CBSE Guess > Papers > Important Questions > Class XII > 2013 > Chemistry > General principles and process of isolation of elements By Mr. R. Srinivas Vasudevamurthy

CBSE CLASS XII

General principles and process of isolation of elements - 3 Marks

1. Distinguish between mineral and ore.

2. Mention the steps involved in metallurgy.

3. Name the important ores of Al, Fe, Cu and Zn.

4. Explain the principles of

a) Hydraulic washing
b) agnetic separation
c) Froth floatation.

5. What is the role of depressant in froth floatation process? Name the depressant used in case of ore containing ZnS and PbS.

6. Mention the principle of leaching. Write the reactions involved in leaching of aluminium.

7. Write the reactions involved in leaching of Ag and Au.

8. Write the reactions involved in the extraction of

a) Fe from hematite ore
b) Cu from copper pyrite ore
c) Zn from zinc blend ore
d) Al from alumina

9. Explain roasting and calcinations with examples.

10. What is the role of cryolite in the extraction of Al from alumina?

11. How is copper extracted from its low grade ore and scraps?

12. Mention the principles of refining the metals by

a) Distillation
b) Liquation
c) Electrolytic refining
d) Zone refining
e) Vapour phase refining

13.  Explain the electrolytic refining of copper with the reactions involved at each electrode.

14. Mention the uses of Al, Cu, Zn , cast iron, wrought iron and steel.

15. Although thermodynamically feasible, in practice Mg is not used to reduce alumina. Why?

16. Why is the reduction of metal oxide easier if the metal formed is in liquid state at the temperature of reduction?

17. Cr₂O₃ + 2Al Al₂O₃+2Cr   ∆G⁰ = - 421 KJ/mole is thermodynamically feasible as is apparent from negative value of  ∆G0. Why does it not occur at room temperature ?

18. Is it true that under certain condition Mg can reduce Al₂O₃ and Al can reduce MgO? What are those conditions?

19. Out of Zn and Fe scraps, which is suitable to reduce leached copper ore and why?

20. Copper can be extracted by hydrometallurgy but not zinc. Why?

21. Mention the principle of chromatography.

22. Explain column chromatography.

23. What criterion is used for the selection of stationary phase in chromatography?

24. How is cast iron different from wrought iron?

25. Why is copper mate put in silica lined converter/

26. Out of C and Co, which is a better reducing agent for reducing ZnO and why?

27. Name the process by which chlorine is obtained as by product. What will happen when an aqueous solution of NaCl is electrolysed?

28.Standard  Free energy of formation of Cr₂O₃ and Al₂O₃ are given as – 540KJ/mole and - 827KJ/mole respectively. Is it possible to reduce Cr₂O₃ using Al?

29. ∆_fG MgO and ∆_fG CO are given below

∆_fG MgO(s)  at 1273 K = - 941 KJ/mole
∆_fG MgO(s) at 2273K = - 314 KJ/mole
∆_fG CO (g) at 1273 K = - 439 KJ/mole
∆_fG CO (g) at 2273 K&n = -628 KJ/mo

Determine which temperature is suitable for reduction of MgO using C?

 

Submitted By : Mr. R. Srinivas Vasudevamurthy
Email: [email protected]