Lattice Enthalpy and Free Energy

The Enthalpy change accompanying the removal of an electron from each ion in one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions

Charge on the cation gets larger across the period and the ions get smaller, the ionic charge is concentrated into a smaller volume so charge density increases. Attraction and bonding to water molecules will be stronger, more energy released as the hydrated ion is formed.

The entropy change that accompanies a reaction in the molar quantities expresses in a chemical equation under standard conditions, all reactants and products being in their standard states

Lattice enthalpy is a measure of the strength of the electrostatic forces of attraction between the oppositely charged ions. The more energy released, so the more exothermic the lattice enthalpy, the stronger the electrostatic attraction

Activation energy not been reached

Cannot be measured directly as it is impossible to form one mole of an ionic lattice from gaseous ions

Ionic size Ionic charge

a) The change has made the system more random b) The change has made the system more ordered

A large negative value for lattice enthalpy shows that there are strong electrostatic forces of attraction between the oppositely charge ions

S - the quantitative measure of the degree of disorder in a system

The Enthalpy change that takes place when one mole of isolated gaseous ions is dissolved in water forming one mole of aqueous ions under standard conditions

kJ mol^-1

The Enthalpy change that accompanies the addition of one electron to each ion in one mole of gaseous 1- ions to form one mole of gaseous 2- ions

At room temp. Enthalpy content of chemical system decreases during the reaction, excess energy is released into the surroundings, increasing stability

Enthalpy change which takes place when one mole of gaseous atoms is formed from its element in its standard state

Charge and radius

kJ mol -1

The Enthalpy change that takes place when one mole of a compound is completely dissolved in water under standard conditions

Consideration of enthalpy and entropy change means it is energetically possible for a reaction to take place

(Delta G) = enthalpy change - temp. x entropy change It is the balance between the enthalpy, entropy and temperature for a process. A process can take place spontaneously when DG is less than 0

Entropy change must be positive and temperature must be high enough so that when multiplied by entropy change, it is greater than enthalpy change

The Enthalpy change that accompanies the formation of 1 mole of an ionic compound from its gaseous ions under standard conditions

As the charge density gets smaller, the electrostatic attraction between the ions decreases, lattice enthalpy becomes less exothermic

The Enthalpy change accompanying the addition of an electron to each atom in one mole of gaseous atoms to form one mole of gaseous 1- ions