Key Terms Flashcards
acid
a species that releases H+ ions in an aq solution
acid dissociation constant Ka
the equilibrium constant that shows the extent of dissociation of a weak acid
acid-base pairs
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 monomers
addition reaction
a reaction in which a reactant is added to an unsaturated molecule to make a one saturated molecule
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 a straight or branched chains.
alkili
a type of base that dissolves in water forming hydroxide ions
alkanes
the hydrocarbon homologous series with single carbon to carbon bonds and the general formula CnH2n+2
alkenes
the hydrocarbon homologous series with at least 1 double carbon to carbon bond and the general formula CnH2n
alkyl group
a side chain formed by removing a hydrogen atom from an alkane parent chain, CH3
alkynes
the hydrocarbon homologous series with at least one triple carbon to carbon bond and the general formula CnH2n-2
aromatic
containing one or more benzene ring
atom economy
(sum of molar masses of desired products)/(sum of molar masses of all products)
atomic number
number of protons in the nucleus of an atom.
atomic orbital
A region around the nucleus that can hold up 2 electrons with opposite spins.
Average bond enthalpy
The average enthalpy change that takes place when breaking by homolytic fission 1 mol of a given type of bond in the molecules of a gaseous species.
Base
A compound that neutralises an acid to form a salt.
Binary compound
A compound containing 2 elements only.
Bond dissociation enthalpy
The enthalpy change that takes place when breaking by homolytic fission 1 mol of a given bond in the molecules of a gaseous species.
Bronsted-lowry acid
A species that is a proton donor.
Bronsted-lowry base
A species that is a proton acceptor.
Buffer solution
A system that minimises the 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 being used up in the process; a catalyst provides an alternative route 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 delta=0 ppm.
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 2 non-hydrogen groups and two hydrogen atoms around the c=c double bond; the cis isomer- Z- has H atoms on each carbon on the same side; the trans isomer- E- has H atoms on each carbon on different sides.
Closed system
A system isolated from it’s 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 bond- dative covalent bonds.
Concentration
The amount of solute, in moles, dissolved in 1dm3 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
Cojugate 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; dative covalent bond.
Coordination number
The total number of coordinate bonds formed between a central ion and ligands.
Covalent bond
The electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.
Dehydration
An elimination reaction in which water is removed from a saturated molecule to make an unsaturated molecule.
Delocalised electrons
Electrons that are shared between more than 2 atoms.
Desorption
Release of an adsorbed substance from a surface.
Dipole
A separation of 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 replaces 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 molecule and the bonds between them.
Disproportionation
A redox reaction in with the same element is 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 concs don’t change.
E/Z isomerism
A type of stereoisomerism in which different groups are 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.
Electronegativity
A measure of the attraction of a bonded atom of the pair of electrons in a covalent bond.
Electrophile
An atom or 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
Removal of a molecule from a saturated molecule to make an unsaturated molecule.
Empirical formula
The formula that shows the simplest whole-number ratio of atoms of each element present in a compound.
Enantiomers
Stereoisomers that are non-superimposable mirror images of each other- optical isomers.
End point
The point in a titration where the indicator changes colour; the end point indicates when the reaction is just complete.
Endothermic reaction
A reaction in which the enthalpy of the products is greater than the enthalpy of the reactants, resulting in heat being taken from the surroundings - delta H is +
Enthalpy H
The heat content that is stored in a chemical system.
Enthalpy change
The difference between the enthalpy of the products and the enthalpy of the reactants.
Enthalpy cycle
A diagram showing the 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 the reactants with the enthalpy of the products.
Entropy
The dispersal of energy within a 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 water and an ester.
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 is -
First ionisation energy
The energy requires to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions.
Fractional distilation
The separation of components in a liquid mixture by their different boiling points into fractions with different compositions.
Fragment ions
Ions formed from the breakdown of the molecular ion in a mass spectrometer.
Fragmentation
The process in mass spectrometry that causes a positive ion to split into smaller pieces, one of which is a positive fragment ion.
Free energy change- ΔG
The balance between enthalpy, entropy and temperature for a process given by;
ΔG= ΔH-TΔS. A process feasible when ΔG>0.
Giant covalent lattice
A 3D structure of atoms bonded together by strong covalent bonds.
Giant metallic lattice
A 3D structure of positive ions and delocalised electrons, bonded together by strong metallic bonds.
Giant ionic lattice
A 3D structure of oppositely charged ions, bonded together by strong ionic bonds.
Group
A vertical column in the periodic table. Elements in a group have similar chemical properties and their atoms have the same number of outer shell electrons.
half-life
The time taken for the concentration of a reactant to decrease by half
Hess’s Law
If a reaction can take place by more than one route and the initial and final conditions are the same, the total enthalpy change is the same for each route..
Heterogeneous catalyst
A reaction in which the catalyst has a different physical state from the reactants; frequently reactants are gases whilst the catalyst is a solid.
Fingerprint region
An area of an infrared spectrum below 1500cm-1 that gives a characteristic pattern for different compounds
First electron affinity
The enthalpy change that takes place when one electron is added to each atom in one mole of gaseous atoms to form one mole of gaseous 1- ions.
heterogeneous equilibrium
An equilibrium in which the species making up the reactants and products have different physical states.
heterolytic fission
The breaking of a covalent bond forming a cation and an anion.
Homogeneous catalyst
A reaction in which the catalyst and reactants are in the same physical state, which is most frequently the aqueous or gaseous state.
Homogeneous equilibrium
An equilibrium in which all the species making up the reactants and products have the same physical state.
Homologous series
A series of organic compounds with the same functional group but with each successive member differing by CH2.
Homolytic fission
The breaking of a covalent bond with one of the bonded electrons going to each atom, forming 2 radicals.
Hydrated
A crystalline compound containing water molecules.
Hydrogen bond
A strong dipole-dipole attraction between an electron- deficient hydrogen atom of -NH, -OH of HF on one molecule and a lone pair of electrons on a highly electronegative atom containing an N, O or F on a different molecule.
Hydrolysis
A reaction with water that breaks a chemical compound into 2 compounds, the H and OH in a water molecule becomes incorporated into the two other compounds.
Induces dipole-dipole interaction
Attractive forces between induced dipoles in different molecules- london forces.
Initial rate of reaction
The change in concs. of a reactant or product per unit of time at the start of the reaction t=0
initiation
The first stage in a radical reaction in which radicals start when a covalent bond is broken by homolytic fission of a covalent bond.
intermediate
A species formed during a reaction that reacts further and is not present in the final products.
Intermolecular forces
An attractive force between molecules. IM forces can be london forces, permanent dipole-dipole interactions or hydrogen bonding.
ion
A positively or negatively charged atom or a covalently bonded group of atoms where the number of electrons is different from the number of protons.
ionic bonding
The electrostatic attraction between positive and negative ions.
ionic product of water Kw
The product of the ions formed in the partial dissociation of water, given by Kw= [H+(aq)][OH-(aq)]
lattice enthalpy
The enthalpy change that accompanies the formation of one mole of an ionic compound from it’s gaseous ions under standard conditions.
Le Chatelier’s principle
When a system under dynamic equilibrium is subjected to an external change, the system readjusts itself to minimise the effect of the change and restore equilibrium.
Ligand
A molecule or ion that can donate a pair of electrons to the transmission metal ion.
Ligand substitution
A reaction in which one or more ligands in a complex ion are replaced by different ligands.l
limiting reagent
The reactant that is not in excess, which will be used up first and stop the reaction.
metallic bond
The electrostatic attraction between positive metal ions and delocalised electrons.
Neutralisation
A chemical reaction in which an acid and a base react together to form a salt and one mole of water.
nucleophile
An atom which is attracted to an electron- deficient centre or atom, where it donates a pair of electrons to form a new covalent bond.
Nucleophilic substitution
A reaction in which a nucleophile is attracted to an electron-deficient carbon atom, and replaces an atom or group of atoms on the carbon atom.
Optical isomers
Stereoisomers that are non-superimposable mirror images of each other; also called enantiomers.
Order
The power to which the conc. of a reactant is raised in the rate equation.
Overall order
The sum of the individual orders of reactants in the rate equation.
Oxidation number
A measure of the number of electrons that an atom uses to bond with atoms of other elements.
Pi- bond
A bond formed by the sideways overlap of 2 p-orbitals, with the electron density above and below the plane of the bonding atoms.
Partial dissociation
The splitting of some of a species in solution into an aq ion.
Pauling electronegativity value
A value assigned as a measure of the relative attraction of a bonded atom for the pair of electrons in a covalent bond.
