Lesson no 8 metallurgy imp

                                Lesson no:-8 Metallurgy

                                      Chemical properties of metals

1. Reaction of metals with oxygen:-Metals combine with oxygen on heating in air and metal oxides are formed. Sodium and potassium are highly reactive metals. Sodium metal combines with oxygen in the air at room temperature to form sodium oxide.  For example : 4NaO(s)+O2(g)----->2Na2O(s) 
2. Reaction of metals with water :- Sodium and potassium react vigorously with water to evolve hydrogen. Calcium reacts with water less vigorously to evolve hydrogen. Magnesium reacts with hot water to evolve hydrogen. Aluminium, iron and zinc do not react with cold or hot but they react with steam to evolve their oxides and hydrogen.
3. Reaction of metals with acids:- Metals raect with dilute hydrochloric acid or dilute sulphuric acid to form metal chloride or metal sulphate and hydrogen gas. the rate of evolution of H2 is maximum in case of magnesium. The reactivity decrease in the order Mg>Al>Zn>Fe.
4. Reaction of metals with nitric acid:- Metals react with nitric acid to form nitrate salts. Depending on the concentration of nitric acid, various oxides of nitrogen (NO,NO2) are formed.
5. Aqua Regia:- Aqua Regia is freshly prepared by mixing concentrated hydrochloric acid and concentrated nitric acid in the ratio 3:1. Aqua Regia is a highly corrosive and fuming liquid. It is one of the few reagents which can dissolve the noble metals like gold and platinum.
6. Reactions of metals with salts of other:- The reactivity of all the metals is not the same. All the metals do not react with oxygen, water and acids. As a result, the relative ractivity of metals cannot be determined using these reagents. If a metal A displaces another metal B from the solution of its salt, it means that the metal A+Salt solution of metal B ----->Salt solution of metal A+metal B.                                                                                                                                                                                                     Reactivity series of metals The arrangement of metals in the increasing order or decreasing order of reactivity is called the reactivity is called the reactivity series of metals. Metals are divided into the following groups according to their reactivity.                                                                                          Chemical properties of non-metals
7. Reaction of metals with non-metals:- The ionic compound is formed when metal reacts with normal.           2Na+Cl2----->2NaCl(sodium chloride)        Ionic compound is formed as sodium loses one electron while chlorine accepts one electron. 
8. Reaction of non-metals with oxygen:- Non-metals combine with oxygen to form acidic oxides. In some cases, neutral oxides are formed.
9. Reaction of non-meatls with water:- Non-metals do not react with water, (exception-halogen). Chlorine dissolves in water giving the following reaction . Cl2(g)+H2O(l)------>HOCL(aq)+HCL(aq).
10. Reaction of dilute acid with non-metals:- Non-meatls do not react with dilute acids, (exception: halogen). Chlorine react with dilute hydrobromic acid to form bromine and HCl. 
11. Reaction of non-metals with hydrogen:- Non-metals react with hydrogen under certain conditions such as proper temperature, pressure and use catalyst.                                                                            Ionic compounds
12. Ionic compounds:- The compounds formed from units, i.e. cation and anion are called ionic compounds. An electrostatic force of attraction between oppositely charged ions (cations and anions) is called an ionic bond.
13. General properties of ionic compounds:- a) Ionic compounds are crystalline solids have a definite shape and hard due to strong electrostatic force of attraction between oppositely charged ions.                                                                                                                                  b)They are generally brittle. When pressure is applied they break into pieces.                              c)They have high melting and boiling points.                                                                              d)They are soluble in water and insoluble in solvents such as kerosene and petrol.                      e)They conduct electricity in the molten state and also in an aqueous solution.                                                                Metallurgy:Various concepts:
14. Minerals and ores:- The compounds of metals that occur in nature along with the impurities are called minerals. The minerals from which metals are extracted economically are called ores.
15. Metallurgy:- The process of extraction of metal in pure form from the ores. The metals are further purified by different methods of purification. All this process is called metallurgy.
16. Concentration of ores:- The process of separating gangue from the ores is called concentration of ores. Some general methods of concentration of ores as follows: a) Separating based on gravitation:-The gravitational method is used to separate the heavy particles of ores from the light  heavy particle of gangue. The process to do this separation as follows: 1)Wilfley table mathod .                                                            2)Hydraulic separation method.                                   b)Magnetic separation method.                                   c)Froth floatation method.                                             d)Leaching.
17. Extraction of reactive metals:-The extraction of highly reactive metals has to be done by electrolytic.
18. Extraction of aluminium:- Atomic number :13, Electronic configuration :2,8,3, Valency :3. Aluminum is extracted from its main ore bauxite (Al2O3.nH2O).                                                a)Concentration of bauxite ore:-Powdered bauxite is heated  with NaOH under high pressure and at 1400C to 1500C for 2 to 8 hours in a digester. Al2O3 being amphoteric in nature forms sodium aliminate (NaAlO2) which is water soluble. The iron oxide impurities does not dissolve in aqueous NaOH and are separated by filteration. However, silica reacts with sodium hydroxide to form soluble sodium silicate. NaAlO2 is hydrolysed to form insoluble Al(OH)3 by diluting it with water and cooling to 500C. Aliminium hydroxide precipitate is then filtered, dried and calcinated by heating at 10000C to obtain pure alumina.                                                b)Electrolytic reduction of alumina:- Cell-A steel tank with graphite lining; Electrolyte- Alumina dissolved in fused cryolite; Cathode-The graphite (carbon) rods dipped in the electrolyte; cryolite (Na3AlF6)and fluorspar (CaF2) are added in the mixture to lower its melting point 10000C. Electrolysis products: Cathode-Aluminium metal, Anode- oxygen gas.
19. Extraction of moderately reactive metals:- In metals, in the middle of the series such as iron, lead, copper are moderately reactive. These metals occur in the form of their sulphide salts or carbonates salts.
20. Extraction of less reactive metals :- The less reactive metals are at the bottom of reactivity series of metal. These metals are found in free state in nature. for example ,gold, silver, platinum. The reserves of copper in free state are exhausted long ago. 
21. Prevention of corrosion:- By coating with some substance on the metal with moisture and oxygen in the air is prevented and no reaction would occur between them.

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