134 UNIT 2 UNIT 3 INDUSTRIAL CHEMISTRY Unit outcomes At the end of this unit, you will be able to list the renewable and non-renewable natural resources and appreciate their importance to the industry as raw materials describe the relationship between natural resources and industry list some chemicals and related industries in Ethiopia list some important chemicals used for the manufacture of valuable products explain the major steps in the industrial production of ammonia, nitrica acid, sulphuric acid, sodium hydroxide, sodium carbonate and aluminum sulphate and di-ammonium phosphate and other Nitrogen fertilizers; and list some important direct uses of NH, HNO,. HSO,, and Na,CO, and their uses as raw materials in the production of other products list some important uses of DAP, (NH), HPO,, nitrogen fertilizers, insecticides and Herbicides prepare insecticides from locally available material describe the uses of the common insecticides and pesticides that are manufactured in chemical industries discuss the important steps in the production of glass, ceramics, cement, sugar and paper and pulp describe the important steps in the production of soaps and detergent, and beverage prepare soap on a small scale from the available resources describe the tanning process UNIT! 135 CHEMISTRY GRADE 1 apply local methods of tanning use local methods of food preservation develop inquiry skills along this unit: observing, predicting, classifying, communicating, and inferring. Start-up Activity From your grade 10 lesson, you have learnt about the occurrence and extraction of some important metals and non-metals. Thus in small groups discuss and present to the class the occurrence and importance of some metals and non-metal that are used as a raw material for the production of desired products. 3.1 Introduction At the end of this section, you will be able to: define industrial chemistry list general characteristics of chemical industries mention the role of industrial chemistry in the society Activity 3.1 Discuss in groups of three and comment on the following statement "It is very difficult to think of life without the chemical industry." 2. List at least five products that are manufactured by Ethiopian chemical industries. Then, report your answer to your classmates. The 19h century industrial revolution began the development of chemical industries at a very high rate. Following this, the demand for goods produced through chemical processes increased. Today, chemical industries in both developed and developing countries produce a number of very useful products. This includes synthetic fibers, plastics, rubber fertilizers, dyes, drugs and many other products. (136 UNIT 3 144 Introduction Chemistry and chemical technology are very important for economic growth and development especially for developing countries like Ethiopia. Ethiopia has minerals (metal ores) deposits which are sources of iron, lead, copper, gold, platinum, tantalum and many rare-earth metals. Moreover, rock salt gypsum, coal, and crude oil are found. So, Ethiopia needs industrial revolution to use its mineral deposits to produce various chemicals on a large scale. So, in this context, what is meant by industrial Chemistry? Industrial chemistry is a branch of chemistry which applies physical and chemical procedures toward the transformation of natural raw materials and their derivatives in to products that have beneficial to humanity.Grade 12 Books: New Curriculum and many rare-earth metals. Moreover, rock salt gypsum, coal, and crude oil are found. So, Ethiopia needs industrial revolution to use its mineral deposits to produce various chemicals on a large scale. So, in this context, what is meant by industrial Chemistry? Industrial chemistry is a branch of chemistry which applies physical and chemical procedures toward the transformation of natural raw materials and their derivatives in to products that have beneficial to humanity. Industrial chemistry differs from classical chemistry in that it closes the gap created in concepts between chemistry as it is taught in schools, and chemistry as it is practiced commercially. Industrial chemistry is the basis of the chemical industry. The chemical industry is an institution involved in producing chemical products such as food, medicine, building materials, plastics, etc. The chemical industry involves the use of chemical processes such as chemical reactions and refining methods to produce a wide variety of materials with desirable properties and quality to satisfy social needs. Most of these products, in turn, can be used by other chemical industries to manufacture other items or can be used directly by consumers. Generally, chemical industries use naturally or artificially available raw materials to produce the desired products. involve chemical reactions to transform raw materials into finished and semi finishe products. consume relatively large quantities of energy during the manufacturing process. use safe operation methods in their manufacturing processes, and test their products during and after manufacture in their quality control laboratories to ensure that the products meet the required specifications. UNIT 3 137 CHEMISTRY GRADE Exercise 3.1 Define "industrial chemistry"? Discuss how chemical industries are considered to be the prominent one when dealing with manufacturing industries.. 3. List the characteristics of chemical industries. 3.2 Natural Resources and Industry At the end of this section, you will be able to: define natural resources list the types of natural resources classify chemical industries based on the raw materials they use to manufacture their products classify chemical industries based on the type product they manufactured describe the applications of minerals in industry. T Activity 3.2 Discuss the following questions in groups and present your findings tor your classmates. 1. How can animals and plants be replaced once they die? What are fossil fuels? Can fossil fuels renewed? Explain the importance of natural resources for chemical industries using examples? 146 (138 UNIT 3 Natural Resources and Industry 146/298 3.2.1 Natural Resources (Raw Materials) Natural resources e the raw materials for the chemical industry which are obtained from the natural environment. The raw materials are obtained from the different components of the natural environment. These are listed below From the atmosphere: The earth's atmosphere has approximately 5 x 10¹ tons of gases. It is composed of different gases namely N,, O, CO, Ne, Ar, Kr and Xe. They are important industrial raw materials. Thus, the natural supply of these gases is unlimited. From the hydrosphere: Ocean water which amounts to about 1.5 × 102 liters3.2.1 Natural Resources (Raw Materials) Natural resources are the raw materials for the chemical industry which are obtained from the natural environment. The raw materials are obtained from the different components of the natural environment. These are listed below From the atmosphere: The earth's atmosphere has approximately 5 x 10' tons of gases. It is composed of different gases namely N,. O,. CO. Ne. Ar. Kr and Xe. They are important industrial raw materials. Thus, the natural supply of these gases is unlimited. From the hydrosphere: Ocean water which amounts to about 1.5 x 10 liters contains about 3.5 percent mass dissolved material. Seawater is a good source of sodium chloride, magnesium and bromine.. From the lithosphere: The vast majority of elements are obtained from the earth's crust in the form of mineral ores, carbon and hydrocarbons. Coal, natural gas and crude petroleum besides being energy sources are also converted to thousands of chemicals. From the biosphere: Vegetation and animals contribute raw materials to the so-called agro-based industries. Oils, fats, waxes, resins, sugar, natural fibres and leather are examples of thousands of natural products. Classification of Natural Resources - Natural resources can be classified as renewable and non-renewable resources.. Renewable resources: The resources that can be replenished through rapid natural cycles are known as renewable resources. These resources are able to increase their abundance through reproduction and utilization of simple substances. Examples of renewable resources plants, (crops and forests) and animals which are being replaced from time to time because they have the power to reproduce and maintain life cycles. There are also renewable resources without any life cycle. These include wood and wood-products, natural rubber, fibers (e.g.; cotton, jute, animal wool, silk, and synthetic fibers), pulp products, and leather. Furthermore, resources, water, and soil are also classified as renewable resources. Moreover, solar energy is considered a renewable resource as much as solar stocks are inexhaustible on the human scale. UNIT 3 139 CHEMISTRY GRADE 12 Non-Renewable Resources: The resources that cannot be replenished (regenerated) through natural processes are known as non-renewable resources. These are available in limited amounts and cannot be increased. These resources include fossil fuels (petrol, coal etc.), metals (iron, copper, gold, silver, lead, zinc etc.), minerals and salts (carbonates, phosphates, nitrates etc.). Once a non-renewable resource is consumed, it is gone forever. Thus, a substitute for it is necessary. Activity 3.3 Although renewable resources can be replenished by natural process they are practically getting depleted. Similarly nonrenewable resources are also over used that they may exhausted shortly. Think how chemical knowledge can be used to tackle such problems and share your views to the class? 3.2.2 Industry Industry is a well-organized facility with a high degree of automation and specialization where large-scale manufacturing of goods take place. Nevertheless, it can also include other commercial activities that provide goods and services such as agriculture, transportation, hospitality, and many others. Manufacturing industry: Manufacturing industry is a compartment industry economy which is concerned with the production or making of goods out of rawa materials by means of a system of organized labor. Classification of manufacturing industry Manufacturing industries use different type of raw materials, skills, and technologies. As a result, different types of products are manufactured. 140 UNIT 3 148/298 Natural Resources and Industry Chemical Industry: Chemical industry is a facility where industrial chemicals are. manufactured. The products result from: a. Chemical reaction between organic materials, or inorganic materials, or both b. Extraction, separation, or purification of natural products, with or without the aid of chemical reactions c. The preparation of specifically valuable materialsChemical Industry: Chemical industry is a facility where industrial chemicals are manufactured. The products result from: a. Chemical reaction between organic materials, or inorganic materials, or both b. Extraction, separation, or purification of natural products, with or without the aid of chemical reactions c. The preparation of specifically valuable materials Classification of the chemical industry based on raw material used for production 1. Chemical industries use natural raw materials (resources) For example, Sugar industries use sugar cane to manufacture sugar. 2. Chemical industries use products from other industries to manufacture their products. For example: Detergent and soap manufacturing industries use preprocessed products like caustic soda, caustic potash and related compounds to manufacture their products. Classification based on the product typea Examples are: Food processing industries, Beverages industries Textiles industries. Wearing apparel industries. Leather industries Paper and chemical industries etc. Exercise 3.2 1. List the types of manufacturing industries based on their products. 2. Give examples of renewable and non-renewable natural resources UNIT 3 141 CHEMISTRY GRADE 12 3.3 Manufacturing of Valuable Products/Chemicals At the end of this section, you will be able to describe the general methods of "manufacturing of valuable products in industries" explain the important steps for the production of NH, in Haber process use Lechaterier's principles to explain how the yield of ammonia can increased in Haber process consult the internet or other reference materials to inspect some important direct uses of HSO,, HNO, and Na CO, examine the physical and chemical properties of H SO, HNO, and Na Co describe the important steps for the production of HNO, in Ostwald Process list the physical and chemical properties of HNO, explain how the production of H SO is considered as the vital to measure the development of a Nation draw the schematic diagram which shows the steps followed in the production of H SO in contact process state the raw material used to manufacture Na CO draw the schematic diagram which shows the steps followed production of Na CO in Solvay process discuss the uses of DAP, (NH), HPO. Nitrogen fertilizers, herbicides and insecticides in the agriculture sector apply indegenious knowledge to produce natural compost use local resources to prepare insecticides. Manufacturing some valuable products: Manufacturing of valuable products involve a number of chemical processes. The process is designed to produce a desired product from a variety of starting raw materials using energy through a succession c treatment steps integrated in a rational fashion (Figure 3.1). The treatment steps could be either physical or chemical in nature. 142 UNIT 3 Manufacturing of Valuable Products/ Chemicals Input (raw material) Transformation (Process) Product (Output) 150/298 Figure 3.1: Basic steps in a manufacturing process. Open Chemistry Guide BookInput (raw material) Transformation (Process) Product (Output) Figure 3.1: Basic steps in a manufacturing process. Valuable products include every industrial product. These products are either directly used or serve as raw materials to synthesize products that are important to solve the society demands in different necessities. Both organic and inorganic chemicals could be used in the manufacturing process. 3.3.1 Ammonia (NH) Activity 3.4 Discuss in group and present your answer to the class. 1. Why ammonia is highly soluble in water? 2. List and describe the conditions that are required to get high yield of ammonia using Le Chatelier's principle? NH,+H,0NH+OH Properties Ammonia is lighter than with a density of 0.769 kg/m³ at STP. Ammonia is commercially and commonly available an aqueous solution; the most common commercial formulation is 28-30% NH,. In the aqueous solution ammonia is partially ionized according to the equilibrium: and it is often referred to as ammonium hydroxide. It is a weak base. It is colorless with sharp and intensely irritating gas at room temperature. melting point is -77.7 °C. Its boiling point is -33.35 °C. Its solubility in water at 25 °C is 34% (w/w). UNIT 3 143 151 CHEMISTRY GRADE 12 2NH,Cl + Ca(OH),→ CaCl,+ 2H20 + 2NH,(8) Uses Ammonia is an important compound, essential to man for a variety of diverse uses. It is used as a cleaning agent, antimicrobial agent, a raw material for the production of nitrogen fertilizers, raw material in the manufacturing of explosives such as nitrocellulose and trinitrotoluene (TNT), used in the production of soda ash and in the Ostwald process to get nitric acid etc. Such a diverse applicability has caused large demand for its production. Preparation Ammonia is easily made in the laboratory by heating an ammonium salt, such as ammonium chloride NH Cl with a strong alkali, such as sodium hydroxide or calcium hydroxide. The gas may also is made by warming concentrated ammonium hydroxide. However, its diverse applicability has caused large demand for its production. The development of the Haber-Bosch process for ammonia production has made it possible to meet this demand. So, the principal commercial method of production of ammonia is the Haber process, the direct combination of nitrogen and hydrogen under high pressure in the presence of a catalyst. The Haber process was found by the German chemist. Fritz Haber, in the early 20 century. It involved the practical use of atmospheric hydrogen and nitrogen to produce ammonia. Carl Bosch was tasked with scaling up the process to an industrial production. The efforts of both these men were recognized in the form of Nobel prizes that were awarded to them in 1918 and 1931, respectively. This also led to the process being called the Haber-Bosch process. Presently, about 454 million tons of nitrogen fertilizers are produced using the Haber-Bosch process. They are extensively used to increase crop yields. 144 UNIT 3Steps Involved in Ammonia Production Step 1: The primary requirements for the production of ammonia are hydrogen (H) and nitrogen (N). H, was initially obtained by electrolyzing water, thus, recent times, this method has been replaced by the use of methane as a source. splitting the water molecule into its components - hydrogen and oxygen. In Methane is easily acquired from natural gas, and requires very less external energy to produce hydrogen. The other substrate, nitrogen, is obtained by carrying out fractional distillation of air. Step 2: The hydrogen and nitrogen are then, introduced into a chamber containing iron particles or lined internally with iron, and a pressure of 15-25 MPa at a temperature of 300 - 500 °C is applied to the gases. These conditions cause the gases to react and produce ammonia, and the following reaction occurs: Step 3: The hot mixture of gases is then passed through a condenser. Since ammonia condenses easily as compared to nitrogen and hydrogen, the liquefied ammonia is collected and removed, and the leftover nitrogen and hydrogen gases are re-introduced into the reactor. Thus, pressure is maintained, and there is no loss or wastage of reactants. This recycling of the raw materials allows a 97% conversion of initial reactants into ammonia, which is, then, used to produce a variety of products. The steps are shown in Figure 3.2. Leftover H, + N Coolant NH, ammoniaa Condesner H,+N Catalyst Reactor Figure 3.2: production of NH,using Haber-Bosch process UNIT 3 145 CHEMISTRY GRADE 12 Experiment 3.1 Preparation and Testing of Ammonia Objective: to prepare ammonia to test its solubility to test its alkaline nature Material Requireda Eye protection or eye goggles, stand and clamp, a dried boiling tube with stopper and delivery tube (see diagram below), beaker 100 mL, beaker, 250 mL or bigger, Bunsen burner, spatula and test tube to collect ammonia gas. Chemicals Required a Ammonium chloride, Calcium hydroxide, Calcium oxide, Concentrated hydrochloric acid, red litmus paper, blue litmus paper and Universal indicator paper. Safety Precautions Wear eye protection throughout. Ammonia gas is toxic and dangerous for the environment and pungent-smelling and must not be inhaled. The experiments must only be carried out in a fume cupboard or in a well-ventilated laboratory. Procedure 1. In a 100 ml beaker, mix 2 spatulas of the ammonium chloride with 2 spatulas of the calcium hydroxide together. The two solids begin to react immediately on mixing. Hold a piece of each color of litmus paper over the mixture and observe the 2. color change. Test also with a piece of universal indicator paper. 3. Transfer the mixture of ammonium chloride and calcium hydroxide into a boiling tube and set up the apparatus as shown in the diagram. 154 146 UNIT 3 Manufacturing of Valuable Products/ Chemicals* Grade 12 Books: New Curriculum Delivery Ammonium chloride and calcium hydroxide Stand Figure 3.3: The setup required for producing ammonia gas 4. Optional: put the lump of calcium oxide into the boiling tube containing the ammonium chloride/calcium hydroxide mixture. The calcium oxide will absorb the water produced in the reaction and ensure that the ammonia gas is dry. 5. Gently warm the reaction mixture.. 6. Collect a test tube which contains a few drops of concentrated hydrochloric acid. Remove the stopper from this test tube and hold the open end near the end of the ammonia gas delivery tube. Observe what happens. Replace the stopper on the test tube of hydrochloric acid and return the test tube to its original place. Two-thirds fill a large beaker with water. This is needed for step 10. Continue to gently warm the reaction mixture. Hold one of the dry boiling tubes in position as shown in the diagram below. Notice that the ammonia is collected with the boiling tube upside down. This is because ammonia less dense than air. UNIT 3 147 CHEMISTRY GRADE 12 nmoina gas Delivery Boiling t 156 Ammonium chloride and calcium hydroxide Stand Figure 3.4: The equipment setup required to collect the ammonia gas. Test around the open end of the collecting boiling tube with universal Indicator paper to check that the collecting tube is full of ammonia. 10. Hold the tube ammonia upside down then quickly put it, mouth stilla downwards, into water in a beaker. The ammonia dissolves in the water and a the level of the water should rise up inside the test tube. If you want to try this a second time, use a fresh dry boiling tube.. Ammoina gas Water Figure 3.5: A setup showing ammonia gas dissolved in water Observation and Analysis A. Why a dried boiling tube is required? What is the purpose of putting the lump of calcium oxide into the boiling tube containing the ammonium chloride/calcium hydroxide mixture? What do you think is the white fume ('smoke') that is produced when the ammonia gas is collected into the HCI? D. What is the nature of ammonia? Is it alkaline or acidic gas? If it is alkaline, please write the reaction equation that shows its alkalinity? 148 UNIT 3 Manufacturing of Valuable Products/ Chemicals 156/298 Experiment 3.2 Ammonia Fountain Demonstration Objective: To make a miniature chemical fountain using only soluble ammonia and atmospheric pressure Materials Required Open Chemistry Guide BookObjective: To make a miniature chemical fountain using only soluble ammonia and atmospheric pressure Materials Required Water, 2-L round bottomed flask, 2-L beaker, 2-hole stopper syringe, Glass tube connected with rubber tube, stand with ring and clamp, test tube, tong, bunsen burner and heat proof mat Chemicals Required NH Cl and NaOH or NH OH (ammonia solution) or dry NH, gas, water and Phenolphthalein Procedure: (1) Preparing dry ammonia and filling the flask a. Set up the flasks as shown in Figures 3.6a and 3.6b Add 50 ml of concentrated ammonia solution to a 100 mL test tube c. place the test tube in a test tube holder and fit it into the mouth of conical flask that is inverted upside down and supported by stand Heat the test tube with Bunsen burner while holding it with a test tube holder so that ammonia gas produced is collected by the upward displacement of air. Alternatively, use a 1:1 mixture of NH Cl: NaOH in the conical flask (II) Demonstration (Figure 3.6b) e. Fill the beaker with water. To this, add 1 mL of phenolphthalein indicator solution. UNIT 3 149 157 CHEMISTRY GRADE 12 f. Position a clamp so that the flask will be held with the tube well below the level of the water. Bear in mind that the flask will be heavy when filled with water so take care that it will not overbalance g. fill the syringe with water, dry the nozzle and carefully fit it into the second hole of the two-holed stopper (see diagram). Remove the plain stopper from the inverted gas-filled flask and quickly fit the stopper which holds the jet and syringe. Be careful not to prematurely inject Use the syringe to squirt a few mL of water into the flask. water from the syringe. As the gas dissolves, a partial vacuum forms inside the flask and the external air pressure will force water up the tube and through the jet - forming fountain. The ammonia gas dissolves in the water emerging from the jet and the indicator changes colour. The fountain continues for some minutes, depending on the size of the flask and the width of the jet. When the fountain finishes, a bubble of gas remains.. Stand NH, gas Round-bottom flask Test tube NH, solution Bunsen burner Figure 3.6a: Generation of ammonia 150 UNIT 3Manufacturing of Valuable Products/ Chemicals Stand NHI, gas Round-bottom flask Dropper with water (syringe) Rubber tube Water with indicator Figure 3.6b: Set-up of ammonia fountain demonstration Experiment Observation and Analysis A. What happens to the colour of the soultion after addition of phenoolphtalin? What does its change shows? B. As ammonia (NH,) getting dissolved in the water what will happen? C. Why does fountain formed in flask? Exercise 3.3 Write a balanced chemical equation for the formation of ammonia by the Haber process. What is the purpose of adding finely divided iron in the Haber process? 2. 3. Why are high temperature conditions required in production of ammonia in the Haber process? 4. Predict the product formed and write the reaction equation when you heat an ammonium salt, such as ammonium chloride NH Cl, with a strong alkali, such as sodium hydroxide or calcium hydroxide, in a laboratory. UNIT 3 151 160/298 CHEMISTRY GRADE 12 3.3.2 Nitric Acid Activity 3.5 4HNO, (1) 4NO, (g)+ O, (g)+ 2H,O(1) brown Discuss in a group and present your answer to the class. Why is nitric acid considered a highly corrosive mineral acid? 2. Why is nitric acid used to manufacture explosives such as trinitrotoluene (TNT) and nitroglycerine? Properties Pure nitric acid has a density of 1.51 g/em³. It is a colorless liquid, with a highly pungent odor, in appearance similar to water, but on exposure to light, it turns brown because of slight decomposition into NO, (brown) and O, Nitric acid is a strong acid and dissociates completely to give H,0 and NO, in a which are typically very soluble in water. Nitric Acid is a highly corrosive mineral acid. Nitric acid and its salts are strong oxidizing agents, particularly when it is hot and concentrated. This fact explains the violence of the reactions with metals, which result dilute aqueous solution. Nitric acid forms a large number of salts, called nitrates, even explosive. in the release of hydrogen. It reacts readily with numerous substances and produces. heat when dissolved in water. A significant proportion of reactions involving it are Concentrated nitric acid is highly hazardous to health. Upon contact with the skin, causes severe burns and even necrosis.. Uses Neutralization of nitric acid with ammonia results in ammonium nitrate - the most important component of mineral fertilizers used worldwide. In addition, HNO can be used soil acidification in horticulture. In the chemical industry, nitric acid primarily a precursor to organic nitrogen compounds, such as nitrobenzenes. When combined with aromatic compounds, it yields substances used to make explosives such as TNT and nitroglycerine. 152 UNIT 3 Manufacturing of Valuable Products/ Chemicals Another important application is rocket fuel. For this purpose, a mixture of HNO, dinitrogen tetroxide and hydrogen peroxide, also known as red fuming nitric acid, is prepared. Nitric acid's potential for plastic production is also noteworthy. Other less Open Chemistry Guide Book 160Another important application is rocket fuel. For this purpose, a mixture of HNO, dinitrogen tetroxide and hydrogen peroxide, also known as red fuming nitric acid, prepared. Nitric acid's potential for plastic production is also noteworthy. Other less popular uses of nitric acid include: production of organic dyes and lacquers; pharmaceutical industry; production of fungicides; cleaning and etching of metal surfaces; refining of precious metals for the jewellery industry (in preparation of aquaregia); the artificial ageing of wood to obtain the desired shade: production of household cleaning products; detection of traces of metals in laboratory test substances. Preparation Nitric acid can be obtained by reacting nitrogen dioxide with water. Under laboratory conditions, an alternative production method is the reaction of potassium nitrate with sulphuric acid to produce pure nitric acid. 2KNO, + H,SO, → K,SO, + 2HNO, (Salt of more volatile acid + less volatile acid → displaces more volatile acid). There is a basic principle that a more volatile acid can be displaced from its salt by a less volatile acid. For commercial purposes, the basic production method is the so-called Ostwald process. This is the catalytic oxidation of ammonia to nitric oxide, which, using special absorption towers, yields concentrated HNO, acid. For purchase, a concentration of 65-68% is most desirable. Ostwald processes: The principle or mechanism behind the Ostwald process is "the conversion of ammonia to nitric acid simply occurs as a result of oxidation. This particular oxidation reaction gives us the corresponding nitric oxide. Further, when the nitric oxide is oxidized nitrous gases are formed, and those gases can trap water molecules. As a result. obtain nitric acid. Catalytic oxidation involving O, is used where ammonia will give rise to the product." UNIT 3 153 CHEMISTRY GRADE 12 Production of Nitric Acid Nitric acid is produced industrially from ammonia by the three-step Ostwald process: Step 1: Ammonia is burned in excess oxygen over a platinum catalyst to form nitric oxide (NO): 4NH, (8)+50, (8) 4NO(8) + 6H,0(8) Step 2: Additional air is added to cool the mixture and oxidize NO to NO,: 2NO(8)+ 0, (8) 2NO,(8) Step 3: The NO, gas is bubbled into the warm water, where it reacts to give nitric acid and nitric oxide: 3NO, (8)+ H2O(1) → 2NHO, (aq)+ NO(8) The nitric oxide (NO) is recycled in Step 2. The production of nitric acid with the Ostwald process is summarized in Figure 3.7. 850-1000 °c Pt/Pd catalyst HNO, NO HO Figure 3.7: Simplified diagrams that show the Nitric acid manufacturing process 154 UNIT 3 Manufacturing of Valuable Products/ ChemicalsPreparation of Nitric Acid in Laboratory Objective: To prepare nitric acid in laboratory Materials Required Round-bottomed borosilicate flask (Preferably thick-walled), delivery tube, glass stopper, glass retort, Tripod stand, Bunsen burner, ice-cold water Chemicals Required Potassium Nitrate and concentrated sulphuric acid Safety Precautions Concentrated nitric acid is corrosive and oxidizing - wear goggles or face shield. The use of nitrile gloves is recommended. Procedure 1. Place a 50 gm of potassium nitrate (KNO,) and 25ml of concentrated sulphuric acid (HSO) in a round bottom flask 2. Heat the reactants to about 200 °C taking care that the temperature does not cross 200 °C 3. Observe nitric acid's vapors cooled and condensed to a brown liquid in a receiver cooled under cold water. See its collection as shown in the diagrama below. Glass stopper Glass retort Clamp stand Conc. H,SO, +KNO, Nitric acid Tripod stand bum Round bottom flask Ice cold water Figure 3.8: Set-up of laboratory preparation of Nitric acid Observation and Analysis What do you observe in the formation of nitric acid in this experiment? Write a reaction equation that explaining Nitric acid's formation in this experiment. UNIT 3 155 CHEMISTRY GRADE 12 Experiment 3.4 Properties of Nitric Acid Objective: To investigate oxidizing property of Nitric acid Materials Requireda round-bottomed borosilicate flask (Preferably thick-walled), clamp stand, delivery tube, test tube, tong, glass wool bowl or trough safety screens (if in an open lab). Chemicals Required 5 g copper turnings and 40 ml concentrated nitric acid Safety Precautions Concentrated nitric acid is corrosive and oxidizing - wear goggles or a face shield. The use of nitrile gloves is recommended. Procedure 1. Fill the test tube flask with water and add the acid to the round-bottomed flask 2. Clamp the round bottomed flask into position and check that the delivery tube, when in place, is at the bottom of the flask 3. Loosely plug the neck of conical flask with glass wool, leaving delivery tube in position, ready to be removed when the copper is added 4. Add the copper and fit the delivery tube. 5. After about 80 seconds, the reaction will slow and observe what will happen 6. The setup for the experiment is represented in the figure below 164 156 UNIT 3Manufacturing of Valuable Products/ Chemicals Stand Delivery tube Round bottom flask Test tube Figure 3.9. Set up for reaction of nitric acid with Copper Observation and Analysis A. As the copper is added, what color is observed or developed in the solution? B. What gas evolved during the reaction? what is the color of this gas? Write the reaction equation, which shows the reaction of copper with concentrated nitric acid. Exercise 3.4 Describe the properties of nitric acid. 2. State the preparation of nitric acid by the Ostwald process. 3. What are the main uses of nitric acid? Predict the product of the reaction between potassium nitrate with sulphuric acid. UNIT 3 157 3.3.3 CHEMISTRY GRADE 12 Nitrogen-Based Fertilizers Activity 3.6 Discuss in a group and present your opinion to your classmates. 1. Describe why a large-scale use of synthetic fertilizers can be harmfula to the environment 2. What is the purpose of adding nitrogen stabilizers in the soil after the addition of nitrogen-based fertilizers? What is the role of nitrifying bacteria in the reaction of nitrogen-based fertilizers? The common forms of N-based fertilizer include anhydrous ammonia, urea, urea ammonium nitrate (UAN) solutions and Diammonium Monohydrogen Phosphate (DAP) with represented by chemical formula (NH) HPO Anhydrous Ammonia Anhydrous ammonia (NH) is the most basic form of nitrogen fertilizer. Ammonia, a gas at atmospheric pressure, must be compressed into a liquid for transport, storage and application. Consequently, it is applied from a pressurized tank and must injected into the soil to prevent its escape into the air. Although almost 80 percent of the earth's atmosphere is comprised of nitrogen, it is in a chemically and biologically unusable form for plants. Using a complex method called the Haber-Bosch process (refer section 3.3.1 for this process), nitrogen captured from the air, combined with a hydrogen source and converted into a form that can be used by growing plants. Ammonia in this form is also known as ammonia gas or anhydrous ("without water") ammonia. 166 (158 UNIT 3 Manufacturing of Valuable Products/ Chemicals 166/298 Application Anhydrous ammonia is applied by injection 6 to 8 inches below the soil surface to minimize escane of gaseous NH into the air. NH is a very hverosconic comnound Open Chemistry Guide BookApplication Anhydrous ammonia is applied by injection 6 to 8 inches below the soil surface to minimize escape of gaseous NH, into the air. NH, is a very hygroscopic compound and once in the soil, reacts quickly with water and changes to the ammonium (NH) form. As a positively charged ion, it reacts and binds with negatively charged soil constituents including clay and organic matter. Thus, it is held on the soil exchange complex and is not subject to movement with water. Soil reactions Over time and with appropriate soil temperatures that support biological activity, NH ions are converted to the nitrate (NO;) form by the action of specific soil bacteria in a process known as nitrification. Nitrification generally occurs at soil temperatures above 50 °F, and increases as temperatures rise above this level. However, some limited activity occurs below 50 °F as well. Ammonium is converted first to nitrite (NO,) by the action of Nitrosomonas bacteria, and then to nitrate by Nitrobacter and Nitrosolobus bacteria: NH NO obacteria NONO Urea Urea is a solid fertilizer with high N content (46%) that can be easily applied to many types of crops and turf. Its ease of handling, storage and transport, convenience of application by many types of equipment, and ability to blend with other solid fertilizers has made it the most widely used source of N fertilizer in the world. Production Urea is manufactured by reacting CO, with NH, in the following two step reactions: 2NH, + CO, → NH,COONH, (ammonium carbamate) NH,COONH, (NH), CO+ H,O (urea+water) The urea molecule has 2 amide (NH) groups joined by a carbonyl (C=O) functional group. UNIT 3 159 CHEMISTRY GRADE 12 Urea Molecule Urea readily dissolves in water, including soil moisture. Thus, it can be "incorporated" into the soil by sufficient rainfall or irrigation. Soil Reactions - If urea is applied to the soil surface and not incorporated by water or tillage, it is subject to volatilization losses of nitrogen. This occurs as urea undergoes hydrolysis to carbon dioxide and ammonia: (NH,), CO + H,O → CO, + 2NH, Urea-ammonium nitrate (UAN) Solutions Urea-ammonium nitrate (UAN) solutions are also popular nitrogen fertilizers. These solutions are made by dissolving urea and ammonium nitrate (NH NO) in water. Urea-ammonium nitrate (UAN) solutions are mixtures of urea, ammonium nitrate, and water in various proportions i e. 35%, 45% and 20% respectively. All common UAN solutions are formulated to contain 50% of actual N as amide, (from urea), 25% as ammonium (from ammonium nitrate), and 25% as nitrate (from ammonium nitrate). Production Liquid urea-ammonium nitrate (UAN) fertilizer is relatively simple to produce. A heated solution containing dissolved urea is mixed with a heated solution of from the urea solution and half from the ammonium nitrate solution. ammonium nitrate to make a clear liquid fertilizer. Half of the total nitrogen comes Soil Reactions - The urea portion of UAN solutions reacts just as dry urea does (see the reaction of urea). If applied on the surface, the amide-N in the solution may incur losses due to volatilization when urease hydrolysis releases NH,. But if UAN is incorporated by tillage or sufficient water, the NH,, quickly reacts with soil water 160 UNIT 3 168 Manufacturing of Valuable Products/ Chemicals to form NH*. This ammonium, as well as the ammonium nitrogen derived from ammonium nitrate in the solution, adheres to soil components at the application site and is not subject to loss in the short term. Like N applied as anhydrous ammonia,to form NH*. This ammonium, as well as the ammonium nitrogen derived from ammonium nitrate in the solution, adheres to soil components at the application site and is not subject to loss in the short term. Like N applied as anhydrous ammonia, this nitrogen will eventually be taken up by plants in the ammonium form, or if not, eventually converted to nitrate by soil bacteria. Diammonium Monohydrogen Phosphate(DAP), (NH) HPO Diammonium monohydrogen phosphate (DAP) is a white crystalline compound. Production Diammonium monohydrogen phosphate (DAP) is formed by the reaction between ammonia and phosphoric acid by the following two steps: Step 1: Anhydrous ammonia reacts with phosphoric acid to form monoammonium dihydrogen phosphate and diammonium monohydrogen phosphate 3NH, (g)+2H,PO, (1) NH,H,PO, (s)+ (NH,), HPO, (s) Step 2: Recycling monoammoniumdihydrogen phosphate for further reaction with anhydrous ammonia yields DAP: NH,H,PO, (s)+ NH, (g) → (NH,),HPO, (s) DAP is used as a fertilizer. It temporarily increases soil acidity, but over the long term, the soil becomes more acidic than before upon nitrification of the ammonium. DAP has the advantage of having both nitrogen and phosphorus, which are essential for plant growth. DAP can be used as fire retardant. It lowers the combustion temperature of the material, decreases weight-loss rates, and causes an increase in the production of residue or char. DAP is also used as a yeast nutrient in wine making and beer brewing. UNIT 3 161 CHEMISTRY GRADE | Sulphuric Acid 170 Activity 3.7 Exercise 3.5 Write the chemical reaction that shows the synthesis of urea? 2. Write the reaction which shows soil reactions of urea? 3. Describe the industrial production of DAP. Write the chemical equations too 4. Describe the properties and major uses of DAP. 5. Calculate the percentage composition of phosphorus and nitrogen in DAP. 3.3.4 Which chemical do you think is produced in the largest volume in the world? And why? Properties Anhydrous, 100% sulphuric acid is a colorless, odorless, heavy, oily liquid. It is heavier than water, with 98 gram/mole molar mass. Pure H,SO, melts at 10.5 °C and boils at 338 °C. It is soluble in all ratios with water. This chemical is highly corrosive. reactive and soluble in water. The sulphuric acid can be diluted by water to get acids in various strengths for different purposes. During the mixing process, sulphuric acid should be added to water, not the other way around. Since the dissolution of sulfuric acid in water is very exothermic i.e. a large amount of heat is released and the solution may even boil. It has a very high oxidizing power and thus, acts as a strong oxidizing and dehydrating agent. It can oxidize both metals as well as non-metals. Moreover, it itself reduces to sulphur dioxide.Example 2H,SO,+ C→ 2SO,+ CO,+ 2H,O 33.5 % sulphuric acid commonly called battery acid while 62.18 sulphuric acid is known as chamber acid used for production of fertlizers 162 UNIT 3 Manufacturing of Valuable Products/ Chemicals Uses Activity 3.8 Discuss in group and present your answer to your classmates.. 170/298 Open Chemistry Guide Bookin group and present your answer to your classmates. By referring different sources such as internet and reference books list the various uses of sulphuric acid. Preparation Sulphuric acid is manufactured industrially by the contact Process which involves the following four major steps: Step 1: Burning sulphur in air (preparation of sulphur dioxide): Step 2: Converting SO, to SO, (Oxidation of sulphur dioxide to prepare sulphur tri oxide) 250, (8) +0,(8)250, (8) The conversion of SO, to SO, is slow, but it is increased by heating the reaction mixture to 400 °C in the presence of VO, catalyst. Because the SO, and O molecules react on contact with the surface of V₂O, the process is called the contact process. Step 3: Passing SO, into concentrated H,SO, (addition reaction of sulphur trioxide and sulphuric acid to give oleum): SO, (g)+ H,SO, (1)→ H,S,O, (1) Sulphur trioxide is absorbed into 98 % sulphuric acid to form oleum which is also known as fuming sulphuric acid. Step 4: Addition of water to oleum i.e. Dilution of oleum to produce concentrated sulphuric acid H,S,O, (1) + H,O(1) 2H,SO,(1) Oleum is diluted with water to form concentrated sulphuric acid, as indicated in the above reaction. The production of sulfuric acid with the contact process is summarized in Figure 3.10. UNIT 3 163 CHEMISTRY GRADE 12 Concentrated sulphuric Acid sulphur HS,0, (Oleum) Pipe Dry Air Catalyst Converter Water Contacting VO, catalyst HSO, 172 at 450-550 °C Second Step Third Step First Step Figure 3.10: Production of sulphuric acid (contact process) Exercise 3.6 Describe the industrial production of H,SO. Write the equations and state the conditions of each step. State the properties and major uses of sulphuric acid. 3. Draw a schematic diagram that involves the four major steps in the production of sulphuric acid along with chemical reactions. 4. When an active metal reacts with concentrated sulfuric acid, the active metal gets oxidized while the sulphuric acid gets reduced to HS, S and SO. Predict the product formed and write the reaction equation "when eight mole of aluminium react with 15 moles of concentrated sulphuric acid" Project 3.1 Write a paper, not less than three pages, comparing and contrasting natural fertilizers, that are processed locally, like manures and compost, with commercial fertilizer. Tip- include their impacts, sustainability, accessibility, and composition in your discussion. Submit a report to your teacher. 164 UNIT 3 Manufacturing of Valuable Products/ Chemicals 172/298 3.3.5 Some Common Pesticides and Herbicides3.3.5 Some T Activity 3.9 Make a group of five students and list up to five names and specific uses of natural and commercial pesticides and herbicides that Ethiopian farmers use to treat insect, pests and weeds. Share your discussions with the rest of the class. Pesticides Pesticides are chemicals used to prevent or control pests, diseases, weeds and other plant pathogens. It decreases yield losses, and maintain high product quality. Chemical pesticides can be classified according to their chemical composition. This method allows the uniform and scientific grouping of pesticides to establish a correlation between structure, activity, toxicity and degradation mechanisms, among other characteristics. Table 3.1, shows the most important pesticides and their general characteristics, and Figure 3.11 show examples of some chemical structures of pesticides. Table 3.1: General characteristics of some pesticides Pesticides Organochlorines Characteristics Soluble in lipids They accumulate in the fatty tissue of animals and transferred through the food chain toxic to a variety of animals long-term persistence Main composition Composed of Carbon, Hydrogen, Chlorine, anda Oxygen atoms. They are nonpolar and lipophilic UNIT 3 165 CHEMISTRY GRADE Characteristics Pesticides Organophosphates Main composition atom in the molecule. In organophosphate pesticides. 174 Carbamates Pyrethroids Chemical structure based on a plant alkaloid Physostigma venenosum Compounds similar to the synthetic pyrethrins (alka loids obtained from petals Biological Soluble in organic solvents but Possess central phosphorus also in water They infiltrate reaching relation whit organ chlo groundwater, less persistent rines, these compounds are than chlorinated hydrocarbons more stable and less toxic some affect the central nervous in the environment. The system They are absorbed by plants can be aliphatic, cyclic and and then transferred to leaves heterocyclic. and stems which are the supply of leaf-eating insects or feed on wise. kill a limited spectrum of insects highly toxic to vertebrates Relatively low persistence Carbamate acid derivatives other pesticides Affect the nervous system but less than compared to the the safest in terms of their use of Chysanthemun ciner some are used as household ariefolium insecticides Only the Bacillus thuringiensis Viruses, microorganisms or (Bt) and its subspecies are used their metabolic product with some frequency are applied against forest pests and crops Particularly against butterflies and also affect other caterpillars 166 UNIT 3 Manufacturing of Valuable Products/ Chemicalshexalydro-6,9-methmuo-2.4.3-benzadiasathiepin 3 axde) Permethrin (3-phanoybenzyl (2RS)-cis trang 3-(2,2 tiyleyclopropanecarbaxylate) CH N-methylcarbamate) Malathion (Diethy 2 DE Carboturan (2.2-Demethy-2,2-dihy drobenzof sra-7 Figure 3.11: Examples of chemicals structure of pesticides (A) Organochloride (B) Pyrethroid (C) Carbamate (D) Organophosphate On the other hand, there are also traditionally produced pesticides by Ethiopian farmers. Traditionally, farmers of different districts produce pesticides from botanical origins and then apply it to fruits, vegetables and other crops. These pesticides are called botanical pesticides. Botanical pesticides are extracted from various plant parts (stems, seeds, roots, leaves and flower heads) of different plant species. Botanical pesticides are hailed for having a broad spectrum of activity, being easy to process. and use, having a short residual activity and for not accumulating in the environment or in fatty tissues of warm-blooded animals. The following some of the common natural pesticides commonly used in some areas of Ethiopia: Neem Leaf, Salt Spray and Onion and Garlic Spray. Let us see detail of Neem Leaf which is one of traditionally produced pesticides. UNIT 3 167 CHEMISTRY GRADE I Neem Leaf Neem has long been used for its medicinal and culinary properties. It is also known to be used as a deterrent to pests. This medicinal herb has a bitter taste and strong odour that may keep the bugs away from your plants, but non-toxic to animals, birds, plants and humans. It's best to spray Neem oil on young plants where it is said to be effective for about 22 days. Add some Neem oil to a dash of liquid soap and some warm water and stir slowly. Add it to a spray bottle and use it immediately. This serves as an insect/pest 3.12 shows a Neem leaf that is grown in most gardens. repellant. Even you can cut down and collect the Neem leaf around your environment and put it simply in your home/table as it serves also as pests/insect repellant. Figure Figure 3.12: Neem Leaf (Azadirachta indica) Project 3.2 Please collect information from your parents or concerned body and write a report about one of the common traditionally produced pesticides by Ethiopian farmers other than Neem Leaf. And submit the report to your teacher... 168 UNIT 3 Manufacturing of Valuable Products/ Chemicals 176/298 Herbicides (chemical weed killers) Herbicides also commonly known as weed killers which are substances used to control unwanted plants. Selective herbicides control specific weed species, while leaving theHerbicides (chemical weed killers) Herbicides also commonly known as weed killers which are substances used to control unwanted plants. Selective herbicides control specific weed species, while leaving the desired crop relatively unharmed. Non-selective herbicides (sometimes called total weed killers in commercial products) since they kill all plant material with which they come into contact. Herbicides have largely replaced mechanical methods of weed control in countries where intensive and highly mechanized agriculture is practiced. Types of Herbicides The most important groups of herbicides and the crosponding examples are given in Table 3.2. Table 3.2 Common groups of herbicides S.No Types of herbicide group Chlorophenoxy acids Examples of Herbicides 2,4-D and 2,4,5-T Atrazine, hexazinone, and simazine Amides 2 Triazines Organic phosphorus chemicals Glyphosate Thiocarbamates 6 Dinitroanilines 7 Chloroaliphatics 8 Inorganic chemicals Alachlor and metolachlor Butylate Trifuralin Dalapon and trichloroacetate Various arsenicals, cyanates, and chlorates Exercise 3.7 What are insecticides? 2. List and describe the types of pesticides. 3. List the most common groups of herbicides. UNIT 3 169 3.3.6 CHEMISTRY GRADE 12 Sodium Carbonate Activity 3.10 Discuss in groups the following questions and present your opinion to the class? What are the raw materials for glass production? How is glass manfuctured? 2. Why does Solvay plant situated near water mass? Properties Sodium carbonate (washing soda) is a white crystalline solid powder. It exists as a decahydrate (Na,CO,.10H,O) compound. It has a density of 2.54 g/cm3, a purity of t has a high melting point 851°C and a high boiling point 1,600 °C. It has hygroscopic properties in nature. There are two forms of sodium carbonate available. light soda and dense soda. Light soda and Dense soda are both chemically identical compounds, with the only difference being their densities and size. Light soda has a lower density of 0.7 g/ml, while dense soda has about 0.9 g/ml. Sodium carbonate can be easily dissolved in water to form an aqueous solution with moderate alkalinity and dissolved in acids by liberating CO,. But it is insoluble in alcohol. Anhydrous Sodium Carbonate is unaffected by heat. It melts without disintegrating. The release of OH (aq) ions during hydrolysis makes Sodium Carbonate aqueous solutions somewhat alkaline. Na,CO, (s) + 2H,0 (1) → H,CO, (aq) + 2Na* (aq) + 20H-(aq) 5 aqueous solution has the property of absorbing carbon dioxide from the air, and produces sodium Hydrogen Carbonate. Na,CO, (ag) + H₂O + CO, (8) 2NaHCO, (aq) 178 170 UNIT 3 Manufacturing of Valuable Products/ ChemicalsUses Sodium carbonate has wide applications in various kinds of fields around the world. One of the most important application of sodium carbonate is for the manufacturing of glass. Based on statistics information, about half of the total production of sodium carbonate is used for the manufacturing of glass. During the production of glass, sodium carbonate acts as a flux in the melting of silica. It is also largely used in production of detergents and soaps. In addition, as a strong chemical base, it is used in the manufacturing of pulp and paper, textiles, drinking water. addition, it can also be used for tissue digestion, dissolving amphoteric metals and compounds, food preparation as well as acting as a cleaning agent. It is also used in the brick industry. Production Method (Solvay process)a Sodium carbonate at present is mostly mined from its natural deposits. It also is manufactured synthetically by Solvay (or ammonia-soda) process. The natural production of sodium carbonate currently has surpassed its synthetic production. The Solvay process involves a series of partial reactions. The first step is calcination of calcium carbonate to form lime and CO,. Lime is converted to calcium hydroxide. The most crucial step of the process involves reacting brine solution with carbon dioxide and ammonia to produce sodium bicarbonate and ammonium chloride. Sodium bicarbonate converts to sodium carbonate. The calcium hydroxide and ammonium chloride react to form calcium chloride as the by-product. The partial reactions are shown below: CaCO, → CaO + CO₂ CaO + H₂O Ca(OH), 2NaCl + 2CO,+ 2NH, + 2H,O 2NaHCO,+ 2NH,Cl 2NaHCO, →Na,CO, + H,O + CO, Ca (OH), + 2NH,CI CaCl, + 2NH, + 2H,O The overall reaction: CaCO,+ 2NaCl Na,CO, + CaCl, UNIT 3 171 CHEMISTRY GRADE 12 180 180/298 Exercise 3.8 List the four major raw materials that are used to manufacture Na,CO, in the Solvay process. 2. What is the main byproduct in manufacturing of Na,CO, in the Solvay Process? 3. Write the chemical equation of the reaction when sodium hydrogen carbonate is heated in the Solvay process. 4. What is the purpose of burning coke in the Solvay process? 5. Write the chemical formula of the following compounds: a) Washing soda b) soda ash c) baking soda 3.3.7 Sodium Hydroxide (NaOH) Activity 3.11 Discuss in groups and present your opinion to the class. During the manufacturing process of NaOH from brine, Cl, is produced in the process. What are the uses of this Cl,? 2. Why do you take care while doing experiments that involves sodium hydroxide? Properties Sodium hydroxide (NaOH) is a white, translucent crystalline solid with a melting point f591 k. It is a stable compound. NaOH is often referred to as caustic soda, due to its corrosive action on many substances: it decomposes proteins at room temperatures and may cause chemical burns to human bodies. It dissolves readily in water moderately soluble in alcohol; its solution has bitter and has a soapy feeling". It is strongly alkaline in nature commonly used as a Base. Manufacturing process NaOH does not occur in nature. It has been manufactured at large scale for many years from readily obtainable raw materials. It is manufactured from sodium chloride (NaCl) and water (H,O) in electrolysis process. Its preparation involves various methods like; 172 UNIT 3 Manufacturing of Valuable Products/ Chemicals 1. Castner-Kellner process1. Castner-Kellner process 2. Nelson Diaphragm cella 3. Loewig's process Castner-Kellner process Principle: In the Castner-Kellner method, electrolysis of brine solution is performed in order to obtain sodium hydroxide.. Castner-Kellner cell: It is a steel tank that is rectangular. Ebonite is lined inside the tank. Titanium acts as an anode and a layer of mercury at the bottom of the tank acts as the cathode. Ionization of brine solution occurs according to the following reaction: 2NaCl 2Na*+ 2CI When the brine solution comes in contact with electric current, ionization takes place. As a result positive and the negative ions move towards the electrodes. Sodium ions get deposited at the mercury cathode forming a sodium amalgam. Chlorine ions move towards the anode and exit the cell from the top. Reaction at the anode: 2C1 Cl+ 2e Reaction at the cathode: 2Na + 2e→2Na NaOH The amalgam formed is then transferred to another chamber called denuder. In the denuder, it is treated with water to obtain a sodium hydroxide solution. On evaporation of the solution, solid sodium hydroxide is formed. This is a very efficient process in order to obtain pure caustic soda. Mercury is toxic so care must be taken to prevent mercury losses. Safety Due to its strong corrosive qualities, exposure to sodium hydroxide in its solid or solution form can cause skin and eye irritation Pure NaOH has a high affinity for water and may form hydrates depending on the concentration. Since some hydrates have melting points greater than 0 °C, insulation or heating during storage. UNIT 3 173 CHEMISTRY GRADE Uses It is widely used in numerous industrial processes such as in pulp and paper manufacturing, alumina extraction from bauxite in aluminum production, as well as in the textiles industry and drinking water production. NaOH is also an important compound in the manufacture of soaps and detergents (i.e. a cleansing agent and in the manufacturing of washing soda), in waste gases scrubbing, saponification and etherification and esterification reactions; as well as in basic catalysis. Exercise 3.9 1. List the uses of NaOH in industrial processes or manufacturing of other valuable products What is the role of caustic soda in the industrial cleaning process? What are the health effects of caustic soda? 3.4 Some Manufacturing Industries in Ethiopia At the end of this section, you will be able to list some manufacturing industries in Ethiopia outline the important steps in the production of ceramics mention some uses of ceramics Write the important steps in the production of cement, ceramics, glass, sugar and ethanol predict the product of sugar fermentation prepare ethanol from locally available ingredients compare and contrast the indigenous and industrial methods of: food preservation and packing, making ethanol, and processing skin and hide. compare and contrast locally made clay materials with ceramics outline important steps in the production of pulp and paper, soaps and detergent and dry detergents explain how tanning is carried out mention some uses of skin and hides present a report to the class after visiting a nearby food factory. 174 UNIT 3 Some Manufacturing Industries in Ethiopia Activity 3.12 182/298 Discuss in groups and present your opinion to the class.Activity 3.12 Discuss in groups and present your opinion to the class. 1. Do you know where in Ethiopia most of chemicals /manufacturing industries are located? 2. List as many of the manufacturing chemical industries in Ethiopia, and write the products manufactured by them in tabular form? The chemical industry in Ethiopia is still at a nascent stage. Therefore, there is a strong demand to develop the chemical industry to meet the requirements of the rapidly growing Ethiopian economy. Currently, imports fulfil domestic demand chemicals/manufacturing products. According to ADDISBIZ.com news of the year 2022, more than 2228 manufacturing industries are available in the country. In this subsection emphasis is given to the production of final products like glass. cement, ceramics, sugar, alcoholic beverages, food packing and preservation, soaps and dry detergent, tanning and paper. 3.4.1 Glass Manufacturing Activity 3.13 Discuss the following questions in groups and present your answer to the class. 1. What is glass? 2. List the types of glasses with their corresponding main functions. Is glass manufactured in Ethiopia? Glass is an amorphous or non-crystalline solid material. It is inexpensive to make, easy to shape when it's molten, reasonably resistant to heat when it's set, chemically inert (glass jar doesn't react with the things inside it). It can be recycled any number of time. The main component of glass is silica. UNIT 3 175 CHEMISTRY GRADE 12 Quartz glass is made by melting pure silica, SiO,, at a temperature of about 2300°C and pouring the molten viscous liquid into moulds. It is of high strength, low thermal expansion and highly transparent. Soda-lime glass is ordinary glass. It is a mixture of sodium silicate and calcium a silicate. It is made by heating a mixture of silica sand, sodium carbonate or sodium sulphate and limestone. The reactions that take place in forming soda-lime glass are the following: Na,CO, +SiO, Na,SiO, +CO, CaCO, +SiO,→CaSiO, +CO, Soda-lime glass accounts for about 90% of manufactured glass. This type of glass is widely used for window panes, bottles, dishes etc. Borosilicate glass is commonly known as Pyrex. It is manufactured using boron (III) oxide, B,O, instead of limestone or calcium oxide. This glass has high resistance to chemical corrosion and temperature changes and is widely used to make ovenware and laboratory equipment such as flasks, beakers, and test tubes. Project 3.3 Have you ever wondered how glass retains different colors? Consult books in your library and make list of the compounds added to impart color to the glass. Submit your findings to your teacher? 176 UNIT 3 Some Manufacturing Industries in Ethiopia Batch preparation: refers to the preparation of the raw materials according to the appropriate combinations. The raw materials are mixed in a proportion of 60% Steps in glass production sand, 21% sodium carbonate and 19% limestone. ii) Glass melting: The raw materials and recycled glass (according to their colour) are fed into a glass-melting furnace. The materials are then heated toSteps in glass production i) ii iv) vi) Some Manufacturing Industries in Ethiopia Batch preparation: refers to the preparation of the raw materials according to the appropriate combinations. The raw materials are mixed in a proportion of 60% sand, 21% sodium carbonate and 19% limestone. Glass melting: The raw materials and recycled glass (according to their colour) are fed into a glass-melting furnace. The materials are then heated to a temperature of about 1600°C to form a molten viscous liquid. Why glasses are separated according to the colour? The furnace operates continuously, producing glass 24 hours a day. Substances that give the glass different colours or improved chemical and physical properties such as transparency, thermal and chemical stability and mechanical strength are added during this process. Glass forming: This is the stage in which the melted glass is made into a required shape.. Annealing: This is a process that involves the removal of internal stresses by reheating the glass followed by a controlled slow-cooling cycle during which the stresses are relieved. Inspection: It involves testing of the glass product to check whether it fulfills desired quality requirements or not. Packing and dispatching is the final stage before distribution Exercise 3.10 Predict the type of glass produced if potassium carbonate is used instead of sodium carbonate? What would be its properties? What type of color will impact by the iron compounds which is often contained as impurities in the sand used in manufacturing of ordinary glass? 3. To produce glass industrially, two types of furnaces are used, what are the two types of furnaces, and what type of glass is produced in each type? UNIT 3 177 CHEMISTRY GRADE 12 3.4.2 Manufacturing of Ceramics Activity 3.14 Form a group of three to discuss the questions below and share your reflection's to the class 1. Discuss the traditional pottery industry in Ethiopia and present your answer to the class? 2. List the similarities and differences between pottery and Ceramics. Prepare a list of ceramics products used in daily life. Ceramic is an inorganic, non-metallic solid prepared by the action of heat and subsequent cooling. Traditional ceramics, such as porcelain, tiles, and pottery are formed from minerals such as clay, talc and feldspar. Most industrial ceramics, however, are formed from extremely pure powders of specialty chemicals, such as silicon carbide, alumina. barium titanate, and titanium carbide. The minerals used to make ceramics are dug out of the earth and are then crushed and ground into a fine powder. Manufacturers often purify this powder by mixing it in a solution and allowing a chemical precipitate (a uniform solid that forms within a solution) to form. The precipitate is then separated from the solution. The powder is heated to drive off impurities including water. The steps of manufacturing ceramics include: A. Moulding: After purification, small amounts of wax are often added to bind the ceramic powder and make it more workable. Plastics may also be added to the powder to give the desired pliability and softness. The powder can be shaped B. into different objects by various moulding processes. Densification: The process of densification uses intense heat to condense a ceramic object into a strong, dense product. After being moulded, the ceramic object is heated in an electric furnace to temperatures between 1000 °C and 1700 °C. As the ceramic heats, the powder particles coalesce, much as water droplets join at room temperature. As the ceramic particles merge, the object becomes increasingly dense, shrinking by up to 20 percent of its original size. 178 UNIT 3 186 Some Manufacturing Industries in Ethiopia The goal of this heating process is to maximize the strength of ceramic by obtaining an internal structure that is compact and extremely dense. In general, most ceramics are hard and wear-resistant, brittle, refractory, thermal and electrical insulators, non-magnetic, oxidation-resistant, and chemically stable. Due to the wide range of properties of ceramic materials, are used for a multitude of applications. Well-known uses of ceramics: - they are commonly found in art sculptures, dishes, platters, and other kitchenware, kitchen tiles and bath room structures. Lesser-known uses for ceramics: they are used as electrical insulators. computer parts, tools, dental replacements, engine parts, and tiles on space shuttles and to replace bones such as the bones in hips, knees, and shoulders. Future uses of ceramics: - In the future, ceramics might be used to remove impurities from the drinking water and to replace diseased heart valves
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