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Byju's Answer
Standard IX
Chemistry
pH of a Solution
H2O + H3PO-4⇋...
Question
H
2
O
+
H
3
P
O
−
4
⇋
H
3
O
+
+
H
P
O
2
−
4
Where,
p
K
1
=
2.15
and
p
K
2
= 7.2
Then, pH of 0.01 M
N
a
H
2
P
O
4
is:
A
9.35
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B
4.675
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C
2.675
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D
7.35
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Solution
The correct option is
A
4.675
N
a
H
2
P
O
4
is the salt produced at the
1
s
t
step neutralisation of
H
3
P
O
4
.
The salt undergoes hydrolysis and
p
H
=
1
2
p
k
1
+
1
2
p
k
2
=
1
2
×
2.15
+
1
2
×
7.2
=
4.675
So, the correct answer is
B
Suggest Corrections
0
Similar questions
Q.
H
2
O
+
H
3
P
O
4
⇌
H
3
O
+
+
H
2
P
O
4
−
;
p
K
1
=
2.15
H
2
O
+
H
2
P
O
−
4
⇌
H
3
O
+
+
H
P
O
2
−
4
;
p
K
2
=
7.20
Hence,
p
H
of
0.01
M
N
a
H
2
P
O
4
is:
Q.
H
3
P
O
4
+
H
2
O
⇌
H
3
O
+
+
H
2
P
O
−
4
;
p
K
1
=
2.15
H
2
P
O
−
4
+
H
2
O
⇌
H
3
O
+
+
H
P
O
−
2
4
;
p
K
2
=
7.20
H
e
n
c
e
,
p
H
o
f
0.01
M
N
a
H
2
P
O
4
i
s
:
Q.
H
3
P
O
4
+
H
2
O
⇌
H
3
O
+
+
H
2
P
O
−
4
p
K
1
=
2.15
H
2
P
O
−
4
+
H
2
O
⇌
H
3
O
+
+
H
P
O
2
4
−
p
K
2
=
7.20
Hence pH of 0.01 M
N
a
H
2
P
O
4
is:
Q.
Calculate pH of 0.05M potassium hydrogen phthalate,
K
H
C
8
H
4
O
4
.
H
2
C
8
H
4
O
4
+
H
2
O
→
H
3
O
+
+
H
C
8
H
4
O
−
4
.
p
K
1
=
2.94
.
H
C
8
H
4
O
−
4
+
H
2
O
→
H
3
O
+
+
C
8
H
4
O
−
2
4
.
p
K
2
=
5.44
.
Q.
H
2
O
+
H
3
P
O
4
⇌
H
3
O
+
+
H
2
P
O
−
4
;
p
K
1
=
2.15
H
2
O
+
H
2
P
O
−
4
⇌
H
3
O
+
+
H
2
P
O
2
−
4
;
p
K
2
=
7.20
Hence, pH of
0.01
M
N
a
H
2
P
O
4
is:
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