Glossary Flashcards
Bronsted-Lowry Acid
A proton donor
Lewis Acid
An electron pair acceptor
Acid derivative
An organic compound related to a carboxylic acid of formula RCOZ, where z = -Cl, -NHR, -OR, or -OCOR.
Activation energy
The minimum energy that a particle needs in order to reach; the energy (enthalpy) difference between the reactants and the transition state.
Aldehyde
An organic compound with the general formula RCHO
Alkaline earth metals
The metals in group 2 of the periodic table
Alkane
A saturated hydrocarbon with only C-C and C-H single bonds, with the geral formula of C(n)H(2n+2)
Allotropes
Pure elements which can exist in different physical forms in which their atoms are arranged differently. For example, diamond, graphite and buckminster-fullerene are allotropes of carbon
Anaerobic respiration
The process by which energy is released and new compounds formed in living things in the absence of oxygen
Atom economy
This describes the efficiency of a chemical reaction by comparing the total number of atoms in the product with the total number of atoms in the starting materials. it is defined by
% atom economy = (mass of desired products)/(total mass of reactants)
Atomic orbital
A region of space around an atomic nucleus where there is a high probability of finding an electron
Avogadro constant
The total number of particles in a mole of substance. Also called the Avogadro number. It is numerically equal to 6.022 x 10^23
Bronsted-Lowry Base
A proton acceptor
Lewis Base
An electron pair donor
Base peak
The peak representing the ion of greatest abundance (the tallest peak) in a mass spectrum
Bond dissociation enthalpy
The Enthalpy change required to break a covalent bond with all species in the gaseous state
Buffer
A solution that resists change of pH when small amounts of acid or base are added or on dilution
Calorimeter
An instrument for measureing the heat changes that accompany chemical reactions
Carbocation
An organic ion in which one of the carbon atoms has a positive charge
Carbon-neutral
A process, or series of processes in which as much carbon dioxide is absorbed from the air as is given out.
Catalyst
A substance that alters the rate of a chemical reaction but is not used up in the reaction
Catalytic cracking
The breaking, with the aid of a catalyst, of long-chain alkane molecules(obtained from crude oil) into shorter chain hydrocarbons (some of which are alkenes)
Chelation
The process by which a multidentate ligand replaces a monodentate ligand in forming co-ordinate (dative) bonds to a transition metal ion
Chemical feedstock
The starting materials in an industrial chemical process
Chiral
Coming from the Greek for ‘handed’. A chiral molecule exists in two mirror image forms that are not superimposable
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
Co-ordinate bond
A covalent bond in which both the electrons come from one of the atoms forming the bond. (also called a dative bond.)
Co-ordination number
The number of ligand molecules bonded to a metal ion
Covalent bonding
Describes a chemical bond in a pair of electrons are shared between two atoms
Dative covalent bonding
Covalent bonding in which both the electrons in the bond come from one of the atoms in the bod (also known as Co-ordinate bonding
Delocalisation
Describes the process by which electrons are spread over several atoms and help bond them together
Delocalised
Describes elections that are spread over several atoms and help to bond them together
Dipole-dipole force
An intermolecular force that results from the attraction between molecules with permanent dipoles
Displacement reaction
A chemical reaction in which one atom or group of atoms replace another in a compound, for example,
Zn + CuO => ZnO + Cu
Displayed formula
The formula of a compound drawn out so that each atom and each bond is shown
Disproportionation
describes a redox reaction in which the oxidation number of some atoms of a particular element increases and that of of other atoms of the same element decreases
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
Electron density
The probability of electrons being found in a particular volume of space
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
Electronegativity
The power of an atom to attract the electrons in a covalent bond
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
Electrophilic addition
A reaction in which a carbon-carbon double bond is saturated, by the carbon-carbon double bond attacking an electrophile
Electrostatic forces
The forces of attraction and repulsion between electrically charged particles
Elimination
A reaction in which an atom or group of atoms is removed from a reactant
Empirical formula
The simplest whole number ration of atoms or each element in a compound
Enantiomer
one of a pair of nonsuperimposable mirror image isomers
Endothermic
Describes a reaction in which heat energy is taken in as the reactants change to products the temperature therefore drops
End point
The point in a titration when the volume of the reactant added just causes the colour of the indicator to change
Enthalpy change
A measure of heat energy given out or taken in when a chemical or physical change occurs at constant pressure
Enthalpy diagrams
Diagrams in which the enthalpies (energies) of the reactants and products of a chemical reaction are plotted on a vertical scale to show their relative levels
Entropy
A numerical measure of disorder in a chemical system
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.
Equivalence point
The point in a titration at which the reaction is just complete
Exothermic
Describes a reaction in which heat energy is given out as the reactants change to products - the temperature therefore rises
Fatty acid
A long-chain carboxylic acid
Fingerprint region
The area of an infra-red spectrum below about 1500 cm^-1. it is caused by complex vibrations of the whole molecule and is characteristic of a particular molecule
Fraction
A mixture of hydrocarbons collected over a particular range of boiling points during the fractional distillation of crude oil.
Free radical
A chemical species with an unpaired electron - usually highly reactive
Functional group
An atom or group of atoms in an organic molecule which is responsible for the characteristic reactions of that molecule
Group
A vertical column of elements in the periodic table. The elements have similar properties because they have the same outer electron arrangement
Half equation
An equation for a redox reaction which considers just on of the species involved and shows explicitly the electrons transferred to or from it
Homologous series
A set of organic compounds with the same functional group. The compounds differ in the length of their hydrocarbon chains
Hydration
A reaction in which water is added
Hydrogen bonding
A type of intermolecular force in which a hydrogen atom (H^δ+) interacts with a more electronegative atom with a δ- charge
Hydrolysis
A reaction of a compound or ion with water
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
Inductive effect
the electronreleasing effect of alkyl groups such as CH3 or -C2H5
Ionic bonding
Describes a chemical bond in which an electron or electrons are transferred from one atome to another, resulting in the formation of oppositely charged ions with electrostatic forces of attraction betwwen them
Ionisation energy
The energy required to remove a mole of electrons from a mole of isolated gaseous atoms or ions
Isome
One of two (or more) compounds with the same molecular formula but different arrangement of atoms in space
Ketone
An organic compound with the general formula R2CO in which there is a C=O double bond not on the terminal carbon
Lattice
A regular three-dimensional arrangement of atoms, ions or molecules
Leaving group
In an organic substitution reaction, the leaving group is an atom or group of atoms that is effected from the starting material, normally taking with it an electron pair and forming a negative ion
Ligand
An atom, ion or molecule that forms a co-ordinate (dative) bond with a transition metal ion using a lone pair of electrons
Lone pair
A pair of electrons in the outer shell of an atom that is not involved in bonding
Maxwell- Boltzmann distribution
The distribution of energies (and therefore speeds) of the molecules in a gas or liquid
Mean bond enthalpy
The average value of the bond dissociation enthalpy for a give type of bond taken from a range of different compounds
Metallic bonding
Describes a chemical bond in which outer electrons are delocalised within the lattice of metal ions
Mole
A quantity of a substance that contains the Avogadro number (6.022 X 10^23) of particles (e.g. atoms, molecules or ions)
Molecular formula
A Formula that tells us the actual number of atoms of each different element that make up a molecule of a compound
Molecular ion
In mass spectrometry this is a molecule of a the sample which has been ionised but which has not broken up during its flight through the instrument
Monomer
A small molecule that combines with man other monomers to form a polymer
Nucleons
Prons and neutrons - the sub-atomic particles found in the nuclei of atoms
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
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
Nucleus
The tiny, positively charged centre of an atom composed of protons and neutrons
Optical isomer
Pairs of molecules that ate non superimposable mirror images
Order of reaction
In the rate expression, this is the sum of the powers to which the concentrations of all the species involved in the reaction are raised.
Oxidation
A reaction in which an atom or groups of atoms loses electrons
Oxidation state
The number of electrons lost or gained by an atom in a compound compared to the individual atom. It forms the basis of a way of keeping track of redox (electron transfer) reactions. Also called oxidation number
Oxidising agent
A reagent that oxidises (removes electrons from) another species
Percentage yield
In a chemical reaction this is the actual amount of product produced divided by the theoretical amount (predicted from the chemical equation expressed as a percentage
Period
A horizontal row of elements in the periodic table. There are trends in the properties of the eleents as we cross a period
Periodicity
The regular recurrence of the properties of elements when they are arranged in atomic number order as in the periodic table
pH
A scale for measuring acidity and alkalinity.
pH = -log[H+] in a solution
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
Polarised
This describes an atom or ion where the distribution of charge around it is distorted from the spherical
Positive inductive effect
Describes the tendency of some atoms or groups of atoms to release electrons via a covalent bond
Proton number
The number of protons in the nucleus of an atom; the same as the atomic number
Protonated
Describes an atom, molecule or ion to which a proton (an H+ ion) has been added
Racemate
A mixture of equal amounts of two optical isomers of a chiral compound. It is optically inactive
Rate constant
The constant of proportionality in the rate expression
Rate-determining step
The slowest step in the reaction mechanism. It governs the rate of the overall reaction
Rate expression
A mathematical expression showing how the rate of a chemical reaction depends on the concentrations of various chemical species involved
Reaction mechanism
The series of simple steps that lead from reactants to products in a chemical reaction
Redox reaction
Short for reduction-oxidation reaction, it describes reactions in which electrons are transferred from one species to another
Reducing agent
A reagent that reduces (adds electrons to) another species
reduction
A reactions in which an atom or group of atoms gain electrons
Ar / Mr
the average mass of a particle / a twelth of the mass of a carbon 12 atom
Saturated hydrocarbon
A compound containing only hydrogen and carbon with only C-C and C-H single bonds, i.e. one to which no more hydrogen can be added
Specific heat capacity
The amount of heat needed to raise the temperature of 1g of substance by 1 K
Spectator ions
Ions that are unchanged during a chemical reaction, that is, they take no part in the reaction
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 (298 K and 100KPa)
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 (298 K and 100 KPa)
Stereoisomer
Isomers with the same molecular formula and the same structure, but a different position of atoms in space
Stoichiometry
Describes the simple whole number ratios in which chemical species react
Strong acid
An acid that is fully dissociated into ions in solution
Strong nuclear force
The forces that holds protons and neutrons together within the nucleus of the atom
Structural formula
A way of writing the formula of an organic compound in which bonds are not shown but each carbon atom is written separately with the atoms or groups of atoms attached to it
Structural isomer
Isomers with the same molecular formula but a different structure
Thermochemical cycle
A sequence of chemical reactions (with their enthalpy changes) that convert a reactant into a product. The total enthalpy change of the sequence of reactions will be the same as that for the conversion of the reactant to the product directly (or by any other route (as used in Hess cycles))
Triglyceride
An ester formed between glycerol (propane-1,2,3-triol) and three fatty acid molecules
van der Waals force
A type of intermolecular force of attraction that is caused by instantaneous dipoles and acts between all atoms and molecules
Weak acid
An acid that is only slightly dissociated into ions in solution. They will also have a Ka value
