Version 260 – Quiz 3 – Laude – (52390)
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pH =

log [H
+
]
pOH =

log [OH

]
K
w
= 10

14
[H
+
][OH

] =
K
w
K
a
K
b
=
K
w
[H
+
] =
K
a
(
C
a
/C
b
)
pH = p
K
a
+ log(
C
b
/C
a
)
[OH

] =
K
b
(
C
b
/C
a
)
pOH = p
K
b
+ log(
C
a
/C
b
)
[H
+
] = (
K
ax
K
ay
)
1
/
2
pH = 0
.
5(p
K
ax
+ p
K
ay
)
001
5.0 points
What would be the pH of a 1 M solution of
Na
2
HPO
4
?
Assume H
3
PO
4
has a p
K
a
1
of 2
and a p
K
a
2
of 7 and a p
K
a
3
of 13.
1.
4.5
2.
2
3.
13
4.
10
correct
5.
7
6.
7.5
Explanation:
For a solution composed of a single ampho
teric species (HPO
4
2

),
pH = 0
.
5(p
K
a
2
+ p
K
a
3
)
= 0
.
5(7 + 13)
= 10
002
5.0 points
One liter of a buffer containing 2 M H
2
CO
3
and 1
.
5 M NaHCO
3
has 24 g of LiOH added
to it. What is the new pH? Assume the
K
a
1
of H
2
CO
3
is 2
.
5
×
10

4
.
1.
6
2.
3
3.
11
4.
4
correct
5.
10
6.
8
Explanation:
(24 g LiOH)
parenleftbigg
1 mol
24 g
parenrightbigg
= 1 mol LiOH
[H
+
] =
K
a
(
C
a
/C
b
)
=
(
2
.
5
×
10

4
)
(1 M
/
2
.
5 M)
= 10

4
pH = 4
003
5.0 points
A 1 M solution of NaOH is used to titrate a
1 M solution of C
6
H
5
COOH (benzoic acid). If
the
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 Spring '09
 Laude
 – Laude, COO−

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