Page 217 - Chemistry ICSE Class X

Metallurgy 203
10. Give reasons:

(a) Gold and silver often occur in native state.
(b) Metals displace hydrogen from acids, whereas nonmetals do not.
(c) Carbonates and sulphides ores are usually converted into oxides before reduction.
11. State the reason for the following behaviour of zinc metal:
On placing a piece of zinc metal in a solution of mercuric chloride, it acquires a shining silvery surface but when
it is placed in a solution of magnesium sulphate, no change is observed.
12. (a) Name any two neutral oxides.
(b) How are metalloids different from metals? Name a metalloid.
(c) Differentiate between roasting and calcination processes used in metallurgy. Give one example of each.
13. Give reasons for the following:
(a) Metals conduct electricity.
(b) Reaction of nitric acid with metals generally does not evolve hydrogen gas.

(c) For making gold ornaments, 22-carat gold is preferred to 24-carat gold.
14. Give reasons for the following:
(a) Na, K and Ca metals form hydrides by combination with hydrogen gas, but most other metals do not.
(b) Aluminium easily combines with oxygen but still it can be used for making kitchen utensils.
15. Name two elements that are stored under kerosene.
16. (a) Name an ore of zinc other than zinc oxide.
(b) By what process can this ore be converted to zinc oxide?
17. What are silica and cryolite chemically? State one use for each of them in metallurgical processes.
18. With the help of a labelled diagram, describe the main steps involved in the enrichment of ores by the process of
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19. Write the chemical equation for
(a) the reaction taking place between sodium metal and cold water.
(b) the reaction of hot aluminium with steam.
20. Name two metals both of which are very ductile as well as very malleable.
21. (a) Why is ZnO called an amphoteric oxide? Name another amphoteric oxide.

(b) What are alkalis? Give one example of alkalis.
22. (a) Write chemical equations for the reactions involved in obtaining pure alumina from the mineral bauxite
which has impurities of iron oxide and silica.
(b) Draw a labelled diagram of the electrolytic tank cell used for the extraction of aluminium from alumina.
23. State reasons for the following:
(a) Aluminium oxide is called an amphoteric oxide.
(b) Sodium and potassium metals are kept immersed under kerosene.
(c) Hydrogen gas is not evolved when most metals react with nitric acid.
24. (a) What is meant by the term ‘enrichment of ore’?
(b) Name four methods generally used for the enrichment of ores.
(c) With the help of a labelled diagram, describe the method for the enrichment of sulphide ores.
25. (a) Name the different varieties of iron.
(b) Mention one use each of those mentioned in (a).
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its constituents?