Metals, Minerals, Ores: Properties, Uses is part of Chemistry. Below are notes on 12 sub-topics, followed by practice MCQs from State PSC and UPSC papers.

Alloys: definition, purpose, composition, and uses of common alloys (e.g., brass, bronze, stainless steel, duralumin)

  • Alloy: Homogeneous mixture of two or more metals, or a metal and a non-metal.
  • Purpose of Alloys: To enhance properties like strength, hardness, corrosion resistance, malleability, ductility, or to lower the melting point.
  • Brass: Alloy of Copper (Cu) and Zinc (Zn). Uses: Utensils, decorative items, cartridges.
  • Bronze: Alloy of Copper (Cu) and Tin (Sn). Uses: Statues, coins, bells, bearings.
  • Stainless Steel: Alloy of Iron (Fe), Chromium (Cr), and Nickel (Ni), with a small amount of Carbon (C). Purpose: High corrosion resistance. Uses: Utensils, surgical instruments, architectural structures.
  • Duralumin: Alloy of Aluminum (Al), Copper (Cu), Magnesium (Mg), and Manganese (Mn). Purpose: Lightweight and high strength. Uses: Aircraft parts, pressure cookers.
  • German Silver: Alloy of Copper (Cu), Zinc (Zn), and Nickel (Ni). It does not contain any actual silver (Ag). Uses: Utensils, ornaments.
  • Horn Silver: Silver chloride (AgCl). Contains silver.
  • Ruby Silver: Silver arsenic sulfide (Ag3AsS3). Contains silver.
  • Lunar Silver: An archaic term for pure silver (Ag) or silver nitrate (AgNO3). Contains silver.
  • Sodium-Potassium (NaK) Alloy: An alloy of Sodium (Na) and Potassium (K) used as a liquid metal coolant for heat transfer in nuclear reactors due to its low melting point and high thermal conductivity.
  • Catalytic Converter: Uses Platinum (Pt), Rhodium (Rh), and Palladium (Pd) as catalysts to convert harmful exhaust gases (e.g., carbon monoxide, nitrogen oxides, unburnt hydrocarbons) into less toxic substances (carbon dioxide, nitrogen, water).
  • Carbon Content in Iron Forms:
    • Pig Iron: Highest carbon content
    • Steel: Intermediate carbon content
    • Wrought Iron: Lowest carbon content (< 0.1%), purest form of commercial iron.
    • Alloy Steel: Steel with additional alloying elements; carbon content varies.
  • Annealing: A heat treatment process for steel (and other metals) primarily performed to relieve internal stresses, increase ductility, reduce hardness, and refine grain structure.

Chemical properties of metals (reaction with oxygen, water, acids, bases, other metal salts)

  • Reactivity Series (Decreasing Order): K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au > Pt.
  • Reaction with Oxygen (Air):
    • Most metals react with O₂ to form metal oxides.
    • Highly Reactive (K, Na): React vigorously and exothermically with atmospheric O₂ and moisture, often igniting. Stored in kerosene oil to prevent this.
    • Moderately Reactive (Mg, Al, Zn, Fe, Pb, Ti): React upon heating. Form protective oxide layers (e.g., Al, Zn, Pb oxides are amphoteric, reacting with both acids and bases).
    • Least Reactive / Noble Metals (Ag, Au, Pt): Do not react with oxygen. Silver does not form oxide. Platinum and Gold do not react directly.
  • Reaction with Water:
    • Highly Reactive (K, Na, Cs): React violently with cold water, producing H₂ gas and metal hydroxide (base). Reaction is highly exothermic, often igniting H₂. Reactivity order with water: Cs > K > Na > Li (Lithium is the least reactive among these alkali metals).
    • Calcium (Ca): Reacts less violently with cold water, producing H₂ and Ca(OH)₂. Floats due to H₂ bubbles adhering to its surface.
    • Magnesium (Mg): Does not react with cold water (or reacts very slowly), but reacts with hot water/steam to form Mg(OH)₂ and H₂. Floats in cold water due to H₂ bubbles from any slow reaction.
    • Aluminium (Al), Zinc (Zn), Iron (Fe): React with steam (not cold or hot water) to form metal oxides and H₂.
    • Lead (Pb), Copper (Cu), Silver (Ag), Gold (Au), Platinum (Pt): Do not react with water (cold or steam) at all.
    • General: Active metal + water → Metal hydroxide (base) + Hydrogen gas.
  • Reaction with Acids (Dilute Non-oxidizing Acids like HCl, H₂SO₄):
    • Metals above H in the reactivity series (e.g., K, Na, Ca, Mg, Al, Zn, Fe, Pb) react to produce H₂ gas and a metal salt.
    • Metals below H in the reactivity series (e.g., Cu, Hg, Ag, Au, Pt) do NOT react with dilute non-oxidizing acids to produce H₂ gas.
    • Special Case (Ca + H₂SO₄): Reaction stops quickly as insoluble Calcium Sulfate (CaSO₄) forms a protective layer on the metal surface, preventing further reaction (passivation).
    • Noble Metals (Au, Pt): Extremely unreactive; do not react with common acids (Gold reacts with aqua regia).
  • Reaction with Bases:
    • Amphoteric Metals (Al, Zn, Pb, Sn): React with strong bases (e.g., NaOH) to produce H₂ gas and a complex salt (e.g., sodium aluminate, sodium zincate).
  • Reaction with Other Metal Salts:
    • A more reactive metal displaces a less reactive metal from its salt solution (based on the reactivity series).
  • Storage of Reactive Metals:
    • Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs): Stored under kerosene oil to prevent reaction with atmospheric oxygen and moisture. These metals are denser than kerosene.
    • Lithium (Li): Highly reactive but less dense than kerosene, so it floats and is not stored in kerosene; typically stored in paraffin wax or mineral oil.
    • Magnesium (Mg), Lead (Pb): Do not require storage in oil or kerosene.
    • Reason for storage: To prevent violent, exothermic reactions with air and moisture.
  • Photodecomposition of Silver Chloride (AgCl):
    • AgCl turns grey in sunlight due to decomposition: 2AgCl(s) → 2Ag(s) + Cl₂(g).
    • Forms silver metal. This is an endothermic (energy-absorbing) decomposition reaction.

Corrosion of metals: causes, mechanism (rusting), and prevention methods (galvanization, anodizing, electroplating, alloying, painting)

prevention

methods

(galvanization,

anodizing,

electroplating,

alloying, painting)

  • Corrosion: Deterioration of metals due to chemical or electrochemical reactions with their environment (e.g., air, moisture, acids).
  • Causes of Corrosion: Primarily the presence of oxygen and moisture (water).
  • Mechanism (Rusting of Iron):
    • An electrochemical process.
    • Occurs when iron is exposed to both oxygen and moisture.
    • Product: Hydrated iron(III) oxide (Fe₂O₃.xH₂O), commonly known as rust, which is a reddish-brown, flaky substance.
    • Weight of iron increases upon rusting due to the combination with oxygen and water molecules.
  • Corrosion of Other Metals:
    • Silver: Tarnishes (turns black) in air due to reaction with sulfur compounds (e.g., H₂S) forming silver sulfide (Ag₂S).
    • Copper: Forms a green coating (e.g., on the Statue of Liberty) when exposed to moist air containing carbon dioxide, creating basic copper carbonate (CuCO₃.Cu(OH)₂).
    • Aluminium: Corrodes rapidly but forms a thin, dense, protective layer of aluminium oxide (Al₂O₃) on its surface, which prevents further corrosion (passivation).
  • Prevention Methods:
    • Galvanization:
      • Process: Coating iron or steel with a thin layer of zinc.
      • Zinc is more electropositive than iron, thus acts as a sacrificial anode, corroding preferentially and protecting the iron from rusting.
    • Anodizing:
      • Process: An electrochemical method to thicken the natural protective oxide layer on metals like aluminium, titanium, and magnesium.
      • The metal article (e.g., aluminium) acts as the anode, forming a denser layer of its own oxide (e.g., aluminium oxide, Al₂O₃).
      • Increases corrosion resistance and is used in industries like aircraft manufacturing.
    • Electroplating: Depositing a thin layer of a non-corrosive metal (e.g., chromium, nickel) onto another metal using an electric current.
    • Alloying: Mixing metals to create corrosion-resistant alloys.
      • Example: Stainless steel (iron alloyed with chromium and nickel) is protected by a passive chromium oxide layer.
    • Painting: Applying a protective coat of paint acts as a barrier, preventing contact between the metal surface and corrosive agents (oxygen, moisture).

Definition and classification of metals, non-metals, and metalloids

  • Elements are broadly classified into Metals, Non-metals, and Metalloids based on their properties.
  • Metals:
    • Generally good conductors of heat and electricity, lustrous, malleable, and ductile.
    • Noble Metals:
      • Highly resistant to corrosion and oxidation.
      • Found in pure (free) form in nature due to low reactivity.
      • Examples: Gold (Au), Platinum (Pt), Silver (Ag). Uranium and Lead are NOT noble metals.
    • Free State Occurrence: Gold and Platinum are commonly found in the free state. Copper and Silver can also occur in the free state.
    • Specific Metals and Symbols:
      • Tungsten: Symbol 'W'.
      • Silver: Symbol 'Ag'.
    • Iron Classification: Depending on chemical composition and mechanical properties, iron is classified as Cast Iron, Wrought Iron, and Steel.
    • Rare-Earth Elements (REEs):
      • A group of 17 elements, comprising the 15 lanthanides plus Scandium (Sc) and Yttrium (Y).
      • All REEs are metals.
      • They are difficult to mine.
      • China is the largest global producer of rare-earth elements, not India.
      • Examples used in electrical/ electronic components: Scandium (Sc), Lanthanum (La), Cerium (Ce).
      • Radium (Ra) is an alkaline earth metal, not a rare-earth metal.
  • Non-metals:
    • Generally poor conductors of heat and electricity, brittle, and dull.
    • Asbestos: A naturally occurring fibrous silicate mineral. No longer preferred for commercial use because it causes lung cancer.
  • Metalloids (Semimetals):
    • Exhibit properties intermediate between metals and non-metals.
    • Examples: Boron (B), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb), Tellurium (Te).
    • Gallium (Ga) is a metal, not a metalloid.
  • Naturally Occurring Substances and Their Elemental Composition:
    • Diamond: Carbon (C).
    • Marble (Calcium Carbonate): Calcium (Ca).
    • Sand (Silicon Dioxide): Silicon (Si).
    • Ruby (Aluminum Oxide): Aluminum (Al).
  • Alloys vs. Elements: Steel is an alloy (primarily iron and carbon), while Nickel, Iron, and Copper are pure metallic elements.

Distinction between minerals and ores

  • Mineral: Naturally occurring solid, inorganic substance with a definite chemical composition and characteristic crystalline structure.
  • Ore: A mineral or rock from which a metal can be extracted economically and profitably.
  • Key Distinction: Economic viability. A mineral is classified as an ore only if the metal extraction process is financially feasible.
  • Relationship: All ores are minerals, but all minerals are NOT ores (as not all minerals contain metals in sufficient concentration or form for profitable extraction).
  • Examples of Silicate Minerals: Feldspar, Zeolite, Mica (contain silicon and oxygen).
  • Example of Non-Silicate Ore: Bauxite (primary ore of Aluminum, mainly composed of hydrated aluminum oxides/hydroxides; it is NOT a silicate).

Extraction of metals from concentrated ores (roasting, calcination, smelting, electrolytic reduction)

  • Roasting: Heating a sulphide ore strongly in excess air to convert it into a metal oxide. (e.g., 2ZnS + 3O₂ → 2ZnO + 2SO₂).
  • Calcination: Heating a carbonate or hydrated ore strongly in limited or no air to convert it into a metal oxide. Releases CO₂ from carbonates and H₂O from hydrates. (e.g., ZnCO₃ → ZnO + CO₂; Al₂O₃·2H₂O → Al₂O₃ + 2H₂O).
  • Smelting: A metallurgical process where a metal is obtained in a fused (molten) state, typically by reduction of its oxide (often with carbon or CO) at high temperatures.
  • Reduction with Carbon (Coke): Used for extracting moderately reactive metals from their oxides (e.g., Zinc, Iron, Lead, Copper). (ZnO + C → Zn + CO).
  • Reduction with Aluminium (Thermit Reaction): Used for oxides of metals less reactive than Aluminium, or when high purity and a molten state are needed. Aluminium acts as the reducing agent.
    • Reaction is highly exothermic.
    • For railway tracks: Iron(III) oxide (Fe₂O₃) reacts with Aluminium. (Fe₂O₃(s) + 2Al(s) → 2Fe(l) + Al₂O₃(s)). Aluminium is the reducing agent.
    • For Manganese extraction: Manganese dioxide (MnO₂) reacts with Aluminium powder. (3MnO₂(s) + 4Al(s) → 3Mn(l) + 2Al₂O₃(s)). For 1 mole of Mn, 4/3 (≈1.33) moles of Al are required.
  • Electrolytic Reduction: Used for extracting highly reactive metals (e.g., Aluminium, Sodium, Magnesium) which cannot be reduced by carbon, from their molten salts or oxides. Metal is produced directly by an electrical process.
  • Aluminium Extraction:
    • Ore: Bauxite (Al₂O₃·xH₂O).
    • Concentration/Purification: Bayer's Process converts bauxite to pure alumina (Al₂O₃).
    • Extraction: Electrolytic reduction of molten alumina (Hall-Héroult process) to produce Aluminium metal.

General principles of metallurgy: concentration, reduction, refining

  • Highly reactive metals (e.g., Na, K, Ca, Mg, Al) occur only in combined state and are generally extracted by electrolysis of their fused salts.
  • Moderately reactive metals (e.g., Cu, Ag) can occur in both native (free) and combined states.
  • Least reactive metals (e.g., Au, Pt) occur primarily in the native (free) state.
  • Aluminium (Al) and Magnesium (Mg) are strong reducing agents often employed in metallurgical processes.
  • Thermite Reaction: Reaction of iron(III) oxide (Fe₂O₃) with aluminium powder.
  • Equation: Fe₂O₃ + 2Al → 2Fe (molten) + Al₂O₃ + Heat.
  • In the thermite reaction, aluminium acts as a reducing agent, reducing Fe₂O₃ to molten iron.
  • The significant heat evolved in the thermite reaction is used for welding purposes (e.g., railway tracks).
  • Nickel (Ni) is a commonly used catalyst for the hydrogenation of vegetable oils. (Other catalysts include Pt, Pd).
  • The Iron-Carbon diagram (phase diagram) is determined under equilibrium conditions.
  • The Time-Temperature-Transformation (TTT) curve is determined under non-equilibrium conditions.

Important ores of common metals (e.g., iron, aluminum, copper, zinc, lead, mercury) and their chemical formulae

  • Aluminium (Al):
    • Bauxite (Al₂O₃·nH₂O) - Most important/primary ore.
    • Manufactured from Bauxite ore.
    • Found in abundance in India.
    • Alumina (Al₂O₃) is a component of cement.
  • Iron (Fe):
    • Hematite (Fe₂O₃)
    • Magnetite (Fe₃O₄)
    • Siderite (FeCO₃)
    • Iron-oxide (Fe₂O₃) is a component contributing to cement properties.
  • Copper (Cu):
    • Malachite (Cu₂CO₃(OH)₂)
    • Bornite (Cu₅FeS₄) - Common ore.
  • Zinc (Zn):
    • Sphalerite (ZnS)
    • Calamine (ZnCO₃)
  • Lead (Pb):
    • Galena (PbS) - Ore of lead.
    • Symbol: Pb.
    • White lead is the trade name for basic lead carbonate ((PbCO₃)₂·Pb(OH)₂).
  • Mercury (Hg):
    • Cinnabar (HgS) - Primary ore.
    • Symbol: Hg.
    • Used in conventional glass thermometers.
  • Manganese (Mn):
    • Pyrolusite (MnO₂)
    • Psilomelane
    • Braunite
  • Magnesium (Mg):
    • Dolomite (MgCO₃·CaCO₃) - Ore of Magnesium (also contains Calcium).
    • Dolomite is used as a soil conditioner.
  • Calcium (Ca):
    • Gypsum (CaSO₄·2H₂O) - Contains Calcium.
    • Lime (CaO) is a main cementing property in cement.
  • Other Important Ores/Minerals:
    • Rock salt (NaCl) - A halide ore.
  • Gemstones:
    • Emerald - Contains beryllium metal.
  • Cement Composition:
    • Cementing property mainly due to: Lime (CaO), Silica (SiO₂), Iron-oxide (Fe₂O₃), Alumina (Al₂O₃).

Physical properties of metals (luster, malleability, ductility, conductivity, density, melting/boiling points)

  • Luster: Metals exhibit a characteristic shiny surface (metallic luster).
  • Malleability: The property of metals to be beaten into thin sheets (e.g., Zinc, Gold, Silver) without breaking.
  • Ductility: The property of metals to be drawn into thin wires. Gold is the most ductile metal; Platinum, Silver, and Copper are also highly ductile.
  • Conductivity: Metals are excellent conductors of both heat and electricity.
    • Electrical Conductivity: Silver is the best electrical conductor, followed by Copper.
    • Molten ionic compounds (e.g., molten Lithium Chloride) also conduct electricity due to mobile ions.
  • Density: Metals generally have high densities.
    • Lightest Metal: Lithium (Li).
    • Heaviest Metals: Osmium (Os) and Iridium (Ir) are the densest elements. Platinum (Pt) is also very dense and often cited as the heaviest among common metals.
  • Melting & Boiling Points: Most metals have high melting and boiling points (e.g., Iron melts at ~1538°C).
    • Low Melting Points: Alkali metals (Lithium, Sodium, Potassium, Rubidium, Caesium) have relatively low melting points.
    • Trend for Alkali Metals: Melting point decreases down the group (Li > Na > K > Rb > Cs). Thus, Caesium has the lowest melting point, and Lithium has the highest among alkali metals.
    • Liquid at Room Temperature: Mercury (Hg) is liquid at ordinary temperatures (e.g., 25°C). Gallium (Ga) also melts just above room temperature (~29.76°C).
  • Hardness: Most metals are hard.
    • Soft Metals: Alkali metals (Lithium, Sodium, Potassium) are soft enough to be cut with a knife.
    • Softest Mineral: Talc (Mohs scale 1).
  • Metallic Bonding: Characterized by non-directionality, which contributes to properties like malleability and ductility.

Reactivity series of metals and its applications

Reactivity Series: A list of metals arranged in 1. the decreasing order of their reactivity. Reactivity is fundamentally determined by a 2. metal's tendency to lose electrons (electronreleasing tendency or electropositivity). More reactive metals lose electrons more easily. Common Reactivity Series (decreasing or3. der): Potassium (K) > Sodium (Na) > Calcium (Ca) > Magnesium (Mg) > Aluminium (Al) > Zinc (Zn) > Iron (Fe) > Lead (Pb) > Hydrogen (H) > Copper (Cu) > Mercury (Hg) > Silver (Ag) > Gold (Au). Applications: Displacement Reactions 4.

    • A more reactive metal displaces a less reactive metal from its salt solution.
    • Feasible Reaction: `More reactive metal + Salt solution of less reactive metal → Salt solution of more reactive metal + Less reactive metal`.
    • Example: `Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)` (Zn is more reactive than Cu).
    • Non-feasible Reaction: `Less reactive metal + Salt solution of more reactive metal → No reaction`.
    • Example: `Cu(s) + FeSO₄(aq) → No reaction` (Cu is less reactive than Fe).
    • Example: `Cu(s) + PbCl₂(aq) → No reaction` (Cu is less reactive than Pb).
    • Example: `Mg(s) + CaCl₂(aq) → No reaction` (Mg is less reactive than Ca).
    • Example: `Ag(s) + CuSO₄(aq) → No reaction` (Ag is less reactive than Cu). Applications: Reaction with Dilute Acids 5. (e.g., HCl)
    • Metals positioned above Hydrogen in the reactivity series displace Hydrogen from dilute acids to form a salt and Hydrogen gas.
    • Example: `Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)`.
    • Reactivity order with HCl: Mg > Al > Zn > Fe (all are above Hydrogen).
    • Metals positioned below Hydrogen (e.g., Cu, Hg, Ag, Au) do not react with dilute acids to produce Hydrogen gas. Metals higher in the series generally react 6. more vigorously with oxygen, water, and acids. Metals like Potassium (K), Sodium (Na) are 7. highly reactive.

Refining of metals (electrolytic refining, zone refining, liquation, distillation, vapor phase refining)

  • Electrolytic Refining: Process for obtaining high purity metals.
    • Principle: More reactive metals from the impure anode dissolve into the electrolyte, while less reactive impurities settle as anode mud. Pure metal ions from the electrolyte deposit on the cathode.
    • Setup: Impure metal serves as the Anode, a thin strip of pure metal as the Cathode, and a soluble salt of the metal as the Electrolyte.
    • Used for: Cu, Zn, Ag, Au, Ni, Sn, Pb.
    • Copper Refining Example:
      • Anode: Impure Copper
      • Cathode: Thin sheet of pure Copper
      • Electrolyte: Acidified Copper Sulphate (CuSO₄) solution
      • Anode Reaction: Cu (impure) → Cu²⁺ + 2e⁻
      • Cathode Reaction: Cu²⁺ + 2e⁻ → Cu (pure)
  • Zone Refining: Method for producing ultrapure metals, especially for semiconductors.
    • Principle: Impurities are more soluble in the molten state of the metal than in the solid state.
    • Process: A narrow circular heater moves along an impure metal rod, creating a molten zone. As the heater moves, impurities preferentially remain in the molten zone and are carried to one end of the rod.
    • Used for: Germanium (Ge), Silicon (Si), Gallium (Ga), Boron (B), Indium (In).
  • Liquation: Used for metals with a significantly lower melting point than their impurities.
    • Principle: Differences in melting points.
    • Process: Impure metal is heated on a sloping hearth; the pure metal melts and flows down, leaving behind higher melting impurities.
    • Used for: Tin (Sn), Lead (Pb), Bismuth (Bi).
  • Distillation: Applicable for metals with low boiling points.
    • Principle: Significant difference in boiling points between the metal and its impurities.
    • Process: The impure metal is heated to its boiling point, vaporizes, and the pure metal vapor is then condensed and collected.
    • Used for: Zinc (Zn), Cadmium (Cd), Mercury (Hg).
  • Vapor Phase Refining: Involves converting the metal into a volatile compound, which is then decomposed to yield pure metal.
    • Requirements: The metal must form a volatile 1. compound with an available reagent. The volatile compound must be 2. easily decomposable to pure metal.
    • Mond's Process (for Nickel):
      • Impure Ni reacts with CO to form volatile nickel tetracarbonyl (Ni(CO)₄).
      • Ni(impure) + 4CO (330-350K) → Ni(CO)₄ (volatile)
      • Ni(CO)₄ is then heated to a higher temperature to decompose, yielding pure nickel.
      • Ni(CO)₄ (450-470K) → Ni(pure) + 4CO
    • van Arkel Process (for Titanium, Zirconium):
      • Impure metal reacts with iodine to form a volatile metal iodide.
      • Ti(impure) + 2I₂ (523K) → TiI₄ (volatile)
      • The iodide vapor is then decomposed on a hot tungsten filament to obtain pure metal.
      • TiI₄ (1700K on hot filament) → Ti(pure) + 2I₂
  • Purest form of Iron: Wrought iron (contains <0.25% carbon and other impurities).

Uses of common metals and their compounds in industries and daily life

  • Limestone is the main ingredient of cement.
  • Gypsum (Calcium Sulfate Dihydrate) is added to cement to increase its setting time and prevent flash setting.
  • Plaster of Paris (Calcium Sulfate Hemihydrate) is manufactured from Gypsum.
  • Platinum is often referred to as 'white metal', especially in jewelry; Rhodium and Palladium are also platinum group metals.
  • Strontium compounds are used to produce a bright red color in fireworks.
  • Magnesium is used in fireworks to produce a bright white light.
  • Rhodium, Platinum, and Palladium are used as catalysts in catalytic converters to eliminate poisonous gases from exhaust.
  • 24 karat gold is pure gold (100% gold) and is very soft.
  • 22 karat gold contains 22 parts pure gold and 2 parts other metals (usually copper or silver), making it approximately 91.67% pure and suitable for ornaments.
  • 18 karat gold comprises 18 parts pure gold and 6 parts other metals, equating to 75% gold, mixed with copper or silver to increase hardness.
  • Cadmium, Mercury, and Lead are toxic metals. Sodium is an essential electrolyte and non-toxic in physiological amounts.
  • Iron is the second most abundant metal in the Earth's crust (after Aluminium).
  • Platinum (Pt) and Gold (Au) occur naturally in their free (native) state due to their low reactivity.
  • Lithium (Li) is a key component in batteries, including lithium-ion batteries used in mobile phones and smartphones.
  • Sodium (Na) is vital for controlling the water content in the blood and facilitating the transfer of nerve impulses.
  • Potassium (K) is essential for the transfer of nerve impulses.
  • Cesium (Cs) is used as a timekeeper in atomic clocks due to its precise atomic transitions.
  • Tin (Sn) is used for coating brass/copper utensils (known as 'kalai') to prevent copper contamination and to coat food cans because it is less reactive than zinc, thus preventing reaction with food.
  • Zinc (Zn) is more reactive than Tin.
  • Barium sulfate (BaSO₄), a barium compound, is used as a contrast agent in medicine for Xray examination of the alimentary canal (barium meal).
  • The red color of gemstone Ruby is due to chromium impurities, not beryllium.
  • Magnesium (Mg) is a central atom in chlorophyll, essential for photosynthesis in green plants.
  • Vitamin B-12 contains Cobalt (Co).
  • Hemoglobin contains Iron (Fe), which binds oxygen in the blood.
  • Chalcopyrite (CuFeS₂) is a primary ore containing Copper (Cu) and Iron (Fe).
  • Zinc Oxide (ZnO) is used in glazing pottery.
  • Silver Bromide (AgBr) and other silver halides are coated on photographic plates/films due to their light sensitivity.
  • Aluminium sulphate (and other aluminium compounds like aluminium hydroxide) can be used to make fireproof clothing due to their fire-retardant properties.
  • Liquid Sodium is employed as a coolant in fast breeder nuclear reactors.
  • Calcium carbonate is commonly used as a mild abrasive and filler ingredient in toothpaste.
  • Bordeaux mixture, a fungicide, consists of copper sulfate and lime (calcium hydroxide), not sodium sulfate.
  • Hexavalent chromium (Cr⁺⁶) is a highly toxic and carcinogenic species of chromium in water.
  • Flame photometry is a suitable method for the determination of alkali metals (Li, Na, K, Rb, Cs) and some alkaline earth metals (Ca, Sr, Ba) by measuring their characteristic flame emissions.
  • Aluminium powder, suspended in oil, is used as paint for its metallic luster and protective qualities.
  • Thermit welding uses Aluminium powder because of its strong affinity for oxygen (it's a potent reducing agent), leading to highly exothermic reactions with metal oxides (e.g., iron oxide).
  • Class D fires involve combustible metals such as magnesium, aluminium, lithium, zinc, sodium, and potassium.
  • Potassium permanganate (KMnO₄) is used as an ethylene scavenger in active packaging to delay the ripening of fruits and vegetables.
  • Titanium is a metal known for its high strength-to-weight ratio, corrosion resistance, and is used extensively in aerospace and defense materials.
  • Crystalline silicon is a crucial material in solar cell production and is also known as solar grade silicon.
  • Heater coils (e.g., in electric heaters, toasters) are typically made of Nichrome (an alloy of Nickel and Chromium) due to its high electrical resistance and ability to withstand high temperatures without oxidation.
  • Tungsten (W) is primarily used for filaments in incandescent light bulbs due to its very high melting point and strength at high temperatures.

5. Alloys

Practice MCQs: Metals, Minerals, Ores: Properties, Uses

Alloys: definition, purpose, composition, and uses of common alloys (e.g., brass, bronze, stainless steel, duralumin)

  1. Which one of the following does not contain silver ?

    Asked in: HPPSC HPAS Prelims 2014

    1. Horn Silver
    2. German Silver
    3. Ruby Silver
    4. Lunar Silver
    Show answer

    Answer: B. German Silver

    German Silver is an alloy composed of copper, nickel, and zinc. Despite its name and silvery appearance, it contains no silver.

  2. Which one of the following metals is alloyed with sodium to transfer heat in a nuclear reactor ?

    Asked in: UPSC NDA 1 2018

    1. Potassium
    2. Calcium
    3. Magnesium
    4. Strontium
    Show answer

    Answer: A. Potassium

    Sodium-Potassium (NaK) alloy is a common liquid metal coolant in nuclear reactors due to its excellent heat transfer properties. Ans: A law officier -2025 The darkening of photochromatic glass is due to the reversible formation of colloidal silver particles from silver halides (primarily silver chloride or bromide) under UV radiation.

  3. Catalytic converter transforms waste gases from the engines of many cars into carbon dioxide, nitrogen and water. The catalyst is made of

    Asked in: UPSC CISF AC EXE 2019

    1. platinum and copper
    2. molybdenum and copper
    3. platinum and rhodium
    4. rhodium and molybdenum
    Show answer

    Answer: C. platinum and rhodium

    Platinum and rhodium are commonly used together in catalytic converters, particularly in three-way converters, which target carbon monoxide (CO), unburnt hydrocarbons (HC), and nitrogen oxides (NOx).

  4. The amount of carbon is highest in

    Asked in: UPPSC Upper Mains 2014

    1. Pig iron
    2. Wrought iron
    3. Steel
    4. Alloy steel
    Show answer

    Answer: A. Pig iron

    Pig iron is a high-carbon product from blast furnaces, used as a raw material for making steel and cast iron.

  5. What is the primary purpose of annealing in the heat treatment of steel ? - (5) Question not attempted

    Asked in: Assistant Eng. (Mechanical) Competitive Examination, 2023

    1. Increasing hardness
    2. Improving corrosion resistance
    3. Relieving stress
    4. Enhancing wear resistance
    Show answer

    Answer: C. Relieving stress

    Annealing is a heat treatment process primarily used to soften metals and relieve internal stresses.

Chemical properties of metals (reaction with oxygen, water, acids, bases, other metal salts)

  1. Which one of the following metals is kept immersed in Kerosene oil to protect it and to prevent accidental fire ?

    Asked in: UPSC CDS 1 2021

    1. Calcium
    2. Sodium
    3. Vanadium
    4. Magnesium
    Show answer

    Answer: B. Sodium

    - Alkali metals like sodium and potassium are very reactive due to their low ionization energies. - Kerosene is a non-polar hydrocarbon that does not react with sodium and acts as a barrier against air and moisture.

  2. Which one of the following does not form oxide on reaction with oxygen?

    Asked in: UPSC CDS 2 2020

    1. Magnesium
    2. Lead
    3. Tin
    4. Silver
    Show answer

    Answer: D. Silver

    Reactivity with oxygen varies among metals. Highly reactive metals like Magnesium react readily, forming stable oxides. Lead and Tin are less reactive than Magnesium but still form oxides. Silver is one of the least reactive metals and does not readily oxidize.

  3. Which one among the following metals is not stored under oil ?

    Asked in: UPSC CDS 2 2024

    1. Sodium
    2. Rubidium
    3. Potassium
    4. Lithium
    Show answer

    Answer: D. Lithium

    - Alkali metals are highly reactive. - Storage under oil or inert atmosphere prevents reaction with air and moisture. - Lithium's reactivity and reaction products differ somewhat from heavier alkali metals.

  4. Which of the following do not react with water at all ?

    Asked in: CGPSC Prelims Exam 2015

    1. Iron
    2. Lead
    3. Magnesium
    4. Aluminium
    Show answer

    Answer: B. Lead

    - Reactivity of metals with water varies. Some react with cold water (e.g., alkali metals), some with hot water/steam (e.g., Mg, Al, Fe), and some react very slowly or not at all (e.g., noble metals, Pb). - Passivation is the formation of a protective layer of oxide or hydroxide on the metal surface that prevents further reaction. Aluminium and Lead are prone to passivation. - Iron rusts, which is a reaction involving water and oxygen. Magnesium reacts with hot water and steam. Aluminium reacts with boiling water and steam, and forms a passive layer at room temperature.

  5. Why silver chloride turns grey in Sunlight?

    Asked in: UPSC Geoscientist 2021

    1. It forms silver metal and is an example of endothermic reaction
    2. It forms silver metal and is an example of exothermic reaction
    3. It forms silver metal and is an example of substitution reaction
    4. It forms silver ion (Ag+) and is an example of endothermic reaction
    Show answer

    Answer: A. It forms silver metal and is an example of endothermic reaction

    Sunlight decomposes silver chloride (AgCl) into grey silver metal (Ag) and chlorine gas. This decomposition is an endothermic reaction.

  6. Which one of the following elements will not react with dilute HCl to produce H2 ?

    Asked in: UPSC NDA 1 2016

    1. Hg
    2. Al
    3. Mg
    4. Fe
    Show answer

    Answer: A. Hg

    Dilute HCl is a non-oxidizing acid. Metals that are more reactive than hydrogen will react with such acids to displace hydrogen gas (H₂). The reactivity of metals can be determined from the electrochemical series (or reactivity series). Metals above hydrogen in the series are more reactive and will displace hydrogen from dilute acids. Metals below hydrogen will not. The relevant part of the reactivity series is (from more reactive to less reactive): ... Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au ... - Al, Mg, and Fe are all above hydrogen in the series, so they will react with dilute HCl to produce H₂ gas. - Hg (Mercury) is below hydrogen in the series, so it will not react with dilute HCl to produce H₂ gas.

  7. Which one of the following elements is least reactive with water ?

    Asked in: UPSC NDA 1 2017

    1. Lithium
    2. Sodium
    3. Potassium
    4. Cesium
    Show answer

    Answer: A. Lithium

    Reactivity of alkali metals with water increases from Lithium to Cesium.

  8. Which one of the following metals does NOT react with cold water ?

    Asked in: UPSC NDA 1 2019

    1. Calcium (Ca)
    2. Potassium (K)
    3. Magnesium (Mg)
    4. Sodium (Na)
    Show answer

    Answer: C. Magnesium (Mg)

    Alkali metals (like Potassium and Sodium) react vigorously or even explosively with cold water, producing hydrogen gas and their hydroxides. Calcium, an alkaline earth metal, also reacts with cold water, albeit less vigorously than sodium or potassium, forming calcium hydroxide and hydrogen gas. Magnesium, another alkaline earth metal, reacts very slowly with boiling water and reacts readily with steam to form magnesium oxide and hydrogen, but it does not react with cold water.

Corrosion of metals: causes, mechanism (rusting), and prevention methods (galvanization, anodizing, electroplating, alloying, painting)

  1. Galvanized iron pipes have a coating of

    Asked in: BPSC Prelims Exam 63rd

    1. zinc
    2. mercury
    3. lead
    4. chromium
    Show answer

    Answer: A. zinc

    - Galvanization is a widely used method for protecting metals, especially steel and iron, from corrosion (rusting). - The most common method is hot-dip galvanizing, where the steel or iron is immersed in a bath of molten zinc. - The zinc coating acts as a physical barrier preventing corrosive substances from reaching the underlying metal. - More importantly, zinc acts as a sacrificial anode. It is more electrochemically active than iron, so if the coating is scratched and the iron is exposed, the zinc will corrode preferentially, protecting the iron from rusting.

  2. What happens to the weight of iron, when it rusts?

    Asked in: BPSC Prelims Exam 67th Re Exam

    1. Decreases then increases
    2. Increases then decreases
    3. Remains same
    4. Increases for long time
    Show answer

    Answer: D. Increases for long time

    Rusting is a chemical reaction where iron combines with oxygen and water. The mass of the product (rust) is greater than the mass of the original iron because oxygen and water have been added.

  3. Silver articles become black after some time when exposed to air because

    Asked in: UPSC CDS 1 2020

    1. silver gets oxidized to silver oxide
    2. silver reacts with moist carbon dioxide in the air to form silver carbonate
    3. silver reacts with sulphur in the air to form a coating of silver sulphide
    4. silver reacts with nitrogen oxides in the air to form silver nitrate
    Show answer

    Answer: C. silver reacts with sulphur in the air to form a coating of silver sulphide

    - Silver reacts with sulfur compounds in the air. - The reaction produces silver sulfide (Ag₂S). - Silver sulfide is black, causing the tarnish.

  4. Which one of the following substances do silver articles react with, that makes the silver articles black ?

    Asked in: UPSC CDS 1 2021

    1. Sulphur
    2. Oxygen
    3. Carbon dioxide
    4. Phosphorus
    Show answer

    Answer: A. Sulphur

    - The tarnishing of silver is primarily caused by the reaction with sulphur compounds, not oxygen or carbon dioxide under normal atmospheric conditions. - The reaction is typically represented as: 2Ag(s) + H₂S(g) → Ag₂S(s) + H₂(g).

  5. Which one of the following is not true for anodizing process?

    Asked in: UPSC CDS 1 2023

    1. It makes aluminium corrosion resistant.
    2. Metals like aluminium, titanium and magnesium can be anodized.
    3. Clean aluminium article is the anode and oxygen gas is evolved at the cathode.
    4. It is used in aircraft industry.
    Show answer

    Answer: C. Clean aluminium article is the anode and oxygen gas is evolved at the cathode.

    - In anodizing, the metal article is the anode. - Anodizing enhances corrosion resistance, wear resistance, and allows for dyeing. - Hydrogen gas is typically evolved at the cathode during anodizing.

  6. Silver articles turn black when kept in the open for longer time due to the formation of

    Asked in: UPSC CDS 2 2020

    1. H₂S
    2. AgS
    3. AgSO₄
    4. Ag₂S
    Show answer

    Answer: D. Ag₂S

    Silver tarnish is caused by the formation of silver sulfide (Ag₂S) through the reaction of silver with hydrogen sulfide in the air.

  7. When copper reacts with moist carbon dioxide (CO₂) in air, it forms a green coating of which one of the following compounds ?

    Asked in: UPSC CDS 2 2021

    1. Cupric carbonate
    2. Cuprous oxide
    3. Cupric oxide
    4. Copper sulphate
    Show answer

    Answer: A. Cupric carbonate

    - The green coating on copper exposed to air is called patina. - Patina is formed by the reaction of copper with moisture, oxygen, and carbon dioxide. - The main component of green patina is basic copper carbonate.

  8. Example of corrosion is

    Asked in: CGPSC Prelims Exam 2016

    1. Black coating on Silver
    2. Green coating on Copper
    3. Brown coating on Iron
    4. Above three
    Show answer

    Answer: D. Above three

    Corrosion is the process of deterioration of materials, primarily metals, by chemical or electrochemical reaction with their environment. - Black coating on Silver: This is silver tarnish, caused by the reaction of silver with sulfur compounds in the air to form silver sulfide (Ag₂S). This is a form of corrosion. - Green coating on Copper: This green layer, known as patina, is formed when copper reacts with atmospheric moisture, carbon dioxide, and sulfur dioxide. It is primarily basic copper carbonate [Cu₂(OH)₂CO₃] and basic copper sulfate [Cu₂(OH)₂SO₄]. This is a form of corrosion. - Brown coating on Iron: This is rust, formed when iron reacts with oxygen and moisture in the air to form hydrated iron(III) oxide (Fe₂O₃·nH₂O). This is a common example of corrosion (rusting).

Definition and classification of metals, non-metals, and metalloids

  1. Consider the following statements: 1. Noble metals are found in pure form in nature. 2. Uranium and lead are examples of noble metal. Which of the above statements is/are correct?

    Asked in: BPSC Prelims Exam 67th Re Exam

    1. 2 only
    2. Both 1 and 2
    3. Brass is also noble metal
    4. 1 only
    Show answer

    Answer: D. 1 only

    Noble metals are characterized by their resistance to corrosion and oxidation in moist air, unlike most base metals. Due to their low reactivity, they are often found in pure metallic form in nature. Examples include gold, silver, platinum, palladium, rhodium, iridium, ruthenium, and osmium. Uranium and lead are reactive metals and are not considered noble metals; uranium is highly reactive and radioactive, and lead tarnishes readily in air. Brass is an alloy of copper and zinc and is not a noble metal (noble metals are elements).

  2. Which one of the following pairs of elements is found in the free state?

    Asked in: UPSC Geoscientist 2021

    1. Gold and Platinum
    2. Copper and Silver
    3. Gold and Silver
    4. Copper and Platinum
    Show answer

    Answer: A. Gold and Platinum

    Gold and Platinum are noble metals that are highly unreactive and commonly found in the free state.

  3. Asbestos is no longer preferred for commercial use because :

    Asked in: HPPSC HPAS Prelims 2010

    1. It causes lung cancer
    2. Its structures are very weak
    3. It is not sound proof
    4. It catches fire
    Show answer

    Answer: A. It causes lung cancer

    Asbestos is a group of naturally occurring fibrous minerals that were widely used in construction and industry due to their heat resistance and durability. However, inhaling asbestos fibres can cause serious health problems, including asbestosis (a chronic lung disease), mesothelioma (a rare and aggressive cancer of the lining of the lungs or abdomen), and lung cancer. Because of these severe health risks, its use has been banned or severely restricted in many countries.

  4. The symbol of the element ‘Tungsten’ is:

    Asked in: UPSC NDA 2 2015

    1. Ta
    2. W
    3. Tl
    4. Tc
    Show answer

    Answer: B. W

    The chemical symbol W represents the element Tungsten, derived from the name Wolfram.

  5. Match List-I with List-II and select the correct answer using the codes given below the lists: List-I List-II (Naturally occurring sub‐ (Elements stance) present)

    Asked in: UPPCS Prelims 2010

    1. Diamond 1. Calcium
    2. Marble 2. Silicon
    3. Sand 3. Aluminum
    4. Ruby 4. Carbon Codes: A B C D A. 3 1 2 4 B. 4 2 1 3 C. 2 1 3 4 D. 4 1 2 3
    Show answer

    Answer: D. Ruby 4. Carbon Codes: A B C D A. 3 1 2 4 B. 4 2 1 3 C. 2 1 3 4 D. 4 1 2 3

    The question asks to match naturally occurring substances with the primary elements present in them. Diamond is an allotrope of pure carbon. Marble is a metamorphic rock composed primarily of calcium carbonate (CaCO₃), so it contains calcium. Sand is commonly composed of silica (silicon dioxide, SiO₂), thus containing silicon. Ruby is a gemstone form of the mineral corundum (aluminum oxide, Al₂O₃), containing aluminum.

  6. Match List I (Naturally occurring substances) with List II (Elements) and select the correct answer using the codes given below the Lists: List I List II (Naturally occurring sub‐ (Elements) stances) I. Diamond D) Carbon II. Marble A) Calcium III. Sand B) Silicon C) Alumini‐ IV. Ruby um Codes:

    Asked in: UPPCS Prelims 1999

    1. I-C, II-A, III-B, IV-D
    2. I-D, II-B, III-A, IV-C
    3. I-B, II-A, III-C, IV-D
    4. I-D, II-A, III-B, IV-C
    Show answer

    Answer: D. I-D, II-A, III-B, IV-C

    - I. Diamond is a crystalline allotrope of Carbon. (I- D) - II. Marble is primarily composed of Calcium Carbonate (CaCO₃), so Calcium is a key element. (II-A) - III. Sand, commonly, is mostly Silicon Dioxide (SiO₂), making Silicon a key element. (III- B) - IV. Ruby is a variety of the mineral Corundum (Al₂O₃), making Aluminium the primary metallic element. (IV-C)

  7. Which one of the following is not a metalloid?

    Asked in: WBCS Main Paper 4 2023

    1. Boron
    2. Silicon
    3. Gallium
    4. Germanium
    Show answer

    Answer: C. Gallium

    Metalloids are elements that have properties intermediate between those of metals and nonmetals. Common metalloids include Boron (B), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb), Tellurium (Te), and sometimes Polonium (Po) and Astatine (At). Gallium (Ga) is a soft, silvery metal.

  8. Which one of the following statements is not true about rare-earth elements?

    Asked in: acf 2019

    1. It is a group of 17 elements.
    2. All elements are metals.
    3. India is the largest producer of those elements.
    4. These elements are very difficult to mine.
    Show answer

    Answer: C. India is the largest producer of those elements.

    Rare-earth elements (REEs) are a group of 17 chemical elements with similar properties. All these elements are metals and are difficult to mine and process. China dominates global production of rare- earth elements. While India has significant reserves, its production capacity is much lower compared to China.

Distinction between minerals and ores

  1. Which of the following is a wrong statement?

    Asked in: TNPSC CS Prelims 2017

    1. All the minerals are not ores
    2. All the ores are not minerals
    3. All the ores are minerals
    4. From ores, metals can be extracted economic‐ ally
    Show answer

    Answer: B. All the ores are not minerals

    A mineral is a naturally occurring solid with a defined chemical composition and crystal structure. An ore is a mineral or an aggregate of minerals from which a metal or other valuable substance can be extracted profitably.

  2. Which one of the following minerals is NOT a naturally occurring silicate ?

    Asked in: UPSC CAPF 2020

    1. Feldspar
    2. Zeolite
    3. Mica
    4. Bauxite
    Show answer

    Answer: D. Bauxite

    Silicate minerals are composed of silicon and oxygen, often with other metals, forming structures based on the SiO₄⁴⁻ tetrahedron unit. Non-silicate minerals lack this fundamental structure.

Extraction of metals from concentrated ores (roasting, calcination, smelting, electrolytic reduction)

  1. The metallurgical process in which a metal is obtained in a fused state is called

    Asked in: BPSC Prelims Exam 67th Re Exam

    1. roasting
    2. calcination
    3. froth floatation
    4. smelting
    Show answer

    Answer: D. smelting

    Smelting is a high-temperature reduction process that typically produces metal in a molten state, enabling separation from gangue (impurities) as slag.

  2. What is the name of the process that converts sulphide ores into oxides by heating strongly in the presence of excess air ?

    Asked in: UPSC CDS 2 2021

    1. Calcination
    2. Roasting
    3. Smelting
    4. Incineration
    Show answer

    Answer: B. Roasting

    - Roasting is specifically applied to sulphide ores. - It requires heating in the presence of excess air. - It converts the sulphide into a metal oxide and releases sulphur dioxide.

  3. In the joining of railway tracks, iron oxide is made to react with

    Asked in: UPSC CDS 2 2022

    1. Aluminium
    2. Zinc
    3. Copper
    4. Tin
    Show answer

    Answer: A. Aluminium

    - The thermite reaction involves the reduction of a metal oxide by a more reactive metal, producing a large amount of heat and molten metal. - The specific reaction used for rail welding is between iron(III) oxide (Fe₂O₃) and aluminium (Al): 2Al + Fe₂O₃ → Al₂O₃ + 2Fe + Heat. - The molten iron produced at high temperature fills the gap between the rails, creating a weld.

  4. During calcination process

    Asked in: MPSC CS Prelims 2019

    1. Only CO2 is given out
    2. Only H2O from hydrates is given out
    3. (1) or (2), depending on type of ore
    4. H2S is given out
    Show answer

    Answer: C. (1) or (2), depending on type of ore

    Calcination is a thermal decomposition process performed in the absence or limited supply of air. Its primary purpose is to drive off volatile substances like water (from hydrated ores) or carbon dioxide (from carbonate ores). For example, heating hydrated bauxite (Al2O3.nH2O) yields Al2O3 and H2O, while heating limestone (CaCO3) yields CaO and CO2.

  5. Which one of the following metals can be extracted using carbon as reducing agent ?

    Asked in: UPSC NDA 2 2023

    1. Zinc
    2. Silver
    3. Gold
    4. Aluminum
    Show answer

    Answer: A. Zinc

    Metals less reactive than carbon can be extracted from their oxides by reduction with carbon (smelting). In the reactivity series, carbon is more reactive than zinc, silver, and gold, but less reactive than aluminium. Therefore, oxides of zinc, silver, and gold can potentially be reduced by carbon, while aluminium oxide cannot.

  6. Manganese is extracted by heating manganese dioxide with aluminium powder. Which one of the following statements with regard to the reaction is correct?

    Asked in: UPSC CAPF 2021

    1. The reaction is exothermic.
    2. The reaction is endothermic.
    3. Manganese is produced as a solid.
    4. Manganese is more reactive than aluminium.
    Show answer

    Answer: A. The reaction is exothermic.

    Thermite reactions involve the reduction of a metal oxide by a more reactive metal (typically aluminium). The general form is Metal Oxide A + Metal B → Metal A + Oxide of Metal B, where Metal B is more reactive than Metal A. These reactions are characterized by their high exothermicity, often producing molten metal.

  7. Manganese is extracted from Manganese dioxide by reaction with Aluminium as described by the following unbalanced chemical equation : MnO₂(s) + Al (s) → Mn (l) + Al₂O₃ (s) The number of moles of Al (s) required to form one mole of Mn from its oxide is

    Asked in: UPSC CISF AC EXE 2020

    1. 1
    2. 0.75
    3. 1.33
    4. 2
    Show answer

    Answer: C. 1.33

    The question requires balancing the given chemical equation and then using stoichiometry to find the mole ratio between reactants and products. The ratio of Al to Mn in the balanced equation is 4:3.

  8. Which is the reducing agent in the thermit reaction carried out for repairing of the railway track?

    Asked in: WBPSC CS Prelims 2023

    1. Iron oxide
    2. Aluminium metal
    3. Aluminium oxide
    4. Iron metal
    Show answer

    Answer: B. Aluminium metal

    The thermit reaction typically involves the reaction between iron oxide (Fe₂O₃) and aluminium metal (Al) to produce molten iron and aluminium oxide (Al₂O₃). The balanced equation is Fe₂O₃ + 2 Al → 2 Fe + Al₂O₃. In this reaction, aluminium reduces iron oxide to iron by taking oxygen away from it. Therefore, aluminium is oxidized (gains oxygen) and acts as the reducing agent.

General principles of metallurgy: concentration, reduction, refining

  1. Which of the following statements are true for the reaction of Fe₂O₃ with aluminium? 1. It is known as the 'thermite reaction'. 2. The heat evolved is used for welding purpose. 3. Aluminium metal acts as an oxidizing agent. 4. Molten Fe and Al are formed at the end of the reaction. Select the correct answer using the code given below.

    Asked in: UPSC CDS 1 2023

    1. 1 and 2
    2. 1 and 3
    3. 2 and 4
    4. 1 and 4
    Show answer

    Answer: A. 1 and 2

    - Statement 1 is correct: This reaction is famously known as the thermite reaction. - Statement 2 is correct: The large amount of heat produced in the thermite reaction results in molten iron, which is used for welding broken railway tracks or cracked machine parts (thermite welding). - Statement 3 is incorrect: Aluminium acts as a reducing agent because it removes oxygen from Fe₂O₃. Iron(III) oxide (Fe₂O₃) acts as the oxidizing agent. - Statement 4 is incorrect: Molten iron (Fe) is formed at the end of the reaction. Aluminium is converted to aluminium oxide (Al₂O₃), not molten aluminium metal.

  2. Match the following: (a) Na and - (i) Obtained by electrolysis of K fused salt (b) Cu and - (ii) Occur only in native state Ag (c) Au and - (iii) Occur both native and Pt combined state (d) Na and - (iv) Reducing agent in metallurgy Ca (e) Al and - (v) Occur only in combined state. Mg

    Asked in: TNPSC CS Prelims 2015

    1. (a) – (v) (b) – (iii) (c) – (ii) (d) – (i) (e) – (iv)
    2. (a) – (iv) (b) – (i) (c) – (ii) (d) – (iii) (e) – (v)
    3. (a) – (ii) (b) – (iii) (c) – (v) (d) – (iv) (e) – (i)
    4. (a) – (iii) (b) – (ii) (c) – (i) (d) – (v) (e) – (iv)
    Show answer

    Answer: A. (a) – (v) (b) – (iii) (c) – (ii) (d) – (i) (e) – (iv)

    - Metals differ in their reactivity, which affects how they occur in nature and how they are extracted. - Highly reactive metals like Na, K, Ca, Al, Mg are usually found only in combined states (ores) and are often extracted by electrolysis of their fused salts or oxides. - Less reactive metals like Cu, Ag can be found in both native and combined states. - Very unreactive (noble) metals like Au, Pt are usually found only in the native state. - Reactive metals like Na, Ca, Al, Mg can act as reducing agents in metallurgy for less reactive metal oxides.

  3. Which one of the following catalysts is used for hydrogenation of vegetable oils ?

    Asked in: UPPSC Upper Mains 2010

    1. Zinc dust
    2. Nickel
    3. Platinum
    4. Copper
    Show answer

    Answer: B. Nickel

    Hydrogenation of vegetable oils, which converts liquid unsaturated fats into solid or semi-solid saturated fats, commonly uses Nickel as a catalyst.

  4. The iron-carbon diagram and TTT curve are determined under : - (5) Question not attempted

    Asked in: Assistant Eng. (Mechanical) Competitive Examination, 2023

    1. Equilibrium and non-equilibrium conditions respectively
    2. Non-equilibrium and equilibrium conditions respectively
    3. Equilibrium conditions for both
    4. Non-equilibrium conditions for both
    Show answer

    Answer: A. Equilibrium and non-equilibrium conditions respectively

    Phase diagrams represent equilibrium conditions, while transformation diagrams like TTT curves represent non-equilibrium transformations.

Important ores of common metals (e.g., iron, aluminum, copper, zinc, lead, mercury) and their chemical formulae

  1. The most important ore of aluminium is

    Asked in: BPSC Prelims Exam 67th Cancelled

    1. bauxite
    2. calamine
    3. calcite
    4. galena
    Show answer

    Answer: A. bauxite

    Bauxite is the primary commercial source of aluminium. It is a heterogeneous material typically composed of aluminium hydroxide minerals (like gibbsite, boehmite, and diaspore), along with impurities such as iron oxides, silicon dioxide, and titanium dioxide. Aluminium is extracted from bauxite using the Bayer process, followed by smelting via the Hall-Héroult process.

  2. Aluminium is manufactured from

    Asked in: UPSC CDS 1 2021

    1. Copper ore
    2. Bauxite ore
    3. Mica ore
    4. Manganese ore
    Show answer

    Answer: B. Bauxite ore

    Bauxite is the principal ore from which aluminium is extracted globally.

  3. Consider the following statements :

    Asked in: KPSC KAS Prelims 2015

    1. Pyrolusite is an ore of manganese.
    2. Galena is an ore of lead. Which of the above statements is/are correct ? Select the code for the correct answer from the options given below : A. A only B. B only
    3. Both A and B
    4. Neither A nor B
    Show answer

    Answer: C. Both A and B

    Statement A is correct: Pyrolusite (MnO₂) is the principal ore of manganese. Statement B is also correct: Galena (PbS) is the principal ore of lead. Both statements accurately identify the metals associated with the given ores.

  4. Cinnabar is an ore of which one of the following ?

    Asked in: UPSC NDA 2 2021

    1. Copper
    2. Zinc
    3. Mercury
    4. Manganese
    Show answer

    Answer: C. Mercury

    Cinnabar is the main ore from which mercury (Hg) is extracted. It is chemically represented as HgS.

  5. Which of the following is an ore of Iron?

    Asked in: OPSC CS Prelims 2017

    1. Siderite
    2. Malachite
    3. Bauxite
    4. Anglesite
    Show answer

    Answer: A. Siderite

    Siderite is an iron ore with the chemical formula FeCO₃ (iron(II) carbonate).

  6. Symbol of material used in conventional glass thermometers is

    Asked in: OPSC CS Prelims 2023

    1. Mg
    2. Hg
    3. Me
    4. Mn
    Show answer

    Answer: B. Hg

    - Conventional thermometers rely on the thermal expansion of a liquid. - Mercury (Hg) is a commonly used liquid in glass thermometers due to its high coefficient of thermal expansion, visibility, and non-wetting properties on glass.

  7. Consider the following pairs of metals and their ores : Metal Ore 1. Iron Siderite 2. Copper - Calamine 3. Zinc Sphalerite Which of the above mentioned pairs is/are not correctly matched ?

    Asked in: PPSC CS Prelims 2013

    1. 1 and 2
    2. Only 2
    3. 2 and 3
    4. Only 3
    Show answer

    Answer: B. Only 2

    - Iron ores include Hematite (Fe2O3), Magnetite (Fe3O4), Limonite (Fe2O3·nH2O), and Siderite (FeCO3). So, Iron-Siderite is correctly matched. - Copper ores include Chalcopyrite (CuFeS2), Cuprite (Cu2O), Malachite (Cu2CO3(OH)2), Azurite (Cu3(CO3)2(OH)2). Calamine (ZnCO3) is an ore of Zinc. So, Copper-Calamine is incorrectly matched. - Zinc ores include Sphalerite (ZnS) and Calamine (ZnCO3). So, Zinc-Sphalerite is correctly matched.

  8. Which of the following is halide ore?

    Asked in: TNPSC CS Prelims 2014

    1. Dolomite
    2. Rock salt
    3. Bauxite
    4. Galena
    Show answer

    Answer: B. Rock salt

    A halide ore is an ore from which a metal can be extracted economically, where the metal is present in the form of a halide compound (containing a halogen element like Chlorine, Fluorine, Bromine, or Iodine). Let's examine the options: A) Dolomite (CaMg(CO₃)₂): This is a carbonate ore. B) Rock salt (NaCl): This is Sodium Chloride, a halide (chloride) compound of Sodium. It is an important source of sodium. C) Bauxite (Al₂O₃·nH₂O): This is an oxide ore of Aluminium. D) Galena (PbS): This is a sulfide ore of Lead.

Physical properties of metals (luster, malleability, ductility, conductivity, density, melting/boiling points)

  1. The heaviest metal among the following is

    Asked in: BPSC Prelims Exam 63rd

    1. gold
    2. silver
    3. mercury
    4. platinum
    Show answer

    Answer: D. platinum

    Density is a measure of mass per unit volume. Among the given options, Platinum is the densest metal.

  2. Which one of the following alkali metals has lowest melting point ?

    Asked in: UPSC NDA 1 2018

    1. Sodium
    2. Potassium
    3. Rubidium
    4. Caesium
    Show answer

    Answer: D. Caesium

    Melting points of alkali metals decrease down the group due to decreasing metallic bond strength as atomic size increases.

  3. Which one of the following could be the melting point of iron ?

    Asked in: UPSC NDA 1 2019

    1. 25°C
    2. 37°C
    3. 500°C
    4. 1500°C
    Show answer

    Answer: D. 1500°C

    The melting point of pure iron is approximately 1538°C (2800°F). The melting points of common metals are relatively high compared to typical ambient temperatures.

  4. The alkali metals have relatively low melting point. Which one of the following alkali metals is expected to have the highest melting point?

    Asked in: UPSC NDA 2 2015

    1. Li
    2. Na
    3. K
    4. Rb
    Show answer

    Answer: A. Li

    Melting points of alkali metals decrease down the group (from Li to Fr) due to decreasing metallic bond strength.

  5. Which one of the following metals is liquid at ordinary temperature?

    Asked in: UPPSC Upper Mains 2014

    1. Lead
    2. Nickel
    3. Mercury
    4. Tin
    Show answer

    Answer: C. Mercury

    Mercury has a significantly low melting point compared to most other metals, causing it to be liquid at typical room temperatures.

  6. Which of the following metals as the lowest melting point?

    Asked in: APPSC Draughtman 2008

    1. Lithium
    2. Sodium
    3. Potassium
    4. Lid
    Show answer

    Answer: C. Potassium

    Among the given options, Potassium (K) has the lowest melting point. The approximate melting points are: Lithium (Li) ~180.5 °C, Sodium (Na) ~327.5 °C (assuming "Lid" is a typo for Lead).

  7. The metal which can be easily cut with a knife —

    Asked in: WBCS Main Paper 4 2021

    1. Paper
    2. Silver
    3. Sodium
    4. Gold
    Show answer

    Answer: C. Sodium

    Alkali metals (Group 1 of the periodic table, excluding hydrogen) like Lithium, Sodium, Potassium, etc., are known for being very soft, highly reactive, and having low melting points compared to other metals. Their softness increases down the group.

  8. Metallic bond is not characterised by

    Asked in: WBCS Main Paper 4 2022

    1. Opacity
    2. Ductility
    3. High conductivity
    4. Directionality
    Show answer

    Answer: D. Directionality

    - Metallic bonds are considered non-directional because the attraction between the positive ions and the delocalized electrons is spread throughout the crystal structure. - Opacity, ductility (ability to be drawn into wires), and high conductivity (electrical and thermal) are characteristic properties of metals resulting from the structure and the presence of mobile electrons.

Reactivity series of metals and its applications

  1. Which one of the following chemical reactions is not feasible?

    Asked in: UPSC CDS 1 2020

    1. Fe + CuSO₄ → FeSO₄ + Cu
    2. Zn + CuSO₄ → ZnSO₄ + Cu
    3. Cu + PbCl₂ → CuCl₂ + Pb
    4. Mg + CuSO₄ → MgSO₄ + Cu
    Show answer

    Answer: C. Cu + PbCl₂ → CuCl₂ + Pb

    Comparing the reactivity of the metals involved: Magnesium (Mg) > Zinc (Zn) > Iron (Fe) > Lead (Pb) > Copper (Cu). - A) Fe + CuSO₄: Fe is more reactive than Cu. Fe displaces Cu. Feasible. - B) Zn + CuSO₄: Zn is more reactive than Cu. Zn displaces Cu. Feasible. - C) Cu + PbCl₂: Cu is less reactive than Pb. Cu cannot displace Pb. Not feasible. - D) Mg + CuSO₄: Mg is more reactive than Cu. Mg displaces Cu. Feasible.

  2. Which one of the following is the correct order of reactivity of Mg, Al, Zn and Fe with HCl?

    Asked in: UPSC CDS 1 2024

    1. Mg > Al > Zn > Fe
    2. Mg > Al > Fe > Zn
    3. Zn > Fe > Mg > Al
    4. Fe > Al > Zn > Mg
    Show answer

    Answer: A. Mg > Al > Zn > Fe

    The standard reactivity series (based on standard electrode potentials) places these metals in the order of decreasing reactivity as Mg > Al > Zn > Fe > H. Therefore, their reactivity with HCl follows the same order: Mg > Al > Zn > Fe.

  3. Which one of the following is the correct reactivity order of metals reacting with dilute HCl?

    Asked in: UPSC CDS 2 2021

    1. Mg > Al > Zn > Fe
    2. Mg < Al < Zn < Fe
    3. Mg > Zn > Fe > Al
    4. Fe > Mg > Al > Zn
    Show answer

    Answer: A. Mg > Al > Zn > Fe

    The reactivity series of metals is determined by their tendency to lose electrons and form positive ions. Metals higher in the series are more reactive and can displace less reactive metals (or hydrogen from acids) from their compounds. The order of reactivity of these common metals is Mg > Al > Zn > Fe.

  4. Which one of the following is the correct order of relative reactivities of metals Ca, Al, Hg and Au?

    Asked in: UPSC Geoscientist 2021

    1. Ca > Al > Hg > Au
    2. Au > Hg > Al > Ca
    3. Al > Ca > Hg > Au
    4. Ca > Al > Au > Hg
    Show answer

    Answer: A. Ca > Al > Hg > Au

    The reactivity series orders metals from most reactive (top) to least reactive (bottom) based on their tendency to lose electrons. Ca is higher than Al, which is higher than Hg, which is higher than Au.

  5. Which one of the following is the correct arrangement of metals in the decreasing order of their reactivity ?

    Asked in: UPSC NDA 1 2023

    1. Iron, Sodium, Silver, Copper
    2. Silver, Copper, Iron, Sodium
    3. Sodium, Copper, Silver, Iron
    4. Sodium, Iron, Copper, Silver
    Show answer

    Answer: D. Sodium, Iron, Copper, Silver

    - Metals are ranked by their reactivity (tendency to lose electrons). - The reactivity series is K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au > Pt. - The metals in the options are Sodium (Na), Iron (Fe), Copper (Cu), Silver (Ag). - Their order in the series is Na > Fe > Cu > Ag.

  6. Which one of the following represents the correct order of electron releasing tendency of metals ?

    Asked in: UPSC NDA 2 2019

    1. Zn > Cu > Ag
    2. Ag > Cu > Zn
    3. Cu > Zn > Ag
    4. Cu > Ag > Zn
    Show answer

    Answer: A. Zn > Cu > Ag

    The electron releasing tendency of metals is determined by their position in the electrochemical series or reactivity series. Metals higher in the series have a greater tendency to lose electrons and act as reducing agents, thus having higher electron releasing tendency.

  7. Which one of the following is the highest reactive metal ?

    Asked in: UKPSC CS Prelims 2024

    1. Sodium
    2. Potassium
    3. Calcium
    4. Iron
    Show answer

    Answer: B. Potassium

    The reactivity of metals is determined by their tendency to lose electrons and form positive ions. This is often represented by the activity series or reactivity series of metals. The general order of reactivity for the given metals is: Potassium (K) > Sodium (Na) > Calcium (Ca) > Iron (Fe). Potassium is an alkali metal and is highly reactive, reacting vigorously with water and air. Sodium is also an alkali metal, less reactive than Potassium but still very reactive. Calcium is an alkaline earth metal, less reactive than alkali metals. Iron is a transition metal and is considerably less reactive than Calcium, Sodium, and Potassium.

  8. Which one among the following is the most reactive metal?

    Asked in: UPSC CISF AC EXE 2023

    1. Na
    2. K
    3. Ca
    4. Mg
    Show answer

    Answer: B. K

    - Reactivity of metals is related to their tendency to lose electrons (become oxidized). - Alkali metals (Group 1) are generally more reactive than alkaline earth metals (Group 2). - Within alkali metals, reactivity increases down the group. - Within alkaline earth metals, reactivity generally increases down the group (though sometimes variations occur, but the general trend holds for Ca vs Mg). - The order of reactivity for the given options is approximately K > Na > Ca > Mg.

Refining of metals (electrolytic refining, zone refining, liquation, distillation, vapor phase refining)

  1. When mild steel is heated to a high temperature and suddenly cooled in water, it becomes hard and brittle. The process is called :

    Asked in: HPPSC HPAS Prelims 2011

    1. Hardening
    2. Annealing
    3. Quenching
    4. Tempering
    Show answer

    Answer: C. Quenching

    Quenching is the rapid cooling of a heated metal to achieve hardening.

  2. The purest form of iron is

    Asked in: MPSC CS Prelims 2012

    1. Cast iron
    2. Wrought iron
    3. Steel
    4. Stainless Steel
    Show answer

    Answer: B. Wrought iron

    Wrought iron is considered the purest form of commercially available iron among the options listed. It is a highly refined iron with a very low carbon content (typically less than 0.08%) and contains dispersed slag inclusions, which are products of the manufacturing process. This low carbon content distinguishes it from cast iron and steel.

  3. In electrolytic refining of copper, the electrolyte is a solution of

    Asked in: UPSC NDA 1 2021

    1. acidified copper chloride.
    2. acidified copper sulphate.
    3. potassium chloride.
    4. sodium sulphate.
    Show answer

    Answer: B. acidified copper sulphate.

    In the process of electrolytic refining, impure copper acts as the anode and dissolves as Cu²⁺ ions, while pure copper acts as the cathode where Cu²⁺ ions from the electrolyte are deposited. The electrolyte needs to contain Cu²⁺ ions, which is achieved by using a solution of copper sulfate (CuSO₄). Sulfuric acid (H₂SO₄) is added to the copper sulfate solution to increase its conductivity and prevent the precipitation of copper hydroxide.

Uses of common metals and their compounds in industries and daily life

  1. Which of the following is the main ingredient of cement?

    Asked in: BPSC Prelims Exam 67th Cancelled

    1. Limestone
    2. Silica clay
    3. Gypsum
    4. Ash
    Show answer

    Answer: A. Limestone

    Portland cement clinker, the binding agent in most cements, is produced by heating a mixture of raw materials containing primarily calcium carbonate (from limestone) and aluminosilicates (from clay or shale) in a kiln. Limestone makes up the largest proportion of the raw mix, providing the necessary calcium oxide.

  2. 'Plaster of Paris' is made up of

    Asked in: CGPSC Prelims Exam 2019

    1. Marble
    2. Cement
    3. Gypsum
    4. Limestone
    Show answer

    Answer: C. Gypsum

    Plaster of Paris (chemically calcium sulfate hemihydrate, CaSO₄·½H₂O) is produced by heating gypsum (calcium sulfate dihydrate, CaSO₄·2H₂O) to about 150°C (302°F). This process removes about three-quarters of the water molecules from the gypsum.

  3. Which of the following metals are used as catalyst in the Catalytic converters to eliminate poisonous gases ?

    Asked in: CGPSC Prelims Exam 2023

    1. Sodium
    2. Thorium
    3. Rhodium
    4. None of the above
    Show answer

    Answer: C. Rhodium

    Catalytic converters commonly use precious metals such as Platinum, Palladium, and Rhodium as catalysts to convert harmful pollutants like carbon monoxide, nitrogen oxides, and unburnt hydrocarbons into less harmful substances such as carbon dioxide, nitrogen, and water.

  4. Which one of the following statements regarding gold is not correct?

    Asked in: UPSC Geoscientist 2022

    1. 24 karat gold is very soft.
    2. 22 karat gold is generally used to make orna‐ ments.
    3. 22 karat gold contains 22 parts of pure gold and 2 parts of iron to make it hard.
    4. 18 karat gold comprises of 75% gold mixed with 25% of copper or silver to make it hard.
    Show answer

    Answer: C. 22 karat gold contains 22 parts of pure gold and 2 parts of iron to make it hard.

    Karat is a measure of gold purity. Pure gold (24 karat) is soft. Gold for jewelry is typically alloyed with other metals like copper, silver, or zinc to increase its hardness and durability.

  5. Which one of the following is non-toxic ?

    Asked in: HPPSC HPAS Prelims 2010

    1. Cadmium
    2. Mercury
    3. Lead
    4. Sodium
    Show answer

    Answer: D. Sodium

    Cadmium, Mercury, and Lead are well-known heavy metals that are highly toxic to humans and the environment, even at low concentrations. Sodium, on the other hand, is an essential electrolyte for human life and, in its common forms (like sodium chloride), is not considered toxic in the same way as the heavy metals listed, although excessive intake can be detrimental to health.

  6. Which is the secondmost abundant metal in the earth's crust?

    Asked in: JPSC CS Prelims 2011

    1. Iron
    2. Aluminium
    3. Copper
    4. Zinc
    Show answer

    Answer: A. Iron

    The abundance of elements in the Earth's crust (by mass) is approximately: Oxygen (46.6%), Silicon nesium (2.1%). Aluminium is the most abundant metal, and Iron is the second most abundant metal.

  7. Which of the following metals occur in free and native state ?

    Asked in: MPSC CS Prelims 2012

    1. Mg, Ca
    2. Ni, Zn
    3. Fe, Al
    4. Pt, Au
    Show answer

    Answer: D. Pt, Au

    Noble metals like Platinum (Pt) and Gold (Au) are very unreactive. Due to their low reactivity, they are often found in nature in their elemental form (native state) rather than in compounds like oxides, sulfides, or carbonates.

  8. Addition of gypsum to cement:

    Asked in: UPSC NDA 2 2015

    1. reduces setting time of cement
    2. produces very light colour cement
    3. increases setting time of cement
    4. shining surface is formed
    Show answer

    Answer: C. increases setting time of cement

    - Cement clinker, when mixed with water, undergoes rapid hydration reactions, especially involving tricalcium aluminate (C₃A), which can lead to flash setting (very rapid hardening). - Gypsum (calcium sulfate dihydrate) is added to the cement clinker during grinding to act as a retarder. - Gypsum reacts with C₃A to form ettringite, which precipitates on the surface of the C₃A particles, forming a barrier that slows down the rapid hydration of C₃A. - This allows sufficient time for the cement paste or concrete to be mixed, transported, placed, and finished before it begins to harden.