CBSE Class 12 Chemistry General Principles And Processes of Isolation of Elements Worksheet Set 02

Official Class 12 Chemistry Worksheets: Unit 6 General Principles and Processes of Isolation of Elements

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Chapter-wise Practice Material: Unit 6 General Principles and Processes of Isolation of Elements

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General Principles and Processes of Isolation of Elements
 
1. Out of C and CO, which is a better reducing agent at 673 K?
 
2. How is copper extracted with a low grade ore of it?
 
3. What is the role of zinc in extraction of Silver?
 
4. Describe the role of SiO2 in extraction of copper from copper matte and write the equation involved.
 
5. What is “copper matte”?
 
6. What are froth stabilizers? Give two examples
 
7. The graphite electrodes in the extraction of ‘aluminium’ by Hall-Heroult process need to be changed frequently. Why?
 
8. Describe how the following changes are brought out:
a) Pig iron into steel.
b) Zinc oxide into zinc metal.
 
9. Write the chemical reactions involved in the process of extraction of Gold. Explain the role of dilute NaCN and Zn in this process.
 
10. Differentiate between
a) Calcination and roasting
b) Electrolytic reduction and electrolytic refining
c) Flux and slag
 
11. Write the chemical reactions which take place in the following operations:
a) Electrolytic reduction of Al2O3.
b) Isolation of Zn from zinc blende.
c) Mond’s process for refining of Ni.
d) I2 in van Arkel process of refining
e) Cryolite in extraction of Aluminium
f) Dilute NaCN in extraction of silver
g) Collector in the froth floatation process
 
12. Describe the principle involved in:
a) Electrolytic refining of metals.
b) Zone refining of metals
c) Froth floatation process
d) Chromatography
e) Vapour phase refining
 
13. Give reasons:
a) Copper matte is put in silica lined convertor.
b) Cryolite is added to alumina during electrolytic reduction.
c) Pine oil is used in the froth floatation process
 
14. a) Name the method used for the refining of titanium.
b) What is the role of Zn in the extraction of silver?
c) Reduction of metal oxide to metal becomes easier if the metal obtained is in liquid state. Why?
 
15. Write down the reactions taking place in different zones of a blast furnace during extraction of iron. How is pig iron different from cast iron?
 
16. a) Name the impurities deposit as anode mud during electrolytic refining of copper.
b) What type of metal can be refined by liquation method.
c) Name the method for refining of metals which are used as semiconductors.
 
17. Copper can be extracted by hydrometallurgy but not zinc. Explain?
 
18. What is German silver? Write its use.
 
19. Explain the following:-
a) Zinc but not copper is used for recovery of Ag from the complex[Ag(CN)2]−.
b) Partial roasting of sulphide ore is done in the metallurgy of copper.
c) Extraction of Cu from pyrites is difficult than that from its oxide ore through reduction.
 
20. Describe the principles of extraction of Zinc from zinc blende.
 
Question. What percentage of carbon is found in wootz steel?
a) 2-2.5%
b) 1.0-1.9%
c) 3-4.5%
d) 0.5-1%

Answer: b

Question. Chromatographic method is based on the principle that
a) different components of a mixture are differently adsorbed on an adsorbent
b) same components of a mixture are differently adsorbed on an adsorbent
c) different components of a mixture are differently absorbed on an absorbent
d) None of the above

Answer: a

Question. If the sulphide ores of copper contains iron, then before heating, it is mixed with
a) silica
b) coke
c) carbon
d) coal

Answer: a

Question. Which of the following elements occurs in free state?
a) Iodine
b) Sulphur
c) Phosphorus
d) Magnesium

Answer: b

Question. Considering Ellingham diagram, which of the following metals can be used to reduce alumina?
a) Mg
b) Zn
c) Fe
d) Cu

Answer: a

Question. Which one of the following is a mineral of iron?
a) Malachite
b) Cassiterite
c) Pyrolusite
d) Magnetite

Answer: d

Question. An ore contains lead sulphide and zinc sulphide.
If froth floatation process is used, these can be separated
a) by using excess of pine oil
b) by using collection and froth stabilisers
c) by adjusting proportion of oil to water or using depressants
d) by using some suitable solvent in which either lead sulphide or zinc sulphide is soluble.

Answer: c

Question. In the extraction of copper from its sulphide ore, the metal finally obtained by the reduction of cuprous
oxide with
a) copper (I) sulphide (Cu2S) 
b) sulphur dioxide (SO2) 
c) iron sulphide (FeS)
d) carbon monoxide (CO)

Answer: a

Question. The ore which is concentrated by leaching process is
a) cuprite
b) argentite
c) sphalerite
d) haematite

Answer: b

Question. The froth stabilisers among the following are
a) pine oil
b) cresol
c) aniline
d) Both (b) and (c)

Answer: d

Question. Extraction of gold and silver involves leaching with CN− ion. Silver is later recovered by
a) liquation
b) distillation
c) zone refining
d) displacement with Zn

Answer: d

Question. Which of the following elements is present as the impurity to the maximum extent in the pig iron?
a) Carbon
b) Silicon
c) Phosphorus
d) Manganese

Answer: a

Question. The Mond process is used for the
a) purification of Ni
b) extraction of Mo
c) purification of Zr & Ti
d) extraction of Zn

Answer: a

Question. Which of the following is not true in the context of roasting process?
a) The ore is heated in a regular supply of air
b) The sulphide ores of copper are heated in reverberatory furnace
c) 2ZnS + 3O2 → 2ZnO+ 2SO2 is a reaction that involves roasting process
d) Mg, Al and Zn oxides can be reduced by roasting process

Answer: d

Question. Sulphide ores are common for which of the following metals.
a) Ag, Cu and Pb
b) Ag, Cu and Sn
c) Ag, Mg and Pb
d) Al, Cu and Pb

Answer: a

Question. The ore that contains both iron and copper is
a) malachite
b) azurite
c) dolomite
d) copper pyrites

Answer: d

Question. Roasting of sulphides gives the gas X as a by-product. This is a colourless gas with choking smell of burnt sulphur and causes great damage to respiratory organs as a result of acid rain.
Its aqueous solution is acidic acts as a reducing agent and its acid has never been isolated.
The gas X is
a) H2S 
b) SO2
c) CO2
d) SO3

Answer: b

Question. Given, ΔGf° (CuO) = −129.7 kJ mol−1,
                 ΔGf° (H2O) = − 237.2  kJ mol−1 and
                 ΔGf° (CO) = −137.2 kJ mol−1
The better reducing agent for the reduction of CuO is
a) H2
b) CO
c) C
d) Any of these

Answer: a

Question. Froth floatation process for the concentration of ores is an illustration of the practical application of
a) absorption
b) adsorption
c) sedimentation
d) coagulation

Answer: b

Question. In the graph of ΔrG° vs T for the formation of oxides,
a) Cu2O  line is almost at the top
b) lines (C, CO) and (C, CO2)  are at much higher positions in the graph
c) Both (a) and (b)
d) Neither (a) nor (b)

Answer: a

Question. The reducing agent used to reduce iron oxide in blast furnace is
a) silica
b) CO
c) C
d) lime

Answer: b

Question. Silica is added to the copper pyrites ore, when taken in reverberatory furnace for extraction of Cu.
This is because
a) it removes the impurity of iron oxide as slag
b) it reacts with Cu2 O  to form slag
c) it reduces Cu2 O  to Cu
d) it helps in separation of Cu from Fe

Answer: a

Question. Auto-reduction is not involved in the extraction of
a) copper
b) mercury
c) lead
d) aluminium

Answer: d

Question. In electrolytic refining method,
a) the impure metal is made to act as anode
b) a strip of the pure metal is used as cathode
c) anode and cathode are kept in a suitable electrolytic bath containing soluble salt of the same metal
d) All the above are true

Answer: d

Question. Stainless steel is rust proof because
a) an oxide layer of chromium protects it.
b) a stoichiometric compound is formed.
c) interstitial compound is formed between Cr and Fe.

Answer: b

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Download CBSE Practice Material: Class 12 Chemistry Unit 6 General Principles and Processes of Isolation of Elements

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