When sodium chloride dissolves in water, the ions separate from each other into positive sodium ions and negative chloride ions. This dissolving process can be represented by the equation NaCl(s) → Na+(aq) + Cl-(aq). The solubility of compounds is based on rules regarding which ions combine to form soluble or insoluble compounds. Compounds that do not dissolve in water and remain as a solid are considered precipitates, and chemical reactions where precipitates form are called precipitation reactions.

2. When table salt (Sodium Chloride) is
dissolved in water to form an aqueous
solution the ions no longer bond together,
they separate into an array of positive and
negative ions.
The dissolving of Sodium Chloride into
water can be represented by the equation:
NaCl (s) → Na+ (aq) + Cl-(aq)

3. The solubility of compounds are based on a number of
rules . At this stage it is important to be aware and
exposed to these:
 All compounds containing NA+, NH4
+, K+ or NO-
3 will
dissolve in water (SOLUBLE)
 Compounds containing Cl-, Br- and I- ions are SOLUBLE
except if they have (Ag+, Pb2+ or Hg2+ ions)
 Compounds containing SO4
-2 are SOLUBLE except (Ba+2,
Pb+2 and Ca2+)
 Compounds containing CO3
-2 and PO4
-3 are INSOLUBLE
except with Na+, NH4
+ or K+
 Compounds containing OH- are INSOLUBLE unless with
Na+, NH4
+ or K+

4. Compounds which are unable to
dissolve in liquid solutions –
a solid forms.
This is a precipitate.
Chemical reactions in
which precipitates
form are known as
precipitation reactions

5. Science Quest page 203
Will it precipitate?
Solution Observations
Sodium Chloride
Silver Nitrate
Cobalt Chloride
Sodium Hydroxide
Potassium Iodide