NCERT Exemplar solutions for Chemistry [English] Class 12 chapter 6 - General Principle and Processes of Isolation of Elements [Latest edition]

In the extraction of chlorine by electrolysis of brine ______.

When copper ore is mixed with silica, in a reverberatory furnace copper matte is produced. The copper matte contains ______.

Which of the following reactions is an example of autoreduction?

A number of elements are available in earth’s crust but most abundant elements are ______.

Zone refining is based on the principle that ______.

In the extraction of copper from its sulphide ore, the metal is formed by the reduction of \[\ce{Cu2O}\] with ______.

Brine is electrolysed by using inert electrodes. The reaction at anode is ______.

In the metallurgy of aluminium ______.

Electrolytic refining is used to purify which of the following metals?

Extraction of gold and silver involves leaching the metal with CN^– ion. The metal is recovered by ______.

Choose the correct option of temperature at which carbon reduces \[\ce{FeO}\] to iron and produces \[\ce{CO}\].

Below point ‘A’ \[\ce{FeO}\] can ______.

For the reduction of \[\ce{FeO}\] at the temperature corresponding to point D, which of the following statements is correct?

At the temperature corresponding to which of the points in figure, FeO will be reduced to Fe by coupling the reaction \[\ce{2FeO -> 2Fe + O2}\] with all of the following reactions?

(a) \[\ce{C + O2 -> CO2}\]

(b) \[\ce{2C + O2 -> 2CO}\]

(c) \[\ce{2CO + O2 -> 2CO2}\]

(i) Point A

(ii) Point B

(iii) Point D

(iv) Point E

Which of the following options are correct?

(i) Cast iron is obtained by remelting pig iron with scrap iron and coke using hot air blast.

(ii) In extraction of silver, silver is extracted as cationic complex.

(iii) Nickel is purified by zone refining.

(iv) Zr and Ti are purified by van Arkel method.

In the extraction of aluminium by Hall-Heroult process, purified \[\ce{Al2O3}\] is mixed with \[\ce{CaF2}\] to:

(i) lower the melting point of \[\ce{Al2O3}\].

(ii) increase the conductivity of molten mixture.

(iii) reduce \[\ce{Al^{3+}}\] into \[\ce{Al(s)}\].

(iv) acts as catalyst.

Which of the following statements is correct about the role of substances added in the froth floation process?

(i) Collectors enhance the non-wettability of the mineral particles.

(ii) Collectors enhance the wettability of gangue particles.

(iii) By using depressants in the process two sulphide ores can be separated.

(iv) Froth stabilisers decrease wettability of gangue.

In the Froth Floatation process, zinc sulphide and lead sulphide can be separated by:

(i) using collectors.

(ii) adjusting the proportion of oil to water.

(iii) using depressant.

(iv) using froth stabilisers.

Common impurities present in bauxite are:

(i) \[\ce{CuO}\]

(ii) \[\ce{ZnO}\]

(iii) \[\ce{Fe2O3}\]

(iv) \[\ce{SiO2}\] 

Which of the following ores are concentrated by froth floation?

(i) Haematite

(ii) Galena

(iii) Copper pyrites

(iv) Magnetite

Which of the following reactions occur during calcination?

(i) \[\ce{CaCo3 -> CaO + CO2}\]

(ii) \[\ce{2FeS2 + 11/2 O2 -> Fe2O3 + 4SO2}\] 

(iii) \[\ce{Al2O3. {x}H2O -> Al2O3 + {x}H2O}\]

(iv)  \[\ce{ZnS + 3/2 O2 -> ZnO + SO2}\]

For the metallurgical process of which of the ores calcined ore can be reduced by carbon?

(i) Haematite

(ii) Calamine

(iii) Iron pyrites

(iv) Sphalerite

The main reactions occurring in blast furnace during extraction of iron from haematite are:

(i) \[\ce{Fe2O3 + 3CO -> 2Fe + 3CO2}\]

(ii) \[\ce{FeO + SiO2 -> FeSiO3}\] 

(iii) \[\ce{Fe2O3 + 3C -> 2Fe + 3CO}\]

(iv) \[\ce{CaO + SiO2 -> CaSiO3}\]

In which of the following method of purification, metal is converted to its volatile compound which is decomposed to give pure metal?

(i) Heating with stream of carbon monoxide.

(ii) Heating with iodine.

(iii) Liquation.

(iv) Distillation.

Which of the following statements are correct?

(i) A depressant prevents certain type of particle to come to the froth.

(ii) Copper matte contains \[\ce{Cu2S}\] and \[\ce{ZnS}\].

(iii) The solidified copper obtained from reverberatory furnace has blistered appearance due to evolution of \[\ce{SO2}\] during the extraction.

(iv) Zinc can be extracted by self-reduction.

In the extraction of chlorine from brine:

(i) ∆G^Θ for the overall reaction is negative.

(ii) ∆G^Θ for the overall reaction is positive.

(iii) E^Θ for overall reaction has negative value.

(iv) E^Θ for overall reaction has positive value.

Why is an external emf of more than 2.2 V required for the extraction of \[\ce{Cl2}\] from brine?

At temperatures above 1073 K coke can be used to reduce \[\ce{FeO}\] to \[\ce{Fe}\]. How can you justify this reduction with Ellingham diagram?

Wrought iron is the purest form of iron. Write a reaction used for the preparation of wrought iron from cast iron. How can the impurities of sulphur, silicon and phosphorus be removed from cast iron?

How is copper extracted from low grade copper ores?

Write two basic requirements for refining of a metal by Mond process and by Van Arkel Method.

Although carbon and hydrogen are better reducing agents but they are not used to reduce metallic oxides at high temperatures. Why?

How do we separate two sulphide ores by Froth Floatation Method? Explain with an example.

The purest form of iron is prepared by oxidising impurities from cast iron in a reverberatory furnace. Which iron ore is used to line the furnace? Explain by giving reaction.

The mixture of compounds A and B is passed through a column of \[\ce{Al2O3}\] by using alcohol as eluant. Compound A is eluted in preference to compound B. Which of the compounds A or B, is more readily adsorbed on the column?

Why is sulphide ore of copper heated in a furnace after mixing with silica?

Why are sulphide ores converted to oxide before reduction?

Which method is used for refining Zr and Ti? Explain with equation.

What should be the considerations during the extraction of metals by electrochemical method?

What is the role of flux in metallurgical processes?

How are metals used as semiconductors refined? What is the principle of the method used?

Write down the reactions taking place in Blast furnace related to the metallurgy of iron in the temperature range 500-800 K.

Give two requirements for vapour phase refining.

Write the chemical reactions involved in the extraction of gold by cyanide process. Also give the role of zinc in the extraction.

Match the items of Column I with items of Column II and assign the correct code:

Match the items of Column I with the items of Column II and assign the correct code:

Match items of Column I with the items of Column II and assign the correct code:

Match items of Column I with the items of Column II and assign the correct code:

Match the items of Column I with items of Column II and assign the correct code:

Assertion: Nickel can be purified by Mond process.

Reason: \[\ce{Ni(CO)4}\] is a volatile compound which decomposes at 460 K to give pure Ni.

Assertion: Zirconium can be purificed by Van Arkel method.

Reason: ZrI₄ is volatile and decomposes at 1800 K.

Assertion: Sulphide ores are concentrated by Froth Flotation method.

Reason: Cresols stabilise the froth in Froth Flotation method.

Assertion: Zone refining method is very useful for producing semiconductors.

Reason: Semiconductors are of high purity.

Assertion: Hydrometallurgy involves dissolving the ore in a suitable reagent followed by precipitation by a more electropositive metal.

Reason: Copper is extracted by hydrometallurgy.

Explain the following:

\[\ce{CO2}\] is a better reducing agent below 710 K whereas \[\ce{CO}\] is a better reducing agent above 710 K.

Explain the following:

Generally sulphide ores are converted into oxides before reduction.

Explain the following:

Silica is added to the sulphide ore of copper in the reverberatory furnace.

Explain the following:

Carbon and hydrogen are not used as reducing agents at high temperatures.

Explain the following:

Vapour phase refining method is used for the purification of Ti.