Ionic Lattices Flashcards
What is an energy level diagram
Show no Ea hump just two lines with arrow between
What are standard conditions for comparing enthalpy changes
298K, 100kPa, all reactants and products in standard states, solutions at concen of 1moldm-3
How is standard enthalpy change of formation written
△f H circle with line through
What is the standard enthalpy of atomisation of an element
The energy change needed to produce one mole of gaseous atoms of an element from its standard state eg 1/2I2(s) ——> I(g)
What is lattice energy of formation of a compound and how to represent and unit
The energy change when one mole of a solid ionic compound is formed from free gaseous ions. Triangle LEF H circle, kJ/mol
When is there a more exothermic lattice energy
When the overall force of attraction between the ions is stronger: if charges on ions are large and ionic radii small
What are Born-Haber cycles
Thermochemical cycles for calculating lattice energies and for investigating stability and bonding in ionic compounds
What is the first electron affinity of an element
The energy change when each atom in one mole of gaseous atoms gains one electron to form one mole of gaseous ions with a single negative charge, exothermic as 1- ion more stable than the atom
Why is second electron affinity endo
As there is repulsion from the already negative ion which must be overcome
What is enthalpy of formation
Enthalpy change when one mole of a substance is formed from its constituent elements with all elements in their standard states
What is hydration enthalpy
Enthalpy change when one mole of gaseous ions become hydrated (dissolved in water)
What is enthalpy of solution
Enthalpy change when one mole of an ionic solid dissolves in an amount of water large enough so that the dissolved ions are well separated and do not interact with each other
What is bond dissociation enthalpy and how to represent
Triangle dis H circle. Enthalpy change when one mole of covalent bonds is broken in the gaseous state eg I2—> 2I
What is enthalpy of vaporisation
Enthalpy change when one mole of a liquid is turned into a gas
What is enthalpy of fusion
Enthalpy change when one mole of a solid is turned into a liquid
When is lattice energy more exothermic
-charges on the ions are large
-ionic radii are small=ions can get closer to each other
Difference between lattice energy of an ionic compound and its standard enthalpy change of formation
-lattice energy is formation of one mole of a compound from its free gaseous ions whereas standard enthalpy change of formation is elements in their standard states under standard conditions
Why is first IE more exo than second, but all endo
Second lost from already positive ion and is closer to nucleus with one more proton than electron so outer electron more firmly attracted to nucleus and nuclear charge shared over fewer electrons
Why is first IE endothermic
Energy needed to overcome force of electrostatic attraction between outer electron and nucleus
Why is first electron affinity exothermic
Electron being gained experiences attraction to nucleus
