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Acids and Bases: Conjugate
Related Topics
Wize University Chemistry Textbook > Acids and Bases
Conjugate Acid-Base Pairs
2 Activities
Wize University Chemistry Textbook > Acids and Bases
Acid Equations (Ka, pKa)
3 Activities
Using the data in the table, which of the conjugate bases below is the strongest base?
A
c
i
d
K
a
H
O
A
c
1.8
×
10
−
5
H
C
H
O
2
1.8
×
10
−
4
H
C
l
O
3.0
×
10
−
8
H
F
6.8
×
10
−
4
\def\arraystretch{1.5} \begin{array}{c} \hline \rm Acid &&&K_a\\ \hline HOAc&&&1.8 \times 10^{-5}\\ HCHO_2&&&1.8 \times 10^{-4}\\ HClO &&& 3.0 \times 10^{-8}\\ HF &&& 6.8 \times 10^{-4}\\ \hline \end{array}
Acid
H
O
A
c
H
C
H
O
2
H
C
l
O
H
F
K
a
1.8
×
1
0
−
5
1.8
×
1
0
−
4
3.0
×
1
0
−
8
6.8
×
1
0
−
4
F
−
F^-
F
−
C
l
O
−
ClO^-
C
l
O
−
C
H
O
2
−
CHO_2^-
C
H
O
2
−
O
A
c
−
OAc^-
O
A
c
−
O
A
c
−
a
n
d
C
H
O
2
−
OAc^-\ and\ CHO_2^-
O
A
c
−
an
d
C
H
O
2
−
I don't know
Check Submission
More Conjugate Acid-Base Pairs Questions:
In a reaction, which of the following could be conjugate acid-base pairs?
Weak Acids and Bases
Will HCO
3
-
act as an acid or as a base?
Weak Acids and Bases
Sulfurous acid (H2SO
3
) is a diprotic weak acid (p
K
a1
= 1.85, p
K
a2
= 7.20). Bisulfite (HSO
3
-
) is the conjugate base of sulfurous acid and is an amphoteric species (can act as an acid or a base). Will HSO
3
-
act as an acid or as a base?
In the reaction
H
S
O
4
−
(
a
q
)
+
O
H
−
(
a
q
)
⇌
S
O
4
2
−
(
a
q
)
+
H
2
O
(
l
)
HSO_4^-\left(aq\right)\ +\ OH^-\left(aq\right)\ ⇌\ SO_4^{2-}\left(aq\right)\ +\ H_2O\ \left(l\right)
H
S
O
4
−
(
a
q
)
+
O
H
−
(
a
q
)
⇌
S
O
4
2
−
(
a
q
)
+
H
2
O
(
l
)
the conjugate acid-base pairs are
Select which of the following WOULD NOT be a conjugate acid/base pair.
Consider the weak bases below and their K
b
values:
C
6
H
7
O K
b
= 1.3 x 10
-10
C
2
H
5
NH
2
K
b
= 5.6 x 10
-4
Consider the following reaction:
N
H
4
+
+
O
H
−
⇌
H
2
O
+
N
H
3
NH^{4+}+OH^-\rightleftharpoons H_2O+NH_3
N
H
4
+
+
O
H
−
⇌
H
2
O
+
N
H
3
Choose the INCORRECT statement
Using the incomplete reaction below, choose the completed equilibrium which indicates the correct association of conjugate acid base pairs.
H
C
l
+
H
2
O
⇌
\rm HCl\quad+\quad H_2O\quad \xrightleftharpoons{\hspace{1.5cm}}
HCl
+
H
2
O
**#1 and #2 designate the two sets of conjugate acid base pairs present in each equilibrium**
Consider the weak bases below and their K
b
values:
C
6
H
7
O
K
b
=
1.3
×
10
−
10
C_6H_7O \hspace{48pt}K_b=1.3 \times 10^{-10}
C
6
H
7
O
K
b
=
1.3
×
1
0
−
10
C
2
H
5
N
H
2
K
b
=
5.6
×
10
−
4
C_2H_5NH_2 \hspace{30pt}K_b=5.6 \times 10^{-4}
C
2
H
5
N
H
2
K
b
=
5.6
×
1
0
−
4
In the reaction
H
S
O
4
(
a
q
)
−
+
O
H
(
a
q
)
−
⇌
S
O
4
(
a
q
)
2
−
+
H
2
O
(
l
)
HSO^-_{4(aq)}+OH^-_{(aq)} \rightleftharpoons SO^{2-}_{4(aq)}+H_2O_{(l)}
H
S
O
4
(
a
q
)
−
+
O
H
(
a
q
)
−
⇌
S
O
4
(
a
q
)
2
−
+
H
2
O
(
l
)
the conjugate acid-base pairs are
To 2L of pure water is added Mg(ClO
4
)
2
. What would the effect on pH be?
Triemethylamine (N(CH
3
)
3
) is a base (pKb=4.19) used in a variety of organic reactions. It can also be used as an effective Lewis base due to it's small steric profile.
if a solution of [N(CH
3
)
3
H]
2
[SO
4
]is dissolved in neutral water the pH will be,
A series of solutions are formed with strontium salts of the form SrX
2
where X=F, Cl, Br, I.
Which of the solutions will have the highest pH?
Pure water has a pH of 7.00. 1.1g of MgBr
2
is added to 15L of pure water. The solubility of MgBr
2
in water is approximatly 101.5g/L. What is the pH of the resulting solution?
Using the incomplete reaction below, choose the completed equilibrium which indicates the correct association of conjugate acid base pairs.
H
C
l
+
N
H
3
⇌
\rm HCl\quad+\quad {NH_3}\quad \xrightleftharpoons{\hspace{1.5cm}}
HCl
+
N
H
3
**#1 and #2 designate the two sets of conjugate acid base pairs present in each equilibrium**
Using the incomplete reaction below, choose the completed equilibrium which indicates the correct association of conjugate acid base pairs.
+
C
H
3
C
O
O
H
⇌
H
2
O
+
N
a
+
C
H
3
C
O
O
−
\rm \quad+\quad {CH_3COOH}\quad \xrightleftharpoons{\hspace{1.5cm}}\quad H_2O\quad+\quad Na^+CH_3COO^-
+
C
H
3
COOH
H
2
O
+
N
a
+
C
H
3
CO
O
−
**#1 and #2 designate the two sets of conjugate acid base pairs present in each equilibrium**
Acids and Bases: Conjugate
In each equation, label the acids, bases and conjugate acid-base pairs
N
H
3
+
H
3
P
O
4
↔
N
H
4
+
+
H
2
P
O
4
−
NH_3+H_3PO_4 \leftrightarrow NH^+_4+H_2PO^-_4
N
H
3
+
H
3
P
O
4
↔
N
H
4
+
+
H
2
P
O
4
−
C
H
3
O
−
+
N
H
3
↔
C
H
3
O
H
+
N
H
2
−
CH_3O^-+NH_3 \leftrightarrow CH_3OH+NH^-_2
C
H
3
O
−
+
N
H
3
↔
C
H
3
O
H
+
N
H
2
−
Using the incomplete reaction below, choose the completed equilibrium which indicates the correct association of conjugate acid base pairs.
H
C
l
+
H
2
O
⇌
\rm HCl\quad+\quad H_2O\quad \xrightleftharpoons{\hspace{1.5cm}}
HCl
+
H
2
O
**#1 and #2 designate the two sets of conjugate acid base pairs present in each equilibrium**
Acids and bases: Conjugate identification
In the reaction HSO
4
-
(aq) + OH
-
(aq) ⇌ SO
4
2
-(aq) + H
2
0(l), the conjugate acid-base pairs are:
B is a weak base. Which equilibrium corresponds to the equilibrium constant K
a
for HB
+
?
Acids and Bases: Conjugate Acid-base Pairs
Indicate how many of these combinations are conjugate acid-base pairs.
Select all that apply.
More Acid Equations (Ka, pKa) Questions:
The following reaction occurs in water:
CH
3
OH <----> CH
3
O
-
+ H
+
Once the reaction was allowed to reach equilibrium, 0.5 M of CH
3
OH, 0.3 M of CH
3
O
+
, and 0.3 M of H
+
were found in solution. What are the K
a
and K
b
of this solution?
The following reaction occurs in water:
CH
3
OH <----> CH
3
O
-
+ H
+
Once the reaction was allowed to reach equilibrium, 0.5 M of CH
3
OH, 0.3 M of CH
3
O
+
, and 0.3 M of H
+
were found in solution. What is the K
a
of this solution?
The following reaction occurs in water:
CH
3
OH <----> CH
3
O
-
+ H
+
Once the reaction was allowed to reach equilibrium, 0.5 M of CH
3
OH, 0.3 M of CH
3
O
+
, and 0.3 M of H
+
were found in solution. What is the K
a
of this solution?
The following reaction occurs in water:
CH
3
OH <----> CH
3
O
-
+ H
+
Once the reaction was allowed to reach equilibrium, 0.5 M of CH
3
OH, 0.3 M of CH
3
O
+
, and 0.3 M of H
+
were found in solution. What is the K
a
of this solution?
The following reaction occurs in water:
CH
3
OH <----> CH
3
O
-
+ H
+
Once the reaction was allowed to reach equilibrium, 0.5 M of CH
3
OH, 0.3 M of CH
3
O
+
, and 0.3 M of H
+
were found in solution. What is the K
a
of this solution?
The following reaction occurs in water:
CH
3
OH <----> CH
3
O
-
+ H
+
Once the reaction was allowed to reach equilibrium, 0.5 M of CH
3
OH, 0.3 M of CH
3
O
+
, and 0.3 M of H
+
were found in solution. What is the K
a
of this solution?
The following reaction occurs in water:
CH
3
OH <----> CH
3
O
-
+ H
+
Once the reaction was allowed to reach equilibrium, 0.5 M of CH
3
OH, 0.3 M of CH
3
O
+
, and 0.3 M of H
+
were found in solution. What is the K
a
of this solution?
The following reaction occurs in water:
CH
3
OH <----> CH
3
O
-
+ H
+
Once the reaction was allowed to reach equilibrium, 0.5 M of CH
3
OH, 0.3 M of CH
3
O
+
, and 0.3 M of H
+
were found in solution. What is the K
a
of this solution?
The following reaction occurs in water:
CH
3
OH <----> CH
3
O
-
+ H
+
Once the reaction was allowed to reach equilibrium, 0.5 M of CH
3
OH, 0.3 M of CH
3
O
+
, and 0.3 M of H
+
were found in solution. What is the K
a
of this solution?
The following reaction occurs in water:
CH
3
OH <----> CH
3
O
-
+ H
+
Once the reaction was allowed to reach equilibrium, 0.5 M of CH
3
OH, 0.3 M of CH
3
O
+
, and 0.3 M of H
+
were found in solution. What is the K
a
of this solution?
The following reaction occurs in water:
CH
3
OH <----> CH
3
O
-
+ H
+
Once the reaction was allowed to reach equilibrium, 0.5 M of CH
3
OH, 0.3 M of CH
3
O
+
, and 0.3 M of H
+
were found in solution. What is the K
a
of this solution?
The following reaction occurs in water:
CH
3
OH <----> CH
3
O
-
+ H
+
Once the reaction was allowed to reach equilibrium, 0.5 M of CH
3
OH, 0.3 M of CH
3
O
+
, and 0.3 M of H
+
were found in solution. What is the K
a
of this solution?
The following reaction occurs in water:
CH
3
OH <----> CH
3
O
-
+ H
+
Once the reaction was allowed to reach equilibrium, 0.5 M of CH
3
OH, 0.3 M of CH
3
O
+
, and 0.3 M of H
+
were found in solution. What is the K
a
of this solution?
The following reaction occurs in water:
CH
3
OH <----> CH
3
O
-
+ H
+
Once the reaction was allowed to reach equilibrium, 0.5 M of CH
3
OH, 0.3 M of CH
3
O
+
, and 0.3 M of H
+
were found in solution. What is the K
a
of this solution?
The following reaction occurs in water:
CH
3
OH <----> CH
3
O
-
+ H
+
Once the reaction was allowed to reach equilibrium, 0.5 M of CH
3
OH, 0.3 M of CH
3
O
+
, and 0.3 M of H
+
were found in solution. What is the K
a
of this solution?
The following reaction occurs in water:
CH
3
OH <----> CH
3
O
-
+ H
+
Once the reaction was allowed to reach equilibrium, 0.5 M of CH
3
OH, 0.3 M of CH
3
O
+
, and 0.3 M of H
+
were found in solution. What is the K
a
of this solution?
The following reaction occurs in water:
CH
3
OH <----> CH
3
O
-
+ H
+
Once the reaction was allowed to reach equilibrium, 0.5 M of CH
3
OH, 0.3 M of CH
3
O
+
, and 0.3 M of H
+
were found in solution. What is the K
a
of this solution?
The following reaction occurs in water:
CH
3
OH <----> CH
3
O
-
+ H
+
Once the reaction was allowed to reach equilibrium, 0.5 M of CH
3
OH, 0.3 M of CH
3
O
+
, and 0.3 M of H
+
were found in solution. What is the K
a
of this solution?
The following reaction occurs in water:
CH
3
OH <----> CH
3
O
-
+ H
+
Once the reaction was allowed to reach equilibrium, 0.5 M of CH
3
OH, 0.3 M of CH
3
O
+
, and 0.3 M of H
+
were found in solution. What is the K
a
of this solution?
The following reaction occurs in water:
CH
3
OH <----> CH
3
O
-
+ H
+
Once the reaction was allowed to reach equilibrium, 0.5 M of CH
3
OH, 0.3 M of CH
3
O
+
, and 0.3 M of H
+
were found in solution. What is the K
a
of this solution?
Methyl diethanolamine CH
3
N(C
2
H
4
OH)
2
is a weak base which we will abbreviate as
mdea
. The conjugate acid,
mdeaH
+
, has a pKa = 8.52.
Nitrous acid has a Ka of 7.1 x 10
-5
. What are [H
3
O
+
], [NO
2
-
] andin 0.50 M HNO
2
?
Acids and Bases: Weak Acid Practice
Nitrous acid has a K
a
of 7.1 x 10
-5
. What are [H
3
O
+
] and [NO
2
-
] in 0.50 M HNO
2
?
Nitrous acid has a Ka of 7.1 x 10
-5
. What are [H
3
O
+
], [NO
2
-
] andin 0.50 M HNO
2
?
Acids and Bases: Ka
The following occurs when HCl is placed in water:
HCl <----> H
+
+ Cl
-
The K
a
for this reaction is known to be K
a
= 5.64 once it reaches equilibrium. At equilibrium, 1.35 x 10
-7
M of HCl and 1.2 M of Cl
-
can be found. What is the pH of the solution at equilibrium?
The following reaction occurs in water:
CH
3
OH <----> CH
3
O
-
+ H
+
Once the reaction was allowed to reach equilibrium, 0.5 M of CH
3
OH, 0.3 M of CH
3
O
+
, and 0.3 M of H
+
were found in solution. What is the K
a
of this solution?
The equilibrium constant for the auto-ionization of water at 10 °C is 3.0 x 10
-15
. What is the concentration of H
3
O
+
ions in pure water at this temperature?
What is the pH of a 1.1M solution of nitrous acid (HNO
2
). The K
a
of nitrous acid is 7.2 x 10
-4
Ammonia(NH
3
) is a weak base, K
b
= 1.8 x 10
-5
and benzoic acid (C
6
H
5
CH
2
O
-
) is a weak acid, K
a
= 6.3 x 10
-5
. A solution of ammonium benzoate (NH
4
)(C
6
H
5
CH
2
O
-
) is:
To 4.00 L of water was added 100 mg of HF (6.6 x 10
-4
). What is the pH?
CH
3
COOH is a weak acid with a K
a
of 1.8 x 10
-5
. In what pH range would you most likely an aqueous solution of Na(CH
3
COO).
Acids and Bases: Henderson Hasselbalch
To a solution of acetic acid (
K
a
=
1.8
×
10
−
5
\rm K_a = 1.8 \times 10^{-5}
K
a
=
1.8
×
1
0
−
5
) was added 0.1 mol of
N
a
O
H
\rm NaOH
NaOH
. After the addition of
N
a
O
H
\rm NaOH
NaOH
the volume was 1.4L and the
p
H
\rm pH
pH
was 5.2.
a) This solution a buffer? (True/False)
b) Calculate the number of moles of acetic acid that were originally in solution. Report your answer in moles to three significant figures. Do not include units in the answer field
Calculate the pH of the solution resulting from the addition of 10.0 mL of a 0.10 M NaOH to 50.0 mL of 0.10 M HCN (Ka = 4.9 x 10
-10
) solution
A solution of [CH
3
NH
3
][CH
3
COO] is made in an undergraduate laboratory. Use the information below to predict the acidity of the solution.
CH
3
COOH: K
a
= 1.8 x 10
-5
CH
3
NH
3
+
: K
a
= 2.3 x 10
-11
Strength of Acids and Bases
What is the strongest acid below? What is the weakest acid?
Strongest acid:
Cl
3
CCOOH
Weakest acid:
HCN
Acids and Bases: Acidity
Nitrous acid has a Ka of 7.1 x 10
-5
. What are [H
3
O
+
] and [NO
2
-
] in 0.50 M HNO
2
?
Which of the solutions below would have the HIGHEST pH value?
Methyl diethanolamine CH
3
N(C
2
H
4
OH)
2
is a weak base which we will abbreviate as
mdea
. The conjugate acid,
mdeaH
+
, has a pKa = 8.52.
Practice: Relating [H3O+], [OH-], pH and pOH
Compare two acids and their 1M solution:
A
c
i
d
1
:
K
a
=
1.0
×
10
−
3
A
c
i
d
2
:
K
a
=
1.0
×
10
−
6
\rm Acid\ 1:K_a=1.0\times10^{-3}\qquad Acid\ 2:K_a=1.0\times10^{-6}
Acid
1
:
K
a
=
1.0
×
1
0
−
3
Acid
2
:
K
a
=
1.0
×
1
0
−
6