(a) Fused alumina is bad conductor of electricity, therefore cryolite is added to purified alumina which makes it a good conductor and reduces the melting point of the mixture. This impure end is then cut off. To remove basic FeO, an acidic flux silica is added during smelting. and froth stabilisers (e.g. Delhi 2012) Cu → Cu2+ + 2e– Answer: (b) Copper obtained from copper pyrites have a blistered appearance due to the evolution of SO2 and so it is called blister copper. (b) Out of C and CO, which is a better reducing agent at the lower temperature range in the blast furnace to extract iron from the oxide ore? Why is copper matte put in silica lined converter? Write the main reason for the stability of colloidal sols. Describe the principle controlling each of the following processes : Question 11. Question 66. Ni(CO)4 4\(\underrightarrow { 450-470K } \) Ni + 4CO, Question 59. (iii) Lowering down the melting point and increasing the conductivity. NCERT Solutions for Class 6, 7, 8, 9, 10, 11 and 12. (iii) For overall reaction ΔGV has negative value. (ii) Zone refining of metals: This method is based on the principle that impurities are more soluble in the molten state of the metal (the melt) than in the solid state. (ii) Iodine in the refining of titanium Question 13. Facebookpräsenz zum Blog philosophia-perennis.com - Liberalkonservative Seite - … Explain the significance of leaching in the extraction of aluminium. Answer: For e.g, sulfide ores of Pb, and Zn are turned into their respective oxides through this process.2Zns + 3O2 ⇒ 2ZnO + 2SO2. It is the refining of impure metals using electricity. and froth stabilisers (e.g. Give equations, if any. It is dissolved in cryolite which lowers the melting point and brings conductivity. (a) Write the principle of vapour phase refining. *According to the Revised CBSE Syllabus 2020-21, this chapter has been removed. The end with impurities is cut off. When dealing with low grade copper ores, bacteria or acids are used in the presence of air to leach the copper. Zinc ore→ Zinc blende. Copper is extracted by hydrometallurgy from low grade ores. Al2 O3 is used as the stationary phase. At anode : (oxidation) Delhi 2016) Free PDF download of NCERT Solutions for Class 12 Chemistry Chapter 6 General Principles and Processes of Isolation of Elements solved by Expert Teachers as per NCERT (CBSE) Book guidelines. Question 46. (Comptt. All India 2013) It is a method of metal refining by converting the metal into its volatile compound and then decomposing it to get the pure metal.To achieve this:(1) the metal should convert into a volatile compound with a reagent,(2) the volatile compound of the metal has to be able to decompose easily so that the pure metal can be conveniently recovered.Zirconium, titanium and nickel are refined through this method. How far do you agree with this statement? At the cathode, H2 is obtained ( in place of Na ). Het laatste nieuws over de beurs, financiële wereld, economie, politiek en ondernemen vind je op fd.nl (ii) What is the role of silica in the extraction of copper? In this method, heat is supplied to nickel in the presence of carbon monoxide to produce nickel tetracarbonyl, which is a volatile complex. In the electrometallurgy of aluminum, the anode is graphite and the cathode iron is graphite lined .The O2 being liberated due to electrolysis reacts with the graphite anode to liberate CO2 and CO. Had it been any other metal besides graphite, the oxygen would have reacted with the aluminum during the electrolysis to form Al2O3. (c) Depressants prevent the formation of froth with air bubbles of other sulphide ores. Question 40. Delhi 2013) It can also be used for testing the purity of a compound. Question 55. (ii) Electrolytic refining (Delhi 2014) (i) Lower zone (zone of heat absorption) : E.g. Q7. The powdered bauxite ore is heated with cone. As the heater moves, the molten zone of the mod also moves along with it. SiO2 + CaO → CaSiO3 ( slag ). The end with impurities is cut off. • the volatile compound should be easily decomposable so that recovery is easy. Write chemical equations for the involved reactions. e.g. Question 3. (ii) Nickel is heated in a stream of carbon monoxide forming a volatile complex, nickel tetracarbonyl which is further subjected to higher temperature so that it is decomposed to give pure nickel. Wenn die Augen brennen und jucken:Trockenheit kann viele Ursachen haben. ‘. and froth stabilisers (e.g., cresols, aniline) which enhance non-wettability of the mineral particles and froth stabilisation respectively. (iii) Impure titanium into pure titanium. 6CaO + P4O10 → 2Ca2 (P04)2 Slag Reactions occur in blast furnace in the extraction of iron from iron oxide ores. (iii) Impure titanium into pure titanium (By Van Arkel method) : The impure titanium is heated in an evacuated vessel with iodine at 870 K. The covalent volatile titanium tetraiodide thus formed is separated which is then decomposed by heating over a tungsten filament at 2075 K to give pure titanium. Unit 6 - General Principles and Processes of Isolation of Elements NCERT Class 12 Chemistry Text Book for Blind and Visually Impaired Students by Dr T K Bansal. Solving these questions will help you to understand the chapter in a better way. (Comptt. 2C + O2 → 2CO, (ii) Zinc acts as a reducing agent which reduces complex of silver into silver (a) Which of the following ores can be concentrated by froth floatation method and why? Delhi 2012) pine oils, fatty acids etc. Question 76. (ii) Liquation (Comptt. Required fields are marked *. (a)Mond’s process: When impure nickel is heated is a current of CO at 330-350 K, it forms volatile nickel tetracarbonyl complex leaving behind the impurities. Answer: In this powdered ore is mixed with collectors (e.g. (ii) Vapour phase refining (Delhi 2014) Differentiate between a mineral and an ore. (All India 2011) Q3. The impurities of the metal deposits below the anode. How is the magnitude of 0 affected by : 4Ag + 8CN– + 2H2O + O2 → 4[Ag(CN)2]– + 4OH– Column chromatography is mostly used in order to take away those impurities which are not very different in chemical properties from the element which needs to be purified. Answer: BYJU’S provides NCERT notes, books, sample papers, previous year question papers, study materials, important questions, exercises, worksheets and assignments to help you in knowing concepts of metallurgy. The significance of leaching in the extraction of aluminium is to prepare pure alumina from the bauxite ore in the following steps : (iii)Limestone is decomposed to CaO ,which removes silica impurity of the ore as slag. (ii) Lead can be refined by liquation. (ii) Vapour phase refining (All India 2013) To remove FeO, silica is added during smelting. Answer: Answer: (Comptt. (Comptt. The word has been obtained from two Greek words; ‘graphy’ meaning ‘to write’ and ‘chroma’ meaning ‘colour’. ZnCO3 \(\stackrel{\Delta}{\longrightarrow}\) ZnO + CO2 ↑ (a) What is the principle behind ‘zone refining’ of metals? In this reaction Au+ ions are reduced to Au. Question 52. pine oils, fatty acids etc.) Answer: (iii) Vapour phase refining (Comptt. 2ZnS + 3O2 → 2ZnO + 2SO2 ↑ The solution of sodium meta-aluminate is neutralized by passing CO2 when hydrated alumina separates out while sodium silicate remains in the solution. Question 84. Why copper matte is put in silica lined converter? Hier sollte eine Beschreibung angezeigt werden, diese Seite lässt dies jedoch nicht zu. Thus, they cannot be used for the extraction of zinc using hydro-metallurgy. For example, ∆fGθ ( Al, Al2O3 ) is more negative than ∆fGθ ( Cu, Cu2O ), thus Al can readily reduce Cu2O to Cu but it is not possible for Cu to reduce Al2O3. 2Al + Cr2O3⇒ Al2O3 +2Cr; ∆fGθ = -827 – ( -540 ) = -287kJ / mol. The choice of stationary phase is done in a way that the elements of the mixture have different solubility in the phase. NaOH to form sodium aluminate and leaving impurities behind. For example: - Mond Process for Refining Nickel and van Arkel Method for Refining Zirconium or Titanium. Answer the following : As a result, pure metal crystallizes out of the melt and the impurities pass to the adjacent molten zone. Chromatography is a widely used process for separation, purification, identification and characterization of the different components of a mixture which are differently adsorbed on a suitable adsorbent. To extract zinc from zinc oxide it is mixed with powdered coke and then heated. Learning this chapter thoroughly plays an important role for the students who opt Chemistry at the higher level of education. Question 45. Sodium silicate cannot be precipitated so it is filtered off. Auf der Grundlage der vom 11. bis 31. NCERT Solutions for Class 12 Chemistry Chapter 6 General Principles and Processes of Isolation of Elements is the most important resource material that you need to prepare well for the CBSE Class 12 chemistry examination and competitive examinations.
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