Oceans - Enthalpies of Solution Flashcards
how are ionic solids held together?
electrostatic attraction between anions and cations
what happens to the arrangement of an ionic compound when dissolved in water?
the cations and anions are seperated by water molecules, so the cations and anions now act independently of each other
how do cations interact with water when dissolved?
the cations attract the 𝛿 negative oxygens in water, forming a solvation shell
how to anions interact with water when dissolved?
attracting the 𝛿 positive hydrogens in water, forming a solvation shell
what is a solvation shell?
a molecule that is surrounded by water molecules
why won’t all ionic compounds dissolve in water?
not enough energy in the water to seperate the anions and cations
what is the process of dissolving an ionic compound?
seperation from lattice
hydration of ions
what is the seperation from lattice?
the process of isolating ions from an ionic lattice during dissolving of ionic compounds
what is lattice enthalpy?
the enthalpy change when one mole of solid is formed by seperated ions come together
is lattice enthalpy endothermic or exothermic?
endothermic
what state are ions in after the lattice seperation but before hydration?
gaseous
what is the symbol for lattice enthalpy?
ΔHlattice
what happens to an ion when it is hydrated?
when they are bound to water molecules in ion-diplole interactions
what effect does charge density have on hydration?
the higher the charge density of an ion, the more hydrated it will be
what happens when bonds form between ions and water molecules?
energy is released
what can the energy released from hydration be used for?
seperating other ions from the lattice
what other factor requires energy that affects the solubility of ionic compounds?
the hydrogen bonds between water molecules need to be broken in order for the ionic compound to dissolve
what is the enthalpy of hydration?
the enthalpy change for the formation of a solution of ions from one mole of gaseous ions
how can the strength of attraction between ions and water molecules be measured?
the enthalpy of hydration
what is the symbol for the enthalpy of hydration?
ΔHhyd
is the enthalpy of hydration exothermic or endothermic?
exothermic
what is the enthalpy of solvation and when is it used?
the same as enthalpy of hydration but not specific to water
used when water is not the solvent
what is the symbol for the enthalpy of solvation?
ΔHsolv
what is the enthalpy change of solution?
the difference between enthalpy of hydration and the lattice enthalpy
what is the equation for the enthalpy change of solution?
ΔHsol = ΔHhyd(anion) + ΔHhyd(cation) - ΔHlattice
draw a diagram for a negative enthalpy of solution of an ionic compound
draw a diagram for a positive enthalpy of solution for an ionic compound
what will happen to ionic compounds with a negative enthalpy of solution?
they will dissolve because the process is energetically favourable
what will happen to ionic compounds with a positive enthalpy of solution?
they will not dissolve as the process is energetically unfavourable
what are the exceptions to the rule of compounds with positive solution enthalpies not dissolving?
situations where the entropy increase is favourable
why won’t ionic solids dissolve in non-polar solvents?
the solvation enthalpy is too small
