Inorganic Chemistry Notes: Hydrides, Oxides & Metallurgy
Inorganic Chemistry Notes: Hydrides, Oxides & Metallurgy
Q1 — Diborane: Preparation, Structure & Bonding
Q1. Write a brief note on the preparation, structure, and bonding of diborane (B2H6). (6 marks)
Answer:
Diborane can be prepared by reducing boron trifluoride (BF3) with lithium aluminium hydride or by reacting sodium borohydride (NaBH4) with acids. The molecule consists of two boron atoms linked to four terminal hydrogen atoms and two bridging hydrogen atoms. The four terminal B–H bonds are normal covalent bonds, while the two bridging hydrogen atoms form three-centre two-electron bonds, giving the molecule a characteristic “banana bond” shape. This type of bonding explains the electron-deficient nature and stability of diborane.
Q2 — Silicon Carbide: Structure, Properties & Uses
Q2. Briefly describe the structure, properties, and uses of silicon carbide (SiC). (6 marks)
Answer:
Silicon carbide has a strong three-dimensional network structure in which each silicon atom is tetrahedrally bonded to carbon atoms. It is extremely hard, has a very high melting point, and shows high thermal and chemical stability. Because of these properties, silicon carbide is widely used as an abrasive material, in cutting tools, furnace linings, and as a semiconductor in high-temperature electronic devices.
Q3 — Hydrazine: Preparation, Properties & Uses
Q3. Write a short note on hydrazine (N2H4) – preparation, properties, and uses. (6 marks)
Answer:
Hydrazine is prepared by the Raschig process, in which ammonia reacts with sodium hypochlorite. It is a colourless liquid with a strong reducing nature and decomposes easily on heating. Hydrazine is used as a rocket fuel, as an oxygen remover in boilers, and as a reducing agent in chemical industries.
Q4 — Xenon Compounds: Examples XeF2, XeF4
Q4. What are xenon compounds? Describe any two briefly. (6 marks)
Answer:
Xenon forms several stable compounds with highly electronegative elements like fluorine and oxygen. Xenon difluoride (XeF2) is a linear molecule used as a fluorinating agent. Xenon tetrafluoride (XeF4) has a square-planar structure and is used in oxidation reactions. These compounds show that noble gases can participate in chemical bonding under special conditions.
Q5 — Phosphorus: Oxides and Oxyacids
Q5. Briefly describe the oxides and oxyacids of phosphorus. (6 marks)
Answer:
Phosphorus forms several oxides such as P4O6 and P4O10. P4O6 is produced by limited oxidation of white phosphorus, while P4O10 is formed under excess oxygen. Phosphorus also forms oxyacids like phosphoric acid (H3PO4), which is a tribasic acid, and phosphorous acid (H3PO3), which is dibasic. These compounds are widely used in fertilizers, water treatment, and industry.
Q6 — Steps in Metallurgical Processes
Q6. Briefly explain the steps involved in metallurgical processes. (6 marks)
Answer:
Metallurgy involves several steps. First, the ore is concentrated by removing impurities through methods like gravity separation or froth flotation. Next, the ore is roasted or calcined to remove volatile components. The concentrated ore is then reduced using heat, electricity, or chemical reducing agents to obtain the metal. Finally, the metal is purified by processes such as electrorefining, zone refining, hydrometallurgy, or solvent extraction.
Q7 — Hydrometallurgy: Principles & Applications
Q7. Write a brief note on hydrometallurgy and its applications. (6 marks)
Answer:
Hydrometallurgy is the extraction of metals using aqueous solutions. In this method, the ore is first dissolved in a suitable solvent, and the metal ions are then separated by precipitation, reduction, or solvent extraction. Hydrometallurgy is widely used for metals like gold, silver, and uranium because it allows extraction at low temperatures and gives high-purity metal.
Q8 — Roasting and Calcination Explained
Q8. Briefly explain roasting and calcination. (6 marks)
Answer:
Roasting is the process of heating sulfide ores in the presence of excess air to convert them into oxides and release sulfur dioxide gas. Calcination is the process of heating carbonates or hydrated ores in limited air to drive off moisture or carbon dioxide. Both processes help convert the ore into a form suitable for reduction.
Q9 — Electrochemical Refining: Purification
Q9. What is electrochemical refining? Briefly explain. (6 marks)
Answer:
Electrochemical refining is a method of purifying metals using electrolysis. The impure metal acts as the anode, and a pure metal sheet acts as the cathode. When an electric current is passed, pure metal ions from the anode deposit on the cathode, leaving impurities behind as anode mud. This method is commonly used for copper, silver, nickel, and gold.
Q10 — Zone Refining: Principle & Importance
Q10. Briefly describe zone refining and its importance. (6 marks)
Answer:
Zone refining is a purification method based on the principle that impurities concentrate in the liquid phase. A narrow region of a metal rod is melted and slowly moved along the rod. Impurities concentrate in the molten zone and are pushed to one end. This technique produces extremely pure metals and is essential for preparing semiconductors like silicon and germanium.
Q11 — Hydroxylamine: Preparation & Uses
Q11. Write a brief note on hydroxyamine (NH2OH): preparation, properties, and uses. (6 marks)
Answer:
Hydroxyamine is prepared by reducing nitric acid or nitrous acid using reducing agents such as hydrogen sulfide or zinc in acidic medium. It is a colourless crystalline solid that is moderately acidic and easily decomposes at higher temperatures. Hydroxyamine is used in organic synthesis, photographic developing, and as a reducing agent in chemical reactions.
Q12 — Hydrazoic Acid: Preparation & Properties
Q12. Briefly describe hydrazoic acid (HN3): preparation, properties, and uses. (6 marks)
Answer:
Hydrazoic acid can be prepared by reacting sodium azide with strong acids such as sulfuric acid. It is a colourless, volatile, and highly explosive liquid with a pungent odour. Due to its explosive nature, it is handled carefully. Hydrazoic acid is mainly used in the preparation of metal azides, which are used in detonators and explosive devices.
Q13 — Xenon Difluoride: Electronic Structure & Properties
13. Briefly explain the electronic structure and properties of xenon difluoride (XeF2). (6 marks)
Answer:
Xenon difluoride is a linear molecule in which xenon forms bonds with two fluorine atoms using available empty d-orbitals. It is a stable, colourless crystalline solid and acts as a strong fluorinating agent. XeF2 is used in synthesis of fluorinated organic compounds and as an oxidising agent in chemical reactions.
Q14 — Silicon Polymers: Linear Polysiloxanes
Q14. Write a short note on silicon polymers (linear polysiloxanes). (6 marks)
Answer:
Silicon polymers, also known as polysiloxanes, consist of repeating –Si–O–Si– units with organic groups attached to silicon atoms. They are chemically inert, thermally stable, water-repellent, and flexible. These properties make them suitable for use in lubricants, waterproof coatings, medical implants, and sealants.
Q15 — Phosphorus Pentoxide: Structure & Properties
Q15. Briefly describe the structure and properties of P4O10. (6 marks)
Answer:
Phosphorus pentoxide (P4O10) consists of a cage-like structure made up of four phosphorus atoms joined to oxygen atoms. It is a white crystalline solid with strong dehydrating properties. It reacts vigorously with water to form phosphoric acid. Because of its dehydrating nature, P4O10 is used as a drying agent and in the manufacture of phosphoric acid.
Q16 — Concentration of Ore: Types
Q16. Briefly explain concentration of ore and its types. (6 marks)
Answer:
Concentration of ore is the process of removing unwanted impurities (gangue) to increase the percentage of metal in the ore. This can be done by gravity separation for heavier ores, froth flotation for sulfide ores, magnetic separation for magnetic minerals, and leaching for soluble ores. The concentrated ore becomes suitable for further extraction.
Q17 — Solvent Extraction in Metallurgy
Q17. Write a brief note on solvent extraction in metallurgy. (6 marks)
Answer:
Solvent extraction involves dissolving the desired metal compound in an organic solvent, which separates it from impurities. The metal is then recovered by stripping or precipitation. This technique is highly selective and is used for metals like uranium, copper, and cobalt. It produces high-purity metal and is efficient even at low concentrations.
Q18 — Roasting Sulfide Ores: Example
Q18. Briefly explain roasting of sulphide ores and write one example. (6 marks)
Answer:
Roasting is the heating of sulfide ores in excess air to convert them into oxides while releasing sulfur dioxide gas. For example, zinc sulfide (ZnS) is roasted to form zinc oxide (ZnO). This process increases the ore’s reactivity and prepares it for reduction.
Q19 — Extraction of Gold: Cyanide Process
Q19. Write a short note on the extraction of gold by cyanide process. (6 marks)
Answer:
In the cyanide process, gold is dissolved in a dilute solution of sodium cyanide in the presence of oxygen to form a soluble complex. The gold is then precipitated by adding zinc powder. The precipitated gold is filtered, purified, and melted. This method is preferred because it extracts even very small amounts of gold efficiently.
Q20 — Electro-winning in Metallurgy
Q20. Briefly describe electro-winning in metallurgy. (6 marks)
Answer:
Electro-winning is the process of extracting metals from their aqueous solutions by electrolysis. The metal ions migrate to the cathode and get reduced to the solid metal. This method is used for metals such as copper, zinc, and aluminium. It produces highly pure metal and is particularly useful in hydrometallurgical extraction.
Q21 — Hydrazine Sulfate: Preparation & Properties
Q21. Briefly explain the preparation and properties of hydrazine sulphate. (6 marks)
Answer:
Hydrazine sulphate is prepared by reacting hydrazine with sulfuric acid, forming white crystalline salts. It is a stable solid that dissolves in water and behaves as a strong reducing agent. Hydrazine sulphate is used in pharmaceuticals, textile dyeing, and as a stabilized form of hydrazine for safer handling.
Q22 — Nitrous Oxide: Structure & Uses
Q22. Write a brief note on the structure and uses of nitrous oxide (N2O). (6 marks)
Answer:
Nitrous oxide has a linear structure with the sequence N–N–O. It is a colourless gas with a slightly sweet smell and supports combustion. Nitrous oxide is used as an anaesthetic in medical procedures, as a propellant in food aerosols, and as an oxidiser in rocket engines.
Q23 — Xenon Trioxide: Description & Properties
Q23. Briefly describe xenon trioxide (XeO3) and its properties. (6 marks)
Answer:
Xenon trioxide is a powerful oxidising agent formed when XeF6 reacts with water. It is a colourless solid that is highly explosive when dry. In solution, it releases oxygen and behaves as a strong acid. Due to its instability, its use is limited to laboratory studies and research on noble gas chemistry.
Q24 — Oxyacids of Nitrogen: Examples
Q24. What are oxyacids of nitrogen? Explain with examples. (6 marks)
Answer:
Nitrogen forms several oxyacids depending on its oxidation state. Nitrous acid (HNO2) is a weak acid used in diazotisation reactions. Nitric acid (HNO3) is a strong acid and powerful oxidising agent used in fertilizers and explosives. These acids show how nitrogen forms diverse compounds through bonding with oxygen.
Q25 — Phosphoric Acid: Preparation & Uses
Q25. Briefly explain the preparation and uses of phosphoric acid (H3PO4). (6 marks)
Answer:
Phosphoric acid is prepared by reacting phosphorus pentoxide with water or by treating phosphate rock with sulfuric acid. It is a tribasic acid widely used in fertilizers, detergents, food preservatives, and pharmaceutical formulations. Its non-toxic nature makes it suitable for industrial and domestic applications.
Q26 — Calcination: Definition & Example
Q26. What is calcination? Briefly explain with an example. (6 marks)
Answer:
Calcination is the process of heating ores in the absence or limited supply of air to remove moisture and volatile substances. For example, heating calcium carbonate (CaCO3) produces calcium oxide (CaO) and carbon dioxide. This process helps convert the ore into a more reactive oxide form suitable for reduction.
Q27 — Extraction of Aluminium: Hall–Héroult
Q27. Write a brief note on the extraction of aluminium by Hall–Heroult process. (6 marks)
Answer:
In the Hall–Heroult process, alumina is dissolved in molten cryolite and electrolysed at about 950°C. Carbon electrodes are used, and aluminium is deposited at the cathode while oxygen reacts with the carbon anode to form carbon dioxide. This method is efficient for producing pure aluminium on a large scale.
Q28 — Froth Flotation: Method & Importance
Q28. Briefly explain froth flotation and its importance. (6 marks)
Answer:
Froth flotation is used to concentrate sulfide ores. The powdered ore is mixed with water, collectors, and frothing agents, then air is bubbled through the mixture. Sulfide particles attach to the bubbles and rise as froth, while impurities sink. This method is essential for benefitting ores like galena and copper pyrite.
Q29 — Magnetic Separation in Metallurgy
Q29. Briefly describe magnetic separation in metallurgy. (6 marks)
Answer:
Magnetic separation uses magnets to remove magnetic ores from non-magnetic impurities. The crushed ore is passed over magnetic rollers, where magnetic minerals like magnetite are attracted and separated. It is commonly used for iron ores and saves time, energy, and processing cost.
Q30 — Thermite Process (Goldschmidt Reaction)
Q30. Write a brief note on thermite process (Goldschmidt reaction). (6 marks)
Answer:
The thermite process involves reducing metal oxides with aluminium powder, producing molten metal and aluminium oxide. For example, iron oxide reacts with aluminium to yield molten iron. This highly exothermic reaction is used in welding railway tracks, repairing machinery, and extracting metals that cannot be easily reduced by carbon.
Q31 — Borazine: Structure & Properties
Q31. Briefly explain the structure and properties of borazine. (6 marks)
Answer:
Borazine, also called inorganic benzene, has a six-membered ring consisting of alternating boron and nitrogen atoms. Its structure resembles benzene, but the B–N bonds are polar. Borazine is a colourless liquid that reacts readily with water and acids due to the electron-deficient boron atoms. It is used as a precursor for ceramic materials and in high-temperature applications.
Q32 — Silicates: Types and Structures
Q32. Write a short note on silicates and their types. (6 marks)
Answer:
Silicates are compounds containing silicon, oxygen, and various metals. They are built from SiO4 tetrahedra, which link together in different ways. Based on their arrangement, silicates are classified into orthosilicates (isolated tetrahedra), pyrosilicates (double tetrahedra), chain silicates, sheet silicates, and three-dimensional network silicates. These structures are found in minerals, ceramics, and glass.
Q33 — Boric Acid: Properties & Uses
Q33. Briefly describe boric acid and its properties. (6 marks)
Answer:
Boric acid (H3BO3) is a weak monobasic acid that appears as a white crystalline solid. It dissolves in hot water and acts as a Lewis acid by accepting hydroxyl ions. Boric acid is used as an antiseptic, fire retardant, and in glass and ceramic industries due to its mild acidity and thermal stability.
Q34 — Allotropy of Phosphorus
Q34. Explain the allotropy of phosphorus briefly. (6 marks)
Answer:
Phosphorus exists in several allotropic forms, mainly white phosphorus, red phosphorus, and black phosphorus. White phosphorus is waxy, highly reactive, and glows in the dark. Red phosphorus is more stable and used in matchboxes. Black phosphorus is the most stable form and has a layered structure similar to graphite. These allotropes differ in structure and reactivity.
Q35 — Ozone: Structure & Properties
Q35. Briefly write about the structure and properties of ozone (O3). (6 marks)
Answer:
Ozone is a triatomic molecule with a bent structure and an O–O–O bond angle of about 117°. It is a pale blue gas with a sharp smell and is a strong oxidising agent. Ozone absorbs harmful ultraviolet radiation in the atmosphere and is used for air purification, bleaching, and sterilisation.
Q36 — Chlorine Dioxide: Preparation & Uses
Q36. Briefly describe the preparation and uses of chlorine dioxide (ClO2). (6 marks)
Answer:
Chlorine dioxide is prepared by reacting sodium chlorite with chlorine gas or by reducing sodium chlorate under controlled conditions. It is a yellowish-green gas with strong oxidising properties. Chlorine dioxide is widely used for bleaching paper pulp and disinfecting drinking water because it does not produce toxic chlorinated by-products.
Q37 — Interhalogen Compounds: Examples
Q37. What are interhalogen compounds? Briefly explain with examples. (6 marks)
Answer:
Interhalogen compounds are formed when two different halogens combine. They are more reactive than pure halogens due to their polar bonds. Examples include ClF3, a powerful fluorinating agent, and ICl, used in organic synthesis. These compounds show expanded valency and are used in industrial and chemical applications.
Q38 — Ammonia: Preparation & Uses
Q38. Write a brief note on ammonia and its uses. (6 marks)
Answer:
Ammonia is prepared industrially by the Haber process using nitrogen and hydrogen under high temperature and pressure. It is a colourless gas with a characteristic pungent smell and is highly soluble in water. Ammonia is used in fertilizers, cleaning solutions, refrigeration systems, and numerous chemical syntheses.
Q39 — Flux and Slag: Role in Metallurgy
Q39. Briefly explain the role of flux and slag in metallurgy. (6 marks)
Answer:
Flux is a substance added to ore during smelting to remove impurities. The flux combines with gangue to form slag, which is a fusible by-product. For example, limestone acts as a flux to remove silica impurities by forming calcium silicate slag. This process ensures that the pure metal separates easily from unwanted materials.
Q40 — Smelting: Process and Purpose
Q40. Write a short note on smelting. (6 marks)
Answer:
Smelting is the process of heating the ore with a suitable reducing agent to extract the metal in molten form. Common reducing agents include carbon or carbon monoxide. Smelting breaks down metal oxides and produces the metal along with gaseous by-products. This method is widely used for iron, copper, and zinc extraction.
Q41 — Carbon Reduction: Example
Q41. Explain carbon reduction in metallurgy with an example. (6 marks)
Answer:
Carbon reduction involves using coke or charcoal to reduce metal oxides at high temperatures. For example, iron oxide reacts with carbon monoxide in a blast furnace to form molten iron. This method is economical and effective for metals whose oxides can be reduced by carbon.
Q42 — Liquation: Separation Method
Q42. Briefly describe liquation. (6 marks)
Answer:
Liquation is a metallurgical process used to separate metals with low melting points from impurities or other metals with higher melting points. The mixture is gently heated so that the low-melting metal melts and drains away, leaving solid impurities behind. It is used for purifying metals such as lead and tin.
Q43 — Mond’s Process for Nickel Purification
Q43. Write a brief note on Mond’s process for nickel purification. (6 marks)
Answer:
In Mond’s process, impure nickel reacts with carbon monoxide at around 50°C to form nickel carbonyl, a volatile complex. This gas is then heated to 180°C, where it decomposes to give pure nickel and carbon monoxide. This process yields very high-purity nickel.
Q44 — Chlorination Process in Metallurgy
Q44. Briefly explain the chlorination process used in metallurgy. (6 marks)
Answer:
Chlorination involves converting metal compounds into volatile metal chlorides using chlorine gas. These volatile chlorides are then separated and reduced to obtain the pure metal. This method is commonly used for titanium and zirconium extraction because their chlorides easily vaporise and purify.