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CHAPTER = Metals produce ba: k3) Metals and Non-Metals CHAPTER AT A GLANCE Elements can be classified as metals and non-metals. Metals are lustrous, sonorous, malleable, ductile and good conductors of heat and electricity. They are solid at room temperature except mercury, which is a liquid. = Non-metals are non-lustrous, soft, brittle, neither malleable nor ductile, non-sonorous and poor conductors of heat and electricity. oxides whereas non-metals produce acidic oxides or amphoteric oxides. = Almost all metals combine with oxygen to form metal oxides. These metal oxides are basic and form salts with acids. They give alkaline solutions in water. = Different metals have different reactivities with water and dilute acids. = A list of common metals arranged in the increasing order of their reactivity is known as activity series. = Amore reactive metal displaces a less reactive metal from its salt solution. = Metals and non-metals react with each other forming ionic compounds in which electrons are transferred from the valence shell of a metal atom to the valence of a non-metal atom. "During the formation of an ionic compound, the metal atom becomes cation and the non-metal atom becomes anion. The cation and anion are held together by strong electrostatic force of attraction called ionic bond. = The ionic compounds exist as ions; have high melting and boiling points, are soluble in water but insoluble in organic solvents. They do not conduct electric current in the solid state but conduct electric current in the molten or dissolved state. = Metals occur in nature in free as well as combined state. = Elements or compounds that occur naturally in the earth’s crust are called minerals. = Minerals from which a metal can be extracted economically are called ores. = The extraction of a metal from its ores is done on the basis of reactivity of the metal. = Most reactive metals are extracted by electrolytic reduction of their molten ores. = Least reactive metals are extracted by heating their oxides. = Metals of medium reactivity are extracted by converting the ore into metal oxide, which is then reduced to the metal by heating with a suitable reducing agent. = Metals react with air and moisture on their surfaces and their surfaces get corroded. This process is called corrosion. The corrosion in case of iron is called rusting. = Rusting can be prevented by painting, oiling, greasing and electroplating. NCERT IN-TEXT QUESTIONS Page 40 1. Give an example of a metal which: (i) is a liquid at room temperature. (ii) can be easily cut with a knife. (iii) is the best conductor of heat. (iv) is a poor conductor of heat. Ans. (i) Mercury (ii) Sodium (iii) Silver (iv) Lead 2. Explain the meaning of malleable and ductile. Ans. Malleable: A substance is said to be malleable if it can be beaten into sheets for example, metals are malleable. Ductile: A substance is said to be ductile if it can be drawn into wires. for example, metals are ductile. Page 46 1. Why does sodium kept immersed in kerosene oil? Ans. Sodium metal is highly reactive. If itis kept open, it can explosively react with oxygen and moisture present in the air. To prevent this explosive reaction and the after effects, sodium is kept immersed in kerosene oil. 2. Write equation for the reactions of: (i) iron with steam (ii) calcium and potassium with water. Ans. (i) Fe + 3H,O—> Fe(OH), + 3H, (ii) Ca + 2H,O—> Ca(OH), + H,; 2K + 2H,O —> 2KOH + H, Ans. (i) Electron-dot structures for sodium, oxygen and magnesium are: Na’ :0: Mg: (ii) Formation of Na,O Naa «a 7 XX + + OX —> (Na’), [:0%*] or Na,O Na ~_” Formation of MgO Mg +,Q* > [MsI* :0=]* or MgO (iii) Ions present in these compounds are: Na* and O* ; Mg”* and O* 2. | Why do ionic compounds have high melting points? Ans. Ionic compounds have strong electrostatic forces of attraction between oppositely charged ions. A considerable amount of energy is required to break these forces of attraction. Thus, ionic compounds they have high melting points. Page 53 1. Define the terms: (a) mineral (b) oreand (c) gangue Ans. (a) Mineral: The free or combined states of elements naturally occurring in the earth’s crust are called minerals. (b) Ore: An ore is a mineral from which a metal can be extracted conveniently and economically. (c) Gangue: The earthy impurities such as sand, lime stone, rocks etc. associated with minerals are collectively known as gangue or matrix. 2. Name two metals which are found in nature in the free state. Ans. Gold and platinum 3. | What chemical process is used for obtaining a metal from its oxide? Ans. Reduction process Page 55 1. Metallic oxides of zinc, magnesium and copper were heated with the following metals: Metal Zine Magnesium Copper Zinc oxide Magnesium oxide Copper oxide In which cases will you find displacement reactions taking place? Ans. Metal Zinc Magnesium Copper Zinc oxide No reaction Displacement | No reaction Magnesium oxide |No reaction |Noreaction | No reaction Copper oxide Displacement | Displacement | No reaction Zinc can displace copper from copper oxide. Zn + CuO — >» ZnO + Cu Magnesium can displace zinc and magnesium from zinc oxide and magnesium oxide respectively. Mg + ZnO —»> MgO + Zn Mg + CuO —» ZnO + Cu 2. | Which metals do not corrode easily? Ans. Less reactive metals that are not attacked by air and moisture don’t corrode easily. 3. | What are alloys? Ans. Alloys are the homogeneous mixtures of two or more metals or metals and non-metals. NCERT TEXTBOOK EXERCISES 1. Which of the following pairs will give displacement reactions? (a) NaCl solution and copper metal (b) MgCl, solution and aluminium metal (c) FeSO, solution and silver metal (d) AgNO, solution and copper metal Ans. (d) AgNO, solution and copper metal 2. Which of the following methods is suitable for preventing an iron frying pan from rusting? (a) applying grease (b) applying paint (c) applying a coating of zinc —_(d) All of these Ans. (c) applying a coating of zinc 3. Anelement reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be: (a) calcium (b) carbon (c) silicon (d) iron Ans. (a) calcium 4. Food cans are coated with tin and not with zinc because: (a) zinc is costlier than tin (b) zinc has a higher melting point than tin 9. Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it as shown in figure. +— Test Tube 4— Spatula containing sulphur powder +— Bumer (a) What will be the action of gas on (i) dry litmus paper? (ii) moist litmus paper? (b) Write a balanced chemical equation for the reaction taking place. Ans. (a) (i) No action (ii) It turns moist blue litmus paper red. (b) $+O,—»80, 10. State two ways to prevent the rusting of iron. Ans. The rusting of iron can be prevented by: (1) preventing the contact of iron surface with air and moisture by painting, oiling or greasing. (2) by coating the iron surface with a more reactive element like zinc. This is called galvanisation. 11. What type of oxides are formed when non-metals combine with oxygen? Ans. Non-metals form two types of oxides. (a) Neutral oxides such as CO, NO etc. (b) Acidic oxides such as SO,, CO, etc. 12. Give reasons: (a) Platinum, gold and silver are used to make jewellery. (b) Sodium, potassium and lithium are stored under oil. (c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking. Ans. 13. (d) (a (a) Carbonate and sulphide ores are usually converted into oxides during the process of extraction. Platinum, gold and silver are used to make jewellery because they have low reactivity and are not attacked by air and moisture. They don’t undergo corrosion and retain their lustre for a long time. Also these metals are highly malleable and ductile. Sodium, potassium and lithium are highly reactive and their reactions with air and moisture are highly explosive. To prevent these explosive reactions, these metals are stored under oil. This is due to the reason that a thin oxide layer of aluminium is formed on its surface which prevents the further oxidation of metal. The oxide layer is stable even at high temperatures. Also aluminium is a good conductor of heat. This is because it is easier to obtain a metal from its oxide as compared to its sulphide or carbonate. You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels. Ans. Incase of a tarnished copper vessel, there is a layer of basic copper carbonate. This basic layer can be cleaned by using sour substances such as lemon or tamarind juice which are acidic in nature and can dissolve the basic coating of copper carbonate. 14. Differentiate between metal and non-metal on the basis of their chemical properties. Metals Non-Metals They form basic oxides. They from acidic oxides. They displace hydrogen from dilute acids. They don’t displace hydrogen from dilute acids. Usually they don’t combine with hydrogen. Only a few reactive metals combine with hydrogen to form metal hydroxide, which are electrovalent compounds. They react with hydrogen to form hydrides which are covalent compounds. They react with chlorine to form electrovalent chlorides. They react with chlorine to form covalent chlorides. 15. A man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he 5. Which of the following oxide(s) of iron would be obtained on prolonged reaction of iron with steam? (a) Fe,O, and Fe,O, (b) FeO (c) Fe,O, (d) Fe,O, 6. What happens when calcium is treated with water? (i) It does not react with water (ii) It reacts violently with water (iii) It reacts less violently with water (iv) Bubbles of hydrogen gas formed stick to the surface of calcium (a) (ii) and (iii) (b) (i) and (ii) (c) (i) and (iv) (d) (iii) and (iv) 7. Generally metals react with acids to give salt and hydrogen gas. Which of the following acids does not give hydrogen gas on reacting with metals (except Mn and Mg)? (a) HCl (b) HSO, — (©) HNO, (d) all of these 8. The composition of aqua-regia is: (a) dil, HCl: dil. HNO, 3 : 1 (b) dil. HCl : conc. HNO, 3 a a (c) cone. HCl : cone. HNO, 3 = 4 (d) cone.HCl : dil. HNO, 3 3 1 9. | Which of the following are not ionic compounds? (i) KC (i) HCL (iii) CCL, (iv) NaCl (a) (i) and (iii) (b) (ii) and (iii) (c) (iii) and (iv) (d) (i) and (ii) 10. Which one of the following properties is not generally exhibited by ionic compounds? (a) electrical conductivity in molten state (b) electrical conductivity in solid state (c) solubility in water (d) high melting and boiling points 11. Which of the following metals exist in their native state in nature? (i) Cu (ii) Au (iii) Zn (iv) Ag (a) (ii) and (iii) (b) (iii) and (iv) (c) (ii) and (iv) (d) (i) and (ii) 12. 13. 14. 15. 16. 17. 18. 19. 20. 21, Metals are refined by using different methods. Which of the following metals are refined by electrolytic refining? (i) Au (ii) Cu (iii) Na (iv) K (a) (i) and (ii) (b) (iii) and (c) (i) and (iii) (d) (ii) and (iii) Silver articles become black on prolonged exposure to air. This is due to the formation of: (a) Ag,S and Ag,N (b) Ag,N (C) Ag,S (d) Ag,O Galvanisation is a method of protecting iron from rusting by coating with a thin layer of: (a) silver (b) gallium (c) zinc (d) aluminium Stainless steel is very useful material for our life. In stainless steel, iron is mixed with: (a) Niand Cr (b) Niand Cu (c) Cuand Au (d) Cuand Cr If copper is kept open in air, it slowly loses its shining brown surface and gains a green coating. It is due to the formation of: (a) Cu(NO,), (b) CuCO, = (c) CuO (d) CuSO, Generally, metals are solid in nature. Which one of the following metals is found in liquid state at room temperature? (a) Fe (b) Cr (c) Na (d) Hg Which of the following metals are obtained by electrolysis of their chlorides in molten state? (i) Na (ii) Ca (iii) Fe (iv) Cu (a) (iii) and (iv) (b) (i) and (iii) (c) (i) and (iv) (a) (i) and (ii) Generally, non-metals are not lustrous. Which of the following non-metal is lustrous? (a) oxygen (b) nitrogen (c) sulphur (d) iodine Which one of the following four metals would be displaced from the solution of its salts by other three metals? (a) Cu (b) Ag (c) Mg (d) Zn 2 ml each of concentrated HCl, HNO, and a mixture of concentrated HCI and concentrated HNO, in the ratio of 3:1 were taken in test tubes labelled as A, B and C. A small piece of metal was put in each test tube. No change occurred in test tubes A and B but the metal got dissolved in test tube C. The metal could be: (a) Pt (b) Au (c) Al (a) Cu 30. 31. 32. 33. 34, 35. 36. Cathode The electronic configurations of three elements X, Y and Z are X — 2,8: Y — 2,8,7 and Z — 2, 8,2. Which of the following is correct? (a) Zis a non-metal (b) Xis a metal (c) Y isa metal (d) Y is anon-metal and Z isa metal Although metals form basic oxides, which of the following metals form an amphoteric oxide? (a) Cu (b) Na (c) Al (d) Ca Generally, non-metals are non-conductors of electricity. Which of the following is a good conductor of electricity? (a) fullerene (b) graphite (c) diamond (da) sulphur Electrical wires have a coating of an insulating material. The material, generally used is: (a) graphite (b) sulphur (c) PVC (d) all can be used Which of the following non-metals is a liquid? (a) carbon (b) bromine (c) sulphur (d) phosphorus Which of the following can undergo a chemical reaction? (a) MgSO, + Pb (b) MgSO, + Fe (c) ZnSO, + Fe (d) CuSO, + Fe Which one of the following figures correctly describes the process of electrolytic refining? Cathode —» — Anode Anode—+ Cathode Acidified Cuso, Acidified solution Cuso, solution | Impurities Impurities Anode Cathode Anode Acidified Acidified CuSO, CuSO, solution solution Impurities Lees} — Impurities () (4) Answers: 1. 4. 7. 9. 10. 11. 14. 17. 20. 22. 24. 26. 27. 28. 30. 32. 35. (c) dullness 2. (b) conductivity 3. (d) (i) and (iv) (d) Fe 5. (c) Fe,O, 6. (d) (iii) and (iv) (c) HNO, 8. (c) conc. HCl : cone. HNO, 38 1 (b) (ii) and (iii) (b) electrical conductivity in solid state (c) (ii) and (iv) 12. (a) (i)and (ii) 13. (c) Ag,S (c) zine 15. (a) Niand Cr 16. (b) CuCO, (a) Hg 18. (d) (i) and (ii) 19. (a) iodine (b) Ag 21. (b) Au (c) a homogeneous mixture 23. (b) (iii) and (iv) (a) deposited on cathode 25. (b) Na (d) steel (b) it reacts with cold water to form magnesium oxide and evolves hydrogen gas (d) zinc amalgam 29. (b) has low melting point (d) Y is anon-metal and Z is a metal 31. (c) Al (b) graphite 33. (c) PVC 34. (b) bromine (d) CuSO, + Fe 36. (c) Short Answer Type Questions 37. Ans. 38. Iqbal treated a lustrous, divalent element M with sodium hydroxide. He observed the formation of bubbles in reaction mixture. He made the same observations when this element was treated with hydrochloric acid. Suggest how he can identify the produced gas. Write chemical equations for both the reactions. The produced gas is H,. It can be identified by bringing a burning match stick near the reaction vessel, as a result of which, a pop sound is produced M + 2NaOH — > NaMO, + H, M +. 2HCl — MC, + H, The element M is a metal. During extraction of metals, electrolytic refining is used to obtain pure metals. (a) Which material will be used as anode and cathode for refining of silver metal by this process? (b) Suggest a suitable electrolyte also. (c) In this electrolytic cell, where do we get pure silver after In this el lytic cell, where di get p il f passing electric current? Ans. Solder is an alloy of lead and tin. Because of its low melting point, it is suitable for welding electrical wires. 46. A metal A, which is used in thermite process, when heated with oxygen gives an oxide B, which is amphoteric in nature. Identify A and B. Write down the reactions of oxide B with HCI and NaOH. Ans. A is aluminium and B is Al,O,,. ALO, +6HCl =—~» 2AlCl, + 3H,O ALO, + 2NaOH —> 2NaAlO, + H,O 47. A metal that exists as a liquid at room temperature is obtained by heating its sulphide in the presence of air. Identify the metal and its ore and give the reaction involved. Ans. Mercury is the only metal that exists as liquid at room temperature. It can be obtained by heating cinnabar (Hg§), the sulphide ore of mercury. The reaction involved is: 2HgS + 30, —> 2Hg + 250, 48. Give the formulae of the stable binary compounds that would be formed by the combination of following pairs of elements. (a) Mg and N, (b) Liand O, (c) Aland Cl, (d) K and O,. Ans. (a) Mg.N, (b) Li,O () AICI, (d) KO 49. What happens when (a) ZnCO, is heated in the absence of oxygen? (b) a mixture of Cu,O and Cu;S is heated? Ans. (a) It undergoes calcination. The chemical reaction can be given as ZnCO, —» ZnO + CO, (b) It undergoes auto reduction forming copper and sulphur dioxide 2Cu,O + Cu,S —~» 6Cu + SO, 50. Anon-metal A is an important constituent of our food and forms two oxides B and C. Oxide B is toxic whereas C causes global warming. (a) Identify A, B and C. (b) To which group of periodic table does A belong? Ans. (a) A is carbon, B is carbon monoxide and C is carbon dioxide. (b) A belongs to Group - 14 of the periodic table. 51. 52. Ans. 53. Ans. 54. Ans. 55. Ans. 56. Ans. 57. Ans. Give two examples each of the metals that are good conductors and poor conductors of heat respectively. (a) Good conductors of heat: silver and copper (b) Poor conductors of heat: lead and mercury Name one metal and one non-metal that exist in liquid state at room temperature. Also name two metals having melting point less than 310 K (37°C). Metal: Mercury (Hg); Non-metal: Bromine (Br) Two metals with melting points less than 310 K are cesium (Cs) and gallium (Ga). An element A reacts with water to form a compound B which is used in white washing. The compound B on heating forms an oxide C which on treatment with water gives back B. Identify A, B and C and give the reactions involved. A is Ca, B is Ca(OH), and C is CaO. Ca(s) + 2H,O —» Ca(OH),(aq) + H,(g) Ca(OH), —» CaO + H,O Analkali metal A gives a compound B (molecular mass = 40) on reacting with water. The compound B gives a soluble compound C on treatment with aluminium oxide. Identify A, B and C and give the reaction involved. A is Na, B is NaOH and C is NaAlO,. 2Na + 2H,O —-» 2NaOH + H, ALO, + 2NaOH —> 2NaAlO, + H,O Give the reaction involved during extraction of zinc from its ore by: (a) roasting of zinc ore (b) calcination of zinc ore. (a) 2ZnS(s) + 30, —» 2ZnO(s) + 2SO,(g) (b) ZnCO,(s) —> ZnO(s) + CO,(g) A metal M does not liberate hydrogen from acids but reacts with oxygen to give a black colour product. Identify M and black coloured product and also explain the reaction of M with oxygen. M is copper and the black product is CuO. 2Cu + O, —» 2CuO An element A forms an oxide A,O, which is acidic in nature. Identify A as a metal or non-metal. Since the oxide of the element A is acidic, it is a non-metal. (c) NaClis not a conductor of electricity in solid state whereas it does conduct electricity in aqueous solution as well as in molten state. (d) Iron articles are galvanised. (e) Metals like Na, K, Ca and Mg are never found in their free state in nature. Ans. (a) It is due to the formation of a layer of oxide Al,O, on the surface of it. (b (Cc Na or Mg is more reactive as compared to carbon. In solid NaCl, the movement of ions is not possible due to the strong electrostatic forces of attraction between the oppositely charged ions. However, in aqueous or molten state, the ions can move freely and conduct electricity. (d To protect them from rusting, iron articles are coated with a layer of zinc by galvanisation. (e) It is so because these metals are highly reactive. 62. (i) Given below are the steps for extraction of copper from its ore. Write the reactions involved. (a) Roasting of copper (I) sulphide. (b) Reduction of copper (I) oxide with copper (I) sulphide. (c) Electrolytic refining. (ii) Draw a neat and well labelled diagram for electrolytic refining of copper. Ans. (i) (a) 2Cu,S(s) + 30,(s) —» 2Cu,O(s) + 250,(g) (b) 2Cu,O(s) + Cu,S(s) —» 6Cu(s) + SO,(g) (c) At cathode: Cu*(aq) + 2e°- —» Cu(s) At anode: Cu(s) —» Cu**(aq) + 2° Diagram for electrolytic refining of copper Key e = |+ e + + Cathode —+ Anode cu" Acidified copper : sulphate Gs solution Tank Impurities (anode mud) 63. Ans. 64. Ans. 65. Ans. Of the three metals X, Y and Z, X reacts with cold water, Y with hot water and Z with steam only. Identify X, Y and Z and also arrange them in the increasing order of reactivity. X is an alkali metal like Na or K, Y is an alkaline earth metal like Mg or Ca and Z is Fe. Increasing order of reactivity: Na or K > Mg or Ca > Fe An element A burns with golden flame in air. It reacts with another element B with atomic number 17 to give a product C. An aqueous solution of product C on electrolysis gives a compound D and liberates hydrogen. Identify A, B, C and D. Also write down the equations for the reactions involved. A is Na, B is Cl,, C is NaCl and D is NaOH. 2Na+Cl, ——» 2NaCl 2NaCl(aq) + 2H,O(!) ——» 2NaOH(aq) + CL(g) + H,(g) Two ores A and B were taken. On heating, ore A gives CO, whereas, ore B gives SO,. What steps will you take to convert them into metals? Since ore A gives CO, and ore B gives SO,. Therefore, these ores are MCO, and MS respectively. Metal M can be obtained from A as shown below: MCO, » MO+CO, MO+C —»+ M+CO Metal M can be obtained from B as given below: 2MS + 30, ——» 2MO + 2SO, MO+C —» M+CO 
