Chem A2 1 definitions

Lattice enthalpy

The enthalpy change when one mole of an ionic compound is converted to gaseous ions

Enthalpy of atomisation

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

First electron affinity

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

Enthalpy of solution

The enthalpy change when one mole of a solute dissolves in water

Enthalpy of hydration

The enthalpy change when one mole of gaseous ions is converted to one mole of aqueous ions

Feasible

A reaction for which 🔼G<0

Entropy

A measure of disorder

Rate of reaction

The change of the concentration of a reactant or product with respect to time

Order of reaction (with respect to a reactant)

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

Order of reaction (overall)

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

Rate constant

The proportionality constant which links the rate of the reaction to the concentrations in the rate equation

Rate determining step

The slowest step in the mechanism of a reaction

Brønsted acid

Proton donor

Brønsted base

Proton accepter

Buffer solution

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

Monobasic acid

Donates one proton per molecule

Asymmetrical (chiral) centre

An atom which has four different atoms or groups attached

Optical isomers

Molecules which exist as non-superimposable mirror images

Optically active

A sample which rotates the plane of plane polarised light

Racemic mixture

A 50:50 mixture of two optical isomers

Monoester

An ester which contains only one ester group

Biodiesel

A fuel, similar to diesel, which is made from vegetable sources

transesterification

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

delocalisation (arenes)

the pi electrons are spread over several atoms