Review Of Simple Acid Base Properties
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2
3
4Review of Simple Acid/Base Properties
Where HA is used to represent any generic Bronsted acid:
+
-
HA (aq) + H
O(l) ========== H
O
(aq) + A
(aq)
2
3
+
-
K
= {[H
O
][A
]/[HA]}
a
3
STRONG ACIDS completely dissociate and therefore have very large values of K
. Examples
a
include HCl, HNO
, HClO
and H
SO
. The conjugate base of strong acids are very weak bases.
3
4
2
4
-
-
-
2-
Therefore, Cl
, NO
, ClO
and SO
are examples of weak bases and are said to be neutral anions.
3
4
4
WEAK ACIDS remain largely undissociated and have relatively small values of K
. Examples
a
include HF, HNO
, HOCl and H
S. The conjugate bases of weak acids are relatively strong bases.
2
2
-
-
-
2-
Therefore, F
, NO
, OCl
and S
are examples of basic anions.
2
STRONG BASES are quantitatively converted into hydroxide ion in aqueous solution.
NaOH, KOH, Ca(OH)
and Mg(OH)
are examples of strong bases, although the latter two have
2
2
limited solubility in water.
WEAK BASES partially react with water to produce hydroxide ions.
+
-
NH
(aq) + H
O(l) ========== NH
(aq) + OH
(aq)
3
2
4
+
-
K
= {[NH
][OH
]/[NH
]}
b
4
3
Water is amphoteric . It can both donate and accept a proton, thus it has the ability to act either as an
acid or a base.
+
-
H
O + H
O ======== H
O
+ OH
2
2
3
+
-
-14
o
K
= [H
O
][OH
]
K
= 1.0 x 10
at 25
C
w
3
w
In general: K
(base) = K
/K
(conjugate acid) and
K
(acid) = K
/ K
(conjugate base)
b
w
a
a
w
b
+
Thus, K
(NH
) = K
/K
(NH
)
a
4
w
b
3
≈ -log [H
+
a
pH = -log
]
H+
In general: pH + pOH = pK
w
o
C; pH = pOH = 7.0
In pure water at 25
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