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Byju's Answer
Standard XII
Chemistry
Spontaneity
For a reactio...
Question
For a reaction to be spontaneous, the sign of Gibbs Free Energy change
Δ
G
is ________.
A
always negative
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B
always positive
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C
sometimes negative
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D
sometimes positive
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E
The sign of
Δ
G
has no effect on spontaneity
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Solution
The correct option is
A
always negative
Δ
G
=
negative for spontaneous reaction.
Δ
G
=
Positive for non-spontaneous reaction.
Δ
G
=
0 for equilibrium.
Hence, the correct option is A.
Suggest Corrections
0
Similar questions
Q.
Free energy,
G
=
H
−
T
Δ
S
, is a state function that indicates whether a reaction is spontaneous or non-spontaneous. If you think of
T
S
as the part of the system`s energy that is disordered already, then
(
H
−
T
S
)
is the part of the system`s energy that is still ordered and therefore free to cause spontaneous change by becoming disordered.
Also,
Δ
G
=
Δ
H
−
T
Δ
S
From the second law of Thermodynamics, a reaction is spontaneous if
Δ
t
o
t
a
l
S
is positive, non-spontaneous if
Δ
t
o
t
a
l
S
is negative, and at equilibrium if
Δ
t
o
t
a
l
S
is zero.
Since,
−
T
Δ
S
=
Δ
G
and since
Δ
G
and
Δ
S
have opposite signs, we can restate the Thermodynamic criterion for the spontaneity of a reaction carried out at a constant temperature and pressure.
If
Δ
G
<
0
, the reaction is spontaneous
If
Δ
G
>
0
, the reaction is non-spontaneous
If
Δ
G
=
0
, the reaction is at equilibrium
Read the above paragraph carefully and answer the following questions based on the above comprehension.
A particular reaction has a negative value for the free energy change. Then at ordinary temperature:
Q.
Free energy,
G
=
H
−
T
Δ
S
, is a state function that indicates whether a reaction is spontaneous or non-spontaneous. If you think of
T
S
as the part of the system`s energy that is disordered already, then
(
H
−
T
S
)
is the part of the system`s energy that is still ordered and therefore free to cause spontaneous change by becoming disordered.
Also,
Δ
G
=
Δ
H
−
T
Δ
S
From the second law of Thermodynamics, a reaction is spontaneous if
Δ
t
o
t
a
l
S
is positive, non-spontaneous if
Δ
t
o
t
a
l
S
is negative, and at equilibrium if
Δ
t
o
t
a
l
S
is zero.
Since,
−
T
Δ
S
=
Δ
G
and since
Δ
G
and
Δ
S
have opposite signs, we can restate the Thermodynamic criterion for the spontaneity of a reaction carried out at a constant temperature and pressure.
If
Δ
G
<
0
, the reaction is spontaneous
If
Δ
G
>
0
, the reaction is non-spontaneous
If
Δ
G
=
0
, the reaction is at equilibrium
Read the above paragraph carefully and answer the following questions based on the above comprehension.
One mol of ice is converted to liquid at
273
K
;
H
2
O
(
s
)
and
H
2
O
(
l
)
have entropies
38.20
and
60.03
J
m
o
l
−
1
d
g
−
1
. Enthalpy change in the conversion will be:
Q.
Δ
G
is the net energy available to do useful work and is a measure of free energy. If a reaction has positive enthalpy change and positive entropy change, under what conditions will the reaction be spontaneous?
Q.
A reaction has a enthalpy
(
Δ
H
)
=
−
40
kcal
at
400
K
. Above
400
K
, the reaction is spontaneous and below this temperature, it is non spontaneous. The values of Gibbs free energy (
Δ
G
) and entropy (
Δ
S
) at
400
K
are respectively:
Q.
Free energy,
G
=
H
−
T
Δ
S
, is a state function that indicates whether a reaction is spontaneous or non-spontaneous. If you think of
T
S
as the part of the system`s energy that is disordered already, then
(
H
−
T
S
)
is the part of the system`s energy that is still ordered and therefore free to cause spontaneous change by becoming disordered.
Also,
Δ
G
=
Δ
H
−
T
Δ
S
From the second law of Thermodynamics, a reaction is spontaneous if
Δ
t
o
t
a
l
S
is positive, non-spontaneous if
Δ
t
o
t
a
l
S
is negative, and at equilibrium if
Δ
t
o
t
a
l
S
is zero.
Since,
−
T
Δ
S
=
Δ
G
and since
Δ
G
and
Δ
S
have opposite signs, we can restate the Thermodynamic criterion for the spontaneity of a reaction carried out at a constant temperature and pressure.
If
Δ
G
<
0
, the reaction is spontaneous
If
Δ
G
>
0
, the reaction is non-spontaneous
If
Δ
G
=
0
, the reaction is at equilibrium
Read the above paragraph carefully and answer the following questions based on the above comprehension.
If an endothermic reaction is non-spontaneous at freezing point of water and becomes feasible at its boiling point, then:
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