Definitions Flashcards
What is the definition for a catalyst?
A substance that alters the rate of a chemical reaction by providing an alternate pathway of a lower energy. It is not used up in a reaction.
What is the definition for activation energy?
The minimum energy that a particle needs in order to react; the energy (enthalpy) difference between the reactants and the transition state.
What is the definition for a acid?
Bronsted-Lowry = A proton donor; Lewis = an electron pair acceptor.
What is the definition for a base?
Bronsted-Lowry = A proton acceptor; Lewis = an electron pair donor
What is the definition for a buffer?
A solution that resists change of pH when small amounts of acid or base are added or on dilution.
What is the definition for a calorimeter?
An instrument for measuring the heat changes that accompany chemical reactions.
What is the definition for a carbocation?
An organic ion in which one of the carbon atoms has a positive charge.
What is the definition for chelation?
The process by which a multidentate ligand replaces a monodentate ligand in forming co-ordinate (dative) bonds to a transition metal ion.
What is the definition for chiral?
This means ‘handed’. A chiral molecule exists in two mirror image forms that are not superimposable.
What is the definition for chiral centre?
An atom to which four different atoms or groups are bonded. The presence of such an atom causes the parent molecule to exist as a pair of nonsuperimposable mirror images.
What is the definition for co-ordinate bond (dative bond)?
A covalent bond in which both the electrons in the bond come from one of the atoms forming the bond.
What is the definition for co-ordination number?
The number of ligand molecules bonded to a metal ion..
What is the definition for dipole - dipole force?
An intermolecular force that results from the attraction between molecules with permanent dipoles.
What is the definition for Displacement reaction?
A chemical reaction in which one atom or group of atoms replaces another in a compound, for example,
Zn + CuO –> ZnO + Cu
What is the definition for disproportionation?
Describes a redox reaction in which the oxidation number of some atoms of a particular element increases and that of other atoms of the same elements decreases.
What is the definition for dynamic equilibrium?
A situation in which the composition of a constant concentration reaction mixture does not change because both forward and backward reactions are proceeding at the same rate.
What is the definition for Electron pair repulsion theory?
A theory which explains the shapes of simple molecules by assuming that pairs of electrons around a central atom repel each other and thus take up positions as far away as possible from each other in space.
What is the definition for electronegativity?
The ability of an atom to attract a bonded pair of electrons in a covalent bond.
What is the definition for Electrophile?
An electron-deficient atom, ion or molecule that takes part in an organic reaction by attacking areas of high electron density in another reactant.
What is the definition for Electrophilic addition?
A reaction in which a carbon-carbon double bond is saturated, by the carbon-carbon double bond attacking an electrophile.
What is the definition for Electrostatic forces?
The forces of attraction and repulsion between electrically charged particles.
What is the definition for Elimination?
A reaction in which an atom or group of atoms is removed from a reactant.
What is the definition for Exothermic?
Describes a reaction in which heat energy is given out as the reactants change to products - therefore the temperature rises.
What is the definition for Fatty acid?
A long-chain carboxylic acid.
What is the definition for Free radical?
A chemical species with an unpaired electron- usually highly reactive.
What is the definition for Endothermic?
Describes a reaction in which heat energy is taken in as the reactants change to products, the temperature therefore drops.
What is the definition for Enthalpy change?
A measure of heat energy given out or taken in when a chemical or physical change occurs at constant pressure.
What is the definition for Entropy?
A numerical measure of disorder in a chemical system.
What is the definition for Equilibrium mixture?
The mixture of reactants and products formed when a reversible reaction is allowed to proceed in a closed container until no further change occurs. The forward and backward reactions are still proceeding but at the same rate.
What is the definition for Homologous series?
A set of organic compounds with the same functional group. The compounds differ in length of their hydrocarbon chains.
What is the definition for Hydration?
A reaction in which water is added.
What is the definition for Hydrogen bonding?
A type of intermolecular force in a which a hydrogen atom interacts with either N, O or F.
What is the definition for Hydrolysis?
A reaction of a compound or ion with water.
What is the definition for Incomplete combustion?
A combustion reaction in which there is insufficient oxygen for all the carbon in the fuel to burn to carbon dioxide. Carbon monoxide and/or carbon (soot) are formed.
What is the definition for Ionisation energy?
The energy required to remove an electron from one mole of gaseous ions to form one mole of gaseous +1 ions.
What is the definition for Isomer?
One or two (or more) compounds with the same molecular formula but different arrangement of atoms in space.
What is the definition for Ketone?
An organic compound with the general formula R2CO in which there is a C=O double bond.
What is the definition for Ligand?
An atom, ion or or molecule that forms a co-ordinate (dative) bond with a transition metal ion using a lone pair of electrons.
What is the definition for Maxwell-Boltzmann distribution?
The distribution of energies (and therefore speeds) of the molecules in a gas or liquid.
What is the definition for Mean bond enthalpy?
The average value of the bond dissociation enthalpy for a given type of bond taken from a range of different compounds.
What is the definition for Metallic bonding?
Describes a chemical bond in which outer electrons are delocalised within the lattice of metal ions.
What is the definition for Monomer?
A small molecule that combines with many other monomers to form a polymer.
What is the definition for Nucleophile?
A negative ion or molecule that is able to donate a pair of electrons and takes part in an organic reaction by attacking an electron deficient area in another reactant.
What is the definition for Nucleophilic substitution?
An organic reaction in which a molecule with a partially positively charged carbon atom is attacked by a reagent with a negative charge or partially negatively charged area (a nucleophile). It results in the replacement of one of the groups or atoms on the original molecule by the nucleophile.
What is the definition for Optical isomer?
Pairs of molecules that are non-superimposable mirror images.
What is the definition for Oxidation?
A reaction in which an atom or group of atoms losses electrons.
What is the definition for Oxidising agent?
A reagent that oxidises (removes electrons from) other species. An oxidising agent is reduced.
What is the definition for pH?
A scale for measuring acidity and alkalinity.
pH = -log10[H^+] in a solution.
What is the definition for Polar?
Describes a molecule in which the charge is not symmetrically distributed so that one area is slightly positively charged and another slightly negatively charged.
What is the definition for racemate?
A mixture of equal amounts of two optical isomers of a chiral compound. It is optically inactive.
What is the definition for rate-determining step?
The slowest step in the reaction mechanism. It governs the rate of the overall reaction.
What is the definition for redox reaction?
Short for reduction-oxidation reaction, it describes reactions in which electrons are transferred from one species to another.
What is the definition for reducing agent?
A reagent that reduces (adds electrons to) another species. The reducing agent is oxidised.
What is the definition for reduction?
A reaction in which an atom or group of atoms gain electrons.
What is the definition for standard molar enthalpy change of combustion?
The enthalpy change when 1 mole of a substance is completely burned in oxygen with all reactants and products in their standard states (298K and 100kPa)
What is the definition for standard molar enthalpy change of formation?
The enthalpy change when 1 mole of substance is formed from its elements with all reactants and products in their standard states (298K and 100kPa)
What is the definition for stereoisomer?
Isomers with the same molecular formula and the same structure, but different position of atoms in space.
What is the definition for structural isomer?
Isomers with the same molecular formula but a different structure.
What is the definition for Triglyceride?
An ester formed between glycerol (Propane-1,2,3-triol) and three fatty acid molecules.
What is the definition for Specific heat capacity?
The amount of heat needed to raise the temperature of 1g of substance by 1 K.
What is the definition for van der waals force?
A type of intermolecular force of attraction that is caused by instantaneous dipoles and acts between all atoms and molecules.
