CBSE Class 12 Chemistry notes and questions for Processes of Isolation of Elements Part C. Learning the important concepts is very important for every student to get better marks in examinations. The concepts should be clear which will help in faster learning. The attached concepts made as per NCERT and CBSE pattern will help the student to understand the chapter and score better marks in the examinations.
GENERAL PRINCIPLES AND PROCESSES OF
ISOLATION OF ELEMENTS
VSA QUESTIONS (1 - MARK QUESTIONS)
1. Name three metals which occur in native state in nature.
[Ans. : Au, Ag and Pt]
2. What are collectors in froth flotation process? Give one example.
[Ex. : Pine oil]
*3. Give the names and formulae of three ores which are concentrated by froth floatation process.
[Ans. : Galena (PbS), zinc blend (zns) cinnabar (HgS)]
4. Among Fe, Cu, Al and Pb, which metal (s) can not be obtained by smelting.
[Ans. : Al]
5. What is the thermodynamic criteria for the feasibility of a reaction?
[Ans. : G should be –ve or log K = + ve]
8. Why can’t aluminium be reduced by carbon?
[Hint : Al is stronger reducing agent than carbon]
9. Name the most important form of iron. Mention its one use.
[Ans. : Cast iron is used for making gutter pipes, castings, railway sleepers,
10. Name the impurities present in bauxite ore.
[Ans. : SiO2, Fe2O3 and TiO2]
11. What is the composition of copper matte?
[Hint : Cu2S and FeS]
12. Which from of copper is called blister copper?
13. What are froth stabilizers? Give two examples.
[Ex. : Cresol and aniline].
14. A sample of galena is contaminated with zinc blend. Name one chemical which can be used to concentrate galena selectively by froth floatation method. [Ans. : NaCN]
15. What are the constituents of German silver?
[Ans. : Cu = 25-30%, Zn = 25-30%, Ni = 40-50%]
16. Why is froth floatation process selected for concentration of the sulphide ore?
[Ans. : Sulphide ore particles are wetted by oil (Pine oil) and gangue particles by water]
17. Write the reaction involved in the extraction of copper from low grade ores.
[Ans. : First step is leaching of ore with acid or bacteria then
Cu2+ (aq) + H2 (g) Cu(s) + 2H+ (g)]
18. Although aluminium is above hydrogen in the electrochemical series, it is stable in air and water. Why?
19. Which method of purification is represented by the following reaction
20. Zinc is used but not copper for the recovery of metallic silver from the complex [Ag(CN)2]–, although electrode potentials of both zinc and copper are less than that of Ag. Explain why?
[Hint : Zinc reacts at faster rate as compared with copper, further zinc is cheaper than copper].
21. Write the composition of motlen mixture which is electrolysed to extract aluminium.
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