Definitions Flashcards
Enthalpy change of reaction
The energy change associated with a given reaction
Enthalpy change of formation
The energy change that takes place when 1 mole of a compound is formed from its constituent elements in their standard conditions
Exotherminc process
Enthalpy change of combustion
The energy change that takes place when one mole of a substance is completely combusted
Enthalpy change of neutralisation
The energy change that takes is associated with the formation of 1 mole of water from a neutralisation reaction
Standard enthalpy change of atomisation
The energy change that takes place when one mole of gaseous atoms is formed from its element in its standard state
Endothermic process
First ionisation energy
The energy required to remove one electron from each atom in one mole of the gaseous element to form one mole of gaseous 1+ ions
Endothermic process
First electron affinity
The energy required to add electrons to atoms to form one mole of gaseous 1- ions from gaseous atoms
Exothermic process because electron is attracted into the outer shell of an atom by the nucleus
Second electron affinity
The energy required to add electrons to form one mole of gaseous 2- ions from gaseous 1- ions
Endothermic process because the electron is repelled by the 1- ion and this repulsion has to be overcome
Relative isotopic mass
The mass of an atom of an isotope compared with one-twelfth of the mass of an atom of carbon 12
Relative atomic mass
The weighted mean mass of an atom of an element compared with one twelfth the mass of an atom of carbon 12
A mole
The amount of any substance containing as many particles as there are carbon atoms in exactly 12g of the carbon 12 isotope
Activation energy
The minimum energy required to start a reaction by breaking bonds in the reactants
Amphoteric substances
substances that can react as both acids and bases e.g amino acids
Atomic orbital
A region of space where it is likely you will find electrons. Each orbital can hold up to 2 electrons with opposite spins.
Average bond enthalpy
The mean energy needed for 1 mole of a given type of gaseous bonds to undergo homolytic fission.
cis-trans isomerism
a type of E/Z isomerism where two substituent groups attached to each carbon atom of the C=C is the same
Covalent bond
A bond formed by a shared pair of electrons between nuclei
Dative covalent bond
A bond formed by a shared pair of electrons that has been provided by one of the bonding atoms only.
Displayed formula
A formula which shows the relative positioning of atoms and the bonds between them.
Disproportionation
The oxidation and reduction of the same element in a redox reaction
E/Z isomerism
A type of stereoisomerism that is caused by the restricted rotation around the double bond, two different groups are attached to each carbon atom of the C=C double bond.
Electron shielding
The repulsion between electrons in different inner shells. Shielding reduces the net attractive force from the positive nucleus on the outer electrons.
Electrophile
An electron pair acceptor
Empirical formula
The simplest whole number ratio of atoms of each element present in a compound.
Endothermic
A reaction in which the enthalpy change is positive, the enthalpy of the products is greater than that of the reactants. This results in heat being taken in from the surroundings.
Exothermic
A reaction in which the enthalpy change is negative, the enthalpy of the products is smaller than that of the reactants. Heat is lost to the surroundings (temperature increases)
Heterogeneous catalyst
A catalyst used in a reaction which is in a different phase from the reactant.
Heterolytic fission
When one bonding atom receives both electrons from the bonding pair.
Homolytic fission
When each bonding atom receives one electron from the bonded pair, forming two radicals.
Homogeneous catalyst
A catalyst used in a reaction that is in the same phase as the reactant
Ionic bond
The electrostatic attraction between oppositely charged ions
Isotopes
Atoms of the same element with different numbers of neutrons (same atomic number different mass number)
Le Chatelier’s principle
When a system in dynamic equilibrium is subjected to change, the equilibrium will shift to minimise the change.
London forces
Attractive forces between induced dipoles in neighbouring molecules
Lone pair
An outer shell pair of electrons that is not involved in chemical bonding
Metallic bonding
The electrostatic attraction between positive metal ions and delocalised electrons
Nucleophile
An electron pair donor
Permanent dipole
A small charge difference across a bond that results from a difference in electronegativity of the bonded atoms.
Permanent dipole-dipole interaction
A weak attractive force between permanent dipoles and permanent dipoles or induced dipoles in neighbouring polar molecules.
pi bonds
Sideways overlap of adjacent p-orbitals above and below the bonding C atoms
Radical
A highly reactive species with one or more unpaired electrons
Rate of reaction
The change in concentration of a reactant or a product in a given time
Salt
A chemical compound formed from an acid when an H+ ion from the acid has been replaced by a metal or another positive ion
Sigma bonds
Made by the direct overlap between orbitals on the bonding atoms
Specific heat capacity
The energy required to raise 1g of a substance by 1K
Stereoisomers
Organic compounds with the same molecular and structural formulae but have different arrangements of atoms in space.
Structural formula
Provides minimal detail to show the arrangement of atoms in a molecule
Structural isomers
Compounds with the same molecular formula but different structural formula
Water of crystallisation
Water molecules that form an essential part of the crystalline strutcure of a compound
