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Byju's Answer
Standard XII
Chemistry
Heat of Formation
Consider the ...
Question
Consider the following reactions.
(a)
H
+
(
a
q
)
+
O
H
−
(
a
q
)
=
H
2
O
(
l
)
,
Δ
H
=
−
X
1
kJ
m
o
l
−
1
(b)
H
2
(
g
)
+
1
2
O
2
(
g
)
=
H
2
O
(
l
)
,
Δ
H
=
X
2
kJ
m
o
l
−
1
(c)
C
O
2
(
g
)
+
H
2
(
g
)
=
C
O
(
g
)
+
H
2
O
(
l
)
−
X
3
kJ
m
o
l
−
1
(d)
C
2
H
2
(
g
)
+
5
2
O
2
(
g
)
=
2
C
O
2
(
g
)
+
H
2
O
(
l
)
+
X
4
kJ
m
o
l
−
1
Enthalpy of formation of
H
2
O
(
l
)
is:
A
+
X
1
kJ
m
o
l
−
1
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B
−
X
2
kJ
m
o
l
−
1
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C
+
X
3
kJ
m
o
l
−
1
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D
−
X
4
kJ
m
o
l
−
1
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Solution
The correct option is
B
−
X
2
kJ
m
o
l
−
1
(a)
H
+
+
O
H
−
→
H
2
O
(
l
)
Δ
H
=
−
X
1
k
J
m
o
l
−
1
(b)
H
2
+
1
2
O
2
→
H
2
O
(
l
)
Δ
H
=
X
2
k
J
m
o
l
−
1
(c)
C
O
2
+
H
2
→
C
O
+
H
2
O
(
l
)
−
X
3
k
J
/
m
o
l
(d)
C
2
H
2
+
5
2
O
2
→
2
C
O
2
+
H
2
O
l
+
X
4
k
J
/
m
o
l
For enthalpy of formation all the reactant should be in standard form
50
6
is correct formation of enthalapy
Suggest Corrections
0
Similar questions
Q.
Calculate the standard enthalpy of formation of
C
H
3
O
H
(
l
)
from the following data.
C
H
3
O
H
(
l
)
+
3
2
O
2
(
g
)
→
C
O
2
(
g
)
+
2
H
2
O
(
l
)
;
Δ
H
o
=
−
726
kJ
m
o
l
−
1
C(graphite)
+
O
2
(
g
)
→
C
O
2
(
g
)
;
Δ
c
H
0
=
−
393
kJ
m
o
l
−
1
H
2
(
g
)
+
1
2
O
2
(
g
)
→
H
2
O
(
l
)
;
Δ
t
H
o
=
−
286
kJ
m
o
l
−
1
.
Q.
The
Δ
f
H
o
for the
C
O
2
(
g
)
,
C
O
(
g
)
and
H
2
O
(
l
)
are -393.5, -110.5 and -241.8
k
J
m
o
l
−
1
respectively. The standard enthalpy change (in
k
J
m
o
l
−
1
) for the given reaction is :
C
O
2
(
g
)
+
H
2
(
g
)
→
C
O
(
g
)
+
H
2
O
(
l
)
Q.
Given that :
2
C
(
s
)
+
2
O
2
(
g
)
→
2
C
O
2
(
g
)
;
Δ
H
=
−
787
kJ
H
2
(
g
)
+
1
/
2
O
2
(
g
)
→
H
2
O
(
l
)
;
Δ
H
=
−
286
kJ
C
2
H
2
(
g
)
+
5
2
O
2
(
g
)
→
2
C
O
2
(
g
)
+
H
2
O
(
l
)
;
Δ
H
=
−
1310
kJ.
Heat of formation of acetylene is:
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.
Consider the following reactions:
(
i
)
H
+
(
a
q
)
+
O
H
–
(
a
q
)
→
H
2
O
(
l
)
,
Δ
H
=
–
X
1
kJ mol
–
1
(
i
i
)
H
2
(
g
)
+
1
2
O
2
(
a
q
)
→
H
2
O
(
l
)
,
Δ
H
=
–
X
2
kJ mol
–
1
(
i
i
i
)
C
O
2
(
g
)
+
H
2
(
g
)
→
C
O
(
g
)
+
H
2
O
(
l
)
,
Δ
H
=
–
X
3
kJ mol
–
1
(
i
v
)
C
2
H
2
(
g
)
+
5
2
O
2
(
g
)
→
2
C
O
2
(
g
)
+
H
2
O
(
l
)
,
Δ
H
=
X
4
kJ mol
–
1
Enthalpy of formation of
H
2
O
(
l
)
is:
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