Kerala Plus Two Chemistry flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Raoult's law

For an ideal solution, the partial vapour pressure of each volatile component equals its pure vapour pressure multiplied by its mole fraction in the liquid mixture.

van't Hoff factor

Ratio of observed colligative effect to that calculated for a non-dissociating solute; for dissociation i=1+(n−1)α, and for association i=1−α+α/n.

Osmotic pressure

Pressure required to prevent net solvent flow through a semipermeable membrane; for dilute solutions π=CRT, where C is molar concentration, R gas constant, T kelvin temperature.

Nernst equation

At 298 K, E=E°−(0.0591/n)log Q for a cell reaction; Q is reaction quotient and n is moles of electrons transferred.

Molar conductivity

Conductivity divided by molar concentration: Λm=κ/c, usually in S m² mol⁻¹; it measures conducting ability per mole of dissolved electrolyte.

Kohlrausch law

Limiting molar conductivity of an electrolyte equals the sum of limiting ionic conductivities, each multiplied by its stoichiometric coefficient; used to calculate weak-electrolyte values.

First-order half-life

For a first-order reaction, t1/2=0.693/k; it is independent of initial reactant concentration, so each successive half-life is equal.

Arrhenius equation

k=Ae^(−Ea/RT), relating rate constant k to activation energy Ea, temperature T, gas constant R, and pre-exponential factor A.

Order of reaction

Sum of the exponents of concentration terms in the experimentally determined rate law; it may be zero, fractional, or negative and is not molecularity.

Lanthanoid contraction

Gradual decrease in atomic and ionic radii from lanthanum to lutetium, caused by poor shielding of nuclear charge by 4f electrons; it increases density and similarity in size.

Interstitial compounds

Compounds formed when small atoms such as carbon or nitrogen occupy holes in a metal lattice; they are often nonstoichiometric, hard, high melting, and retain metallic conductivity.

Transition element

An element whose atom or common ion has an incomplete d subshell; typical properties include variable oxidation states, coloured ions, paramagnetism, catalysis, and complex formation.

Coordination number

Number of donor atoms directly bonded to the central metal ion in a complex; common values are 2, 4, and 6, giving linear, tetrahedral/square planar, and octahedral geometries.

Chelate effect

Greater stability of complexes with polydentate ligands compared with similar monodentate ligands, because ring formation reduces the entropy loss on binding and resists ligand displacement.

Spectrochemical series

Order of ligands by crystal-field splitting: I⁻<Br⁻<Cl⁻<F⁻<H2O<NH3<CN⁻<CO; stronger-field ligands produce larger Δo and favour low-spin complexes.

SN1 mechanism

Two-step nucleophilic substitution with rate-determining carbocation formation; rate depends on substrate, tertiary haloalkanes react fastest, and chiral substrates give racemisation.

SN2 mechanism

One-step nucleophilic substitution with backside attack and inversion of configuration; rate depends on both substrate and nucleophile, and primary haloalkanes react fastest.

Finkelstein reaction

Conversion of an alkyl chloride or bromide to the corresponding iodide by heating with sodium iodide in dry acetone; sodium chloride or bromide precipitates, shifting equilibrium.

Lucas test

Adding anhydrous ZnCl2 in concentrated HCl to an alcohol: tertiary alcohol turns cloudy immediately, secondary on warming, primary only with heating or not readily.

Williamson synthesis

Preparation of an ether by treating a sodium alkoxide with a primary alkyl halide via SN2; tertiary halides favour elimination and give alkenes instead.

Phenol acidity

Phenol is more acidic than alcohols because its phenoxide ion is resonance-stabilised; electron-withdrawing substituents increase acidity, while electron-donating groups decrease it.

Tollens' test

Warm ammoniacal silver nitrate with an aldehyde; aldehyde reduces Ag⁺ to metallic silver, forming a mirror, while most ketones do not react.

Aldol condensation

Base-catalysed reaction of an aldehyde or ketone having α-hydrogen to form a β-hydroxy carbonyl, which may dehydrate to an α,β-unsaturated carbonyl.

Cannizzaro reaction

Concentrated base converts an aldehyde without α-hydrogen into equal amounts of the corresponding carboxylate salt and alcohol through disproportionation.

Hinsberg test

Benzenesulfonyl chloride distinguishes amines: primary gives an alkali-soluble sulfonamide, secondary an insoluble sulfonamide, and tertiary gives no sulfonamide.

Diazotisation

Reaction of a primary aromatic amine with sodium nitrite and hydrochloric acid at 0–5 °C to form a diazonium salt, which is unstable and used for coupling and substitution.

Hofmann bromamide reaction

Heating an amide with bromine and alkali gives a primary amine with one fewer carbon atom, through migration of the alkyl group to nitrogen.

Reducing sugar

A sugar with a free anomeric hydroxyl group that can reduce Tollens' or Fehling's reagent; glucose, fructose, maltose, and lactose are reducing, but sucrose is not.

Denaturation

Loss of a protein's native three-dimensional structure by heat, pH change, or chemicals, often without breaking peptide bonds; biological activity and solubility may be lost.

DNA base pairing

In DNA, adenine pairs with thymine by two hydrogen bonds, and guanine pairs with cytosine by three; the strands are antiparallel and form a double helix.

Rf value

In chromatography, the ratio of the distance travelled by the solute spot to the distance travelled by the solvent front from the same origin; it is characteristic under fixed conditions.

Brown ring test

Test for nitrate: add iron(II) sulphate and then concentrated sulphuric acid carefully; a brown ring of nitrosyl iron(II) complex forms at the interface.