Chemistry — Complete Revision Notes
All 11 units in one page — atomic structure through applied chemistry. Select any line to highlight it for yourself; your highlights are saved on this device. The colour coding below follows the original notes.
| BPSC CHEMISTRY — FILE 1 Atomic Structure | Physical & Chemical Changes, Solution |
Bold ORANGE numbers = high-yield facts. RED traps = common exam mistakes. Read subtopic-by-subtopic.
| WHERE THESE QUESTIONS COME FROM BPSC/UPPSC PYQs (39th-71st) via IAS Valley Notes compilation, cross-checked against a tagged Chemistry PYQ bank (Everyday/Applied, Acids-Bases-pH, Organic subtopics), the RO/APO 2026 Science paper, NCERT Class 6-12, and the 72nd BPSC General Science book. |
1.1 Atomic Models — Scientist Timeline
In one line: Every major atomic model was built to fix a flaw in the one before it — know WHO, WHAT experiment, and WHAT limitation, in that order.
| NUMBERS TO REMEMBER Maharishi Kanad (~600 BCE, India): first to theorise 'Parmanu' — indivisible particles that combine into molecules. Democritus (5th c. BCE, Greece): coined 'atomos' (uncuttable) — all matter = tiny indivisible particles. Antoine Lavoisier (18th c., France): Father of Modern Chemistry; Law of Conservation of Mass; named C, H, O; disproved phlogiston theory. John Dalton (1808, England): Atomic Theory — atoms indivisible; same element = identical atoms; compounds form in fixed ratios. J.J. Thomson (1897/1904): discovered the electron (cathode ray tube); Plum Pudding Model — positive sphere + embedded electrons. Ernest Rutherford (1911): Gold Foil/Alpha Scattering — atom is mostly empty space; dense positive nucleus at centre; discovered proton. Niels Bohr (1913): electrons orbit in fixed energy levels/shells; absorb/emit energy only when jumping orbits; explains H spectrum only. James Chadwick (1932): bombarded beryllium with alpha particles → discovered the neutron (neutral, mass slightly > proton). Heisenberg & Schrödinger (1920s–30s): Quantum Model — electrons in probability orbitals, not fixed paths; Uncertainty Principle. |
| Model | Key Idea | Basis | Limitation |
|---|---|---|---|
| Thomson (1904) | Positive sphere + embedded e⁻ | Cathode ray tube | Could not explain gold foil results |
| Rutherford (1911) | Dense nucleus; mostly empty space | Alpha scattering | Couldn't explain why e⁻ don't fall into nucleus |
| Bohr (1913) | Fixed circular orbits (K,L,M,N) | H-atom spectrum | Fails for multi-electron atoms |
| Quantum Model | Electrons in probability orbitals (s,p,d,f) | Schrödinger wave mechanics | Mathematically complex, but most accurate |
| TRAPS — how the exam catches you Uncertainty Principle applies ONLY to microscopic particles (electrons) — NOT macroscopic objects [real PYQ, BPSC APO paper]. Rutherford's experiment discovered the nucleus AND the proton — Chadwick discovered the neutron separately, 21 years later (1932). BUT note: many official BPSC answer keys credit E. Goldstein (1886, canal ray experiment) as the discoverer of the proton, with Rutherford providing later confirmation — both framings have appeared in real papers, so recognise either. Bohr's model works well ONLY for hydrogen (single electron) — fails for multi-electron atoms; that gap is exactly what the Quantum Model fixes. Modern atomic SYMBOLS (e.g. H, O, Na) are based on the method proposed by Berzelius — not Dalton (who used circular symbols) or Bohr/Thomson [real PYQ, BPSC CDPO 2022]. |
1.2 Subatomic Particles, Electronic Configuration & Quantum Rules
In one line: Electron/proton/neutron facts plus the three filling rules (Aufbau, Hund's, Pauli) are near-guaranteed 1-2 mark BPSC questions.
| NUMBERS TO REMEMBER Max electrons per shell = 2n²: K(n=1)=2, L(n=2)=8, M(n=3)=18, N(n=4)=32. Outermost shell cannot exceed 8 (Octet Rule). Aufbau Principle: fill lowest-energy orbitals first (1s→2s→2p→3s→3p→4s→3d...). Hund's Rule: electrons occupy orbitals singly before pairing (half-filled = more stable). Pauli Exclusion Principle: max 2 electrons per orbital, with opposite spins — no two electrons share all 4 quantum numbers. Quantum numbers: n=Principal (shell), l=Azimuthal (orbital shape: s=0,p=1,d=2,f=3), m=Magnetic (orientation), s=Spin (±½). Sample configs: Na(11)=2,8,1; Cl(17)=2,8,7; Ca(20)=2,8,8,2; N(7)=2,5. Bond order: CO=3 (triple), O₂=2 (double), N₂=3, H₂=1. Higher bond order = shorter & stronger bond. Paramagnetic (unpaired e⁻, attracted to field): O₂, Fe, Mn. Diamagnetic (all paired, weakly repelled): N₂, NaCl, H₂O. Ferromagnetic (strongly attracted, retains magnetism): Fe, Co, Ni. |
| Particle | Charge | Mass | Location | Discovered By |
|---|---|---|---|---|
| Electron (e⁻) | −1 | ~0 amu (1/1840 of proton) | Outside nucleus | J.J. Thomson (1897) |
| Proton (p⁺) | +1 | ~1 amu | Inside nucleus | Rutherford (1917) |
| Neutron (n⁰) | 0 | ~1 amu (slightly > proton) | Inside nucleus | Chadwick (1932) |
| TRAPS — how the exam catches you Cathode rays travel straight, carry negative charge, and are IDENTICAL regardless of cathode material — this is what proves electrons are a universal constituent of all matter. Valency = electrons in outermost shell, OR (8 − outermost electrons) if that count exceeds 4. |
1.3 Atomic Number, Mass Number & the Isotope Family
In one line: Isotopes/Isobars/Isotones/Isoelectronic is a guaranteed match-the-definition question — anchor each to its ONE distinguishing variable.
| NUMBERS TO REMEMBER Atomic Number (Z) = protons = electrons (neutral atom). Defines the element's chemical identity. Henry Moseley (1913): each element has a unique atomic number → basis of the Modern Periodic Table. Mass Number (A) = protons + neutrons (nucleons). Neutrons (N) = A − Z. Protium (¹H): 1p, 0n. Deuterium (²H/D): 1p, 1n. Tritium (³H/T): 1p, 2n (radioactive). Hydrogen is the ONLY element with a common isotope having zero neutrons. |
| Type | Definition | Example |
|---|---|---|
| Isotopes | Same Z, different A (different neutrons) | ¹H, ²H, ³H; ²³⁵U, ²³⁸U |
| Isobars | Same A, different Z | ¹⁴C (Z=6) & ¹⁴N (Z=7); ⁴⁰Ca & ⁴⁰Ar |
| Isotones | Same number of neutrons, different Z & A | ¹⁴C (N=8) & ¹⁵N (N=8) |
| Isoelectronic | Same number of electrons | N₂ & CO (both 14e⁻); O²⁻,F⁻,Na⁺,Mg²⁺,Al³⁺ (all 10e⁻) |
| TRAPS — how the exam catches you Given e⁻=18, n=20 → mass number A = Z+N = 18+20 = 38 (protons=electrons=18) — a real, repeatedly-asked BPSC calculation. Isotopes have the SAME chemical properties (same Z) but DIFFERENT physical properties (different A/mass). |
1.4 Radioactivity & Applications of Isotopes
In one line: Alpha/Beta/Gamma properties plus the isotope-to-application matching table are two of the highest-yield sub-topics in this chapter.
| NUMBERS TO REMEMBER Radioactivity discovered by Henri Becquerel (1896); term 'radioactivity' coined by Marie Curie, who also discovered Polonium and Radium. Half-life = time for half the radioactive nuclei to decay; constant for each isotope, unaffected by temperature/pressure/chemical state. Half-lives: C-14 = 5730 yr; U-238 = 4.5 billion yr; Ra-226 = 1600 yr. Pitchblende = ore of Uranium; Marie Curie extracted Radium from pitchblende in trace amounts [39th BPSC 1994]. Atomic bomb = nuclear FISSION (splitting U-235/Pu-239). Hydrogen bomb = nuclear FUSION (uncontrolled) [67th BPSC 2022]. |
| Radiation | Nature | Charge | Penetrating Power |
|---|---|---|---|
| Alpha (α) | Helium nucleus (2p+2n) | +2 | Least — stopped by paper |
| Beta (β) | Fast electron from nucleus | −1 | Medium — stopped by Al sheet |
| Gamma (γ) | EM wave (photon) | 0 | Highest — needs lead/concrete |
| Isotope | Field | Use |
|---|---|---|
| Carbon-14 | Archaeology | Carbon dating up to ~50,000 yrs; half-life 5730 yr |
| Uranium-235 | Nuclear energy | Fission fuel — reactors & atomic bombs |
| Iodine-131 | Medicine | Thyroid cancer & hyperthyroidism treatment |
| Cobalt-60 | Medicine/Industry | Cancer radiotherapy; sterilising equipment; food irradiation |
| Sodium-24 | Medicine | Tracing blood flow, detecting clots |
| Deuterium (D₂O) | Nuclear physics | Heavy water — moderator in reactors (slows neutrons, doesn't absorb them) |
| Phosphorus-32 | Biology | Tracking DNA replication; plant phosphorus-uptake studies |
| TRAPS — how the exam catches you Alpha rays are particles (He nucleus), NOT an electromagnetic wave — a real distractor in 'which is NOT an EM wave' questions. D₂O (heavy water) = MODERATOR, not a fuel — it slows neutrons without absorbing them, sustaining a controllable chain reaction. |
2.1 States of Matter — Five States & Gas Laws
In one line: Beyond solid/liquid/gas, know Plasma (4th, most abundant in the universe) and Bose-Einstein Condensate (5th, near absolute zero) plus the gas-law formulas.
| NUMBERS TO REMEMBER Plasma (4th state): ionised matter (free ions + electrons); most abundant visible matter in the universe — Sun, stars, lightning, neon signs, fluorescent tubes. Bose-Einstein Condensate (5th state, BEC): near absolute zero (0K = −273.15°C); predicted by S.N. Bose & Einstein (1924-25); first created 1995 (Cornell, Wieman, Ketterle — Nobel 2001); all particles act as one quantum entity. Temperature conversions: K = °C + 273.15; °C = (5/9)(°F − 32). 1 mole of any gas at STP = 22.4 litres = 6.022×10²³ molecules (Avogadro's number). |
| Property | Solid | Liquid | Gas |
|---|---|---|---|
| Shape/Volume | Both definite | Volume definite only | Neither definite |
| Particle arrangement | Rigid, close-packed | Close, mobile | Far apart, random |
| Compressibility | Negligible | Slight | High |
| Kinetic energy | Least | Intermediate | Highest |
| Law | Statement | Formula |
|---|---|---|
| Boyle's Law | Constant T: V ∝ 1/P | P₁V₁ = P₂V₂ |
| Charles's Law | Constant P: V ∝ T | V₁/T₁ = V₂/T₂ |
| Gay-Lussac's Law | Constant V: P ∝ T | P₁/T₁ = P₂/T₂ |
| Avogadro's Law | Equal V, T, P → equal molecules | 1 mole gas = 22.4 L at STP |
| Ideal Gas Law | Combines all three | PV = nRT (R = 8.314 J/mol·K) |
| TRAPS — how the exam catches you Solids CANNOT flow easily — a 'which is not a solid characteristic' question tests exactly this [BPSC TRE-3 2024]. Pressure cooker: HIGH pressure → water boils ABOVE 100°C → food cooks faster. Mountains: LOW pressure → water boils BELOW 100°C → food takes longer. |
2.2 Mixtures — Solutions, Colloids & Suspensions
In one line: Particle size is the deciding variable across all three; Tyndall Effect is present ONLY in colloids — the single most-tested distinguishing fact.
| NUMBERS TO REMEMBER Tyndall Effect = scattering of light by colloidal particles (named after John Tyndall). Milk & starch solution show it; salt water (a solution) does not. Brownian motion (zig-zag movement) is seen in colloids AND suspensions — proves the particle nature of matter. |
| Feature | Solution | Colloid | Suspension |
|---|---|---|---|
| Particle size | <1 nm | 1–1000 nm | >1000 nm |
| Tyndall Effect | Absent | PRESENT | Absent |
| Settling | Stable | Stable, no settling | Settles on standing |
| Examples | Salt/sugar water | Milk, fog, blood, jelly | Muddy water, chalk-water |
| Colloid Type | Dispersed Phase | Medium | Example |
|---|---|---|---|
| Aerosol (liquid) | Liquid | Gas | Fog, mist, hairspray |
| Aerosol (smoke) | Solid | Gas | Smoke, dust |
| Foam | Gas | Liquid | Shaving cream, soap lather |
| Emulsion | Liquid | Liquid | Milk, butter, mayonnaise |
| Sol | Solid | Liquid | Milk of magnesia, blood plasma, ink |
| Gel | Liquid | Solid | Jelly, boot polish, cheese |
| TRAPS — how the exam catches you Colloids are NOT separated by ordinary filter paper — need a semipermeable membrane; suspensions ARE separated by ordinary filtration. |
2.3 Separation Techniques
In one line: Match each technique to its underlying physical PRINCIPLE — that's how BPSC phrases these questions.
| Technique | Principle | Example Use |
|---|---|---|
| Filtration | Particle size | Sand from water; water treatment |
| Evaporation | Boiling point (solid stays) | Salt from sea water |
| Distillation | Boiling point difference | Pure water from mixture |
| Fractional Distillation | Slightly different boiling points | Petroleum refining (petrol/kerosene/diesel/LPG) |
| Chromatography | Differential adsorption | Separating dyes in ink [BPSC CDPO 2022] |
| Centrifugation | Density difference, high speed | Cream from milk; washing machines [67th BPSC 2022] |
| Magnetic Separation | Magnetic property | Iron filings from sulfur |
| Sublimation | Solid→gas directly | Naphthalene, camphor, iodine, NH₄Cl, dry ice |
| Crystallization | Solubility varies with temperature | Purifying copper sulfate, alum |
| Solvent Extraction | Differential solubility, 2 solvents | Extracting iodine using CCl₄ |
• Simple physical separation methods (NCERT Class 6 level, still real PYQ material): Handpicking — removing large impurities (stones, husk) by hand. Threshing — beating stalks to separate grain seeds. Winnowing — using wind to blow away lighter chaff, leaving heavier grain. Sieving — passing through a mesh to separate by particle size. Sedimentation — heavier solid settles at the bottom when a liquid is added. Decantation — pouring off the clear liquid on top, leaving the settled solid behind.
• Desiccants (also called hygroscopic substances) absorb moisture from surroundings WITHOUT any chemical reaction — e.g. silica gel packets [real PYQ, BPSC CDPO 2022].
| TRAPS — how the exam catches you Working principle of a washing machine = Centrifugation (density-based), not filtration [67th BPSC Re-Exam 2022]. Fractional distillation ≠ plain distillation: fractional needs a fractionating column and works when boiling points are CLOSE together (e.g., petroleum fractions). |
2.4 Phase Transitions & Latent Heat
In one line: All bond-BREAKING transitions absorb heat (endothermic); all bond-FORMING transitions release heat (exothermic) — one rule covers all six transitions.
| NUMBERS TO REMEMBER Latent heat = heat absorbed/released during phase change WITHOUT temperature change. Fusion (ice): 334 J/g. Vaporization (water): 2260 J/g — this is why STEAM BURNS are more severe than hot-water burns. Water's anomalous expansion: EXPANDS on freezing (ice less dense than water); maximum density at 4°C; ice floats and insulates aquatic life in winter — due to hydrogen bonding. Dry ice = solid CO₂; sublimes at −78.5°C at 1 atm; used in food preservation, fog effects, refrigerant, dry cleaning. Evaporation (surface only, any temperature, causes cooling) vs Boiling (throughout liquid, fixed boiling point, no cooling effect). |
| Transition | Direction | Heat Change |
|---|---|---|
| Melting (Fusion) | Solid → Liquid | Absorbed |
| Freezing | Liquid → Solid | Released |
| Vaporization (Boiling) | Liquid → Gas | Absorbed |
| Condensation | Gas → Liquid | Released |
| Sublimation | Solid → Gas directly | Absorbed |
| Deposition | Gas → Solid directly | Released |
• Triple point of water = the exact temperature-pressure combination where solid, liquid and gas coexist in equilibrium: 273.16 K (0.01°C) and 611.657 Pa — used as a reference point for temperature calibration [real PYQ, 67th BPSC].
• Hygrometer = instrument used to measure humidity/moisture content in air [real PYQ, 64th BPSC].
• Viscosity = a fluid's resistance to flow; honey has the highest viscosity among common liquids [real PYQ, 66th BPSC].
• Dissolved solutes change water's boiling/freezing point: adding SALT raises the boiling point and lowers the freezing point; adding METHYL ALCOHOL (methanol) LOWERS the boiling point — both via weakened hydrogen bonding [real PYQ, 67th BPSC Re-Exam 2022].
• For an IDEAL solution (two liquids mixing with no molecular interaction), the enthalpy of mixing must be ZERO [real PYQ, 70th BPSC Re-Exam 2024].
| TRAPS — how the exam catches you Increasing pressure RAISES boiling point (pressure cooker); decreasing pressure LOWERS it (mountains) — commonly reversed by test-takers. Liquefaction of a gas needs LOW temperature + HIGH pressure together — pick one condition wrong and the gas won't liquefy [real PYQ, 70th BPSC 2024]. |
2.5 Physical vs Chemical Changes
In one line: The test is simple — did a NEW substance form? If yes, chemical. A few 'tricky examples' below are BPSC's favourite way to test this.
| NUMBERS TO REMEMBER Law of Conservation of Mass (Lavoisier): total mass of reactants = total mass of products; atoms are rearranged, never created or destroyed. Law of Definite (Constant) Proportions (Joseph Proust): in a given compound, elements are always present in a fixed mass ratio — e.g. water is always H:O = 1:8 by mass; ammonia is always N:H = 14:3 by mass. Law of Multiple Proportions (Dalton, 1803): when two elements combine to form MORE THAN ONE compound, the masses of one element that combine with a fixed mass of the other are in a ratio of small whole numbers. Dalton's atomic theory successfully explains all three laws — conservation of mass, definite proportions, AND multiple proportions [real PYQ, 70th BPSC 2024] — but NOT the law of radioactivity, which doesn't exist as a law of chemical combination. |
| Feature | Physical Change | Chemical Change |
|---|---|---|
| New substance? | No | Yes |
| Reversibility | Generally reversible | Generally irreversible |
| Signs | State/shape/size change only | Colour change, gas, precipitate, heat/light |
• Burning a candle = BOTH: melting wax (physical) + combustion of wax (chemical).
• Blackening of silverware = Chemical (Ag + H₂S → Ag₂S).
• Boiling of water = Physical (still H₂O) — a real, repeated BPSC answer [65th BPSC Re-Exam 2020].
• Rusting of iron = Chemical (new compound Fe₂O₃·xH₂O formed).
• Dissolving salt/sugar in water = Physical (recoverable by evaporation); dissolving CO₂ in water = Chemical (forms H₂CO₃).
• Electrolysis of water = Chemical/decomposition reaction (H₂O → H₂ + O₂) [BPSC BAO 2024].
2.6 Types of Chemical Reactions
In one line: Six named reaction types, one memory hook each — this table alone answers most 'identify the reaction type' questions.
| NUMBERS TO REMEMBER OIL RIG: Oxidation Is Loss (of e⁻)/gain of O; Reduction Is Gain (of e⁻)/loss of O. Oxidizing agent gets reduced; reducing agent gets oxidized. Exothermic (heat released): combustion, neutralization, respiration, rusting, dissolving H₂SO₄. Endothermic (heat absorbed): photosynthesis, thermal decomposition (CaCO₃→CaO+CO₂), dissolving NH₄Cl. Thermite reaction: Fe₂O₃ + 2Al → Al₂O₃ + 2Fe + heat — highly exothermic; used to weld railway tracks; Al is a stronger reducing agent than Fe. Lime water test for CO₂: Ca(OH)₂ + CO₂ → CaCO₃↓ (milky); excess CO₂ → Ca(HCO₃)₂ (soluble, clears again). Rancidity = oxidation of fats/oils; prevented by antioxidants (BHA, BHT, Vit C/E), N₂ gas packaging (chips packets), refrigeration, air-tight/vacuum packaging. |
| Type | Pattern | Example |
|---|---|---|
| Combination | A+B → AB | 2Mg + O₂ → 2MgO |
| Decomposition | AB → A+B | 2H₂O → 2H₂ + O₂ (electrolysis) |
| Single Displacement | More reactive replaces less reactive | Fe + CuSO₄ → FeSO₄ + Cu |
| Double Displacement | Ion exchange, often precipitate | AgNO₃ + NaCl → AgCl↓ + NaNO₃ |
| Combustion | Fuel + O₂ → CO₂+H₂O+energy | CH₄ + 2O₂ → CO₂ + 2H₂O |
| Neutralization | Acid+Base → Salt+Water (exothermic) | HCl + NaOH → NaCl + H₂O |
| TRAPS — how the exam catches you ALWAYS add acid to water, NEVER water to acid — diluting H₂SO₄ is highly exothermic and can cause dangerous spattering [NCERT Class 10]. In a soda-acid fire extinguisher: dilute H₂SO₄ + sodium bicarbonate (NaHCO₃) [70th BPSC Pre 2024] — a repeatedly tested composition fact. Faraday constant is a UNIVERSAL constant (~96,485 coulombs per mole) — it does NOT depend on the electrolyte, the current passed, or the solvent volume [real PYQ, 66th BPSC 2020]. It equals the total charge carried by one mole of electrons. Reduction (gain of electrons/hydrogen or loss of oxygen) happens in photosynthesis too: CO₂ is REDUCED to carbohydrates using energy from sunlight — a real, counter-intuitive PYQ pairing [BPSC Teacher exam]. |
— END —
| BPSC CHEMISTRY — FILE 2 Inorganic Chemistry | Metals, Minerals, Ores |
Bold ORANGE numbers = high-yield facts. RED traps = common exam mistakes. Read subtopic-by-subtopic.
| WHERE THESE QUESTIONS COME FROM BPSC/UPPSC PYQs (39th-71st) via IAS Valley Notes compilation, cross-checked against a tagged Chemistry PYQ bank, the RO/APO 2026 Science paper, NCERT Class 6-12, and the 72nd BPSC General Science book. |
3.1 Periodic Table — Historical Development
In one line: Four names, four attempts — each fixed a flaw in the last. Mendeleev arranged by MASS; Moseley (Modern table) by ATOMIC NUMBER — the single most-tested contrast here.
| NUMBERS TO REMEMBER Modern Periodic Table: 18 groups, 7 periods, 118 elements. Longest period = 6th (32 elements). Shortest = 1st (2 elements: H, He). Mendeleev's predictions: Eka-boron = Scandium, Eka-aluminium = Gallium, Eka-silicon = Germanium. |
| Scientist | Year | Contribution / Limitation |
|---|---|---|
| Dobereiner | 1817 | Law of Triads — 3rd element's properties between first two (Li-Na-K). Couldn't classify all elements. |
| John Newlands | 1866 | Law of Octaves — every 8th element similar (musical octaves). Worked only for first 17 elements. |
| Dmitri Mendeleev | 1869 | Arranged 63 elements by increasing ATOMIC MASS; predicted undiscovered elements (Eka-boron=Sc, Eka-silicon=Ge); left gaps. |
| Henry Moseley | 1913 | Modern Periodic Law — properties are a periodic function of ATOMIC NUMBER, not mass. Basis of today's table. |
| TRAPS — how the exam catches you Mendeleev's table could not explain the position of isotopes and placed Hydrogen awkwardly with the halogens — this exact gap is what atomic-number-based Moseley table fixed. |
3.2 Periodic Table — Blocks, Groups & Trends
In one line: Memorise the AIEM trend rule once — it answers every 'across period vs down group' question in one shot.
| NUMBERS TO REMEMBER AIEM memory hook: Atomic radius, Ionization energy, Electronegativity, Metallic character — across a period: radius↓ IE↑ EN↑ metallic↓; down a group, all reverse. Fluorine (F) = most electronegative element (4.0, Pauling scale). Noble gases = highest ionization energy in each period. Smallest atom = Hydrogen; largest naturally occurring = Francium. Most abundant metal in crust = Aluminium (8.1%). Most abundant element in crust = Oxygen (46.6%), then Silicon (27.7%). Most abundant gas in atmosphere = Nitrogen (78%). Radon = rarest noble gas, NOT normally present in air (unlike He, Ne, Ar, Kr, Xe). |
| Block | Groups | Key Elements |
|---|---|---|
| s-block | 1, 2 | H, He, Li, Na, K, Be, Mg, Ca — alkali & alkaline earth metals |
| p-block | 13–18 | B, C, N, O, F, Cl, noble gases |
| d-block | 3–12 | Transition metals: Sc→Zn etc. |
| f-block | bottom rows | Lanthanides (Ce–Lu) & Actinides (Th–Lr) — all actinides radioactive |
| Group | Name | Key Property |
|---|---|---|
| 1 | Alkali Metals | 1 valence e⁻; soft; stored in kerosene (Na, K) |
| 2 | Alkaline Earth Metals | 2 valence e⁻; Ca in bones/teeth |
| 17 | Halogens | 7 valence e⁻; most reactive non-metals; F = most electronegative |
| 18 | Noble Gases | Complete outer shell; chemically inert |
| Property | Across Period (L→R) | Down Group (Top→Bottom) |
|---|---|---|
| Atomic Radius | Decreases | Increases |
| Ionization Energy | Increases | Decreases |
| Electronegativity | Increases | Decreases |
| Metallic Character | Decreases | Increases |
| TRAPS — how the exam catches you Mercury (Hg) = only liquid METAL at room temperature. Bromine (Br) = only liquid NON-metal at room temperature — a classic pairing trap. Iodine is the only non-metal with metallic lustre — don't confuse with Bromine (liquid, not lustrous). |
3.3 Metals vs Non-metals vs Metalloids
In one line: Metalloids (semiconductors) sit between the two extremes — B, Si, Ge, As, Sb, Te, Po is the full list BPSC expects you to know cold.
| NUMBERS TO REMEMBER Metalloids/semimetals: Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium, Polonium. Silicon & Germanium = most important semiconductors (transistors, chips, solar cells). |
| Property | Metals | Non-metals | Metalloids |
|---|---|---|---|
| Lustre | Shiny (except non-lustrous few) | None (except Iodine) | Semi-metallic |
| Malleability | Malleable, ductile | Brittle | Brittle |
| Conduction | Good (Ag best) | Poor (except graphite) | Semiconductors |
| Oxide nature | Basic | Acidic | Amphoteric |
| Electron tendency | Lose e⁻ (electropositive) | Gain e⁻ (electronegative) | Either |
3.4 Reactivity Series & Metal Reactions
In one line: One ordered list explains almost every metal-reaction question — memorise it once, apply it everywhere.
| NUMBERS TO REMEMBER Reactivity series (most → least reactive): K > Na > Ca > Mg > Al > Zn > Fe > Pb > (H) > Cu > Hg > Ag > Pt > Au. Most reactive metal = Potassium (K); least reactive = Gold (Au). Metals above hydrogen displace it from dilute acids. K, Na, Ca: react violently with COLD water. Mg: reacts with HOT water. Al, Zn, Fe: react only with STEAM. Cu, Pb: no reaction with water/dilute acid. Au, Ag, Pt: noble metals — unreactive even with hot conc. acids; only Aqua Regia dissolves Au/Pt. Aqua Regia = 1 part conc. HNO₃ + 3 parts conc. HCl (by volume) — the only mixture that dissolves gold and platinum. |
| Metal | With Air/O₂ | With Water | With Dilute Acid |
|---|---|---|---|
| K, Na | Catch fire; kept in kerosene | Violent — MOH + H₂ | Violent |
| Mg | Burns, dazzling white flame | Only hot water/steam | Readily: MgCl₂ + H₂ |
| Al, Zn, Fe | Oxide layer on heating | Only steam | Readily |
| Cu | Blackens (CuO) | No reaction | No reaction |
| Au, Ag, Pt | No reaction | No reaction | No reaction (only Aqua Regia dissolves Au/Pt) |
| TRAPS — how the exam catches you Al and Zn are AMPHOTERIC metals — they react with BOTH acids and bases, releasing H₂ gas in either case. Purest form of iron = Wrought iron (lowest carbon content) — not cast iron (most brittle) or steel (most used) [BPSC CDPO 2018]. Food cans are coated with TIN, not zinc, because zinc is MORE reactive than tin (the opposite of the intuitive guess) [real PYQ, BPSC Teacher & TRE-3 2024]. Noble metals (Au, Ag, Pt) are found in PURE/native form in nature — Uranium and Lead are NOT noble metals, a real distractor pairing [BPSC Re-Exam 2022]. The MORE NEGATIVE a metal's standard electrode potential, the STRONGER its reducing power — a real PYQ ranked three metals purely by their electrode-potential values using this rule [70th BPSC Re-Exam 2024]. When iron rusts, its weight actually INCREASES (oxygen is added to form Fe₂O₃·nH₂O) — per BPSC's own official answer key, this is the accepted answer even though flaking rust can reduce weight over a very long time [real PYQ, 67th BPSC Re-Exam 2022]. |
3.5 Corrosion — Rusting, Tarnishing & Prevention
In one line: Rusting/tarnishing are slow oxidation (chemical change) — the prevention methods table is the exam-relevant half of this topic.
| Method | How it Works | Example |
|---|---|---|
| Galvanization | Zn coating; Zn = sacrificial anode | Pipes, buckets, roofing sheets |
| Electroplating | Protective metal layer via electrolysis | Cr on steel, Sn on cans |
| Alloying | Corrosion-resistant elements added | Cr in stainless steel (self-healing Cr₂O₃) |
| Anodization | Thickens natural oxide layer | Aluminium cookware, aircraft parts |
• Rusting of iron: Fe + O₂ + H₂O → Fe₂O₃·xH₂O (hydrated iron oxide, red-brown).
• Green patina on copper: Cu + CO₂ + H₂O → CuCO₃·Cu(OH)₂ (basic copper carbonate).
• Tarnishing of silver: Ag + H₂S → Ag₂S (silver sulfide, black) — real PYQ: silver ornaments blacken due to atmospheric H₂S, NOT oxygen [BPSC APO paper].
| TRAPS — how the exam catches you Galvanized (zinc-coated) pots are UNSUITABLE for storing oil/fatty/acidic food — the zinc coating reacts with free fatty acids/moisture to form toxic zinc salts, both spoiling the food and corroding the pot [real PYQ, 71st BPSC]. |
4.1 Ores & Minerals — Concepts + Master Ore Table
In one line: Ore = mineral that's PROFITABLE to extract metal from — all ores are minerals, not all minerals are ores. The metal↔ore table is pure recall; learn it as pairs.
| NUMBERS TO REMEMBER Gangue = impurities in ore (sand, rock, clay) removed during extraction. Crust abundance order: Oxygen(46.6%) > Silicon(27.7%) > Aluminium(8.1%) > Iron(5.0%) > Calcium(3.6%) > Sodium(2.8%) > Potassium(2.6%) > Magnesium(2.1%). Main ingredient in cement manufacture = Limestone [real PYQ, 67th BPSC 2022]. Other major iron ores beyond Haematite/Magnetite: Limonite (FeO(OH)·nH2O) and Siderite (FeCO₃) [real PYQ, 42nd BPSC]. |
| Metal | Principal Ore(s) | Formula |
|---|---|---|
| Aluminium | Bauxite | Al₂O₃·2H₂O |
| Iron | Haematite / Magnetite | Fe₂O₃ / Fe₃O₄ |
| Copper | Copper pyrites (Chalcopyrite) | CuFeS₂ |
| Zinc | Zinc blende (Sphalerite) | ZnS |
| Lead | Galena | PbS |
| Mercury | Cinnabar | HgS |
| Tin | Cassiterite | SnO₂ |
| Titanium | Ilmenite / Rutile | FeTiO₃ / TiO₂ |
| Thorium | Monazite | mixed phosphates |
| Uranium | Pitchblende / Carnotite | UO₂ |
| Silver | Argentite | Ag₂S |
| Gold | Native gold | Au (free state) |
• Blue vitriol = Copper sulfate (CuSO₄·5H₂O) — white when anhydrous, blue when hydrated; dissolves in water, insoluble in alcohol [real PYQ, 63rd BPSC 2017].
• Technetium (Tc, atomic number 43) is the first artificially prepared element — isolated in 1937 by Carlo Perrier and Emilio Segrè [real PYQ, 70th BPSC 2024].
• Sapphire and Ruby share the chemical formula Al₂O₃ (crystalline aluminium oxide, corundum) — colour differences come from trace impurities [real PYQ, 66th BPSC Re-Exam 2020].
• Electrical conductivity order among common metals (highest to lowest): Silver > Copper > Gold > Aluminium > Beryllium > Calcium [real PYQ, 65th BPSC Re-Exam 2020].
• By DENSITY, Platinum (~21.45 g/cm³) is the 'heaviest' common metal — denser than Gold (19.32), Mercury (13.54) and Silver (10.5). A separate real PYQ instead asked for the heaviest metal by comparing Uranium, Copper, Aluminium and Silver, and accepted Uranium (atomic mass 238) — recognise BOTH framings ('heaviest' can mean density OR atomic mass depending on the options given).
| TRAPS — how the exam catches you Galena (PbS) is the ore of LEAD, not aluminium — a real PYQ distractor asking 'which is NOT an ore of aluminium' [ScienceMCQ bank]. Aluminium's real ores/minerals: Bauxite (main), Corundum, Feldspar, Kaolinite (China clay). Al₂O₃·2SiO₂·2H₂O is the formula of China clay (Kaolinite), not bauxite [BPSC School Teacher 2023]. Zinc blende (ZnS) is a good conductor of heat and electricity — an often-missed exception. Four real aluminium ores with formulas, all fair game: Bauxite (Al₂O₃·2H₂O), Cryolite (Na₃AlF₆), Corundum (Al₂O₃), Diaspore (AlO(OH)) [real PYQ, 70th BPSC 2024 — corundum AND cryolite both confirmed as aluminium ores]. Non-ferrous metallic minerals contain NO iron (e.g. cobalt, tin, copper, zinc). Ferrous metallic minerals DO contain iron — but note manganese, nickel and chromium are also classed as ferrous-associated/alloying minerals in BPSC's own answer key framing [real PYQ, 65th BPSC Re-Exam 2020]. |
4.2 Metallurgy — Extraction Steps
In one line: Four steps in fixed order: Concentration → Oxide conversion → Reduction → Refining. Match reduction METHOD to metal REACTIVITY.
| NUMBERS TO REMEMBER Step 1 (Concentration/Ore Dressing): crushing/grinding, magnetic separation, froth flotation (sulphide ores), gravity separation, leaching. Step 2 (Conversion to oxide): Roasting = heating sulphide ore in EXCESS air (ZnS+O₂→ZnO+SO₂). Calcination = heating carbonate ore in LIMITED air (ZnCO₃→ZnO+CO₂). Step 3 (Reduction) — Smelting is specifically defined as the process where a metal is obtained in a FUSED/molten state via high-temperature reduction of the ore [real PYQ, 67th BPSC Re-Exam 2022]. Step 4 (Refining): Electrolytic refining (impure=anode, pure=cathode) for Cu/Ag/Au. Distillation for volatile metals (Zn, Hg). Zone refining for ultra-pure semiconductors (Si, Ge). Electroplating a vessel with zinc: the VESSEL is made the negative pole (cathode) and PURE ZINC is made the positive pole (anode) — zinc loses electrons to become a cation and deposits onto the vessel [real PYQ, 46th BPSC]. |
| Reactivity | Reduction Method | Example |
|---|---|---|
| Less reactive (Hg, Ag) | Heat alone | 2HgO → 2Hg + O₂ |
| Medium (Zn, Fe, Cu, Pb) | Carbon/CO reduction (smelting) | Fe₂O₃ + 3CO → 2Fe + 3CO₂ |
| Fe (special case) | Thermite/Displacement | Fe₂O₃ + 2Al → Al₂O₃ + 2Fe |
| Highly reactive (Na,Ca,Mg,Al) | Electrolytic reduction | Molten NaCl → Na; molten Al₂O₃ (in cryolite) → Al |
4.3 Bihar/India Mineral Geography
In one line: A recurring 'state + mineral' question set — Jaduguda (India's only uranium mine) and Monazite (Kerala coast) are the two highest-value facts here.
• Iron ore: Jharkhand (Singhbhum). Coal: Jharia, Bokaro (Jharkhand). Mica: Jharkhand/Bihar.
• Uranium: Jaduguda, Jharkhand — India's ONLY uranium mine.
• Monazite (thorium ore): Kerala coast — a nuclear-fuel-relevant sand deposit.
• Iron ore belts elsewhere: Bababudan Hills (Karnataka), Dhalli-Rajhara Range (Chhattisgarh), Noamundi (Jharkhand) [real RO Prelims 2026 PYQ — Kemmangundi is in Karnataka, NOT Odisha, a common trap].
4.4 Calcium Compounds — Family Table
In one line: One reaction chain — limestone → quicklime → slaked lime → lime water/POP/bleaching powder — connects this entire family; learn the chain, not isolated facts.
| NUMBERS TO REMEMBER Lime water CO₂ test: Ca(OH)₂ + CO₂ → CaCO₃↓ (milky); excess CO₂ → Ca(HCO₃)₂ (clear again). POP sets by REHYDRATING: CaSO₄·½H₂O + 1½H₂O → CaSO₄·2H₂O (gypsum) — and EXPANDS slightly on setting, which is exactly why it's used for dental moulds/fracture casts. |
| Compound | Formula | Prep / Key Use |
|---|---|---|
| Limestone (Calcite) | CaCO₃ | Cement, glass, steel flux |
| Quicklime | CaO | CaCO₃ → CaO + CO₂ (calcination) |
| Slaked lime | Ca(OH)₂ | CaO + H₂O → Ca(OH)₂ (exothermic); bleaching powder, whitewashing |
| Gypsum | CaSO₄·2H₂O | Raw material for Plaster of Paris |
| Plaster of Paris | CaSO₄·½H₂O | Gypsum heated at 120-130°C; fracture casts |
| Bleaching Powder | CaOCl₂ | Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O; disinfectant |
| TRAPS — how the exam catches you Plaster of Paris is NOT slaked lime — a very common trick question. POP = CaSO₄·½H₂O; slaked lime = Ca(OH)₂. Bleaching powder is poorly SOLUBLE in water — a 'which is NOT true' PYQ tests exactly this [39th BPSC 1994]. It releases Cl₂ gas on reaction with dilute acid. |
4.5 Sodium Compounds & Water Hardness
In one line: Baking soda vs baking powder vs washing soda is a guaranteed compare-and-contrast question — know what each ADDITIONALLY contains and why.
| NUMBERS TO REMEMBER Chlor-alkali process: NaCl(aq) --electrolysis--> NaOH + Cl₂ + H₂. Products: NaOH (caustic soda), Cl₂ (bleaching powder/PVC/antiseptics), H₂ (fuel/margarine) [NCERT Class 10]. Baking Powder = NaHCO₃ + tartaric acid + starch — the acid neutralises the bitter Na₂CO₃ taste that baking soda alone would leave behind. |
| Compound | Formula | Common Name |
|---|---|---|
| Sodium chloride | NaCl | Table/Rock salt |
| Sodium hydroxide | NaOH | Caustic soda |
| Sodium carbonate | Na₂CO₃·10H₂O | Washing soda |
| Sodium bicarbonate | NaHCO₃ | Baking soda |
| Sodium sulphate | Na₂SO₄·10H₂O | Glauber's salt |
| Sodium thiosulphate | Na₂S₂O₃·5H₂O | Hypo (photography fixer) |
| Borax | Na₂B₄O₇·10H₂O | Tincar |
| Hardness Type | Cause | Removal |
|---|---|---|
| Temporary | Ca(HCO₃)₂, Mg(HCO₃)₂ | Boiling; Clark's method [Ca(OH)₂] |
| Permanent | CaSO₄, MgSO₄, CaCl₂, MgCl₂ | Washing soda (Na₂CO₃); ion exchange/zeolite; distillation |
4.6 Glass Types & Other Key Inorganic Compounds
In one line: Glass composition determines its use — swap one oxide (Pb for Ca, or add B₂O₃) and you get an entirely different glass.
| Glass Type | Composition | Use |
|---|---|---|
| Soda glass | Na₂O+CaO+SiO₂ | Windows, bottles |
| Pyrex (borosilicate) | SiO₂+B₂O₃+Al₂O₃+Na₂O | Lab glassware — low thermal expansion |
| Optical (flint) glass | SiO₂+PbO+K₂O | Lenses, prisms — high refractive index (Pb) |
| Safety glass | 2 glass sheets + plastic layer | Car windshields |
| Compound | Formula | Key Fact |
|---|---|---|
| Sulphuric acid | H₂SO₄ | 'King of Chemicals'; most-produced industrial chemical; never add water to it — always acid to water |
| Ammonia | NH₃ | Haber process: N₂+3H₂⇌2NH₃ (Fe catalyst, 450°C, 200 atm) |
| Hydrogen peroxide | H₂O₂ | Bleaching agent; 3% solution = antiseptic; oxidising agent |
| Nitrous oxide | N₂O | 'Laughing gas'; medical anaesthetic; whipped-cream propellant |
• White lead (commercial name 'Safeda') = basic/alkaline lead carbonate, formula 2PbCO₃·Pb(OH)₂ [real PYQ, BPSC 11th-12th 2023].
• CaO (quicklime) is SOLUBLE in water (reacts to form Ca(OH)₂) — but FeO and ZnO are NOT soluble in water [real PYQ, BPSC TRE-3 2024].
• Zinc Oxide (ZnO) is used across rubber, plastic, ceramics, glass, cement, paints, ointments, food products, batteries, and even secondarily in solvents and explosives — a much broader use-list than most students expect [real PYQ, BPSC TRE-3 2024].
• Manganese is used in match manufacturing, leather processing, photography-related materials, and dry battery production — India's top manganese-ore states are Madhya Pradesh, Maharashtra, Odisha, Karnataka and Andhra Pradesh [real PYQ, BPSC TRE-3 2024].
• In lab-grown diamonds (LGD), Graphite is used as the diamond 'seed' (via the HPHT or Chemical Vapour Deposition method) — Moissanite/White Sapphire/Cubic Zirconia are themselves diamond SIMULANTS, not the seed material used to grow real lab diamonds [real PYQ, 70th BPSC Re-Exam 2024].
— END —
| BPSC CHEMISTRY — FILE 3 Alloys | Non-metals (Carbon, Hydrogen, S/N/Halogens/Inert Gases, Acid-Base-Salt) |
Bold ORANGE numbers = high-yield facts. RED traps = common exam mistakes. Read subtopic-by-subtopic.
| WHERE THESE QUESTIONS COME FROM BPSC/UPPSC PYQs (39th-71st) via IAS Valley Notes compilation, cross-checked against a tagged Chemistry PYQ bank, the RO/APO 2026 Science paper, NCERT Class 6-12, and the 72nd BPSC General Science book. |
5.1 Alloys — Master Table & Carat System
In one line: Alloys = homogeneous mixtures of metals made harder, more corrosion-resistant, or lower-melting than the pure metal — German Silver is the single most-repeated trick fact in this topic.
| NUMBERS TO REMEMBER 24 carat = pure gold (100%, too soft for jewellery). 22 carat = 91.7% gold. 18 carat = 75% gold. 14 carat = 58.3% gold. |
| Alloy | Components | Use |
|---|---|---|
| Brass | Cu + Zn | Utensils, musical instruments, cartridges |
| Bronze | Cu + Sn | Statues, coins, bells, medals |
| Steel | Fe + C (<2%) | Buildings, bridges, vehicles |
| Stainless Steel | Fe+C+Cr+Ni+Mn | Cutlery, surgical tools; Cr = corrosion-resistant |
| Duralumin | Al+Cu+Mn+Mg | Aircraft bodies — light yet strong |
| Solder | Sn 60% + Pb 40% | Joining electrical wires; low melting point |
| Fuse wire | Sn 63% + Pb 37% | Electrical fuses; melts on overload |
| German Silver | Cu+Zn+Ni (NO silver) | Ornaments, cutlery |
| Gun Metal | Cu+Zn+Sn | Guns, valves, gears |
| Nichrome | Ni 80% + Cr 20% | Heater coils, electric irons — high resistivity |
| Amalgam | Hg + any metal | Dental fillings (Ag-Sn-Hg) |
| Magnalium | Mg + Al | Aircraft frames — very light |
| TRAPS — how the exam catches you German Silver contains NO silver at all — it's Cu+Zn+Ni. Extremely common BPSC/UPPSC trick question. Fuse wire and Solder have the SAME two components (Sn+Pb) but DIFFERENT proportions — don't confuse them. 'White metal' is itself an alloy — usually Lead + Tin (sometimes with cadmium, bismuth, zinc) [real PYQ, 67th BPSC Re-Exam 2022]. Gold and Platinum do NOT corrode at all [real PYQ, BPSC BAO 2024] — the two 'noble' metals immune to atmospheric attack. |
6.1 Non-metals — Allotropes of Carbon
In one line: Diamond and graphite are BOTH pure carbon — the only difference is atomic arrangement, and that arrangement alone explains every property difference.
| NUMBERS TO REMEMBER Graphite conducts electricity because each carbon has ONE delocalized (free-moving) π electron. Diamond does NOT conduct — all 4 electrons are locked in bonds, none free. Graphite is also used as a MODERATOR in nuclear reactors, just like heavy water (D₂O) — both slow down neutrons. The purest form of amorphous carbon is Lamp black — NOT wood/sugar/bone charcoal (which are all impure amorphous carbon forms) [real PYQ, BPSC CDPO 2022]. |
| Allotrope | Structure | Key Property |
|---|---|---|
| Diamond | 3D tetrahedral (sp³), each C bonded to 4 others | Hardest natural substance; poor conductor |
| Graphite | Layered hexagonal (sp²), weak inter-layer bonds | Soft, slippery; GOOD conductor of electricity |
| Fullerene (C₆₀) | Soccer-ball structure, 60 C atoms | Molecular solid; used in nanotechnology, drug delivery |
| Graphene | Single layer of graphite (2D) | Strongest known material; excellent conductor |
| Coal/Coke | Amorphous, no regular structure | Fuel; coke used in steel manufacturing |
6.2 Non-metals — Hydrogen and its Compounds
In one line: Hydrogen is unique — one electron, one proton, placed in Group 1 but chemically resembling both alkali metals and halogens.
| NUMBERS TO REMEMBER Most abundant element in the universe (mostly combined, as water/hydrocarbons on Earth). Lab preparation: Zn + dilute H₂SO₄ → ZnSO₄ + H₂↑. Industrial: electrolysis of water; steam reforming of natural gas. Properties: colourless, odourless, lightest gas known, highly flammable, burns with a pale blue flame; 2H₂ + O₂ → 2H₂O. Isotopes: Protium (¹H, 1p 0n), Deuterium (²H/D, 1p 1n), Tritium (³H/T, 1p 2n, radioactive) — hydrogen is the ONLY element whose common isotope (protium) has zero neutrons. Uses: hydrogenation of vegetable oils (making vanaspati/margarine — Ni catalyst), ammonia manufacture (Haber process), rocket fuel, fuel cells, oxy-hydrogen welding. Hydrogen has the highest calorific value of any fuel (~1,50,000 kJ/kg) and zero carbon emission — central to the emerging 'Hydrogen Economy'. Hydrogen storage methods: physically by high-pressure compression (gas cylinders), or chemically by absorption into metal hydrides (Pd, Pt readily absorb/occlude hydrogen gas). 'Colours' of hydrogen (by production method): Green H₂ = electrolysis using renewable power (zero emission). Grey H₂ = steam methane reforming of natural gas (the MOST common industrial method today, but releases CO₂ — NOT green despite hydrogen itself being clean-burning). Blue H₂ = grey process + carbon capture. |
| TRAPS — how the exam catches you Helium, not hydrogen, is used to fill weather/party balloons DESPITE hydrogen being lighter — because hydrogen forms an explosive mixture with air, while helium is inert [real BPSC APO PYQ]. D₂O (heavy water, made from deuterium) is used as a nuclear reactor MODERATOR — not as a fuel. Hydrofluoric acid (HF) is NEVER stored in glass bottles — it reacts with and etches the SiO₂ in glass. Stored in wax/plastic/polyethylene containers instead. Oxy-acetylene (not oxy-hydrogen) is the gas combination most commonly used for welding/cutting metal in real BPSC PYQs — oxy-hydrogen welding exists but is asked far less often. |
6.3 Non-metals — Sulphur and its Compounds
In one line: The Contact Process (making H₂SO₄ from sulphur) is the highest-yield fact here — know the 3-step chain, not just the final product.
| NUMBERS TO REMEMBER Allotropes: Rhombic sulphur (α-sulphur) — yellow, stable at room temperature. Monoclinic sulphur (β-sulphur) — stable only above 96°C. Occurrence: native sulphur deposits (e.g., Sicily); sulphide ores — iron pyrites (FeS₂), galena (PbS), zinc blende (ZnS), copper pyrites (CuFeS₂); gypsum (CaSO₄·2H₂O). Contact Process (industrial H₂SO₄ manufacture): S + O₂ → SO₂; 2SO₂ + O₂ --(V₂O₅ catalyst, ~450°C)--> 2SO₃; SO₃ + H₂SO₄ → Oleum; Oleum + H₂O → H₂SO₄. H₂SO₄ = 'King of Chemicals' — highest-volume industrial chemical produced worldwide; used in fertilizers, batteries, detergents, dyes. SO₂: colourless, pungent gas; used as a bleaching agent (in presence of moisture) and as a food preservative (sulphiting); also the MAIN cause of acid rain when it oxidises to H₂SO₄ in the atmosphere. |
| TRAPS — how the exam catches you NEVER add water to concentrated H₂SO₄ — always add acid to water. Dilution is highly exothermic and can cause dangerous spattering. |
6.4 Non-metals — Nitrogen, Halogens & Inert Gases
In one line: Nitrogen is inert due to its N≡N triple bond; halogens get LESS reactive down the group; noble gases are inert because their outer shell is already full — three different reasons for three different kinds of 'unreactive'.
| NUMBERS TO REMEMBER Nitrogen (N₂) = 78% of atmosphere; the N≡N triple bond makes it chemically very stable/inert at room temperature. Fixed naturally by lightning and by Rhizobium bacteria (legume root nodules); industrially by the Haber process. Halogen reactivity DECREASES down the group: F > Cl > Br > I (opposite of the metal reactivity trend, since halogens gain electrons rather than lose them). Noble gas uses: Helium — balloons/airships (safe, non-flammable), deep-sea diving gas mixtures, MRI/cryogenics. Neon — glowing signs (red-orange). Argon — inert atmosphere for welding; fills incandescent bulbs to stop filament oxidation. Krypton/Xenon — flash lamps, high-intensity headlights. Radon — radioactive; a health hazard when it accumulates in enclosed spaces (basements). |
| Element | Colour/State | Key Use |
|---|---|---|
| Fluorine (F₂) | Pale yellow gas | Toothpaste fluoridation; Teflon; most electronegative element |
| Chlorine (Cl₂) | Greenish-yellow gas | Water disinfection; bleaching powder; PVC manufacture |
| Bromine (Br₂) | Reddish-brown LIQUID | Photography (AgBr); flame retardants; only liquid non-metal at room temp |
| Iodine (I₂) | Violet/purple solid, metallic lustre | Antiseptic (tincture); iodised salt (prevents goiter) |
6.5 Acid-Base-Salt — Theories of Acids and Bases
In one line: Three theories, each BROADER than the last — Arrhenius (aqueous only) → Brønsted-Lowry (proton transfer) → Lewis (electron pairs, covers everything).
| NUMBERS TO REMEMBER Water is amphoteric — acts as a BASE with HCl (accepts H⁺) and as an ACID with NH₃ (donates H⁺). HCl+H₂O→H₃O⁺+Cl⁻; NH₃+H₂O→NH₄⁺+OH⁻. Amphoteric OXIDES react with BOTH acids and bases: Al₂O₃ (aluminium oxide) and ZnO (zinc oxide) are the two classic examples. CuO, by contrast, is purely BASIC — a common mix-up in PYQs. |
| Theory | Acid | Base | Scope |
|---|---|---|---|
| Arrhenius (1884) | Gives H⁺ in water | Gives OH⁻ in water | Aqueous solutions only |
| Brønsted-Lowry (1923) | Proton (H⁺) DONOR | Proton (H⁺) ACCEPTOR | Non-aqueous media too |
| Lewis (1923) | Electron-pair ACCEPTOR | Electron-pair DONOR | Broadest — all coordination chemistry |
| TRAPS — how the exam catches you Dry HCl gas does NOT turn dry litmus paper red — acidic behaviour needs H₃O⁺ ions, which form only when HCl dissolves in WATER. Moist/aqueous HCl does change litmus; the dry gas alone does not. |
6.6 Common Acids & Natural/Chemical Indicators
In one line: 'Ants Sting Forcefully' — Ant=Formic, Vinegar=Acetic, Lemon=Citric, Curd=Lactic. These four source→acid pairs are asked almost every year.
| Acid | Formula | Natural Source |
|---|---|---|
| Hydrochloric acid | HCl | Gastric juice (stomach) |
| Sulphuric acid | H₂SO₄ | 'King of Chemicals'; car batteries |
| Nitric acid | HNO₃ | Explosives (TNT/RDX), fertilizers, aqua regia |
| Acetic acid | CH₃COOH | Vinegar |
| Citric acid | C₆H₈O₇ | Citrus fruits (lemon, orange) |
| Lactic acid | CH₃CHOHCOOH | Sour milk/curd; muscles during exercise |
| Formic acid | HCOOH | Ant/bee sting, nettle leaves |
| Oxalic acid | (COOH)₂ | Tomatoes, spinach |
| Tartaric acid | C₄H₆O₆ | Grapes, tamarind |
| Indicator | Source | In Acid | In Base |
|---|---|---|---|
| Litmus | Lichen | Red | Blue |
| Turmeric | Curcuma longa | Yellow | Red/Brown |
| Phenolphthalein | Synthetic | Colourless | Pink |
| China Rose extract | Hibiscus | Dark Pink | Green |
| Methyl orange | Synthetic | Red/Pink | Yellow/Orange |
| TRAPS — how the exam catches you Onion and clove oil are OLFACTORY indicators — their smell disappears in basic solutions [NCERT Class 10]. |
6.7 Salts, Strong/Weak Acids & the pH Scale
In one line: A salt's acid/basic/neutral nature depends ENTIRELY on the strength of the acid and base that formed it — one rule explains NaCl, CH₃COONa, and NH₄Cl.
| NUMBERS TO REMEMBER NaCl (strong acid HCl + strong base NaOH) → NEUTRAL salt, pH=7. CH₃COONa (weak acid + strong base) → BASIC salt. NH₄Cl (strong acid + weak base) → ACIDIC salt [53rd-55th BPSC 2011]. pH = −log₁₀[H⁺] (Soren Sorensen, 1909); range 0-14; each unit = 10× change in H⁺ concentration. pH<7 acidic, pH=7 neutral, pH>7 basic. pOH = −log[OH⁻]; pH+pOH=14 at 25°C. For 0.1 N HCl: [H⁺]=0.1=10⁻¹, so pH = 1 [real PYQ, 71st BPSC]. |
| Substance | Approx. pH |
|---|---|
| Battery acid | 0–1 |
| Gastric juice | 1.5–3.5 |
| Lemon juice | 2–2.5 |
| Acid rain | <5.6 |
| Pure water | 7 (neutral) |
| Human blood | 7.35–7.45 |
| Milk of magnesia | 10–10.5 |
| Caustic soda (NaOH) | 13–14 |
| TRAPS — how the exam catches you Tooth enamel dissolves below pH 5.5 — that's the tooth-decay threshold, distinct from the acid-rain threshold of pH 5.6 [NCERT Class 10]. Bee sting is ACIDIC (formic acid) → treat with baking soda (alkaline). Wasp sting is ALKALINE → treat with vinegar (acidic). These are opposite — a classic reversal trap. |
— END —
| BPSC CHEMISTRY — FILE 4 Organic Chemistry — Hydrocarbons, Alcohol, Polymer, Organic Acid, Explosives, Fuel |
Bold ORANGE numbers = high-yield facts. RED traps = common exam mistakes. Read subtopic-by-subtopic.
| WHERE THESE QUESTIONS COME FROM BPSC/UPPSC PYQs (39th-71st) via IAS Valley Notes compilation, a tagged Chemistry PYQ bank (Organic Chemistry & Materials Science subtopic), the RO/APO 2026 Science paper, and NCERT Class 10-12 organic chemistry chapters. |
7.1 Hydrocarbons — Saturated & Unsaturated
In one line: Alkanes (single bonds, saturated) vs Alkenes/Alkynes (double/triple bonds, unsaturated) — the bond type alone decides the suffix, the reactivity, and the flame quality.
| NUMBERS TO REMEMBER Homologous series: a family of compounds with the same functional group, differing by a -CH₂- unit each step, showing similar chemical properties and a gradual change in physical properties. Functional groups (examples): -OH (alcohol), -CHO (aldehyde), -COOH (carboxylic acid), -X (haloalkane, X=halogen). Saturated hydrocarbons burn with a CLEAN flame; unsaturated hydrocarbons burn with a more SOOTY/smoky flame (incomplete combustion due to higher carbon content). Unsaturated hydrocarbons ADD hydrogen in the presence of a catalyst (Ni) to become saturated — this is hydrogenation, used industrially to convert vegetable oils into vanaspati ghee. Saturated hydrocarbons (alkanes) are comparatively unreactive/inert; substitution reactions (not addition) are typical for them. |
| Class | Bond Type | Suffix | General Formula | Example |
|---|---|---|---|---|
| Alkanes | Single bonds only (saturated) | -ane | CₙH₂ₙ₊₂ | Methane CH₄, Ethane C₂H₆ |
| Alkenes | ≥1 double bond (unsaturated) | -ene | CₙH₂ₙ | Ethene C₂H₄ |
| Alkynes | ≥1 triple bond (unsaturated) | -yne | CₙH₂ₙ₋₂ | Ethyne (Acetylene) C₂H₂ |
7.2 Aromatic Hydrocarbons — Benzene & its Reactions
In one line: Benzene's ring reacts by ELECTROPHILIC SUBSTITUTION, not addition — sulfonation, nitration, and halogenation all follow the same 'catalyst generates an electrophile' pattern.
| NUMBERS TO REMEMBER Benzene (C₆H₆) treated with fuming sulfuric acid (oleum, excess SO₃) → benzenesulfonic acid (C₆H₅SO₃H) via electrophilic aromatic sulfonation [real PYQ]. The 'big four' electrophilic aromatic substitutions of benzene: Nitration (→ nitrobenzene), Halogenation (→ halobenzenes), Friedel-Crafts alkylation/acylation, and Sulfonation. In benzene + Cl₂ (with FeCl₃ catalyst): FeCl₃ is a Lewis acid catalyst that polarises the Cl-Cl bond, generating the electrophilic Cl⁺ species that attacks the electron-rich ring — FeCl₃ itself is NOT consumed/oxidised/reduced, its role is purely to GENERATE the electrophile [real PYQ]. CO₂ is a linear, symmetric molecule (O=C=O) — its two C=O bond dipoles point in exactly opposite directions and cancel out, giving CO₂ a net ZERO dipole moment (non-polar), unlike bent/pyramidal molecules like H₂O and NH₃ [real PYQ]. Benzene (C₆H₆) bonding count: 12 sigma (σ) bonds (6 C-C + 6 C-H) + 3 pi (π) bonds (from the 3 alternating double bonds/delocalized ring system) — a frequently tested bond-counting fact. |
| TRAPS — how the exam catches you SN1 and SN2 are nucleophilic SUBSTITUTION mechanisms; E2 (elimination) is NOT a substitution reaction — a real 'which is NOT' PYQ tests exactly this distinction. Acidity order: Carboxylic acids > phenols with electron-withdrawing groups (e.g., p-Nitrophenol) > plain Phenol > Alcohols. So Benzoic acid > p-Nitrophenol > Phenol [real PYQ] — carboxylate resonance stabilization beats phenoxide stabilization. |
7.3 Alcohols
In one line: Ethanol is BPSC's favourite alcohol question — know the difference between absolute, denatured, and rectified spirit.
| NUMBERS TO REMEMBER Ethanol (C₂H₅OH) is a liquid at room temperature; produced industrially by fermentation of sugars (yeast) or from ethylene (petrochemical route). Absolute alcohol = 100% pure ethanol (no water) [real PYQ, BPSC BAO 2024]. Denatured alcohol = ethanol deliberately mixed with poisonous substances (e.g., methanol, pyridine) to make it unfit for drinking, while remaining usable industrially — this AVOIDS liquor tax on industrial ethanol. Ethanol uses: pharmaceuticals — antiseptic, antipyretic (fever-reducing), and anti-allergic medicine production; antiseptics (70% ethanol solution kills germs better than 100% — some water is needed to denature microbial proteins), fuel (ethanol-blended petrol, India's E20 programme), solvent for polymers/cosmetics. Fermentation biochemistry (sugarcane/molasses → ethanol): the enzyme Invertase converts sucrose (cane sugar) into glucose + fructose; the enzyme Zymase then converts glucose/fructose into ethanol + CO₂ — two distinct enzyme steps, a favourite NCERT-level detail. Fructose is the sweetest naturally occurring sugar — sweeter than sucrose or glucose; a common comparison point against synthetic sweeteners (saccharin, aspartame). Alcohols are oxidised to carboxylic acids (e.g., ethanol → acetic acid) — this is the ONLY route covered here; oxidation is the defining alcohol→acid conversion (e.g., using acidified KMnO₄/K₂Cr₂O₇, or aerobically by Acetobacter bacteria to make vinegar). |
7.4 Organic (Carboxylic) Acids
In one line: Every 'natural acid + food source' pairing in this file traces back to a carboxylic acid — memorise the memory hook once, apply it to every question.
| NUMBERS TO REMEMBER Memory hook: 'Ants Sting Forcefully' → Ant sting = Formic acid. Vinegar = Acetic acid. Lemon = Citric acid. Curd = Lactic acid — the four most-asked source-acid pairs. Carboxylic acids are MORE acidic than phenols/alcohols because their conjugate base (carboxylate ion) is resonance-stabilised across TWO equivalent oxygen atoms — a stronger stabilisation than phenoxide's single-ring resonance. |
| Acid | Formula | Source |
|---|---|---|
| Acetic (Ethanoic) | CH₃COOH | Vinegar |
| Citric | C₆H₈O₇ | Citrus fruits |
| Lactic | CH₃CHOHCOOH | Curd/sour milk; exercising muscles |
| Formic (Methanoic) | HCOOH | Ant/bee sting — MOST reactive carboxylic acid |
| Oxalic | (COOH)₂ | Tomatoes, spinach — removes rust/ink stains |
| Tartaric | C₄H₆O₆ | Grapes, tamarind — used with baking soda in baking powder |
7.5 Explosive Substances
In one line: Nitric acid (HNO₃) is the common thread — almost every major explosive is made by nitrating an organic compound with concentrated HNO₃/H₂SO₄.
| NUMBERS TO REMEMBER Nitric acid (HNO₃) is the essential reagent for making nitro-explosives (TNT, RDX, nitroglycerin, gun cotton) via nitration reactions — this links Ch10's 'HNO₃ used in explosives' fact directly to this topic. Nitroglycerin is chemically classed as an ESTER (glyceryl trinitrate = ester of glycerol and nitric acid) — not an amine or amide, a common classification trap. Historic atomic bombs (fissile material, not chemical explosives but a related PYQ pairing): Hiroshima bomb 'Little Boy' used Uranium-235; Nagasaki bomb 'Fat Man' used Plutonium-239. Firecracker/fireworks colours come from metal salts: Strontium salts → bright RED, Barium → green, Copper → blue, Sodium → yellow, Magnesium/Aluminium → white/silver sparks. |
| Explosive | Full Name/Composition | Key Fact |
|---|---|---|
| TNT | Trinitrotoluene | Made by nitrating toluene; relatively stable, standard military explosive |
| RDX | Cyclotrimethylenetrinitramine (Research Department Explosive) | More powerful than TNT; used in military & demolition |
| Nitroglycerin | Glyceryl trinitrate | Extremely shock-sensitive liquid explosive; also used medically (angina — vasodilator) |
| Dynamite | Nitroglycerin absorbed in kieselguhr (diatomaceous earth) | Invented by Alfred Nobel — made nitroglycerin safe to handle/transport |
| Gun Cotton | Nitrocellulose (cellulose nitrate) | Made by nitrating cellulose; propellant explosive |
| Gunpowder | Charcoal + Sulphur + Potassium nitrate (KNO₃) | Oldest known explosive/propellant |
| HMX (Octogen) | High Melting Explosive, C₄H₈N₈O₈ | High explosive; rocket fuels, military use |
7.6 Polymers — Natural & Synthetic
In one line: Addition polymerization (double-bond monomers simply join) vs Condensation polymerization (monomers join WITH loss of a small molecule like H₂O) — that one distinction sorts every polymer in the table below.
| Polymer | Monomer | Type |
|---|---|---|
| Polyethylene | Ethylene | Addition; Thermoplastic |
| PVC | Vinyl chloride | Addition; Thermoplastic |
| Teflon (PTFE) | Tetrafluoroethylene | Addition; Thermoplastic — non-stick, chemically inert |
| Nylon-6,6 | Hexamethylenediamine + Adipic acid | Condensation; Thermoplastic |
| Polyester (Dacron) | Ethylene glycol + Terephthalic acid | Condensation; Thermoplastic |
| Bakelite | Phenol + Formaldehyde | Condensation; Thermosetting — world's FIRST synthetic polymer (1907, Baekeland) |
| Melamine-formaldehyde | Melamine + Formaldehyde | Condensation; Thermosetting |
| Buna-S (SBR) | Butadiene + Styrene | Addition; most widely used synthetic rubber |
| Kevlar | Diamine + diacid chloride | Condensation — bulletproof vests |
| PHBV | 3-hydroxybutanoic + 3-hydroxyvaleric acid | Condensation; BIODEGRADABLE bioplastic [71st BPSC 2025 PYQ] |
| Superglue | Cyanoacrylate | Rapid moisture-triggered polymerization [real PYQ] |
| Natural Polymer | Monomer | Source |
|---|---|---|
| Starch | Glucose (α) | Rice, wheat, potato — plant energy storage |
| Cellulose | Glucose (β) | Plant cell walls — cotton, paper, wood |
| Natural Rubber | Isoprene | Latex from Hevea brasiliensis |
| Proteins | Amino acids | Hair, muscle, enzymes |
| TRAPS — how the exam catches you PHBV is a biodegradable polymer/bioplastic (produced naturally by bacteria) — NOT a synthetic non-biodegradable plastic [real PYQ, ScienceMCQ bank]. Superglue is a polymer of Cyanoacrylate, not Vinyl chloride (that's PVC's monomer) — a common distractor pairing [real PYQ]. Acrylic is called 'artificial wool'; Rayon is called 'artificial silk' — these two are frequently swapped in trick questions, so fix the pairing firmly: Acrylic→wool, Rayon→silk. |
7.6b Vulcanization & Thermoplastic vs Thermosetting
In one line: Vulcanization (Goodyear, 1839) is what turns weak, sticky natural rubber into the tyres you actually use — sulfur cross-links the polymer chains.
| NUMBERS TO REMEMBER Vulcanization: heating natural rubber with sulfur at ~150°C creates cross-links between polymer chains → harder, stronger, more elastic, water-resistant. Discovered by Charles Goodyear (1839). Natural rubber = polymer of Isoprene (2-methylbuta-1,3-diene); without vulcanization it's soft, sticky, and has poor mechanical properties. |
| Feature | Thermoplastic | Thermosetting |
|---|---|---|
| On heating | Softens, can be remoulded | Hardens PERMANENTLY |
| Recycling | CAN be recycled | CANNOT be recycled |
| Examples | PVC, polyethylene, nylon, Teflon | Bakelite, melamine-formaldehyde |
7.7 Fuels & Combustion — Calorific Values & Coal Types
In one line: Hydrogen has the HIGHEST calorific value of any fuel — a fact that surprises most students but is asked repeatedly.
| NUMBERS TO REMEMBER Fire triangle: Fuel + Heat + Oxygen — remove any ONE to extinguish a fire. Octane number = anti-knock quality of petrol (iso-octane=100, n-heptane=0). Cetane number = ignition quality of diesel. Types of combustion: Rapid (wood, LPG), Spontaneous (white phosphorus, no external heat needed), Explosive (dynamite, gunpowder), Slow (rusting, respiration — no flame). |
| Fuel | Calorific Value (kJ/kg) | Note |
|---|---|---|
| Hydrogen | ~1,50,000 | HIGHEST of any fuel; zero carbon emission |
| LPG | ~55,000 | Propane+Butane; ethyl mercaptan added for smell |
| CNG | ~55,000 | Mainly CH₄; cleanest vehicular fuel |
| Petrol | ~47,000 | Quality = OCTANE number |
| Diesel | ~45,000 | Quality = CETANE number |
| Coal (Anthracite) | ~32,000 | Best-quality coal |
| Biogas | ~20,000 | CH₄ 50-75% + CO₂; from manure/organic waste |
| Coal Type | Carbon % | Quality |
|---|---|---|
| Peat | ~50% | Lowest — first stage of coal formation; plant traces still recognisable [real PYQ] |
| Lignite | 60–70% | Brown coal |
| Bituminous | 70–85% | Most abundant; power generation, coking coal |
| Anthracite | 90–95% | Best/cleanest-burning |
| TRAPS — how the exam catches you Peat, the EARLIEST stage of coal formation, is the variety that still shows visible plant-material traces — as coalification progresses toward anthracite, those traces are lost [real PYQ]. |
7.8 LPG/CNG/Biogas & Fire Extinguishers
In one line: LPG and CNG have DIFFERENT compositions despite both being 'cooking gas'-adjacent — Propane+Butane vs mostly Methane.
| NUMBERS TO REMEMBER Ethyl mercaptan is added to LPG/CNG (both naturally odourless) to give a detectable rotten-egg smell for leak detection. Water gas = CO+H₂ (steam over hot coke). Producer gas = CO+N₂ (limited air over hot coke). Fuel cell: H₂+O₂→H₂O+electricity — zero emissions. LPG cylinders don't carry a pressure gauge because the pressure inside stays roughly CONSTANT (governed by the liquid-vapour equilibrium) regardless of how much gas remains — pressure alone can't indicate the remaining quantity, unlike a CNG cylinder. |
| Feature | LPG | CNG | Biogas |
|---|---|---|---|
| Composition | Propane+Butane | Mainly CH₄ (80-90%) | CH₄ 50-75% + CO₂ |
| Storage | Liquid under pressure | Compressed gas, 200 bar | Gas, used/stored directly |
| Use | Domestic cooking | Vehicles | Cooking, heating |
| Extinguisher Type | Mechanism | Best For |
|---|---|---|
| Water | Cools below ignition temp | Class A (wood/paper) only |
| CO₂ | Removes O₂, cools | Electrical fires, flammable liquids |
| Dry Powder (ABC) | Smothers + interrupts chain reaction | All fire classes |
| Soda-Acid | NaHCO₃ + dil. H₂SO₄ → CO₂+H₂O | Small/domestic fires [70th BPSC 2024 PYQ] |
— END —
| BPSC CHEMISTRY — FILE 5 Food Preservation, Nutrition, Medicine | Detergents and Soap |
Bold ORANGE numbers = high-yield facts. RED traps = common exam mistakes. Read subtopic-by-subtopic.
| WHERE THESE QUESTIONS COME FROM BPSC/UPPSC PYQs (39th-71st) via IAS Valley Notes compilation, a tagged Chemistry PYQ bank (Everyday & Applied Chemistry subtopic), the RO/APO 2026 Science paper, and NCERT Class 10-12. |
8.1 Drugs & Medicines — Classification
In one line: One drug can wear multiple hats (Aspirin = analgesic + antipyretic + anti-inflammatory + anticoagulant) — BPSC tests whether you know ALL of a drug's roles, not just one.
| NUMBERS TO REMEMBER Aspirin = Acetylsalicylic acid — simultaneously analgesic + antipyretic + anti-inflammatory + anticoagulant (blood thinner). Most commonly asked drug in BPSC. Penicillin = first antibiotic, discovered by Alexander Fleming (1928). Cisplatin, carboplatin, oxaliplatin (platinum-based compounds) are chemotherapy drugs — they bind cancer-cell DNA and interfere with replication [real PYQ]. |
| Category | Function | Examples |
|---|---|---|
| Analgesics | Relieve pain | Aspirin, Paracetamol, Ibuprofen, Morphine |
| Antipyretics | Reduce fever | Aspirin, Paracetamol |
| Antibiotics | Kill/inhibit BACTERIA (not viruses) | Penicillin, Streptomycin, Tetracycline |
| Antiseptics | On LIVING tissue (wounds, skin) | Dettol, Savlon, 70% Ethanol, Iodine tincture |
| Disinfectants | On NON-living surfaces only | Phenol, Chlorine, Bleaching powder |
| Antacids | Neutralise excess stomach HCl | Mg(OH)₂, Al(OH)₃, NaHCO₃ |
| Antihistamines | Block histamine — treat allergies | Cetirizine, Chlorpheniramine |
| Antimalarial | Treat malaria | Quinine (from Cinchona bark), Chloroquine |
| Sedatives/Tranquillisers | Reduce anxiety, induce sleep | Diazepam, Chlordiazepoxide |
| Chemotherapy drugs | Kill rapidly-dividing cancer cells | Cisplatin, Carboplatin (platinum compounds) |
| TRAPS — how the exam catches you Antiseptics go on LIVING tissue; Disinfectants go on NON-living surfaces — never the reverse. Chloramine-T, for instance, is a strong oxidiser too harsh for living tissue, so it's used only as a non-living-surface disinfectant [real PYQ]. Quinine and Chloroquine are BOTH antimalarial — neither is an antibiotic, a frequent distractor pairing. Oxytocin is a HORMONE (from hypothalamus, secreted by pituitary) — NOT an antibiotic [real PYQ, BPSC CDPO 2018]. |
8.2 Named-Drug Trick Facts & Matching
In one line: BPSC loves match-the-drug-to-its-class questions — this is a compressed answer key for the most commonly recycled options.
| Drug | Class |
|---|---|
| Norethisterone | Antifertility/contraceptive hormone (progestin) |
| Levonorgestrel | Antifertility/contraceptive hormone (progestin) — emergency contraceptive pill [real PYQ, 71st BPSC 2025] |
| Venlafaxine | Antidepressant (SNRI) |
| Cetirizine | Antihistamine |
| Chlordiazepoxide | Tranquilliser (first benzodiazepine, brand Librium) |
| Arsphenamine (Salvarsan) | Early antisyphilitic chemotherapeutic agent |
| Tetraethyl lead | Historical anti-knock/octane-boosting fuel additive (now banned — toxic) |
| TRAPS — how the exam catches you Norethisterone (norethindrone) is the antifertility/contraceptive-pill hormone — a real PYQ distractor list includes antidepressants and antihistamines to test if you know the specific class [71st BPSC]. India completely phased out LEADED petrol by 2000; tetraethyl lead has been replaced by ethanol blending (India's E20 programme) and MTBE. |
8.3 Food Chemistry — Artificial Sweeteners
In one line: Sweetness is always measured RELATIVE to sugar — know the multiplier, not just the name.
| Sweetener | Relative Sweetness | Note |
|---|---|---|
| Saccharin | 300–500× sugar | FIRST artificial sweetener; slight bitter aftertaste |
| Aspartame | ~200× sugar | Most widely used; breaks down at high cooking temp |
| Sucralose (Splenda) | ~600× sugar | Stable at high temp; used in baking |
| Stevia | 200–300× sugar | Natural — from Stevia rebaudiana plant |
| Neotame | ~8000× sugar | Aspartame derivative, heat-stable |
| TRAPS — how the exam catches you Aspartame is an artificial SWEETENER — not a synthetic rubber; a real PYQ tests this exact mix-up between chapter topics. |
8.4 Food Preservatives, Antioxidants & Handling Chemicals
In one line: Different preservation methods work by different mechanisms — osmosis (salt/sugar), acidity (vinegar), or oxidation-blocking (antioxidants, N₂ gas) — know WHICH mechanism, not just the chemical name.
| NUMBERS TO REMEMBER Salt/Sugar: high concentration → plasmolysis (bacteria lose water by osmosis). Vinegar (acetic acid): acidic environment inhibits bacteria — pickles, ketchup. Sodium benzoate (C₆H₅COONa): the most common chemical preservative — cold drinks, jams, pickles. Potassium metabisulphite: wine, dried fruits, fruit juices. Antioxidants (BHA, BHT, Vitamin C/E): prevent RANCIDITY (oxidation of fats/oils). Nitrogen gas filled in chips packets: prevents oxidation of oils — a physical (inert-atmosphere), not chemical, preservation method. Iodised salt is fortified with Potassium Iodide (KI), NOT free/elemental iodine — a common misconception; KI is stable and safely provides dietary iodine to prevent goiter. |
• Calcium carbide is used to artificially HASTEN fruit ripening (releases acetylene gas, mimics ethylene) — though banned in India for food use due to arsenic/phosphorus impurity risks.
• Potassium permanganate (KMnO₄) is used to PRESERVE fruit (as a wash, controls fungal growth).
• Silver iodide (AgI) is used for cloud seeding to induce ARTIFICIAL RAIN — not a food chemical, but a commonly paired distractor in the same PYQ set [real RO Prelims 2026 match-the-following].
9.1 Soap — Composition & Saponification
In one line: Soap cleans via MICELLE formation — hydrophobic tail traps grease, hydrophilic head faces water — this single mechanism explains everything soap can and can't do.
| NUMBERS TO REMEMBER Soap = sodium/potassium salt of a long-chain fatty acid; formula RCOONa or RCOOK. Preparation — Saponification: fat/oil + NaOH(aq) → soap + glycerol. Soap molecule structure: hydrophilic head (−COO⁻Na⁺, water-loving) + hydrophobic tail (long hydrocarbon chain, grease-loving). Micelle formation: soap molecules surround grease/dirt with hydrophobic tails pointing IN (toward grease) and hydrophilic heads pointing OUT (toward water) — this emulsifies grease so it washes away [real PYQ: soap removes grease by emulsification]. |
| TRAPS — how the exam catches you Soap does NOT work well in hard water — Ca²⁺/Mg²⁺ ions react with soap to form an insoluble scum: 2RCOONa + CaCl₂ → (RCOO)₂Ca↓ + 2NaCl. |
9.2 Detergents — Composition & Advantage over Soap
In one line: Detergents exist because soap has exactly one weakness (hard water) — everything about detergent chemistry follows from fixing that one weakness.
| NUMBERS TO REMEMBER Detergents = sodium alkyl sulphonates or sodium alkyl benzene sulphonates (R-SO₃Na) [real PYQ, 63rd BPSC 2017]. Advantage over soap: WORK IN HARD WATER — the Ca²⁺/Mg²⁺ salts of sulphonates remain SOLUBLE (unlike soap's insoluble scum). Disadvantage: older/non-biodegradable detergents cause water pollution (persistent froth in rivers); modern detergents use straight-chain sulphonates that ARE biodegradable. |
— END —
| BPSC CHEMISTRY — FILE 6 Fertilizers | Miscellaneous (Environmental Chemistry & Applied Facts) |
Bold ORANGE numbers = high-yield facts. RED traps = common exam mistakes. Read subtopic-by-subtopic.
| WHERE THESE QUESTIONS COME FROM BPSC/UPPSC PYQs (39th-71st) via IAS Valley Notes compilation, a tagged Chemistry PYQ bank, the RO/APO 2026 Science paper, and NCERT Class 6-12. |
10.1 Fertilizers — NPK Table, Haber Process & Biofertilizers
In one line: Urea's 46% nitrogen content is the single most-asked fertilizer fact — everything else in this topic builds around the N-P-K framework.
| NUMBERS TO REMEMBER N-P-K roles: Nitrogen (N) for leaf/vegetative growth, Phosphorus (P) for roots/fruits, Potassium (K) for overall plant health/disease resistance. Urea elements: C, H, N, O (carbamide) — a direct 'which elements are present' PYQ [66th BPSC 2020]. Nitrogen fertilizers manufactured via the Haber Process: N₂ + 3H₂ ⇌ 2NH₃ (Fe catalyst, 450°C, 200 atm) [NCERT Class 11]. Biofertilizers: Rhizobium (legume root nodules — nitrogen fixation), Azospirillum, Mycorrhiza, Blue-green algae. |
| Fertilizer | Formula | Nutrient |
|---|---|---|
| Urea | CO(NH₂)₂ | 46% N — highest of any N fertilizer; most widely used |
| DAP | (NH₄)₂HPO₄ | N=18%, P₂O₅=46% |
| Ammonium sulphate | (NH₄)₂SO₄ | N=21%; oldest N fertilizer; also adds sulphur |
| Ammonium nitrate | NH₄NO₃ | N=34%; fast-acting; explosive when concentrated |
| Potash (MOP) | KCl | Provides K — root development, disease resistance |
| TRAPS — how the exam catches you Overuse of chemical fertilizers → eutrophication and nitrate contamination of groundwater — this links fertilizer overuse directly to the water-pollution topic below. |
11.1 Miscellaneous — Air Pollutants
In one line: Each pollutant has ONE signature mechanism — CO binds haemoglobin, SO₂ causes acid rain, CFCs destroy ozone. Learn the mechanism, not just the source.
| NUMBERS TO REMEMBER CO is colourless, odourless, and binds haemoglobin 200× faster than O₂, forming carboxyhaemoglobin — a repeatedly tested exact multiplier [real PYQ]. |
| Pollutant | Main Source | Key Effect |
|---|---|---|
| CO | Incomplete combustion | Binds Hb 200× faster than O₂ → carboxyhaemoglobin → suffocation |
| SO₂ | Burning coal/oil, ore smelting | MAIN cause of acid rain; respiratory disease |
| NOₓ | Vehicle exhaust, power plants | Acid rain (HNO₃); photochemical smog |
| Ozone (tropospheric) | Photochemical smog | Eye/lung irritant — 'bad' ozone, unlike protective stratospheric ozone |
| Lead compounds | Leaded petrol (banned), battery recycling | Neurotoxin — affects children's brain development |
| CFCs (Freons) | Fridges, ACs, aerosol sprays | Destroy stratospheric ozone layer |
11.2 Miscellaneous — Greenhouse Effect & Ozone Layer
In one line: One Chlorine atom destroys ~100,000 ozone molecules — the chain-reaction scale is exactly why CFCs are so damaging despite being used in tiny quantities.
| NUMBERS TO REMEMBER Greenhouse gases: CO₂ (main), CH₄, N₂O, O₃, H₂O vapour, CFCs. Global Warming Potential: CH₄ = 25× CO₂; N₂O = 298× CO₂; CFCs = thousands× CO₂. CO₂ has risen from ~280 ppm (pre-industrial) to ~420 ppm today — mainly from fossil fuel combustion; deforestation reduces CO₂ absorption capacity. Stratospheric ozone (15-35 km) is BENEFICIAL — absorbs UV-B/UV-C. Formation: O₂+UV→2O; O+O₂→O₃. CFC depletion chain: CF₂Cl₂ --UV--> Cl + CF₂Cl; Cl+O₃→ClO+O₂; ClO+O→Cl+O₂ — the chain regenerates Cl, so one Cl atom can destroy ~100,000 O₃ molecules. Montreal Protocol (1987): international treaty phasing out CFCs/HCFCs — widely regarded as the most successful environmental treaty. Ozone hole is largest over Antarctica (polar vortex effect). International climate agreements: Kyoto Protocol (1997), Paris Agreement (2015). |
11.3 Miscellaneous — Acid Rain & Water Pollution
In one line: Minamata=Mercury, Itai-Itai=Cadmium — this Japan-disease pairing is asked almost every cycle; keep the two straight by remembering 'Itai-Itai' (ouch-ouch, from bone pain) = bone-damaging Cadmium.
| NUMBERS TO REMEMBER Acid rain: pH < 5.6 (normal rain is pH ~5.6 due to dissolved CO₂). Caused by SO₂→H₂SO₄ and NOₓ→HNO₃ in rainwater. Taj Mahal marble damage: CaCO₃ + H₂SO₄ → CaSO₄ + H₂O + CO₂ — the CaSO₄ (gypsum) forms a white powdery crust, a favourite illustrative BPSC example. North Bihar: groundwater ARSENIC contamination (Ganga plains — Bhagalpur, Patna districts, natural geological deposits) plus fluorosis in several districts — both are major Bihar-specific BPSC topics. |
| Concept | Explanation |
|---|---|
| BOD | O₂ consumed by microbes decomposing organic matter; high BOD = polluted water |
| COD | Total O₂ to chemically oxidise ALL pollutants; COD ≥ BOD always |
| Eutrophication | Fertiliser runoff → algal bloom → blocks sunlight → O₂ depletion → fish death |
| Minamata Disease | Mercury (Hg) poisoning via fish — Minamata Bay, Japan, 1956 |
| Itai-Itai Disease | Cadmium (Cd) poisoning — Japan; severe bone/kidney damage |
| Fluorosis | Excess fluoride in drinking water — teeth/bone damage; endemic in Bihar, Rajasthan, Andhra Pradesh |
11.4 Miscellaneous — Smog Types
In one line: Classical smog needs COLD + moisture; photochemical smog needs HOT + sunlight — opposite weather conditions produce two entirely different pollution chemistries.
| Type | Classical (London) Smog | Photochemical (LA) Smog |
|---|---|---|
| Formation | Coal burning + fog; SO₂+smoke+moisture | NOₓ+VOCs+sunlight → O₃, PAN |
| Weather | Cold, humid | Hot, sunny, low humidity |
| Main components | SO₂, soot (reducing smog) | O₃, PAN, NO₂ (oxidising smog) |
| Effect | Respiratory problems | Eye irritation; PAN is most toxic component |
11.5 Miscellaneous — Applied Chemistry Grab-Bag
In one line: A cluster of standalone applied-chemistry facts BPSC has actually asked — each is a complete, self-contained fact worth memorising individually.
• A catalyst works by lowering the potential energy of the TRANSITION STATE (activation energy) — it does NOT change the energy of reactants or products [real RO Prelims 2026 PYQ].
• 'Night-glowing' phosphorescent pigment = Europium-doped strontium aluminate (SrAl₂O₄:Eu) — modern glow-in-the-dark material, replacing the older, shorter-glowing zinc sulphide doped with copper (ZnS:Cu).
• 'Smart film'/smart-glass (electrochromic) applications use Indium Tin Oxide (ITO) — a transparent conducting oxide, also standard in touchscreens and thin-film solar cells.
• Photostat (photocopier) machine drums are coated with Selenium [real PYQ, BPSC APO paper].
• Ammoniacal nitrogen in wastewater = the SUM of free ammonia (NH₃) AND ammonium ion (NH₄⁺) together, not just one of the two [real PYQ].
• Fischer-Tropsch process: CO + H₂ --(iron catalyst)--> hydrocarbons + oxygenated hydrocarbons — used to synthesise fuels from syngas [real PYQ].
• Agar-agar, alginic acid, and the jelly from Gracilaria algae are chemically Phyco-colloids [real PYQ].
• Lipids are insoluble in water because they are hydrophobic [real PYQ].
• Green Chemistry = designing chemical products/processes that reduce or eliminate the use and generation of hazardous substances — focuses on prevention at the source, not clean-up afterward.
• Cadmium is NOT radioactive (unlike Uranium, Radium, Thorium, which ARE) — a common trap since Cadmium 'sounds' radioactive. It's a toxic heavy metal, used in Ni-Cd rechargeable batteries, and causes Itai-Itai disease.
• Breathalyzer chemistry: the test cartridge contains potassium dichromate (K₂Cr₂O₇) + dilute sulphuric acid, which is orange-red; it turns GREEN when it oxidises ethanol in the breath — the colour change (orange→green) indicates alcohol presence.
• The 'X' in X-ray stands for 'unknown' — Wilhelm Röntgen named it X-ray in 1895 because the nature of the radiation was unknown at the time of discovery.
— END —