A2 1 chemistry

Ccea A2 unit 1

Asymmetric centre

An atom which has 4 different atoms or groups attached

Optical isomers

Molecules which exist as non-super impossible mirror images (in different directions)

Optically active

A sample which rotates the plane of plane polarised light

Racemic mixture

A 50:50 mixture of z optical isomers

Structural isomer

Isomers which have the same molecular formula but different structural formula

D (positive)

Rotates the polarised light clockwise

L (negative)

Rotates the polarised light anticlockwise

Stereospecific

When receptor sites will only bind to isomers in a specific way

Aldehyde/ketone

CnH2nO

Nucleophile

An ion or molecule, with a lone pair of electrons, that attacks regions of low electron density.

Mass spectrometry

a technique that separates particles according to their mass

Carboxylic acid

CnH2nO2

Infrared spectrum

graph of energy absorbed by a molecule as a function of frequency or wavelength of light

Dicarboxylic acid

a carboxylic acid that contains two carboxyl groups, one at each end of a carbon chain

Dibasic acid

Produces two H+ ions in solution

Tribasic acid

Produces three H+ ions in solution

Dimer

a compound whose molecules are composed of two identical monomers

Dipole-dipole

attractions between oppositely charged regions of polar molecules

Addition reaction

A reaction in which a pi bond of a double bond is broken and species are added across the bond

Electrophile

An ion or molecule which attracts a region of high electron density

Alkaline hydrolysis

When an ester is heated under reflux with a dilute alkali

Acid hydrolysis

A reaction heated under reflux with pure water, catalysed by a dilute acid

Transesterification

A reaction where the alkyl group of an ester is exchanged with the alkyl group of an alcohol

Biodiesel

A fuel similar to diesel, which is made from vegetable sources e.g. from a reaction of rapeseed oil with methanol

Monoester

An ester which contains only 1 ester group

Glycerol

Propane-1,2,3-triol

Hydrogenation

Unsaturated fats react with hydrogen in the presence of finely divided nickel at 180 degrees to achieve total saturation

Delocalisation

The pi electrons are spread out over several atoms

Buffer

A solution which resists changes in pH on addition of small amounts of acid or alkali

Weak acid

Acids which partially dissociate in solution to form H+ ions

Weak base

A base which partially dissociates in solution to form OH- ions

Strong acid

An acid which fully dissociates in solution to form H+ ions

Mono basic acid

Donate 1 proton (H+) per molecule

Dibasic acid

Donates 2 protons (H+) per molecule

Strong base

A base which fully dissociates in solution to form OH- ions

Bronsted acid

Proton donor

Bronsted base

Proton acceptor

Dynamic equilibrium

An equilibrium in which both the forward and reverse reaction are occurring at the same rate and the concentration of reactants and products remains constant

Le Chatlelier’s principle

Any change in a system at equilibrium results in a shift of equilibrium in the direction which minimises change

Hess’ law

Enthalpy change of an overall reaction is independent of the route by which a chemical reaction takes place

Entropy

A measure in the amount of disorder in a substance

Rate Determining Step

Slowest step in the mechanism for the reaction

Rate constant (k)

A positive number that varies with temp and defines the relationship between the rate of reaction and the concentrations in the rate equation

Rate equation

The relationship between the rate of reaction and the composition of the reaction mixture

Average rate

The average speed at which the reactants are converted to products during the reaction

Order of reaction of reactants

The power to which the concentration of a reactant is raised in the rate equation

Overall order

The sum of the powers to which the concentration terms are raised in the rate equation

Feasible reaction

A reaction which occurs 🔺G>0

Entropy

A measure of the amount of disorder in a substance

Gibbs free energy

Free energy change

1st Electron affinity

The Enthalpy change when 1 mole of gaseous atoms is converted into gaseous ions with a single negative charge

Enthalpy of atomisation

The enthalpy change when 1 mole of gaseous atoms is formed from the element in its standard state

Enthalpy of solution

The Enthalpy change when 1 mole of a solute dissolves in water

Enthalpy of hydration

The Enthalpy change when 1 mole of gaseous ions is converted to 1 mole of aqueous ions

Bond dissociation enthalpy

The energy charge when all the bonds of the same type in 1 mole of gaseous molecules are broken

2nd electron affinity

The enthalpy change when 1 mole of electrons is added to gaseous ions with a charge of 1 - to form gaseous ions with a charge of 2-

1st ionisation energy

The energy required to convert 1 mole of gaseous atoms to gaseous ions with a single positive charge

2nd ionisation energy

The energy required to convert 1 mole of gaseous ions with a single positive charge into gaseous ions with a double positive charge

Bond Enthalpy

The energy required to break 1 mole of a given bond averaged over many compounds

Standard enthalpy of formation

The enthalpy change when 1 mole of a compound is formed from its elements in their standard states under standard conditions

Lattice enthalpy

The Enthalpy change when 1 mole of an ionic compound is converted to gaseousions