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Standard XII

Chemistry

Gibbs Free Energy & Spontaneity

Which of the ...

Question

Which of the following best determines whether a reaction is spontaneous?

Change in Gibbs free energy,

Δ G

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Change in entropy,

Δ S

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Change in kinetic energy,

Δ K E

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Change in enthalpy,

Δ H

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Change in heat of formation,

Δ H_{f}^{0}

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Solution

The correct option is E Change in Gibbs free energy, $Δ G$
Change in Gibbs free energy, $Δ G$ best determines whether a reaction is spontaneous.
For spontaneous reaction, $Δ G < 0$
For non spontaneous reaction $Δ G > 0$
For equilibrium reaction $Δ G = 0$

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Similar questions

Q. In an irreversible process taking place at constant T and P and in which only pressure-volume work is being done the change in Gibbs free energy

(Δ G)

and change in entropy

(Δ S)

satisfy the criteria:

Gibbs-Helmholtz equation relates the free energy change to the enthalpy and entropy changes of the process as

(Δ G)_{P T} = Δ H - T Δ S

The magnitude of

Δ H

does not change much with the change in temperature but the entropy factor

T Δ S

changes appreciably.
Thus, spontaneity of a process depends very much on temperature.

For the reaction at

25^{\circ} C

X_{2} O_{4} (l) ⟶ 2 X O_{2}

Δ H = 2.0 K c a l

and

Δ S = 20 c a l K^{- 1}

the reaction would be:

Q. In the reaction

P + Q \to R + S

, there is no change in entropy. Enthalpy change for the reaction (

Δ H

) is 12 kJ

m o l^{- 1}

. Under the conditions, reaction will have negative value of free energy change:

Gibbs-Helmholtz equation relates the free energy change to the enthalpy and entropy changes of the process as

(Δ G)_{P T} = Δ H - T Δ S

The magnitude of

Δ H

does not change much with the change in temperature but the entropy factor

T Δ S

changes appreciably. Thus, spontaneity of a process depends very much on temperature.

For the reaction at

298 K

2 A + B ⟶ C,

Δ H = 100 K c a l

and

Δ S = 0.020 K c a l K^{- 1}

. If

Δ H

and

Δ S

are assumed to be constant over the temperature range, at what temperature will the reaction become spontaneous?

Q. Assertion :The thermodynamic factor which determines the spontaneity of a process is the free energy. For a process to be spontaneous the free energy must be -ve Reason: The change in free energy is related to the change in enthalpy and change in entropy. The change in entropy for a process must always be positive if it is spontaneous.

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Which of the following best determines whether a reaction is spontaneous?

The correct option is E Change in Gibbs free energy, ΔGChange in Gibbs free energy, ΔG best determines whether a reaction is spontaneous.For spontaneous reaction, ΔG<0For non spontaneous reaction ΔG>0For equilibrium reaction ΔG=0

The correct option is E Change in Gibbs free energy, $Δ G$
Change in Gibbs free energy, $Δ G$ best determines whether a reaction is spontaneous.
For spontaneous reaction, $Δ G < 0$
For non spontaneous reaction $Δ G > 0$
For equilibrium reaction $Δ G = 0$