METALS AND NON-METALS, Summaries of Chemistry

Download METALS AND NON-METALS and more Summaries Chemistry in PDF only on Docsity! Prepared by: M. S. KumarSwamy, TGT(Maths) Page - 1 - METALS AND NON-METALS 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? Answer. It is due to the formation of basic copper carbonate [CuC03.Cu(0H)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. Answer. ‘X’ is carbon, ‘Y’ is diamond as it is the hardest natural substance and ‘Z’ is graphite as it is 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. Answer. 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 Answer. 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. Answer. (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 Answer. (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. Answer. Iron; 3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g) 8. Why does calcium float in water? Answer. It is because hydrogen gas is formed which sticks to surface of calcium, therefore it floats. 9. Name a non-metal which is lustrous and a metal which is non-lustrous. Answer. 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? Answer. Hydrogen gas is formed. Bring a burning matchstick near to it, H2 will burn explosively with ‘pop’ sound. 11. Name the metal which reacts with a very dilute HNO3 to evolve hydrogen gas. Answer. Magnesium 12. Name two metals which are found in nature in the free state. Answer.(i) Gold (ii) Silver 13. What is the valency of silicon with atomic number 14? Answer. Its valency is equal to 4. 14. What is the valency of phosphorus with atomic number 15? Answer. Phosphorus has valency 3. 15. What is the valency of an element with atomic number 35? Answer. Its valency is 1. 16. Arrange the following metals in the decreasing order of reactivity: Na, K, Cu, Ag. Answer. K > Na > Cu > Ag 17. An element forms an oxide, A2O3 which is acidic in nature. Identify A as a metal or non- metal. Answer. ‘A’ is non-metal as non-metallic oxides are acidic in nature. Prepared by: M. S. KumarSwamy, TGT(Maths) Page - 2 - 18. 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 ? Answer. It is due to the formation of basic copper carbonate [CuCO3.Cu(OH)2]. 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 knife and a non-metal which is the hardest sustance. (ii) a metal and a non-metal which exist as liquid at room temperature. Answer. (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 jewellary. Answer. (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. Answer. (a) It is because metals are sonorous, i.e. they produce sound when struk with a hard substance. (b) It-is because copper is 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. Answer. (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. Answer. Calcium starts floating because the bubbles of hydrogen gas formed stick to the surface of metal. 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. Answer. (a) It is because it reacts with acids as well as bases to produce salts and water.’Al’ is less electropositive metal. So, it forms 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. Prepared by: M. S. KumarSwamy, TGT(Maths) Page - 5 - Answer. 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. Answer. 38. You are given samples of three metals. Sodium, magnesium and copper. Suggest any two activities to arrange them in order of decreasing activity. Answer. Activity 1: Sodium reacts with cold water vigorously to form sodium hydroxide and hydrogen gas Magnesium does not react with cold water but with hot water to form magnesium ! hydroxide and hydrogen gas. Hence sodium is more reactive than magnesium. 39. You are provided with magnesium ribbon and sulpher powder. Explain with the help of an activity that metal oxides are basic and non-metal oxide are acidic in nature. Answer. Aim: To test the nature of oxides formed by metals and non-metals. Materials Required: Sulphur powder, Mg ribbon, water, blue litmus paper, red litmus paper. Procedure: 1.Take magnesium ribbon with a pair of tongs and burn it in flame in the presence of air. 2.Collect the product formed and dissolve it in warm water. 3.Add red litmus paper into it. 4.Observe the change in colour and decide the nature of the oxide formed. 5.Burn sulphur in a deflagrating spoon in the presence of air and dissolve the oxide formed in water. 6.Dip blue litmus paper into the solution and observe the changein the colour and decide the nature of the oxide formed. Observation: The oxide formed by metal turns red litmus blue whereas oxide of non-metal turns blue litmus red. Prepared by: M. S. KumarSwamy, TGT(Maths) Page - 6 - Chemical Reaction: Conclusion: Most of the metallic oxides are basic in nature whereas most of the non-metallic oxides are acidic in nature. 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 df activity series. Answer. (i) ‘A’ can be obtained by chemical reduction using carbon or carbon monoxide as reducing agent. (ii) ‘B’ can be obtained by electrolytic reduction. (iii) ‘C’ can be reduced by reducing agent like ‘Al’. 41. (a) Explain the formation of ionic compound CaO with electron dot structure. Atomic number of calcium and oxygen are 20 and 8 respectively. (b) Name the constituent metals of bronze. Answer. 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 responsible for this change. (ii)Name and write chemical formula of the green coating formed on the metal. (iii) List two important methods to prevent the process. Answer. (i) Metal is copper. The process is corrosion. (ii)Basic copper carbonate [CuCO3.Cu(0H)2]. (iii) • It should be coated with tin • It should be mixed with other metals to form alloys 43. Write balanced equations for the reaction of: (i) aluminium when heated in air. Write the name of the product. (ii) iron with steam. Name the product obtained. (iii) calcium with water. Why does calcium start floating in water? Answer. Prepared by: M. S. KumarSwamy, TGT(Maths) Page - 7 - 44. Write balanced chemical equations for the following reactions: (a) Dilute sulphuric acid reacts with aluminium powder. (b) Dilute hydrochloric acid reacts with sodium carbonate. (c) Carbon dioxide is passed through lime water. Answer. 45. What is meant by ‘rusting’? With labelled diagrams, describe an activity to find out the conditions under which iron rusts. Answer. The process in which iron reacts with oxygen in the presence of moisture to form reddish brown coating of hydrated ferric oxide [Iron (III) oxide].Fe2O3 xH20 Activity: (i) Take three boiling tubes A, B and C. (ii) Pour some water in test tube A Put iron nails in it and cork it. (iii) Pour boiled distilled water in another test tube B and put iron nails in it. Add 1 ml of ojl over it such that oil flo’ats over it and prevents the air from entering. (iv) Take some iron nails in test tube C and put some anhydrous calcium chloride in it and cork it. (v) Leave all the three test tubes for one day and then observe. Observation: Iron nails get rusted in test tube A because both air and water are present in it. Iron nails do not get rusted in B because there is water but no air. In C, rusting will not take place because there is neither air nor water. Conclusion: Iron gets rusted in the presence of air and water. 46. (a) Show the formation of Na2O by the transfer of electrons between the combining atoms. (b) Why are ionic compounds usually hard? (c) How is it that ionic compounds in the solid state do not conduct electricity but they do so when in molten state? Answer. Prepared by: M. S. KumarSwamy, TGT(Maths) Page - 10 - (b) Copper, being more reactive than silver will displace silver from silver nitrate solution and there will be deposition of silver on copper coin. The colour of solution will turn to blue. 56. (a) Define activity series of metals. Arrange the metals gold, copper, iron and magnesium in order of their increase in reactivity. (b) What will you observe when: (i) Some zinc pieces are put in copper sulphate solution. (ii) Some silver pieces are put into green coloured ferrous sulphate solution. Answer. (a) The series of metals in which metals are arranged in decreasing order of their reactivity. Au < Cu < Fe < Mg is increasing order of reactivity. (b) (i) The blue solution will become colourless and reddish brown copper metal will be deposited. Reaction will not take place because Ag’ is less reactive than iron. 57. (a) Write the chemical name of the coating that forms on silver and copper articles when these are left exposed to moist air. (b) Explain what is galvanisation. What purpose is served by it? (c) Define an alloy. How are alloys prepared? How do the properties of iron change when: (i) small quantity of carbon, (ii) nickel and chromium are mixed with it. Answer. (a) Ag2S (silver sulphide) is formed on silver, basic copper carbonate CuCO3. CU(OH)2 is formed on copper. (b) The process of coating zinc over iron is called galvanisation. It is used to prevent rusting of iron. (c) Alloy is a homogeneous mixture of two or more metals. One of them can be non-metal. Alloys are prepared by melting two or more metals together. (?) Iron does not rust on adding small,quantity of carbon. (ii) When we form alloy of iron with nickel and chromium, we get stainless steel which is malleable and does not get rusted. 58. (a) Differentiate between roasting and calcination. Explain the two with the help of suitable chemical equations. How is zinc extracted from its ore? (b) Name two metals that can be used to reduce metal oxides to metals. Answer. (a) Roasting: It is a process in which sulphide ore is heated in the presence of oxygen to convert into oxide. Cali ination: It is a process in which carbonate ore is heated in the absence of air to form oxide. By reduction process, Zn can be extracted from its ore. (b) Aluminium, Magnesium. 59. (a) In the formation of compound between two atoms A and B, A loses two electrons and B gains one electron. (i) What is the nature of bond between A and B? (ii) Suggest the formula of the compound formed between A and B. (b) On similar lines explain the formation of MgCl2 molecule. Prepared by: M. S. KumarSwamy, TGT(Maths) Page - 11 - (c) Common salt conducts electricity only in the molten state. Why? (d) Why is melting point of NaCl high? Answer. 60. (a) Carbon cannot be used as reducing agent to obtain Mg from MgO. Why? (b) How is sodium obtained from molten sodium chloride? Give equation of the reactions. (c) How is copper obtained from its sulphide ore? Give equations of the reactions. Answer. (a) It is because ‘Mg’ is stronger reducing agent than carbon. (b) Sodium is obtained from molten NaCl by electrolysis. Blister Copper is purified by electrolytic refining. 61. How is the method of extraction of metals high up in the reactivity series different from that for metals in the middle ? Why the same process cannot be applied for them? Explain giving equations, the extraction of sodium. Answer. Metals high up in the series are obtained by electrolytic reduction because these metals are strong reducing agents and therefore, cannot be obtained by chemical reduction. Metals in middle of series are less reactive and can be obtained by chemical reduction. The same process can not be used for both of them as highly reactive metals can not be obtained by chemical reduction. Extraction of sodium is done by electrolysis of molten sodium chloride. 62. Write the names and symbols of two most reactive metals. Explain by drawing electronic structure how any one of the two metals react with a halogen. State any four physical properties of the compound formed. Answer. K(Potassium) and Na(Sodium) are the two most reactive metals. K’ and Na‘ are electronic structures as they have one valence electron. where ‘F’ is a halogen. Prepared by: M. S. KumarSwamy, TGT(Maths) Page - 12 - Four physical properties of the compounds formed by these elements and halogens are: (i) They have high melting point. (ii)They are soluble in water. (iii) They conduct electricity in molten state not in solid state. (iv) They are solid and somewhat hard. 63. A metal ‘M’ which is one of the best conductor of heat and electricity used in making electric wires is found in nature as sulphide ore M2S? (i) Name the metal ‘M’ (ii) Which process will be suitable for extraction of this metal M from its ore M2S? Write the balanced chemical reactions involved in the process of ‘ extraction. (iii) With the help of a labelled diagram, explain the process of electrolytic refining of the metal. Answer. (i) Copper (ii) It is concentrated by froth-floatation process. Impure copper is purified by electrolytic refining. (iii) 1)The electrolytic tank containing acidified copper sulphate solution as electrolyte. 2) A thick block of impure copper metal is made anode. 3) A thin strip of pure copper metal is made cathode. On passing electric current,impure copper from the anode dissolves and goes into copper sulphate solution and pure copper from copper sulphate deposits on cathode.Thus pure copper metal is produced on the cathode.The soluble impurities go into the solution whereas insoluble impurities collect below the anode as anode mud. At cathode, Cu2+ + 2e– —> Cu At anode, Cu – 2e– —–> Cu2+ 64. Give reasons for the following: (i) Silver and copper lose their shine when they are exposed to air. Name the substance formed on their surface in each case. (ii) Tarnished copper vessels are cleaned with tamarind juice. (iii) Aluminium is more reactive than iron yet there is less corrosion of aluminium as compared to iron when both are exposed to air. Answer. Prepared by: M. S. KumarSwamy, TGT(Maths) Page - 15 - (c) (i) Metal will catch fire. (ii) Alkali solution is formed which turns red litmus blue. 72. (a) The reaction of metal (X) with ferric oxide is highly exothermic. Metal (X) is obtained from its oxides by electrolytic reduction. Identify (X) and write its reaction with ferric oxide. (b) Give reason to justify that aluminium oxide is an amphoteric oxide. Also, give another example of amphoteric oxide. (c) Mention constituent metals present in bronze. Answer. (a) ‘X’ is ‘Al’ (b) AI2O3 reacts with acid as well as base therefore it is amphoteric oxide. Zinc oxide is also an amphoteric oxide. (c) Bronze contains’ copper and tin. 73. No reaction takes place when granules of a solid ‘A’ are mixed with a powder of solid ‘B\ However when the mixture is heated, a reaction starts with evolution of much heat. Product ‘C’ of the reaction settles down as a liquid metal and solid product ‘D’ keeps floating over the liquid ‘C\ This reaction is sometimes used for making metals for ready use in odd places. (i) Based on this information, make assumptions about ‘A’ and ‘B’ and corresponding deductions about ‘C’ and ‘D’ and write a balanced chemical equation for the reaction. Include in the chemical equation about physical states of the reactants and products, need of heating for starting the reaction and the reaction being exothermic. (ii) Name two types of chemical reactions to which this reaction can belong. Answer. (i) ‘A’ is aluminum, ‘B’ is ferric oxide [Iron(III) oxide], (ii)This reaction is displacement reaction because AT is displacing ‘Fe’. It is also a redox reaction because AT is reducing agent and Fe2O3is oxidising agent. 74. (a) What is meant by corrosion? Name any two methods used for the prevention of corrosion. (b) Suppose you have to extract metal M from its enriched sulphide ore. If M is in the middle of the reactivity series, write various steps used in extracting this metal. Answer. (a) Corrosion is a process in which metal reacts with substances present in the environment to form surface compounds. Prevention: (i) Galvanisation is a process to prevent corrosion of iron. (ii)Electroplating is also used to prevent corrosion. (b)(i) Concentration of ores: Sulphide ore will be concentrated by froth- floatation process. Sulphide ore will be collected in froth whereas gangue will be left behind. (ii) Roasslng: Sulphide ore is heated strongly in the presence of O2 to form metal oxide and sulphur dioxide. 2MS + 3O2 ————- ► 2MO + 2SO2 (iii) Reduction: MO reacts with carbon (acts as reducing agent) to form metal and CO. MO + C —-> M + CO (iv) Electrolytic refining: Impure metal ‘M’ is purified by electrolytic refining. Impure metal is taken as anode, pure metal is taken as cathode, soluble salt of metal is taken as electrolyte. Impure metal forms metal ions which gain electrons and form pure metal at cathode. Prepared by: M. S. KumarSwamy, TGT(Maths) Page - 16 - 75. (a) Distinguish between ionic and covalent compounds under the following properties: (i) Strength of forces between constituent elements. (ii) Solubility of compounds in water. (iii) Electrical conduction in substances. (b) Explain how the following metals are obtained from their compounds by the reduction process: (i) Metal M which is in the middle of the reactivity series. (ii) Metal N which is high up in the reactivity series. Give one example of each type. Answer. Ionic Compounds Covalent Compounds (i) Strength – They have strong forces of attraction They have weak forces of attraction. (ii) Solubility – They are soluble in water They are insoluble in water (iii) Conduction – They conduct electricity in aqueous solution. They do not conduct electricity in aqueous solution. (b) (i) Metal M which is in the middle of the reactivity series is reduced by aluminium, e.g. 3MnO2(s) + 4Al(s) ——–> 2Al2O3(s) + 3Mn(l) (ii) Metal N will be obtained by electrolytic reduction, e.g. A1 is obtained by electrolytic reduction.