Enthalpy and Entropy Key Terms and Definitions Flashcards
Ionic Bonding
The electrostatic attraction between positive and negative ions
Lattice Enthalpy
The enthalpy change on formation of one mole of an ionic lattice from gaseous ions
First Ionisiation Energy
The energy required to remove one mole of electrons from one mole of gaseous atoms
Second Ionisation Energy
The energy required to remove one mole of electrons from one mole of gaseous 1+ ions
Enthalpy Change of Atomisation
The enthalpy change on forming one mole of gaseous atoms from an element in its standard state
Enthalpy Change of Formation
The enthalpy change on formation of one mole of a compound from its elements
Electron Affinity
The enthalpy change when an electron is added to every atom/ion
Standard Enthalpy Change of Compound
The enthalpy change that accompanies a reaction when a compound is formed
Enthalpy Change of a Solution
The enthalpy change on dissolving one mole of a solute
When a solid dissolves, two processes occur :
1) the ionic lattice breaks into gaseous ions
2) gaseous ions dissolve in water due to the attraction between ions and polar molecules
Enthalpy Change of Hydration
The enthalpy change on dissolving one mole of gaseous ions in water, always exothermic
Factors affecting Lattice Enthalpies
- ionic size
- ionic charge
small ions are closer together, leading to a stronger attraction between the atoms, higher charges lead to stronger attractions also
Factors affecting Hydration Enthalpies
- size of ions
- charge of ions
depends on the ability of the ion to attract polar water molecules, the attraction is strongest with ions with a higher charge density (small radius, high charge)
Entropy is…
… the quantitative measure of disorder in a system
Gases have a… entropy than solids?
greater entropy, as particles in a solid, are fixed and unmoving, but particles in a gas are randomly moving and disordered
