CHSE Odisha Elective Chemistry key terms

The smallest portion of a crystal lattice that, when repeated in three dimensions, reproduces the complete crystal. It is described by its edge lengths and the angles between them.

The fraction, usually expressed as a percentage, of the total volume of a unit cell that is actually occupied by the constituent particles. It depends on the type of lattice.

A point defect in ionic crystals in which equal numbers of cations and anions are missing from their lattice positions, leaving empty sites. It lowers the density of the crystal.

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

The ratio of the observed value of a colligative property to the value calculated assuming no dissociation or association, showing how many particles one formula unit effectively produces.

The potential, measured against the standard hydrogen electrode at 298 K, of an electrode in which all species are at unit activity, usually 1 M concentration and 1 bar pressure.

The conductance of a solution containing one mole of dissolved electrolyte placed between electrodes one centimetre apart. It increases on dilution because dissociation increases and ion-ion hindrance falls.

At infinite dilution, the molar conductivity of an electrolyte equals the sum of the limiting molar conductivities of its individual ions, each multiplied by its stoichiometric coefficient.

The arrangement of elements or ions in order of increasing standard reduction potential, used to predict whether a redox reaction such as metal displacement will occur spontaneously.

The sum of the powers to which reactant concentrations are raised in the experimentally determined rate law. It may be zero, fractional or negative and is not given by the balanced equation.

The time required for the concentration of a reactant to fall to half of its initial value. For a first-order reaction it is independent of the starting concentration.

The minimum extra energy that colliding reactant molecules must possess, above their average energy, for the collision to lead to product formation.

An expression relating the rate constant to temperature: k = A e^(−Ea/RT), where A is the frequency factor, Ea the activation energy and R the gas constant.

The accumulation of molecules of a gas or solute on the surface of a solid or liquid, rather than throughout its bulk, because of unbalanced attractive forces at the surface.

Adsorption in which the adsorbed molecules are held to the surface by chemical bonds, giving a monomolecular layer, a high heat of adsorption and strong, often irreversible, attachment.

The scattering of a beam of light by colloidal particles, which makes the path of the beam visible; it distinguishes a colloid from a true solution.

Heating an ore strongly in a limited supply of air or in the absence of air, to remove water and volatile impurities and to decompose carbonates into oxides.

Heating a sulphide ore in a plentiful supply of air so that it is converted into its oxide, with sulphur dioxide released; commonly used before reduction of the metal.

Treatment of a finely divided ore with a suitable solvent that dissolves the desired metal compound selectively, leaving the gangue behind; the metal is then recovered from solution.

A graph plotting the standard Gibbs energy of formation of metal oxides per mole of oxygen against temperature; it predicts the temperature at which one metal can reduce another's oxide.

The tendency of the outermost s-electrons in heavier p-block elements, such as lead and bismuth, to remain unused in bonding, making their lower oxidation states more stable than expected.

The gradual decrease in atomic and ionic radii from lanthanum to lutetium, caused by poor shielding of the nuclear charge by the inner 4f electrons.

The separation in energy of a metal's d orbitals when ligands approach and create an electrostatic field of particular geometry around the central ion.

A ligand that attaches to the same central metal ion through two or more donor atoms at once, forming a ring structure and usually giving a more stable complex.

A form of isomerism in coordination compounds in which the same ligands exchange places between the coordination sphere and the ion outside it, giving different ions in solution.

A nucleophilic substitution in which the leaving group departs first to form a carbocation intermediate, which is then attacked by the nucleophile; the rate depends only on the substrate.

A one-step nucleophilic substitution in which the nucleophile attacks the carbon from the side opposite the leaving group as it departs, giving inversion of configuration.

A test that distinguishes primary, secondary and tertiary alcohols by the time taken for a cloudy layer of alkyl chloride to appear when the alcohol is shaken with concentrated hydrochloric acid and zinc chloride.

The introduction of a formyl group onto the ring of phenol by treating it with chloroform and aqueous sodium hydroxide, giving mainly salicylaldehyde.

A base-catalysed reaction in which an aldehyde or ketone having α-hydrogen forms a β-hydroxy carbonyl compound, which may lose water to give an α,β-unsaturated carbonyl.

A reaction of aldehydes without α-hydrogen, such as benzaldehyde, with concentrated alkali, in which one molecule is oxidised to a carboxylate salt and another reduced to an alcohol.

The conversion of a primary amide into a primary amine containing one carbon fewer, by heating it with bromine and aqueous or alcoholic potassium hydroxide.

The reaction of a primary aromatic amine with nitrous acid, generated from sodium nitrite and hydrochloric acid at 273–278 K, to form a diazonium salt.

The amide linkage formed between the carboxyl group of one amino acid and the amino group of another, with the loss of a water molecule.

The loss of a protein's natural three-dimensional shape and biological activity caused by heat, extremes of pH or chemical agents, without breaking peptide bonds.

A molecule that contains both a positive and a negative charge on different sites; amino acids exist mainly in this dipolar form in neutral aqueous solution.

A chain reaction in which unsaturated monomers join together without losing any atoms, so the empirical formula of the polymer is the same as that of the monomer.

Heating natural rubber with sulphur to form cross-links between polymer chains, making the rubber harder, stronger and less sticky.

A chemical applied to living tissue, such as skin or wounds, to kill or inhibit microorganisms and prevent infection; it is milder than a disinfectant.