NCERT Solutions for Class 12 Chemistry Chapter 6 

NCERT Solutions for Class 12 Chemistry Chapter 6 General Principles and Processes of Isolation of Elements

NCERT Class 12 Chemistry Chapter 6 details the Principles and Processes of Isolation of Elements. Students will learn various terminologies such as concentration, calcination, roasting, refining, etc., in this chapter. In addition, they will understand the methodologies of oxidation and reduction as used within the extraction procedures. With chapter6 class 12 Chemistry, 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. All in all, chapter 6 class 12 Chemistry, will be helpful to understand the large number of chemical processes associated with metallurgy.

Keeping in mind the growing curiosity of students, Extramarks has curated NCERT solutions class 12 Chemistry chapter 6 to aid students to understand the various concepts detailed in the chapter. Students may refer to the NCERT class 12 Chemistry chapter 6 study material for free on Extramarks.

Key Topics Covered In NCERT Solutions Class 12 Chemistry Chapter 6

The key topics covered in NCERT solutions class 12 Chemistry chapter 6 – Principles and Processes of Isolation of Elements are in the table below. 

Students can click on the above topics under NCERT solutions class 12 Chemistry chapter 6 to refer to the study material, revision notes, and essential questions that can help them during their examination.

The key topics covered in NCERT solutions class 12 Chemistry chapter 6 in brief:

6.1 Introduction

The first exercise under class 12 Chemistry chapter 6 NCERT solutions 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. The minerals in which the metal is present and extracted are called ores. Usually, the ores contain impurities that can be removed to a specific limit in the concentration steps. After this step, the ore is chemically treated to obtain metals. With the help of reducing agents such as CO, carbon, etc., the metal compound is decreased to metal. Then, 

1. The metal oxide reacts with a reducing agent;
2. A. The oxide reduces to metal

1. Oxidation of reducing agent

The Isolation of elements as defined in the NCERT solutions class 12 Chemistry chapter 6 aims to teach the students different extraction processes of metals from ores. Some metals, such as noble metals,  Gold, Silver, Platinum etc., are present in their original metallic state. Metallurgy is the branch of science that works with extracting metals from ores that are naturally available in the environment.

All of the elements, especially metals, are presently combined with other elements, and these are called minerals. An element may combine with various other elements to make various minerals, but out of them, only a few are feasible sources of that metal. Such sources are known as Ores.

6.2 Extraction of metals

Under this exercise of NCERT solutions 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. 

Extraction of metals and their Isolation occurs over some significant steps:

•       Concentration of Ore
•       Isolation of metal from concentrated ore
•       Purification of the metal

Aluminium:

•       Bauxite AlOx(OH)3-2x [where 0 < x < 1]
•       Kaolinite (a form of clay) [Al2 (OH)4 Si2O5]

Iron:

•       Haematite Fe2O3
•       Magnetite Fe3O4
•       Siderite FeCO3
•       Iron pyrites FeS2

Copper:

•       Copper pyrites CuFeS2
•       Malachite CuCO3.Cu(OH)2
•       Cuprite Cu2O
•       Copper glance Cu2S

Zinc:

•       Zinc blende/Sphalerite ZnS
•       Calamine ZnCO3
•       Zincite ZnO

6.3 Gibbs free energy:

As per the definition compiled in NCERT 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. Gibbs’s free energy is represented by the symbol ‘G’, 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’s 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

equation

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: The Gibbs free energy is a state function; therefore, it is not dependent on the path. As defined in NCERT solutions class 12 Chemistry chapter 6,  a change in Gibbs free energy gives a change in enthalpy minus the product of temperature and entropy change of the system. 

ΔG = ΔH – Δ(TS)

If the reaction happens under constant temperature ΔT=O

ΔG = ΔH – TΔS

This equation shows as the Gibbs Helmholtz equation. 

ΔG > 0; the reaction is nonspontaneous as well as endergonic

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

ΔG = 0; reaction is at equilibrium

 The Spontaneity of a process Gibbs equation suggests we conclude the Spontaneity of reaction due to enthalpy and entropy values directly. 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 E.g. 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. 

6.4 Gibbs Energy in Chemistry

Under NCERT solutions class 12 Chemistry Chapter 6 Exercise 6.4, students learn about Gibbs energy. In the energetics of processes for systems at constant temperature and pressure, the appropriate quantity is the Gibbs free energy. The Gibbs free energy has a beneficial property, decreasing for a spontaneous process at constant temperature and pressure. Under these conditions, Gibbs’s free energy decrease equals the maximum amount of energy available for work. Whether it increases for some transition, the change in Gibbs free energy constitutes the minimum amount of work required. 

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

 6.5 Refining

Refining plays a crucial role in metallurgy, which has been explained in NCERT solutions class 12 Chemistry chapter 6. 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 impurities. 

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

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

Detailed information given by refining the technique is explained in the chapter.

Distillation: This technique is widely used to purify metals with low boiling points, like mercury and zinc. In this process, the impure metal is heated above its boiling point so that it can produce vapour. The impurities are not vapourised, and hence they are isolated. The mists of the pure metal are then condensed, leaving the impurities behind.

Liquation: In this process, the melting point of the metals is taken into consideration. Metals having low melting points are purified using this method. The melting point of the impurities is maximized in comparison to the metal. The metals are converted into liquid states by supplying heat slightly above their melting point. So pure metal melts and flows down from the furnace, leaving the impurities behind. 

Vapour phase refining: Under this topic of NCERT solutions class 12 Chemistry chapter 6, students learn that in this type of purification, the metal should form a volatile compound in the presence of a reagent, and it should decompose quickly to recover the metal. The metal is transformed into its volatile compound. This volatile compound then undergoes decomposition to give pure metal. For example, nickel is purified in this way. 

6.6 Chromatography:

In this exercise of NCERT solutions class 12 Chemistry chapter 6, students learn about Chromatography as a technique for separating, purifying, and testing metal and organic compounds. The term “chromatography” is derived from Greek, chroma meaning “colour,” and graphein meaning “to write.”

In this method, we apply the mixture to be isolated on 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, pumped by a stationary phase. Normally, 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 present 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 under NCERT solutions class 12 Chemistry chapter 6. There are four types of chromatography.  

1. Adsorption Chromatography
2. Thin layer Chromatography
3. Column Chromatography
4. Partition Chromatography

Students may learn more about it in NCERT solutions class 12 Chemistry chapter 6, provided by Extramarks. Extramarks provides detailed study material and revision notes. Students may click here to access notes on Exercise 6.6.

 6.7 Applications of Chromatography

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

Students may refer to various study materials based on NCERT solutions class 12 Chemistry chapter 6 to ace their exams. 

NCERT solutions class 12 Chemistry chapter 6 Exercise & Answer Solutions

The NCERT solutions class 12 Chemistry chapter 6 exercise and answer solutions 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 questions papers, important questions, and more pertaining to NCERT solutions on Extramarks.

NCERT solutions class 12 Chemistry chapter 6 is explained in detail by the experts of Extramarks. In addition to chapter 6, students can access NCERT Solution for all other Chemistry chapters of class 12. Furthermore, students can click on the links provided below to access the study material of other classes and subjects.

NCERT Solution Class 12

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NCERT Solution Class 9

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NCERT Solution Class 7

NCERT Solution Class 6

NCERT Solution Class 5

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NCERT Solution Class 2

NCERT Solution Class 1

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