KPK Class 10 Chemistry Notes Chapter #16 | (Chemical Industries)
Short Questions and long questions (Chemical Industries) KPK Class 10 Chemistry Notes Chapter #16. We have uploaded complete and comprehensive notes of Chapter #16 for all kpk boards.
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short questions Class 10 Chemistry Notes Chapter #16
Q.1) How do you convert NaHCO3 into Na2CO3?
Answer: By Calcinations: Dry sodium bicarbonate is heated in rotatory furnace called calciner, to give anhydrous sodium carbonate or soda ash. 2NaHCO3 →Na2CO3 + CO2 + H2O Carbon dioxide released in this step is re-circulated in carbonating tower.
Q.2) Enlist the different uses of urea?
Answer: Uses of Urea: It is a white crystalline organic compound. It is important due to the following usage: 1. About 86% of urea manufactured is used as solid fertilizer. 2. Urea-formaldehyde resins have large use as a plywood adhesive/glues. 3. Melamine-formaldehyde resins have largely used as dinnerware and for making extra hard surfaces. 4. Urea can be used to make urea nitrate, which is highly explosive. 5. Urea is used as raw material for manufacture of many important chemical compounds like plastic, resins, various adhesives. 6. Urea is a used as flameproofing agent.
Q.3) Differentiate between mineral and ore?
The majority of metals are usually found in combined form having definite chemical composition. The naturally occurring metallic compounds are called minerals.
An aggregate of mineral and other impurities is known as ore. A naturally occurring solid material from which a metal or valuable mineral can be extracted profitably is called an ore.
All minerals are not ores
All ores are essential minerals too.
Example: Clay is the example of Aluminium
Example: Bauxite and cryolite are the main ores of aluminium
Q.4) Define metallurgy? What are its steps?
Answer: Metallurgy: The science that deals with the procedures used in extracting metals from their ores, purifying alloying metals and creating useful objects from metals are called metallurgy. Steps involved in metallurgy: (i) Concentration of the ore a) Gravity separation b) Froth flotation process c) Electromagnetic separation (ii) Extraction of the metal a) Roasting b) Smelting: c) Bassemerization (iii) Refining of the metal
Q.5) What is the function of forth floatation process?
Answer: Froth Floatation Process: This method is based on the wetting of the ore and gangue with pine oil and water. This method is especially used for sulphide ores. In this method a mixture of water, pine oil and detergents are used which are made to agitate with the ore. A blst of compressed air is blown through the pipe of a rotating agitator to produce forth. The sulphide ore particles are wetted and coated by pine oil and rise up along with the forthat the top of mixture in container from which it is collected. The gangue particles wetted by water sink to the bottom of the tank. The froth containing the sulphide ore is tranferred to another container, washed and dried. Thus sulphide ore is separated from the gangue.
Q.6) On what basis the different fractions of petroleum are separated?
Answer: The different fraction of petroleum are separated on the basis of boiling points. Compounds with the highest boiling points condense first near the bottom, while those compounds having low boiling points move to the top of the fractionating column. The vapours condense gradually at different levels according to their boiling points.
Q.7) What is slaked lime? How slaked lime is produced?
Answer: Slaked Lime: Calcium hydroxide is an inorganic compound with the chemical formula Ca(OH)2. It is a colorless crystal or white powder and is obtained when quicklime is mixed or slaked with water. Preparation of Slaked lime: Carbon dioxide is produced by heating limestone in limekiln. CaCO3 → CaO + CO2 Carbon dioxide is fed into the carbonating tower form the top. Calculated amounts of quick lime and water are mixed to produce slaked lime. CaO +H2O → Ca(OH)2
Q.8) Assess the composition of urea and calculate the percentage of nitrogen in it.
Answer: Composition of Urea:
Element and their symbol
Percentage of nitrogen in urea: Urea = NH2-CO-NH2 Total mass=60 Mass of nitrogen = 14, 2 molecules hence m=28 N%= mass of nitrogen/Mass of urea X 100 = 28/60 X 100 N%= 46.6%
Q.9) What is gangue and where it is formed?
Answer: Gangue: The earthy materials such as sand, rock, clay and other impurities attached with the ores are called gangue. Formed on Earth’s crust where ores are concentrated.
Q.10) How blister copper is purified?
Answer: The impure blister copper is purified by the electrolytic process. The process of electro-refining of copper involves the following steps: 1. A large plate of impure blister copper is made as the anode 2. A thin rod or sheet of pure copper is made as the cathode. 3. The electrolyte is copper sulphate and dil. sulphuric acid solution is used. 4. The potential difference is 1.3 volt in this process. 5. During electrolysis pure copper is deposited on the cathode plates 6. The impurities (Ag, Au, and Pt mud along with Cu2O) in the anode settle down at the bottom and are removed as anode mud. 7. The copper obtained by this method is 99.9% pure. Anode reaction: Cu → Cu+2 + 2e– Cathode reaction: Cu+2 + 2e– ← Cu
Q.1 a) How could you convert the concentrated ore to its oxide?
Answer: Convert concentrated ore to oxide: It is easier to obtain metal from its oxide form as compared to its sulphide, carbonate or any other form. Therefore, prior to reduction usually, the metal is converted to its oxide form. Following methods are used to convert the concentrated ore to its oxide form. 1. Roasting: The process in which the concentrated ore is heated either alone or with some other materials in excess of air in a furnace. The concentrated ore is then roasted in a furnace between 500oC and 700oC in the presence of a current of air. Ores of metals such as copper and nickel, when roasted in air, are converted to their oxides and sulphur is oxidized to SO2. While ores of some metals like lead are partially oxidized and converted into sulphate. The following reaction takes place. CuCO3→CuO + CO2 Cu(OH)2 →CuO + H2O 2CuFeS2 + O2→Cu2S + 2FeS + SO2 2. Smelting: It is a general term used for various operations, whereby the metal is separated by fusion from its ore. It is the process in which the oxide ore in the fused state is reduced with reducing agents such as coke to get the metal is called smelting. The roasted ore is mixed with coke and sand and smelted into a blast furnace. During smelting, it gets oxidized to iron oxide. The iron oxide then reacts with silica forming iron silicate. 2FeS + 3O2 →2FeO +2SO2 FeO + SiO → FeSiO3 Iron silicate is slag. It is lighter than molten sulphides of copper and iron hence it is removed at the upper hole. The cuprous sulphide in the blast furnace also oxidizes and form copper oxide. 2Cu2S + 3O2 → 2Cu2O + 2SO2 The copper oxide then reacts with un-reacted iron sulphide and form cuprous sulphide and iron oxide. Cu2O + FeS →Cu2S + FeO This FeO also reacts with silica forming, iron silicate slag. Molten cuprous sulphide with iron sulphide is called matte and is removed through the slag hole. 3. Bessemerization: Bessemer process was invented by Henry Bessemer. The process is carried out in a special kind of egg-shaped or pear-shaped furnace. This furnace is a Bessemer converter. In mesmerization, the molten matte is poured in Bessemer converter and calculated amount of sand is added. Iron sulphide oxidized to form iron oxide. This iron oxide reacts with sand forming FeSiO3 which floats on the top. 2FeS + 3O2 → 2FeS +2SO2 FeO + SiO2 →FeSiO3 On the other cuprous sulphide converted to cuprous oxide. The cuprous oxide reacts with cuprous sulphide to produce copper in molten form and sulphideoxide. 2Cu2S +3O2→ 2Cu2O + 2SO2 2Cu2O +Cu2S → 6Cu + SO2 The copper produced in this way is known as blister copper because it has a porous surface which is due to the escape of sulphur dioxide gas during solidification. It is 95 to 97% pure copper, besides, this it contains iron, manganese, silver, gold et.
Q.1 b) How would you use the roasting in extraction of copper?
Answer: Roasting is the process in which the concentrated ore is heated either alone or with some other materials in excess of air in a furnace. Ores of metals such as copper when roasted in air are converted to their oxides. The following reaction takes place. CuCO3→CuO + CO2 Cu(OH)2 →CuO + H2O 2CuFeS2 + O2→Cu2S + 2FeS + SO2
Q.1 c) What inference can you make of smelting in extraction of copper?
Answer: In the process of smelting the cuprous sulphide in the blast furnace oxidizes and form copper oxide. 2Cu2S + 3O2 → 2Cu2O + 2SO2 The copper oxide then reacts with un-reacted iron sulphide and form cuprous sulphide and iron oxide. Cu2O + FeS →Cu2S + FeO This FeO also reacts with silica forming, iron silicate slag. Molten cuprous sulphide with iron sulphide is called matte and is removed through the slag hole.
Q.1 d) Can you elaborate the reason of electro-refining of copper?
Answer: Electro-refining of metals is a process of obtaining pure metal form the impure one by the process of electrolysis. So by the process of electro-refining impure blister copper is refined.
Q.2 a) List the raw materials used in Solvay’s process?
Answer: Raw materials The raw materials used in the Solvay process are: 1. Ammonia gas (NH3) 2. Sodium chloride (NaCl) or brine 3. Limestone (CaCO3) 4. Water (H2O)
Q.2 b) What basic reactions would you use to support the manufacture of soda ash?
Answer: Basic Reaction: Following reaction are involved in the manufacture of Soda Ash. i. Preparation of Brine solution: At first step a saturated solution of sodium chloride is prepared which is also known as brine. ii. Preapration of ammonical Brine: In this step brine solution is allowed to flow down in ammoniating tower. Ammonia is dissolved in brine. iii. Preparation of Carbon dioxide and slaked lime: Carbon dioxide is produced by heating limestone in limekiln. CaCO3 → CaO + CO2 Calculated amout of water and quick lime are mixed to produce slaked lime Ca(OH)2. CaO + H2O → Ca(OH)2 iv. Carbonation of Ammonical Brine: In this step carbon dioxide is mixed with carbon dioxide gas. The carbon dioxide is converted into small bubbles. Carbon dioxide reatcs with ammonia to form ammonium carbonate. CO2 + NH3 + H2O → NH4HCO3 Ammonium carbonate reacts with sodium chloride and form sodium bicarbonate and ammonium chloride. NH4HCO3 + NaCl (brine) → NaHCO3 + NH4Cl v. Filtration of precipitates: The precipitate of sodium bicarbonate is separated from the solution by filtration. vi. Calcinations: Sodium bicarbonate is then heated to form sodium carbonate. 2NaHCO3 + heat → Na2CO3 + H2O + CO2
Q.2 c) Predict the by products in the Solvay process?
Answer: Ammonia and calcium chloride are the by products in the solvay process.
Q.3 a) Enlist the raw materials used in the manufacture of urea.
Answer: Raw materials The raw materials for the manufacture of urea are: (i) Ammonia (NH3) (ii) Carbon dioxide (CO2) Ammonia is prepared by the Haber process. The Haber process combines 1 volume of nitrogen from the air with 3 volumes of hydrogen derived mainly from natural gas (methane) into ammonia using iron catalyst at 450oC and 200 atm pressure. The reaction is reversible and the production of ammonia is exothermic. N2 + 3H2 ⇔ 2NH3
Q.3 b) What basic reactions would you use to support the manufacture of urea?
Answer: Basic Reactions: Following reaction are involved in the manufacture of urea Reaction of ammonia and carbon dioxide NH3 and CO2 are heated at 170 – 200oC and 100 – 200 atm pressure. Firstly ammonium carbamate is formed. 2NH3 + CO2 → NH2COONH4 Urea formation Ammonium carbamate is subsequently dehydrated by the application of heat to form urea and water. NH2COONH4 → NH2CONH2 + H2O
Q.3 c) What is the advantage of recycling of unreacted compound in the manufacture of urea?
Answer: Avantage of recycling of unreacted compound: Unreacted NH3 and CO2 are recycled and then used for the manufacture of urea so we do not need to introduce the reactants form the external sources again and again. So the recycling of unreacted compounds is economically favorable.
Q.4 a) Define refining of petroleum. Describe the composition of petroleum?
Answer: Refining of Petroleum: The conversion of crude oil into useful products with different boiling range and free from impurities is called refining. Composition of petroleum Petroleum or crude oil is a complex mixture of hydrocarbons and other chemicals. Petroleum in solid state is called asphalt; in liquid state, crude oil; and in gas state, natural gas. The composition may vary depending how and where the petroleum was formed. However, raw petroleum has characteristic properties and composition. Hydrocarbons in crude oil There are four main types of hydrocarbons present in crude oil. These hydrocarbons in petroleum are typically present in the following percentages: 1. Paraffins (15% – 60%) 2. Napthenes (30% – 60%) 3. Aromatics (3% to 30%) 4. Asphaltics making up the remainder. Elemental composition of petroleum Petroleum is a complex mixture made up predominantly of carbon and hydrogen, but it also frequently contains significant amounts of nitrogen, sulphur, oxygen and other elements. These key compounds in petroleum are present in the following percentages: 1. Carbon (93% – 97%) 2. Hydrogen (10% – 14%) 3. Nitrogen (0.1% – 2%) 4. Oxygen (01.% – 1.5%) 5. Sulphur (0.5% – 6%) 6. Few trace metals (< 0.1%)
Q.4 b) What are the two theories about the origin of petroleum?
Answer: Origin of Petroleum: Nothing definite can be said about the origin of petroleum, because man is familiar with its use from ancient time. Chinese used petroleum as fuel as early as 200 B.C. There are two theories about the origin of petroleum. 1. Inorganic or Abiotic origin: This theory was put forward by a Russian chemist Mendeleev. He proposed that steam reacted with metallic carbides at high temperature and pressure under the surface of the earth produced petroleum. This theory did not gain popularity. 2. Organic origin: According to this theory the remains of plants and animals were buried under the soil millions of year ago. These dead organic matter were converted into petroleum by the action of bacteria under the influence of temperature and pressure of the earth. These deposits trapped between the layers of nonporous rocks. The oil and gas thus formed could bot come out and collected underground. This theory gained popularity.
Q.5 a) Write a detail note on metallurgical operations.
Answer: Basic Metallurgical operations: It involves many physical and chemical processes. In these processes, metal is not only separated from their respective ores but it is also made suitable for use, because most of the metals are not suitable for use in pure form. There is no single method for the extracting of all metals from their ores. Because metals exists in various forms in combined state such as oxides, sulphides, halides, carbonates, silicates, sulphates and phosphates etc. Metals are extracted from their ores by variety of methods. For example, reactive metals like sodium, potassium, calcium and aluminium etc. are extracted by electrochemical process while low reactive metals such as iron, copper, zinc and lead etc. are extracted by entirely chemical methods. The selection of the process for extraction is mainly depended upon the following factors. a). Type of the ores i.e. oxide, sulphide, carbonate or halide etc b). Reactivity of the metal contained in the ores. c). Nature of the gangue present in the ores The steps involved in metallurgy for extraction of metals in the pure state from its ores are; 1. Concentration of ore: The removal of useless rocky portion of the ore is called concentration of ore. This is also called as enrichment of ore or dressing of the ore. Ore is an impure metal containing large amount of sand and rocky material. The impurities like sand, rocky materials must be removed from the ore before the extraction of metal to avoid bulk handling and in subsequent fuel costs. Many chemical and physical methods are used in concentration of ore. Physical methods includes: i. Hand picking ii. Hydraulic washing iii. Froth Floatation 2. Conversion of concentrate to oxide: It is easier to obtain a metal from its oxide form as compared to its sulphide, carbonate or any other form. Therefore prior to reduction usually the metal is converted to its oxide form. Following methods are used to convert the concentrated ore to its oxide form. i. Roasting ii. Smelting (Formation of matte) iii. Bessemerization 3. Purification of Metals: Electro-refining is a process of obtaining pure metal from the impure one by the process of electrolysis.
Q.5 b) Explain the process of smelting and bessmeraiztion with references of copper extraction.
Answer: 1. Roasting: The process in which the concentrated ore is heated either alone or with some other materials in excess of air in a furnace. The concentrated ore is then roasted in a furnace between 500oC and 700oC in the presence of a current of air. Ores of metals such as copper, when roasted in air, are converted to their oxides. The following reaction takes place. CuCO3→CuO + CO2 Cu(OH)2 →CuO + H2O 2CuFeS2 + O2→Cu2S + 2FeS + SO2 2. Smelting: It is a general term used for various operations, whereby the metal is separated by fusion from its ore. It is the process in which the oxide ore in the fused state is reduced with reducing agents such as coke to get the metal is called smelting. The cuprous sulphide in the blast furnace oxidizes and form copper oxide. 2Cu2S + 3O2 → 2Cu2O + 2SO2 The copper oxide then reacts with un-reacted iron sulphide and form cuprous sulphide and iron oxide. Cu2O + FeS →Cu2S + FeO This FeO also reacts with silica forming, iron silicate slag. Molten cuprous sulphide with iron sulphide is called matte and is removed through the slag hole.
Q.5 c) Enlist different uses of urea.
Answer: Uses of Urea: It is a white crystalline organic compound. It is important due to the following usage: i. About 86% of urea manufactured is used as solid fertilizer. ii. Urea-formaldehyde resins have large use as a plywood adhesive glues. iii. Melamine-formaldehyde resins are used as dinnerware and for making extra hard surfaces. iv. Urea can be used to make urea nitrate, which is highly explosive. v. Urea is used as raw material for the manufacture of many important chemical compounds like plastic, resins, various adhesives, etc. vi. Urea is used as flameproofing agent. vii. It is used as an ingredient in hair conditioners, facial cleansers, and lotions. viii. It is used as an alternative to rock salt in the deicing roadways and runways. It does not promote metal corrosive to the extent that salt does. ix. A flavour enhancing additive for a cigarette. x. The main ingredient in hair remover creams. xi. Urea-containing creams are used as topical dermatological products to promote rehydrations of skin.