acid-brohhhggdjjdjdkkddkdkdkkddkdknsted.ppt

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2. Historical views on acidsHistorical views on acids
•The more recent Bronsted-Lowry concept is
that acids are H
+
(proton) donors and bases are
proton acceptors
Ionization
ClH
+
H Cl+
•Oxygen (e.g. H
2
SO
4
) was originally thought to cause
acidic properties. Later, Hydrogen was implicated,
but it was still not clear why CH
4
was neutral.
•Arrhenius made the revolutionary suggestion that
some solutions contain ions & that acids produce H
+

ions in solution.

3. The Bronsted-Lowry conceptThe Bronsted-Lowry concept
•In this idea, the ionization of an acid by water
is just one example of an acid-base reaction.
•Acids and bases are identified based on
whether they donate or accept H
+
.
•“Conjugate” acids and bases are found on the
products side of the equation. A conjugate base
is the same as the starting acid minus H
+
.
+ClH
H
H
O
+
H
H
HO Cl+
acid baseconjugate acidconjugate base
conjugate acid-base pairs

4. Practice problemsPractice problems
Identify the acid, base, conjugate acid,
conjugate base, and conjugate acid-base pairs:
acid base conjugate acidconjugate base
HC
2H
3O
2(aq) + H
2O(l)  C
2H
3O
2
–
(aq) + H
3O
+
(aq)
conjugate acid-base pairs
acidbase conjugate acidconjugate base
OH
–
(aq) + HCO
3
–
(aq)  CO
3
2–
(aq) + H
2
O(l)
conjugate acid-base pairs

5. Amphiprotic
•Sometimes a molecule can donate a proton (act as
an acid) and sometimes it can accept a proton (act
as a base).
•Molecules that have this ability to act as both an
acid and a base are called amphoteric or
amphiprotic.
•Water is the most common example of an
amphoteric substance.

6. Practice
For each of the following reactions identify any Bronsted-Lowry
acids and bases.
•HNO
3 + H
2O  H
3O
+
+ NO
3
-
•HNO
3 + NH
3  NH
4
+
+ NO
3
-
•S
2-
+ H
2O  HS
-
+ OH
-
•HS
-
+ OH
-
 S
2-
+ H-OH
•HS
-
+ HCl  H
2
S + Cl
-
Are any of the substances above amphoteric?
•Reference: pg. 488-491
•Try questions 1,2 on page 492