Which of the following is not correct-a - G is zero for a reversible reaction-b - G is positive for a spontaneous reaction-c - G is negative for a spontaneous reaction-d - G is positive for a non-spontaneous reaction-

(b) ΔG gives a criteria for spontaneity at constant pressure and temperature. (i) If ΔG is negative ( lt; 0), the process is spontaneous. (ii) If ΔG is positi ...

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Standard XII

Chemistry

Gibbs Free Energy & Spontaneity

Which of the ...

Question

Which of the following is not correct?
(a) $Δ$ G is zero for a reversible reaction.
(b) $Δ$ G is positive for a spontaneous reaction.
(c) $Δ$ G is negative for a spontaneous reaction.
(d) $Δ$ G is positive for a non-spontaneous reaction.

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Solution

(b)

$Δ$ G gives a criteria for spontaneity at constant pressure and temperature.
(i) If $Δ$ G is negative (< 0), the process is spontaneous.
(ii) If $Δ$ G is positive (> 0), the process is non-spontaneous.
(iii) If $Δ$ G is zero then reaction is equilibrium.

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Similar questions

Q. Assertion :There is no reaction known for which

Δ G

is positive, yet it is spontaneous. Reason: For photochemical reaction,

Δ G

is negative.

Q. For spontaneous reaction,

Δ G

is:

Q. Assertion :All exothermic reactions are spontaneous at room temperature. Reason:

Δ G

=-ve for above reactions and for spontaneous reactions

Δ G = - v e

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.

Which of the following is correct?

Q. For non-spontaneous process at constant T & P

Δ G

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Which of the following is not correct? (a) Δ G is zero for a reversible reaction. (b) Δ G is positive for a spontaneous reaction. (c) Δ G is negative for a spontaneous reaction. (d) Δ G is positive for a non-spontaneous reaction.

(b) ΔG gives a criteria for spontaneity at constant pressure and temperature. (i) If ΔG is negative (< 0), the process is spontaneous. (ii) If ΔG is positive (> 0), the process is non-spontaneous. (iii) If ΔG is zero then reaction is equilibrium.

Which of the following is not correct?
(a) $Δ$ G is zero for a reversible reaction.
(b) $Δ$ G is positive for a spontaneous reaction.
(c) $Δ$ G is negative for a spontaneous reaction.
(d) $Δ$ G is positive for a non-spontaneous reaction.

(b)

$Δ$ G gives a criteria for spontaneity at constant pressure and temperature.
(i) If $Δ$ G is negative (< 0), the process is spontaneous.
(ii) If $Δ$ G is positive (> 0), the process is non-spontaneous.
(iii) If $Δ$ G is zero then reaction is equilibrium.