CBSE Class 10 Science 2015 Term I Set 1

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Question : 19
Total: 36
In column I different methods of extraction are given. Name the methods used for the extraction of metals given in Column II :
 Column-I  Column-II
 (i) Reduction with carbon  Al, Zn, Na, Fe, Mn, Pb
 (ii) Electrolytic reduction
 (iii) Reduction with aluminium
(b) Differentiate between roasting and calcination processes giving one example of each.
Solution:  
 Column-I  Column-II
 (i) Reduction with carbon  Zn,Fe,Pb
 (ii) Electrolytic reduction  Al,Na
 (iii) Reduction with aluminium  Mn
(b) Difference between roasting and calcination.
 S.No.  Roasting  Calcination
 1.   Roasting is done in case of sulphide ores.  Calcination is done in case of carbonate ores.
 2  In this, the ore is heated in the presence of excess air to convert it into its oxide compound.  The carbonate ore is heated in the absence of air (limited supply of air) to convert into its oxide.
 3  The gas given out is SO2 (sulphur dioxide) gas.
Example:
2ZnS+
3O2
Air
Heat
2
ZnO
+2SO2
 The gas given out is mathrmCO2 (carbon dioxide) gas.
Example:
ZnCO3
Heat
ZnO
+CO2
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