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Question
Chemistry
If the bond energies of H - H , Br - Br and H - Br are 433,192 and 364 kJ mol -1 respectively, then Δ H° for the reaction H 2(g)+ Br 2(g) longrightarrow 2 HBr (g) is
Q. If the bond energies of
H
−
H
,
B
r
−
B
r
and
H
−
B
r
are
433
,
192
and
364
k
J
m
o
l
−
1
respectively, then
Δ
H
∘
for the reaction
H
2
(
g
)
+
B
r
2
(
g
)
⟶
2
H
B
r
(
g
)
is
2133
197
Manipal
Manipal 2007
Report Error
A
-261 kJ
50%
B
+103 kJ
0%
C
+261 kJ
50%
D
-103 kJ
0%
Solution:
For reaction
H
2
(
g
)
+
B
r
2
(
g
)
⟶
2
H
B
r
(
g
)
Δ
H
∘
=
?
On the basis of bond energies of
H
2
,
B
r
2
and
H
B
r
,
Δ
H
of above is calculated as follows
Δ
H
=
−
[
2
×
bond energy of
H
B
r
−
(bond
energy of
H
2
+
bond energy of
C
l
2
)
]
Δ
H
=
−
[
2
×
(
364
)
−
(
433
)
+
192
k
J
=
−
[
728
−
(
625
)]
k
J
=
−
103
k
J