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Additional Questions - Chapter 1 - Metallurgy - 12th Chemistry Guide Samacheer Kalvi Solutions

Updated On 11-02-2025 By Lithanya


Additional Questions
1 Mark Questions and Answers
I. Choose the best answer:
Question 1.

Chemical formula of bauxite is
(a) $\mathrm{Fe}_2 \mathrm{O}_3$
(b) $\mathrm{Fe}_2 \mathrm{O}_3 \cdot \mathrm{FeO}$
(c) $\mathrm{Al}_2 \mathrm{O}_3 \cdot \mathrm{H}_2 \mathrm{O}$
(d) $\mathrm{Al}_2 \mathrm{O}_3 \cdot 2 \mathrm{H}_2 \mathrm{O}$
Answer:
(d) $\mathrm{Al}_2 \mathrm{O}_3 \cdot 2 \mathrm{H}_2 \mathrm{O}$
Question 2.
An example of an oxide ore is
(a) malachite
(b) bauxite
(c) galena
(d) zinc blende
Answer:
(b) bauxite
Question 3.
Froth floatation process involves the
(a) treatment of the ore with water and pine oil
(b) washing of the ore with a steam of water
(c) owing off the ore over a conveyor belt rolling over magnetic roller
(d) melting of ore
Answer:
(a) treatment of the ore with water and pine oil

Question 4.
In the froth floatation process for the purification of ores the particles float because
(a) they are light
(b) their surface is not easily wetted by water
(c) they bear electrostatic charge
(d) they are insoluble
Answer:
(b) their surface is not easily wetted by water
Question 5 .
In a metallurgical process, an acid flux is used for removing
(a) Slag
(b) basic flux
(c) acidic gangue
(d) basic gangue
Answer:
(d) basic gangue
Question 6.
The process of the removal of impurities from a crude metal is called
(a) concentration
(b) calcination
(c) refining
(d) roasting
Answer:
(c) refining
Question 7.
Which of the following metal is obtained by self reduction method?
(a) $\mathrm{Fe}$
(b) $\mathrm{Cu}$
(c) $\mathrm{Ag}$
(d) $\mathrm{Mg}$
Answer:
(b) $\mathrm{Cu}$
Question 8.
Which one of the following ore is best concentrated by froth floatation method?
(a) Magnetite
(b) Malachite
(c) Galena
(d) Haematite

Answer:

(c) Galena

Question 9.
Heating mixture of $\mathrm{Cu}_2 \mathrm{O}$ and $\mathrm{Cu}_2 \mathrm{~S}$ will give
(a) $\mathrm{Cu}+\mathrm{SO}_2$
(b) $\mathrm{Cu}+\mathrm{SO}_3$
(c) $\mathrm{CuO}+\mathrm{CuS}$
(d) $\mathrm{Cu}_2 \mathrm{SO}_3$
Answer:
(a) $\mathrm{Cu}+\mathrm{SO}_2$
Question 10.
Which of the following pairs of metals is purified by Van-Arkel method?
(a) $\mathrm{Ag}$ and $\mathrm{Au}$
(b) $\mathrm{Ni}$ and $\mathrm{Fe}$
(c) Ga and In
(d) $\mathrm{Zr}$ and $\mathrm{Ti}$
Answer:
(d) $\mathrm{Zr}$ and $\mathrm{Ti}$
Question 11.
Aluminium is extracted from alumina $\left(\mathrm{Al}_2 \mathrm{O}_3\right)$ by electrolysis of a molten mixture of .
(a) $\left(\mathrm{Al}_2 \mathrm{O}_3\right)+\mathrm{KF}+\mathrm{Na}_3 \mathrm{AlF}_6$
(b) $\left(\mathrm{Al}_2 \mathrm{O}_3\right)+\mathrm{HF}+\mathrm{NaAlF}_4$
(c) $\left(\mathrm{Al}_2 \mathrm{O}_3\right)+\mathrm{CaF}_2+\mathrm{NaAlF}_4$
(d) $\left(\mathrm{Al}_2 \mathrm{O}_3\right)+\mathrm{Na}_3 \mathrm{AlF}_6+\mathrm{CaF}_2$
Answer:
(d) $\left(\mathrm{Al}_2 \mathrm{O}_3\right)+\mathrm{Na}_3 \mathrm{AlF}_6+\mathrm{CaF}_2$
Question 12.
The ore which contains both copper and iron
(a) Cuprite
(b) Haematite
(c) Copper pyrite
(d) Malachite
Answer:
(c) Copper pyrite
Question 13.
Match the extraction processes listed in Column-I with metals listed in Column-II.

(a) $\mathrm{A}-2, \mathrm{~B}-1, \mathrm{C}-4, \mathrm{D}-3$
(b) $\mathrm{A}-3, \mathrm{~B}-4, \mathrm{C}-1, \mathrm{D}-2$
(c) $\mathrm{A}-3, \mathrm{~B}-1, \mathrm{C}-2, \mathrm{D}-4$
(d) $\mathrm{A}-4, \mathrm{~B}-2, \mathrm{C}-1, \mathrm{D}-3$
Answer:
(c) $\mathrm{A}-3, \mathrm{~B}-1, \mathrm{C}-2, \mathrm{D}-4$
Question 14.
Chief ore of aluminium is
(a) bauxite
(b) clay
(c) haematite
(d) magnetite
Answer:
(a) bauxite
Question 15 .
Which one of the following metal having least chemical reactive?
(a) $\mathrm{Na}$
(b) $\mathrm{Mg}$
(c) $\mathrm{Al}$
(d) $\mathrm{Au}$
Answer:
(d) $\mathrm{Au}$
Question 16.
Pick out the more reactive metal.
(a) $\mathrm{Cu}$
(b) $\mathrm{Ag}$
(c) $\mathrm{Au}$
(d) $\mathrm{Na}$
Answer:
(d) $\mathrm{Na}$
Question 17.
Consider the following statements.
(i) All ores are minerals but all minerals are not ores.
(ii) Bauxite is an ore of aluminium while clay is not.
(iii) Extraction of aluminium form clay is profitable one.
Which of the above statement(s) is / are not correct?

(a) (i) only
(b) (ii) only
(c) (iii) only
(d) (i), (ii) and (iii)
Answer:
(c) (iii) only
Question 18.
Match the List-I and List-II correctly using the code given below.

Answer:
(c) $3,4,2,1$
Question 19.
The impurities associated with ores is
(a) flux
(b) slag
(c) gangue
(d) metal
Answer:
(c) gangue
Question 20.
Oxide ores are concentrated by
(a) handpicking
(b) hydraulic washing
(c) froth floatation process
(d) Magnetic separation process
Answer:
(b) hydraulic washing
Question 21.
Haematite and tin stone are purified by
(a) gravity separation process
(b) magnetic separation process
(c) froth floatation process
(d) handpicking
Answer:
(a) gravity separation process
Question 22.
Froth floatation process is applicable for
(a) oxide ores
(b) carbonate ores
(c) chloride ores
(d) sulphide ores
Answer:
(d) sulphide ores

Question 23.
Copper pyrite and zinc blende are purified by
(a) gravity separation process
(b) magnetic separation process
(c) froth floatation process
(c) handpicking
Answer:
(c) froth floatation process
Question 24 .
Frothing agent used in froth floatation process is
(a) pine oil
(b) olive oil
(c) mustard oil
(d) neem oil
Answer:
(a) pine oil
Question 25.
Depressing agents used to separate $\mathrm{ZnS}$ from $\mathrm{PbS}$ is
(a) $\mathrm{NaCN}$
(b) $\mathrm{NaCl}$
(c) $\mathrm{NaNO}_3$
(d) $\mathrm{NaNO}_2$
Answer:
(a) $\mathrm{NaCN}$
Question 26.
Leaching is also called as
(a) hand picking
(b) Electrolysis
(c) Chemical process
(d) magnetic separation process
Answer:
(c) Chemical process
Question 27.
In the leaching process, the metal present in the ore is converted into
(a) soluble salt
(b) soluble complex

Question 32.
The process in which the concentrated ore is strongly heated in the absence of air is called as
(a) Roasting
(b) Calcination
(c) Smelting
(d) Leaching
Answer:
(b) Calcination
Question 33.
A chemical substance that forms an easily fusible slag with gangue is called as
(a) flux
(b) pure metal
(c) ore
(d) impure metal
Answer:
(a) flux
Question 34.
Blistered copper is
(a) $98 \%$ pure copper
(b) $96 \%$ pure copper
(c) $97 \%$ pure copper
(d) $88 \%$ pure copper
Answer:
(a) $98 \%$ pure copper
Question 35 .
Ignition mixture used in aluminothermic process is
(a) $\mathrm{Mg}+\mathrm{BaO}_2$
(b) $\mathrm{MgO}+\mathrm{BaO}$
(c) $\mathrm{Al}_2 \mathrm{O}_3+\mathrm{Mg}$
(d) $\mathrm{Al}_2 \mathrm{O}_3+\mathrm{BaO}_2$
Answer:
(a) $\mathrm{Mg}+\mathrm{BaO}_2$

Question 36.
For spontaneous reaction, the change in free energy should be
(a) positive
(b) negative
(c) zero
(d) neutral
Answer:
(b) negative
Question 37.
The change in Gibbs free energy for a reaction is expressed by
(a) $\Delta \mathrm{G}=\Delta \mathrm{H}+\mathrm{T} \Delta \mathrm{S}$
(b) $\Delta \mathrm{G}=\Delta \mathrm{H}-\mathrm{TS}$
(c) $\mathrm{G}=\mathrm{H}-\mathrm{TS}$
(d) $\Delta \mathrm{G}=\Delta \mathrm{H}-\mathrm{T} \Delta \mathrm{S}$
Answer:
(d) $\Delta \mathrm{G}=\Delta \mathrm{H}-\mathrm{T} \Delta \mathrm{S}$
Question 38.
Relationship between $\Delta \mathrm{G}^{\circ}$ and $\mathrm{K}_{\mathrm{p}}$ is
(a) $\Delta \mathrm{G}^{\circ}=-\mathrm{RT}$ In $\mathrm{K}_{\mathrm{p}}$
(b) $\Delta \mathrm{G}^{\circ}=-\mathrm{R} \operatorname{In} \mathrm{K}_{\mathrm{p}}$
(c) $\Delta \mathrm{G}^{\circ}=-\mathrm{T} \operatorname{In} \mathrm{K}_{\mathrm{p}}$
(d) $\Delta \mathrm{G}^{\circ}=\mathrm{RT} \operatorname{In} \mathrm{K}_{\mathrm{p}}$
Answer:
(a) $\Delta \mathrm{G}^{\circ}=-\mathrm{RT} \operatorname{In} \mathrm{K}_{\mathrm{p}}$
Question 39.
Consider the following statements.
(i) Ellingham drawn on a plot by considering the temperature in the $\mathrm{x}$-axis and the standard free energy change for the formation of metal oxide in y-axis.
(ii) The resultant plot is straight line.
(ii) In the Ellingham diagram, $\Delta \mathrm{H}$ as slope and $\Delta \mathrm{S}$ as y-intercept.

Which of the above statement(s) is / are not correct?
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (ii) only
(d) (iii) only
Answer:
(d) (iii) only
Question 40.
Which of the following oxides is unstable $\mathrm{j}$ at moderate temperature?
(a) $\mathrm{Al}_2 \mathrm{O}_3$
(b) $\mathrm{Cr}_2 \mathrm{O}_3$
(c) $\mathrm{MgO}$
(d) $\mathrm{HgO}$
Answer:
(d) $\mathrm{HgO}$
Question 41.
The oxides will decompose on heating even in the absence of a reducing agent is
(a) $\mathrm{Ag}_2 \mathrm{O}$
(b) $\mathrm{HgO}$
(c) $\mathrm{MgO}$
(d) both (a) and (b)
Answer:
(d) both (a) and (b)
Question 42.
Consider the following statements.
(i) Ellingham diagram gives information about the thermodynamic feasibility of a reaction.
(ii) It explains the rate of the reaction.
(iii) Below $1000 \mathrm{~K}$ temperature, $\mathrm{FeO}$ is more stable than $\mathrm{CO}$.
Which of the above statements (s) is / are not correct?
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) only

(d) (ii) only
Answer:
(d) (ii) only
Question 43.
Gibbs free energy change for the electrolysis process is expressed by
(a) $\Delta \mathrm{G}^{\circ}=-\mathrm{nFE}^{\circ}$
(b) $\Delta G^{\circ}=n F$
(c) $\Delta \mathrm{G}^{\circ}=-\mathrm{nE}^{\circ}$
(d) $\Delta \mathrm{G}^{\circ}=\mathrm{nFE}^{\circ}$
Answer:
(a) $\Delta \mathrm{G}^{\circ}=-\mathrm{nFE}^{\circ}$
Question 44.
The technique used to refining zine and mercury is
(a) Liquation
(b) Distillation
(c) Zone refining
(d) Van-Arkel method
Answer:
(b) Distillation
Question 45.
Which of the following is not purified by zone refining process?
(a) $\mathrm{Ge}$
(b) $\mathrm{Si}$
(c) $\mathrm{Ga}$
(d) $\mathrm{Al}$
Answer:
(d) $\mathrm{Al}$

Question 46.
Nickel is purified by
(a) Mond process
(b) Van-Arkel method
(c) Zone refining
(d) Electrolytic refining
Answer:
(a) Mond process
Question 47.
Titanium is purified by
(a) Mond process
(b) Van-Arkel method
(c) Zone refining
(d) Electrolytic refining
Answer:
(b) Van-Arkel method
Question 48.
The metal used for galvanisation of iron is
(a) $\mathrm{Al}$
(b) $\mathrm{Zn}$
(c) $\mathrm{Cu}$
(d) $\mathrm{Au}$
Answer:
(b) $\mathrm{Zn}$
Question 49.
Which metal alloy is used in design of aeroplane parts?
(a) $\mathrm{Al}$
(b) $\mathrm{Zn}$
(c) $\mathrm{Cu}$
(d) $\mathrm{Au}$
Answer:
(a) $\mathrm{Al}$

Question 50.
Which metal is used for making coins and ornaments along with gold and other metals?
(a) $\mathrm{Zn}$
(b) $\mathrm{Al}$
(c) $\mathrm{Cu}$
(d) $\mathrm{Fe}$
Answer:
(c) $\mathrm{Cu}$
II. Fill in the blanks:
1. Minerals that contains a high percentage of metal from which it can be extracted conveniently and economically are called .............
2. .............. helps us to select a suitable reducing agent and appropriate temperature range for reduction.
3. If $\mathrm{E}^{\circ}$ is positive, then the $\Delta \mathrm{G}$ is. ...................
4. Chemical formula of cuprite is ...............
5. Gravity separation is also called as....................

6. ............ ore is purified by gravity separation process.
7. In froth floatation process .............. acts as a collector.
8. Sodium cyanide is added to depresses the floatation property of $\mathrm{ZnS}$ by forming a layer of ................
9. The process of gold reduced to its elemental state is called
10. Leaching process is a ................. reaction.
11. Magnesite is calcined to give .........................
$12 . \ldots \ldots \ldots \ldots \ldots$ a chemical substance that forms an easily fusible slag with gangue.
13. Flux + Gangue $\rightarrow \ldots \ldots \ldots \ldots$
14. In the extraction of iron ................ is removed as slag.
15. In the extraction of copper ...............is removed as slag.
16. $\mathrm{Cr}_2 \mathrm{O}_3$ can be reduced by ............ an process.
17. ................. is used as a reducing agent for the reduction of chromic oxide.
$18 . \ldots \ldots \ldots \ldots \ldots$ is purified by zone refining.
19. In the mond process, impure nickel is heated with ............. compound.
20............... filament is used to decompose titanium tetraoxide.
21. is the most abundant metal.
22. is used in packing materials for food items.
23. ............. is used in the manufacture of paints, rubber and cosmetics.
24. ............................. is the first metal used by the humans.
25. .................... is one of the expensive and precious metals.
26. ..................... is used for increasing the efficiency of solar cells and also used as catalysts.
$27 . \ldots \ldots \ldots \ldots \ldots$ ore is concentrated by froth floatation process.
28. Zinc blende is concentrated by ...............
29. Gold ore is leached by adding of ......................

Answer:

1. Ores
2. Ellingham diagram
3. negative
4. $\mathrm{Cu}_2 \mathrm{O}$
5. Hydraulic washing
6. oxide
7. Sodium ethyl xanthate
8. $\mathrm{Na}_2\left[\mathrm{Zn}(\mathrm{CN})_4\right]$ - Sodium negative
9. Cementation
10. Redox
11. Magnesia
12. Flux
13. slag
14. Calcium silicate $\left(\mathrm{CaSiO}_3\right)$
15. Ferrous silicate $\left(\mathrm{FeSiO}_3\right)$
16. Aluminothermic process
17. Aluminium
18. semi-conductior
19. carbon monoxide
20. Tungsten
21. Aluminium
22. Aluminium foils
23. Aluminium
24. Zinc oxide
25. Copper
26. Gold
27. Gold nanoparticle
28. Sulphide
29. Froth floatation

III. Match the following:
Question 1.

(i) Haematite - (a) $\mathrm{Fe}_3 \mathrm{O}_4$
(ii) Siderite - (b) $\mathrm{Fe}_3 \mathrm{O}_3$
(iii) Iron pyrite - (c) $\mathrm{Fe}_3 \mathrm{O}_3$
(iv) Magnetite - (d) $\mathrm{FeS}_2$
Answer:
(i) - (b)
(ii) $-(\mathrm{c})$
(iii) $-(\mathrm{d})$
(iv) - (a)
Question 2.
(i) Copper glance - (a) $\mathrm{CuCO}_3 \cdot \mathrm{Cu}(\mathrm{OH})_2$
(ii) Malachite - (b) $\mathrm{Cu}_2 \mathrm{~S}$
(iii) Copper pyrite - (c) $2 \mathrm{CuCO}_3 \cdot \mathrm{Cu}(\mathrm{OH})_2$
(iv) Azurite - (d) $\mathrm{CuFeS}_2$
Answer:
(i) - (b)
(ii) - (a)
(iii) $-(\mathrm{d})$
(iv) - (c)
Question 3.
(i) Zinc blende - (a) $\mathrm{Al}_2 \mathrm{O}_3 \cdot 2 \mathrm{H}_2 \mathrm{O}$
(ii) Bauxite - (b) $\mathrm{ZnCO}_3$
(iii) $\mathrm{Zincite}-$ (c) $\mathrm{ZnS}$
(iv) Calamine - (d) $\mathrm{ZnO}$
Answer:
(i) - (c)
(ii) - (a)
(iii) $-(\mathrm{d})$
(iv) - (b)

Question 4.
(i) Tin stone - (a) $\mathrm{AgCl}$
(ii) Argentite - (b) $\mathrm{Ag}_3 \mathrm{SbS}_3$
(iii) Ruby silver - (c) $\mathrm{Ag}_2 \mathrm{~S}$
(iv) Horn silver - (d) $\mathrm{SnO}_2$
Answer:
(i) - (d)
(ii) $-(\mathrm{c})$
(iii) - (b)
(iv) - (a)
Question 5.
(i) Oxide ore - (a) Zinc blende
(ii) Carbonate ore - (b) Horn silver
(Hi) Sulphide ore - (c) Haematite
(iv) Chloride ore - (d) Calamine
Answer:
(i) - (c)
(ii) $-(\mathrm{d})$
(iii) - (a)
(iv) - (b)
Question 6.
(i) Tin stone - (a) Magnetic separation process
(ii) Copper pyrite - (b) Leaching process
(Hi) Bauxite - (c) Froth floatation process
(iv) Chromite - (d) Hydraulic washing process
Answer:
(i) $-(\mathrm{d})$
(ii) $-(\mathrm{c})$
(iii) - (b)
(iv) - (a)
Question 7.
(i) Aluminium - (a) cosmetics
(ii) Zinc oxide - (b) gas pipelines
(iii) Iron - (c) making coins
(iv) Copper - (d) bicycle chains

Answer:
(i) - (b)
(ii) $-($ a)
(iii) $-(\mathrm{d})$
(iv) - (c)
Question 8.
(i) Gold nanopaticle - (a)Cast iron
(ii) Cast iron - (b) Cooking vessels
(iii) Metallic zinc - (c) Solar cells
(iv) Aluminium - (d) Pump stoves
Answer:
(i) - (c)
(ii) $-(\mathrm{d})$
(iii) $-($ a)
(iv) - (b)
IV. Assertion and reasons:
Note:
In the following questions a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) $A$ and $R$ are correct, $R$ explains $A$
(b) $\mathrm{A}$ and $\mathrm{R}$ are correct, $\mathrm{R}$ does not explains $\mathrm{A}$
(c) $\mathrm{A}$ is correct but $\mathrm{R}$ is wrong
(d) $\mathrm{A}$ is wrong but $\mathrm{R}$ is correct
Question 1.
Assertion(A) - Clay is an ore of aluminium while bauxite is not.
Reason (R) - Aluminium can be economically extracted from bauxite not from clay.
Answer:
(d) $A$ is wrong but $R$ is correct
Question 2.
Assertion(A) - Haematite and tin stone are concentrated by hydraulic washing process. Reason (R) - Oxide ores are heavy and have high specific gravity.
Answer:
(a) $\mathrm{A}$ and $\mathrm{R}$ are correct, $\mathrm{R}$ explains $\mathrm{A}$.

Question 3 .
Assertion(A) - Sulphide ores are concentrated by froth floatation process.
Reason (R) - Sulphide ores are preferentially wetted by oil can be separated from gangue. Answer:
(a) $\mathrm{A}$ and $\mathrm{R}$ are correct, $\mathrm{R}$ explains $\mathrm{A}$
Question 4.
Assertion(A) - A suitable reducing agent is selected based on the thermodynamic consideration. Reason (R) - The reduction of metal oxide with a given reducing agent can occur if the free energy change for the coupled reaction is positive.
Answer:
(c) $\mathrm{A}$ is correct but $\mathrm{R}$ is wrong
Question 5.
Assertion(A) - Aluminium can be used as a reducing agent for the reduction of chromic oxide.
Reason (R) - In the Ellingham diagram, formation of chromium oxide lies above that of the aluminium, therefore $\mathrm{Al}_2 \mathrm{O}_3$ is more stable than $\mathrm{Cr}_2 \mathrm{O}_3$.
Answer:
(a) $\mathrm{A}$ and $\mathrm{R}$ are correct, $\mathrm{R}$ explains $\mathrm{A}$
Question 6.
Assertion(A) - Zone refining is based on the principles of fractional crystallisation, Reason (R) - This process is carried out in an inert gas temperature.
Answer:
(b) $\mathrm{A}$ and $\mathrm{R}$ are correct, $\mathrm{R}$ does not explain $\mathrm{A}$
Question 7.
Assertion(A) - Aluminium is used in the $\mathrm{j}$ design of chemical reactors.
Reason (R) - Aluminium has high resistance to corrosion.
Answer:
(a) A and R are correct, $\mathrm{R}$ explains $\mathrm{A}$
V. Find the odd one out and give the reasons:

Question 1.
(a) Nickel
(b) Silicon
(c) Germanium
(d) Galium
Answer:
(a) Nickel
Reason:
$\mathrm{Si}, \mathrm{Ge}$ and $\mathrm{Ga}$ are purified by I zone refining while $\mathrm{Ni}$ is not.
Question 2.
(a) Copper
(b) Zinc
(c) Silver
(d) Galium
Answer:
(d) Galium
Reason:
$\mathrm{Cu}, \mathrm{Zn}$ and $\mathrm{Ag}$ are purified by electrolytic refining while $\mathrm{Ga}$ is not.
Question 3.
(a) $\Delta \mathrm{G}=-\mathrm{ve}$
(b) $\Delta \mathrm{H}=-\mathrm{ve}$
(c) $\Delta \mathrm{S}=+\mathrm{ve}$
(d) $\Delta \mathrm{S}=-\mathrm{ve}$
Answer:
(d) $\Delta \mathrm{S}=-\mathrm{ve}$
Reason:
$\Delta \mathrm{G}=$-ve, $\Delta \mathrm{H}=$-ve, $\Delta \mathrm{S}=+$ ve are the conditions for spontaneous reaction, $\Delta \mathrm{S}=$-ve is condition for non-spontaneous process.

Question 4.
(a) Haematite
(b) Siderite
(c) Limonite
(d) Azunte
Answer:
(a) Azurite
Reason:
Azurite is ore of copper but others arc ore of iron.
Question 5 .
(a) Copper glance
(b) Zinc blende
(c) Argentite
(d) Magnetite
Answer:
(d) Magnetite
Reason:
Magnetite is oxide ore but others are sulphide ores.
Question 6.
(a) Silver
(b) Gold
(c) Sodium
(d) Platinum
Answer:
(c) Sodium
Reason:
Sodium is more reactive element than $\mathrm{Ag}, \mathrm{Au}$ and Pt.
VI. Find out the correct pair:
Question 1 .
(a) Metallurgy - Extraction of metals
(b) Clay - Ore of $\mathrm{Al}$
(c) $\mathrm{Na}$ - Native element
(d) Ore - Gangue
Answer:
(a) Metallurgy Extraction of metals

Question 2.
(a) Bauxite - Iron
(b) Siderite - Aluminium
(c) Malachite - Copper
(d) Argentite - Gold
Answer:
(c) Malachite - Copper
Question 3.
(a) Limonite - Sulphide ore
(b) Cuprite - Oxide ore
(c) Calamine - Suiphide ore
(d) Horn silver - Oxide ore
Answer:
(b) Cuprite - Oxide ore
Question 4.
(a) Oxide ore - Froth floatation process
(b) Suiphide ore - Gravity separation process
(c) Gold ore - Leaching method
(d) Oxide ore - Magnetic separation process
Answer:
(c) Gold ore - Leaching method
Question 5.
(a) Aluminium - Galvanising metals
(b) Zinc - Cooking vessels
(c) Iron - Cutlery
(d) Copper - Dental fillings
Answer:
(c) Iron-Cutlery
VII. Find out the incorrect pair:
Question 1.

(a) Copper - Least reactive
(b) Clay - Mineral of $\mathrm{Al}$
(c) Bauxite - Mineral of $\mathrm{Al}$
(d) Gangue - Impurity
Answer:
(c) Bauxite - Mineral of $\mathrm{Al}$

Question 2.
(a) Aluminium - Corundum
(b) Limonite - Iron
(c) Galena - Lead
(d) Tin - Siderite
Answer:
(d) Tin - Siderite
Question 3.
(a) Magnetite - $\mathrm{FeO}_4$
(b) Malachite $-\mathrm{CuCO}_3 \cdot \mathrm{Cu}(\mathrm{OH})_2$
(c) Horn silver $-\mathrm{Ag}_2 \mathrm{~S}$
(d) Stefinite $-\mathrm{Ag}_2 \mathrm{SbS}_4$
Answer:
(c) Horn silver $-\mathrm{Ag}_2 \mathrm{~S}$
Question 4.
(a) Tin stone - Oxide ore
(b) Copper pyrite - Oxide ore
(c) Zincite - Oxide ore
(d) Bauxite - Oxide ore
Answer:
(b) Copper pyrite Oxide ore
Question 5.
(a) Haematitc - Gravity separation process
(b) Copper pyrite - froth floatation process
(c) Bauxite - Leaching process
(a) pyrolusite - Magnetic separation process
Answer:
(b) Copper pyrite - froth floatation process
Question 6.
(a) Gold ore - Cyanide leaching
(b) Nickel ore - Ammonia leaching
(c) Aluminium ore - Alkali leaching

(d) Silver ore - Acid leaching
Answer:
(a) Silver ore - Acid leaching
Question 7.
(a) Aluminium - Design of aeroplane
(b) Zinc oxide - Cosmetics
(c) Zinc suiphide - X-ray screens
(d) Iron - Artifici al limb joints
Answer:
(d) Iron-Artificial limb joints
2 Mark Questions and Answers
VIII. Answer the following:
Question 1.

Define Metallurgy.
Answer:
The various steps involved in the extraction of metals from their ores as well as refining of crude metals are collectively known as metallurgy.
Question 2.
What are minerals?
Answer:
A naturally occurring substance obtained by mining which contains the metal in free state or in the form of compounds like oxides, sulphides etc... is called as mineral. Bauxite and clay are minerals of Aluminium.
Question 3.
What are ores?
Answer:
A mineral from which the metal can be extracted easily and economically are called ores. Bauxite is an ore of Aluminium.

Question 4.
What are all the steps involved in metallurgical process?
Answer:
The extraction of a metal from its ore consists the following metallurgical process.
1. Concentration of the ore
2. Extraction of crude metal
3. Refining of crude metal
Question 5.
What is Gangue?
Answer:
Generally, the ores are associated with nonmetallic impurities, rocky materials and siliceous matter which are collectively known as gangue.
Question 6.
Give the depressing agents used in the froth floatation process and why we use depressing agents in that process?
Answer:
Generally sodium cyanide and sodium carbonate are used as an depressing agents for froth floatation process. These reagents are used to selectively prevent other metal sulphides from coming to the froth. For example, when impurities such as $\mathrm{ZnS}$ is present in galena $(\mathrm{PbS})$, sodium cyanide $(\mathrm{NaCN})$ is added to depresses the flotation property of $\mathrm{ZnS}$ by forming a layer of zinc complex $\mathrm{Na}_2\left[\mathrm{Zn}(\mathrm{CN})_4\right]$ on the surface of zinc sulphide.
Question 7.
What are leaching process?
Answer:
This method is based on the solubility of the ore in a suitable solvent and the reactions in aqueous solution. In this method, the crushed ore is allowed to dissolve in a suitable solvent, the metal present in the ore is converted to its soluble salt or complex while the gangue remains insoluble. This process is also called chemical method.

Question 8.
Explain Cyanide leaching.
Answer:
In the concentration of gold ore, the crashed ore of gold is leached with aerated dilute solution of sodium cyanide. Gold is converted into a soluble cyanide complex. The gangue, aluminosilicate remains insoluble.
$
4 \mathrm{Au}(\mathrm{s})+8 \mathrm{CN}^{-}(\mathrm{aq})+\mathrm{O}_2(\mathrm{~g})+2 \mathrm{H}_2 \mathrm{O}(1) \rightarrow 4\left[\mathrm{Au}(\mathrm{CN})_2\right]^{-}(\mathrm{aq})+4 \mathrm{OH}^{-}(\mathrm{aq})
$
Question 9.
What is Cementation?
Answer:
Gold can be recovered by reacting the deoxygenated leached solution with zinc. In this process the gold is reduced to its elemental state (zero oxidation sate) and the process is called $\mathrm{Zn}(\mathrm{s})+2\left[\mathrm{Au}(\mathrm{CN})_2\right]^{-}(\mathrm{aq}) \rightarrow\left[\mathrm{Zn}(\mathrm{CN})_4\right]^{2-}(\mathrm{aq})+2 \mathrm{Au}(\mathrm{s})$
Question 10.
What is Ammonia leaching.
Answer:
When a crashed ore containing nickel, copper and cobalt is treated with aqueous ammonia . under suitable pressure, ammonia selectively leaches these metals by forming their soluble complexes viz. $\left[\mathrm{Ni}\left(\mathrm{NH}_3\right)_6\right]^{2+},\left[\mathrm{Cu}\left(\mathrm{NH}_3\right)_4\right]^{2+}$, and $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5 \mathrm{H}_2 \mathrm{O}\right]^{3+}$ respectively from the ore leaving behind the gangue, iron(III) oxides/hydroxides and aluminosilicate.
Question 11.
What is Acid leaching?
Answer:
Leaching of sulphide ores such as $\mathrm{ZnS}, \mathrm{PbS}$ etc,, can be done by treating them with hot aqueous sulphuric acid.
$
2 \mathrm{ZnS}(\mathrm{s})+2 \mathrm{H}_2 \mathrm{SO}_4(\mathrm{aq})+\mathrm{O}_2(\mathrm{~g}) \rightarrow 2 \mathrm{ZnSO}_4(\mathrm{aq})+2 \mathrm{~S}(\mathrm{~s})+\mathrm{H}_2 \mathrm{O}
$
In this process the insoluble sulphide is converted into soluble sulphate and elemental sulphur.
Question 12 .
What is roasting?
Answer:
The process of heating an ore (generally, sulphide are) is strongly below its melting point in the presence of an excess of air is called roasting.

Question 13.
Define Calcination.
Answer:
It is the process in which the concentrated ore is strongly heated in the absence of air. This
method can also be carried out with a limited supply of air.
$
\mathrm{CaCO}_3 \stackrel{\Delta}{\longrightarrow} \mathrm{CaO}+\mathrm{CO}_2 \uparrow
$
Question 14.
How will you manage sulphur dioxide produced during roasting process?
Answer:
The sulphur dioxide produced during roasting process is harmful to the environment. In modem metallurgical factories, this by product is trapped and converted into sulphuric acid to avoid air pollution.
Question 15 .
What is smelting?
Answer:
Smelting is a process of reducing the roasted metallic oxide to metal in molten condition. In this process, impurities are removed by the addition of flux as slag.
Question 16.
Explain Auto reduction.
Answer:
Simple roasting of some of the ores give the crude metal. In such cases, the use of reducing agents is not necessary. For example, mercury is obtained by roasting of its ore cinnabar $(\mathrm{HgS})$ $\mathrm{HgS}_{(\mathrm{s})}+\mathrm{O}_{2(\mathrm{~g})} \rightarrow \mathrm{Hg}(\mathrm{l})+\mathrm{SO}_2 \uparrow$
Question 17.
What is Ellingham diagram?
Answer:
The graphical representation of variation of the standard Gibbs free energy of reaction for the formation of various metal oxides with temperature is called Ellingham diagram.

Question 18.
$\mathrm{CO}$ is more stable at higher temperature. Why?
Answer:
In the Ellingham diagram, the formation of carbon monoxide is a straight line with negative slope. In this case $\Delta \mathrm{S}$ is positive as 2 moles of $\mathrm{CO}$ gas is formed by the consumption of one mole of oxygen. Hence, $\mathrm{CO}$ is more stable at higher temperature.
Question 19.
$\mathrm{Ag}_2(\mathrm{~g}) \mathrm{O}$ and $\mathrm{HgO}$ are unstable at moderate temperature and they will decompose on heating even in the absence of a reducing agent. Why?
Answer:
Ellingham diagram for the formation of $\mathrm{Ag}_{2(\mathrm{~g})} \mathrm{O}$ and $\mathrm{HgO}$ is at upper part of the diagram and their decomposition temperatures are 600 and $700 \mathrm{~K}$ respectively. It indicates that these oxides are unstable at moderate temperatures and will decompose on heating even in the absence of a reducing agent.
Question 20.
What is refining process?
Answer:
Generally the metal extracted from its ore contains some impurities such as unreacted oxide ore, other metals, nonmetal etc. Removal of such impurities associated with the isolated crude metal is called refining process.
Question 21.
List out the common refining methods.
Answer:
1. Distillation
2. Liquation
3. Electrolytic refining
4. Zone refining
5. Vapour phase method

Question 22.
Explain Distillation process with suitable example.
Answer:
This method is employed for low boiling volatile metals like zinc (boiling point $1180 \mathrm{~K}$ ) and mercury $(630 \mathrm{~K})$. In this method, the impure metal is heated to evaporate and the vapours are condensed to get pure metal.
Question 23.
Write the applications of copper.
Answer:
1. Copper is the first metal used by the humans and extended use of its alloy bronze resulted in a new era, Bronze age.
2. Copper is used for making coins and ornaments along with gold and other metals.
3. Copper and its alloys are used for making wires, water pipes and other electrical parts.
Question 24 .
Why aluminium cannot be extracted by reducing alumina with carbon?
Answer:
Alumina $\left(\mathrm{Al}_2 \mathrm{O}_3\right)$ cannot be reduced by using carbon because aluminum has more affinity for oxygen than carbon. Therefore, aluminium cannot be extracted by reducing alumina with carbon.
Question 25.
Write the names of two ores of copper.
Answer:
Main ores of copper are:
1. Copper pyrites $-\mathrm{CuFeS}_2$
2. Copper glance $-\mathrm{Cu}_2 \mathrm{~S}$
3. Malachite $-\mathrm{CuCO}_3 \cdot \mathrm{Cu}(\mathrm{OH})_2$
Question 26.
Explain the role of carbon monoxide in the purification of nickel?
Answer:
During the purification of Nickel by Mond's process, carbon monoxide (CO) is used to convert impure nickel to nickel carbonyl. Nickel carbonyl is an unstable compound. Heating to higher temperature decomposes it to give pure nickel.

Question 27.
$\mathrm{ZnO}$ can be reduced to the metal by heating with carbon but not $\mathrm{Cr}_2 \mathrm{O}_3$. Justify your answer.
Answer:
Carbon has more affinity for oxygen than zinc, whereas chromium has higher affinity for oxygen than zinc. Hence $\mathrm{ZnO}$ can be reduced to the metal by heating with carbon but not $\mathrm{Cr}_2 \mathrm{O}_3$.
Question 28.
Name the method used for the refining of
1. Nickel
2. Zirconium
Answer:
1. Mond's process
2. Van Arkel's method
Question 29.
Give one example for
1. Acidic flux
2. Basic flux
Answer:
1. Acidic flux: $\mathrm{SiO}_2$
2. Basic flux: $\mathrm{CaCO}_3, \mathrm{MgCO}_3$
Question 30 .
Why is the reduction of a metal oxide easier if the metal formed is in liquid state at the temperature of reduction?
Answer:
The entropy is higher if the metal is in liquid state than when it is in solid state. The value of entropy change $(\Delta \mathrm{S})$ of the reduction process is more on +ve side when the metal formed is in liquid state and the metal oxide being reduced is in solid state. Thus, the value of $\Delta \mathrm{G}^{\circ}$ becomes more on negative side and the reduction becomes easier.
3 Mark Questions and Answers
IX. Answer the following questions:

Question 1.
All ores are minerals, but all minerals are not ores. Explain.
Answer:
A naturally occurring substance obtained by mining which contains the metal in free state or in the form of compounds is called a mineral. In most of the minerals, the metal of interest is present only in small amounts and some of them contains a reasonable percentage of metal. Such minerals that contains a high percentage of metal, from which it can be extracted conveniently and economically are called ores. Hence all ores are minerals but all minerals are not ores.
Question 2.
Bauxite is an ore of aluminium while china clay is not. Why?
Answer:
Bauxite and china clay, both are minerals of aluminium. However, aluminium can be commercially extracted from bauxite while extraction from china clay is not a profitable one. Hence the mineral, bauxite is an ore of aluminium while china clay is not.
Question 3.
Explain Gravity separation process or Hydraulic washing process?
[OR]
How will you concentrate oxide ores?
[OR]
Explain the suitable method to concentrate hematite and tinstone ores.
Answer:
In this method, the ore having high specific gravity is separated from the gangue that has low specific gravity by simply washing with running water. Ore is crushed to a finely powdered form and treated with rapidly flowing current of water. During this process the lighter gangue particles are washed away by the running water. This method is generally applied to concentrate the native ore such as gold and oxide ores such as hematite $\left(\mathrm{Fe}_2 \mathrm{O}_3\right)$, tin stone $\left(\mathrm{SnO}_2\right)$ etc.
Question 4.
Write a notes on alkali leaching process?
Answer:
In this method, the ore is treated with aqueous alkali to form a soluble complex. For example, bauxite, an important ore of aluminium is heated with a solution of sodium hydroxide or sodium carbonate in the temperature range $470-520 \mathrm{~K}$ at $35 \mathrm{~atm}$ to form soluble sodium metaaluminate leaving behind the impurities, iron oxide and titanium oxide.
$
\mathrm{Al}_2 \mathrm{O}_3(\mathrm{~S})+2 \mathrm{NaOH}(\mathrm{aq})+3 \mathrm{H}_2 \mathrm{O}(\mathrm{l}) \rightarrow 2 \mathrm{Na}\left[\mathrm{Al}(\mathrm{OH})_4\right](\mathrm{aq})
$
The hot solution is decanted, cooled, and diluted. This solution is neutralised by passing $\mathrm{CO}_2$ gas, to the form hydrated $\mathrm{Al}_2 \mathrm{O}_2$ precipitate.
$
2 \mathrm{Na}\left[\mathrm{Al}(\mathrm{OH})_4\right](\mathrm{aq})+\mathrm{CO}_2(\mathrm{~g}) \rightarrow \mathrm{Al}_2 \mathrm{O}_3 \cdot \mathrm{xH}_2 \mathrm{O}(\mathrm{s})+2 \mathrm{NaHCO}_3(\mathrm{aq})
$

The precipitate is filtered off and heated around $1670 \mathrm{~K}$ to get pure alumina $\mathrm{Al}_2 \mathrm{O}_3$.
Question 5.
Complete the following reaction.
1. $\mathrm{ZnS}+\mathrm{O}_2 \underset{\rightarrow}{\rightarrow}$ ?
2. $\mathrm{P}_4+\mathrm{O}_2 \stackrel{\Delta}{\rightarrow}$ ?
3. $\mathrm{CaCO}_3 \stackrel{\Delta}{\rightarrow}$ ?
Answer:
1. $2 \mathrm{ZnS}+3 \mathrm{O}_2 \underset{\rightarrow}{\rightarrow} 2 \mathrm{ZnO}+2 \mathrm{SO}_2 \uparrow$
2. $\mathrm{P}_4+5 \mathrm{O}_2 \underset{\rightarrow}{\rightarrow} \mathrm{P}_4 \mathrm{O}_{10} \uparrow$
3. $\mathrm{CaCO}_3 \underset{\rightarrow}{\rightarrow} \mathrm{CaO}+\mathrm{CO}_2 \uparrow$

Question 6.
Explain Aluminothermic process.
Answer:
Metallic oxides such as $\mathrm{Cr}_2 \mathrm{O}_3$ can be reduced by an aluminothermic process. In this process, the metal oxide is mixed with aluminium powder and placed in a fire clay crucible. To initiate the reduction process, an ignition mixture (usually magneisium and barium peroxide) is used.
$
\mathrm{BaO}_2+\mathrm{Mg} \rightarrow \mathrm{BaO}+\mathrm{MgO}
$
During the above reaction a large amount of heat is evolved (temperature upto $2400^{\circ} \mathrm{C}$, is generated and the reaction enthalpy is $-852 \mathrm{~kJ} \mathrm{~mol}$ ) which facilitates the reduction of $\mathrm{Cr}_2 \mathrm{O}_3$ by aluminium power.
$
\mathrm{Cr}_2 \mathrm{O}_3+2 \mathrm{Al} \underset{\rightarrow}{\rightarrow} 2 \mathrm{Cr}+\mathrm{Al}_2 \mathrm{O}_3
$
Question 7.
Why aluminium can be used as a reducing agent for the reduction of chronic oxide?
Answer:
Ellingham diagram is used to predict thermodynamic feasibility of reduction of oxides of one metal by another metal. Any metal can reduce the oxides of other metals that are located above it in the diagram. For example, in the Ellingham diagram, for the fonnation of chromium oxide lies above that of the aluminium, meaning that $\mathrm{Al}_2 \mathrm{O}_3$, is more stable than $\mathrm{Cr}_2 \mathrm{O}_3$. Hence aluminium can be used as a reducing agent for the reduction of chromic oxide. However, it cannot be used to reduce the oxides of magnesium and calcium which occupy lower position than aluminium oxide.
Question 8.
Write notes on liquation.
Answer:
Liquation:
This method, is employed to remove the impurities with high melting points from metals having relatively low melting points such a stin( $\mathrm{Sb} ; \mathrm{mp}=904 \mathrm{~K})$, lead $(\mathrm{Pb} ; \mathrm{mp}=600 \mathrm{~K})$, mercury $(\mathrm{Hg} ; \mathrm{mp}=$ $234 \mathrm{~K})$, and bismuth $(\mathrm{Bi} ; \mathrm{mp}=545 \mathrm{~K})$. In this process, the crude metal is heated to form fusible liquid and allowed to flow on a sloping surface.
The impure metal is placed on sloping hearth of a reverberatory furnace and it is heated just above the melting point of the metal in the absence of air, the molten pure metal flows down and the impurities are left behind. The molten metal is collected and solidified.

Question 9.
Write the application of Iron ( $\mathrm{Fe})$.
Answer:
1. Iron is one of the most useful metals and its alloys are used everywhere including bridges, electricity pylons, bicycle chains, cutting tools and rifle barrels.
2. Cast iron is used to make pipes, valves and pumps stoves etc.
3. Magnets can be made of iron and its alloys and compounds.
4. An important alloy of iron is stainless steel, and it is very resistant to corrosion. It is used in architecture, bearings, cutlery, surgical instruments and jewellery. Nickel steel is used for making cables, automobiles and aeroplane parts. Chrome steels are used for manufacturing cutting tools and curshing machines
Question 10.
Mention the uses of Gold ( $\mathrm{Au})$.
Answer:
1. Gold, one of the expensive and precious metals. It is used for coinage, and has been used as standard for monetary systems in some countries.
2. It is used extensively in jewellery in its alloy form with copper. It is also used in electroplating to cover other metals with a thin layer of gold which are used in watches, artificial limb joints, cheap jewellery, dental fillings and electrical connectors.
3. Gold nanoparticles are also used for increasing the efficiency of solar cells and also used an catalysts.
Question 11.
The extraction of $\mathrm{Au}$ by leaching with $\mathrm{NaCN}$ involves both oxidation and reduction. Justify giving equation.
Answer:
- $4 \mathrm{Au}(\mathrm{s})+8 \mathrm{CN}^{-}(\mathrm{aq})+2 \mathrm{H}_2 \mathrm{O}_2(\mathrm{aq})+\mathrm{O}_2(\mathrm{~g}) \rightarrow 4\left[\mathrm{Au}(\mathrm{CN})_2\right]^{-}(\mathrm{aq})+4 \mathrm{OH}^{-}(\mathrm{aq})$
- $2\left[\mathrm{Au}(\mathrm{CN})_2\right]^{-}(\mathrm{aq})+\mathrm{Zn}(\mathrm{s}) \rightarrow 2 \mathrm{Au}(\mathrm{s})+\left[\mathrm{Zn}(\mathrm{CN})_4\right]^{-2}(\mathrm{aq})$
In the first reaction $\mathrm{Au}$ changes into $\mathrm{Au}^{+}$, i.e. its oxidation takes place. In the second reaction: $\mathrm{Au}^{+} \rightarrow \mathrm{Au}^{\circ}$
(i.e.) reduction takes place.

Question 12.
Account for the following facts:
1. The reduction of a metal oxide is easier if the metal formed is in liquid state at the temperature of reduction.
2. The reduction of $\mathrm{Cr}_2 \mathrm{O}_3$ with $\mathrm{Al}$ is thermodynamically feasible, yet it does not occur at room temperature.
3. Pine oil is used in froth floatation method.
Answer:
1. In liquid state entropy is higher than the solid form, this makes $\Delta_{\mathrm{f}} \mathrm{G}$ more negative.
2. By increasing the temperature, fraction of activated molecules increases, which helps in crossing over the energy barrier.
3. Pine oil enhances the non-wetting property of the ore particles and also acts as the froth collector.
Question 13.
Write the chemical reactions for purification of Zirconium by Van Arkel's process.
Answer:

5 Mark Questions and Answers
$X$. Answer the following questions:
Question 1.

Explain froth floatation process.
(Or)
How will you concentrate sulphide ores?
(Or)
Explain-the concentration of copper pyrites and galena ores.
Answer:
Froth flotation:
This method is commonly used to concentrate sulphide ores such as galena $(\mathrm{PbS})$, zinc blende $(\mathrm{ZnS})$ etc. In this method, the metallic ore particles which are preferentially wetted by oil can be separated from gangue. In this method, the crushed ore is suspended in water and mixed with frothing agent such as pine oil, eucalyptus oil etc. A small quantity of sodium ethyl xanthate which acts as a collector is also added. A froth is generated by blowing air through this mixture.
The collector molecules attach to the ore particle and make them water repellent. As a result, ore particles, wetted by the oil, rise to the surface along with the froth. The froth is skimmed off and dried to recover the concentrated ore. The gangue particles that are preferentially wetted by water settle at the bottom.
When a sulphide ore of a metal of interest contains other metal sulphides as impurities, depressing agents such as sodium cyanide, sodium carbonate etc are used to selectively prevent other metal sulphides from coming to the froth. For example, when impurities such as $\mathrm{ZnS}$ is present in galena $(\mathrm{PbS})$, sodium cyanide $(\mathrm{NaCN})$ is added to depresses the flotation property of $\mathrm{ZnS}$ by forming a layer of zine complex $\mathrm{Na}_2\left[\mathrm{Zn}(\mathrm{CN})_4\right]$ on the surface of zine sulphide.

Question 2.
Discuss the magnetic separation process.
(Or)
How will you separate magnetic ores from non-magnetic ores?
Answer:
Magnetic separation:
This method is applicable to ferromagnetic ores and it is based on the difference in the magnetic properties of the ore and the impurities. For example tin stone can be separated from the wolframite impurities which is magnetic. Similarly, ores such as chromite, pyrolusite having magnetic property can be removed from the non magnetic siliceous impurities.

The crushed ore is poured on to an electromagnetic separator consisting of a belt moving over two rollers of which one is magnetic. The magnetic part of the ore is attracted towards the magnet
and falls as a heap close to the magnetic region while the nonmagnetic part falls away from it as shown in the figure.

Question 3.
Write a note on thermodynamic principle of metallurgy.
Answer:
Thermodynamic principle of metallurgy:
The extraction of metals from their oxides can be carried out by using different reducing agents.
For example, consider the reduction of a metal oxide $\mathrm{M}_{\mathrm{x}} \mathrm{O}_{\mathrm{y}}$.
$$
\frac{2}{y} \mathrm{M}_{\mathrm{x}} \mathrm{O}_{\mathrm{y}}(\mathrm{s}) \rightarrow \frac{2 x}{y} \mathrm{M}(\mathrm{s})+\mathrm{O}_2(\mathrm{~g})
$$
The above reduction may be carried out with carbon. In this case, the reducing agent carbon may be oxidised to either $\mathrm{CO}$ or $\mathrm{CO}_2$.
- $\mathrm{C}+\mathrm{O}_2 \rightarrow \mathrm{CO}_{2(\mathrm{~g})}$
- $2 \mathrm{C}+\mathrm{O}_2 \rightarrow 2 \mathrm{CO}_{(\mathrm{g})}$

If carbon monoxide is used as a reducing agent, it is oxidised to $\mathrm{CO}_2$ as follows,
$
2 \mathrm{CO}+\mathrm{O}_2 \rightarrow 2 \mathrm{CO}_{2(\mathrm{~g})}
$
A suitable reducing agent is selected based on the thermodynamic considerations. We know that for a spontaneous reaction, the change in free energy (AG) should be negative. Therefore, thermodynamically, the reduction of metal oxide [equation (1)] with a given reducing agent [Equation (2), (3) or (4)] can occur if the free energy change for the coupled reaction. [Equations (1) \& (2), (1) \& (3) or (1) \& (4)] is negative. Hence, the reducing agent is selected in such a way that it provides a large negative $A G$ value for the coupled reaction.
Ellingham diagram:
The change in Gibbs free energy $(\Delta \mathrm{G})$ for a reaction is given by the expression. $\Delta \mathrm{G}=\Delta \mathrm{H}-\mathrm{T} \Delta \mathrm{S}$
where, $\Delta \mathrm{H}$ is the enthalpy change, $\mathrm{T}$ the temperature in kelvin and $\Delta \mathrm{S}$ the entropy change. For an equilibrium process, $\Delta \mathrm{G}^{\circ}$ can be calculated using the equilibrium constant by the following expression $\Delta \mathrm{G}^{\circ}=-\mathrm{RT} \ln K \mathrm{p}$
Harold Ellingham used the above relationship to calculate the $\Delta \mathrm{G}^{\circ}$ values at various temperatures for the reduction of metal oxides by treating the reduction as an equilibrium process. He has drawn a plot by considering the temperature in the $\mathrm{x}$-axis and the standard free energy change for the formation of metal oxide in $y$-axis. The resultant plot is a straight line with $\Delta \mathrm{S}$ as slope and $\Delta \mathrm{H}$ as y-intercept. The graphical representation of variation of the standard Gibbs free energy of reaction for the formation of various metal oxides with temperature is called Ellingham diagram.
Question 4.
Explain the observations from the Ellingham diagram.
Answer:
1. For most of the metal oxide formation, the slope is positive. It can be explained as follows. Oxygen gas is consumed during the formation of metal oxides which results in the decrease in randomness. Hence, $\Delta \mathrm{S}$ becomes negative and it makes the term, $\mathrm{T} \Delta \mathrm{S}$ positive in the straight line equation.
2. The graph for the formation of carbon monoxide is a straight line with negative slope. In this case $\Delta \mathrm{S}$ is positive as 2 moles of $\mathrm{CO}$ gas is formed by the consumption of one mole of oxygen gas. It indicates that $\mathrm{CO}$ is more stable at higher temperature.

3. As the temperature increases, generally $\Delta \mathrm{G}$ value for the formation of the metal oxide become less negative and becomes zero at a particular temperature. Below this temperature, $\Delta \mathrm{G}$ is negative and the oxide is stable and above this temperature $\Delta \mathrm{G}$ is positive. This general trend suggests that metal oxides become less stable at higher temperature and their decomposition becomes easier.
4. There is a sudden change in the slope at a particular temperature for some metal oxides like $\mathrm{MgO}, \mathrm{HgO}$. This is due to the phase transition (melting or evaporation).
Question 5.
Discuss.the applications of the Ellingham diagram:
Answer:
Ellingham diagram helps us to select a suitable reducing agent and appropriate temperature range for reduction. The reduction of a metal oxide to its metal can be considered as a competition between the element used for reduction and the metal to combine with oxygen.
If the metal oxide is more stable, then oxygen remains with the metal and if the oxide of element used for reduction is more stable, then the oxygen from the metal oxide combines with elements used for the reduction. From the Ellingham diagram, we can infer the relative stability of different metal oxides at a given temperature.
1. Ellingham diagram for the formation of $\mathrm{Ag}_2 \mathrm{O}$ and $\mathrm{HgO}$ is at upper part of the diagram and their decomposition temperatures are 600 and $700 \mathrm{~K}$ respectively. It indicates that these oxides are unstable at moderate temperatures and will decompose on heating even in the absence of a reducing agent.
2. Ellingham diagram is used to predict thermodynamic feasibility of reduction of oxides of one metal by another metal. Any metal can reduce the oxides of other metals that are located above it in the diagram. For example, in the Ellingham diagram, for the formation of chromium oxide lies above that of the aluminium, meaning that $\mathrm{Al}_2 \mathrm{O}_3$ is more stable than $\mathrm{Cr}_2 \mathrm{O}_3$. Hence aluminium can be used as a reducing agent for the reduction of chromic oxide. However, it cannot be used to reduce the oxides of magnesium and calcium which occupy lower position than aluminium oxide.

3. The carbon line cuts across the lines of many metal oxides and hence it can reduce all those metal oxides at sufficiently high temperature. Let us analyse the thermodynamically favourable conditions for the reduction of iron oxide by carbon. Ellingham diagram for the formation of $\mathrm{FeO}$ and $\mathrm{CO}$ intersects around $1000 \mathrm{~K}$.

Below this temperature the carbon line lies above the iron line which indicates that $\mathrm{FeO}$ is more stable than $\mathrm{CO}$ and hence at this temperature range, the reduction is not thermodynamically feasible. However, above $1000 \mathrm{~K}$ carbon line lies below the iron line and hence, we can use coke as reducing agent above this temperature. The following free energy calculation also confirm that the reduction is thermodynamically favoured.
From the Ellingham Diagram at $1500 \mathrm{~K}$ :
- $2 \mathrm{Fe}_{(\mathrm{s})}+\mathrm{O}_{2(\mathrm{~g})} \rightarrow 2 \mathrm{FeO}_{(\mathrm{g})}$
- $2 \mathrm{C}_{(\mathrm{s})}+\mathrm{O}_{2(\mathrm{~g})} \rightarrow 2 \mathrm{CO}_{(\mathrm{g})}$
- $\Delta \mathrm{G}_1=-350 \mathrm{~kJ} \mathrm{~mol}^{-1}$
- $\Delta \mathrm{G}_2=-480 \mathrm{~kJ} \mathrm{~mol}^{-1}$
Reverse the reaction (1)
- $2 \mathrm{FeO}_{(\mathrm{s})} \rightarrow 2 \mathrm{Fe}_{(\mathrm{s})}+\mathrm{O}_{2(\mathrm{~g})}$
- $-\Delta \mathrm{G}_1=+350 \mathrm{~kJ} \mathrm{~mol}^{-1}$
Now couple the reactions (2) and (3)
- $2 \mathrm{FeO}_{(\mathrm{s})}+2 \mathrm{C} 2 \mathrm{Fe}(1, \mathrm{~s})+2 \mathrm{CO}_{(\mathrm{g})}$
- $\Delta \mathrm{G}_3=-130 \mathrm{~kJ} \mathrm{~mol}^{-1}$
The standard free energy change for the reduction of one mole of $\mathrm{FeO}$ is: $\Delta \mathrm{G}_3 / 2=-65 \mathrm{~kJ} \mathrm{~mol}^{-1}$
Question 6.
Explain the method to purify Titanium metal.

[OR]
Explain Van-Arkel method for refining Titanium.
[OR]
How will you purify metals by using iodine?
Answer:
This method is based on the thermal decomposition of metal compounds which lead to the formation of pure metals. Titanium and zirconium can be purified using this method. For example, the impure titanium metal is heated in an evacuated vessel with iodine at a temperature of $550 \mathrm{~K}$ to form the volatile titanium tetra-iodide.( $\left.\mathrm{TiI}_4\right)$. The impurities are left behind, as they do not react with iodine.
$
\mathrm{Ti}_{(\mathrm{s})}+2 \mathrm{I}_{2(\mathrm{~s})} \rightarrow \mathrm{TiI}_4 \text { (vapour) }
$
The volatile titanium tetraiodide vapour is passed over a tungsten filament at a temperature around $1800 \mathrm{~K}$. The titanium tetraiodide is decomposed and pure titanium is deposited on the filament. The iodine is reused. $\mathrm{Til}_4$ (vapour) $\rightarrow \mathrm{Ti}_{(\mathrm{s})}+2 \mathrm{I}_{2(\mathrm{~s})}$
Question 7.
Mention the applications of Aluminium.
Answer:
Aluminium is the most abundant metal and is a good conductor of electricity and heat. It also resists corrosion. The following are some of its applications.
1. Many heat exchangers/sinks and our day to day cooking vessels are made of aluminium.
2. It is used as wraps (aluminium foils) and is used in packing materials for food items,
3. Aluminium is not very strong, However, its alloys with copper, manganese, magnesium and silicon are light weight and strong and they are used in design of aeroplanes and other forms of transport.
4. As Aluminium shows high resistance to corrosion, it is used in the design of chemical reactors, medical equipments,refrigeration units and gas pipelines.
5. Aluminium is a good electrical conductor and cheap, hence used in electrical overhead electric cables with steel core for strength.

Question 8.
Complete the following reactions,
1. $\mathrm{Cr}_2 \mathrm{O}_3+\mathrm{A} 1 \stackrel{\Delta}{\rightarrow}$ ?
2. $\mathrm{B}_2 \mathrm{O}_2+\mathrm{Na} \stackrel{\Delta}{\rightarrow}$ ?
3. $\mathrm{ThO}_2+\mathrm{Ca} \Delta$ ?
4. $\mathrm{Mn}_3 \mathrm{O}_4+\mathrm{C} \underset{\vec{\Delta}}{\rightarrow}$ ?
5. $\mathrm{Ag}_2 \mathrm{O}+\mathrm{H}_2 \underset{\rightarrow}{\rightarrow}$ ?
Answer:
1. $\mathrm{Cr}_2 \mathrm{O}_3+2 \mathrm{Al} \underset{\Delta}{\rightarrow} 2 \mathrm{Cr}+\mathrm{Al}_2 \mathrm{O}_3$
2. $\mathrm{B}_2 \mathrm{O}_3+6 \mathrm{Na} \underset{\Delta}{\rightarrow} 2 \mathrm{~B}+3 \mathrm{Na}_2 \mathrm{O}$
3. $\mathrm{ThO}_2+2 \mathrm{Ca} \stackrel{1250 \mathrm{~K}}{\longrightarrow} \mathrm{Th}+2 \mathrm{CaO}$
4. $\mathrm{Mn}_3 \mathrm{O}_4+4 \mathrm{C} \underset{\Delta}{\rightarrow} 3 \mathrm{Mn}+4 \mathrm{CO}$
5. $\mathrm{Ag}_2 \mathrm{O}+\mathrm{H}_2 \underset{\rightarrow}{\rightarrow} 2 \mathrm{Ag}+\mathrm{H}_2 \mathrm{O}$
Common Errors and its Rectifications
Common Errors:
1. In balancing inorganic reactions, they may struggle.
2. Ores formula they may forget.
3. In metallurgy, the steps are very important.
Rectifications:
1. Students are advised to balance first the negative charged atoms like oxygen, chlorine in the equation.
2. Simple way is to remember one oxide ore (or) one sulphide ore from which the metal is extracted.
3. Students should practice to write steps headings first along with explanation.