Assam ASSEB HS Chemistry cheat sheet

Unit-cell atoms: simple cubic z=1, bcc z=2, fcc z=4; packing efficiency SC 52.4%, BCC 68%, FCC 74%.

Radius–edge relations: SC r=a/2; BCC r=√3a/4; FCC r=a/(2√2).

Density d = zM/(a^3 N_A), with a in cm and M in g mol^-1.

Raoult's law: p_total = p°_A x_A + p°_B x_B; relative lowering Δp/p°_A = x_B for a non-volatile solute.

Colligative relations: ΔTb=iKb m, ΔTf=iKf m, π=iCRT; i=1 for non-electrolytes, i>1 for dissociating solutes.

Henry's law p=K_H x: gas solubility decreases as temperature rises and as K_H rises.

Ideal solutions: ΔH_mix=0, ΔV_mix=0, obey Raoult over all compositions; positive deviation means A–B forces weaker than A–A/B–B.

Schottky defect: cation–anion vacancy pair, density decreases; Frenkel defect: ion displaced to interstitial site, density unchanged.

Osmotic pressure is preferred for macromolecules because it is measurable at low concentration and is not sensitive to particle size.

G=1/R; conductivity κ=G l/A; molar conductivity Λm=κ×1000/M (κ in S cm^-1, M in mol L^-1).

Strong electrolytes: Λm=Λ°m−A√c; weak electrolytes: degree of dissociation α=Λm/Λ°m.

Kohlrausch law: Λ°m=ν+λ°+ + ν−λ°−; used for weak electrolytes and sparingly soluble salts.

Nernst equation at 298 K: E=E°−(0.0591/n) log Q; E°cell=E°cathode−E°anode.

ΔG°=−nFE°; E°>0 gives ΔG°<0 and a spontaneous cell reaction.

Faraday: Q=It; moles reacted=Q/(nF); F=96500 C mol^-1.

Salt bridge maintains electrical neutrality and reduces liquid-junction potential; it does not supply electrons.

Rusting requires both O2 and H2O; in acidic corrosion H+ is reduced, in neutral/aerobic corrosion O2 is reduced; galvanising and cathodic protection prevent corrosion.

On dilution, κ decreases but Λm increases for both strong and weak electrolytes.

Rate=k[A]^m[B]^n; order=m+n; order is experimental and may be zero, fractional, or negative.

Zero order: [A]=[A]0−kt, t1/2=[A]0/(2k), k units mol L^-1 s^-1.

First order: ln[A]=ln[A]0−kt, t1/2=0.693/k, k unit s^-1; half-life independent of [A]0.

Second order: 1/[A]=1/[A]0+kt, t1/2=1/(k[A]0).

Arrhenius: k=Ae^(−Ea/RT); ln(k2/k1)=(Ea/R)(1/T1−1/T2); slope of ln k vs 1/T is −Ea/R.

Collision theory: rate=PZ e^(−Ea/RT); P is steric/orientation factor; only collisions with E≥Ea are effective.

Catalyst lowers Ea and speeds both forward and reverse reactions; it does not change ΔH, ΔG°, or equilibrium constant.

Rate-determining step is the slowest elementary step; overall rate law follows its reactants and prior equilibria.

Units of k: zero mol L^-1 s^-1; first s^-1; second L mol^-1 s^-1; general (mol L^-1)^(1−n) s^-1.

Physisorption: van der Waals forces, ΔH_ads about 20–40 kJ mol^-1, reversible, multilayer, not specific.

Chemisorption: chemical bonds, ΔH_ads about 80–240 kJ mol^-1, irreversible, monolayer, specific.

Freundlich isotherm: x/m=k p^(1/n), 0<1/n<1; log plot is linear.

Langmuir isotherm: monolayer, uniform sites, no interaction; x/m=ap/(1+bp).

Homogeneous catalyst is in same phase as reactants; heterogeneous catalyst is in a different phase, often solid.

Promoters increase catalyst activity; poisons reduce it; catalytic converters oxidise CO and hydrocarbons and reduce NOx.

Colloid particle size 1–1000 nm; Tyndall scattering, Brownian motion, and electrophoresis are characteristic.

Hardy–Schulze rule: coagulating power increases with ion charge; Al3+>Ca2+>Na+ for a negative sol.

Dialysis removes dissolved electrolytes from a colloid; peptisation converts a precipitate back to a colloid.

Froth flotation concentrates sulphide ores; gangue is wetted by water, ore particles are carried by froth.

Roasting: sulphide ore + excess air → oxide + SO2; calcination: carbonate/hydroxide + limited air → oxide + CO2/H2O.

Reduction methods: carbon (ZnO, Fe2O3), CO (Fe2O3), Al thermite (Cr2O3, Mn3O4), electrolysis (Na, Al), self-reduction (Cu2S).

Refining: distillation (Zn, Hg), liquation (Pb, Sn), electrolytic (Cu, Al), zone refining (Si, Ge), van Arkel (Ti, Zr).

Group 15: N2 inert due to N≡N; NH3 basic; HNO3 oxidising; P has white/red/black allotropes; PCl5 trigonal bipyramidal.

Group 16: O2, O3; SO2 bleaches by reduction; H2SO4 made by contact process; Se and Te are metalloids.

Group 17: oxidising power F2>Cl2>Br2>I2; Cl2 with water gives HOCl, causing bleaching; interhalogens like ClF3.

Group 18: noble gases; XeF2 linear, XeF4 square planar, XeF6 distorted octahedral; xenon fluorides hydrolyse.

Inert-pair effect: down groups 13–15, lower oxidation state becomes more stable, e.g., Tl+>Tl3+, Pb2+>Pb4+, Bi3+>Bi5+.

3d series: variable oxidation states, coloured ions, paramagnetism, complex formation, catalytic activity.

Anomalous configurations: Cr [Ar]3d^5 4s^1, Cu [Ar]3d^10 4s^1, because half-filled/full d subshells are extra stable.

Atomic radii decrease across 3d then rise slightly at Cu/Zn; Zn has no unpaired d electrons and is diamagnetic.

Magnetic moment μ=√(n(n+2)) BM, where n is number of unpaired electrons.

Lanthanoid contraction: poor 4f shielding → decreasing radii; causes Y to resemble heavy lanthanoids and Zr/Hf similarity.

KMnO4: acidic → Mn2+ (n=5), neutral → MnO2 (n=3), alkaline → MnO4^2- (n=1); purple colour fades.

K2Cr2O7 in acid → Cr3+ (green); Cr2O7^2- orange, CrO4^2- yellow; dichromate is a primary standard.

Ce4+ is a strong oxidant (→Ce3+); Eu2+ is a reducing agent (→Eu3+); lanthanoids mostly form +3 ions.

Catalysts: Fe (Haber), V2O5 (contact), Ni (hydrogenation), Pt/Rh (catalytic converter).

Coordination number = number of donor atoms bonded to metal; common 4 (tetrahedral/square planar) and 6 (octahedral).

Ligand denticity: monodentate (NH3, Cl^-), bidentate (en, C2O4^2-), hexadentate (EDTA); chelate complexes are extra stable.

Nomenclature: name ligands alphabetically; anionic ligands end -o; complex cation named before anion; oxidation state in Roman numerals.

Isomerism: geometric (cis/trans), optical, ionization, hydrate, linkage, and coordination isomerism.

VBT: sp3 tetrahedral, dsp2 square planar, d2sp3 inner-orbital octahedral, sp3d2 outer-orbital octahedral.

CFT: Δo = splitting of d orbitals in octahedral field; strong-field ligands (CN^-, CO) give low-spin and large Δo.

Spectrochemical series: I^-<Br^-<Cl^-<F^-<H2O<NH3<en<CN^-<CO.

Colour arises from d–d transitions; d0 and d10 complexes are usually colourless.

Applications: EDTA in titrations, cisplatin anticancer, chlorophyll Mg complex, vitamin B12 Co complex.

SN2: one step, backside attack, inversion (Walden), second-order, favoured by primary halides and polar aprotic solvents.

SN1: carbocation intermediate, first-order, racemisation, favoured by tertiary halides and polar protic solvents.

Elimination with alcoholic KOH follows Saytzeff rule: more substituted alkene is major; bulky base gives Hofmann product.

Aryl halides resist SN1/SN2 due to sp2 C–X partial double-bond character; nucleophilic substitution needs drastic conditions.

Finkelstein: R–X + NaI/acetone → R–I; Swarts: R–X + AgF → R–F.

Sandmeyer: ArN2+ + CuCl/HCl → ArCl; Gattermann uses Cu/HCl; coupling with phenol gives azo dyes.

Grignard: RMgX + HCHO → 1° alcohol; + RCHO → 2° alcohol; + R2CO → 3° alcohol; + CO2 → carboxylic acid.

Boiling point RI>RBr>RCl>RF; branching lowers boiling point; haloalkanes are denser than water.

Haloalkane + AgNO2 → nitroalkane; + KNO2 → alkyl nitrite; this is a distinction test.

Alcohols: Lucas test ZnCl2/HCl - 3° immediate turbidity, 2° ~5 min, 1° no reaction at room temperature.

Oxidation: 1° alcohol → aldehyde → carboxylic acid; 2° → ketone; 3° resists oxidation under mild conditions.

Phenol is acidic because phenoxide is resonance-stabilised; it dissolves in NaOH but not in NaHCO3, distinguishing it from carboxylic acids.

Phenol reactions: Reimer–Tiemann (CHCl3/NaOH) → salicylaldehyde; Kolbe (CO2/NaOH) → salicylic acid; excess Br2 → 2,4,6-tribromophenol.

Williamson synthesis: RONa + R'X → R–O–R' via SN2; primary halides work best, tertiary give elimination.

Ether cleavage with HI: cold dilute gives alcohol + alkyl iodide; excess hot HI gives two alkyl iodides.

Zeisel method: ether + HI → alkyl iodide, estimated by AgNO3; methoxy groups detected this way.

Dehydration of alcohols with conc. H2SO4 follows Saytzeff; order of ease 3°>2°>1°.

Ethers form explosive peroxides on prolonged air exposure; stored in dark with antioxidants.

Nucleophilic addition reactivity: HCHO > RCHO > R2CO; electron-withdrawing groups increase reactivity, steric bulk decreases it.

Tollens' test: ammoniacal AgNO3 gives silver mirror with aldehydes; Fehling's test is positive for aliphatic aldehydes, not aromatic.

Aldol condensation: carbonyl with α-H + dilute base → β-hydroxy carbonyl; heat → α,β-unsaturated carbonyl.

Cannizzaro: aldehyde without α-H (HCHO, PhCHO) + conc. NaOH → alcohol + carboxylate (disproportionation).

Haloform test: CH3CO– or CH3CH(OH)– + I2/NaOH → CHI3 yellow precipitate; positive for acetaldehyde and methyl ketones.

Carboxylic acid acidity: HCOOH > CH3COOH; electron-withdrawing groups increase acidity (ClCH2COOH > CH3COOH); electron-donating groups decrease.

HVZ reaction: carboxylic acid + Br2/P → α-bromo acid; decarboxylation: RCOONa + NaOH/CaO → RH + Na2CO3.

Clemmensen reduction (Zn-Hg/HCl) and Wolff–Kishner (NH2NH2/KOH) reduce C=O to CH2.

Carboxylic acids form salts with NaHCO3, releasing CO2; this distinguishes them from phenols.

Amine basicity in water: (CH3)2NH > CH3NH2 > (CH3)3N > NH3; aromatic amines are weaker because lone pair is delocalised.

Hinsberg test: 1° amine + PhSO2Cl → soluble sulphonamide; 2° → insoluble; 3° → no reaction.

Diazonium salt reactions: Sandmeyer (CuCl/HCl → ArCl), coupling with phenol → azo dye, hydrolysis → phenol.

Carbohydrates: glucose is aldohexose, fructose ketohexose; sucrose is non-reducing; starch and cellulose are polysaccharides.

Proteins are polypeptides; amino acids have –NH2 and –COOH; denaturation destroys secondary/tertiary structure without breaking peptide bonds.

Addition polymers: polythene, PVC, Teflon; condensation polymers: nylon-6,6, terylene, Bakelite.

Soap is sodium salt of fatty acid; micelle forms in water; detergents are synthetic and can be biodegradable or non-biodegradable.

Drug classes: analgesics (aspirin), antibiotics (penicillin), antiseptics (dettol).

Enzymes are biological catalysts, highly specific; vitamins are micronutrients; nucleic acids DNA/RNA store genetic information.

Molarity M = moles solute / litres solution; normality = molarity × n-factor; dilution M1V1=M2V2.

Primary standards: oxalic acid, K2Cr2O7, Na2CO3, NaCl; must be pure, stable, non-hygroscopic.

KMnO4 titration is self-indicating; endpoint is faint permanent pink; acidified with dilute H2SO4, not HCl.

K2Cr2O7 titration uses diphenylamine indicator; endpoint is blue-violet; n=6 for Cr2O7^2- → 2Cr3+.

Iodometric titration uses starch indicator; endpoint is blue to colourless; Na2S2O3 is standardised against K2Cr2O7.

Salt analysis: cations by group reagents (Group I HCl, II H2S, III NH4OH, IV (NH4)2CO3); flame tests identify Na, K, Ca, Sr, Ba, Cu.

Anion tests: carbonate gives CO2 with acid; sulphate gives white BaSO4; chloride gives white AgCl soluble in NH3; nitrate gives brown NO2.

Organic preparation: acetanilide by acetylation of aniline; p-nitroacetanilide by nitration; iodoform by acetone + I2/NaOH.

Percentage yield = actual yield/theoretical yield ×100%; percentage purity from titration.