Inorganic Chemistry is part of Chemistry. Below are notes on 12 sub-topics, followed by practice MCQs from State PSC and UPSC papers.
Acid-Base Chemistry and Non-aqueous Solvents
- Standard Hydrogen Electrode (SHE): Its standard electrode potential is defined as 0.00 V at all temperatures. Its absolute electrode potential is not zero.
- Primary Standard: A substance of high purity, stable, non-hygroscopic, high molecular/ equivalent weight, and readily available to prepare a solution of exact concentration.
- Examples of Primary Standards: Potassium dichromate (K₂Cr₂O₇), Oxalic acid, Anhydrous sodium carbonate (Na₂CO₃), Silver nitrate (AgNO₃).
- Secondary Standards: Substances like Potassium permanganate (KMnO₄), Sodium thiosulphate (Na₂S₂O₃), and EDTA, whose solutions must be standardized against a primary standard.
- Hard and Soft Acid-Base (HSAB) Principle: Hard acids prefer to bond with hard bases, and soft acids prefer to bond with soft bases.
- Hard Bases: Characterized by small size, high electronegativity, and low polarizability of the donor atom (e.g., O, N, F). Examples: Fluoride (F⁻), Hydroxide (OH⁻), Water (H₂O), Ammonia (NH₃), Carbonate (CO₃²⁻), Nitrate (NO₃⁻), Carboxylate (RCOO⁻).
- Soft Bases: Characterized by large size, low electronegativity, and high polarizability of the donor atom (e.g., P, S, I). Examples: Iodide (I⁻), Thiocyanate (SCN⁻, S-bonded), Trialkylphosphines (R₃P), Carbon monoxide (CO), Cyanide (CN⁻), Hydride (H⁻).
- Aqua Regia: A highly corrosive mixture of concentrated nitric acid (HNO₃) and concentrated hydrochloric acid (HCl).
- Aqua Regia Ratio: Typically prepared with 1 part concentrated HNO₃ to 3 parts concentrated HCl by volume.
- Aqua Regia Properties: It is highly acidic (pH < 7) and appears yellow/orange due to the formation of volatile products like nitrosyl chloride (NOCl) and chlorine gas (Cl₂).
- Aqua Regia Function: Capable of dissolving noble metals such as gold (Au) and platinum (Pt) by a synergistic action of oxidizing nitrate and complexing chloride ions (forming AuCl₄⁻ or PtCl₆²⁻).
Atomic Structure and Periodicity
- Antoine Lavoisier is regarded as the Father of Modern Chemistry.
- Elements are classified as Metals, Nonmetals, and Metalloids. "Gases" is a state of matter, not an element type.
- The year 2019 was designated the International Year of the Periodic Table of Chemical Elements, celebrating its 150th anniversary.
- There are 94 naturally occurring elements. Approximately 100 different chemical elements exist on Earth.
- Laws of Chemical Combination:
- Avogadro's Law: Equal volumes of all gases at the same temperature and pressure contain equal numbers of molecules.
- Law of Multiple Proportions: If two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element are in simple wholenumber ratios.
- Law of Conservation of Mass: Matter can neither be created nor destroyed.
- Law of Definite Proportions: A given compound always contains exactly the same proportion of elements by weight.
- To find moles: Moles = Mass (g) / Molar Mass (g/mol). For 72.06 g of carbon (molar mass ≈ 12.01 g/mol), it's approximately 6 moles.
- Henry Moseley developed the Modern Periodic Table, which is based on atomic number. Dmitri Mendeleev developed the first widely accepted periodic table based on atomic mass.
- For isoelectronic species (e.g., O²⁻, F⁻, Na⁺, Mg²⁺), ionic radii decrease with increasing nuclear charge. The correct increasing order of ionic radii is Mg²⁺ < Na⁺ < F⁻ < O²⁻.
- Electron Gain Enthalpy (EGE):
- Generally becomes more negative across a period and less negative down a group.
- Chlorine (Cl) has the most negative EGE among F, Cl, P, S. Fluorine (F) has a less negative EGE than Cl due to its small size causing inter-electronic repulsion.
- Among P, S, Cl, F, Cl has the most negative EGE, and Phosphorus (P) has the least negative EGE.
- Frederick Sanger won the Nobel Prize in Chemistry twice (1958 and 1980).
- The Nobel Prize in Chemistry in 2018 was awarded to Frances Arnold, George P. Smith, and Greg Winter for their work on directed evolution.
- Branches of Chemistry and their areas:
- Biochemistry: Chemical processes in living organisms.
- Material Chemistry: Solid state chemistry and polymer chemistry.
- Physical Chemistry: Physical principles of chemical processes.
- Analytical Chemistry: Detection and determination of chemicals and compounds.
- The number of molecules is directly proportional to the number of moles.
moles), 42 g of N₂ (1.5 moles) contain the same number of molecules.
- 2 g of Carbon (approx. 0.166 moles) contains a different number of molecules.
- Highest Valency of elements:
- Sulfur (S): Six
- Phosphorus (P): Five
- Lead (Pb): Four
- Silver (Ag): Two (though +1 is more common)
- Cesium (Cs) is the strongest electropositive element among the options given due to its large atomic size and low ionization energy.
- According to Newlands' Law of Octaves, Beryllium (Be) resembles Magnesium (Mg).
- Periodic Table Trends:
- Ionization potential (Ionization energy) generally increases along a period and decreases down a group.
- In a group, electron affinity generally decreases as atomic weight (and size) increases.
- In a given period, electronegativity generally increases as the atomic number increases.
- When going from left to right across the periods of the Periodic Table:
- Elements become less metallic in nature.
- The number of valence electrons increases.
- The atoms lose their electrons less easily (ionization energy increases).
- The oxides become more acidic.
- Representative Elements (Main Group Elements) belong to Group 1, Group 2, and Group 13 to 18.
- Incorrect statement: Chlorine has more negative electron gain enthalpy than Fluorine.
- Helium (He) has the highest first ionization enthalpy in the periodic table.
- In any period, alkali metals (Group 1) have the highest atomic radius.
- Mercury (Hg) and Bromine (Br) are liquids at room temperature.
- The ratio by mass of carbon to oxygen in carbon dioxide (CO₂) is 12 : (2 16) = 12 : 32 = 3 : 8.
- To determine which option weighs highest, calculate the mass (moles × molar mass) for each:
- 0.2 mole of sucrose (C₁₂H₂₂O₁₁, 342 g/ mol) = 68.4 g
- 2 moles of CO₂ (44 g/mol) = 88 g
- 2 moles of CaCO₃ (100 g/mol) = 200 g
- 10 moles of H₂O (18 g/mol) = 180 g
- Thus, 2 moles of CaCO₃ weighs the highest.
- The ratio of mass of magnesium to sulfur in magnesium sulphide (MgS) is 24 : 32 = 3 : 4.
- Acidic nature of oxides increases from left to right across a period.
Bioinorganic Chemistry
- Arsenic, Chromium, and Mercury are highly toxic trace elements.
- Copper is an essential trace element and is less toxic compared to Arsenic, Chromium, and Mercury.
- Moungi G. Bawendi, Louis E. Brus, and Alexei Ekimov were awarded the Nobel Prize in Chemistry in 2023.
- Calcium (Ca) is an essential element for blood clotting.
Catalysis by Inorganic Compounds
- Green Chemistry: Aims to design chemical products and processes that reduce or eliminate the use and generation of hazardous substances, focusing on non-toxic reagents/ solvents and environmentally-friendly products.
- Positive Catalyst: Increases the rate of a chemical reaction by providing an alternate reaction pathway with lower activation energy.
- Negative Catalyst (Inhibitor): Decreases the rate of a chemical reaction.
- Manganese Dioxide (MnO₂): Acts as a positive catalyst in the thermal decomposition of potassium chlorate (KClO₃), significantly increasing the rate of oxygen gas (O₂) production. (e.g., 2KClO₃(s) --(MnO₂, heat)--> 2KCl(s) + 3O₂(g)).
- Thermite Reaction: A highly exothermic redox reaction involving a metal oxide (e.g., Fe₂O₃) and a more reactive metal (e.g., Al) as the reducing agent.
- Thermite Reaction Example: Fe₂O₃(s) + 2Al(s) → 2Fe(s) + Al₂O₃(s).
- Characteristics of Thermite Reaction: It is a displacement reaction; Fe₂O₃ acts as the oxidizing agent (Fe is reduced); it is highly exothermic, releasing a large amount of heat.
- Applications of Thermite Reaction: Used in thermite welding for joining metal parts, such as railway tracks, due to the high temperature produced.
- Green Oxidizing Agent: Aqueous Hydrogen Peroxide (H₂O₂) is preferred in green chemistry for clean oxidation processes as its only by-product is water, unlike toxic oxidants like K₂Cr₂O₇.
Chemical Bonding and Molecular Structure
- Chemical Bonds: Electrostatic forces holding atoms together in molecules or crystals.
- Types of Bonds:
- Ionic Bond: Formed by complete transfer of electrons, typically between a metal and a non-metal (e.g., K₂S, CaO, Na₃N, ZnS).
- Ionic compounds are generally soluble in polar solvents (like water) and insoluble in nonpolar/less polar organic solvents (like alcohol).
- Ionic compounds in solid state are poor conductors of electricity due to fixed ion positions; they conduct in molten state or solution.
- Ionic character increases with greater electronegativity difference and according to Fajan's rules (larger cation, smaller anion, lower charge -> less covalent character, i.e., more ionic). K₂S has high ionic character compared to BeF₂ (due to Be's small size and high polarizing power).
- Covalent Bond: Formed by sharing of electrons, typically between two nonmetals (e.g., NCl₃, SiO₂, SiC). Silicon carbide (SiC) is a superhard material due to strong covalent network bonds.
- Metallic Bond: Present in metals, involves delocalized electrons.
- Compounds vs. Mixtures:
- Compound: Has a fixed composition; particles contain two or more elements chemically combined in a definite ratio; constituents cannot be separated by simple physical methods (e.g., Sugar, Aluminium hydroxide, Sodium carbonate).
- Mixture: Has variable composition; constituents are not chemically combined; can be separated by simple physical methods (e.g., Air, Milk, Tea).
- Molecular Formula & Moles:
- To write formula of ionic compounds: Use valencies (e.g., Ammonium Carbonate: NH₄⁺ valency +1, CO₃²⁻ valency -2 ⇒ (NH₄)₂CO₃).
- Number of moles of an atom in a compound: 1 mole of Al(OH)₃ contains 3 moles of hydrogen atoms.
- Formula Mass: Sum of atomic masses of all atoms in a formula unit (e.g., Na₂CO₃ = (223) + (112) + (316) = 106 u).
- Mass Percent: (Mass of element / Total molar mass) 100. For C₆H₁₂O₄, mass % of C is six times mass % of H (72:12).
- VSEPR Theory (Valence Shell Electron Pair Repulsion Theory):
- Repulsive interaction order: Lone pair-lone pair (l.p. - l.p.) > Lone pairbond pair (l.p. - b.p.) > Bond pairbond pair (b.p. - b.p.).
- Predicting Geometry & Hybridization:
- Steric Number 2: sp hybridization, Linear geometry (e.g., BeCl₂, XeF₂).
- Steric Number 3: sp² hybridization, Trigonal planar geometry (e.g., BF₃, SO₃).
- Steric Number 4: sp³ hybridization, Tetrahedral electron geometry.
- 4 bp, 0 lp: Tetrahedral molecular geometry, 109.5° bond angle (e.g., CH₄, CF₄).
- 3 bp, 1 lp: Pyramidal molecular geometry (e.g., NH₃).
- Steric Number 5: sp³d hybridization, Trigonal bipyramidal electron geometry.
- 5 bp, 0 lp: Trigonal bipyramidal molecular geometry, contains 90° and 120° angles (e.g., PCl₅).
- 4 bp, 1 lp: See-saw molecular geometry (e.g., SF₄).
- 2 bp, 3 lp: Linear molecular geometry (e.g., XeF₂).
- Steric Number 6: sp³d² hybridization, Octahedral electron geometry.
- 6 bp, 0 lp: Octahedral molecular geometry, contains 90° and 180° angles (e.g., SF₆, SiF₆²⁻).
- 4 bp, 2 lp: Square planar molecular geometry (e.g., XeF₄).
- Dipole Moment:
- A measure of polarity of a molecule, it's a vector quantity.
- Depends on bond polarity and molecular geometry. If bond dipoles cancel due to symmetry, net dipole moment is zero (e.g., BF₃, CH₄).
- NH₃ has a significant dipole moment (1.47 D) due to its pyramidal shape and lone pair contributing to the dipole. NF₃ has a smaller dipole moment (0.23 D) because the bond dipoles partially oppose the lone pair dipole.
- Molecular Orbital (MO) Theory:
- Bond Order: 0.5 (Number of electrons in bonding MOs - Number of electrons in antibonding MOs).
- For CO (14 electrons): Bond Order = 3.
- Paramagnetism/Diamagnetism:
- Paramagnetic: Contains unpaired electrons (e.g., O₂).
- Diamagnetic: All electrons are paired (e.g., H₂, N₂).
- Electrophiles: Electron-deficient species that "love" electrons; typically positively charged or have empty orbitals (e.g., Cl⁺, NO₂⁺, AlCl₃, SO₃, :CH₂ (carbene)).
Chemistry of Main Group Elements (s-block and p-block)
- Quartz crystals in clocks are silicon dioxide (SiO₂).
- Nitrous oxide (N₂O) is known as laughing gas.
- Quicklime is calcium oxide (CaO).
- When lead nitrate [Pb(NO₃)₂] is heated, brown fumes of nitrogen dioxide (NO₂) are emitted (Pb(NO₃)₂ → PbO + NO₂ + O₂).
- Quicklime (CaO) is used for white-washing walls.
- The solution of slaked lime (Ca(OH)₂) is used for whitewashing.
- Slaked lime (Ca(OH)₂) reacts slowly with CO₂ in air to form a thin layer of CaCO₃ on walls.
- Calcium hydroxide is called 'slaked lime' and is an inorganic compound.
- The reaction CaO(s) + H₂O(l) → Ca(OH)₂(aq) is exothermic and produces slaked lime.
- Aluminum oxide (Al₂O₃) is an amphoteric oxide.
- Caustic soda (NaOH) is used for degumming raw material in paper manufacturing.
- Lithium (Li) does not form solid hydrogen carbonate.
- Magnesium (Mg) traps the energy of sunlight in photosynthesis (as part of chlorophyll).
- Calcium (Ca) is involved in the control of muscle contraction.
- Strontium (Sr) gives a red colour to flame in flame tests.
- Barium (Ba) sulphate compounds (BaSO₄) are used in medicine to examine the alimentary canal of a patient (barium meal).
- The main constituent of pearl is calcium carbonate (CaCO₃).
- A mixture of sodium chloride (NaCl) and ammonium chloride (NH₄Cl) can be separated by sublimation (NH₄Cl sublimes).
- Bromine (Br₂) and mercury (Hg) are elements that are liquid at room temperature and standard pressure.
- Calcium chloride (CaCl₂) is used as a drying agent in guard tubes for the preparation of HCl gas.
- Potassium nitrate (KNO₃) is used as a fertilizer, in medicine, and in making gunpowder. It is also used as a preservative for meat products.
- Hydrogen has three isotopes: protium, deuterium, and tritium.
- Helium (He) is not commonly used in electric bulbs; Argon (Ar) is.
- Oxygen (O₂) is used to burn fuel (as an oxidizer) in rocket engines in spacecraft.
- Nitrogen (N₂) can be used in gaseous form to replace air in food packaging to prevent spoilage.
- Vermillion is chemically Mercury(II) Sulphide (HgS).
- Washing soda is sodium carbonate (Na₂CO₃).
- Sodium (Na) exhibits singular valency (+1).
- Bleaching powder (CaOCl₂) is used for disinfecting drinking water.
- Baking soda (NaHCO₃) is an ingredient in antacids.
- Washing soda (Na₂CO₃) is used for the removal of permanent hardness of water.
- Plaster of Paris (CaSO₄·½H₂O) is used for making toys and casts.
- s-block and p-block elements are together called 'Representative elements'.
- Clean, dry air contains approximately
volume.
- Crookes glass contains cerium oxide and can cut off ultraviolet rays.
- Plaster of Paris (CaSO₄·½H₂O) is obtained by heating gypsum (CaSO₄·2H₂O).
- Sodium carbonate (Na₂CO₃) is not an important constituent of baking powder; sodium bicarbonate (NaHCO₃) is.
- Bleaching powder (CaOCl₂) acts as an oxidising agent.
- Blue vitriol is copper(II) sulfate pentahydrate (CuSO₄·5H₂O) and contains five water molecules, not ten.
- Sodium hydroxide (NaOH) is produced by passing electricity through an aqueous solution of sodium chloride (brine electrolysis, Chlor-alkali process).
- Baking soda (NaHCO₃) is used in fire extinguishers (to produce CO₂).
- Quicklime (CaO) is used in the manufacture of glass (as a flux).
- Gypsum (CaSO₄·2H₂O) is used in the manufacture of Plaster of Paris.
- The electrolytes used in a dry cell are ammonium chloride (NH₄Cl) and zinc chloride (ZnCl₂).
- Dry ice is solid carbon dioxide (CO₂).
- The main raw materials for cement manufacturing are lime (CaO), silica (SiO₂), and alumina (Al₂O₃).
- Sodium thiosulphate (Na₂S₂O₃) is the chemical used as a fixer/developer in photography and as an antichlor.
- Sodium oxide (Na₂O) dissolves in water.
- Gypsum (CaSO₄·2H₂O) is not used as a raw material in the manufacture of glass. Soda, alumina, borax, and silica are.
- Silica (SiO₂) is not typically a pigment; zinc oxide, chalk, and white lead are pigments.
- Airbags work by the rapid conversion of sodium azide (NaN₃) into nitrogen gas (N₂).
- Borax (Na₂B₄O₇·10H₂O) is composed of Sodium, Boron, Oxygen, and Hydrogen.
- Magnesium oxide (MgO) typically has the highest melting point among Na₂O, MgO, Fe₂O₃, CuO due to strong ionic bonding and smaller ion size.
- Combination of one volume of nitrogen with three volumes of hydrogen produces two volumes of ammonia (N₂ + 3H₂ → 2NH₃).
- The reaction 3Cu + 8HNO₃ (dilute) → 3Cu(NO₃)₂ + 4H₂O + 2NO gives nitric oxide (NO) gas.
- The chemical formula of gypsum is CaSO₄·2H₂O.
- Chalk and marble are different forms of calcium carbonate (CaCO₃).
- Passing CO₂ gas through limewater (Ca(OH)₂) produces a white precipitate of calcium carbonate (CaCO₃).
- The chemical formula of Plaster of Paris is CaSO₄·½H₂O.
- The nitride anion (N³⁻) has a valency of –3.
- Hydrogen sulphide (H₂S) is an inorganic gaseous pollutant of air.
- Mg₂C₃ on hydrolysis gives propyne (CH₃C≡CH), not acetylene.
- Be₂C on hydrolysis gives methane (CH₄).
- Al₄C₃ on hydrolysis gives methane (CH₄), not allylene (propyne).
- Indian Salt Petre is potassium nitrate (KNO₃).
- Sulphur dioxide (SO₂) acts as both a reducing and an oxidizing agent.
- Silver bromide (AgBr) is used in photography, not for artificial photosynthesis.
- Silver iodide (AgI) is used for artificial rain.
- Milk of magnesia (Mg(OH)₂) is an antacid.
- The major active component in the water extract of ash from burning banana plants (a substitute for soda) is potassium carbonate (K₂CO₃).
- Arsenic present in groundwater can be partially removed along with iron by precipitation/coagulation methods if iron is also present.
- Urea is white.
- Hydrous copper sulphate (CuSO₄·5H₂O, blue vitriol) is blue.
- Lead sulphide (PbS) is black.
- Potassium permanganate (KMnO₄) is pinkish purple.
- Iron sulphate (FeSO₄·7H₂O) and zinc sulphate (ZnSO₄·7H₂O) crystals have the same number of water of crystallization (seven). Copper sulphate (CuSO₄·5H₂O) has five.
- Bleaching powder is prepared by the action of chlorine on dry slaked lime [Ca(OH)₂].
- Bleaching powder (CaOCl₂) acts as an oxidizing agent, not a reducing agent.
- Bleaching powder is also known as chlorinated lime and is used for disinfecting drinking water.
- Quartz contains Silicon (Si).
- Sodium hexametaphosphate (Na₆P₆O₁₈, Calgon) is used for water softening.
- If the formula of a sodium salt is Na₂X (X has -2 valency), then the formula of its aluminium salt (Al has +3 valency) would be Al₂X₃.
- Copper oxide (CuO), Potassium oxide (K₂O), and Calcium oxide (CaO) are basic oxides and do not usually react (dissolve or form complexes) with sodium hydroxide (NaOH). Aluminium oxide (Al₂O₃) is amphoteric and reacts with NaOH.
- Borax is prepared from sodium carbonate and boric acid/boron minerals.
- Carbon dioxide (CO₂) is an acidic oxide, not a basic oxide.
- The gas that turns limewater milky is carbon dioxide (CO₂).
- Lithium (Li) forms compounds with pronounced covalent character due to its small size and high charge density.
- Sodium chlorate (NaClO₃) is used in the match industry.
- Atmospheric air is approximately 21% oxygen and 78% nitrogen.
- Hydrofluoric acid (HF) reacts with glass (SiO₂) and cannot be kept in glass vessels.
- Plaster of Paris is produced by heating Gypsum.
- Limestone is the main ingredient in cement.
- Potassium permanganate (KMnO₄) is used to purify water because it is an oxidizing agent.
- When potassium iodide (KI) solution is added to a solution of lead nitrate (Pb(NO₃)₂), a yellow precipitate of lead iodide (PbI₂) is formed.
- Hypo solution used in photography is an aqueous solution of sodium thiosulphate (Na₂S₂O₃).
- Silver iodide (AgI) is used for producing artificial rain.
- Ozone (O₃), chlorine dioxide (ClO₂), and chloramine are all used as disinfectants for water.
- Smoke screens generally consist of fine particles of titanium oxide (TiO₂) dispersed in air.
- Fluorescent powder is used for developing fingerprints on multi-coloured surfaces.
- Potassium bromide (KBr) is used in photography.
- Potassium nitrate (KNO₃) is used in gunpowder.
- Potassium sulphate (K₂SO₄) is used as a fertilizer.
- Mono-potassium tartrate (KHC₄H₄O₆) is used in bakery products.
- German Silver contains Nickel.
- Solder contains Tin.
- Bleaching powder contains Chlorine.
- Hypo (sodium thiosulphate) contains Sodium.
- Gypsum is added to cement to slow down its rate of setting.
- Alkaline earth metals (e.g., Barium, Strontium) are highly reactive and are not found free in nature.
- Plaster of Paris is a chemical form of calcium sulphate.
- The chemical name of Magnesium chloride is MgCl₂.
- Boron nitride (BN) is known as inorganic graphite.
- When SiO₂ reacts with sodium carbonate (Na₂CO₃), carbon dioxide (CO₂) gas is liberated.
- The oxidation state of Oxygen in F₂O is +2, as fluorine is more electronegative than oxygen.
- The formula of Freon-12 is CF₂Cl₂ (dichlorodifluoromethane).
- Silica Gel is chemically composed of two atoms of Oxygen and one atom of Silicon (SiO₂).
- Methods for the estimation of nitrogen are Dumas and Kjeldahl's method.
- On treating a sodium fusion extract with sodium nitroprusside, the appearance of a violet colour is due to the formation of [Fe(CN)₅NOS]⁴⁻ (indicating the presence of sulfur).
- Hydrogen sulfide is not a part of the nitrogen cycle.
- "The History of Hindu Chemistry" is written by Sir Prafulla Chandra Ray.
- The chemical substance present in bones and teeth is calcium phosphate (as hydroxyapatite).
- The most common form of glass is Soda glass (soda-lime glass).
- The chemical used in indelible ink (election ink) is silver nitrate (AgNO₃).
- Approximately 20% of oxygen is present in the air.
- Mercury (Hg) is used in manometers.
- Silicon (Si) is a semiconductor.
- Sodium chloride (NaCl) is salt.
- Nichrome is used as a resistance wire.
- Test tubes are usually made of glass.
- Crookes glass contains cerium oxide.
- Lithium-ion batteries are secondary (rechargeable) cells. The anode (negative electrode) in a lithium-ion battery is usually made up of graphite, coated on copper foil.
- Nickel-cadmium (Ni-Cd) batteries have a
- "Aqua Regia" is a mixture of concentrated HCl and concentrated HNO₃ (typically 3:1 ratio).
Chemistry of Transition and Inner-Transition Elements (d-block and f-block)
- Anhydrous Copper(II) Sulfate (CuSO₄) is white.
- Hydrated Copper(II) Sulfate (CuSO₄·5H₂O) is blue due to the presence of water molecules.
- In V₂O₇⁻⁴, Vanadium (V) has an oxidation state of +5.
- Iron(III) oxide (Fe₂O₃) exhibits a single oxidation state for Iron (+3).
- Silver Bromide (AgBr) is used in black and white photography.
- A Ferrous Sulphate crystal (green vitriol) contains 7 water molecules (FeSO₄·7H₂O).
- Manganese (Mn) commonly exhibits a +7 oxidation state, for example, in KMnO₄.
- The highest oxidation state of Manganese is +7, found in KMnO₄.
- When one mole of KMnO₄ (Mn⁷⁺) is reduced:
- To MnO₄²⁻ (Mn⁶⁺), 1 electron is transferred.
- To MnO₂ (Mn⁴⁺), 3 electrons are transferred.
- To Mn₂O₃ (Mn³⁺), 4 electrons are transferred.
- To Mn²⁺ (Mn²⁺), 5 electrons are transferred.
- The lanthanoids series consists of 14 elements in the periodic table.
- Strontium (for red) and Barium (for green) salts are used to provide colours in fireworks.
- Copper(II) Sulfide (CuS) is black.
- Transition elements typically form colored compounds, exhibit variable oxidation states, and act as good catalysts.
- Transition elements are characterized by having incompletely filled d-orbitals in their atomic or common ionic states.
Coordination Compounds
- In [AlCl(H₂O)₅]²⁺, Al has an oxidation state of +3 (x + (-1) + 5(0) = +2) and a coordination number (covalency) of 6 (1 Cl + 5 H₂O ligands).
- IUPAC nomenclature for coordination compounds: Cationic complex named first, then anionic complex.
- Ligands named alphabetically before the metal.
- Prefixes di-, tri-, tetra- for simple ligands; bis-, tris-, tetrakis- for complex ligands.
- Anionic ligands end in '-o' (e.g., cyanido, chlorido). Neutral ligands are named as molecules (e.g., ammine, aqua, carbonyl).
- Metal name for cationic/neutral complex; metal name with '-ate' suffix for anionic complex.
- Oxidation state of metal in Roman numerals in parentheses.
- For [Ag(NH₃)₂][Ag(CN)₂]:
- Cationic part: [Ag(NH₃)₂]⁺ (Ag(I)). Name: Diamminesilver(I).
- Anionic part: [Ag(CN)₂]⁻ (Ag(I)). Name: Dicyanidoargentate(I).
- Full name: Diamminesilver(I) dicyanidoargentate(I).
- Isomerism in [CoCl₂(en)₂]Cl:
- Geometrical Isomerism (cis/trans): The octahedral complex [CoCl₂(en)₂]⁺ can exist as cis (chlorides adjacent) and trans (chlorides opposite) isomers.
- Optical Isomerism (Enantiomerism): The cis isomer of [CoCl₂(en)₂]⁺ is chiral and thus exhibits optical isomerism (non-superimposable mirror images). The trans isomer is achiral.
- This complex shows both geometrical and optical isomerism.
- Magnetic properties and geometry of Ni complexes:
- Ni(II) (d⁸) complexes:
- Tetrahedral (sp³): Typically formed with weak field ligands (e.g., Cl⁻). Due to small crystal field splitting (Δt), electrons remain unpaired. Thus, [NiCl₄]²⁻ is paramagnetic (2 unpaired electrons).
- Square Planar (dsp²): Typically formed with strong field ligands (e.g., CN⁻). Strong field causes pairing of d-electrons. Thus, [Ni(CN)₄]²⁻ is diamagnetic (0 unpaired electrons). [Ni(NH₃)₄]²⁺ can also be square planar and diamagnetic.
- Ni(0) (d¹⁰) complexes:
- Tetrahedral (sp³): All 10 d-electrons are paired. Thus, [Ni(CO)₄] is diamagnetic (0 unpaired electrons).
- Diamagnetic: All electrons are paired (0 unpaired electrons).
- Paramagnetic: Contains unpaired electrons.
- For [Ni(CO)₄]:
- Oxidation state of Ni is 0 (CO is a neutral ligand).
- Ni(0) has a d¹⁰ electronic configuration (all 10 valence electrons fill the dorbitals).
- In a d¹⁰ configuration, all electrons are paired.
- Therefore, [Ni(CO)₄] has 0 unpaired electrons and is diamagnetic.
- Its geometry is tetrahedral (sp³ hybridization).
Inorganic Reaction Mechanisms
- Balancing Chemical Equations:
- For Fe₂O₃(s) + CO(g) → Fe(s) + CO₂(g), the balanced equation is 1Fe₂O₃ + 3CO → 2Fe + 3CO₂. Coefficients: 1, 3, 2, 3.
- For Fe + H₂O → Fe₃O₄ + H₂, the balanced equation is 3Fe + 4H₂O → Fe₃O₄ + 4H₂. Coefficients: 3, 4, 1, 4.
- Redox Reaction Fundamentals:
- Oxidation: Loss of electrons, gain of oxygen, removal of hydrogen, increase in oxidation state.
- Reduction: Gain of electrons, loss of oxygen, gain of hydrogen, decrease in oxidation state.
- Oxidizing Agent (Oxidant): A substance that gets reduced itself, causing oxidation in another substance.
- Reducing Agent (Reductant): A substance that gets oxidized itself, causing reduction in another substance.
- Identifying Redox Reactions:
- A reaction is considered redox if there is a change in the oxidation states of at least one element.
- Example of a non-redox reaction: AlCl₃ + 3H₂O → Al(OH)₃ + 3HCl (no change in oxidation states for Al, Cl, H, or O).
- Disproportionation Reactions:
- Occur when an element in a single oxidation state is simultaneously oxidized and reduced.
- Requires the element to possess at least three possible oxidation states, with its initial state being intermediate.
- The ClO₄⁻ ion (where Cl is in its highest oxidation state, +7) cannot undergo disproportionation as it cannot be further oxidized.
- Species like ClO⁻ (Cl +1), ClO₂⁻ (Cl +3), ClO₃⁻ (Cl +5) can disproportionate.
- Common Reducing & Oxidizing Agents:
- Reducing substances (reductants): Iron (Fe), Hydrogen (H₂), Carbon (C), Carbon Monoxide (CO), active metals.
- Oxidizing substances (oxidants): Oxygen (O₂), Potassium permanganate (KMnO₄, Mn in +7 state), Potassium dichromate (K₂Cr₂O₇, Cr in +6 state).
- Potassium Permanganate (KMnO₄): Acts as a strong oxidizing agent and is a self-indicator in redox titrations (purple MnO₄⁻ to colorless Mn²⁺ in acidic medium).
- Specific Redox Reaction Examples:
- In 2Cu₂O (s) + Cu₂S (s) → 6Cu (s) + SO₂ (g): Cu(I) (from both Cu₂O and Cu₂S) is reduced to Cu(0), acting as the oxidant. S(-2) in Cu₂S is oxidized to S(+4) in SO₂, acting as the reductant.
- In PbO + H₂ → Pb + H₂O: Lead is reduced (Pb(+2) to Pb(0)), and hydrogen is oxidized (H(0) to H(+1)).
- In CuO + H₂ → Cu + H₂O: Copper is reduced (Cu(+2) to Cu(0)), and hydrogen is oxidized (H(0) to H(+1)).
- Fire Extinguishers for Electrical Fires:
- Dry chemical powder extinguishers are appropriate for fires due to electric short circuits as they are non-conductive and smother the flames. Foam and pressurized water extinguishers are unsafe due to conductivity.
- Nobel Prize in Chemistry Facts:
- Frederick Sanger: Received the Nobel Prize in Chemistry twice, in 1958 and 1980. The gap between the two prizes was 22 years (> 20 years).
- Paul J. Crutzen: Awarded the Nobel Prize in Chemistry in 1995. He was a citizen of The Netherlands and is known for popularizing the term 'Anthropocene'.
Nuclear Chemistry
- Faraday constant (F) is a universal constant, representing the amount of electric charge per mole of electrons.
- Isotopes of Uranium (e.g., U-235) are used as nuclear fuel.
- Isotopes of Cobalt (e.g., Co-60) are used in the treatment of cancer, specifically in radiation therapy.
- Isotopes of Iodine (e.g., I-131) are used in the treatment of goitre and other thyroid conditions.
- Isotopes of Radium (e.g., Ra-223) are used in the treatment of certain cancers, including secondary cancer (bone metastases).
- Astatine (At) and Francium (Fr) are highly radioactive elements with no stable isotopes.
- Tritium (³H) is a radioactive isotope of hydrogen.
- Zirconium (Zr) has several stable isotopes and is generally not considered radioactive in the same context as Astatine, Francium, or Tritium.
Organometallic Chemistry
- Organometallic compounds contain at least one metal-carbon bond (M-C).
- Metal carbonyls are organometallic compounds with carbon monoxide (CO) ligands.
- Metal clusters are compounds featuring three or more metal atoms linked by direct metalmetal bonds.
- Fe${3}$(CO)${12}$ is an example of a trinuclear metal cluster (triangular geometry).
- Dinuclear metal carbonyls like Fe${2}$(CO) ${9}$, Co${2}$(CO)${8}$, and Mn${2}$ (CO)${10}$ contain two metal atoms with metal-metal bonds but are generally not classified as "clusters" in the strict sense (which typically implies 3+ metal atoms).
Solid State Inorganic Chemistry
- Flint glass is used for making optical instruments.
- Glass is an amorphous solid, often described as a supercooled liquid, and has no definite melting point.
- Crystallinity does not develop upon cooling of molten glass; it remains amorphous.
- Sodium silicate is known as water glass.
- Coloured glasses are made by adding different colouring materials (e.g., metal oxides).
- Pyrex glass (borosilicate glass) contains boron and is harder and more heat-resistant than soda-lime (soft) glass.
- Main raw materials for glass manufacture include silica (sand), sodium carbonate (soda ash), and limestone.
- Cerium oxide (CeO₂) is used in the manufacture of ultra-violet protective glasses.
- Photochromatic glass turns dark in sunlight due to the decomposition of silver halides (e.g., AgCl, AgBr, AgI) into silver metal.
- Glass and sand are not used as lubricants in heavy industries.
- Major raw materials for cement manufacture are limestone and clay.
- Essential constituents of Portland cement include silica (SiO₂), alumina (Al₂O₃), and lime (CaO).
- Cement contains calcium silicate, calcium aluminate, and calcium sulfoaluminate.
- Gypsum (CaSO₄·2H₂O) is added to cement clinker to increase (lengthen/retard) the setting time, thereby decreasing the rate of setting and preventing flash setting.
- Tricalcium silicate (C₃S) is primarily responsible for the initial setting and early strength of cement.
- Dicalcium silicate (C₂S) and tricalcium silicate (C₃S) contribute to the final longterm strength of cement.
- During cement setting, hydrated silicate gels form and harden, leading to a gain in strength.
- Silicon carbide (SiC) is also known as Carborundum.
- Carborundum (SiC) is used as an abrasive due to its extreme hardness.
- In an NaCl lattice, both Na⁺ and Cl⁻ ions have a coordination number of 6.
- Concrete is a thick paste made of cement, sand, stone chips (aggregates), and water.
- Zone refining is used for the ultra-purification of semiconductors such as Silicon (Si), Germanium (Ge), and Gallium (Ga).
- Ultramarine blue pigment is a complex alumino-silicate containing sulfur.
- Alumina (Al₂O₃) is a common adsorbent used in adsorption chromatography.
- Silica gel is chemically inert, non-toxic, noncorrosive, and can be conditioned to a particular level before use.
- Solid lubricants include Graphene and Talc.
- Nanomaterial uses: Sunscreen lotion (Titanium oxide nanoparticles), Textiles (Nano silver for antimicrobial properties), Optoelectronics (Quantum dots), High-definition television (Zinc selenide, Quantum dots).
4. Metals, Minerals, Ores: Properties,
Uses
Practice MCQs: Inorganic Chemistry
Acid-Base Chemistry and Non-aqueous Solvents
In case of a standard hydrogen electrode
Asked in: UPSC CDS 2 2016 · JUNIOR laboratory assistant 2025
- absolute electrode potential is not zero
- absolute electrode potential is zero
- both absolute and standard electrode potential values are zero
- electrode potential is zero only at 25°C
Show answer
Answer: A. absolute electrode potential is not zero
By international convention, the standard electrode potential of the SHE is defined as zero volts (0 V) at standard conditions (typically 25°C, 1 bar/atm H₂ pressure, and 1 M H⁺ concentration). This defines a relative scale for measuring the standard potentials C. 10-20 mL of material D. All of the above Ans: D Hickman heads are specifically designed for microscale distillations, minimizing material loss and maximizing recovery.
By what process, can acetone be separated from a mixture of acetone and methyl alcohol?
Asked in: Group B Exam 2012
- Filtration
- By separating funnel
- By fractional crystallisation
- By fractional distillation
Show answer
Answer: D. By fractional distillation
This question tests the understanding of separation techniques for liquid mixtures based on their physical properties, specifically boiling points. of other half-cells. However, the absolute potential of the SHE, which represents the potential difference between the electrode and a point infinitely far away in vacuum, is not zero and is estimated to be around +4.44 V at 25°C.
Which of the following functions as primary standard?
Asked in: WBCS Main Paper 4 2022
- KMnO₄
- K₂Cr₂O₇
- Sodium Thiosulphate
- EDTA
Show answer
Answer: B. K₂Cr₂O₇
- A primary standard is a substance of high purity, stable in air, not hygroscopic, with a precisely known formula, and a high equivalent weight, used for standardizing solutions. - Potassium permanganate (KMnO₄) is a strong oxidizing agent but is not a primary standard because it is difficult to obtain in high purity, is not completely stable in solution, and can be reduced by organic matter. - Sodium Thiosulphate (Na₂S₂O₃) is typically used as a secondary standard, requiring standardization against a primary standard like potassium iodate or potassium dichromate, as its solutions are not highly stable. - EDTA (Ethylenediaminetetraacetic acid) is also commonly used as a secondary standard, standardized against primary standards like calcium carbonate or zinc. - Potassium dichromate is stable, non-hygroscopic, and readily available in high purity, making it suitable as a primary standard, particularly in redox titrations.
Pair of hard bases among the following is -
Asked in: Department Recruitment 2024 (Chemist) 2024
- R-NH$_{2}$, CN$^{-}$
- N$_{2}$H$_{4}$, R$_{3}$P
- CO$_{3}^{2-}$, NO$_{3}^{-}$
- NH$_{3}$, CO
Show answer
Answer: C. CO$_{3}^{2-}$, NO$_{3}^{-}$
In the context of Hard-Soft Acid-Base (HSAB) theory, hard bases are small, highly charged, and have a low polarizability. Soft bases are large, low charged, and highly polarizable.
Which statement is true about aqua regia? I. Aqua regia is a mixture of HNO$_{3}$ and HCl, in a molar ratio of 3 : 1 II. Nitrosyl chloride and nitrogen dioxide impart yellow/orange colour to aqua regia III. Aqua regia can dissolve gold and platinum IV. pH of aqua regia is $> 7$
Asked in: mineral dev officier 2025
- I, II and III
- I and II
- II and III
- I and III
Show answer
Answer: A. I, II and III
Aqua regia is a mixture of concentrated nitric acid (HNO$_{3}$) and concentrated hydrochloric acid (HCl). It is known for its ability to dissolve noble metals like gold and platinum. Nitrosyl chloride (NOCl) is formed and contributes to its colour and reactivity. Its pH is highly acidic. The standard ratio is 1 part HNO$_{3}$ to 3 parts HCl by volume or molarity.
Atomic Structure and Periodicity
Who is regarded as the Father of Modern Chemistry?
Asked in: BPSC Prelims Exam 65th
- Rutherford
- Einstein
- Lavoisier
- C. V. Raman
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Answer: C. Lavoisier
- Lavoisier introduced quantitative measurements, clarified the concept of elements, named oxygen and hydrogen, and formulated the law of conservation of mass. - These contributions marked a shift from alchemy to modern chemistry.
Which of the following is not a type of element?
Asked in: BPSC Prelims Exam 65th
- Metals
- Nonmetals
- Gases
- Metalloids
Show answer
Answer: C. Gases
- Metals, Nonmetals, and Metalloids are categories used to classify elements on the periodic table. - "Gases" refers to a state of matter, not a fundamental classification of elements based on their inherent properties (like conductivity, reactivity, etc.) across all states and conditions.
UNESCO inaugurated the celebration of 2019 as the International Year of the Periodic Table of Chemical Elements to celebrate its completion of how many years?
Asked in: BPSC Prelims Exam 65th
- 100
- 150
- 75
- 50
Show answer
Answer: B. 150
Dmitri Mendeleev published his first version of the Periodic Table of Elements in 1869. Therefore, 2019 marked 150 years since this seminal event.
What is the total number of naturally occurring elements ?
Asked in: UPSC CDS 2 2023
- 114
- 94
- 86
- 82
Show answer
Answer: B. 94
Elements up to atomic number 92 (Uranium) are generally considered naturally occurring on Earth in macroscopic quantities. Elements with atomic numbers 93 (Neptunium) and 94 (Plutonium) also occur naturally, but only in trace amounts, primarily as products of neutron capture and radioactive decay of Uranium. Elements beyond 94 are predominantly synthetic, created in laboratories or nuclear reactions, although some very heavy elements might exist fleetingly in specific astrophysical events.
Which one of the following statements about the law of chemical combination is not correct?
Asked in: UPSC Geoscientist 2022
- Equal volumes of all gases at the same temper‐ ature and pressure contain equal number of mo‐ lecules.
- If two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of other element, are not in any proportion.
- Matter can neither be created nor destroyed.
- A given compound always contains exactly the same proportion of elements by weight.
Show answer
Answer: B. If two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of other element, are not in any proportion.
The Law of Chemical Combination includes fundamental principles like the Law of Conservation of Mass, Law of Definite Proportions, and Law of Multiple Proportions.
What is the number of moles of carbon in a sample containing 72.06 g of carbon?
Asked in: UPSC Geoscientist 2022
- 4
- 6
- 2
- 8
Show answer
Answer: B. 6
- The number of moles relates mass to the number of particles (atoms or molecules). - Molar mass is the mass of one mole of a substance. - The atomic mass of Carbon (C) is the basis for its molar mass.
Who among the following scientists developed the Modern Periodic Table ?
Asked in: UPSC Geoscientist 2024
- Henry Moseley
- Dmitri Ivanovich Mendeleev
- John Alexander Newlands
- Johann Döbereiner
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Answer: A. Henry Moseley
Moseley's work in 1913 using X-ray spectroscopy showed that the atomic number (the number of protons in an atom's nucleus) is a more fundamental property than atomic mass for organizing the elements. Arranging elements by increasing atomic number resolves anomalies present in Mendeleev's table.
Which one among the following is the correct arrangement in increasing order of ionic radii of O²⁻, F⁻, Na⁺, Mg²⁺ ?
Asked in: UPSC Geoscientist 2024
- Mg²⁺ < Na⁺ < F⁻ < O²⁻
- O²⁻ < F⁻ < Na⁺ < Mg²⁺
- Mg²⁺ < Na⁺ < O²⁻ < F⁻
- O²⁻ < F⁻ < Mg²⁺ < Na⁺
Show answer
Answer: A. Mg²⁺ < Na⁺ < F⁻ < O²⁻
The given ions O²⁻, F⁻, Na⁺, and Mg²⁺ are isoelectronic species, meaning they all have the same number of electrons (10 electrons, with the electronic configuration $1s^2 2s^2 2p^6$). For isoelectronic species, the ionic radius decreases as the nuclear charge (atomic number) increases. A higher nuclear charge exerts a stronger attraction on the same number of electrons, pulling them closer to the nucleus and reducing the ionic size. The atomic numbers are: Oxygen (O) = 8, Fluorine (F) = 9, Sodium (Na) = 11, Magnesium (Mg) = 12. The effective nuclear charges are approximately +8 for O²⁻, +9 for F⁻, +11 for Na⁺, and +12 for Mg²⁺. As the nuclear charge increases (from +8 to +12), the attraction on the 10 electrons increases, leading to a decrease in ionic size. Order of increasing nuclear charge: O²⁻ (+8) F⁻ > Na⁺ > Mg²⁺. Order of increasing ionic radii: Mg²⁺
Bioinorganic Chemistry
Which one among the following trace elements is not highly toxic ?
Asked in: UPSC Geoscientist 2024
- Arsenic
- Chromium
- Copper
- Mercury
Show answer
Answer: C. Copper
- Arsenic (As) is a metalloid widely recognized as highly toxic and carcinogenic. - Chromium (Cr) has both essential and toxic forms; Hexavalent chromium (Cr(VI)) is highly toxic and carcinogenic. - Mercury (Hg) is a heavy metal that is highly toxic, particularly in its organic form (methylmercury), affecting the nervous system. - Copper (Cu) is an essential trace element necessary for many biological processes. While excessive intake can cause toxicity, it is less likely to be classified as highly toxic compared to arsenic, mercury, and certain forms of chromium in common environmental exposures, as the body has mechanisms to regulate copper levels and it is required for life.
Which of the following categories of Nobel Prize, 2023 was awarded to Moungi G. Bawendi, Louis E. Brus and Alexei Ekimov?
Asked in: GA Acts Rules CHEX 27 2023 0307 2024
- Physiology or Medicine
- Physics
- Chemistry
- None of the above
Show answer
Answer: C. Chemistry
Knowing the recipients and their respective fields for the Nobel Prizes is a common aspect of current affairs questions.
Which element is essential for blood clotting?
Asked in: moter vehicle inspector
- Ca
- Ba
- Sr
- Ra
Show answer
Answer: A. Ca
Calcium ions are indispensable for blood coagulation.
Catalysis by Inorganic Compounds
By green chemistry, we mean
Asked in: MPSC CS Prelims 2019
- Producing chemicals of our daily use from greenhouse gases
- Performing chemical processes which use green plants
- Performing only those reactions which are of biological origin
- The use of non-toxic reagents and solvents to produce environmentally-friendly products
Show answer
Answer: D. The use of non-toxic reagents and solvents to produce environmentally-friendly products
Green chemistry is the design of chemical products and processes that reduce or eliminate the use or generation of hazardous substances. It focuses on pollution prevention at the source by modifying chemical synthesis methods to be safer, more efficient, and environmentally benign.
Statement-I: Oxygen gas is easily produced at a faster rate by heating a mixture of potassium chlorate and manganese dioxide than heating potassium chlorate alone. Statement-II: Manganese dioxide acts as a negative catalyst.
Asked in: UPSC NDA 1 2015
- Both the statements are individually true and Statement II is the correct explanation of Statement I
- Both the statements are individually true but Statement II is not the correct explanation of Statement I
- Statement I is true but Statement II is false
- Statement I is false but Statement II is true
Show answer
Answer: C. Statement I is true but Statement II is false
Statement I correctly describes the effect of adding manganese dioxide (MnO₂) to potassium chlorate (KClO₃) when heated. MnO₂ acts as a catalyst, speeding up the decomposition of KClO₃ into potassium chloride (KCl) and oxygen gas (O₂). The reaction is 2KClO₃ (s) → 2KCl (s) + 3O₂ (g). Statement II claims that manganese dioxide acts as a negative catalyst. A negative catalyst (or inhibitor) slows down a reaction. Since MnO₂ increases the rate of decomposition of KClO₃, it is a positive catalyst.
Consider the following reaction : Fe2O3(s) + 2Al(s) → 2Fe(s) + Al2O3(s) Which of the following statements about the given reaction is NOT correct ?
Asked in: UPSC NDA 2 2023
- It is an example of displacement reaction
- It is highly endothermic reaction
- Fe2O3 acts as oxidizing agent
- This reaction is applicable to joining of railway tracks
Show answer
Answer: B. It is highly endothermic reaction
The reaction Fe2O3(s) + 2Al(s) → 2Fe(s) + Al2O3(s) is known as the thermite reaction. It is a highly exothermic reaction, releasing a large amount of heat. Aluminum is more reactive than iron and displaces iron from its oxide, making it a displacement reaction. Fe2O3 is reduced (loses oxygen), so it acts as an oxidizing agent. The large amount of heat produced makes this reaction useful for welding, including joining railway tracks.
Green chemistry uses following oxidising agent for clean oxidation
Asked in: WBCS Main Paper 4 2022
- K$_2$Cr$_2$O$_7$
- NH$_4$NO$_3$
- K$_2$S$_2$O$_8$
- Aqueous H$_2$O$_2$
Show answer
Answer: D. Aqueous H$_2$O$_2$
Green chemistry promotes the use of environmentally benign reagents and processes. H₂O₂ is favoured because its main byproduct upon reduction is water, which is harmless.
Chemical Bonding and Molecular Structure
What is the bond order of CO group?
Asked in: BPSC Prelims Exam 65th
- 1
- 2.5
- 3.5
- 3
Show answer
Answer: D. 3
Using molecular orbital theory, the bond order of CO is calculated as 3. This consists of one sigma bond and two pi bonds.
Which one of the following is not a characteristic of a compound?
Asked in: UPSC CDS 1 2018
- Composition is variable.
- All particles of compound are of only one type.
- Particles of compound have two or more ele‐ ments.
- Its constituents cannot be separated by simple physical methods.
Show answer
Answer: A. Composition is variable.
A defining characteristic of a compound is its fixed and definite composition by mass.
The PCl$_{5}$ molecule has trigonal bipyramidal structure. Therefore, the hybridization of p orbitals should be
Asked in: UPSC CDS 1 2019
- sp$^{2}$
- sp$^{3}$
- dsp$^{2}$
- dsp$^{3}$
Show answer
Answer: D. dsp$^{3}$
- PCl$_{5}$ has a trigonal bipyramidal structure. - This structure arises from the hybridization of the central atom's valence orbitals. - A trigonal bipyramidal geometry corresponds to sp$^3$d (or dsp$^3$) hybridization. - The central P atom has 5 bonding pairs and 0 lone pairs.
Which one of the following has the highest ionic character?
Asked in: UPSC CDS 1 2024
- BeF₃
- SiO₂
- NCl₃
- K₂S
Show answer
Answer: D. K₂S
Ionic character is primarily determined by the electronegativity difference between the bonded atoms. A larger electronegativity difference leads to a more ionic bond. Bonds between highly electropositive metals (Group 1 and 2) and highly electronegative non-metals (Group 16 and 17) are generally ionic.
Which one among the following substances is a compound ?
Asked in: UPSC CDS 2 2023
- Sugar
- Air
- Milk
- Tea
Show answer
Answer: A. Sugar
Sugar (commonly sucrose, C₁₂H₂₂O₁₁) is made up of Carbon, Hydrogen, and Oxygen atoms chemically combined in a fixed ratio. Therefore, sugar is a compound. Air is a mixture of gases like nitrogen, oxygen, argon, carbon dioxide, etc. Milk is a complex mixture of water, fats, proteins, carbohydrates, minerals, etc. Tea is an aqueous mixture containing compounds extracted from tea leaves.
The electrostatic repulsion between electron pairs such as lone pair - lone pair (l.p. - l.p.), bond pair - bond pair (b.p. - b.p.) and lone pair - bond pair (l.p. - b.p.) in a given valence shell decreases in the order of _______.
Asked in: MPSC CS Prelims 2022
- l.p. - l.p. < l.p. - b.p. < b.p. - b.p.
- l.p. - l.p. > l.p. - b.p. > b.p. - b.p.
- b.p. - b.p. < l.p. - l.p. < l.p. - b.p.
- l.p. - b.p. > b.p. - b.p. > l.p. - l.p.
Show answer
Answer: B. l.p. - l.p. > l.p. - b.p. > b.p. - b.p.
- VSEPR theory predicts molecular geometry based on minimizing electron pair repulsions. - Lone pairs exert stronger repulsions than bond pairs. - The order of repulsion strength is l.p.-l.p. > l.p.-b.p. > b.p.-b.p.
Which of the following is correct for the shapes of NH₃ and BF₃ ?
Asked in: MPSC CS Prelims 2023
- NH₃ - Pyramidal and BF₃ - Pyramidal
- NH₃ - Planar and BF₃ - Planar
- NH₃ - Planar and BF₃ - Pyramidal
- NH₃ - Pyramidal and BF₃ - Planar
Show answer
Answer: D. NH₃ - Pyramidal and BF₃ - Planar
VSEPR theory predicts molecular geometry based on the repulsion between electron pairs (both bonding and lone pairs) around the central atom. The arrangement of electron pairs minimizes repulsion. Lone pairs exert more repulsion than bonding pairs, influencing the bond angles and molecular shape.
Which one of the following is the correct molecular formula of ammonium carbonate if the valency of ammonium ion is (+1) and carbonate anion is (-2) ?
Asked in: UPSC NDA 1 2022
- (NH₄)₂CO₃
- NH₄(CO₃)₂
- (NH₃)₂CO₃
- NH₄CO₃
Show answer
Answer: A. (NH₄)₂CO₃
The valency (or charge) of the ammonium ion (NH₄⁺) is +1. The valency (or charge) of the carbonate anion (CO₃²⁻) is -2. To form a neutral compound, we need a total positive charge equal in magnitude to the total negative charge. If we take two ammonium ions, the total positive charge is 2 (+1) = +2. If we take one carbonate ion, the total negative charge is 1 (-2) = -2. The charges +2 and -2 balance to give a neutral compound. Therefore, the formula is (NH₄)₂CO₃, indicating two ammonium ions for every one carbonate ion.
Chemistry of Main Group Elements (s-block and p-block)
Quartz crystals used in clocks are
Asked in: BPSC Prelims Exam 63rd
- sodium silicate
- silicon dioxide
- germanium oxide
- titanium dioxide
Show answer
Answer: B. silicon dioxide
- Quartz is one of the most abundant minerals in the Earth's continental crust. - Its chemical formula is SiO₂, which represents silicon dioxide. - It is a hard, brittle mineral. - Quartz crystals exhibit piezoelectric properties, meaning they can generate an electric charge when subjected to mechanical stress and vice versa. This property is what makes them useful in electronic oscillators, including those in clocks and watches.
Which of the following is also known as laughing gas?
Asked in: BPSC Prelims Exam 65th UPPCS Prelims 2023
- Nitric oxide
- Nitrous oxide
- Nitrogen pentoxide
- Nitrogen
Show answer
Answer: B. Nitrous oxide
- Chemical compound N₂O is also known as dinitrogen monoxide or nitrous oxide. - Historically used as an anaesthetic and analgesic, and recreationally due to its psychoactive effects.
Which among the following is known as quicklime?
Asked in: BPSC Prelims Exam 67th Re Exam
- CaCO₂
- Ca(OH)₂
- CaCl₂
- CaO
Show answer
Answer: D. CaO
Quicklime is the common name for the chemical compound calcium oxide (CaO).
When we heat lead nitrate [Pb(NO₃)₂] in a boiling tube, we observe the emission of brown fumes. Which one of the following is the brown gas ?
Asked in: UPSC CDS 1 2021
- NO
- N₂O₂
- NO₃
- NO₂
Show answer
Answer: D. NO₂
- The balanced chemical equation for the decomposition of lead nitrate is: 2Pb(NO₃)₂(s) → 2PbO(s) + 4NO₂(g) + O₂(g). - Nitrogen dioxide (NO₂) is a toxic, reddish-brown gas.
Which of the following statements with regard to the reaction given below are correct? CaO(s) + H₂O(l) → Ca(OH)₂(aq) + Heat 1. Quicklime is used for white-washing of walls. 2. The solution of slaked lime is used for whitewashing of walls. 3. CaO reacts slowly with CO₂ in air to form a thin layer of CaCO₃ on walls. 4. Calcium hydroxide called ‘slaked lime’ is an inorganic compound. Select the correct answer using the code given below.
Asked in: UPSC CDS 1 2023
- 1 and 4 only
- 2 and 4
- 2 and 3
- 1, 3 and 4
Show answer
Answer: B. 2 and 4
Slaked lime (Ca(OH)₂) solution is used for whitewashing. Slaked lime reacts with CO₂ in air to form CaCO₃.
Which one of the following is an amphoteric oxide?
Asked in: UPSC CDS 1 2024
- MgO
- P₄O₁₀
- Na₂O
- Al₂O₃
Show answer
Answer: D. Al₂O₃
Amphoteric oxides react with both acids and bases. Aluminium oxide (Al₂O₃) is an amphoteric oxide.
In paper manufacturing, degumming of the raw material is done using
Asked in: UPSC CDS 2 2016
- sulphuric acid
- bleaching powder
- caustic soda
- nitric acid
Show answer
Answer: C. caustic soda
Caustic soda is a strong alkali used in the pulping process to dissolve lignin and other impurities, separating the cellulose fibres. This process effectively "degums" or cleans the fibres before they are processed into paper. Bleaching powder is used for whitening the pulp after pulping. Sulphuric acid and nitric acid are strong acids with different applications (e.g., in chemical processing or nitration) and are not typically the primary agents for degumming in standard paper pulping, although acidic processes (like the sulfite process) exist, they target lignin and hemicellulose differently than the general removal of gummy substances often associated with alkaline treatments or specific fibre degumming steps.
Which one of the following elements does not form solid hydrogen carbonate?
Asked in: UPSC CDS 2 2016
- Sodium
- Potassium
- Caesium
- Lithium
Show answer
Answer: D. Lithium
LiHCO₃ exists in aqueous solution, but when attempts are made to isolate it as a solid, it readily decomposes upon heating or dehydration into lithium carbonate (Li₂CO₃), water (H₂O), and carbon dioxide (CO₂). This instability prevents the formation of a stable solid crystalline LiHCO₃ under normal conditions, unlike NaHCO₃, KHCO₃, CsHCO₃, etc., which are stable solids. This difference is often attributed to Lithium's small ionic size and relatively high polarizing power (diagonal relationship with Magnesium).
Chemistry of Transition and Inner-Transition Elements (d-block and f-block)
What is the colour of anhydrous CuSO₄ ?
Asked in: UPSC Geoscientist 2024
- White
- Blue
- Green
- Yellow
Show answer
Answer: A. White
Copper(II) sulfate exists in several hydration states. The most common form is copper(II) sulfate pentahydrate (CuSO₄·5H₂O), which is a bright blue crystalline solid. The blue colour is due to the presence of hydrated copper(II) ions, [Cu(H₂O)₄]²⁺, where water molecules act as ligands coordinated to the Cu²⁺ ion. The d-d electronic transitions within the Cu²⁺ ion, influenced by the surrounding water ligands, cause the absorption of certain wavelengths of visible light (specifically red-orange light), resulting in the complementary blue colour being observed. When copper(II) sulfate pentahydrate is heated, it loses its water of crystallization. The blue pentahydrate first turns into pale blue CuSO₄·3H₂O, then blue-green CuSO₄·H₂O, and finally becomes anhydrous copper(II) sulfate (CuSO₄), which is a white powder. In the anhydrous state, the crystal structure changes, and the Cu²⁺ ion is no longer surrounded by water ligands in the same way. This alters the energy levels of the d orbitals, and the absorption characteristics change such that no visible light is strongly absorbed, causing the compound to appear white.
The oxidation state of V in V₂O₇⁻⁴ is _______.
Asked in: MPSC CS Prelims 2022
- + 5
- - 5
- + 4
- + 10
Show answer
Answer: A. + 5
- The sum of oxidation states in a neutral molecule is zero. - The sum of oxidation states in a polyatomic ion equals the charge of the ion. - Oxygen typically has an oxidation state of -2, except in peroxides (-1) or superoxides (-1/2). - The oxidation state of an element in its elemental form is zero.
Copper sulphate crystals available in the market are blue coloured crystals. By careful heating, they turn to white colour. Which one of the following is responsible for the blue colour ?
Asked in: UPSC NDA 1 2023
- Oxygen
- Nitrogen
- Water
- Hydrogen
Show answer
Answer: C. Water
The blue colour of hydrated copper sulphate is caused by the presence of water molecules bound within the crystal structure.
Which one of the following compounds does not exhibit a different oxidation number of the same element?
Asked in: UPSC NDA 2 2019
- Pb₃O₄
- Fe₃O₄
- Fe₂O₃
- Mn₃O₄
Show answer
Answer: C. Fe₂O₃
We need to determine the oxidation state of the metal element in each compound: A) Pb₃O₄ is a mixed oxide, often written as 2PbO·PbO₂. In PbO, O is -2, so Pb is +2. In PbO₂, O is -2 (total -4 for 2 O atoms), so Pb is +4. Lead has oxidation states +2 and +4 in Pb₃O₄. B) Fe₃O₄ is a mixed oxide, FeO·Fe₂O₃. In FeO, O is -2, so Fe is +2. In Fe₂O₃, O is -2 (total -6 for 3 O atoms), so 2 Fe atoms are +6, meaning each Fe is +3. Iron has oxidation states +2 and +3 in Fe₃O₄. C) Fe₂O₃: Assuming oxygen is -2, the total charge from 3 oxygen atoms is 3 (-2) = -6. For the compound to be neutral, the total charge from 2 iron atoms must be +6. Thus, the oxidation state of each Fe atom is +6 / 2 = +3. All iron atoms in Fe₂O₃ are in the +3 oxidation state. D) Mn₃O₄ is a mixed oxide, MnO·Mn₂O₃. In MnO, O is -2, so Mn is +2. In Mn₂O₃, O is -2 (total -6 for 3 O atoms), so 2 Mn atoms are +6, meaning each Mn is +3. Manganese has oxidation states +2 and +3 in Mn₃O₄.
Which one of the following compounds is used in 'black and white' photography ?
Asked in: UPSC NDA 2 2021
- AgF
- AgBr
- AgCl
- Ag₂SO₄
Show answer
Answer: B. AgBr
- Silver halides are photosensitive compounds. - AgBr is widely used in photographic films.
What is the number of water molecules present in a Ferrous Sulphate crystal ?
Asked in: UPSC NDA 2 2021
- 1
- 3
- 5
- 7
Show answer
Answer: D. 7
- Ferrous Sulphate forms hydrated crystals. - The most common hydrate is the heptahydrate (FeSO₄·7H₂O).
Match the Number of electrons transferred (a) when one mole of KMnO₄ is reduced to (b) (a) 1, 3, 4, 5 (b) Mn₂O₃, MnO₂, MnO₄²⁻, Mn²⁺
Asked in: TNPSC CS Prelims 2015
- 1 – MnO₄²⁻, 3 – MnO₂, 4 – Mn₂O₃, 5 – Mn²⁺
- 1 – Mn²⁺, 3 – Mn₂O₃, 4 – MnO₂, 5 – MnO₄²⁻
- 1 – MnO₂, 3 – Mn²⁺, 4 – MnO₄²⁻, 5 – Mn₂O₃
- 1 – Mn₂O₃, 3 – Mn²⁺, 4 – MnO₄²⁻, 5 – MnO₂
Show answer
Answer: A. 1 – MnO₄²⁻, 3 – MnO₂, 4 – Mn₂O₃, 5 – Mn²⁺
- KMnO₄ contains manganese in the +7 oxidation state (as MnO₄⁻). - Reduction involves gaining electrons, decreasing the oxidation state of manganese. - Calculate the oxidation state of manganese in each given product (Mn₂O₃, MnO₂, MnO₄²⁻, Mn²⁺). - The number of electrons transferred is the difference between the initial (+7) and final oxidation states of manganese.
Which one of the following elements has the oxidation state as +7 ?
Asked in: UPSC CISF AC EXE 2018
- Nitrogen
- Phosphorus
- Manganese
- Magnesium
Show answer
Answer: C. Manganese
Manganese (Mn) is a transition metal that can exhibit various oxidation states, including +2, +3, +4, +6, and +7. In compounds like potassium permanganate (KMnO4), Manganese has an oxidation state of +7.
Coordination Compounds
The oxidation state and covalency of Al in [AlCl (H₂O)₅]²⁺ are
Asked in: UPSC Geoscientist 2023
- + 3 and 3
- + 3 and 6
- + 2 and 6
- + 2 and 1
Show answer
Answer: B. + 3 and 6
Oxidation state is the charge the central atom would have if all ligands were removed along with the electron pairs they donate. Covalency in coordination complexes is the number of coordinate bonds formed, equal to the coordination number.
Which one of the following is the IUPAC name of [Ag(NH₃)₂] [Ag(CN)₂] ?
Asked in: UPSC Geoscientist 2024
- Diammine dicyanidodisilver(I)
- Diammine dicyanidoargentate(I)
- Diamminesilver(I) dicyanidoargentate(I)
- Dicyanidoargentate(I) diamminesilver(I)
Show answer
Answer: C. Diamminesilver(I) dicyanidoargentate(I)
For the cation [Ag(NH₃)₂]⁺: The metal is Silver (Ag). Ammonia (NH₃) is an neutral ligand named 'ammine'. There are two ammine ligands (diammine). The charge of the complex is +1. Since NH₃ is neutral, the oxidation state of Ag is +1. As it is a cation, the metal name is used as is, followed by the oxidation state in Roman numerals. Name: Diamminesilver(I). For the anion [Ag(CN)₂]⁻: The metal is Silver (Ag). Cyanide (CN⁻) is an anionic ligand named 'cyanido' or 'cyano'. There are two cyanido ligands (dicyanido). The charge of the complex is -1. Since CN⁻ has a charge of -1, Ag + 2(-1) = -1, so the oxidation state of Ag is +1. As it is an anion, the suffix '-ate' is added to the Latin name of the metal (Argentum for Silver), followed by the oxidation state. Name: Dicyanidoargentate(I).
Which one of the following types of isomerisms is shown by [CoCl₂(en)₂]Cl ?
Asked in: UPSC Geoscientist 2024
- Optical isomerism only
- Geometrical isomerism only
- Both ionisation and geometrical isomerisms
- Both geometrical and optical isomerisms
Show answer
Answer: D. Both geometrical and optical isomerisms
The complex [CoCl₂(en)₂]⁺ is of the type [Ma₂b₂] (where 'a' is Cl and 'b' is the bidentate ligand 'en' represented by two coordination points). Such octahedral complexes can exist as cis and trans geometrical isomers. The trans isomer (where the two Cl ligands are opposite to each other) has a plane of symmetry and is optically inactive. The cis isomer (where the two Cl ligands are adjacent) lacks a plane of symmetry and is chiral, existing as a pair of enantiomers (non-superimposable mirror images), which are optically active.
Which one of the following Ni(II) complexes is diamagnetic and has tetrahedral geometry ?
Asked in: UPSC Geoscientist 2024
- [NiCl₄]²⁻
- [Ni(CO)₄]
- [Ni(NH₃)₄]²⁺
- [Ni(CN)₄]²⁻
Show answer
Answer: B. [Ni(CO)₄]
[Ni(CO)₄]: In this complex, Nickel is in the 0 oxidation state (Ni(0)). Its electron configuration is d¹⁰. All 10 d electrons are paired. The hybridization is sp³, resulting in a tetrahedral geometry. Since all electrons are paired, the complex is diamagnetic. For Ni(II) complexes (d⁸): - [NiCl₄]²⁻: Cl⁻ is a weak field ligand. Forms a tetrahedral complex (sp³ hybridization) which is paramagnetic (2 unpaired electrons). - [Ni(NH₃)₄]²⁺: NH₃ is a moderate field ligand. Can form tetrahedral (sp³, paramagnetic) or square planar (dsp², diamagnetic) complexes depending on conditions, but the tetrahedral form is paramagnetic. - [Ni(CN)₄]²⁻: CN⁻ is a strong field ligand. Forms a square planar complex (dsp² hybridization) which is diamagnetic (all electrons paired).
The number of unpaired electrons in tetrahedral [Ni(CO)₄] complex is:
Asked in: MPSC CS Prelims 2020
- 0
- 1
- 2
- 3
Show answer
Answer: A. 0
In [Ni(CO)₄], nickel is in the oxidation state of 0. The electronic configuration of Ni is [Ar] 3d⁸ 4s². Carbon monoxide (CO) is a strong field ligand. In the presence of strong field ligands like CO, the electrons in the 3d and 4s orbitals of Ni(0) pair up. The 4s electrons are promoted to the 3d orbitals, resulting in a 3d¹⁰ configuration with all electrons paired. The hybridization involved is sp³ leading to a tetrahedral geometry.
Inorganic Reaction Mechanisms
Consider the following chemical reaction : aFe₂O₃(s) + bCO(g) → cFe(s) + dCO₂ In the balanced chemical equation of the above, which of the following will be the values of the coefficients a, b, c and d respectively?
Asked in: UPSC CDS 1 2018
- 3, 2, 3, 1
- 1, 3, 2, 3
- 2, 3, 3, 1
- 3, 3, 2, 1
Show answer
Answer: B. 1, 3, 2, 3
- Balancing chemical equations involves ensuring the number of atoms of each element is the same on both the reactant and product sides. - Coefficients represent the relative number of molecules or moles involved in the reaction. - Balancing is achieved by using stoichiometric coefficients in front of the chemical formulas.
Which one of the following equations is the balanced chemical equation for the given reaction ? $\text{Fe + H}_2\text{O} \rightarrow \text{Fe}_3\text{O}_4\text{ + H}_2$
Asked in: UPSC CDS 2 2023
- $\text{Fe + 4H}_2\text{O} \rightarrow \text{Fe}_3\text{O}_4\text{ + H}_2$
- $\text{3Fe + H}_2\text{O} \rightarrow \text{Fe}_3\text{O}_4\text{ + 2H}_2$
- $\text{3Fe + 4H}_2\text{O} \rightarrow \text{Fe}_3\text{O}_4\text{ + 4H}_2$
- $\text{3Fe + 4H}_2\text{O} \rightarrow \text{Fe}_3\text{O}_4\text{ + H}_2$
Show answer
Answer: C. $\text{3Fe + 4H}_2\text{O} \rightarrow \text{Fe}_3\text{O}_4\text{ + 4H}_2$
Checking the balanced equation: Left side: Fe = 3, H = 4 2 = 8, O = 4 1 = 4 Right side: Fe = 3, H = 4 2 = 8, O = 4 The number of atoms of each element is equal on both sides.
Frederick Sanger was awarded the Nobel Prize for Chemistry twice. What was the gap between the two prizes ?
Asked in: MPSC CS Prelims 2015
- > 10 years
- < 10 years
- > 20 years
- < 20 years
Show answer
Answer: C. > 20 years
- Frederick Sanger is one of only four individuals to have won the Nobel Prize twice, and the only one to have won it twice in Chemistry. - His first prize was for protein sequencing (specifically insulin). - His second prize was for DNA sequencing methods (the Sanger method).
Paul J. Crutzen, who often used the term 'Anthropocene' and who won the Nobel Prize for Chemistry in year 1995, was a citizen of :
Asked in: MPSC CS Prelims 2021
- The Netherlands
- Germany
- France
- Poland
Show answer
Answer: A. The Netherlands
Paul J. Crutzen (1933-2021) was a Dutch atmospheric chemist. He shared the Nobel Prize in Chemistry in 1995 with Mario J. Molina and F. Sherwood Rowland for their work on the formation and depletion of stratospheric ozone. He is also widely credited with popularizing the term "Anthropocene" to denote the current geological epoch dominated by human activity.
Which one of the following is not an example of a redox reaction?
Asked in: UPSC NDA 1 2022
- AlCl₃ + 3H₂O → Al(OH)₃ + 3HCl
- 2NaH → 2Na + H₂
- 4Fe + 3O₂ → 2Fe₂O₃
- CuSO₄ + Zn → Cu + ZnSO₄
Show answer
Answer: A. AlCl₃ + 3H₂O → Al(OH)₃ + 3HCl
- A redox reaction is a chemical reaction that involves the transfer of electrons, resulting in changes in the oxidation states of atoms. - Oxidation is an increase in oxidation state (loss of electrons). - Reduction is a decrease in oxidation state (gain of electrons). - Let's analyze the oxidation states in each reaction: - A) AlCl₃ (+3, -1) + H₂O (+1, -2) → Al(OH)₃ (+3, -2, +1) + HCl (+1, -1). Oxidation states of all elements remain unchanged. - B) 2NaH (+1, -1) → 2Na (0) + H₂ (0). Na changes from +1 to 0 (reduction), H changes from -1 to 0 (oxidation). Redox. - C) 4Fe (0) + 3O₂ (0) → 2Fe₂O₃ (+3, -2). Fe changes from 0 to +3 (oxidation), O changes from 0 to -2 (reduction). Redox. - D) CuSO₄ (+2, -2) + Zn (0) → Cu (0) + ZnSO₄ (+2, -2). Cu changes from +2 to 0 (reduction), Zn changes from 0 to +2 (oxidation). Redox.
Which one of the following species is not capable of showing disproportionation reaction ?
Asked in: UPSC NDA 2 2016
- ClO⁻
- ClO₂⁻
- ClO₃⁻
- ClO₄⁻
Show answer
Answer: D. ClO₄⁻
Disproportionation is a redox reaction where an element in a specific oxidation state is simultaneously oxidized to a higher oxidation state and reduced to a lower oxidation state. For this to happen, the element must be in an intermediate oxidation state. In ClO₄⁻, Chlorine is in its highest common oxidation state of +7. It can only be reduced to a lower state (e.g., +5, +3, +1, 0, -1), but it cannot be oxidized further. Therefore, it cannot undergo disproportionation.
Consider the following redox reaction: 2Cu2O (s) + Cu2S (s) —— 6Cu (s) + SO2 (g) Identify the species among the following acting as oxidant and reductant, respectively:
Asked in: UPSC CAPF 2023
- Cu(I) and S of Cu2S
- Cu and S of SO2
- Cu and O of SO2
- Cu(I) and O of SO2
Show answer
Answer: A. Cu(I) and S of Cu2S
An oxidant (oxidizing agent) is a substance that accepts electrons and is itself reduced. A reductant (reducing agent) is a substance that donates electrons and is itself oxidized. In this reaction, Cu(I) gains electrons to become Cu(0), hence Cu(I) is the oxidant. S(-2) loses electrons to become S(+4), hence S(-2) is the reductant.
Which one of the following is a reducing substance?
Asked in: UPSC CISF AC EXE 2017
- Oxygen
- Iron
- Potassium permanganate
- Potassium dichromate
Show answer
Answer: B. Iron
A reducing substance (or reductant) is a species that loses electrons in a redox reaction, causing another substance to be reduced while itself being oxidized. Iron can readily lose electrons to form Fe²⁺ or Fe³⁺ ions, thus acting as a reducing agent.
Nuclear Chemistry
Faraday constant
Asked in: BPSC Prelims Exam 66th
- depends on the amount of the electrolyte
- depends on the current passed in the electro‐ lyte
- depends on the volume of the solvent in which the electrolyte is dissolved
- is a universal constant
Show answer
Answer: D. is a universal constant
The Faraday constant is a fundamental physical constant representing the charge of one mole of electrons.
Match List-I with List-II and select the correct answer using the code given below the Lists : List-I List-II (Element) (Application)
Asked in: UPSC CAPF 2015
- Isotope of 1. Treatment of cancer Uranium
- Isotope of Co‐ 2. Treatment of goitre balt
- Isotope of Iod‐ 3. Treatment of secondary ine cancer
- Isotope of Radi‐ 4. Nuclear fuel um Code : A B C D (a) 3 2 1 4 (b) 4 2 1 3 (c) 4 1 2 3 (d) 3 1 2 4 A. A-3, B-2, C-1, D-4 B. A-4, B-2, C-1, D-3 C. A-4, B-1, C-2, D-3 D. A-3, B-1, C-2, D-4
Show answer
Answer: C. Isotope of Iod‐ 3. Treatment of secondary ine cancer
- Isotopes of Uranium, specifically Uranium-235, are widely used as fuel in nuclear power plants because they are fissile. - Cobalt-60 is a radioactive isotope of cobalt used in radiotherapy for the treatment of cancer. - Iodine-131 is a radioactive isotope of iodine used in the treatment of goitre and thyroid cancer due to its accumulation in the thyroid gland. - Radium isotopes, particularly Radium-226, were historically used in brachytherapy (a type of radiotherapy) for treating various cancers, including secondary cancers (metastases), although its use has largely been replaced by other isotopes like Cobalt-60 or Iridium-192 due to safety concerns and availability.
Which one of the following is NOT radioactive?
Asked in: UPPCS Prelims 2001
- Astatine
- Francium
- Tritium
- Zirconium
Show answer
Answer: D. Zirconium
Astatine (At, Z=85) is the second-rarest naturally occurring element (after francium). All isotopes of astatine are short-lived and highly radioactive. Francium (Fr, Z=87) is an alkali metal. It is the most unstable of the naturally occurring elements. All isotopes of francium are highly radioactive and have very short half-lives. Tritium (³H) is a radioactive isotope of hydrogen, with a half-life of about 12.3 years. It decays by beta emission. Zirconium (Zr, Z=40) is a transition metal. Natural zirconium is composed of five stable isotopes (⁹⁰Zr, ⁹¹Zr, ⁹²Zr, ⁹⁴Zr) and one extremely long-lived radioisotope (⁹⁶Zr, half-life > 2.0 × 10¹⁹ years). In general contexts, Zirconium is considered a stable element and is used in applications like nuclear reactors due to its low neutron absorption cross-section, not its radioactivity.
Organometallic Chemistry
An example of a metal cluster is
Asked in: mineral dev officier 2025
- Fe$_{3}$(CO)$_{12}$
- Fe$_{2}$(CO)$_{9}$
- Co$_{2}$(CO)$_{8}$
- Mn$_{2}$(CO)$_{10}$
Show answer
Answer: A. Fe$_{3}$(CO)$_{12}$
A metal cluster is typically defined as a compound containing three or more metal atoms directly bonded to each other, forming a distinct metal core.
Solid State Inorganic Chemistry
Which one of the following types of glasses is used for making optical instruments?
Asked in: UPSC CDS 2 2017
- Pyrex glass
- Soft glass
- Hard glass
- Flint glass
Show answer
Answer: D. Flint glass
Flint glass is a type of optical glass characterized by a high refractive index and relatively high dispersion. It is often used in combination with crown glass (lower refractive index, lower dispersion) to make achromatic lenses that reduce chromatic aberration (the distortion caused by the different wavelengths of light being refracted at slightly different angles). These properties are crucial for the performance of optical instruments like cameras, telescopes, and microscopes.
Which one among the following statements is not true for glass ?
Asked in: UPSC CDS 2 2024
- Sodium silicate is known as water glass.
- Glass is also called super cooled liquid.
- Crystallinity develops on cooling of the molten mass of the glass.
- Coloured glasses can be made by adding different colouring materials.
Show answer
Answer: C. Crystallinity develops on cooling of the molten mass of the glass.
Glass is defined as an amorphous solid. The process of glass formation (vitrification) involves cooling a molten material rapidly enough to prevent the atoms or molecules from arranging themselves into a regular, repeating crystalline structure. If crystallization occurs during cooling, the material becomes a crystalline solid, not glass.
What are the major raw materials used in the manufacture of cement?
Asked in: UPSC Geoscientist 2022
- Limestone and clay
- Al2O3 and limestone
- Fe3O4 and clay
- Clay and MgO
Show answer
Answer: A. Limestone and clay
Cement is manufactured by heating a mixture of calcareous materials (primarily calcium carbonate from limestone) and argillaceous materials (clay or shale containing silica, alumina, and iron oxide).
Silicon carbide (SiC) is known as :
Asked in: HPPSC HPAS Prelims 2011
- Quartz
- Tridynite
- Corundum
- Carborundum
Show answer
Answer: D. Carborundum
Carborundum is a trade name that became synonymous with silicon carbide, especially the material used for grinding and polishing due to its extreme hardness. It was first synthesized by Edward Goodrich Acheson in 1893.
Which among the following are essential constituents of Portland cement ?
Asked in: UPSC NDA 1 2024
- Sand, lime, clay
- Silica, alumina, lime
- Silica, lime, graphite powder
- Sand, graphene, clay
Show answer
Answer: B. Silica, alumina, lime
The major chemical components of Portland cement clinker are tricalcium silicate (alite), dicalcium silicate (belite), tricalcium aluminate (celite), and tetracalcium aluminoferrite (ferrite). These are formed from the reaction of lime (CaO), silica (SiO2), alumina (Al2O3), and iron oxide (Fe2O3) during calcination.
What is the coordination number of Na⁺ and Cl⁻ ions in NaCl lattice ?
Asked in: UPSC NDA 1 2024
- 6, 1
- 1, 6
- 6, 6
- 5, 5
Show answer
Answer: C. 6, 6
The NaCl crystal structure is a face-centered cubic (FCC) arrangement where each Na⁺ ion is octahedrally surrounded by six Cl⁻ ions, and similarly, each Cl⁻ ion is octahedrally surrounded by six Na⁺ ions.
The setting time of cement is lowered by adding
Asked in: UPSC NDA 2 2016
- oxides of aluminium
- gypsum
- oxides of magnesium
- silica
Show answer
Answer: A. oxides of aluminium
- Setting time refers to the time required for cement paste to lose its plasticity. - Additives are used to control setting time: accelerators decrease setting time, retarders increase it. - Gypsum is a common retarder, preventing flash set by reacting with C₃A. - Oxides of aluminium are present in cement clinker primarily as tricalcium aluminate (C₃A), which hydrates rapidly and contributes to early setting. Certain forms of reactive alumina can act as accelerators.
Which one of the following statements about glass is not correct?
Asked in: UPSC NDA 2 2019
- Glass is often said to be a supercooled liquid.
- Glass has no definite melting point.
- Soda glass is harder than pyrex glass.
- Boron is present in pyrex glass.
Show answer
Answer: C. Soda glass is harder than pyrex glass.
A) Glass is an amorphous solid, lacking a long- range ordered crystalline structure. Its structure is similar to a liquid's, and it becomes increasingly viscous as it cools, without a sharp transition like freezing. Hence, it is often described as a supercooled liquid or an amorphous solid. This statement is generally considered correct. B) Due to its amorphous nature, glass does not have a specific melting point. It softens gradually over a range of temperatures. This statement is correct. C) Soda- lime glass (soda glass) is the most common type of glass (window panes, bottles). Pyrex is a brand of borosilicate glass, which contains boron oxide (B₂O₃) in addition to silica. The addition of boron oxide significantly changes the properties, making it more resistant to thermal shock and chemical corrosion, and generally harder and more resistant to scratches compared to soda-lime glass. Therefore, soda glass is not harder than pyrex glass; it is softer. D) Pyrex glass is a type of borosilicate glass, meaning it contains boron (specifically in the form of boron oxide). This statement is correct.