on September 29, 2022, 3:53 AM
NCERT Solutions for Class 12 Chemistry Chapter 6 General Principles and Processes of Isolation of Elements in Hindi and English Medium updated for session 2023-2024. Students can get the solutions of intext and exercises questions of 12th Chemistry unit 6 in simple format.
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Processes of Isolation of Elements
The extraction and isolation of metals from ores involve the following major steps:
- (A) Concentration of the ore (or) Purification of the Ore
- (B) Isolation of the metal from its concentrated ore
- (C) Purification of the metal (Or) Refining of the Metal.
Occurrence of Metals
A few elements like carbon, Sulphur, gold and noble gases, occur in free state while others are found in combined forms in the earth’s crust. Elements vary in abundance.
Ores
For obtaining a particular metal, first we look for minerals which are naturally occurring chemical substances in the earth’s crust and are obtained through mining. Out of many minerals in which a metal may be found, only a few are viable to be used as source of that metal. Such minerals are known as ores.
Metallurgy
Metallurgy is defined as a process that is used for the extraction of metals in their pure form. The compounds of metals mixed with soil, limestone, sand, and rocks are known as minerals.
Class 12 Chemistry Chapter 6 MCQ
Concentration of sulphide ore is done by
The salt which is least likely to be found in minerals is
Metallurgical Processes
Types of Metallurgical Processes
- Pyrometallurgy Extraction of metals takes place at very high temperature. Cu, Fe, Zn, Sn, etc. are extracted by this method.
- Hydrometallurgical process in this method, metals are extracted by the use of their aqueous solution. Ag and Au are extracted by this method.
- Electrometallurgical process Na, K, Li, Ca, etc., are extracted from their molten salt solution through electrolytic method.
12th Chemistry Unit 6 Multiple Choice Questions
The method of concentrating the ore which makes use of the difference in density between ore and impurities is called
Which of the following sulphides when heated strongly in air gives the corresponding metal without undergoing separate reduction of oxide?
Which of the following metals is sometimes found native in nature?
Extraction of iron from its oxides
Oxide ores of iron, after concentration through calcination/roasting (to remove water, to decompose carbonates to oxides and sulphides) are mixed with limestone and coke and fed into a Blast furnace from its top. Here, the oxide is reduced to the metal.
The iron obtained from Blast furnace contains about 4% carbon and many impurities in smaller amount (e.g., S, P, Si, Mn). This is known as pig iron. It can be moulded into variety of shapes. Cast iron is different from pig iron and is made by melting pig iron with scrap iron and coke using hot air blast. It has slightly lower carbon content (about 3%) and is extremely hard and brittle.
Wrought iron
Wrought iron or malleable iron is the purest form of commercial iron and is prepared from cast iron by oxidising impurities in a reverberatory furnace lined with haematite. The haematite oxidises carbon to carbon monoxide:
Fe₂O₃ + 3C ⟶ 2Fe + 3CO
Class 12 Chemistry Chapter 6 Important Questions
What is general principles and processes of isolation of elements?
It is usually contaminated with earthly or undesired materials known as gangue. The extraction and isolation of metals from ores involves the following major steps: • Concentration of the ore, • Isolation of the metal from its concentrated ore, and • Purification of the metal.
Why are alloys used instead of pure metals?
Almost all metals are used as alloys—that is, mixtures of several elements—because these have properties superior to pure metals. Alloying is done for many reasons, typically to increase strength, increase corrosion resistance, or reduce costs.
Which is ferrous metal?
Ferrous metals include steel, cast iron, as well as alloys of iron with other metals (such as with stainless steel etc.).
