5.3 Specific types of equilibria Flashcards
solubility rules, molar solubility and ion product, ATSI use to remove toxins in cycad fruit
features of structure of ionic compound
(1) form
(2) attraction
(3) bonding
(1) crystalline lattice
(2) electrostatic attraction extends throughout lattice
(3) ionic
features of the structure of water
*is a molecule
(1) bonding
(2) polarity
(1) covalent
(2) polar, bent (due to large electroneg. difference between H and O)
process of dissolution in water
(1+2) attraction
(3) which bonds broken and formed
(1) partially negative oxygen ions in H2O attracts [the cation]
(2) partially positive hydrogen ions in H2O attracts [the anion]
(3) ionic bonds broken; ion-dipole bonds formed
a solute dissolves in a solvent when:
solute-solvent attractive forces overcome solute-solute and solvent-solvent attractive forces
(2) what solubility depends on
(1) energy required to separate lattice ions
(2) energy released during ion hydration
what energy required to separate lattice ions depends on
strength of ionic bonding
(3) what strength of ionic bonding depends on
(1) spatial arrangement of ions in lattice
(2) ion size
(3) ion charges
(3) what strength of ion-dipole bonding depends on
(1) ion size
(2) ion charge
(3) geometry of ions
the more soluble the salt is,
the more energy released compared to energy needed
HSC Q: Describe changes in bonding and entropy when KCl dissolves in water.
(1) define KCl and water
(2) detail the dissolution process
(3) which bonds broken, which formed?
(4) entropy and why
(1) KCl is salt with covalent bonding, water is polar molecule with hydrogen bonding
(2) partially neg. O attracts K+; partially pos. H attracts Cl-;
(3) ionic bonds broken, ion-dipole bonds formed
(4) salt lattice is broken, ions disperse, thus entropy increases
ΔH, ΔS in separating solvent molecules
endothermic, positive entropy
ΔH, ΔS in solute dissolution
endothermic, positive entropy
ΔH, ΔS in ion hydration
exothermic, negative entropy
list range of solubility
Insoluble < 0.01 mol L-1
Soluble > 0.1 mol L-1
Slightly soluble 0.01 – 0.1 mol L-1
solution is SATURATED when…
solution can dissolve as much solute as will be dissolved at that temperature
solution is UNSATURATED when…
solution that has not reached the limit of solute it will dissolve
solution is SUPERSATURATED when…
solution that contains more dissolved solute than a saturated solution under the same conditions
explain dynamic equilibrium in saturated solutions
equilibrium reached between crystallisation and dissolution (ions break away from crystal into solution and ions in solution precipitate out to solid at equal rates)
solubility of most solids as temperature increases:
increases
solubility of all gases as temperature increases:
decreases
what is a precipitate
formed solid in a solution
solubility product expression
Ksp = [S] [S]
Ksp = equilibrium constant
higher Ksp = more soluble
you can only compare the Ksp of compounds if…
they produce the same number/ratio of ions
what is molar solubility
moles of a salt that will dissolve per litre of water to form a saturated solution
4 steps to find Ksp from molar solubility
(1) balanced equation and equilibrium expression
(2) construct MICE chart
(3) substitute molar values
(4) find Ksp
when ion product < Ksp…
solution is UNSATURATED and NO precipitate forms
when ion product >= Ksp…
solution is SATURATED and precipitate forms
if Q < Ksp, net reaction…
proceeds to the right (unsaturated)
Q = Ksp…
equilibrium, no net change
Q > Ksp, net reaction…
proceeds to the left (super saturated)
common ion effect
adding a salt to a solution that already contains one of the ions reduces the solubility of the salt
toxins present in cycads
cycasin and macrozamin
processes used by ATSI to remove toxins in cycads
cooking, pounding/grinding, and then leaching
