METALS - I : MCQs & SHORT ANSWERS

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MULTIPLE-CHOICE QUESTIONS

SELECT THE CORRECT ALTERNATIVE:

1. ______ is the formula of cuprite.
   
   
   
   1. Cu₂O
   2. Cu₂S
   3. CuCO₃
   4. CuCl₂
      
   
   
2. Siderite is an ore of ______.
   
   
   
   1. Copper
   2. Silver
   3. Calcium
   4. Iron
      
   
   
3. ______ is an ore of calcium.
   
   
   
   1. Magnetite
   2. Siderite
   3. Malachite
   4. Gypsum
      
   
   
4. During electrolytic reduction, ______ acts as reducing agent.
   
   
   
   1. anode
   2. cathode
   3. electrolyte
   4. the metal
      
   
   
5. Liquefaction method is used for the purification of metals with ______.
   
   
   
   1. high melting point
   2. low melting point
   3. high boiling point
   4. low boiling point
      
   
   
6. The formula of cryolite is ______.
   
   
   
   1. Cr₂O₃
   2. Na₃AlF₆
   3. Na₂AlF₆
   4. Na₂Cr₂O₇
      
   
   
7. Which of the following is a liquid metal at room temperature ?
   
   
   
   1. Sodium
   2. Cobalt
   3. Bromine
   4. Mercury
      
   
   
8. ______ is the best conductor of heat and electricity.
   
   
   
   1. Gold
   2. Silver
   3. Copper
   4. Iron
      
   
   
9. ______ is a poor conducting metal for heat.
   
   
   
   1. Copper
   2. Silver
   3. Aluminium
   4. Lead
      
   
   
10. The melting point of iron is ______ °C.
    
    
    
    1. 1539
    2. 1639
    3. 1359
    4. 1369
       
    
    
11. The true order of reactivity of metals with dil. HCl is ______.
    
    
    
    1. Mg>Al>Zn>Fe
    2. Mg>Zn>Fe>Al
    3. Al>Mg>Zn>Fe
    4. Zn>Mg>Al>Fe
       
    
    
12. Pure gold is ______ carats.
    
    
    
    1. 22
    2. 23
    3. 24
    4. 25
       
    
    
13. Which of the following is used as a semi-conductor ?
    
    
    
    1. Copper
    2. Silver
    3. Gold
    4. Germanium
       
    
    
14. The main constituent of bauxite is ______.
    
    
    
    1. Al₂O₃
    2. Al₂(SO₄)₃
    3. CaSO₄
    4. Na₃AlF₆
       
    
    
15. Which method is used for the purification of more reactive metals ?
    
    
    
    1. Chemical reduction
    2. Roasting
    3. Calcination
    4. Electrochemical reduction
       
    
    
16. Which reaction takes place at anode in an electrolytic process ?
    
    
    
    1. Oxidation
    2. Reduction
    3. Oxidation-reduction
    4. None of above
       
    
    
17. Which metal is obtained in liquid state (during extraction) ?
    
    
    
    1. Sodium
    2. Gallium
    3. Tin
    4. Uranium
       
    
    
18. Which substance is used to decrease the melting point of alumina in Hall - Haroult process ?
    
    
    
    1. CuSO₄
    2. Cryolite
    3. Gypsum
    4. Limonite
       
    
    
19. ______ is used in manufacturing scientific balance.
    
    
    
    1. Steel
    2. Brass
    3. Stainless steel
    4. Magnalium
       
    
    

ANSWERS TO MCQs

(1) A (2) D (3) D (4) B (5) B (6) B (7) D (8) B (9) D (10) A (11) A (12) C (13) D (14) A (15) D (16) A (17) C (18) B (19) D (20)

SHORT QUESTIONS

ANSWER IN SHORT:

1. Which metals are available in free state in nature ?
   
        ANS : Less reactive metals like gold, silver and copper are available in free state in nature.
   
2. Why are metals like sodium, potassium and aluminium not available in free state in nature ?
   
        ANS : Metals like sodium, potassium and aluminium are not available in free state in nature because they are more reactive metals.
   
3. Define : Mineral.
   
        ANS :Elements as well as elements in the form of their compounds which are available in earth's crust are known as minerals. OR A naturally occuring compound in which the metal exists either in native state or combined state is called mineral.
   
4. Define : Ore.
   
        ANS : A metal in the form of its compounds with other elements and/or their compounds is known as an ore. OR A mineral from which a metal can be extracted economically and conveniently is called an ore.
   
5. In what form are ores/minerals generally found in nature ?
   
        ANS : Generally, ores/minerals are found in the form of oxides, silicates, sulphides, carbonates, phosphates, etc.
   
6. Write names of two ores of copper.
   
        ANS : Cuprite and malachite are two ores of copper.[Also, copper pyrite and copper glance are ores of copper.]
   
7. Write the formula of siderite and gypsum.
   
        ANS : The formula of siderite is FeCO₃ and that of gypsum is CaSO₄.2H₂O.
   
8. Mention three main spheres of earth.
   
        ANS : Three main spheres of earth are : Lithosphere, Hydrosphere and Atmosphere.
   
9. Which elements are found in lithosphere ?
   
        ANS : Lithosphere mainly consists of oxides and sulphides of elements like aluminium, sodium, iron, copper, calcium, etc.
   
10. Which elements are found in the liquid sphere (hydrosphere) of the earth ?
    
         ANS : Hydrosphere contains elements like chlorine, bromine, sodium, potassium, magnesium in the form of their compounds.
    
11. Define : Metallurgy.
    
         ANS : The process of extracting pure metals from their ores and refining them for commercial use is called metallurgy.
    
12. What is gangue (or matrix) ?
    
         ANS : The impurities such as sand, stones, earthy matter, etc. present in the ore are called gangue (or matrix).
    
13. On what does the process of metallurgy depend ?
    
         ANS : The process of metallurgy depends on (i) the nature of the metal to be extracted (ii) the type of impurity present in the ore.
    
14. Mention the equipment used for grinding of ore.
    
         ANS : Ball mill and Stamp mill are equipment used for grinding ore.
    
15. What is concentration of ore ?
    
         ANS : The process of removal of impurities from an ore is called concentration of ore.
    
16. Mention the methods employed for concentration of ore.
    
         ANS : Methods employed for concentration of ore are :
    
    
    • Froth floatation process
      
    • Magnetic Separation method
      
    • Centrifugal method
      
    • Chemical method.
      
    
    
17. What is the principle of froth floatation process ?
    
         ANS : The froth floatation process is based on the principle of difference in wetting properties of the ore and the gangue particles with water and oil.
    
18. What is the principle of magnetic separation method ?
    
         ANS : Magnetic separation method uses the principle of difference in the magnetic properties of the ore and the gangue.
    
19. What is the principle of centrifugal method ?
    
         ANS : The principle of centrifugal method is the difference in the densities of ore and the impurities.
    
20. Which type of ores are concentrated by chemical method ?
    
         ANS : Ores of highly reactive metals are concentrated by chemical method.
    
21. Define : Roasting.
    
         ANS : Heating a substance (concentrated ore) in presence of oxygen under controlled atmospheric pressure is called roasting.
    
22. What is the purpose of roasting in metallurgy ?
    
         ANS : In metallurgy, the purpose of roasting is the conversion of sulphide ore into oxide besides the removal of volatile impurities.
    
23. What is calcination ?
    
         ANS : Calcination is the process in which the concentrated ore is heated strongly in absence of air.
    
24. What is smelting ?
    
         ANS : Smelting is a process of heating an ore strongly to obtain metal in molten state by reduction.
    
25. What is reduction ?
    
         ANS : The conversion of metal oxide into metal is called reduction.
    
26. On what does the method of reduction depend ?
    
         ANS : The method of reduction depends on the nature and reactivity of the metal.
    
27. Mention some reducing agents.
    
         ANS : Carbon, carbon monoxide, alumunium, etc are examples of reducing agent.
    
28. What is taken as anode in electrolytic refining of a metal ?
    
         ANS : A rod of impure metal is taken as anode in electrolytic refining of a metal.
    
29. By which method are ultrapure elements obtained ?
    
         ANS : Ultrapure elements are obtained by Zone refining (fractional separation) method.
    
30. What is the use of van Arkel's method ?
    
         ANS : van Arkel's method is used for obtaining ultrapure elements like germanium and uranium.
    
31. What acts as cathode in electrolytic reduction of Al₂O₃ ?
    
         ANS : Carbon (graphite) lining inside the iron tank acts as cathode in electrolytic reduction of Al₂O₃.
    
32. What works as electrolyte in Hall-Haroult cell ?
    
         ANS : The mixture of molten Al₂O₃ and Na₃AlF₆ works as electrolyte in Hall-Haroult cell.
    
33. What is slag ?
    
         ANS : Calcium silicate formed from sand present in iron ore and calcium oxide produced by decomposition of calcium carbonate is called SLAG.
    
34. Which metals can liberate H⁺ ions from aqueous solutions of acids ?
    
         ANS : More reactive metals or the metals on the left side of hydrogen in the reactivity series can liberate H⁺ ions from aqueous solutions of acids.
    
35. What is emf (electromotive force) ?
    
         ANS : The cell potential of an electrochemical cell measured in comparison to standard hydrogen electrode is known as electromotive force (emf) of that cell.
    
36. What is emf series ?
    
         ANS : The series prepared by arranging oxidation potentials (emfs) of half cells (electrodes) in descending order is called emf series.
    
37. What is reactivity series of metals ?
    
         ANS : The arrangement of metals in order of their decreasing reactivities is called reactivity series of metals.
    
38. Mention the most malleable and ductile metals.
    
         ANS : Gold and silver are the two most malleable and ductile metals.
    
39. What do we mean by malleability ?
    
         ANS : Malleability means capacity to be hammered into very thin sheet without being broken.
    
40. What do we mean by ductility ?
    
         ANS : Ductility is a property of a substance (metal) by which it can be drawn into thin wires.
    
41. Mention three metals having low density.
    
         ANS : Sodium, potassium and magnesium are metals with low density.
    
42. Why are metals electropositive ?
    
         ANS : Metals are electropositive because their atoms can lose electrons easily to form positively charged ions.
    
43. What is the nature of the oxides of metals ?
    
         ANS : Oxides of metals are basic in nature.
    
44. Why are the oxides of metals basic ?
    
         ANS : Oxides of metals are basic because they form alkaline solutions with water.
    
45. What do we mean by amphoteric oxides ?
    
         ANS : Those oxides of metals which show both acidic as well as basic behaviour in aqueous solutions are called amphoteric oxides.
    
46. Mention some metals that do not react with water at all.
    
         ANS : Lead, copper, silver and gold are the metals that do not react with water at all.
    
47. Why are metals reducing agents ?
    
         ANS : Metals are reducing agents because they give electrons to other element and in turn get oxidised to respective positive ion.
    
48. What is corrosion ?
    
         ANS : The destruction of metal due to its exposure to environmental factors like air and moisture is called corrosion of metals.
    
49. What is rust chemically ?
    
         ANS : Chemically rust is a mixture of ferric oxide and ferric hydroxide.[Fe₂O₃.xH₂O].
    
50. What is galvanization ?
    
         ANS : The process of depositing a thin layer of zinc metal on iron is called galvanization.
    
51. What is an alloy ?
    
         ANS : An alloy is a homogeneous solid solution (mixture) of two or more metals or a metal and a nonmetal.
    
52. Mention the constituents of stainless steel.
    
         ANS : Iron, nickel and chromium are the constituents of stainless steel.
    
53. Which unit is used to express the purity of gold ?
    
         ANS : Carat is used to express the purity of gold.
    
54. Write the classification of elements.
    
         ANS : Elements are classified as metals, nonmetals amd semimetals (metalloids).
    
55. How can special type of steel be obtained ?
    
         ANS : Special type of steel can be obtained by heating iron red hot in absence of air with pieces of leather (animal skin).
    
56. In which forms of compounds is an ore obtained in nature ?
    
         ANS : An ore is obtained in the form of oxide, carbonate, sulphide, silicate, sulphate, etc in nature.
    
57. Dolomite is a mineral of which metal ?
    
         ANS : Dolomite is a mineral of calcium.
    
58. From where in India is the mineral of aluminium obtained ?
    
         ANS : The mineral of aluminium (bauxite) is obtained from the states of Bihar, Gujarat, Madhya Pradesh and Rajasthan.
    
59. What is the importance of turpentine oil in froth floatation process ?
    
         ANS : In froth floatation process the importance of turpentine oil is that it selectively wets ore particles making them lighter and it forms lather (froth) containing those particles which can be easily taken out.
    
60. Which metals are obtained in their molten state ?
    
         ANS : Metals obtained in molten state are tin, lead, bismuth, iron and aluminium.
    
61. Mention the type of electric charge on anode.
    
         ANS : The electric charge on anode is positive.
    
62. Write the equation of the reaction taking place on inert anode during electrolysis of molten NaCl.
    
         ANS :
    
         Cl^-_(l) → Cl + e^-
    
         Cl + Cl → Cl_2(g)
    
63. Which metals are used as semiconductors ?
    
         ANS : Silicon, boron and germanium are used as semiconductors.
    
64. Which metals are obtained in ultrapure condition by van Arkel's method ?
    
         ANS : Metals like germanium and uranium are obtained in ultrapure condition by van Arkel's method.
    
65. Write the principle of zone refining (fractional ultrapurification) method.
    
         ANS : The zone refining process uses the principle of fractional crystallization.
    
66. Which method is used to obtain pure aluminium from alumina ?
    
         ANS : Hall-haroult electrolytic method is used to obtain aluminium from alumina.
    
67. How can the comparison of reactivity of metals be done ?
    
         ANS : The comparison of reactivity of metalscan be done by the reaction of dilute HCl with different metals and observing the rate of evolution of hydrogen gas.
    
68. What will be the reaction when zinc metal is placed in a solution of copper sulphate ?
    
         ANS : When zinc metal is placed in a solution of copper sulphate the more reactive zinc displaces copper from its solution forming colourless solution of zinc sulphate containing brown granules of copper metal.
    
69. Write the equation of the reaction of sodium oxide with water.
    
         ANS :
    
              Na₂O_(s) + H₂O_(l) → 2NaOH_(aq)
    
70. Write an equation of the reaction between a metal and hydrochloric acid.
    
         ANS :
    
               Mg_(s) + 2HCl_(aq) → MgCl_2(aq) + H_2(g)
    
    OR
    
               2Al_(s) + 6HCl_(aq) → 2AlCl_3(aq) + 3H_2(g)
    
71. What is the chemical formula of rust ?
    
         ANS : The chemical formula of rust is Fe₂O₃,Fe(OH)₃ OR Fe₂O₃.xH₂O
    
72. What is galvanised iron ?
    
         ANS : Iron with its surface covered by a thin layer of zinc metal to protect it from being rusted is called galvanised iron.
    
73. What is anode (anodic) mud ?
    
         ANS : The impurities(less reactive metals) that settle down at the bottom of the anode during electrolytic refining of a metal are collectively called anode mud.