Gibbs free energy various forms

In summary, ΔG°' is the value of ΔG° at 25°C, while ΔG° is the change in free energy under non-standard conditions. ΔG° is a function of temperature, while ΔG°' is constant at all conditions. ΔG is the change in free energy when pure species in States 1 and 2 are not at 1 atm pressure.
  • #1
Raghav Gupta
1,011
76
What is the difference between 1) ΔG°' and ΔG°
and 2) ΔG°' and ΔG ?
ΔG° I think it is the gibbs free energy at standard state means at room temperature 1 atm pressure.
 
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  • #2
##\Delta G^0## is constant at all conditions. Its ##\Delta G## that changes with change in conditions.
 
  • #3
What about ΔG°' ?
 
  • #4
Where did you read it?
 
  • #5
It was given in the question of our assignment.
 
  • #6
May be something like the conditions that are common in your field of science, say pH is 7 and temp is 36 °C.
 
  • #7
Raghav Gupta said:
What is the difference between 1) ΔG°' and ΔG°
and 2) ΔG°' and ΔG ?
ΔG° I think it is the gibbs free energy at standard state means at room temperature 1 atm pressure.
ΔG0 is the change in free energy between state 1 and state 2, whereState 1: Stoichiometric quantities of pure reactants in separate containers, each at temperature T and 1 atm pressure

State 2: Corresponding stoichiometric quantities of pure products in separate containers, each at temperature T and 1 atm pressure

So ΔG0 is a function of temperature.

Chet
 
  • #8
He didn't ask about that.
 
  • #9
Titan97 said:
##\Delta G^0## is constant at all conditions. Its ##\Delta G## that changes with change in conditions.
Alcathous said:
He didn't ask about that.
What do the words "ΔG° I think it is the gibbs free energy at standard state means at room temperature 1 atm pressure." mean to you?

Chet
 
  • #10
I've never seen ΔG0' used before, but, apparently ΔG0' is the value of ΔG0 at 25 C (see post #7).

Incidentally, regarding ΔG, this is the change in free energy if the pressures of the pure species in States 1 and 2 (see post #7) are not all equal to 1 atm.

Chet
 

1. What is Gibbs free energy and why is it important in chemistry?

Gibbs free energy is a thermodynamic quantity that represents the maximum amount of work that can be extracted from a system at a constant temperature and pressure. It is important in chemistry because it helps determine whether a chemical reaction will occur spontaneously or not. If the Gibbs free energy is negative, the reaction is spontaneous and can proceed without any external influence.

2. What are the different forms of Gibbs free energy?

There are three forms of Gibbs free energy: standard Gibbs free energy, Gibbs free energy of reaction, and Gibbs free energy of formation. Standard Gibbs free energy (ΔG°) is the change in free energy that occurs under standard conditions (1 atm pressure, 25°C temperature, and 1 M concentration). Gibbs free energy of reaction (ΔG) is the change in free energy that occurs in a reaction at any given conditions. Gibbs free energy of formation (ΔGf) is the change in free energy that occurs when one mole of a compound is formed from its constituent elements in their standard states.

3. How is Gibbs free energy related to enthalpy and entropy?

The relationship between Gibbs free energy (G), enthalpy (H), and entropy (S) is described by the equation ΔG = ΔH - TΔS. This equation, known as the Gibbs-Helmholtz equation, shows that the change in free energy (ΔG) is dependent on the change in enthalpy (ΔH) and the change in entropy (ΔS) of a system, as well as the temperature (T).

4. Can Gibbs free energy be negative?

Yes, Gibbs free energy can be negative. A negative value for ΔG indicates that the reaction is spontaneous and can occur without any external influence. However, it is important to note that the value of ΔG is dependent on the conditions of the system, and a reaction that may be spontaneous under one set of conditions may not be spontaneous under another set of conditions.

5. How is Gibbs free energy used to predict the equilibrium of a chemical reaction?

The Gibbs free energy change (ΔG) can be used to predict the direction of a chemical reaction and whether it will reach equilibrium. If ΔG is negative, the reaction is spontaneous and will proceed in the forward direction. If ΔG is positive, the reaction is non-spontaneous and will proceed in the reverse direction. At equilibrium, ΔG is equal to zero, indicating that the reaction has reached a state of balance and will not proceed in either direction without external influence.

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