What does it mean for a compound to be
soluble in water?
–The substance will dissociate into ions.
Example 1: AB (s) ( + water) ® AB (aq) ® A+ (aq) + B-(aq)
AB (aq) represents an aqueous solution of AB
containing hydrated ions, A+ (aq) and B-(aq).
Each formula unit in the above example
produces one each of the ions. Or, a mole
of the formula unit produces a mole each of the cations and anions, a total of 2 moles of aqueous ions.
Example 2: AB2 (s) ( + water) ® AB2 (aq) ® A+ (aq) + 2 B-(aq)
In example 2, 1 mole of the compound produces 1 mol of hydrated
cations and 2 moles of hydrated anions, a total of 3 moles of
aqueous ions.