What do soluble compounds contain?
Alkali metal ions (Li+, Na+, K+,
Rb+, Cs+), the ammonium ion (NH4
+), Nitrates (NO
3
-), bicarbonates (HCO3
-), chlorates (ClO3
-), Halides (Cl-, Br-, I-)
and Sulfates (SO4
2-)
What are the insoluble exceptions to the soluble compounds?
Halides of Ag+, Hg2
2+, and Pb2+
Sulfates of Ag+, Ca2+, Sr2+, Ba2+,Hg2
2+, and Pb2+
What are the insoluble compounds?
Carbonates (CO3
2-), phosphates (PO4
3-), chromates (CrO4
2-), sulfides (S2-) and hydroxides (OH-)
What are the soluble exceptions to the insoluble compounds?
Compounds containing alkali metal ions and the ammonium ion.
Compounds containing alkali metal ions and the Ba2+ ion.
What are the acid-base properties of salt solutions?
The acidity (basicity) of salt solutions depends on the acid-base
properties of their ions
Acidic cations � act as weak acids in water
The cations (conjugate acids) of weak bases (NH4
+, CH3NH2
+, �) ? act as weak acids Small, highly charged
metal cations (Al3
+, Fe3
+, Cr3
+, Cu2
+, �) ? act as weak acids
Neutral cations � do not influence the pH �
The cations of strong bases (Group I, Ca2
+, Sr2
+, Ba2
+) and metal cations with +1 charge (Ag+,
Cu+, �) are extremely weak acids (weaker than
H2O) ? do not influence the pH
What are the properties of acidic cations?
Acidic cations � act as weak acids in water
The cations (conjugate acids) of weak bases (NH4
+, CH3NH2
+, �) ? act as weak acids Small, highly charged
metal cations (Al3
+, Fe3
+, Cr3
+, Cu2
+, �) ? act as weak acids
What are the properties of neutral cations?
Neutral cations � do not influence the pH �
The cations of strong bases (Group I, Ca2
+, Sr2
+, Ba2
+) and metal cations with +1 charge (Ag+,
Cu+, �) are extremely weak acids (weaker than
H2O) ? do not influence the pH
What are the properties of basic anions?
Basic anions � act as weak bases in water
The anions (conjugate bases) of weak acids (F-,
CN-, S2-, PO4
3- �) ? act as weak bases
What are the properties of neutral anions?
Neutral anions � do not influence the pH
The anions (conjugate bases) of strong acids (Cl-,
Br-, I-, NO3
-, ClO4
- �) are extremely weak bases (weaker than
H2O) ? do not influence the pH
What are the properties of amphoteric anions of polyprotic acids?
Amphoteric anions of polyprotic acids � can act as weak acids or
bases in water
Anions with ionizable protons (H2PO4
-, HPO4
2-, HS-, HSO3
-, HSO4
-) ? act as either weak acids or weak bases depending on
the relative values of their Ka and Kb
constants)
What are the acid-base properties of salt solutions for neutral
cations and neutral anions?
Salts of neutral cations and neutral anions yield neutral solutions
Ex: NaCl(s) ? Na+ + Cl- (neutral
solution)
Na+ ? neutral cation (cation of a strong base, NaOH)
Cl- ? neutral anion (anion of a strong acid, HCl)
What are the acid-base properties of salt solutions for acidic
cations and neutral anions?
Salts of acidic cations and neutral anions yield acidic solutions
Example: NH4Cl(s) ? NH4
+ + Cl- (acidic solution)
NH4
+ ? acidic cation (cation of a weak base, NH3)
Cl-? neutral anion (anion of a strong acid, HCl) NH4
++ H2O ? H3O++NH3
Example: FeCl3(s) ? Fe3++
3Cl- (acidic solution)
Fe3+ ? acidic cation (highly charged, small cation)
Cl- ? neutral anion (anion of a strong acid, HCl)
Fe(H2O)6
3+ + H2O ? H3O+ + Fe(H2O)5OH2+
What are the acid-base properties of salt solutions for neutral
cations and basic anions?
Salts of neutral cations and basic anions yield basic solutions
Example: Na2S(s) ? 2Na+ + S2-
(basic solution)
Na+ ? neutral cation (cation of a strong base, NaOH)
S2- ? basic anion (anion of a weak acid, H2S)
S2- + H2O ? HS- + OH-
Example: KF(s) ? K+ + F- (basic
solution)
K+ ? neutral cation F- ? basic anion
What is an electrolyte?
An electrolyte is a substance that contains free ions and behaves as
an electrically conductive medium.
What is an ionic solution?
Because electrolytes generally consist of ions in solution, they are
also known as ionic solutions
What is a strong electrolyte? Is it a good conductor?
A strong electrolyte is one where many ions are present in the
solution and yes it's a strong conductor
What is a weak electrolyte? Is it a strong conductor?
A weak electrolyte is one where few ions are present and no it's a
weak conductor
...
Non-electrolytes do not conduct electricity at all.
...
Conductivity in aqueous solutions, is a measure of
the ability of water to conduct an electric current. The more
ions there are in the solution, the higher its
conductivity. Also the more ions there are in solution, the stronger
the electrolyte.
...
The concentration of ions in solution. The higher the
concentration of ions in solution, the higher its conductivity will
be. The type of substance that dissolves in water. Whether a
material is a strong electrolyte (e.g. potassium nitrate, KNO3), a
weak electrolyte (e.g. acetic acid, CH3COOH) or a non-electrolyte
(e.g. sugar, alcohol, oil) will affect the conductivity of water
because the concentration of ions in solution will be different in
each case. Strong electrolytes form ions easily, weak electrolytes
do not form ions easily and non-electrolytes do not form ions in
solution.
...
The warmer the solution, the higher the solubility of the material
being dissolved and therefore the higher the conductivity as well
Designate the following properties as either chemical or physical:
When conducting a flame test, you see a bright purple color.
Chemical
Designate the following properties as either chemical or physical:
Measuring the conductivity of a solution and seeing a high reading.
Physical � conductivity just measures the amount a compound dissolves
in water, which is not a chemical change in the compound.
Designate the following properties as either chemical or physical:
Observing a precipitate when silver nitrate is added.
Chemical � the addition of silver nitrate to a solution results in a chemical
reaction between two compounds, producing a new compound that is
insoluble in water.
What is occurring at the molecular level during a flame test that
causes different colors to appear?
The solution contains ions of the chemical compound being tested.
When these ions are put into the flame, the energy from the flame
excites the electrons of these atoms. The release of energy as the
electrons go from excited state back to ground state produce a photon
of energy. For certain atoms, such as group 1 and group 2 metals,
these photons have wavelength(s) in the visible spectrum. The
continual excitation and de-excitation produces a particular color.
When is evaporation an appropriate technique to use in lab? How do
you properly and safely perform this technique?
Evaporation should be used when you want to isolate a product that is
soluble and in solution. (NOTE: Evaporation will not isolate a product
if there is another soluble salt in solution � both salts will remain
after evaporation).
In order to safely perform the technique, the Bunsen burner or hot
plate should be set so that the solution boils but not too vigorously.
A watch glass should be placed on top of the container to keep the
salt from popping out of the container.