Gibbs Free Energy for non-standard conditions

• sgstudent
In summary, the equation ΔG=ΔG°+RTlnQ is used for reactions that are not under standard conditions. Under non-standard conditions, it means that the values for ΔG and Q are not at their standard states. The Q in this case can be either Qp, based on the partial pressure of the gas, or Qc, based on the concentration. Standard conditions vary for different states of matter and can also differ in biology compared to chemistry. For a gas, standard conditions correspond to a fugacity of 1 bar, while for a solution, it is an activity of 1 mol/kg for the solute and pure solvent for the solvent. For a solid, the standard state is the pure solid.
sgstudent
ΔG=ΔG°+RTlnQ are for reactions that are not under standard conditions. What does it mean under non-standard conditions for the ΔG?

And what is the Q in this case? Is it Qp where it is based on the partial pressure of the gas or Qc which is based on the concentration?

Thanks

Standard conditions are a convention and differ for solids liquids and gasses, as well as for solutes and solvents. Also, in biological systems other standard conditions are chosen than in chemistry.
A gas is under standard conditions when its fugacity (which is equal to its partial pressure in a good approximation for not too high pressures) is 1 bar. For a solution, standard condition of the solute is an activity of 1 mol/kg. For the solvent, the standard state is the pure solvent. For a solid, the pure solid.

1. What is Gibbs Free Energy for non-standard conditions?

Gibbs Free Energy for non-standard conditions is a thermodynamic property that describes the amount of energy available to do work in a system at a given temperature, pressure, and composition. It takes into account the effects of non-standard conditions, such as changes in temperature and pressure, on the system's energy.

2. How is Gibbs Free Energy for non-standard conditions calculated?

The Gibbs Free Energy for non-standard conditions is calculated using the equation: ΔG = ΔG° + RTln(Q), where ΔG° is the standard Gibbs Free Energy, R is the gas constant, T is the temperature in Kelvin, and Q is the reaction quotient. This equation takes into account the effects of non-standard conditions on the system.

3. What is the significance of Gibbs Free Energy for non-standard conditions?

Gibbs Free Energy for non-standard conditions is significant because it tells us whether a chemical reaction will occur spontaneously or not under non-standard conditions. If ΔG is negative, the reaction will occur spontaneously, while a positive ΔG indicates that the reaction will not occur spontaneously and will require energy input to proceed.

4. How does temperature affect Gibbs Free Energy for non-standard conditions?

Temperature has a direct effect on Gibbs Free Energy for non-standard conditions. As temperature increases, the value of ΔG decreases, making it more likely for a reaction to occur spontaneously. Similarly, as temperature decreases, the value of ΔG increases, making it less likely for a reaction to occur spontaneously.

5. Can Gibbs Free Energy for non-standard conditions be negative?

Yes, Gibbs Free Energy for non-standard conditions can be negative. A negative value indicates that the reaction is spontaneous under non-standard conditions and will occur without the need for energy input. However, it is important to note that the reaction may still require a catalyst or some other form of activation energy to proceed.

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