energetics II

Define enthalpy change of formation

The standard enthalpy change when one mole of a compound is formed from its elements under standard conditions and standard states

Define enthalpy change of atomisation

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

define ionisation energy

The enthalpy change needed to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous atoms with a 1plus charge

Define electron affinity

The enthalpy change when one mole of gaseous atoms gain one mole of electrons to form a 1- ion

Define enthalpy of lattice formation

The enthalpy change when one mole of a crystalline substance is formed from its constituent ions in gaseous state

Why is the second electron affinity of oxygen endothermic

As it takes energy to overcome the repulsive forces between the negative ion and the electron

What is the trend in first electron affinity as you go down group 7

Will become less exothermic as the atoms get larger and have more shielding so it’s easier to attract electrons to the atom and form a negative ion

What factors affect lattice enthalpies

The sizes of the ion and the charge on the ion

How does the size of the ion affect lattice enthalpy

The larger the ions, the less negative the enthalpies of lattice formation as the ions are larger the charges become further apart and so have a weaker attractive force between them

How does the charge of the ion affect lattice enthalpy

The bigger the charge on the ion the greater the attraction between the ion so the stronger the enthalpy lattice , more negative values

What is the trend of lattice enthalpies down any group

They become less negative

Define enthalpy change of solution

The enthalpy change when one mole of an ionic solid dissolves in water to form an infinitely dilute solution.

Define enthalpy change of hydration

The enthalpy change when one mole of an ion in its gaseous state is completely hydrated by water

What kind of a reaction is hydration

Exothermic