Important Questions for Class 12 Chapter 6 - General Principles and Processes of Isolation of Elements

Important questions based on NCERT syllabus for Chapter 6 - General Principles and Processes of Isolation of Elements:

Question-1: What is meant by the term “chromatography”?

Solution: Chromatography is a technique used for separation, purification, identification and characterization of the components of a mixture whether coloured or colourless. The term chromatography was originally derived from the Greek word ‘chroma’ meaning colour and ‘graphy for writing because the method was first used for the separation of coloured substances (plant pigments) into individual components

Question-2: The choice of a reducing agent in a particular case depends on thermodynamic factor. How far do you agree with this statement? Support your opinion with two examples.

Solution: We can study the choice of a reducing agent in a particular case using Ellingham diagram.
It is evident from the diagram that metals for which the standard free energy of formation oftheir oxides is more negative can reduce those metal oxides for which the standard free energy of formation of their respective oxides is less negative. It means that any metal will reduce the oxides of other metals which lie above it in the Ellingham diagram. This is because the standard free energy change (ΔrG°) of the combined redox reaction will be negative by an amount equal to the difference in Δf G° of the two metal oxides. Thus both Al and Zn can reduce FeO to Fe but Fe cannot reduce Al203 to A1 and ZnO to Zn. In the same way, G can reduce ZnO to Zn but not CO.

Question-3: Which of the ores mentioned can be concentrated by magnetic separation method?

Solution: Ores Which are magnetic in nature can be separated from non-magnetic gangue particles by magnetic separation method. For ex: ores of iron such as haemetite (Fe2O3), magnetite (Fe3O4), siderite (FeCO3) and iron pyrites (FeS2 ) being magnetic can be separated from non-magnetic silica and other impurities by magnetic separation method.