorus

24. The qualitative detection of halogens in organic compounds is most commonly done using which test?

A) Dumas' method B) Kjeldahl's method C) Beilstein test D) Sodium fusion test (Lassaigne's test)

25. In the Lassaigne's test for halogens, the organic compound is fused with sodium metal. The resulting mass is extracted with water, forming sodium halide. This extract is then acidified with dilute nitric acid. What is the next step to detect halogens?

A) Add ferrous sulfate solution B) Add silver nitrate solution C) Add lead acetate solution D) Add sodium nitroprusside solution

26. When silver nitrate solution is added to the sodium fusion extract (acidified with nitric acid) for halogen detection, a precipitate is formed. The color of the precipitate indicates the presence of:

A) Nitrogen B) Sulfur C) Halogen D) Phosphorus

27. A white precipitate, insoluble in dilute nitric acid but soluble in ammonium hydroxide, is formed when testing for halogens. This indicates the presence of:

A) Chlorine B) Bromine C) Iodine D) Fluorine

28. If the precipitate formed with silver nitrate in the Lassaigne's test for halogens is pale yellow and soluble in ammonium hydroxide, it indicates the presence of:

A) Chlorine B) Bromine C) Iodine D) Fluorine

29. A yellow precipitate, insoluble in ammonium hydroxide, is formed when testing for halogens using the Lassaigne's test. This indicates the presence of:

A) Chlorine B) Bromine C) Iodine D) Fluorine

30. Which of the following precipitates formed with silver nitrate in the Lassaigne's test for halogens is insoluble in ammonium hydroxide?

A) Silver chloride B) Silver bromide C) Silver iodide D) Silver fluoride

31. The Beilstein test is a qualitative test for halogens. It involves heating the organic compound with copper powder. A green or blue flame indicates the presence of:

A) Nitrogen B) Sulfur C) Halogens D) Phosphorus

32. Which of the following is a limitation of the Beilstein test for halogens?

A) It is highly specific for all halogens. B) It gives a positive test for some non-halogen compounds. C) It requires fusion with sodium metal. D) It is used for quantitative analysis.

33. In the Lassaigne's test for halogens, why is the sodium fusion extract acidified with nitric acid before adding silver nitrate?

A) To precipitate any sulfide ions present B) To prevent the precipitation of other silver salts like silver carbonate C) To oxidize the halide ions D) To detect nitrogen simultaneously

34. If an organic compound contains both chlorine and bromine, and is subjected to the Lassaigne's test for halogens, what would be observed upon addition of silver nitrate?

A) A white precipitate B) A pale yellow precipitate C) A yellow precipitate D) A mixture of white and pale yellow precipitates

35. Which of the following statements is true regarding the detection of halogens using silver nitrate after sodium fusion?

A) Silver fluoride is soluble in ammonium hydroxide. B) Silver chloride is soluble in ammonium hydroxide. C) Silver bromide is insoluble in ammonium hydroxide. D) Silver iodide is soluble in ammonium hydroxide.

36. When testing for phosphorus, if the organic compound contains halogens, the presence of halogens can interfere by forming precipitates with ammonium molybdate. What precaution is taken to avoid this interference?

A) Use hydrochloric acid for acidification B) Use sulfuric acid for acidification C) Ensure complete oxidation of phosphorus D) Fuse with sodium carbonate only, not sodium nitrate

37. In the Lassaigne's test, if the organic compound contains nitrogen and the resulting sodium fusion extract is incorrectly acidified with sulfuric acid before adding ferrous sulfate, what might be the consequence?

A) The test for nitrogen will be more sensitive. B) Sulfuric acid might react with ferrous sulfate, leading to erroneous results. C) Prussian blue formation will be enhanced. D) No significant interference will occur.

38. Which element's detection involves the formation of a colored complex with iron(III) chloride after oxidation?

A) Nitrogen B) Sulfur C) Phosphorus D) Halogens

39. The detection of phosphorus can also be carried out by heating the organic compound with concentrated sulfuric acid and potassium permanganate. This process oxidizes phosphorus to:

A) Phosphine B) Phosphorous acid C) Phosphoric acid D) Elemental phosphorus

40. After oxidation of phosphorus to phosphoric acid, it can be detected by adding ammonium molybdate and observing the formation of a yellow precipitate. This is similar to the step in which other detection method?

A) Nitrogen detection B) Sulfur detection C) Halogen detection D) Lassaigne's test for phosphorus

41. Which of the following pairs of elements and their characteristic Lassaigne's test observations is INCORRECT?

A) Nitrogen: Formation of Prussian blue B) Sulfur: Black precipitate with lead acetate C) Halogens: White precipitate with silver nitrate (for Chlorine) D) Phosphorus: Yellow precipitate with sodium cobalt nitrite

42. If an organic compound contains only sulfur, the Lassaigne's test would yield sodium sulfide. Upon acidification with acetic acid and addition of lead acetate, a black precipitate of ____ is formed.

A) Lead(II) sulfate B) Lead(II) sulfite C) Lead(II) sulfide D) Lead(II) thiosulfate

43. In the detection of nitrogen, the initial reaction of sodium cyanide with ferrous sulfate forms sodium ferrocyanide. Further addition of ferric chloride and acidification leads to the formation of Prussian blue. What is the chemical formula of Prussian blue?

A) Fe4[Fe(CN)6]3 B) Fe3[Fe(CN)6]2 C) Na4[Fe(CN)6] D) Fe(CN)2

44. Which of the following elements can be detected using a simple flame test with copper wire (Beilstein test)?

A) Nitrogen B) Sulfur C) Halogens D) Phosphorus

45. The qualitative detection of phosphorus often involves converting it to phosphate. Which of the following oxidizing agents is NOT typically used in this conversion process?

A) Sodium nitrate B) Potassium permanganate C) Sodium peroxide D) Hydrogen peroxide

46. When testing for halogens, if the organic compound contains iodine, the sodium fusion extract, after acidification with nitric acid and addition of silver nitrate, gives a yellow precipitate. This precipitate is:

A) Silver chloride B) Silver bromide C) Silver iodide D) Silver nitrate

47. The Kjeldahl's method is primarily used for the quantitative estimation of:

A) Sulfur B) Halogens C) Nitrogen D) Phosphorus

48. Which of the following tests is specifically designed for the detection of halogens in organic compounds and involves heating the compound with copper powder on a wire loop in a flame?

A) Lassaigne's test B) Beilstein test C) Kjeldahl's test D) Dumas' test

49. In the Lassaigne's test for sulfur, if the sodium fusion extract is acidified with acetic acid and then treated with sodium nitroprusside, a violet color is observed. This is due to the formation of:

A) Sodium sulfide B) Iron(III) thiocyanate C) Sodium hexacyanoferrate(III) sulfide D) [Fe(CN)5NO]2- complex with S2-

Qualitative detection of N S P and halogens in organic compounds - Online Test

Test Results