Precipitation chem Flashcards
define saturated
max amount of solute dissolved in presence of XS solute
define the solubility of a substance
= max amount that will dissolve in a given volume of solvent
solubility depends on
chemical nature of the solute and solvent the temperature (generally higher solubility at higher temp)
insoluble ionic solids generally have…
highly charged anions and cations, so that the attractive forces between anion/cations are greater than with water.
Solubility rules - the soluble
ammonium, G1, nitrate and ethanoate salts
sulfates EXCEPT Ca, Sr, Ba, Pb
halide salts EXCEPT Ag+ and Pb2+
generally, anion charges -1 tend to be soluble
solubility rules - the insoluble
OH- and O2-, except for Na+ and K+
Sulfides (S2-), Carbonates, Phosphates EXCEPT Na+, K+ and NH4+
in general, anion charge -2 or -3 insoluble.
ions exist in solution as _____
hydrates
what are hydrates
complexes of ions w/ H2O
written M+(aq) or X-(aq)
ion surrounded by H2O molecules, orientation depends on charge on ion.
H end is ∂+, O end is ∂-
Cu2+ colour in solution
blue
Fe2+ colour in sln
light green
Ag+ in solution and ppt
cls sln, brown ppt Ag2O
Fe3+ in sln and ppt
pale yellow sln
Fe(OH)3 red-orange ppt
Mg(OH)2 solubility in XS NaOH and NH3
not soluble in either
Ba(OH)2 solubility in XS NaOH and NH3
not soluble in either
ions that form cls sln and white ppt w/ OH-
Mg2+, Ba2+, Pb2+, Al3+, Zn2+
Pb(OH)2 solubility in XS NaOH and NH3
soluble in XS NaOH
NOT soluble in XS NH3
Al(OH)3 solubility in XS NaOH and NH3
soluble in XS NaOH
NOT soluble in XS NH3
Zn(OH)2 solubility in XS NaOH and NH3
soluble in both
Add H2SO4 to find the difference between these two pairs of substances
Mg(OH)2 and Ba(OH)2
Both are not soluble in NaOH/NH3
Pb(OH)2 and Al(OH)3
Both are soluble in NaOH but not NH3
Ba and Pb form insoluble sulphates
testing for CO3^2- and OH-
litmus
red–>blue in CO3^2- and OH-
add aq acid - carbonate reacts, forming H2CO3 which decomposes to H2 and CO2 (bubbles)
testing for SO4^2-
add acidified BaCl
white ppt, BaSO4
testing for Cl-, Br-, I-
add aq AgNO3
insoluble ppt formed
AgCl = white
AgI = cream/yellow
differentiate Cl- and I- ions
first add aq AgNO3 to form AgCl and AgI
AgCl dissolves on addition of aq NH3 –> Ag(NH3)2^+
AgI remains undissolved
define ligand
the groups in a complex ion that are bonded to the central ion
cation central, a long e- pair on ligand used for bonding
for H2O, nonbonding pair on O
examples of possible ligands
molecules: H2O, NH3
anions: OH-, Cl-, SCN-
what affects the numbers of attached ligands
the size and charge of the central ion
2, 4 and 6 are common
formation of a complex ion results in
the precipitate dissolving
compound containing complex ion is soluble in water
what ions have coloured ppts or complex ions?
transition metals
