Lattice Energy Flashcards
Define first ionisation energy.
Energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of unipositive ions.
Define electron affinity.
Energy change when one mole of gaseous atoms gains one mole of electrons to form one mole of negative ions.
Define enthalpy of formation.
When one mole of a substance is formed from its elements in their standard stages under standard conditions.
Define enthalpy of combustion.
When one mole of a substance is burned in excess oxygen under standard conditions.
Define enthalpy of atomisation.
When one mole of gaseous atoms is formed from an element in its standard state.
Define enthalpy of neutralisation.
When one mole of water is produced by the neutralisation of an acid by excess base under standard conditions.
Define lattice energy.
The exothermic energy change when one mole of solid crystal is formed from ions in the gaseous state.
How does ionic radius affect lattice energy?
As ionic radius decreases, lattice energy becomes more exothermic.
Explain the trend in thermal stability of carbonates in group 2.
More stable down the group.
Size of cations increases.
Carbonate ions are less polarised.
Explain why dissolving of magnesium surface is exothermic.
Breaking lattice is endothermic.
Hydration of ions is exothermic.
Therefore dissolving of MgSO4 is exothermic.
Enthalpy of hydration is greater than lattice energy.
Predict effect on Ssystem if hydrated barium chloride forms instead of anhydrous barium chloride.
Ssys of hydrated BaCl2 will be greater — more complex.
Ssys will increase.
8 water molecules are formed instead of 10.
Ssys will decrease.
Can’t predict overall change on Stotal — we dont know extent of each change.
