CBSE Class 12 Chemistry Revision Notes Chapter 6

Chemistry Class 12 Chapter 6 Notes

The topic of general principles and processes of element isolation is an important chapter in Inorganic Chemistry.This is a chapter that includes practical applications too. The CBSE Class 12 Chemistry Chapter 6 Notes provide a detailed summary of the chapter General Principles and Processes of Elements Isolation. 

Isolation of Elements in Chemistry Class 12 Chapter 6 Notes cover topics such as metal occurrence, ore concentration, crude metal extraction, the Ellingham diagram, iron extraction, refining, and so on.Class 11 and 12 have a comprehensive science curriculum, and many students find chemistry to be a difficult subject to learn.The CBSE Class 12 Chemistry Chapter 6 Notes help students learn the chapter in simple, easy to understand language, allowing them to learn the entire syllabus of the chapter thoroughly.

Chemistry Class 12 Chapter 6 Notes – Introduction

The principles and processes of isolation of elements in Chapter 6 Chemistry Class 12 Notes introduce students to various metals and their principles. Moreover, you will study how the isolation of elements takes place. There are around 91 metals that we know. The metals found in large amounts are only silver, copper, platinum, and gold. However, to obtain other pure metals, we require two Chemistry principles. In other words, these principles are known as “extraction” and “isolation.”

CBSE Class 12 Chemistry Chapter 6 Notes covers the Principles and Processes of Elements Isolation.In this chapter, students will learn various terminologies such as concentration, calcination, roasting, refining, etc. In addition, they will understand the methodologies of oxidation and reduction  used within the extraction procedures. With Class 12 Chemistry Chapter 6 Notes, students will easily be able to apply the thermodynamic concepts to the extraction of Aluminium, Copper, Zinc, etc. Moreover, they will understand why CO is a reducing agent at some specific temperatures. Class 12 Chemistry Chapter 6 Notes will help you understand several chemical processes associated with metallurgy.

Keeping in mind the growing curiosity of students, Extramarks has curated CBSE solutions, such as Class 12 Chemistry Chapter 6 Notes, to aid students in understanding various concepts detailed in the chapter. Students will get access to the CBSE Class 12 Chemistry Chapter 6 study materials on the Extramarks website once they register on the website.

Key Topics Covered in Class 12 Chemistry Chapter 6 Notes

Introduction:

The first section under Class 12 Chemistry Chapter 6 Notes is an introduction to metals. Metals are essential for various purposes. Thus, extracting them from the mineral resource in a commercially feasible way is necessary. 

Ore is natural rock or sediment that contains minerals, typically containing metals, that can be mined, and treated. These minerals from which metal is extracted are known as ores. Usually, the ores contain impurities that can be removed to a specific limit in the concentration steps. After this step, ores are chemically treated to obtain metals. 

With the help of reducing agents such as CO, carbon, etc., the metal compound is reduced to metal. The metal oxide then reacts with a reducing agent, resulting in:

• The oxide reduces to metal.
• Oxidation of reducing agents occurs.

As defined in the CBSE solutions Class 12 Chemistry Chapter 6, the isolation of elements aims to teach the students different extraction processes of metals from ores. Some metals, such as noble metals like gold, silver, platinum, etc., are present in their original metallic state. 

Note:

Metallurgy is the branch of science that deals with extracting metals from ores that are naturally available in the environment.

All of the elements, especially metals, are combined with other elements, and these are called minerals. An element may combine with various other elements to make different minerals, but only a few of them are possible sources of that metal. Such sources are known as ores.Such sources are known as Ores. Other than the Class 12 Chemistry Chapter 6 Notes, students are recommended to refer to various study materials such as NCERT Solutions and CBSE Revision Notes for a more detailed explanation, all available at the Extramarks website.

Occurrence of Metals:

The earth’s crust is the source of several elements. Out of these elements, 70% are metals. Aluminium is the most abundant metal in the earth’s crust, and iron comes in second. The percentages of various elements in the earth’s crust are O-49%, Si-26%, Al-7.5%, Fe-4.2%, Ca-3.2%, Na-2.4%, K-2.3%, Mg-2.3%, and H-l%

Metals occur in two ways in nature:

• In native state

• In a combined state, they depend upon their chemical reactivities.

Native State: 

Elements with low chemical reactivity of noble metals with the least electropositive character are not attacked by oxygen, moisture, and CO2. These elements, hence, occur in the free state or the native state. For example, Au, Ag, Pt, S, O, N, inert gases, etc.

Combined State: 

Highly reactive elements such as F, Cl, Na, K, etc., occur in their natural combined form as compounds such as oxides, carbonates, sulphides, halides, etc. Hydrogen is the only non-metal that exists only in oxidised form. Extraction and isolation of metals:

Under this section of Class 12 Chemistry Chapter 6, students learn the technique of extracting metal ores buried deep underground, known as Mining. The metal ores are available in the earth’s crust in varied abundance. The extraction of metals from ores allows us to use the minerals in the ground! The ores are very dissimilar from the finished metals in buildings and bridges. Simply Ores consist of the desired metal compound, Gangue’s impurities, and earthly substances. 

Metal extraction and isolation occur in several significant steps:

•       The concentration of Ore.
•       Isolation of metal from concentrated ore.
•       Purification of the metal.

The principles of the ores of aluminium, iron, copper, and zinc have been given below:

a)Aluminium:

•       Bauxite AlOx(OH)3-2x [here 0 < x < 1]

•       Kaolinite (a form of clay) [Al2 (OH)4 Si2O5]

b)Iron:

•       Haematite Fe2O3

•       Magnetite Fe3O4

•       Siderite FeCO3

•       Iron pyrites FeS2

c)Copper:

•       Copper pyrites CuFeS2

•       Malachite CuCO3.Cu(OH)2
•       Cuprite Cu2O

•       Copper glance Cu2S

d)Zinc:

•       Zinc blende/Sphalerite ZnS

•       Calamine             ZnCO3

•       Zincite ZnO

The concentration of Ore:

The first step is to remove the impurities from the ore, which does notinvolve any chemical process. It depends on the difference between the physical properties of the metal and the unwanted particles.

Following are the physical processes involved:

1. Hydraulic Washing

1. Magnetic Separation

1. Froth Flotation Method
2. Leaching

Isolation of metal from its concentrated ores:

This method involves getting impure metal from its concentrated ore. It is a chemical process.

Below are the processes involved:

1. Conversion of oxide (Calcination & Roasting) and reduction to form metal.
2. Electrochemical Process.
3. Oxidation-reduction.

Purification of the metals: 

It involves various refining techniques to purify metals.

Following are the processes involved:

1. Distillation
2. Liquation
3. Electrolysis
4. Zone refining
5. Vapour phase refining
6. Chromatographic methods

More information on The Concentration of Ores: 

• Benefaction:

Removal of the not needed materials (e.g., sand, clays, etc.) from ore is called concentration, dressing, or benefaction. It involves various steps, and the selection of these steps is based upon the differences in physical properties of the compound of the metal present and which gangue particles are there.

• Hydraulic Washing: 

This process is based on the differences in gravities of the ore and the gangue particles. Removing lighter earthy impurities from the heavier ore particles by washing with water is known as levigation. The lighter impurities are washed away. This process is commonly used for oxide ores such as haematite, tinstone, and native ores of gold (Au) and silver (Ag).

• Magnetic Separation: 

This process is based on differences in the magnetic properties of the ore components. If a magnetic field can attract either ore or gangue (one of these two), then such separations are carried out. For example, Fe ores. The ground ore consists of a conveyor belt that passes over a magnetic roller.

• Froth Flotation Method:

This method removes gangue from sulphide ores. In this method, a suspension of the powdered ore is made with water. This process depends on the preferential wetting of ore particles by oil and gangue by water. In conclusion, the ore particles become light and rise to the top in the form of froth, while the gangue particles become heavy and settle down. Hence, adsorption is involved in this method. 

• Process of Froth Flotation Method:

It consists of collectors such as pine oils, fatty acids, xanthates, etc. that will increase the non-wettability of the mineral particles. It also contains froth stabilisers like cresols and anilines.In conclusion, it stabilises the froth.

• The mineral particles become wet by fatty oils, while the gangue particles become wet by water (H2O). A rotating paddle churns the mixture and draws air into it. As a result, froth is established, giving out the mineral particles. The froth is light and is skimmed off. It is then dried for the renewal of the ore particles.
• Mostly, it is possible to separate two sulphide ores by adjusting the proportion of oil to water or by using Depressants. 

For Example: In the case of an ore containing zinc sulphide(ZnS) and lead sulphide (PbS), the depressant used is sodium cyanide (NaCN). It selectively stops ZnS from coming to the froth but allows PbS to come with the froth. 

• Leaching:

Leaching is often applied if ore is soluble in some suitable solvent. The following Examples explain the procedure of leaching.

Leaching of alumina from bauxite: The primary  ore of aluminium, bauxite, usually consists of SiO2, iron oxides( FeO), and titanium oxide (TiO2) impurities. Concentration is achieved by digesting powdered Ore combined with a concentrated solution of sodium hydroxide( NaOH) at (473 to 523 K) and (35 – 36 bar pressure). In this step, Al2O3 is leached out as sodium aluminate (and SiO2 as sodium silicate), leaving the impurities behind.

  Al2O3(s) + 2NaOH (aq) + 3H2O (l)  →  2Na [Al (OH) 4] ( aq)

Aluminate solution is neutralised by passing CO2 gas, and hydrated Al2O3 is precipitated. At this step, the solution is seeded with freshly developed samples of hydrated Al2O3, which induces precipitation.

Here, 2Na [Al (OH)4] (aq) + CO2 (g)  →  Al2O3. x H2O(s) + 2NaHCO3 (aq)

Generally, the sodium silicate remains in the solution, and the hydrated alumina is filtered, dried, and heated to give back pure aluminium oxide, Al2O3:

Al2O3.xH2O(s)   →  Al2O3(s) + xH2O(g) (Temperature at 1470K)

Other Examples: In the metallurgy of silver and gold, the respective metals are leached with a dilute solution of NaCN or KCN in the presence of air (for O2). From there, the metal is obtained later by replacement.

4M+8CN–(aq)+2H2O(aq)+O2(g)→4[M(CN)2]–(aq)+4OH–(M is Ag / Au)

2[M(CN)2]–] + Zn(s)  →  [Zn (CN) 4]2-(aq) + 2M(s)

Some important terms:

1. a) Matrix or Gangue: Minerals are always associated with earthy impurities known as matrix or gangue.
2. b) Flux: It is a substance used to decrease the melting point of an ore or a substance used to react with impurities to form slag.

• i) Acidic flux: It converts basic impurities into slag. E.g., SiO2 is used in the metallurgy of copper to remove FeO as FeSiO3(slag). Other acidic fluxes are B2O3, P4O10 etc.
• ii) Basic flux: It converts acidic impurities to slag. For, e.g. CaO is used in the metallurgy of iron to remove SiO2 as CaSiO3 (slag). Other primary fluxes are CaCO3, MgCO3, MgO etc.

1. c) Slag: The low fusible substance produced by the reaction of flux with impurities during the extraction of metals is known as slag. The process is called a slagging operation.
2. d) Alloy: It is a homogenous mixture of a metal with one or more elements that may be metals or non-metals.
3. e) Metallurgy: The complete scientific and technological process employed to extract a metal from its ore is called metallurgy.

Extraction of Crude Metals from Concentrated Ore:

Concentrated ore is usually changed into oxide before reduction, as oxides are easier to reduce.

Hence, the isolation of crude metal from concentrated ore involves two significant steps:

1. Conversion to oxide.
2. Reduction of the oxides to metal.

Conversion to Oxide:

1. a) Calcination: 

It converts ores into oxides by rapidly heating them below their melting points in the presence of a limited supply of air or in the absence of air.

During calcination, volatile impurities, organic matter, and moisture are eliminated.

Fe2O3 x H2O → Fe2 O3 (s) + x H2O (g)   in the presence of heat

ZnCO3 (s)       → ZnO(s) + CO2 (g)

1. b) Roasting: 

In the roasting process, ore is heated in a furnace with a regular supply of air at a temperature below the melting point of the metal. This process is commonly applied for sulphide ores and is carried out in blast furnaces or reverberatory furnaces. Roasting helps to eliminate non-metallic impurities and moisture.

Some of the chemical reactions involving sulphide ores are shown below:

             2ZnS + 3O2  → 2ZnO + 2SO2

             2PbS + 3O2  → 2PbO + 2SO2

            2Cu2S + 3O2  → 2Cu2O + 2SO2

When Ore contains iron, it is combined with silica before heating. FeO Iron oxide ‘slags of’ as iron silicate and copper are produced in the form of copper matte that contains Cu2S and FeS.

FeO + SiO2 → FeSiO3 (Slag)

Definition of Slag: 

‘flux’ is added during metallurgy, which combines with ‘gangue’ to create ‘slag’. Slag separates from ore more easily than gangue.The removal of gangue is made easier in this manner.

Reduction of the Oxides to Metal:

The roasted or calcined ore is then converted into free metal by reduction. The reduction method is based on the activity of metal.

• Metals that are low in the activity series (like Cu, Ag, and Au) are obtained by heating their compounds in the air: 

Metals in the middle of the activity series (like Fe. Zn, Ni, Sn) are obtained by heating their oxides with carbon. In contrast, the electrolytic reduction process obtains metals that are very abundant in the activity series (like sodium, K, Ca, Mg, and Al).

• Using the concepts of thermodynamics will support us in knowing the metallurgical transformations.

Gibbs Free Energy:

As per the definition compiled in CBSE solutions Class 12 Chemistry Chapter 6, Gibbs free energy, also called the Gibbs function, Gibbs energy, or free enthalpy, is a quantity used to estimate the maximum amount of work done in a thermodynamic system when the temperature and pressure are kept constant. The symbol’ G’ represents Gibbs free energy, and the value is expressed in Joules or Kilojoules. It can be defined as the maximum amount of work extracted from a closed system.

Gibbs free energy is equal to the system’s enthalpy minus the product of the temperature and entropy. 

The equation is shown as follows:

G = H – TS

Here,

G = Gibbs free energy

H = enthalpy

T = temperature

S = entropy

OR

G = U + PV – TS

Here,

 U = internal energy(unit is joule)

 P = pressure ( pascal)

 V = volume ( m3)

 T = temperature (kelvin)

 S = entropy (kelvin)

Variations of the Equation: 

Gibbs free energy is a state function. Therefore, it is not dependent on the path. A change in Gibbs free energy results in a change in enthalpy less the product of the system’s temperature and entropy.

ΔG = ΔH – Δ(TS)

If the reaction happens under constant temperature ΔT=O

ΔG = ΔH – TΔS

This equation is known as the Gibbs-Helmholtz equation. 

ΔG > 0; the reaction is non-spontaneous as well as endergonic.

ΔG < 0; the reaction is spontaneous as well as exergonic.

ΔG = 0; the reaction is at equilibrium.

 The spontaneity of a process in the Gibbs equation implies that we can directly conclude the spontaneity of the reaction due to enthalpy and entropy values.

The system enthalpy is negative if the reaction is exothermic, making Gibbs’s free energy negative. So we can say that all exothermic reactions are spontaneous.

Spontaneity can only be suggested if a reaction can occur, not necessarily if a reaction will occur. 

For example, the conversion of diamond to graphite is a spontaneous process at STP,  but it is a slow step. It will take so many years for the transformation to occur. 

Gibbs Energy in Chemistry:

Students learn about Gibbs energy in CBSE and with the help of Class 12 Chemistry Chapter 6 Notes.In the energetics of processes for systems at constant temperature and pressure, the appropriate quantity is Gibbs free energy. 

 For a spontaneous process at constant temperature and pressure, the Gibbs free energy has the advantage of decreasing. Under these conditions, Gibbs free energy decrease equals the maximum amount of energy available for work. Whether it increases or decreases for some transition, the change in Gibbs free energy represents the bare minimum of work.

The transformation of a system from one stage to another, at constant temperature and pressure, is spontaneous if Gibbs free energy decreases. 

If the transformation’s Gibbs free energy is unchanged, the two states are in equilibrium. Gibbs energy is sometimes called the thermodynamic potential at constant pressure to specify its analogy with the potential energy of the mechanical system, which also has a minimum value under equilibrium conditions.

Ellingham diagram:

These diagrams are plots of the change in Gibbs free energy in forming oxides of elements vs. temperature. It gives a good concept for choosing a reducing agent for oxide reduction. These diagrams help determine whether a thermal reduction of ores is feasible. Gibbs free energy change must be negative at a particular temperature for a reaction to be possible. These diagrams have the drawback of not taking the kinetics of reduction into account, which means the reduction rate cannot be predicted.

Blast Furnace:                          

In the blast furnace, the reduction of iron oxides occurs at various temperature ranges. A hot air balloon is blown from the bottom of the furnace, and coke is burned to get the temperature up to about 2200K in the lower portion itself. Therefore, the burning of coke supplies most of the heat required.

In the upper part, the temperature is lower, and the iron oxides (Fe2O3 and Fe3O4) coming from the top are reduced in steps to FeO. Thus, the reduction reactions in the lower and higher temperature ranges depend on the corresponding intersection points in the ΔrG(-) vs T plots.

Following are the reactions that are taking place:

At 500 – 800 K (minimum temperature range in the blast furnace)-

3 Fe2O3 + CO yields→ 2 Fe3O4+CO2

Fe3O4 + 4 CO yields→ 3 Fe+4 CO2

Fe2O3 + CO yields→ 2 FeO+ CO2

The maximum temperature range in the blast furnace ( 900 K- 1500 K)-

C + CO2 → 2 CO

FeO + CO → Fe + CO2

Limestone decomposes to CaO and CO2

CaCO3 → CaO + CO2

Calcium silicate is formed if silica (impurity) interacts with calcium oxide (CaO) to create slag. It floats on top of molten Fe, preventing Fe oxidation.

CaO + SiO2 → CaSiO3

Products created in Blast Furnace:

Limestone is also decomposed to calcium oxide (CaO), which eliminates the silicate impurity in ore and acts as slag. Slag is in a molten state and separates from iron.

Pig Iron: The iron obtained from the blast furnace contains about 4% carbon and other impurities. This iron is called pig iron.

Cast iron: This iron varies from pig iron and is made by melting pig iron with scrap iron and coke using a hot air blast. It has a slightly lower carbon content (about 3%) and is extremely tough and brittle.

Wrought iron: Also known as malleable iron, is the purest form of commercial iron and is developed from cast iron by oxidising impurities in a reverberatory furnace lined with haematite.

This haematite oxidises into carbon to (CO) carbon monoxide:

Fe2O3 + 3 C → 2 Fe + 3 CO

Limestone is mixed as a flux, and sulphur, silicon, and phosphorus are oxidised and transferred into the slag. The metal is eliminated and freed from the slag by passing through rollers.

Applications:

Extraction of iron from its oxide:

The reduction of oxides occurs in various zones of the blast furnace.

C + ½ O2 yields→ CO

FeO + CO yields→ Fe(s/l) + CO2

Pig iron is the iron produced in a blast furnace. It is made of impure iron and contains 4% carbon and tiny amounts of S, P, Si, and Mn. It may be moulded into a wide range of shapes. Cast iron is prepared by melting pig iron, scrap iron, and coke with a hot air blast. It has a carbon content of approximately 3%. It is exceedingly brittle and rigid. Malleable iron, or wrought iron, is the purest iron available for commercial use. It’s also referred to as malleable iron. Pig iron is oxidatively refined in a reverberatory furnace lined with haematite, converting carbon to carbon monoxide.

Fe2O3 +3C →2Fe +3CO

Extraction of Copper from Cuprous Oxide (Cu [I] oxide):

Most ores are sulphide, and several may also consist of iron. The sulphide ores are roasted or smelted to give oxides:

2Cu2S + 3O2 → 2Cu2O + 2SO2

The oxide created is easily reduced to metallic copper using coke:

             Cu2O + C → 2Cu + CO

In the actual method, Ore is heated in a reverberatory furnace after combined with silica. In the furnace, iron oxide, iron silicate and copper are produced in the form of copper matte. This consists of Cu2S and FeS.

          FeO + SiO2  →  FeSiO3    (Slag)

A Copper matte is then charged into a silica-lined converter. Some silica is combined, and a hot air blast is blown to change into the remaining.

FeS2, FeO and Cu2S or Cu2O to the metallic Cu.

Below reactions take place:

        2FeS + 3O2 → 2FeO + 2SO2

        FeO + SiO2 → FeSiO3)

        2Cu2S + 3O2 → 2Cu2O + 2SO2

        2Cu2O + Cu2S → 6Cu + SO2

The solidified Cu obtained has a blistered appearance because of the evolution of SO2, and hence it is known as blister copper. 

Extraction of Zinc from Zinc Oxide:

The reduction of zinc oxide is made using coke. The temperature is higher than that in the case of copper.

For heating, the oxide is made into briquettes with coke and clay.

ZnO + C →Zn + CO

Here, coke is the catalyst, and the temperature is 673 K.

The metal is distilled off and accumulates by rapid chilling. 

Electrochemical Principles of Metallurgy:

Electrolysis is done in the reduction of molten metal salts.

Suppose the below equation:

ΔG(0) = – nE(-)F 

n= no of electrons and E(-) = electrode potential of redox couple formed in the system.

More reactive metals have large -ve electrode potential values.

This implies that their reduction is complicated if the variety of two E(-) values corresponds to a positive E(-) and consequently a negative ΔG(0) in the equation.

As a result, the less reactive metal will come out of the solution, and the more reactive metal will go into the solution.

For Example:  Cu2+ (aq) + Fe(s) → Cu(s) + Fe2+ (aq)

In general electrolysis, the Mn+ ions are discharged at negative electrodes (cathodes) and deposited there. Rarely is a flux added to make the molten mass more conductive.

Aluminium:

In the metallurgy of Aluminium, purified Al2O3 is mixed with Na3AlF6 or CaF2, which lowers the melting point of the mix and brings conductivity. The fused matrix is electrolysed. Steel cathode and graphite anode are used. The graphite anode is applicable here for the reduction of the metal.

The net reaction may be shown as:

          2Al2O3 + 3C → 4Al + 3CO2

This method of electrolysis is widely known as the Hall-Heroult method.

The electrolysis of the molten mass is carried out in an electrolytic cell with carbon electrodes. The oxygen liberated at the anode interacts with the carbon of the anode, producing CO and CO2.

About 0.5 kilograms of carbon anode is burnt away for each kg of aluminium produced.

The electrolytic chemical reactions are

Cathode  Al3+ (melt) + 3e– → Al(l)

Anode  C(s) + O2– (melts) → CO(g) + 2e–

C(s) + 2O2– (melts) → CO2 (g) + 4e–

Refining:

As explained in the CBSE solutions Class 12 Chemistry, Chapter 6 Notes, refining plays a crucial role in metallurgy. Any metal extracted from its ore is usually impure. This impure metal that is extracted is known as crude metal. Refining is a method of removing impurities to obtain metals of high purity. The impurities are removed from hard metal by various techniques based on the properties of the metal and the properties of the impurities. 

Some of the processes involved in the purification of crude metal are shown below

•       Distillation.
•       Liquation.
•       Electrolysis.
•       Zone refining.
•       Vapour phase refining.
•       Chromatographic methods.

More detailed information on refining techniques is explained in the other study materials created by the subject experts at  Extramarks. 

Distillation: 

This technique is widely used to purify metals with low boiling points, like mercury and zinc. Impurities in metal are heated above their boiling points to produce vapour in this process.The impurities are not vaporised, and hence they are isolated. The mists of the pure metal are then condensed, leaving the impurities behind. Students may refer to various study materials, such as NCERT Solutions, CBSE Revision Notes, and Class 12 Chemistry Chapter 6 Notes, for a more detailed explanation.

Liquation: 

In this process, the melting point of the metals is taken into consideration. Metals with low melting points are purified using this method. The melting point of the impurities is higher than that of the metal.The metals are converted into liquid states by supplying heat slightly above their melting points. So pure metal melts and flows down from the furnace, leaving the impurities behind.

Electrolytic Refining:

Generally, the impure metal is made to act as the anode in this process. A pure strip form of the same metal is used as a cathode. They are kept in a suitable electrolytic bath consisting of soluble salts of the same metals.

The more basic metals remain in the solution, while the less basic ones go to the anode mud.

The reactions are:

Anode  M → Mn+ + ne–

Cathode  Mn+ + ne– → M

This process is used to refine copper, zinc, etc.

In the case of copper refining, anodes are impure copper, and pure copper strips are taken as a cathode.

The electrolyte is an acidified solution of CuSO4 (copper sulphate) and the overall result of electrolysis is the transfer of copper in pure form from the anode to the cathode:

Anode Cu → Cu2+ + 2 e–

Cathode  Cu2+ + 2e– → Cu

Impurities from the blister copper are collected as anode mud that contains antimony, selenium, tellurium, silver, gold, and platinum. Recovery of these elements may meet the cost of refining.

Zone refining:

This process depends on the principle that the impurities are more soluble in the molten form than in the solid form of the metal. A circular mobile heater is constant at one end of a rod of impure metal. The molten zone proceeds along with the heater, which is moved forward. The pure metal crystallises out of the melt as the heater proceeds, and the impurities transfer into the adjacent molten zone. The method is repeated several times, and the heater is moved in the same direction. At one end, impurities get concentrated. This end is cut off. This method is beneficial for producing semiconductors and other metals of very high purity. 

Examples include germanium, silicon, boron, gallium, and indium. 

Vapour phase refining:

Students learn in this topic that the metal should form a volatile compound in a reagent and quickly decompose to recover the metal in this type of purification. The metal is changed into its volatile compound. This volatile compound then undergoes decomposition to yield pure metal. 

For Example, Nickel is purified in this way. 

Chromatography:

Chromatography is a technique for separating, purifying, and testing metals and organic compounds. The term “chromatography” is derived from Greek, with chroma meaning “colour,” and graphene meaning “to write.”

This method applies the mixture to be isolated to a stationary phase (solid or liquid). A pure solvent like water or any gas can pass slowly over the stationary phase, moving the components separately as per their solubility in the pure solvent.

Chromatography principle: 

This is a separation method where the analyte is mixed within a liquid or gaseous mobile phase and pumped by a stationary phase. Usually, one phase is hydrophilic, and another phase is lipophilic. 

Components of the analyte communicate differently with these two phases. Depending on their polarity, they spend more or less time interacting with the stationary phase and are therefore retarded to a greater or lesser extent. 

The Separation of the various components in the sample: 

Each sample component elutes from the stationary phase at a specific retention time. As components pass through the detector, their signal is recorded, and the graph is plotted in a chromatogram. 

In addition to the Chromatography principle, students also learn the types of Chromatography in this Chapter. 

There are four types of chromatography.  

1. Adsorption Chromatography.

1. Thin-layer Chromatography.
2. Column Chromatography.
3. Partition Chromatography.

Students may learn more about it in CBSE solutions and other study resources provided by Extramarks. Extramarks provide detailed study material and Revision Notes. Students may click here to access Notes on Chromatography.

 Applications of Chromatography:

In bioanalytical Chemistry, chromatography is widely used to separate, isolate, and purify proteins from complex sample matrices. In cells, forexample, proteins occur alongside numerous other compounds such as lipids and nucleic acids. . These proteins must be isolated from all the different cell components to be analysed.

Students may refer to various study materials based on CBSE solutions Class 12 Chemistry Chapter 6 Notes to ace their examinations, all available at the Extramarks website. 

Importance of Aluminium, Copper, Zinc, and  Iron:

Aluminium: 

• Aluminium foil is used as chocolate wrappers.

• The fine dust of the metal is used in paints and lacquers. 

• Al, a highly reactive element, is also used to extract chromium and manganese from their oxides.

• Aluminum wires are used as electrical conductors. 

• Alloys that contain aluminium, being light, are very useful.

Copper: 

• Copper is used for making wires used in the electrical industry and for water and steam pipes. 
• It is also involved in several alloys that are somewhat tougher than the metal itself, such as brass (with zinc), bronze (with tin), and coinage alloy (with nickel). 

Zinc: 

• Zinc is used for galvanising iron. 
• It is also applied in large quantities in batteries as a constituent of many alloys, such as brass (Cu 60%, Zn 40%) and German silver (Cu 25-30%, Zn 25-30%, Ni 40–50%). 
• Zinc dust is applied as a reducing agent in the manufacture of dyestuff, paints, etc. 

Iron: 

• Cast iron, the most important form of iron, is used for casting stoves, railway sleepers, gutter pipes, toys, etc. 
• It is used in the manufacture of wrought iron and steel. 
• Wrought iron is used in making anchors, wires, bolts, chains, and agricultural implements. 
• Steel has several uses: 
• Alloy steel is obtained when other metals are added to it. 
• Nickel steel is used for making cables, automobiles, and aeroplane parts, pendulums, and measuring tapes, chrome steel is used for cutting tools and crushing machines, and stainless steel is used for cycles, automobiles, utensils, pens, etc.

Key summary points from Class 12 Chemistry Chapter 6 Notes:

• Metallurgy: Some processes are used to extract metals from their ores. It also includes their purification and alloy formation.
• Ore: A mineral from which one or more metals can be extracted efficiently and profitably.
• Flux:  A substance used to reduce the melting point of ore or react with gangue and convert it to slag.
• Gangue: Earthy impurities present with minerals are also called Gangue or matrix.
• Pyrometallurgy: Methods of thermal reduction (using a reducing agent and heat) of ores to metals.
• Hydrometallurgy: The method of extracting metals using leaching and displacement by employing reactive metals.
• Leaching: The process of reacting an ore with a reagent in order to extract the required material as water-soluble salts.

• Ellingham diagrams: Plot of ΔfG0 oxide. Temperature versus sulphide or halide per mole of oxygen, sulfur, or halogen, respectively.

• Smelting: Heating purified oxide form of Ore with coke. It may be metal or matte. It is generally known as the carbon reduction method.

• Aluminothermy: Method of reducing oxide of metal by heating with powdered aluminium.

Class 12 Chemistry Chapter 6 Notes: Exercise & Answer Solutions

CBSE solutions and Class 12 Chemistry Chapter 6 Notes exercise and answer solutions developed by the Extramarks team are based on NCERT books. Every exercise is compiled to add more value to the chapter. Students may refer to various study materials, such as revision notes, past year question papers, essential questions, and more about NCERT and CBSE solutions on Extramarks website.

CBSE solutions Class 12 Chemistry Chapter 6 Notes are explained in detail by the experts at Extramarks. In addition to Chapter 6, students can access the CBSE Solution for all other Chemistry chapters of Class 12. Furthermore, students can click on the links provided below to access the study material for different classes and subjects.

Students can click on the links provided below to access the solutions to the exercises they may need to prepare for the examination.

• Class 12 Chemistry Chapter 6: Exercise and Solutions

 Students can refer to the respective exercise to access the NCERT solutions Class 12 Chemistry Chapter 6. Students can also explore all types of educational content on the Extramarks website. Click on the respective links below to learn more.  

• NCERT Solutions Class 1
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• NCERT Solutions Class 4
• NCERT Solutions Class 5
• NCERT Solutions Class 6
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• NCERT Solutions Class 9
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• NCERT Solutions Class 11
• NCERT Solutions Class 12

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• NCERT Solutions
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NCERT Exemplar Class 12 Chemistry Chapter 6

All exemplar problems and solutions are given to help students prepare for their examinations. These exemplar questions are a little more complex, and they cover every concept covered in each chapter of the Class 12 Chemistry NCERT syllabus.

Students will fully understand all the concepts covered in each chapter by practising the questions and solutions from Extramarks Class 12 Chemistry Chapter 6 Notes that cover exemplar specific questions.

Exemplars provide the best solutions to the challenges that students confront. To match the ideas taught in each class and provide the most outstanding practising materials or worksheets for students, all of these questions strictly follow updated 2021-22 CBSE guidelines.

Key Features of CBSE Solutions Class 12 Chemistry Chapter 6 Notes

The general principles and processes of element isolation are an essential topic for examinations like IIT, JEE, and NEET. Hence, while studying chemistry, the best quality notes and solutions provided by Extramarks prove helpful for students. Class 12 Chemistry Chapter 6 Notes can help students understand the topics covered in the chapter easily and quickly.

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