Qualitative detection of N S P and halogens in organic compounds - One Line Questions

1. 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 mixture of white and pale yellow precipitates
2. 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? — Add silver nitrate solution
3. 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? — Add lead acetate solution
4. The yellow precipitate formed with ammonium molybdate in the test for phosphorus is chemically known as: — Ammonium phosphomolybdate
5. A white precipitate, insoluble in dilute nitric acid but soluble in ammonium hydroxide, is formed when testing for halogens. This indicates the presence of: — Chlorine
6. 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: — Bromine
7. A yellow precipitate, insoluble in ammonium hydroxide, is formed when testing for halogens using the Lassaigne's test. This indicates the presence of: — Iodine
8. The detection of phosphorus in organic compounds typically involves its oxidation to phosphate. Which method is commonly used for this purpose? — Sodium fusion followed by oxidation
9. The qualitative detection of halogens in organic compounds is most commonly done using which test? — Sodium fusion test (Lassaigne's test)
10. Which method is generally employed for the qualitative detection of sulfur in organic compounds? — Sodium fusion test (Lassaigne's test)
11. 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? — Fe4[Fe(CN)6]3
12. Which reagent is used to detect sulfide ions formed in the Lassaigne's test for sulfur? — Lead acetate
13. Which reagent is used to detect the presence of cyanide ions in the Lassaigne's extract when testing for nitrogen? — Ferrous sulfate
14. 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? — Sodium nitroprusside
15. Which of the following is a characteristic observation for the detection of sulfur using the Lassaigne's test? — Black precipitate with lead acetate
16. Which of the following is NOT a characteristic observation for the Lassaigne's test for nitrogen? — A pale green solution
17. 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? — Nitric acid
18. Which of the following is a limitation of the Beilstein test for halogens? — It gives a positive test for some non-halogen compounds.
19. 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? — Beilstein test
20. 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. — Lead(II) sulfide
21. Which method is commonly used for the qualitative detection of nitrogen in organic compounds? — Dumas' method
22. 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: — Sulfur
23. Which of the following elements cannot be detected using the Lassaigne's test? — Phosphorus
24. 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: — Halogen
25. 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: — Halogens
26. Which element's detection involves the formation of a colored complex with iron(III) chloride after oxidation? — Phosphorus
27. Which of the following elements can be detected using a simple flame test with copper wire (Beilstein test)? — Halogens
28. A violet color with sodium nitroprusside in the Lassaigne's test for a compound containing both N and S indicates the presence of: — Both Nitrogen and Sulfur
29. 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? — Lassaigne's test for phosphorus
30. Which of the following pairs of elements and their characteristic Lassaigne's test observations is INCORRECT? — Phosphorus: Yellow precipitate with sodium cobalt nitrite
31. 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: — Phosphoric acid
32. 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: — Both Prussian blue and iron(II) sulfide
33. Which of the following precipitates formed with silver nitrate in the Lassaigne's test for halogens is insoluble in ammonium hydroxide? — Silver iodide
34. 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: — Silver iodide
35. Which of the following statements is true regarding the detection of halogens using silver nitrate after sodium fusion? — Silver chloride is soluble in ammonium hydroxide.
36. Which reagent is used to detect the presence of phosphate ions in the qualitative analysis of phosphorus in organic compounds? — Ammonium molybdate
37. In the Lassaigne's test, if the organic compound contains both nitrogen and sulfur, what is formed upon fusion with sodium metal? — Sodium cyanide and sodium sulfide
38. 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? — Hydrogen peroxide
39. 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? — Sodium phosphate
40. 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: — [Fe(CN)5NO]2- complex with S2-
41. The Kjeldahl's method is primarily used for the quantitative estimation of: — Nitrogen
42. 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: — Nitrogen
43. 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? — Sulfuric acid might react with ferrous sulfate, leading to erroneous results.
44. 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? — To convert nitrogen into sodium cyanide
45. In the Lassaigne's test for halogens, why is the sodium fusion extract acidified with nitric acid before adding silver nitrate? — To prevent the precipitation of other silver salts like silver carbonate
46. 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? — Use sulfuric acid for acidification
47. 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? — Yellow precipitate of ammonium phosphomolybdate
48. When sodium sulfide from the Lassaigne's extract is treated with lead acetate solution, what is the observation if sulfur is present? — Black precipitate of lead(II) sulfide
49. 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? — Blue precipitate of Prussian blue
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