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  Chemical Industries: Online Quiz quiz in Javascript Theories of Covalent Bonding and Shapes of Molecules Quiz Test Exams Question of Next Good Try! You Got out of answers correct! That's TryAgain

1. The naturally occuring metallic compounds are called as: a) ore b) gangue c) mineral d) rock ... Answer is c) Explanation: Mostly, metals exist in combined state (in compound form) with other elements rather than in free state with few exception. These compounds of metals are known as minerals. For example, iron exists as haematites (Fe 2 O 4 ) and magnetsite (Fe 4 O 4 . Haematites (Fe 2 O 4 ) and magnetsite (Fe 4 O 4 are minerals of iron. show Answer 2. The separation of minerals from gangue is called concentration. Which of the following methods is used for concentration? a) semelting b) roasting c) refining d) floatation ... Answer is d) Floatation: Floatation is the process in which ore particles are agitated with mixture of oil and detergents. Mineral particles rise on the top as froth, from where it is sepearated. Copper ore is generally concentrated by this method. show Answer 3. Which of the...

Determining oxidation state of an atom in a compound Example : A device called Breathalyzer is used by police to test a person’s health for alcohol. It contains an acidic solution of potassium dichromate K2Cr2O7. It is a strong oxidizing agent. Determine oxidation state . Important Note Remember, before determining oxidation state, one must know oxidation state of elements in following table.                             Solution   Oxidation state of K = +1 Oxidation state of O = -2 Oxidation state of Cr = X Since, the algebraic sum of oxidation state of all atoms in a neutral molecule or formula unit is zero. So, 2(Oxidation state of K) +2(Oxidation state of Cr) + 7(Oxidation state of O) = 0 2(+1) +2 (Oxidation state of Cr)+ 7(-2) = 0 +2 +2 (X) -14 =0 2 (X) -12 =0 2 (X) =+12 X = +6 Oxidation state of Cr = +6 Example: Boric acid (H3BO3) is used in eye wash . What is the oxidation state of B in this acid? Sol...

Question: Describe Solvay process. Answer. Solvay Process A process in which sodium carbonate is obtained from lime stone, ammonia and brine is known as Solvay process. Solvay Process  consists of following steps 1. Preparation of Ammonical Brine Ammonical brine is prepared by dissolving ammonia gas in brine. Ammonical brine is transferred into carbonating tower 2. Carbonation In carbonating tower, carbon dioxide is passed through ammonical brine and following reaction take place.   At the bottom of tower, NaHCO3 is precipitated out by keeping temperature  at 15 Oc. 3. Filtration Precipitates of NaHCO3 are separated from the milky solution by filtration. It is used as baking soda. 4. Calcination Sodium hydrogen carbonate is heated to get sodium carbonate. Carbon dioxide released is re-cycled in the process. 5. Preparation of Carbon dioxide and slaked line Carbon dioxide is produced by heating the lime stone in kiln. CO2 is fed into the carbonating tower from ...

Self Assessment Exercise   1. List important ores of iron, copper, zinc and mercury  2. List out basic metallurgical operations.  3. List main processes used to concentrate the ore.  4. Write names of methods used in the extraction of a metal from its concentrated ores.  5. List methods used to purify metals.  Answer.  1.  Iron ores  a. Haematite (Fe2O3)  b. Magnesite (Fe3O4)  Copper ores Chalcopyrite (CuFeS2)  Zinc ore Zinc blend (ZnS)  Murcury ore  Cinnabar (HgS)  2. Basic metallurgical operatio ns i.  Crushing, grinding or pulverizing of the ore ii. Concentration of the ore  iii. Extraction of metals iv.  Refining of metals  3. Main process in used in concentration of ores i.  Magnetic separation ii. Cyclone separation  iii. Floatation process  4. Names of methods used in the extraction of a metal from its concentrated ores   i.   Roas...

Electro-refining   An electro-refining is performed in an electrolytic cell for purification of metals. In this method, impure metal is used as anode and pure metal (same metal as in anode) is used as cathode. For example, electro-refining of copper is carried out in an electrolytic tank containing copper sulphate solution as electrolyte.   On passing electric current through an electrolyte, impure copper dissolves and converts into Cu2+ ions. These Cu2+ ions gain electrons at cathode and form Cu atoms, which get deposited at the cathode. During the process, anode becomes thinner and thinner and cathode becomes large. The impurities like Au and Ag fall off the anode as anode mud.   Following reactions occur during the electro-refining.  Anode Reaction:  Cathode Reaction:       Distillation: Metals with relatively melting points such as As and Hg are purified by distillation. Next  Back to Main Page

Extraction of Metals   After separation of gangue, mineral is passed through some chemical process to extract the pure metal from it. Followings are main chemical processes used for extraction of metals.  a. Roasting  b. Smelting  c. Refining or purification of metals  a. Roasting   The process in which minerals are converted into their oxides by heating in the air at temperature below their melting point is called roasting. Examples of roasting are given below.  b. Smelting   Reduction of the metals ions to free metal is called smelting. The most common reducing agents are coke, carbon monoxide and hydrogen. Some examples are:  Smelting of copper ore is done in two steps.  i. In first step, the roasted copper ore is heated with coke and sand at about 1100 oC. The minerals melt and separate into it two layers. The bottom layer that contains mixture of CuS and FeS is also known as matte. The upper layer is a silicate s...

Question: Describe cyclone separation and floatation process. Answer . Cyclone Separation   When there is a large density difference between ore and impurities, cyclone separation is used. In this method, air is passed through pulverized ore under high pressure. Lighter particles are blown away through the top and heavy particles of ores are stuck to walls by centrifugal force and falls down the funnel.  Cyclone Separator Floatation Process:    In this process, pulverized ore is fed into a tank containing water and oil detergents mixture. The mixture is continuously shaken with flow of air. Detergent-oil mixture only binds with mineral particles leaving gangue particles behind. Thus, mineral particles rise to the surface as froth where they are skimmed off. The gangue particles fall down the bottom. Floatation method is used for concentration of copper ore. Previous   Next

Question:  Describe concentration of minerals. Answer . 1. Concentration After mining, ore undergoes crushing, grinding or pulverizing step and converted into the powdered form. Then mineral is separated from gangues from by some physical methods.  This process of separation of minerals is called concentration.  The method of separation of minerals depends upon the nature of material. Some important methods are given as follows.  i. Magnetic Separation ii. Cyclone separation iii. Floatation Process i. Magnetic Separation For magnetic ore, a magnet is used to remove minerals from gangues. In this process, the powered ore is dropped over a moving belt. Belt moves over two wheels, one of which is magnetic. Magnetic wheel attracts magnetic ore as it comes near to it. As a result, ore falls further away later than impurities. Previous   Next Back to Main Page

Question: Define following terms.     i. Minerals     ii. Ore       iii. Gangue  Answer .   Minerals The naturally occurring metallic compounds are called minerals. For example Iron is found naturally as hematite (Fe2O3) and magnetite (Fe3O4). Here, hematite and magnetite are minerals of Iron.  Ore A solid deposit containing sufficient percentage of a mineral from which extraction of metal is convenient and economical is called an ore.  Gangue The debris, such as sand, rock and clay attached with the mineral is known as grange.  Question: What is metallurgy? Enlist main steps involved in metallurgy.  Answer .  Metallurgy The process of separating a metal from its ore and preparing it for use is called metallurgy. The main steps in metallurgy are given as follows.  1. Mining 2. Crushing, grinding or pulverizing of ore  3. Concentration of the ore  4. Extr...