Thermodynamics Flashcards
(20 cards)
enthalpy of formation
enthalpy change when one mole of a compound is formed from its constituent elements under standard conditions
prods/reactants in standard state
enthalpy of lattice formation
Enthalpy change when 1 mol of solid ionic compound is formed from its gaseous ions
electron affinity
enthalpy change when one mol of gaseous atoms converted to one mol of gaseous ions
enthalpy of hydration
enthalpy change when 1 mol of a gaseous ion forms aqueous ions
lattice enthalpy of dissociation
enthalpy change to break up 1 mol of solid ionic compound into constituent gaseous ions
enthalpy of atomisation
enthalpy change when 1 mol of gaseous atoms produced from element in standard state
perfect ionic model
ions are perfect spheres with only electrostatic forces between ions
two properties of ions that influence the value of a lattice enthalpy
distance between ions
ionic charge
enthalpy is greater than expected/more exothermic
covalent character strengthens the lattice interactions and BH cycle allows for covalent interaction
enthalpy is equal to perfect ionic model
compound is perfectly ionic / no covalent character
value for the enthalpy of hydration for the chloride ion is more negative than the bromide ion
chloride ions are smaller than bromide ions
stronger forces of attraction between cl ions and water
chloride ions attract the δ+ on H of water
lattice dissociation enthalpy of magnesium chloride is greater than that of calcium chloride
magnesium ion has a smaller radius
attraction between ions stronger
lattice dissociation enthalpy of magnesium oxide is greater than that of magnesium chloride
oxide ion has a greater charge than chloride ion
attracts the magnesium ion more strongly
magnesium ions attract water
water is polar
+ve ion attracts negative O on water molecule
endothermic
energy supplied to break bonds
fluorine electronegativity > chlorine
fluorine smaller
electrons attracted more strongly to the nucleus
entropy with positive value
more disorder
enthalpy change of formation
sum of everything
enthalpy of lattice formation
enthalpy of formation - (sum of everything)
enthalpy of lattice formation NaF vs NaCl
NaCl less negative
Cl- bigger
weaker attraction to Na+
