Detection of Extra Elements:
1. How is nitrogen detected in an organic compound?
Answer: Nitrogen is detected using the Lassaigne’s test. The organic compound is fused with sodium to form sodium cyanide, which is then treated with ferrous sulfate and ferric chloride to form Prussian blue, indicating the presence of nitrogen.
2. Describe the test for the detection of sulfur in an organic compound.
Answer: Sulfur is detected by the sodium fusion test, where the organic compound is fused with sodium to form sodium sulfide, which reacts with lead acetate to form black lead sulfide.
3. How are halogens detected in organic compounds?
Answer: Halogens are detected using the Beilstein test. The organic compound is heated on a copper wire in a flame, producing a green flame if halogens are present.
Detection of Functional Groups:
4. How can the hydroxyl group in alcohols be detected?
Answer: The hydroxyl group in alcohols can be detected using the ceric ammonium nitrate test, where a red color indicates the presence of alcohols.
5. What test is used to detect phenolic hydroxyl groups?
Answer: The ferric chloride test is used to detect phenolic hydroxyl groups. A violet or green color indicates the presence of phenol.
6. How can aldehydes be distinguished from ketones?
Answer: Aldehydes can be distinguished from ketones using the Tollen’s reagent test, where aldehydes reduce Tollen’s reagent to form a silver mirror, whereas ketones do not react.
7. Describe the test for detecting carboxyl groups in organic compounds.
Answer: Carboxyl groups can be detected using the sodium bicarbonate test, where effervescence due to the release of carbon dioxide indicates the presence of a carboxyl group.
8. How are amino groups in organic compounds detected?
Answer: Amino groups can be detected using the ninhydrin test, where a blue or purple color indicates the presence of amino groups.
Preparation of Inorganic Compounds:
9. What is the chemistry involved in the preparation of Mohr’s salt?
Answer: Mohr’s salt is prepared by dissolving equimolar amounts of ferrous sulfate and ammonium sulfate in water, followed by crystallization.
10. How is potash alum prepared?
Answer: Potash alum is prepared by dissolving potassium sulfate and aluminum sulfate in water, then cooling the solution to crystallize potash alum.
Preparation of Organic Compounds:
11. Describe the preparation of acetanilide.
Answer: Acetanilide is prepared by acetylation of aniline with acetic anhydride in the presence of an acid catalyst.
12. How is p-nitroacetanilide synthesized?
Answer: p-Nitroacetanilide is synthesized by nitrating acetanilide with a mixture of concentrated sulfuric acid and nitric acid.
13. What is the process for preparing aniline yellow?
Answer: Aniline yellow is prepared by diazotizing aniline with nitrous acid, followed by coupling with aniline in a basic medium.
14. Describe the preparation of iodoform.
Answer: Iodoform is prepared by the haloform reaction, where acetone or ethanol is treated with iodine and sodium hydroxide, resulting in the formation of iodoform.
Titrimetric Exercises:
15. What is the principle behind the titration of oxalic acid with KMnO4?
Answer: The principle is based on the redox reaction where oxalic acid is oxidized by KMnO4 in an acidic medium, with the endpoint indicated by a persistent pink color.
16. Explain the titration of Mohr’s salt with KMnO4.
Answer: Mohr’s salt is titrated with KMnO4 in an acidic medium. The ferrous ion in Mohr’s salt is oxidized to ferric ion by KMnO4, with the endpoint indicated by a persistent pink color.
Qualitative Salt Analysis:
17. How is the cation Pb2+ identified in a qualitative salt analysis?
Answer: Pb2+ is identified by adding potassium chromate to the solution, resulting in a yellow precipitate of lead chromate.
18. Describe the identification of the anion Cl- in a salt analysis.
Answer: Cl- is identified by adding silver nitrate to the solution, resulting in a white precipitate of silver chloride that is soluble in ammonia.
Chemical Principles in Experiments:
19. What is the enthalpy of solution of CuSO4 and how is it measured?
Answer: The enthalpy of solution of CuSO4 is the heat change when CuSO4 dissolves in water. It is measured by dissolving a known amount of CuSO4 in water and recording the temperature change.
20. Explain the enthalpy of neutralization of a strong acid and strong base.
Answer: The enthalpy of neutralization is the heat change when an acid and a base react to form water. It is typically measured by mixing known concentrations of a strong acid and strong base and recording the temperature change.