Objectives - To study the chemical properties
of the three cations: Pb2+, Hg22+ and Ag+ and then use these properties to separate
and identify which of these cations are present in an unknown solution.
There are about 25 cations, which are commonly examined. From this
group only three (Pb2+, Hg22+
and Ag+) form water insoluble chlorides. This chemical property
is used as a basis for separating them from other cations. Differences in the
chemical properties of the individual ions are then used as a basis for separation
If a solution contains several cations, it is possible to select
a reagent that will form an insoluble product with one of the cations and not
with the others. A technique known as centrifuging separates
the precipitated cations (i.e. the solid) from the remaining ions in the solution.
The solution, or known as the supernate, is then
poured off and the analysis continues for the remaining cations in the solution.
Click on the following links and study the net ionic equations
for the reactions you will observe: