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Byju's Answer
Standard XII
Chemistry
Heat of Formation
If H 2 + 1 ...
Question
If
H
2
+
1
2
O
2
⟶
H
2
O
;
△
H
=
68.09
k
c
a
l
K
+
H
2
O
+
w
a
t
e
r
⟶
K
O
H
(
a
q
)
+
1
2
H
2
:
△
H
=
−
48.0
k
c
a
l
K
O
H
+
w
a
t
e
r
⟶
K
O
H
(
a
q
)
:
△
H
=
−
14.0
k
c
a
l
What is the heat of formation of
K
O
H
?
Open in App
Solution
H
2
+
1
2
O
2
⇌
H
2
O
△
H
=
68.09
k
c
a
l
.
.
.
.
(
i
)
K
+
H
2
O
+
w
a
t
e
r
→
K
O
H
(
a
q
)
+
1
2
H
2
△
H
=
−
48
k
c
a
l
.
.
.
.
(
i
i
)
K
O
H
+
w
a
t
e
r
→
K
O
H
(
a
q
)
△
H
=
−
14
k
c
a
l
.
.
.
.
(
i
i
i
)
We have to find
△
H
for reaction.
K
+
1
2
O
2
+
1
2
H
2
→
K
O
H
.
.
.
.
(
i
v
)
Rkn
(
i
v
)
is given as
(
i
i
)
−
(
i
i
i
)
+
(
i
)
∴
△
H
for
(
i
v
)
=
△
H
2
−
△
H
3
+
△
H
1
=
−
48
+
14
+
68.09
=
34.09
k
c
a
l
Suggest Corrections
0
Similar questions
Q.
If
H
2
+
1
2
O
2
→
H
2
O
;
Δ
H
=
−
68.39
K
c
a
l
K
+
H
2
O
+
w
a
t
e
r
→
K
O
H
(
a
q
)
+
1
2
H
2
;
Δ
H
=
−
48.0
K
c
a
l
K
O
H
+
w
a
t
e
r
→
K
O
H
(
a
q
)
Δ
H
=
−
14.0
K
c
a
l
the heat of formation of
K
O
H
is
Q.
If
H
2
+
1
2
O
2
→
H
2
O
;
Δ
H
=
−
68.09
k
c
a
l
K
+
H
2
O
+
w
a
t
e
r
→
K
O
H
(
a
q
.
)
+
1
2
H
2
;
Δ
H
=
−
48.0
k
c
a
l
K
O
H
+
w
a
t
e
r
→
K
O
H
(
a
q
)
;
Δ
H
=
−
14.0
k
c
a
l
the heat of formation of
K
O
H
is:
Q.
H
2
+
1
/
2
O
2
⟶
H
2
O
;
Δ
H
⊖
=
−
68
K
c
a
l
.
K
+
H
2
O
+
a
q
⟶
K
O
H
(
a
q
)
+
1
/
2
H
2
;
Δ
H
⊖
=
−
48
K
c
a
l
.
K
O
H
+
a
q
⟶
K
O
H
(
a
q
)
;
Δ
H
⊖
=
−
14
K
c
a
l
From the above data, the standard heat of formation of
K
O
H
i
n
K
c
a
l
is
Q.
Following are the thermochemical reactions:
H
2
+
1
2
O
2
→
H
2
O
;
Δ
H
=
−
68.39
kcal/mol
K
+
H
2
O
→
K
O
H
(
a
q
)
+
1
2
H
2
;
Δ
H
=
−
48.0
kcal/mol
K
O
H
+
H
2
O
→
K
O
H
(
a
q
)
;
Δ
H
=
−
14.0
kcal/mol
The heat of formation (in kcal/mol) of
K
O
H
is:
Q.
Heat of formation of KOH(s) using the following equations :
K
(
s
)
+
H
2
O
(
l
)
+
(
a
q
)
⟶
K
O
H
(
a
q
)
+
1
2
H
2
(
g
)
;
Δ
H
=
−
48.0
k
c
a
l
H
2
(
g
)
+
1
2
O
2
(
g
)
⟶
H
2
O
(
l
)
;
Δ
H
=
−
68.4
k
c
a
l
K
O
H
(
s
)
+
(
a
q
)
⟶
K
O
H
(
a
q
)
;
Δ
H
=
−
14.0
k
c
a
l
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