Chapter: Metals and Non-metals

Class X Science

Very Short Answer Type Questions [1 Mark]

1. A green layer is gradually formed on a copper plate left exposed to air for a week in a bathroom. What could this green substance be?
   Ans: It is due to the formation of basic copper carbonate \([CuCO_3.Cu(OH)_2]\).
2. A non-metal X exists in two different forms Y and Z. Y is the hardest natural substance, whereas Z is a good conductor of electricity. Identify X, Y and Z.
   Ans: ‘X’ is carbon, ‘Y’ is diamond as it is the hardest natural substance and ‘Z’ is graphite as it is a good conductor of electricity.
3. Metals generally occur in solid state. Name and write symbol of a metal that exists in liquid state at room temperature.
   Ans: Mercury (Hg) exists in liquid state at room temperature.
4. Which of the following two metals will melt at body temperature (37 °C)? Gallium, Magnesium, Caesium, Aluminium
   Ans: Gallium and Caesium.
5. From amongst the metals sodium, calcium, aluminium, copper and magnesium, name the metal (a) which reacts with water only on boiling, and (b) another which does not react even with steam.
   Ans: (a) Magnesium reacts with water only on boiling. (b) Copper does not react even with steam.
6. Which one of the following metals does not react with oxygen even at high temperatures? (a) Calcium (b) Gold (c) Sodium
   Ans: (b) Gold does not react with oxygen even at high temperatures.
7. Name any one metal which reacts neither with cold water nor with hot water, but reacts with heated steam to produce hydrogen gas.
   Ans: Iron; \(3Fe(s) + 4H_2O(g) \rightarrow Fe_3O_4(s) + 4H_2(g)\)
8. Why does calcium float in water?
   Ans: It is because hydrogen gas is formed which sticks to the surface of calcium, therefore it floats.
9. Name a non-metal which is lustrous and a metal which is non-lustrous.
   Ans: Iodine is a non-metal which is lustrous, lead is a non-lustrous metal.
10. Which gas is liberated when a metal reacts with an acid? How will you test the presence of this gas?
    Ans: Hydrogen gas is formed. Bring a burning matchstick near to it, \(H_2\) will burn explosively with a ‘pop’ sound.
11. Name the metal which reacts with a very dilute \(HNO_3\) to evolve hydrogen gas.
    Ans: Magnesium.
12. Name two metals which are found in nature in the free state.
    Ans: (i) Gold (ii) Silver.
13. What is the valency of silicon with atomic number 14?
    Ans: Its valency is equal to 4.
14. What is the valency of phosphorus with atomic number 15?
    Ans: Phosphorus has valency 3.
15. What is the valency of an element with atomic number 35?
    Ans: Its valency is 1.
16. Arrange the following metals in the decreasing order of reactivity: Na, K, Cu, Ag.
    Ans: K > Na > Cu > Ag.
17. An element forms an oxide, \(A_2O_3\) which is acidic in nature. Identify A as a metal or non-metal.
    Ans: ‘A’ is non-metal as non-metallic oxides are acidic in nature.

Short Answer Type Questions [I] [2 Marks]

19. Write one example of each of (i) a metal which is so soft that it can be cut with a knife and a non-metal which is the hardest substance. (ii) a metal and a non-metal which exist as liquid at room temperature.
    Ans: (i) Sodium, carbon (diamond). (ii) Mercury is liquid metal, bromine is liquid non-metal.
20. Mention the names of the metals for the following: (i) Two metals which are alloyed with iron to make stainless steel. (ii) Two metals which are used to make jewellery.
    Ans: (i) Nickel and chromium. (ii) Gold and platinum.
21. Give reason for the following: (a) School bells are made up of metals. (b) Electric wires are made up of copper.
    Ans: (a) It is because metals are sonorous, i.e., they produce sound when struck with a hard substance. (b) It is because copper is a good conductor of electricity.
22. Name the following: (a) A metal, which is preserved in kerosene. (b) A lustrous coloured non-metal. (c) A metal, which can melt while kept on palm. (d) A metal, which is a poor conductor of heat.
    Ans: (a) Sodium is preserved in kerosene. (b) Iodine is lustrous coloured non-metal. (c) Gallium. (d) Lead.
23. Explain why calcium metal after reacting with water starts floating on its surface. Write the chemical equation for the reaction. Name one more metal that starts floating after some time when immersed in water.
    Ans: Calcium starts floating because the bubbles of hydrogen gas formed stick to the surface of the metal.
    \(Ca(s) + 2H_2O(l) \rightarrow Ca(OH)_2 + H_2(g)\)
    Magnesium reacts with hot water and starts floating due to the bubbles of hydrogen gas sticking to its surface.
24. Give reason for the following: (a) Aluminium oxide is considered as an amphoteric oxide. (b) Ionic compounds conduct electricity in molten state.
    Ans: (a) It is because it reacts with acids as well as bases to produce salts and water. Al is a less electropositive metal. So, it forms an amphoteric oxide which can react with acid as well as base. (b) Ionic compounds can conduct electricity in molten state because ions become free to move in molten state.
25. Write two differences between calcination and roasting.
    Ans:

    Calcination	Roasting
    (i) It is carried out by heating ore in the absence of air.	(i) It is carried out by heating ore in the presence of air.
    (ii) It converts carbonate ores into oxides.	(ii) It converts sulphide ores into oxides.

26. The way metals like sodium, magnesium and iron react with air and water is an indication of their relative positions in the ‘reactivity series’. Is this statement true? Justify your answer with examples.
    Ans: Yes, sodium reacts explosively even with cold water, it is most reactive. Magnesium reacts with hot water, it is less reactive than Na. Iron reacts only with steam which shows it is least reactive among the three.
27. \(X + YSO_4 \rightarrow XSO_4 + Y\)
    \(Y + XSO_4 \rightarrow \text{No reaction}\)
    Out of the two elements, ‘X’ and ‘Y’, which is more reactive and why?
    Ans: ‘X’ is more reactive than ‘Y’ because it displaces ‘Y’ from its salt solution.
28. What is an alloy? State the constituents of solder. Which property of solder makes it suitable for welding electrical wires?
    Ans: Alloy is a homogeneous mixture of two or more metals (one of them can be a non-metal). Solder consists of lead and tin. It has a low melting point which makes it suitable for welding electrical wires.
29. Using the electronic configurations, explain how magnesium atom combines with oxygen atom to form magnesium oxide by transfer of electrons.
    Ans:
    Mg(12) = 2, 8, 2
    \(Mg \rightarrow Mg^{2+} + 2e^-\) (2, 8)
    O(8) = 2, 6
    \(O + 2e^- \rightarrow O^{2-}\) (2, 8)
    Formation: \((Mg)^{2+} (:{\ddot{O}}:)^{2-}\)
30. When a metal X is treated with cold water, it gives a base Y with molecular formula XOH (Molecular mass = 40) and liberates a gas Z which easily catches fire. Identify X, Y and Z.
    Ans: \(2Na + 2H_2O \rightarrow 2NaOH + H_2(g)\)
    ‘X’ is sodium (Na), ‘Y’ is sodium hydroxide (NaOH), ‘Z’ is \(H_2(g)\).
31. (a) Give two methods to prevent the rusting of iron. (b) Name the ores of the following metals: (i) mercury, and (ii) zinc.
    Ans: (a) (i) Painting (ii) Galvanisation. (b) (i) Cinnabar (ii) Zinc Blende.
32. Write chemical equations that show aluminium oxide reacts with acid as well as base.
    Ans: \(Al_2O_3 + 6HCl \rightarrow 2AlCl_3 + 3H_2O\)
    \(Al_2O_3 + 2NaOH \rightarrow 2NaAlO_2 + H_2O\)
33. Elements magnesium and oxygen respectively belong to group 2 and group 16 of the Modern Periodic Table. If the atomic numbers of magnesium and oxygen are 12 and 8 respectively, draw their electronic configurations and show the process of formation of their compound by transfer of electrons.
    Ans: Mg(12) = 2, 8, 2; O(8) = 2, 6. Magnesium loses 2 electrons to Oxygen. Formula: \(Mg^{2+} O^{2-}\).

Short Answer Type Questions [II] [3 Marks]

34. State three reasons for the following facts: (i) Sulphur is a non-metal (ii) Magnesium is a metal. One of the reasons must be supported with a chemical equation.
    Ans:

    Sulphur (Non-metal)	Magnesium (Metal)
    (i) Poor conductor of heat/electricity	(i) Good conductor of heat/electricity
    (ii) Neither malleable nor ductile	(ii) Malleable and ductile
    (iii) \(S + O_2 \rightarrow SO_2\); \(SO_2 + H_2O \rightarrow H_2SO_3\) (Acidic oxide)	(iii) \(2Mg + O_2 \rightarrow 2MgO\); \(MgO + H_2O \rightarrow Mg(OH)_2\) (Basic oxide)

35. What is cinnabar? How is metal extracted from cinnabar? Explain briefly.
    Ans: Cinnabar is HgS. Mercury is obtained by roasting cinnabar. HgO formed is thermally unstable and gives mercury. Mercury can be purified by distillation.
    \(2HgS(s) + 3O_2(g) \xrightarrow{heat} 2HgO(s) + 2SO_2(g)\)
    \(2HgO(s) \xrightarrow{heat} 2Hg(l) + O_2(g)\)
36. (a) Write the electron dot structures for potassium and chlorine. (b) Show the formation of KCl by the transfer of electrons. (c) Name the ions present in the compound, KCl.
    Ans: (a) K (2, 8, 8, 1) has 1 valence electron. Cl (2, 8, 7) has 7 valence electrons. (b) K loses 1 electron to Cl. (c) \(K^+\) and \(Cl^-\).
37. (a) State the electron-dot structure for calcium and sulphur. (b) Show the formation of CaS by the transfer of electrons. (c) Name the ions present in this compound CaS. Atomic number of Ca = 20, O = 16 (Note: Question says O=16 but asks about S=16).
    Ans: (a) Ca: 2, 8, 8, 2; S: 2, 8, 6. (b) Ca transfers 2 electrons to S. (c) \(Ca^{2+}\) and \(S^{2-}\).
38. You are given samples of three metals: Sodium, magnesium and copper. Suggest any two activities to arrange them in order of decreasing activity.
    Ans: Activity 1: Sodium reacts with cold water vigorously (\(2Na + 2H_2O \rightarrow 2NaOH + H_2\)). Magnesium does not react with cold water but with hot water. Hence Na > Mg.
    Activity 2: \(Mg + CuSO_4 \rightarrow MgSO_4 + Cu\). \(Cu + MgSO_4 \rightarrow\) No reaction. Hence Mg > Cu.
    Order: Na > Mg > Cu.
39. You are provided with magnesium ribbon and sulphur powder. Explain with the help of an activity that metal oxides are basic and non-metal oxides are acidic in nature.
    Ans: Burn magnesium to get ash (MgO), dissolve in water, it turns red litmus blue (Basic). Burn sulphur, collect gas (\(SO_2\)), dissolve in water (\(H_2SO_3\)), it turns blue litmus red (Acidic).
40. Suggest a method of reduction for the following metals during their metallurgical processes: (i) metal ‘A’ which is one of the last, second or third position in the reactivity. (ii) metal ‘B’ which gives vigorous reaction even with water and air. (iii) metal ‘C’ which is kept in the middle of activity series.
    Ans: (i) ‘A’ can be obtained by heating alone or chemical reduction (e.g., Hg). (ii) ‘B’ can be obtained by electrolytic reduction. (iii) ‘C’ can be reduced by reducing agent like ‘C’ or ‘Al’.
41. (a) Explain the formation of ionic compound CaO with electron dot structure. (b) Name the constituent metals of bronze.
    Ans: (a) Ca (2,8,8,2) loses 2 electrons, O (2,6) gains 2 electrons. Forms \(Ca^{2+}\) and \(O^{2-}\). (b) Bronze is made of copper and tin.
42. A metal ‘X’ acquires a green colour coating on its surface on exposure to air. (i) Identify the metal ‘X’ and name the process. (ii) Name and write chemical formula of the green coating. (iii) List two important methods to prevent the process.
    Ans: (i) Copper; Corrosion. (ii) Basic copper carbonate \([CuCO_3.Cu(OH)_2]\). (iii) Coating with tin; Alloying.
43. Write balanced equations for the reaction of: (i) aluminium when heated in air. (ii) iron with steam. (iii) calcium with water.
    Ans: (i) \(4Al + 3O_2 \xrightarrow{heat} 2Al_2O_3\)
    (ii) \(3Fe + 4H_2O(steam) \rightarrow Fe_3O_4 + 4H_2\)
    (iii) \(Ca + 2H_2O \rightarrow Ca(OH)_2 + H_2\). Bubbles stick to the surface causing floatation.
44. Write balanced chemical equations for: (a) Dilute sulphuric acid reacts with aluminium powder. (b) Dilute hydrochloric acid reacts with sodium carbonate. (c) Carbon dioxide is passed through lime water.
    Ans: (a) \(2Al + 3H_2SO_4(dil) \rightarrow Al_2(SO_4)_3 + 3H_2\)
    (b) \(Na_2CO_3 + 2HCl \rightarrow 2NaCl + H_2O + CO_2\)
    (c) \(Ca(OH)_2 + CO_2 \rightarrow CaCO_3 + H_2O\)
45. What is meant by ‘rusting’? With labelled diagrams, describe an activity to find out the conditions under which iron rusts.
    Ans: Rusting is the formation of hydrated ferric oxide (\(Fe_2O_3.xH_2O\)) on iron in presence of moisture and air. Activity: Tube A (Air+Water) -> Rusts. Tube B (Boiled water+Oil, no air) -> No rust. Tube C (Dry air, \(CaCl_2\)) -> No rust. Conclusion: Air and water both required.
46. (a) Show the formation of \(Na_2O\) by electron transfer. (b) Why are ionic compounds hard? (c) Why do they conduct electricity in molten state but not solid?
    Ans: (a) 2 Na atoms each lose 1 electron to 1 O atom. (b) Strong inter-ionic attraction. (c) Ions are free to move in molten state but fixed in solid state.
47. (a) Show transfer of electrons for MgO. (b) Solvent for ionic compounds? (c) Why aqueous solutions conduct?
    Ans: (a) Mg loses 2e, O gains 2e. (b) Water. (c) Aqueous solutions contain free ions.
48. What are amphoteric oxides? Choose from: \(Na_2O, ZnO, Al_2O_3, CO_2, H_2O\).
    Ans: Oxides reacting with both acids and bases. Examples: \(ZnO\), \(Al_2O_3\) (Note: Source text has a typo listing Na2O, but standard answer is ZnO and Al2O3).
49. Define: (i) mineral (ii) ore (iii) gangue.
    Ans: (i) Mineral: Naturally occurring substance with metal. (ii) Ore: Mineral from which metal is extracted profitably. (iii) Gangue: Impurities in ore.
50. An ore produces \(SO_2\) on heating. Concentration process? Steps to convert to metal?
    Ans: Concentration: Froth-floatation. Steps: (i) Roasting (heating in air) to form oxide. (ii) Reduction of oxide to metal (using Carbon).
51. Give reasons: (i) Ionic compounds have high MP. (ii) Highly reactive metals not reduced by carbon. (iii) Copper vessels get green coat.
    Ans: (i) Strong inter-ionic attraction. (ii) They have higher affinity for oxygen than carbon. (iii) Corrosion forming basic copper carbonate.
52. State reasons: (i) Shining metals become dull. (ii) Zn + dil \(HNO_3\) no \(H_2\). (iii) Metal sulphides in rocks, halides in sea.
    Ans: (i) Corrosion/Surface oxidation. (ii) \(HNO_3\) is strong oxidising agent (oxidises \(H_2\) to water). (iii) Solubility differences (Halides soluble, wash to sea).
53. State reasons: (i) Electric wires covered with rubber. (ii) Zn displaces H from HCl, Cu does not. (iii) Sulphide ore converted to oxide first.
    Ans: (i) Insulation/Safety. (ii) Zn is more reactive than H; Cu is less reactive than H. (iii) Reduction of oxide is easier than sulphide.

Long Answer Type Questions [5 Marks]

54. (a) Electron dot for Cl and Ca. Formation of \(CaCl_2\). (b) Nature and physical properties.
    Ans: (a) Ca transfers 2 electrons (one to each Cl). Formula \(CaCl_2\). (b) Ionic compound. Properties: Hard/Solid, High MP/BP, Soluble in water.
55. (a) Ore gives brisk effervescence with HCl. Type? Steps to extract. (b) Copper coin in \(AgNO_3\).
    Ans: (a) Carbonate ore. Steps: Calcination (heat without air) -> Oxide -> Reduction (with C). (b) \(Cu + 2AgNO_3 \rightarrow Cu(NO_3)_2 + 2Ag\). Solution turns blue, silver deposits.
56. (a) Define activity series. Arrange Au, Cu, Fe, Mg increasing order. (b) Observation: (i) Zn in \(CuSO_4\). (ii) Ag in \(FeSO_4\).
    Ans: (a) Arrangement of metals by decreasing reactivity. Au < Cu < Fe < Mg. (b) (i) Blue colour fades, reddish-brown Cu deposits (Zn displaces Cu). (ii) No reaction (Ag less reactive than Fe).
57. (a) Chemical name of coating on Silver and Copper corrosion. (b) Galvanisation? (c) Alloy definition. Steel/Stainless steel constituents.
    Ans: (a) Silver: \(Ag_2S\) (Silver sulphide). Copper: \(CuCO_3.Cu(OH)_2\). (b) Coating iron with zinc to prevent rust. (c) Alloy: Homogeneous mixture. Steel (Fe+C), Stainless Steel (Fe+Ni+Cr).
58. (a) Roasting vs Calcination. Zn extraction. (b) Metals to reduce oxides.
    Ans: (a) Roasting: Heating sulphide ore in air (\(2ZnS + 3O_2 \rightarrow 2ZnO + 2SO_2\)). Calcination: Heating carbonate ore without air (\(ZnCO_3 \rightarrow ZnO + CO_2\)). Reduction: \(ZnO + C \rightarrow Zn + CO\). (b) Al, Mg.
59. (a) A loses 2e, B gains 1e. Formula? (b) \(MgCl_2\) formation. (c) NaCl conduction. (d) NaCl MP.
    Ans: (a) Ionic bond. \(AB_2\). (b) Mg transfers 2e to two Cl atoms. (c) Conducts in molten/solution due to free ions. (d) High MP due to strong electrostatic attraction.
60. (a) Carbon not used for Mg? (b) Na extraction. (c) Cu extraction from sulphide.
    Ans: (a) Mg has high affinity for O. (b) Electrolysis of molten NaCl. (c) Roasting (\(2Cu_2S + 3O_2 \rightarrow 2Cu_2O + 2SO_2\)) then \(2Cu_2O + Cu_2S \rightarrow 6Cu + SO_2\).
61. Extraction of metals high up vs middle. Sodium extraction.
    Ans: High up: Electrolytic reduction (cannot use C). Middle: Chemical reduction (use C). Sodium: Electrolysis of molten chloride. Cathode: Na, Anode: \(Cl_2\).
62. Reactive metals K, Na reacting with halogen. Properties.
    Ans: Form Ionic compounds (e.g., NaCl, KCl). Properties: High MP, Soluble in water, Conduct in molten state, Hard solids.
63. Metal M (Copper) extraction from \(M_2S\). Electrolytic refining.
    Ans: (i) Copper. (ii) Roasting then self-reduction (Bessemerisation). (iii) Anode: Impure Cu, Cathode: Pure Cu, Electrolyte: \(CuSO_4\). Pure Cu deposits on cathode.
64. (i) Corrosion of Ag/Cu. (ii) Tamarind cleaning. (iii) Al corrosion resistance.
    Ans: (i) Ag -> \(Ag_2S\) (Black), Cu -> Basic Carbonate (Green). (ii) Acid in tamarind neutralizes/dissolves basic carbonate layer. (iii) Al forms protective oxide layer (\(Al_2O_3\)).
65. (a) Electron dot Na, O, Mg. (b) \(Na_2O\), MgO formation. (c) Properties.
    Ans: (c) Solid/Hard, Soluble in water, Conduct electricity in solution/molten.
66. Alloys. Brass, Bronze, Solder.
    Ans: Mixture of metals. Brass (Cu+Zn), Bronze (Cu+Sn), Solder (Pb+Sn).
67. Metal E (stored in kerosene) = Na. Reactions.
    Ans: \(4Na + O_2 \rightarrow 2Na_2O\). \(Na_2O + H_2O \rightarrow 2NaOH\). Extraction: Electrolysis of molten chloride.
68. (a) Mercury ore (Cinnabar). Extraction. (b) Thermite reaction. (c) High reactivity extraction.
    Ans: (a) Roast HgS to HgO, then heat HgO to Hg. (b) Reaction of \(Fe_2O_3\) with Al to produce molten iron for welding rails. (c) Electrolytic reduction.
69. (a) Top reactivity extraction (Al). (b) Alloys (Steel, Brass).
    Ans: (a) Electrolysis of bauxite. (b) Steel (Fe+C), Brass (Cu+Zn).
70. Ionic compound formation. Properties.
    Ans: Transfer of electrons. Properties: High MP, Soluble in water, Conduct in molten.
71. (a) X (Low) -> Chemical reduction. Y (High) -> Electrolytic. (b) NaCl formation. (c) Na in water.
    Ans: (c) Catches fire, Forms alkali (turns red litmus blue).
72. (a) Reaction of X (Al) with \(Fe_2O_3\). (b) \(Al_2O_3\) amphoteric. (c) Bronze constituents.
    Ans: (a) \(Fe_2O_3 + 2Al \rightarrow Al_2O_3 + 2Fe + Heat\). (b) Reacts with HCl and NaOH. (c) Cu + Sn.
73. Reaction of A (Al) + B (\(Fe_2O_3\)).
    Ans: Thermite reaction. Displacement and Redox reaction. Products: Molten Iron and \(Al_2O_3\).
74. (a) Corrosion & Prevention (Galvanisation). (b) Extraction of Middle metal M (Sulphide ore).
    Ans: (b) Concentration -> Roasting (\(2MS + 3O_2 \rightarrow 2MO + 2SO_2\)) -> Reduction (\(MO + C \rightarrow M + CO\)) -> Refining.
75. (a) Ionic vs Covalent properties. (b) Extraction M (Middle) vs N (High).
    Ans: (a) Ionic: Strong force, Soluble in water, Conducts. Covalent: Weak force, Insoluble, No conduction. (b) M: Reduction by C/Al. N: Electrolytic reduction.