Metals and Non-Metals.pdf

3 CHAPTER Metals and Non-metals NCERT Corner In-text Questions Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g) 1. Give an example of a metal which Potassium reacts wit...

3 CHAPTER Metals and Non-metals NCERT Corner In-text Questions Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g) 1. Give an example of a metal which Potassium reacts with cold water immediately and violently with liberation of H2 that catches fire. (i) Is a liquid at room temperature? 2K(s) + 2H2O(l) → 2KOH(aq) + H2(g)+Heat (ii) Can be easily cut with a knife? 5. Samples of four metals A, B, C and D were taken (iii) Is the best conductor of heat? and added to the following solution one by one. The (iv) Is a poor conductor of heat? results obtained have been tabulated as follows: Ans. (i) Mercury is the metal that is liquid at room Metal Iron (II) Copper (II) Zinc Silver temperature sulphate sulphate sulphate Nitrate (ii) Sodium and potassium are the softest metals that A No reaction Displacement – – can be cut with a knife B Displacement – No reaction – (iii) Silver is the best conductor of heat C No reaction No reaction No reaction Displacement (iv) Mercury and lead are poor conductor of heat. D No reaction No reaction No reaction No reaction 2. Explain the meanings of malleable and ductile. Use the Table above to answer the following Ans. (i) Metals that can be beaten to sheets are considered questions about metals A, B, C and D. to be malleable (i) Which is the most reactive metal? (ii) What would you observe if B is added to a (ii) Metals which can be drawn into thin wires are solution of Copper (II) sulphate? considered to be ductile (iii) Arrange the metals A, B, C and D in the order of 3. Why is sodium kept immersed in kerosene oil? decreasing reactivity. Ans. Sodium is highly reactive metal and if it is kept Ans. (i) Metal B is the most reactive as it will gives open, it will react with oxygen. And this can result displacement reaction with Iron (II) sulphate in explosion and fire. Thus, sodium metal is kept (FeSO4). immersed in kerosene oil to avoid its reaction with (ii) When metal B react with copper (II) sulphate oxygen, moisture and carbon dioxide of air. solution, a displacement reaction will take place due to which the blue colour of copper 4. Write equations for the reactions of (II) sulphate solution (CuSO4) will fade and a (i) iron with steam red-brown deposit of copper will be formed on metal B. (ii) calcium and potassium with water (iii) Metal B is the most reactive because it displaces Ans. (i) Iron reacts with steam to form a iron(II,III) iron from its salt solution. Metal A is less reactive oxide and H2 gas. because it will displaces copper (Cu) from its salt solution CuSO4. Metal C is less reactive because 3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g) it can displace only silver from its salt solution (ii) Calcium reacts with water to form calcium (AgNO3) and metal D is least reactive metal as it hydroxide and hydrogen gas. cannot displace any metal from its salt solution.  Thus, the decreasing order of reactivity of the The ions that are present in Magnesium oxide metals is compound (MgO) are: Magnesium ion [Mg2+] B > A > C > D. and oxide ion (O2–). 6. Which gas is produced when dilute hydrochloric 9. Why do ionic compounds have high melting points? acid is added to a reactive metal? Write the chemical Ans. The ionic compounds are made up of positive and reaction when iron reacts with dilute H2SO4. negative ions. There is a strong force of attraction Ans. Hydrogen gas is produced when dilute HCl is added between the oppositely charge ions, so a lot of to a reactive metal. of heat energy is required to break this force of Fe(s) + H2SO4(aq) → FeSO4(aq) + H2(g) attraction and melt the ionic compound. Due to 7. What would you observe when zinc is added to a this, ionic compounds have high melting points. solution of iron (II) sulphate? Write the chemical 10. Define the following terms. reaction that takes place. (i) Mineral Ans. Zinc is more reactive than iron. Thus, Zinc displaces Iron from its salt solution, i.e., FeSO4. The colour (ii) Ore of ferrous sulphate is pale green, which will turns (iii) Gangue colourless upon reaction. Ans. (i) Minerals are compounds that are found FeSO4(aq) + Zn(s) → ZnSO4(aq) + Fe(s) naturally in the earth’s crust. For Example: Pale green Zinc sulphate Alums(K2SO4.Al2(SO4)3.24H2O) etc. (Colourless) (ii) Ores are the minerals from which metal can 8. (i) Write the electron-dot structures for sodium, be extracted profitably. For Example: Bauxite oxygen and magnesium. Al2O3.2H2O is the ore of Al, copper pyrite (ii) Show the formation of Na2O and MgO by the CuFeS2 is the ore of Cu. transfer of electrons. (iii) Ores that is mined from the earth are naturally (iii) What are the ions present in these compounds? contaminated with impurities like sand, rocky Ans. (i) Sodium:  Oxygen:   Magnesium: materials. These impurities present in the ore   Na      O      Mg : are known as gangue. (ii) Formation of Magnesium oxide: 11. Name two metals which are found in nature in the When magnesium (Mg) reacts with oxygen free state (O), the magnesium atom transfers its two Ans. Gold and platinum are the two metals found in the valence electrons to an oxygen atom. By losing free state in nature. two electrons, the magnesium atom forms a magnesium ion (Mg 2+) and by gain of two 12. What chemical process is used for obtaining a metal electrons, the oxygen atom forms an oxide ion from its oxide? (O2–). Ans. Reduction method is used to obtain metal from its Mg: + O → MgO oxide. Formation of Sodium oxide: For Example: Zinc oxide is reduced to zinc by Two sodium atoms (Na) transfer their 1 valence heating with carbon electrons each to an oxygen atom. By loss of two ZnO + C  ∆ → Zn + CO electrons, the two sodium atoms form sodium ions (2Na+) and by gain of two electrons, the 13. Metallic oxides of zinc, magnesium and copper oxygen atom forms an oxide ion (O2–). were heated with the following metals. Na Metal Zinc Magnesium Copper + O: —→ Na2O Na Zinc Oxide (iii) The ions that are present in sodium oxide Magnesium Oxide compound (Na2O) are: Sodium ions (2Na+) and Copper Oxide oxide ion (O2–). 10 UDAAN Study Material Class-X PW  In which cases, will you find displacement reactions Magnesium taking place ? No reaction No reaction No reaction Oxide Ans. A more reactive metal that is placed higher in reactivity series can displace a less reactive metal Copper Displacement Displacement No reaction from its oxide. Among Zinc (Zn), Magnesium Oxide (Mg), and Copper (Cu) metals. Magnesium is Magnesium (Mg) will displace both Zinc (Zn) and the most reactive, copper is the least reactive Copper (Cu) from their oxides as it is placed higher metal and zinc is less reactive. The displacement in reactivity series. reaction will take place in the following cases are: 14. Which metals do not corrode easily? Ans. Gold and platinum are the metals which do not Metal Zinc Magnesium Copper corrode easily 15. What are alloys? Zinc Oxide No reaction Displacement No reaction Ans. An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal. NCERT Exercise 1. Which of the following pairs will give displacement (a) Calcium (b) Carbon reactions? (c) Silicon (d) Iron (a) NaCl solution and copper metal Ans. (a) Calcium. (b) MgCl2 solution and aluminium metal Calcium reacts with oxygen to form calcium oxide (c) FeSO4 solution and silver metal which has high melting point. Calcium oxide is water (d) AgNO3 solution and copper metal soluble so it will give Calcium Hydroxide in water. Ans. (d) Copper displace the silver metal from AgNO3 Carbon forms carbon-dioxide with oxygen that is gas. solution and reduce it to the elemental metal Ag in the Silicon reacts with oxygen to give silicon dioxide. process. Copper itself gets oxidised to Cu2+ and silver This is insoluble in water. metal gets precipitate out and a copper (II) nitrate Iron reacts with oxygen to give Iron oxide. This is also solution will form. insoluble in water. Cu(s) + 2AgNO3(aq) → Cu(NO3)2(aq) + 2Ag(s) 4. Food cans are coated with tin and not with zinc because 2. Which of the following methods is suitable for (a) Zinc is costlier than tin. preventing an iron frying pan from rusting? (b) Zinc has a higher melting point than tin. (a) Applying grease (c) Zinc is more reactive than tin. (b) Applying paint (d) Zinc is less reactive than tin. (c) Applying a coating of zinc Ans. (c) Food cans are coated with tin and not with zinc (d) All of the above because Zinc is more reactive (placed at higher position than tin in reactivity series) than tin. Thus it Ans. (c) Applying a coat of Zinc react with organic acids present in food to form toxic Though, applying grease and paint will prevent iron compounds that are harmful for us. from rusting but we cannot apply these methods 5. You are given a hammer, a battery, a bulb, wires and on frying pan. Thus applying a coat of zinc is most a switch. suitable method to prevent an iron pan from rusting. (a) How could you use them to distinguish between 3. An element reacts with oxygen to give a compound samples of metals and non-metals? with a high melting point. This compound is also (b) Assess the usefulness of these tests in distinguishing soluble in water. The element is likely to be between metals and non-metals. Metals and Non-metals 11 Ans. (a) Metals are malleable and can be easily drawn (a) What will be the action of gas on into sheets by hitting with hammer whereas if (i) dry litmus paper? we beat non-metals they break down easily and (ii) moist litmus paper? they cannot be drawn into sheets as they are non- malleable. (b) Write a balanced chemical equation for the reaction taking place. Metals are considered good conductors of electricity thus they make bulb glow when we Ans. (a) When sulphur powder is burnt in the air sulphur- connect metals with a battery, wire and bulb. dioxide (SO2) is formed. Similarly non-metals are bad conductors of (i) Sulphur dioxide will not have any effect on electricity, and they will not lit up the bulb on dry litmus paper. connecting with wire and battery. (ii) Moist litmus paper contains water as a result, (b) These tests are helpful and useful to show the SO2 reacts with it to form sulphurous acid. malleability and electrical conductivity nature of Hence, Sulphur dioxide will turn the moist the metals and non-metals. litmus paper from blue to red. 6. What are amphoteric oxides? Give two examples of (b) S(s) + O2(g) → SO2(g) amphoteric oxides SO2(g) + H2O (l) → H2SO3(aq) Ans. Oxides which react with both acids and bases to    (moist litmus    (Sulphurous give salt and water are called amphoteric oxides.       paper)      acid) For Examples: ZnO and Al2O3. 10. State two ways to prevent the rusting of iron. 7. Name two metals which will displace hydrogen Ans. (i) Iron can be protected from rusting by coating the from dilute acids, and two metals which will not. surface of the iron with rust proof paints. Ans. Aluminium (Al) and Magnesium (Mg) will displace (ii) By applying Oil/grease on the surface of iron hydrogen from dilute acids as they are considered objects. It will protect the iron surface to come in very reactive metals. Gold and Silver will not displace contact with air that contains moisture. hydrogen from dilute acids as these metals are less 11. What type of oxides are formed when non-metals reactive (lie at bottom of activity series). combine with oxygen? 8. In the electrolytic refining of a metal M, what would Ans. Non-metals combine with oxygen to give acidic and you take as the anode, the cathode and the electrolyte? neutral oxides. Ex: N2O5 or N2O3 is an acidic oxide; Ans. In the electrolytic refining of metal ‘M’, an impure CO is a neutral oxide. and thick block of metal M is taken as anode, thin 12. Give reasons strip or wire of pure metal M is taken as cathode. (a) Platinum, gold and silver are used to make A suitable salt solution of metal M is taken as the jewellery. electrolyte. (b) Sodium, potassium and lithium are stored under 9. Pratyush took sulphur powder on a spatula and heated oil. it. He collected the gas evolved by inverting a test tube (c) Aluminium is a highly reactive metal, yet it is used over it, as shown in figure below. to make utensils for cooking. (d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction Ans. (a) Platinum, gold and silver are used to make Test tube jewellery because these metals are least reactive (lie at bottom of series) thus they are not affected by air, moisture or most chemicals. These metals Spatula containing are lustrous, malleable, ductile in nature and are sulphur powder corrosion resistant. Burner (b) Sodium and potassium are stored under oil because they react with oxygen so vigorously that they catch fire if kept in the open. Hence in order to prevent contact with water, these metals are stored Collecting of gas under oil like kerosene. 12 UDAAN Study Material Class-X PW  (c) Aluminium forms a non reactive layer of aluminium They are good reducing They are good oxidizing oxide on its surface. This coating prevents other agents. agents. compounds from reacting with aluminium. Thus, aluminium is used to make utensils for cooking. Most of metal displace Non-metals are non- hydrogen from dilute reactive with dilute (d) Carbonate and sulphide ores are usually converted acids. acids. into oxides during the process of extraction because metals can be easily extracted by the reduction of Most metals displace Non-metal usually do hydrogen from water/ not react with water/ their oxides rather than from their carbonates and water vapours to form water vapours. sulphides. metal hydroxide. 13. You must have seen tarnished copper vessels being Metals react with Non-metals react with cleaned with lemon or tamarind juice. Explain why chlorine to form ionic chlorine to form covalent these sour substances are effective in cleaning the chlorides compounds. vessels. 15. A man went door to door posing as a goldsmith. He Ans. Tarnished copper vessels are being cleaned with promised to bring back the glitter of old and dull lemon or tamarind juice because they contains organic gold ornaments. An unsuspecting lady gave a set of acids which will dissolve the coating of copper oxide gold bangles to him which he dipped in a particular or basic copper carbonate formed on the surface of solution. The bangles sparkled like new but their tarnished copper vessels. This will makes them shine weight was reduced drastically. The lady was upset red-brown again. Thus, sour substance are very but after a futile argument the man beat a hasty retreat. effective in cleaning tarnished copper vessels. Can you play the detective to find out the nature of the 14. Differentiate between metal and non-metal on the solution he had used? basis of their chemical properties. Ans. Goldsmith has used Aqua regia which is also known Ans. as royal water. It is the mixture of concentrated Metals Non-metals Hydrochloric acid and concentrated Nitric acid in the ratio of 3:1. Aqua regia dissolves noble metals like When metals are heated When non-metals are gold and platinum. When upper-layer of dull gold with oxygen, they will heated with oxygen, ornament is dissolved in aqua regia solution, gold lose form ionic oxides that they will form covalent their weight and the bangles shine again like new one. are basic in nature. oxides that are acidic in 16. Give reasons why copper is used to make hot water nature. tanks and not steel (an alloy of iron). They are electro positive They are electro negative Ans. Copper is used in making hot water tanks and not steel in nature. They lose in nature. They gain (an alloy of iron) because copper does not react with electrons readily and electrons readily and either water or steam while iron reacts with steams forms a positive ion. forms negative ions. thus it will corrode the tank. Metals and Non-metals 13