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Auto-ionization of Water: pH
Related Topics
Wize University Chemistry Textbook > Acids and Bases
Autoionization of Water (Kw)
5 Activities
If the pH of pure water is 6.80 at 37 °C, calculate K
w
pOH and [OH
-
] at this temperature.
If an answer has an exponent (ex. 1.6x10
3
), input it as: 1.6e3
pOH
[OH-] Enter answer with 2 significant digits.
Kw (Enter answer with 2 significant digits)
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More Autoionization of Water (Kw) Questions:
Concentration
A solution of LiOH is made by mixing an unknown amount of LiOH with 1 L of water. The pOH is measured to be 3.65, what is the concentration of LiOH?
MW Li: 7 g/mol
MW O: 16 g/mol
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
Diet cola drinks have a pH of about 3.0, while milk has a pH of about 7.0. How many times greater is the H
3
O
+
concentration in diet cola than in milk?
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?
Acids and Bases: pH
100
m
L
100\ mL
100
m
L
of a
0.5
M
0.5\ M
0.5
M
solution of Hydrochloric acid (
H
C
l
\rm HCl
HCl
) was added to
48
m
L
48\ mL
48
m
L
of a
0.410
M
0.410\ M
0.410
M
solution of sodium benzoate (
C
6
H
5
C
O
O
N
a
\rm C_6H_5COONa
C
6
H
5
COONa
) the conjugate base of benzoic acid (
C
6
H
5
C
O
O
H
\rm C_6H_5COOH
C
6
H
5
COOH
K
a
=
6.6
×
10
−
5
\rm K_a = 6.6 \times 10^{-5}
K
a
=
6.6
×
1
0
−
5
). Calculate the
p
H
\rm pH
pH
of the resulting solution.
An aqueous solution only contains a 0.050 M in a weak base. Which of the following statements would be true about the solution?
Lactic acid, shown below, is added to many beverages, including some sour beers. What is the pH of a 0.050M lactic acid solution in 0.50M hydrochloric acid? (K
a
for lactic acid=1.38x10
-4
)
What is the hydroxide ion (OH
-
) concentration of a solution with a pH of 6.1?
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 (K
a
= 4.9 x 10
-10
) solution
Diet cola drinks have a pH of about 3.0, while milk has a pH of about 7.0. How many times greater is the H
3
O+ concentration in diet cola than in milk?
What is the pH of a solution prepared by mixing 50 mL of a 0.10 M HCl solution with 150 mL of pure water?
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
Diet cola drinks have a pH of about 3.0, while milk has a pH of about 7.0. How many times greater is the H
3
O
+
concentration in diet cola than in milk?
Concentration
A solution of LiOH is made by mixing an unknown amount of LiOH with 1 L of water. The pOH is measured to be 3.65, what is the concentration of LiOH?
MW Li: 7 g/mol
MW O: 16 g/mol
pH: Neutralization
A student adds 11.6 mL of a 3.7M KOH solution, to 29 mL of a 1.4 M HCl. What is the final pH after the addition?
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).
To 150 mL of water was added 0.18 moles of ammonia (NH
3
K
b
= 2.3 x 10
-5
) calculate the pH.
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
What is the pH of a solution made by mixing 22g of NaOH in 3.1 L of water?
Molecular formula: Concentration
A solution of HBr has a pOH of 12.2, what is the [H
+
] concentration?
What is the pH of a solution of 0.1 M sodium acetate (NaCH
3
CO
2
) given that the Ka for acetic acid is 1.8×10
−5
?
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
To a
90
m
L
90\ mL
90
m
L
of
0.17
M
0.17\ M
0.17
M
of
H
F
\rm HF
HF
is added
25
m
L
25\ mL
25
m
L
of
0.06
M
0.06\ M
0.06
M
N
a
O
H
\rm NaOH
NaOH
. The
K
a
K_a
K
a
of
H
F
\rm HF
HF
is
7.2
×
10
−
4
7.2 \times 10^{-4}
7.2
×
1
0
−
4
. Calculate the
p
H
\rm pH
pH
of the solution.
What is the pH of pure, neutral water at 37°C? At 37°C, K
w
= 2.4x10
-14
.
A student titrated 10.00 mL of 0.10 M sodium acetate (CH
3
COONa) with HCℓ and determined that 10.00 mL of HCℓ was needed to reach the equivalence point. At equivalence, what is the expected pH?
K
a
of CH
3
COOH = 1.8×10
-5
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
What is the pH of a solution prepared by mixing 50 mL of a 0.10 M HCl solution with 150 mL of pure water?
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?
If the pH of pure water is 6.80 at 37 °C, calculate K
w
pOH and [OH
-
] at this temperature.
Equilibrium: Auto-ionization of water
Given the equilibrium information for water below, what is the concentration of hydroxide ions in a solution of 1.5 M HCl?
2 H
2
O (l)
⇌
H
3
O+ (aq) + OH
-
(aq), K
c
= 1x10
-14
at 20
o
C
Equilibrium: ICE Tables and Auto-ionization of Water
Given the equilibrium information for water below, what is the concentration of hydroxide ions in water?
2 H
2
O (l) ⇌ H
3
O
+
(aq) + OH
-
(aq), K
c
= 1x10
-14
at 20
o
C
If the pH of pure water is 6.80 at 37 °C, calculate K
w
pOH and [OH
-
] at this temperature.
The compound
fluoroacetic acid
(shown), has a pK
a
value of 2.59. What is pK
b
of its conjugate base?
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
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?