Untitled - Kelly Walsh High School

226 CHEMISTRY FOR THE UTTERLY CONFUSED
Quick Tip
The same reasoning that was used in dealing with weak acids is also true here:
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[HB ] [OH ]; [HB] Minitially; the numerator can be represented as [OH ] 2 ;
and knowing the initial molarity and Kb of the weak base, the [OH ] can be calculated.
If we know the initial molarity and [OH ], it is possible to calculate the Kb. Different sources may give different values for K b, always use the values given to
you by your instructor or textbook.
The K a and K b of conjugate acid-base pairs are related through the K w expression:
K aK b K w
15-6 Acid-Base Properties
of Salts and Oxides
Some salts have acid-base properties. Ammonium chloride, NH 4Cl, when dissolved
in water will dissociate and the ammonium ion will act as a weak acid,
donating a proton. The strong bases previously listed are all salts that dissolve
yielding the hydroxide ion (which is really the base, not the salt).
Certain oxides can have acid or basic properties. Many oxides of metals that
have a 1 or 2 charge are basic oxides because they will react with water to
form a basic solution:
Na 2O(s) H 2O(l) l 2 NaOH(aq)
Many nonmetal oxides are acidic oxides because they react with water to form
an acidic solution:
CO 2(g) H 2O(l) l H 2CO 3(aq)
Another salt-like group of compounds that have acid-base properties is the
hydrides of the alkali metals and calcium, strontium, and barium. These
hydrides will react with water to form the hydroxide ion and hydrogen gas:
KH(s) H 2O(l) l KOH(aq) H 2(g)