Definitions Flashcards
Endothermic
A reaction in which the enthalpy of the products is greater than the enthalpy of the reactants
Exothermic
A reaction in which the enthalpy of the products is less than the enthalpy of reactants
Conservation of Energy
Energy can neither be created or destroyed, it can only be transformed from one form to another
Hess’ law
The enthalpy change of a reaction is independent of the route taken provided initial and final conditions remain the same
Standard Conditions
298K, 100Kpa
Standard enthalpy change
Heat energy change at constant pressure under standard conditions
Enthalpy of formation
Enthalpy change when one mole of compound is formed from its constituent elements under standard condtions (100kpa, 298K)
Enthalpy of combustion
Enthalpy change when one mole of substance is burnt completely in oxygen under standard conditions (298k, 100kpa)
Enthalpy of neutralisation
Enthalpy change when one mole of water is produced in a neutralisation reaction under standard conditions (298k, 100kpa)
1st ionisation reaction
Energy change when one mole of gaseous atoms is converted into gaseous ions with a singly positive charge.
1st electron affinity
Energy change when one mole of gaseous atoms is converted into gaseous ions with a singly negative charge
Bond dissociation energy
energy change required to break one mole of a specific bond
average bond enthalpy
energy change required to break one mole of a specific bond averaged over many compounds
Enthalpy of atomisation
enthalpy change when one mole of gaseous atoms is formed from its element in its standard state under standard conditions
Lattice enthalpy
Enthalpy change when one mole of ionic compound is converted into gaseous ions
Enthalpy of solution
Enthalpy change when one mole of solute dissolves in water
Enthalpy of hydration
Enthalpy change when one mole of gaseous ions is converted into one mole of aqueous ions.
Feasible/aqueous
A reaction for which ^G<0
Entropy(s)
a measure of disorder/ randomness
Gibbs free energy
^G= ^H - T^S
Isomers
Compounds with same formula but a different arrangement of atoms within compound
Structural isomers
Compounds with same molecular formula but different structural formula
Stereoisomers
same structural formula but a different arrangement of atoms in space
Geometric isomers
same structural formula but a different arrangement of atoms in space due to the presence of at least 1 C=C
E/Z or Cis/Trans isomerism
Restricted rotation around the C=C bonds in the compound. each atom of C=C has 2 different atoms/ groups of atoms attached.
Optical isomers
super-imposable mirror images of one another, have an asymmetric centre.
Asymmetric/ chiral centre
atom bonded to 4 different atoms/groups of atoms in a tetrahedral arrangement.
optically active
sample which rotates the plane of plane polarised light
Racemic mixture
50;50 mixture of 2 optical isomers
optically inactive
optical isomers are in a 50;50 mixture, they rotate the plane of plane polarised light in equal but opposite directions.
Stereospecific
active site only bonds when the molecules have a particular orientation/ shape.
reflux
repeated boiling and condensing of a reaction mixture
hydrolysis
breaking up molecules by their reaction with water
nucleophile
molecule with a lone pair of electrons, which attacks regions of low electron density
hydrogenation
addition of a hydrogen molecule across C=C
elimination
a reaction in which a smaller molecule is removed from a larger molecule
electrophile
ion/molecule which attacks regions of high electron density
substitution
replacement of an atom/ group of atoms with another atom/ group of atoms
delocalisation (arenes)
pie electrons are spread over several atoms
chromophore
group of atoms and electrons forming part of an organic molecule which causes it to be coloured
conjugation
special stability associated with 3 or more adjacent, parallel, overlapping p orbitals, resulting in increased electron delocalisation and longer electron wavelength.
Reduction
Loss of oxygen, gain of hydrogen
Nucleophile
Ion/molecule with a lone pair of electrons which attacks regions of low electron density
Addition
Pie bond of double bond broken and species added
Hydrolysis
Splitting bonds using water
Monoester
Ester which contains only one ester group
Transesterification
Reaction where alkyl group of an ester is exchanged with alkyl group of an alcohol
Biodiesel
Fuel similar to diesel, made from vegetable sources eg; the reaction of rapeseed oil and methanol
Delocalisation
Pie electrons spread over several atoms
Hydrolysis
Breaking up molecules by their reaction with water
Hydrogenation
Addition of hydrogen molecules across C=C
Condensation reaction
2 molecules combine to form one large molecule while releasing a small molecule eg; H2O, HCl
Triglyceride
Chemical compound which contains 1 molecule of glycerol and 3 fatty acids
Saturated
Contains no C=C or C triple bond C
Monounsaturated
Molecule contains one C=C per molecule
Polyunsaturated
Molecule contains 2 or more C=C per molecule
Saponification
Alkaline hydrolysis of a fat/oil
