01 - Key definitions Flashcards
Acid
A species that releases H+ ions in aqueous solution.
Acid dissociation constant
The equilibrium constant that shows the extent of dissociation off a weak acid.
Acid-base pair
A pair of two species that transform into each other by gain or loss of a proton.
Activation Energy
The minimum energy required to start a reaction by the breaking of bonds.
Actual Yield
The amount of product obtained from a reaction.
Addition Polymerisation
Formation of a very long molecular chain, by repeated addition reactions of many unsaturated alkene molecules (monomers).
Addition Reaction
A reaction in which two reactants join together to form one product.
Adsorption
The process that occurs when a gas or liquid or solute is held to the surface of a solid.
Alicyclic
Containing carbon atoms joined together in a ring that is not aromatic.
Aliphatic
Containing carbon atoms joined together in straight or branched chains.
Alkali
A type of base that dissolves in water forming hydroxide ions, OH- ions.
Alkanes
The hydrocarbon homologous series with single carbon-carbon bonds and the general formula CnH2n+2.
Alkenes
The hydrocarbon homologous series with at least one carbon=carbon double bond.
Alkyl group
A side chain formed by removing a hydrogen atom removed from an alkane parent chain.
Alkynes
The hydrocarbon homologous series with at least one triple carbon-to-carbon bond.
Amount of substance
The quantity whose unit of the mole, used as a means of counting any species such as atoms, ions and molecules.
Anhydrous
Containing no water molecules.
Anion
A negatively charged ion with more electrons than protons.
Aromatic
Containing one or more benzene rings.
Atom Economy
(Sum of molar masses of desired products) / (Sum of molar masses of all products).
Atomic number
Also known as proton number and shows the number of protons in the nucleus of an atom.
Atomic orbital
A region around the nucleus that can hold up to two electrons.
Average Bond Enthalpy
The average enthalpy change that takes place when breaking by homolytic fission 1mol of a given type of bond in the molecules of a gaseous species.
Avogadro constant
The number of atoms per mole of the carbon-12 isotope (6.02 x 10*23 mol).
Base
A compound that neutralises an acid to form a salt.
Binary compound
A compound containing two elements only.
Bond angle
The angle between two bonds at an atom.
Bond Dissociation Enthalpy
The enthalpy change that takes place when breaking by homolytic fission 1mol of a given bond in the molecules of a gaseous species.
Bonded Pair
A pair of electrons shared between two atoms to make a covalent bond.
Bronsted-Lowry Acid
A species that is a proton, H+, donor.
Bronsted-Lowry Base
A species that is a proton, H+, acceptor.
Buffer solution
A system that minimises pH changes on addition of small amounts of an acid or a base.
Carbocation
An ion that contains a positively charged carbon atom.
Catalyst
A substance that increases the rate of a chemical reaction without getting used up in the process; a catalyst provide an alternative route/reaction pathway for the reaction with a lower activation energy.
Cation
A positively charged ion with fewer electrons than protons.
Chain reaction
A reaction in which the propagation steps release new radicals that continue the reaction.
Chemical Shift
A scale, in ppm, that compares the frequency of an NMR absorption with the frequency of the reference TMS at 0ppm.
Chiral carbon
A carbon atom attached to four different atoms or groups of atoms.
Chromatogram
A visible record showing the result of separation of the components of a mixture by chromatography.
Cis-trans isomerism
A special type of E/Z isomerism in which there are two non-hydrogen groups and two hydrogen atoms around the C=C double bond: the Cis isomer (Z isomer) has H atoms on each carbon on the same side; the Trans isomer (E isomer) has H atoms on each carbon on opposite/different sides.
Closed system
A system isolated from its surroundings.
Collision Theory
Two reacting particles must collide for a reaction to occur, and must be in the correct orientation and have sufficient energy to overcome the activation energy of the reaction.
Complex ion
A transition metal ion bonded to ligands by coordinate bonds (dative covalent bonds).
Concentration
The amount of solute, in moles, dissolved in 1dm*3 of solution.
Condensation Reaction
A reaction in which two small molecules react together to form a larger molecule with elimination of a small molecule such as water.
Conjugate Acid
A species that releases a proton to form a conjugate base.
Conjugate Base
A species that accepts a proton to form a conjugate acid.
Coordinate bond
A shared pair of electrons in which the bonded pair has been provided by one of the bonding atoms only; also called a dative covalent bond.
Coordination number
The total number of coordinate bonds formed between a central metal ion and ligands.
Covalent Bond
The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.
Dative covalent
A shared pair of electrons in which the bonded pair has been provided by one of the bonding atoms only; also known as a coordinate bond.
Dehydration
An elimination reaction in which water is removed from a saturated molecule to make an unsaturated molecule.
Delocalised electron
Electrons which are shared between more than two atoms.
Desorption
Release of an absorbed substance from a surface.
Dipole
A separation in electrical charge so that one atom of a polar covalent bond, or one end of a polar molecule, has a small positive charge and the other has a small negative charge.
Displacement Reaction
A reaction in which a more reactive element displaces a less reactive element from an aqueous solution of its ions.
Displayed formula
A formula showing the relative positioning of all the atoms in a compound/molecule and the bonds between them.
Disproportionation
A redox reaction in which the same element has been both oxidised and reduced.
Dynamic equilibrium
The equilibrium that exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction and concentrations do not change.
E/Z isomerism
A type of stereoisomerism in which different groups attached to each carbon of a C=C double bond may be arranged differently in space because of the restricted rotation of the C=C bond.
Electron configuration
A shorthand representation that shows the arrangement of electrons in sub-shells of an atom.
Electronegativity
A measure of the attraction of a bonded atom for the pair of electrons in a covalent bond.
Electrophile
An atom (or a group of atoms) which is attracted to an electron-rich centre or atom, where it accepts a pair of electrons to form a new covalent bond.
Electrophilic Addition
An addition reaction in which the first step is attack by an electrophile on a region of high electron density.
Electrophilic Substitution
A type of substitution reaction in which an electrophile is attracted to an electron-rich centre or atom, where it accepts a pair of electrons to form a new covalent bond.
Elimination reaction
The removal of a molecule from a saturated molecule to make/form an unsaturated molecule.
Empirical Formula
The smallest and simplest whole-number ratio of atoms of elements present in a compound.
Enantiomers
Stereoisomers that are non-superimposablemirror images of each other; also called optical isomers.
End Point
The point in a titration where an indicator changes colour; the end point indicates when the reaction is just complete.
Endothermic Reaction
A reaction in which the enthalpy of products is greater than the enthalpy of reactants, resulting in heat being taken in form the surroundings (delta H is +).
Enthalpy (H)
The heat content that is stored in a chemical system.
Enthalpy Change (delta H)
The difference between the enthalpy of products and the enthalpy of reactants.
Enthalpy Cycle
A diagram showing alternative routes between reactants and products which allows the indirect determination of an enthalpy change from other known enthalpy changes using Hess’s Law.
Enthalpy Profile Diagram
A diagram for a reaction to compare the enthalpy of reactants with the enthalpy of products.
Entropy
The used for the dispersal of energy and disorder within chemicals making up the chemical system.
Equilibrium constant
A measure of the position of equilibrium; the magnitude of an equilibrium constant indicates whether there are more reactants or more products in an equilibrium system.
Equivalence Point
The point in a titration at which the volume of one solution has reacted exactly with the volume of the second solution.
Esterification
A reaction in which a carboxylic acid reacts with an alcohol to form an ester and water.
Exothermic reaction
A reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants, resulting in heat loss to the surroundings (delta H-).
