UPMSP Intermediate Chemistry key terms

The number of gram equivalents of solute dissolved in one litre of solution. It equals molarity multiplied by the number of equivalents per mole of solute and changes with the reaction the solute takes part in.

The number of moles of solute present in one kilogram of solvent. Because it depends on mass rather than volume, it stays unchanged when the temperature changes, unlike molarity.

The ratio of the number of moles of one component to the total number of moles of all components in a mixture. It is dimensionless and the sum of all mole fractions equals one.

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.

A property of a dilute solution that depends only on the number of solute particles present, not on their identity. Examples include relative lowering of vapour pressure, boiling point elevation and freezing point depression.

The extra pressure that must be applied to a solution to stop solvent from passing through a semipermeable membrane into it. It equals the product of molarity, gas constant and absolute temperature for dilute solutions.

The ratio of the observed colligative effect to the value expected for a non-dissociating solute. It is greater than one for electrolytes that dissociate and less than one for solutes that associate.

A device that converts chemical energy of a redox reaction into electrical energy (galvanic cell) or uses electrical energy to drive a non-spontaneous reaction (electrolytic cell). It consists of two electrodes in contact with electrolytes.

The potential of an electrode measured against the standard hydrogen electrode under standard conditions of one molar concentration, one bar pressure and 298 K. It indicates the tendency of a species to gain electrons.

An equation relating the cell or electrode potential to the standard potential and the reaction quotient. It shows how changing ion concentrations or gas pressures shifts the potential from its standard value.

The conductance of a solution containing one mole of electrolyte, obtained by dividing conductivity by molar concentration. It increases on dilution because dissociation increases and ion-ion interactions decrease.

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 number in the formula. It allows calculation of limiting values for weak electrolytes.

The mass of substance deposited or liberated at an electrode is proportional to the quantity of charge passed, and for a fixed charge it is proportional to the equivalent mass of the substance.

The proportionality constant in a rate law that equals the reaction rate when all reactant concentrations are unity. Its value depends on temperature and the presence of a catalyst, and its units reveal the reaction order.

The sum of the powers to which reactant concentrations are raised in the experimentally determined rate law. It is found by experiment and may differ from the stoichiometric coefficients of the balanced equation.

The number of reacting species that collide simultaneously in an elementary step of a reaction mechanism. It is a whole number and applies only to elementary steps, not to overall reactions.

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 initial concentration and equals 0.693 divided by the rate constant.

An equation expressing the rate constant as the product of a pre-exponential factor and an exponential term containing activation energy and temperature. It explains why reaction rates rise steeply with heating.

The minimum extra energy that colliding reactant molecules must possess for a collision to convert them into products. A larger value makes the reaction slower and more temperature sensitive.

Elements whose atoms or common ions have a partly filled d subshell. They typically show variable oxidation states, form coloured ions and complexes, and act as catalysts.

An ion or neutral molecule that donates one or more electron pairs to a central metal ion to form a coordinate bond in a complex. Common examples are water, ammonia, chloride and cyanide.

The number of donor atoms of ligands directly bonded to the central metal ion in a complex. It is commonly four or six, giving tetrahedral, square planar or octahedral geometry.

The separation of the five d orbitals of a metal ion into sets of different energy when ligands approach it. The size of this splitting decides the colour and magnetic behaviour of the complex.

A metal complex in which a single ligand occupies two or more coordination positions on the same central ion, forming a ring. Such complexes are usually more stable than similar complexes with unidentate ligands.

A two-step substitution in which the leaving group departs first to form a carbocation, which is then attacked by the nucleophile. It is favoured by tertiary substrates and polar protic solvents and gives racemisation.

A one-step substitution in which the nucleophile attacks the carbon from the side opposite the leaving group while the leaving group departs. It shows second-order kinetics and inverts the configuration at the carbon.

Aryl halides resist nucleophilic substitution because the carbon-halogen bond has partial double-bond character and the ring is electron rich. Substitution requires strong conditions and proceeds through a benzyne or addition-elimination route.

The preparation of an ether by treating an alkoxide ion with a primary alkyl halide through an SN2 reaction. Using a tertiary halide instead causes elimination and gives an alkene as the main product.

The formylation of phenol by treatment with chloroform and aqueous sodium hydroxide, giving salicylaldehyde as the major product. It involves a dichlorocarbene intermediate that attacks the ring.

The base-catalysed reaction in which an enolate of one aldehyde or ketone adds to the carbonyl carbon of another, forming a beta-hydroxy carbonyl compound that may lose water to give an alpha,beta-unsaturated product.

A disproportionation shown by aldehydes having no alpha hydrogen, such as methanal and benzaldehyde, when heated with concentrated alkali. One molecule is oxidised to a carboxylate salt and another is reduced to an alcohol.

A test that distinguishes primary, secondary and tertiary amines by reacting them with benzenesulphonyl chloride. Primary amines give a soluble sulphonamide, secondary give an insoluble one, and tertiary do not react.

The pair of cyclic stereoisomers of a sugar that differ only in the configuration at the hemiacetal carbon, called the anomeric carbon. The alpha and beta forms of glucose are examples.

The amide linkage formed between the carboxyl group of one amino acid and the amino group of another with loss of water. It is planar and rigid, and its repeated sequence builds the polypeptide chain of a protein.

The loss of the three-dimensional shape and biological activity of a protein caused by heat, extremes of pH or chemicals. The primary structure stays intact but hydrogen bonds and other secondary interactions break.

A point defect in an ionic crystal in which a cation and an anion are missing from their lattice sites in equal numbers. It keeps the crystal electrically neutral and lowers its density.

A point defect in which an ion leaves its normal lattice site and occupies an interstitial position in the same crystal. It usually involves the smaller cation and does not change the density of the solid.

The smallest repeating portion of a crystal lattice which, when repeated in three dimensions, generates the whole crystal. It is described by edge lengths and the angles between them.