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Metallurgy Book Back Questions

12th Standard EM

Reg.No. :
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Chemistry

Time : 01:00:00 Hrs
Total Marks : 50
5 x 1 = 5
1. In the electrolytic refining of copper, which one of the following is used as anode?

(a)

Pure copper

(b)

Impure copper

(c)

Carbon rod

(d)

Platinum electrode

2. Which of the following plot gives Ellingham diagram

(a)

$\Delta SVsT$

(b)

$\Delta { G }^{ 0 }VsT$

(c)

$\Delta { G }^{ 0 }Vs\cfrac { 1 }{ T }$

(d)

$\Delta { G }^{ 0 }Vs{ T }^{ 2 }$

3. In the Ellingham diagram, for the formation of carbon monoxide

(a)

$\left( \cfrac { \Delta { S }^{ 0 } }{ \Delta T } \right)$

(b)

$\left( \cfrac { \Delta { G }^{ 0 } }{ \Delta T } \right)$ is positive

(c)

$\left( \cfrac { \Delta { G }^{ 0 } }{ \Delta T } \right)$ is negative

(d)

initially $\left( \cfrac { \Delta T }{ \Delta { G }^{ 0 } } \right)$ is positive, after 700oC,$\left( \cfrac { \Delta { G }^{ 0 } }{ \Delta T } \right)$ is negative

4. Which of the following reduction is not thermodynamically feasible?

(a)

${ Cr }_{ 2 }{ O }_{ 3 }+2Al\longrightarrow { Al }_{ 2 }{ O }_{ 3 }+2Cr$

(b)

${ Al }_{ 2 }{ O }_{ 3 }+2Cr\longrightarrow { Cr }_{ 2 }{ O }_{ 3 }+2Sl$

(c)

$3Ti{ O }_{ 2 }+4Al\longrightarrow 2A{ l }_{ 2 }{ O }_{ 3 }+3Ti$

(d)

none of these

5. Which of the following is not true with respect to Ellingham diagram?

(a)

Free energy changes follow a straight line. Deviation occurs when there is a phase change.

(b)

The graph for the formation of CO2 is a straight line almost parallel to free energy axis.

(c)

Negative slope of CO shows that it becomes more stable with increase in temperature

(d)

Positive slope of metal oxides shows that their stabilities decrease with increase in temperature

6. 6 x 2 = 12
7. What is the difference between minerals and ores?

8. What are the various steps involved in extraction of pure metals from their ores?

9. What is the role of Limestone in the extraction of Iron from its oxide Fe2O3?

10. Which type of ores can be concentrated by froth floatation method? Give two examples for such ores.

11. Out of coke and CO, which is better reducing agent for the reduction of ZnO? Why?

12. Describe a method for refining nickel

13. 6 x 3 = 18
14. Explain zone refining process with an example using the Ellingham diagram given below

15. (A) Predict the conditions under which
(i) Aluminium might be expected to reduce magnesia.
(ii) Magnesium could reduce alumina.
(B) Carbon monoxide is more effective reducing agent than carbon below 983K but, above this temperature, the reverse is true –Explain.
(c) it is possible to reduce Fe2O3 by coke at a temperature around 1200K

16. Give the uses of zinc.

17. Explain the electrometallurgy of aluminium

18. Explain the following terms with suitable examples.
(i) Gangue
(ii) slag

19. Give the basic requirement for vapour phase refining.

20. 3 x 5 = 15
21. The selection of reducing agent depends on the thermodynamic factor: Explain with an example.

22. Give the limitations of Ellingham diagram

23. Write a short note on electrochemical principles of metallurgy.