12th Standard CBSE Syllabus & Materials
12th Standard CBSE
CBSE 12th Economics Government Budget and the Economy Previous year Question Papers Study Material - QB365 Set A
NEW12th Standard CBSE
CBSE 12th Computer Science Interface Python with MySQL - New Previous year Question Papers Study Material - QB365 Set A
NEW12th Standard CBSE
CBSE 12th Computer Science Database Concept - New Previous year Question Papers Study Material - QB365 Set A
NEW12th Standard CBSE
CBSE 12th Computer Science Data Communication - New Previous year Question Papers Study Material - QB365 Set A
NEW12th Standard CBSE
CBSE 12th Computer Science Data Structures - New Previous year Question Papers Study Material - QB365 Set A
NEW12th Standard CBSE
CBSE 12th Computer Science Functions - New Previous year Question Papers Study Material - QB365 Set A

Published on: 05/10/2019
General Principles and Processes of Isolation of Elements
Download CBSE Class 12th Standard CBSE Chemistry question papers, sample papers, important questions, and previous year solved papers in PDF format. Get free study materials, NCERT solutions, and exam preparation resources for Class 12th Standard CBSE Chemistry
Questions + Answers key
Take MCQ Chemistry Test

1.
Metals are very useful in our daily life. Aluminium powder is used in white paints. It is also used as a reducing agent. Alloys containing aluminium being light, are very useful. Utensils of aluminium are more popular than utensils of brass. Metals like silver, gold, iron, copper, zinc are very useful in our daily life.
What value is associated for using aluminium?
2.
Metals are very useful in our daily life. Aluminium powder is used in white paints. It is also used as a reducing agent. Alloys containing aluminium being light, are very useful. Utensils of aluminium are more popular than utensils of brass. Metals like silver, gold, iron, copper, zinc are very useful in our daily life.
Why are aluminium vessels preferred over copper and bronze vessels?
3.
Metals are very useful in our daily life. Aluminium powder is used in white paints. It is also used as a reducing agent. Alloys containing aluminium being light, are very useful. Utensils of aluminium are more popular than utensils of brass. Metals like silver, gold, iron, copper, zinc are very useful in our daily life.
(i) Which metal foils are used as wrappers for sweets, medicines, chapaties ties etc ?
(ii) Why are aluminium vessels preferred over copper and bronze vessels?
(iii) What value is associated for using aluminium?
4.
In roasting, the are is heated in a regular supply of air in furnace at a temperature below the melting point of the metal. Metal sulphide gets converted into metal oxide and sulphur dioxide gas is formed
which is air pollutant. It also leads to the formation of acid rain which is harmful for crops and buildings made from marble.
How can sulphuric acid help in national economy?
5.
In roasting, the are is heated in a regular supply of air in furnace at a temperature below the melting point of the metal. Metal sulphide gets converted into metal oxide and sulphur dioxide gas is formed
which is air pollutant. It also leads to the formation of acid rain which is harmful for crops and buildings made from marble.
(i) Where should we have industries using roasting process in metallurgy? Give reason.
(ii) How can sulphuric acid help in national economy?
6.
While washing a miner's overalls, a washer woman noticed that sand and similar dirt fell to the bottom of the wash tub. What was peculiar, the copper bearing compounds that had come to the clothes from the mines were caught in the soaplids and so they came to the top. One of her clients was a chemist, Mrs. Malik. The washer woman told her experience to Mrs. Malik. The latter thought that the idea could be used for separating copper compounds from rocky and earth materials on a large scale. After reading the above passage answer the following questions-
What values are shown by washer woman and Mrs.Malik?
7.
While washing a miner's overalls, a washerwoman noticed that sand and similar dirt fell to the bottom of the washtub. What was peculiar, the copper-bearing compounds that had come to the clothes from the mines were caught in the soaplids and so they came to the top. One of her clients was a chemist, Mrs. Malik. The washerwoman told her experience to Mrs. Malik. The latter thought that the idea could be used for separating copper compounds from rocky and earth materials on a large scale. After reading the above passage answer the following questions-
What type of ores are concentrated by this process?
8.
While washing a miner's overalls, a washer woman noticed that sand and similar dirt fell to the bottom of the wash tub. What was peculiar, the copper bearing compounds that had come to the clothes from the mines were caught in the soaplids and so they came to the top. One of her clients was a chemist, Mrs. Malik. The washer woman told her experience to Mrs. Malik. The latter thought that the idea could be used for separating copper compounds from rocky and earth materials on a large scale. After reading the above passage answer the following questions-
(i) Name the process of concentration of ore based on the observation of washer woman.
(ii) What type of ores are concentrated by this process?
(iii) What values are shown by washer woman and Mrs.Malik?
9.
Why is the reduction of a metal oxide easier if the metal formed is in liquid state at the temperature of reduction?
10.
Explain the following
i. Carbon reduction process is not applied for reducing aluminium oxide to aluminium.
ii. Aq Sodium chloride cannot be used for the isolation of sodium by electrolytic reduction method.
iii. Thermite process is quite useful for repairing the broken parts of machines.
1.
Aluminium is very useful metal. It is very light and good conductor of both heat and electricity. Although it is placed high up in the series but layer of its oxide deposited on the surface of the metal checks its corrosion.
2.
Aluminium vessels are not affected either by acids or alkalies or by other chemicals, but copper and bronze vessels react with these forming poisonous chemical compounds.That's why, vessels are made up of aluminium are preferred.
3.
(i) Aluminium metal
(ii) Aluminium vessels are not affected either by acids or alkalies or by other chemicals, but copper and bronze vessels react with these forming poisonous chemical compounds.That's why, vessels are made up of aluminium are preferred.
(iii) Aluminium is very useful metal. It is very light and good conductor of both heat and electricity. Although it is placed high up in the series but layer of its oxide deposited on the surface of the metal checks its corrosion.
4.
Sulphuric acid is one of the most useful industrial chemicals. It is used in strongest batteries, in textiles paper and leather industry, in manufacture of points and pigments.
5.
(i) The industries involving the roasting of sulphur ores must be installed at place far from the cities so that the pollution caused by release of S02 gas may not affect human beings.
(ii) Sulphuric acid is one of the most useful industrial chemicals. It is used in strongest batteries, in textiles paper and leather industry, in manufacture of points and pigments.
6.
Keen observation, love for mankind, love for enviroment, will to explore and experiment, general awareness.
7.
Only sulphide ores like ZnS, CuFeS2, etc. are concentrated by froth floatation process
8.
(i) Froth floatation process.
(ii) Only sulphide ores like ZnS, CuFeS2, etc. are concentrated by froth floatation process
(iii) Keen observation, love for mankind, love for enviroment, will to explore and experiment, general awareness.
9.
The entropy is higher if the metal is in liquid state than when it is in solid state. The value of entropy change (DS) of the reduction process is more on positive side when the metal formed is in liquid state and the metal oxide being reduced is in solid state. Thus the value of DrG V becomes more on negative side and the reduction becomes easier.
10.
(i) Carbon isn't utilized for diminishing aluminum oxide since aluminum is more responsive than carbon. Thus, carbon can't uproot aluminum from its oxide. Aluminum oxide is exceptionally steady and Carbon is less responsive than aluminum, hence it can't be utilized to diminish aluminum oxide to aluminum metal.
(ii) An aqueous solution of sodium chloride is not used for electrolysis because aqueous solution contains water as well which results in the formation of sodium hydroxide in the solution and sodium metal is not obtained.
NaCl(aq) -Electricity- NaOH(aq) + H2(g)(at cathode) + Cl2(g)(at anode)
Hence molten sodium chloride is used to extract sodium from sodium chloride.
NaCl(l) -Electricity-Na(s)(at cathode) + Cl2(g)(at anode)
(iii) The reduction of a metal oxide to form metal by using aluminium powder as a reducing agent is called a thermite reaction. This reduction property of aluminium is used in thermite welding for joining the broken pieces of heavy iron objects like girders, railway tracks or cracked machine parts.
12th Standard CBSE Syllabus & Materials
12th Standard CBSE
CBSE 12th Computer Science Python Revision Tour I - New Previous year Question Papers Study Material - QB365 Set A
NEW12th Standard CBSE
CBSE 12th Business Studies Planning Important Questions And Answers Study Material - QB365 Set A
NEW12th Standard CBSE
CBSE 12th Business Studies Business Environment Important Questions And Answers Study Material - QB365 Set A
NEW12th Standard CBSE
CBSE 12th Business Studies Principles of Management Important Questions And Answers Study Material - QB365 Set A
CBSE 12th Standard CBSE Subjects
CBSE Standards