Solubility Prac
Introduction: Solubility is when a particular substance can dissolve in water. The solute is the
substance that dissolves in the solvent, (the solvent is usually of a larger amount) to form a solution
which is two substances mixed together. When a substance, it is not soluble, when mixed with
water, it will produce a precipitate which is a solid.
The following table shows the solubility rules:
Negative ions
(anions)
Positive ions
(cations)
Acetate, CH3COO–
All
All
Li+,
Cl–
Solubility of
compounds
Soluble
Na+,
K+,
Soluble
Chloride,
Bromide, Br–
Iodide, I–
All others
Soluble
Hydroxide, OH–
Li+, Na+, K+, Rb+, NH4+, Sr2+, Ba2+
Soluble
All others
Low solubility
Nitrate,
PO43–
Hg2+,
NH4+
Ag+,
NO3–
Pb2+,
Rb+,
Cu+
Low solubility
All
Soluble
Phosphate,
Carbonate, CO32–
Li+,
Na+,
K+,
Rb+,
NH4+
All others
Low solubility
Sulfate, SO42–
Ca2+, Sr2+, Ba2+, Pb2+
Low solubility
Soluble
All others
Sulfide,
S2–
Li+,
Na+,
K+,
Soluble
Rb+,
NH4+,
Be2+,
Mg2+,
Ca2+,
Sr2+,
Soluble
Ba2+
All others
Low solubility
Aim: To predict, then test to determine which of the chosen ionic compounds are soluble in water.
Materials:




Lots of test tubes
Test tube racks
Water
These ionic substances:
Aluminium nitrate, Aluminium sulphate, Ammonium carbonate, Ammonium
chloride, Ammonium sulphate, Barium chloride, Barium nitrate, Barium sulphate,
Calcium carbonate, Calcium chloride, Calcium hydroxide, Calcium sulphate, Cobalt
chloride, Copper II carbonate, Copper II oxide, Copper II sulphate, Iron II chloride,
Iron III chloride, Iron III oxide, Lead chloride, Lead nitrate, Lithium chloride,
Magnesium hydroxide, Magnesium nitrate, Magnesium oxide, Magnesium sulphate,
Nickel sulphate, Potassium carbonate, Potassium chloride, Potassium dichromate,
Potassium hydroxide, Potassium iodide, Potassium sulphate, Silver nitrate, Sodium
carbonate, Sodium chloride, Sodium hydroxide, Sodium nitrate, Sodium sulphate,
Strontium chloride.
Method:



Fill each test tube about a quarter with water
Take a small spoonful of each compound and put it in each test tube
Give the test tubes a shake and record their solubility
Results:
SUBSTANCE
PREDICTION
SOLUBLE/INSOLUBLE
Aluminium nitrate
Soluble
Soluble
Aluminium sulphate
Soluble
Soluble
Ammonium carbonate
Insoluble
Soluble?
Ammonium chloride
Soluble
Soluble
Ammonium sulphate
Soluble
Soluble
Barium chloride
Soluble
Soluble
Barium nitrate
Soluble
Soluble
Seems soluble, still solid in the
bottom, could have put too
much in but apparently
insoluble.
Water is murky but insoluble
Insoluble
Barium sulphate
Calcium carbonate
Insoluble
Calcium chloride
Soluble
Soluble
Calcium hydroxide
Insoluble
Soluble?
Calcium sulphate
Insoluble
Insoluble
Cobalt chloride
Soluble
Soluble
Copper II carbonate
Insoluble
Soluble?
Copper II oxide
Insoluble
Copper II sulphate
Soluble
Soluble
Iron II chloride
Soluble
Insoluble?
Iron III chloride
Soluble
Soluble
Iron III oxide
Soluble
Lead chloride
Insoluble
Insoluble
Lead nitrate
Soluble
Soluble
Lithium chloride
SUBSTANCE
Soluble
Low solubility
SOLUBLE/INSOLUBLE
Magnesium chloride
Soluble
Soluble
Magnesium hydroxide
Insoluble
Soluble?
Magnesium nitrate
Soluble
Soluble
PREDICTION
Magnesium oxide
Insoluble
Magnesium sulphate
Soluble
Soluble
Nickel sulphate
Soluble
Soluble
Potassium carbonate
Soluble
Soluble
Potassium chloride
Soluble
Soluble
Potassium dichromate
Soluble
Soluble
Potassium hydroxide
Soluble
Soluble
Potassium iodide
Soluble
Soluble
Potassium sulphate
Soluble
Soluble
Silver nitrate
Soluble
Soluble
Sodium carbonate
Soluble
Soluble
Sodium chloride
Soluble
Soluble
Sodium hydroxide
Soluble
Soluble
Sodium nitrate
Soluble
Soluble
Sodium sulphate
Soluble
Soluble
Strontium chloride
Soluble
Soluble
Discussion:
1. For the substances Barium sulphate, Calcium carbonate, Calcium sulphate and Lead chloride, it
was predicted that they would be insoluble, which they were. The predictions were made based on
the table of rules. For example, when sulphate is mixed with barium, it is one of the few times
sulphate becomes insoluble.
Iron II chloride on the other hand was predicted soluble, because according to the rules, chloride is
soluble with any iron. But, in the prac it turned out to be insoluble. This could be because of reasons
of inaccuracy such as putting too much of the substance in the test tube or not shaking the test tube
enough, so the substance couldn’t all dissolve.
2. According to the table of rules, Sodium chloride is soluble. This diagram shows how sodium
chloride dissolves in water.
H+
O-
Cl-
H+
H+
H+
O-
Cl-
Cl-
H+
H+
O-
H+
Na+
Na+
Sodium, Na+, is a positive ion
and Chlorine, Cl-, is a
negative ion.
The positive hydrogens of
water, H+, attract and attach to
the negative Chlorine. The
same happens with Sodium and
the oxygen part of water.
O
-
H+
Na+
Hydrogen shells are formed
around the separated
molecules and prevent them
from rejoining and so can no
longer form a solid.
3. The majority of our results matched up to our predictions. The ones that didn’t were: Ammonium
carbonate, Calcium hydroxide, Copper II carbonate and Magnesium hydroxide. They were predicted
insoluble, using the table of rules, but in the prac were soluble. This could once again be because of
inaccuracy, possibly not assessed well enough but it is more difficult for something to dissolve in
something than to not – saying that, if something’s soluble it’s usually soluble, it is hard to get that
wrong, but if something seems insoluble, there’s usually something you can do to make the
substance dissolve better.
Conclusion: We have now learnt to make accurate predictions of the solubility of a substance, using
the table of solubility rules. Unpredicted outcomes have occurred and may not be because of wrong
predictions. Inaccurate testing may have been the reason.