thermodynamics Flashcards
what is lattice enthalpy of formation
enthalpy change when one mole of a solid is formed from it constituent ions in the gas phase always -ve exothermic
what is lattice enthalpy of dissociation
enthalpy change when one mole of a solid is broken up into its constituent ions in the gas phase always +ve endothermic
how do we compare enthalpies
more or less -ve/+ve
the more exothermic a lattice enthalpy of formation is the ___ the ionic bonds are in the giant ionic lattice
stronger
smaller the ion the ____ the bond
stronger
what is enthalpy of solution
energy change when 1 mole of ionic solid is dissolved in an amount of water large enough so that all the dissolved ions are well seperate
what is enthalpy of hydration
energy change when one mole of gaseous ions become hydrated
what is electron affinity
enthalpy change when a mole of gaseous atom gains an electron to form a mole of gaseous ions
what is enthalpy of atomisation
enthalpy change when one mole of gaseous atoms is produced from an element in its standard state
what is bond dissociation enthalpy
enthalpy change when one mole of bonds is broken in the gas phase
what is enthalpy of vaporisation
enthalpy change when one mole of a liquid is turned into gas
what is enthalpy of fusion
enthalpy change when one mole of solid is turned into a liquid
what is the perfect ionic model
it suggest that all ions are perfectly spherical and the charge is found in the centre
more covalent character the ___ the ionic bond
stronger
larger anions bonded to cations tend to have ___ covalent character
why ???
more
as the cation distorts the electron density of the larger anion
what is entropy
measurement of how disordered a system is
why does a system tend towards more disorder
to increase in energy
the entropy is zero at what temperature
why ???
absolute zero as the particles do not move and so have no disorder
what happens to disorder and entropy as temp increases
why ???
disorder increases as particles vibrate more so there is more disorder so the entropy is higher
how to calculate standard entropy change
(sum of products) - (sum of reactants)
