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Byju's Answer
Standard XII
Chemistry
Heat of Formation
Kc values for...
Question
K
c
values for
3
2
H
2
+
1
2
N
2
⇌
N
H
3
are
0.0266
and
0.0129
a
t
m
−
1
respectively at
350
o
C
and
400
o
C
.
Calculate the heat of formation of
N
H
3
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Solution
Using van't haff equation
h
n
(
K
e
K
1
)
=
Δ
r
H
o
R
[
1
T
1
−
1
T
2
]
We have :
T
1
=
350
o
C
=
623
K
,
K
1
=
0.0266
a
t
m
−
1
T
2
=
400
o
C
=
673
K
,
K
2
=
0.0129
a
t
m
−
1
Putting these values in equation, We get:
ln
(
0.0266
0.0129
)
=
Δ
r
H
o
0.082
[
1
628
−
1
678
]
⇒
Δ
r
H
o
=
−
0.497
K
J
Enthalpy of the reaction
=
−
0.497
K
J
∴
Heat of formation
=
0.497
K
J
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Similar questions
Q.
K
c
for
3
2
H
2
+
1
2
N
2
⇌
N
H
3
are 0.0266 and 0.0129
a
t
m
−
1
respectively at
350
o
C
and
400
o
C
. Calculate heat of formation of
N
H
3
.
Q.
K
C
for
3
/
2
H
2
+
1
/
2
N
2
⇌
N
H
3
are 0.0266 and
0.0129
a
t
m
−
1
respectively, at 350
o
C and 400
o
C. Calculate the heat of formation of
N
H
3
.
Q.
Heat of formation of
N
H
3
at
4298
K
and constant pressure is
−
11
k
c
a
l
m
o
l
−
1
. Calculate heat of formation of
N
H
3
at
398
K
and constant pressure. What are corresponding values at constant volume?
Q.
Δ
G
o
(
298
K
)
for the reaction
1
2
N
2
+
3
2
H
2
K
1
⇌
N
H
3
is -16.5 kJ
m
o
l
−
1
. The equilibrium constant
(
K
1
)
at
25
o
C
& the equilibrium constant
K
2
and
K
3
for the following reactions are
N
2
+
3
H
2
K
2
⇌
2
N
H
3
N
H
3
K
3
⇌
1
2
N
2
+
3
2
H
2
Q.
Calculate the equilibrium constant
(
K
c
)
for the formation of
N
H
3
in the following reaction:
N
2
(
g
)
+
3
H
2
(
g
)
⇌
2
N
H
3
(
g
)
At equilibrium, the concentration of
N
H
3
,
H
2
and
N
2
are
1.2
×
10
−
2
,
3.0
×
10
−
2
and
1.5
×
10
−
2
M
respectively.
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