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Gibbs energy, spontaneity and relation to equilibrium constant
JEE Main level
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Difficulty 2 of 3
td102
For the vaporisation of a liquid at its normal boiling point,
Δ
v
a
p
H
=
38.6
kJ
mo
l
−
1
and
Δ
v
a
p
S
=
104
J
K
−
1
mo
l
−
1
. The normal boiling point is about
A
371
K
B
98
K
C
3.71
K
D
644
K
Answer: A
At the boiling point liquid and vapour are in equilibrium, so
Δ
G
=
0
and
T
b
=
Δ
H
/Δ
S
=
38600/104
=
371.2
K
. The value
98
is the result in
∘
C
, not in kelvin.
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