{"id":22249,"date":"2024-01-11T17:38:35","date_gmt":"2024-01-11T12:08:35","guid":{"rendered":"https:\/\/apboardsolutions.in\/?p=22249"},"modified":"2024-01-12T16:21:01","modified_gmt":"2024-01-12T10:51:01","slug":"ap-inter-2nd-year-chemistry-important-questions-chapter-5","status":"publish","type":"post","link":"https:\/\/apboardsolutions.in\/ap-inter-2nd-year-chemistry-important-questions-chapter-5\/","title":{"rendered":"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy"},"content":{"rendered":"<p>Students get through <a href=\"https:\/\/apboardsolutions.in\/ap-inter-2nd-year-chemistry-important-questions\/\">AP Inter 2nd Year Chemistry Important Questions<\/a> 5th Lesson General Principles of Metallurgy which are most likely to be asked in the exam.<\/p>\n<h2>AP Inter 2nd Year Chemistry Important Questions 5th Lesson General Principles of Metallurgy<\/h2>\n<p><span style=\"color: #0000ff;\">Very Short Answer Questions<\/span><\/p>\n<p>Question 1.<br \/>\nWhat is the role of depressant in froth floatation?<br \/>\nAnswer:<br \/>\nBy using depressants in froth floatation process, it is possible to separate a mixture of two sulphide ores.<br \/>\nEg: In the ore containing ZnS and PbS, the depressant used is NaCN. It prevents ZnS from coming to the froth but allows PbS to come with the froth.<\/p>\n<p>Question 2.<br \/>\nExplain &#8220;poling&#8221;. (AP Mar. &#8217;16, &#8217;15; IPE &#8217;16, 15 (AP))<br \/>\nAnswer:<br \/>\nWhen the metals are having the metal oxides as impurities this method is employed. The impure metal is. melted and is then covered by carbon powder. Then it is stirred with green wood poles. The reducing gases formed from the green wood and the carbon, reduce the oxides to the metal.<br \/>\nEg : Cu &amp; Sn metals are refined by this method.<\/p>\n<p><img loading=\"lazy\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/07\/AP-Board-Solutions.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy\" width=\"196\" height=\"17\" \/><\/p>\n<p>Question 3.<br \/>\nDecribe a method for the refining of nickel.<br \/>\nAnswer:<br \/>\nMond&#8217;s process:<\/p>\n<ul>\n<li>In Mond&#8217;s process, nickel is heated in a stream of carbon monoxide forming a volatile complex, nickel tetra carbonyl.<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-23588\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/09\/AP-Inter-2nd-Year-Chemistry-Important-Questions-Chapter-5-General-Principles-of-Metallurgy-1.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy 1\" width=\"308\" height=\"41\" \/><\/li>\n<li>Nickel tetra carbonyl is strongly heated to decompose and gives the pure Nickel.<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-23589\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/09\/AP-Inter-2nd-Year-Chemistry-Important-Questions-Chapter-5-General-Principles-of-Metallurgy-2.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy 2\" width=\"298\" height=\"38\" \/><\/li>\n<\/ul>\n<p>Question 4.<br \/>\nWhat is the role of cryolite in the metallurgy of aluminium ? (IPE 2015 (TS), BMP, 2016 (TS))<br \/>\nAnswer:<br \/>\nBy adding the cryolite to the pure Alumina, the melting point of pure Alumina is lowered (which is very high 2324K) and electrical conductivity of pure alumina is increased.<\/p>\n<p>Question 5.<br \/>\nGive the composition of the following alloys (IPE &#8217;16, &#8217;14 (TS)) (AP &amp; TS Mar. &#8217;17)<br \/>\na) Brass<br \/>\nb) Bronze<br \/>\nc) German Silver<br \/>\nAnswer:<br \/>\na) Composition of Brass : 60 &#8211; 80% Cu, 20 &#8211; 40% Zn<br \/>\nb) Composition of Bronze : 75 &#8211; 90% Cu, 10 &#8211; 25% Sn<br \/>\nc) Composition of German silver : 50 &#8211; 60% Cu, 10 &#8211; 30% Ni, 20 &#8211; 30% Zn.<\/p>\n<p><img loading=\"lazy\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/07\/AP-Board-Solutions.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy\" width=\"196\" height=\"17\" \/><\/p>\n<p>Question 6.<br \/>\nWhat is matte ? Give its composition.<br \/>\nAnswer:<br \/>\nDuring the extraction of \u2019Cu\u2019 from copper pyrites the product of the blast furnace consists mostly of Cu<sub>2<\/sub>S and a little of FeS. This product is known as &#8220;Matte&#8221;. It is collected from the outlet at the bottom of the furnace.<\/p>\n<p>Question 7.<br \/>\nWhat is flux ? Give an example.<br \/>\nAnswer:<br \/>\nFlux : An outside substance added to. ore to lower its melting point is known as flux.<\/p>\n<ul>\n<li>Flux combines with gangue and forms easily fusible slag.<br \/>\ngangue + flux \u2192 slag<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-23590\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/09\/AP-Inter-2nd-Year-Chemistry-Important-Questions-Chapter-5-General-Principles-of-Metallurgy-3.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy 3\" width=\"274\" height=\"55\" \/><\/li>\n<\/ul>\n<p>Question 8.<br \/>\nHow is aluminium useful in the extraction of chromium and manganese from their oxides ?<br \/>\nAnswer:<\/p>\n<ul>\n<li>&#8216;Al&#8217; is used as reducing agent.<\/li>\n<li>By Alumino thermite process Cr, Mn are extracted from their oxides.<\/li>\n<li>The reactions are highly exothermic.<\/li>\n<\/ul>\n<p>Cr<sub>2<\/sub>O<sub>3<\/sub> + 2Al \u2192 2Cr + Al<sub>2<\/sub>O<sub>3<\/sub><br \/>\n3Mn<sub>3<\/sub>O<sub>4<\/sub> + 8Al \u2192 4Al<sub>2<\/sub>O<sub>3<\/sub> + 9Mn<\/p>\n<p><img loading=\"lazy\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/07\/AP-Board-Solutions.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy\" width=\"196\" height=\"17\" \/><\/p>\n<p>Question 9.<br \/>\nWhat is a mineral ?<br \/>\nAnswer:<br \/>\nThe chemical compound from which a metal can be extracted is called a mineral. Bauxite, crayolite are the minerals of aluminium.<\/p>\n<p>Question 10.<br \/>\nWhat is an ore ?<br \/>\nAnswer:<br \/>\nAn ore is a mineral from which the metal can be extracted easily and economically. Bauxite is the ore of aluminium.<\/p>\n<p>Question 11.<br \/>\nWhat is a ore. Give the ores of Al, Zn, Fe, Cu.<br \/>\nAnswer:<br \/>\nThe mineral from which metal can be extracted economically is called ore.<br \/>\nAluminium ores : Bauxite = Al<sub>2<\/sub> O<sub>3<\/sub>. 2H<sub>2<\/sub>O; Cryolite = Na<sub>3<\/sub>Al F<sub>6<\/sub><br \/>\nZinc ores : Zinc blende = Zns; Calamine = ZnCO<sub>3<\/sub><br \/>\nCopper ores : Cuprite: CuO; Copper pyrites = Cu<sub>2<\/sub>S<br \/>\nIron ores : Haematite = Fe<sub>2<\/sub>O<sub>3<\/sub> Magnetite = Fe<sub>3<\/sub>O<sub>4<\/sub><\/p>\n<p>Question 12.<br \/>\nWhat is the role of SiO<sub>2<\/sub> in the extraction of copper.<br \/>\nAnswer:<br \/>\nIn the extraction of copper SiO<sub>2<\/sub> acts as flux. It combines with FeO and removes as slag.<br \/>\nFeO + SiO<sub>2<\/sub> (flux) \u2192 FeSiO<sub>3<\/sub> (Slag)<\/p>\n<p><span style=\"color: #0000ff;\">Short Answer Questions<\/span><\/p>\n<p>Question 1.<br \/>\nOutline the principles of refining of metals by the following methods.<br \/>\n(a) Zone refining<br \/>\n(b) Electrolytic refining<br \/>\n(c) Poling<br \/>\n(d) Vapour phase refining.<br \/>\nAnswer:<br \/>\na) Zone refining :<\/p>\n<ul>\n<li>Zone refining is based on the principle that the impurities are more soluble in the melt than in the solid state of the metal.<\/li>\n<li>A circular mobile heater is fixed at one end of a rod of impure metal.<\/li>\n<li>The molten zone moves along with the heater moves forward the pure metal crystallises out of the melt and the impurities pass into the adjacent molten zone.<\/li>\n<\/ul>\n<p><img loading=\"lazy\" class=\"alignnone size-full wp-image-23591\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/09\/AP-Inter-2nd-Year-Chemistry-Important-Questions-Chapter-5-General-Principles-of-Metallurgy-4.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy 4\" width=\"492\" height=\"201\" \/><\/p>\n<ul>\n<li>The above process is repeated several times and the heater is moved in the same direction form one end to the other end. At one end impurities get concentrated. This end is cut off.<\/li>\n<li>This method is very useful for producing semiconductor grade metals of very high purity.<br \/>\nEg : Ge, Si, B, Ga etc&#8230;<\/li>\n<\/ul>\n<p>b) Electrolytic refining: This process is used for less reactive metals like Cu, Ag, AZ, Au etc.<\/p>\n<ul>\n<li>In this process anode is made by impure metal and a thin strip of pure metal acts as cathode.<\/li>\n<li>On electrolysis metal dissolves from anode and pure metal gets deposited at cathode.<\/li>\n<\/ul>\n<p><img loading=\"lazy\" class=\"alignnone size-full wp-image-23592\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/09\/AP-Inter-2nd-Year-Chemistry-Important-Questions-Chapter-5-General-Principles-of-Metallurgy-5.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy 5\" width=\"275\" height=\"102\" \/><br \/>\nImpurities settle down below anode in the form of anode mud.<\/p>\n<p>c) Poling : When the metals are having the metal oxides as impurities this method is employed. The impure metal is melted and is then covered by carbon powder. Then it is stirred with green wood poles. The reducing gases formed from the green wood and the carbon, reduce the oxides to the metal. Eg : Cu &amp; Sn metals are refined by this method.<\/p>\n<p>d) Vapour phase refining: In this method the metal is converted into its volatile compound and coll Ted. It is then decomposed to give pure metal.<\/p>\n<ol>\n<li>The metal should form a volatile compound with an available reagent.<\/li>\n<li>The volatile compound should be easily decomposable. So the recovery is easy.<br \/>\nE.g : Mond&#8217;s process :<\/p>\n<ul>\n<li>In Mond&#8217;s process, nickel is heated in a stream of carbon monoxide forming a volatile complex, nickel tetra carbonyl,<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-23593\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/09\/AP-Inter-2nd-Year-Chemistry-Important-Questions-Chapter-5-General-Principles-of-Metallurgy-6.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy 6\" width=\"304\" height=\"39\" \/><\/li>\n<li>Nickel tetra carbonyl is strongly heated to decompose and gives the pure Nickel.<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-23594\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/09\/AP-Inter-2nd-Year-Chemistry-Important-Questions-Chapter-5-General-Principles-of-Metallurgy-7.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy 7\" width=\"289\" height=\"36\" \/><\/li>\n<\/ul>\n<\/li>\n<\/ol>\n<p><img loading=\"lazy\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/07\/AP-Board-Solutions.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy\" width=\"196\" height=\"17\" \/><\/p>\n<p>Question 2.<br \/>\nExplain the purification of sulphide ore by froth floatation method. (Mar &#8217;15) (A.P. Mar. &#8217;17)<br \/>\nAnswer:<br \/>\nFroth floatation method :<\/p>\n<ul>\n<li>This method is used to concentrate sulphide ores.<\/li>\n<li>In this process a suspension of the powdered ore is made with water.<\/li>\n<li>A rotating paddle is used to agitate the suspension and air is blown into the suspension in presence of an oil.<\/li>\n<li>Froth is formed as a result of blown of air, which carries the mineral particles.<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-23595\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/09\/AP-Inter-2nd-Year-Chemistry-Important-Questions-Chapter-5-General-Principles-of-Metallurgy-8.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy 8\" width=\"338\" height=\"323\" \/><\/li>\n<li>To the above slurry froth collectors and stabilizers are added.<\/li>\n<li>Collectors like pine oil enhance non-wettability of the mineral particles.<\/li>\n<li>Froth stabilizers like cresol stabilize the froth.<\/li>\n<li>The mineral particles wet by oil and gangue particles wet by water.<\/li>\n<li>The broth is light and is skimmed off. The ore particles are then obtained from the froth. By using depressants in froth floatation process, it is possible to separate a mixture of two suplhide ores. Eg: In the ore containing ZnS and PbS, the depressant used is NaCN. It prevents ZnS from coming to the froth but allows PbS to come with the froth.<\/li>\n<\/ul>\n<p>Question 3.<br \/>\nWhat is Ellingham diagram ? What information can be known from this in the reduction of oxides ?<br \/>\nAnswer:<br \/>\nThe graphical representation of Gibbs energy which provides a sound basis for considering the choice of reducing agent in the reduction of oxides. This graphical representation is known as Ellingham diagram.<br \/>\nThis diagram helps us in predicting the feasibility of thermal reduction of an ore.<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-23596\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/09\/AP-Inter-2nd-Year-Chemistry-Important-Questions-Chapter-5-General-Principles-of-Metallurgy-9.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy 9\" width=\"399\" height=\"380\" \/><\/p>\n<ul>\n<li>The Criterion of feasibility of a reaction is that at a given temperature, Gibbs energy of the reaction must be negative.<\/li>\n<li>Ellingham diagram normally consists plots of \u0394G\u00b0 vs T for formation of oxides of elements.<\/li>\n<li>The graph indicates whether a reaction is possible or not, i.e., the tendency of reduction with a reducing agent is indicated.<\/li>\n<li>The reducing agent forms its oxide when the metal oxide is reduced. The role of reducing agent is to make the sum of \u0394G\u00b0 values of the two reactions negative.<\/li>\n<li>Out of C and CO, Carbon monoxide (CO) is a better reducing agent at 673K.<\/li>\n<li>At 983K (or) above coke(C) is better reducing agent.<\/li>\n<li>The above observations are from Ellingham diagram.<br \/>\nZinc is not extracted from zinc oxide through reduction by using CO.<\/li>\n<\/ul>\n<p>Explanation :<br \/>\n2Zn + O<sub>2<\/sub> \u2192 2ZnO, \u0394G\u00b0 = -650 kJ<br \/>\n2CO + O<sub>2<\/sub> \u2192 2CO<sub>2<\/sub>, \u0394G\u00b0 = -450 kJ<br \/>\n2ZnO + 2CO \u2192 2Zn, 2CO<sub>2<\/sub>, \u0394G\u00b0 = 200 kJ<br \/>\n\u0394G\u00b0 = Positive indicates that the reaction is not feasible.<br \/>\nThe above fact is explained on the basis of Ellingham diagram.<\/p>\n<p><img loading=\"lazy\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/07\/AP-Board-Solutions.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy\" width=\"196\" height=\"17\" \/><\/p>\n<p>Question 4.<br \/>\nGive examples to differentiate roasting and calcination. (IPE &#8217;14, B.M.P. 2016) (A.P. &amp; T.S. Mar. &#8217;16, &#8217;15)<br \/>\nAnswer:<br \/>\nRoasting: Removal of the volatile components of a mineral by heating mineral either alone (or) mixed with some other substances to a high temperature in the presence of air is called Roasting.<\/p>\n<ul>\n<li>It is applied to the sulphide ores.<\/li>\n<li>SO<sub>2<\/sub> gas is producted along with metal oxide.<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-23597\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/09\/AP-Inter-2nd-Year-Chemistry-Important-Questions-Chapter-5-General-Principles-of-Metallurgy-10.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy 10\" width=\"309\" height=\"35\" \/><\/li>\n<\/ul>\n<p>Calcination: Removed of the volatile components of a mineral by heating in the absence of air is called calcination.<\/p>\n<ul>\n<li>It is applied to carbonates and bicarbonates.<\/li>\n<li>CO<sub>2<\/sub> gas is produced along with metal oxide.<\/li>\n<\/ul>\n<p><img loading=\"lazy\" class=\"alignnone size-full wp-image-23598\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/09\/AP-Inter-2nd-Year-Chemistry-Important-Questions-Chapter-5-General-Principles-of-Metallurgy-11.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy 11\" width=\"260\" height=\"74\" \/><\/p>\n<p>Question 5.<br \/>\nHow is copper extracted from copper pyrites ?<br \/>\nAnswer:<br \/>\nExtraction of copper from copper pyrites :<br \/>\nCopper pyrite is the main source of copper metal. Various steps involved in the extraction of copper are discussed below.<\/p>\n<p>Step -I:<\/p>\n<p>Concentration of ore by froth floatation process :<br \/>\nThe ore is first crushed in ball mills. The finely divided ore is suspended in water. A little pine oil is added and the mixture is vigorously&#8217; agitated by a current of air. The froth formed carries the ore particles almost completely. The gangue sinks to the bottom of the tank. The froth is separated and about 95% concentrated ore is obtained.<\/p>\n<p>Step -II:<\/p>\n<p>Roasting : To remove the volatile impurities like As (or) Sb, the ore is roasted in a free supply of air. A mixture of sulphides of copper and iron are obtained and these are partially oxidised to respective oxides.<br \/>\nCu<sub>2<\/sub>S. Fe<sub>2<\/sub>S<sub>3<\/sub> + O<sub>2<\/sub> \u2192 Cu<sub>2<\/sub>S + 2FeS + SO<sub>2<\/sub><br \/>\n2Cu<sub>2<\/sub>S + 3O<sub>2<\/sub> \u2192 2Cu<sub>2<\/sub>O + 2SO<sub>2<\/sub><br \/>\n2FeS + 3O<sub>2<\/sub> \u2192 2FeO + 2SO<sub>2<\/sub><\/p>\n<p>Step -III: .<\/p>\n<p>The roasted ore is mixed with a little coke and sand (Silica) and smelted in a blast furnace and fused. A blast of air, necessary for the combustion of coke, is blown through the tuyeres present at the base of the furnace.\u2019 The oxidation of the sulphides of copper and iron will be completed further. A slag of iron silicate is formed according to the reactions given below :<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-23599\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/09\/AP-Inter-2nd-Year-Chemistry-Important-Questions-Chapter-5-General-Principles-of-Metallurgy-12.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy 12\" width=\"388\" height=\"116\" \/><\/p>\n<p>Step -IV :<\/p>\n<p>After smelting the copper ore in blast furnace, the product of the blast furnace consists mostly of Cu<sub>2<\/sub>S and a little of ferrous sulphide. This product is known as &#8220;Matte.&#8221; It is collected from the outlet at the bottom of the furnace. After then the following processes are carried out for getting the pure copper.<\/p>\n<p>Bessemerization : The matte is charged into a Bessemer converter. A bessemer converter is a pear-shaped furnace. It is made of steel plates. The furnace is given a basic lining with lime or magnesium oxide (obtained from dolomite or magnesite). The converter is held in position by trunnions and can be tilted in any position. A hot blast of air and sand is blown through the tuyeres present near the bottom. Molten metal, the product in the furnace, collects at the bottom of the converter.<\/p>\n<p>Reactions that took place in blast furnace go to completion. Almost all of iron is eliminated slag. Cuprous oxide combines with cuprous sulphide and forms Cu metal.<br \/>\n2Cu<sub>2<\/sub>O + Cu<sub>2<\/sub>S \u2192 6Cu + SO<sub>2<\/sub><br \/>\nThe molten metal is cooled in sand moulds. SO<sub>2<\/sub> escapes. The impure copper metal is known as \u2018Blister copper\u201d and is about 98% pure.<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-23600\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/09\/AP-Inter-2nd-Year-Chemistry-Important-Questions-Chapter-5-General-Principles-of-Metallurgy-13.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy 13\" width=\"283\" height=\"324\" \/><\/p>\n<p>Step -V:<\/p>\n<p>Refining: The Blister copper is purified by electrolysis. The impure copper metal is made into plates. They are<br \/>\nsuspended into lead \u2014 lined tanks containing Copper (II) Sulphate solution. Thin plates of pure copper serve as<br \/>\ncathode. The cathode plates are coated with graphite. On electrolysis, pure copper is deposited at the cathode. The<br \/>\ncopper obtained is almost 100% pure Cu.<\/p>\n<p><img loading=\"lazy\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/07\/AP-Board-Solutions.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy\" width=\"196\" height=\"17\" \/><\/p>\n<p>Question 6.<br \/>\nExplain the process of leacing of aluminium from bauxite.<br \/>\nAnswer:<br \/>\nExtraction of Aluminium from Bauxite:<br \/>\nFor the purpose of extraction of Al, Bauxite is the best source.<br \/>\nPurification of Bauxite: Bauxite containing Fe<sub>2<\/sub>O<sub>3<\/sub> as impurity is known as Red Bauxite.<br \/>\nBauxite containing SiO<sub>2<\/sub> as impurity is known as White Bauxite and can be purified by \u201cSet-peck\u2019s Process. Red Bauxite is purified by Bayer\u2019s process and Hall\u2019s process.<\/p>\n<p>Bayer\u2019s Process: Red bauxite is roasted and digested in concentrated NaOH at 423 K. Bauxite dissolves in NaOH to form sodium meta aluminate while impurity Fe<sub>2<\/sub>O<sub>3<\/sub> does not dissolve which can be removed by filtration.<br \/>\nAl<sub>2<\/sub>O<sub>3<\/sub>.2H<sub>2<\/sub>O + 2NaOH \u2192 2NaAlO<sub>2<\/sub> + 3H<sub>2<\/sub>O<br \/>\nThe solution which contains sodium meta aluminate is diluted and crystals of Al(OH)<sub>3<\/sub>, are added which serves as seeding orgent. Sodium meta aluminate undergoes hydrolysis to precipitate Al(OH)<sub>3<\/sub>.<br \/>\n2NaAlO<sub>2<\/sub> + 4H<sub>2<\/sub>O \u2192 2NaOH + 2Al(OH)<sub>3<\/sub>\u2193<br \/>\nAl(OH)<sub>3<\/sub> is filtered and ignited at 1200\u00b0C to get anhydrous alumina.<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-23601\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/09\/AP-Inter-2nd-Year-Chemistry-Important-Questions-Chapter-5-General-Principles-of-Metallurgy-14.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy 14\" width=\"256\" height=\"36\" \/><br \/>\nHalls\u2019 Process: Red Bauxite is fused with sodium carbonate to form sodium meta aluminate<br \/>\nwhich is extracted with water. The impurity Fe<sub>2<\/sub>O<sub>3<\/sub> is filtered out.<br \/>\nAl<sub>2<\/sub>O<sub>3<\/sub> + Na<sub>2<\/sub>CO<sub>3<\/sub> \u2192 2NaAlO<sub>2<\/sub> + CO<sub>2<\/sub><br \/>\nInto the solution of sodium meta aluminate, CO<sub>2<\/sub> gas is passed to precipitate Al(OH)<sub>3<\/sub>.<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-23602\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/09\/AP-Inter-2nd-Year-Chemistry-Important-Questions-Chapter-5-General-Principles-of-Metallurgy-15.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy 15\" width=\"449\" height=\"45\" \/><br \/>\nThe precipitated Al(OH)<sub>3<\/sub> is ignited at 1200\u00b0C to get anhydrous alumina.<br \/>\n2Al(OH)<sub>3<\/sub> \u2192 Al<sub>2<\/sub>O<sub>3<\/sub> + 3H<sub>2<\/sub>O<\/p>\n<p>Serpeck&#8217;s Process: Powdered bauxite is mixed with coke and heated to 2075 K in a current of nitrogen gas. Aluminium Nitride is formed while SiO<sub>2<\/sub> is reduced to Si which escapes out.<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-23603\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/09\/AP-Inter-2nd-Year-Chemistry-Important-Questions-Chapter-5-General-Principles-of-Metallurgy-16.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy 16\" width=\"346\" height=\"80\" \/><br \/>\nAluminium nitride is hydrolysed to get aluminium hydroxide which on ignition gives anhydrous alumina.<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-23604\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/09\/AP-Inter-2nd-Year-Chemistry-Important-Questions-Chapter-5-General-Principles-of-Metallurgy-17.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy 17\" width=\"291\" height=\"72\" \/><br \/>\nElectrolytic Reduction of Alumina: Pure Alumina (Al<sub>2<\/sub>O<sub>3<\/sub>) is a bad conductor of electricity and it has high melting point (2050\u00b0C). So it cannot be electrolysed. Alumina is electrolysed by dissolving in fused cryolite to increase the conductivity and small amount of Fluorspar is added to reduce its melting point. Thus the electrolyte is a fused mixture of Alumina, Cryolite and Fluorspar.<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-23605\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/09\/AP-Inter-2nd-Year-Chemistry-Important-Questions-Chapter-5-General-Principles-of-Metallurgy-18.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy 18\" width=\"443\" height=\"315\" \/><br \/>\nElectrolysis is carried out in an iron tank lined inside with graphite (carbon) which functions as cathode. A number of carbon rods (or) copper rods suspended in the electrolyte functions as anode.<\/p>\n<p>An electric current of 100 amperes at 6 to 7 volts is passed through the electrolyte. Heat produced by the current keeps the mass in fused state at 1175 to 1225K. The following reactions take place in the electrolytic cell under these conditions.<br \/>\nNa<sub>3<\/sub>AlF<sub>6<\/sub> \u2192 3NaF + AlF<sub>3<\/sub><br \/>\nCryolite<br \/>\n4AlF<sub>3<\/sub> \u2192 4Al<sup>3+<\/sup> + 12F<sup>&#8211;<\/sup><br \/>\nAt cathode : 4Al<sup>3+<\/sup> + 12e<sup>&#8211;<\/sup> \u2192 4Al<br \/>\nAt anode : 12F<sup>&#8211;<\/sup> \u2192 6F<sub>2<\/sub> + 12e<sup>&#8211;<\/sup><br \/>\nF<sub>2<\/sub> formed at the anode reacts with alumina and forms Aluminium fluoride.<br \/>\n2Al<sub>2<\/sub>O<sub>3<\/sub> + 6F<sub>2<\/sub> \u2192 4AlF<sub>3<\/sub> + 3O<sub>2<\/sub><br \/>\nAluminium, produced at the cathode, sinks to the bottom of the cell. It is removed from time to time through topping hole.<\/p>\n<p>Purification of Aluminium: (Hoope\u2019s Process)<\/p>\n<p>The impurities present are Si, Cu, Mn etc.,<br \/>\nThe electrolytic cell used for refining of aluminium consists of iron tank lined inside with<br \/>\ncarbon. This acts as anode. The tank contains three layers of fused masses. The bottom layer<br \/>\ncontains impure aluminium. Middle layer contains mixture of AlF<sub>3<\/sub>, NaF and BaF<sub>2<\/sub> saturated with Al<sub>2<\/sub>O<sub>3<\/sub>. Top layer contains pure aluminium and graphite rods kept in it act as cathode.<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-23606\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/09\/AP-Inter-2nd-Year-Chemistry-Important-Questions-Chapter-5-General-Principles-of-Metallurgy-19.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy 19\" width=\"518\" height=\"288\" \/><br \/>\nOn passing current aluminium ions from the middle layer are discharged at the cathode as pure aluminium. Equivalent amount of aluminium from the bottom layer passes into middle layer.<\/p>\n<p>Question 7.<br \/>\nExplain the reactions occuring in the blast furnace in the extraction of iron.<br \/>\nAnswer:<br \/>\nIn the Blast furnace, reduction of iron oxides takes place in different temperature ranges. Hot air is blown from the bottom of the furnace and coke is burnt to give temperature upto about 2200K in the lower portion itself, The burning of coke therfore supplies most of the heat required in the process. The CO and heat moves to upper part of the furnace. In upper part, the temperature is lower and the iron oxides (Fe<sub>2<\/sub>O<sub>3<\/sub> and Fe<sub>3<\/sub>O<sub>4<\/sub>) coming from the top are reduced in steps to FeO. Thus, the reduction reactions taking place in the lower temperature range and in the higher temperature range, depend on the points of corresponding intersections in the \u0394<sub>r<\/sub>G<sup>\u03b8<\/sup> vs T plots. These reactions can be summarised as follows:<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full wp-image-23607\" src=\"https:\/\/apboardsolutions.com\/wp-content\/uploads\/2022\/09\/AP-Inter-2nd-Year-Chemistry-Important-Questions-Chapter-5-General-Principles-of-Metallurgy-20.png\" alt=\"AP Inter 2nd Year Chemistry Important Questions Chapter 5 General Principles of Metallurgy 20\" width=\"420\" height=\"452\" \/><\/p>\n<p>At 500 \u2014 800 K (lower temperature range in the blast furnace)<br \/>\n3 Fe<sub>2<\/sub>O<sub>3<\/sub> + CO \u2192 2 Fe<sub>3<\/sub>O<sub>4<\/sub> + CO<sub>2<\/sub><br \/>\nFe<sub>3<\/sub>O<sub>4<\/sub> + 4CO \u2192 3 Fe + 4 CO<sub>2<\/sub>.<br \/>\nFe<sub>2<\/sub>O<sub>3<\/sub> + CO \u2192 2 FeO + CO<sub>2<\/sub><br \/>\nAt 900- 1500 K (higher temperature range in the blast furnace)<br \/>\nC + CO<sub>2<\/sub> \u2192 2 CO<br \/>\nFeO + CO \u2192 Fe + CO<sub>2<\/sub><br \/>\nLime stone is also decomposed to CaO which removes silicate impurity of the ore as CaSiO<sub>3<\/sub> slag. The slag is in molten state and separ\u00e5tes out from iron.<\/p>\n<p>The iron obtained from blast furnace contains about 4% carbon and many impurities in smaller amount (e.g., S, P, Si, Mn). This is known as pig iron. Cast iron is different from and is made by melting pig iron with scrap iron and coke using hot air blast. It has slightly lower carbon content (about 3%) and is extremely hard and brittle.<br \/>\nFe<sub>2<\/sub>O<sub>3<\/sub> + 3 C \u2192 2 Fe + 3 CO<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Students get through AP Inter 2nd Year Chemistry Important Questions 5th Lesson General Principles of Metallurgy which are most likely to be asked in the exam. AP Inter 2nd Year Chemistry Important Questions 5th Lesson General Principles of Metallurgy Very Short Answer Questions Question 1. What is the role of depressant in froth floatation? 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