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Byju's Answer
Standard XII
Chemistry
Heat of Reaction
H 2g + 1 / 2 ...
Question
H
2
(
g
)
+
1
2
O
2
(
g
)
→
H
2
O
(
l
)
;
Δ
H
=
−
286.2
k
J
;
H
2
O
(
l
)
→
H
+
(
a
q
)
+
O
H
−
(
a
q
)
;
Δ
H
=
+
57.3
k
J
. Enthalpy of ionisation of
O
H
−
in aqueous solution is:
A
−
228.5
k
J
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B
+
228.5
k
J
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C
−
343.5
k
J
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D
zero
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Solution
The correct option is
A
−
228.5
k
J
Solution:- (A)
−
228.5
k
J
Given:-
H
2
(
g
)
+
O
2
(
g
)
⟶
H
2
O
(
l
)
;
Δ
H
=
−
286.2
k
J
.
.
.
.
.
(
1
)
H
2
O
(
l
)
⟶
H
+
(
a
q
.
)
+
O
H
−
(
a
q
.
)
;
Δ
H
=
+
57.3
k
J
.
.
.
.
.
(
2
)
Adding
e
q
n
(
1
)
&
(
2
)
, we have
H
2
(
g
)
+
O
2
(
g
)
+
H
2
O
(
l
)
⟶
H
2
O
(
l
)
+
H
+
(
a
q
.
)
+
O
H
−
(
a
q
.
)
;
Δ
H
=
[
57.3
+
(
−
286.2
)
]
k
J
H
2
(
g
)
+
O
2
(
g
)
⟶
H
+
(
a
q
.
)
+
O
H
−
(
a
q
.
)
;
Δ
H
=
−
228.9
k
J
≈
−
228.5
k
J
Hence the enthalpy of ionisation of
O
H
−
in aqeuous solution is
−
228.5
k
J
.
Suggest Corrections
0
Similar questions
Q.
Consider the following reactions :
I)
H
+
(
a
q
)
+
O
H
−
(
a
q
)
=
H
2
O
(
l
)
;
Δ
H
=
−
X
1
k
J
.
m
o
l
−
1
II)
H
2
(
g
)
+
1
2
O
2
(
g
)
=
H
2
O
(
l
)
;
Δ
H
=
−
X
2
k
J
.
m
o
l
−
1
III)
C
O
2
(
g
)
+
H
2
(
g
)
=
C
O
(
g
)
+
H
2
O
(
l
)
;
Δ
H
=
+
X
3
k
J
.
m
o
l
−
1
IV)
C
2
H
2
(
g
)
+
5
2
O
2
(
g
)
=
2
C
O
(
g
)
+
H
2
O
(
l
)
;
Δ
H
=
+
X
4
k
J
.
m
o
l
−
1
Enthalpy of formation of
H
2
O
(
l
)
is:
Q.
Given, that,
H
2
O
(
l
)
→
H
+
(
a
q
)
+
O
H
−
(
a
q
)
;
Δ
H
=
57.32
k
J
H
2
(
g
)
+
1
2
O
2
(
g
)
→
H
2
O
(
l
)
;
Δ
H
=
−
286.02
k
J
Then, calculate the enthalpy of formation of
O
H
−
at
25
o
C
is:
Q.
The enthalpy of vaporisation of liquid water using data:
H
2
(
g
)
+
1
/
2
O
2
(
g
)
⟶
H
2
O
(
l
)
;
Δ
H
=
−
285.77
k
J
/
m
o
l
e
H
2
(
g
)
+
1
/
2
O
2
(
g
)
⟶
H
2
O
(
l
)
;
Δ
H
=
−
241.84
k
J
/
m
o
l
e
Q.
Given that
;
H
2
O
(
l
)
→
H
+
(
a
q
)
+
O
H
−
(
a
q
)
;
Δ
H
=
57.32
kJ
H
2
(
g
)
+
1
2
O
2
(
g
)
→
H
2
O
(
l
)
;
Δ
H
=
−
286.02
kJ
Then calculate the enthalpy of formation of
O
H
−
at
25
o
C.
Q.
Calculate enthalpy for formation of ethylene from the following data:
(I)
C
(
g
r
a
p
h
i
t
e
)
+
O
2
(
g
)
→
C
O
2
(
g
)
;
Δ
H
=
−
393.5
k
J
(II)
H
2
(
g
)
+
1
2
O
2
(
g
)
→
H
2
O
(
l
)
;
Δ
H
=
−
286.2
k
J
(III)
C
2
H
4
(
g
)
+
3
O
2
(
g
)
→
2
C
O
2
(
g
)
+
2
H
2
O
(
l
)
;
Δ
H
=
−
1410.8
k
J
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