The change in the Gibbs free energy of a chemical reaction can be defined as the difference in the Gibbs free energy of the products and that of the reactants. This can be represented as
ΔG = G(products) - G(reactants)
When ∆G =0, (that means G(reactants) = G (products)
At this stage, the system is said to have achieved equilibrium.
∆G > 0, the process is non - spontaneous
The change in the Gibbs energy for a reaction in which all the reactants and products are in the standard state is known as standard Gibbs energy change
(∆G°)
The relationship between Gibbs energy changeand standard Gibbs energy changeis given as
∆G = ∆G° + RTlnQ
where,
R is universal gas constant
T is absolute temperature
Q is reaction quotient
For a reaction A + B C + D
'.' Q =
ΔG = ΔG° + RTln
At equilibrium, when ΔG = 0 and Q = Kc, the equation
ΔG = ΔG° + RTln
Becomes ΔG = ΔG° + RTlnKc
ΔG° = - RTlnKc
lnKc =
Taking antilog on both sides,
K = e
If ΔG° < 0, then becomes positive and e - ∆ G ⁰/ RT >1
If k > 1 It is a spontaneous reaction.
If ΔG° > 0, then becomes positive and e - ∆ G ⁰/ RT <1
If k < 1 It is a non-spontaneous reaction.
According to Le Chatelier's principle: "If a system at equilibrium is subjected to a change in the temperature, pressure or concentration of the reactants or the products that govern the equilibrium, then the equilibrium position shifts in the direction in which this change is reduced or nullified."
The change in the Gibbs free energy of a chemical reaction can be defined as the difference in the Gibbs free energy of the products and that of the reactants. This can be represented as
ΔG = G(products) - G(reactants)
When ∆G =0, (that means G(reactants) = G (products)
At this stage, the system is said to have achieved equilibrium.
∆G > 0, the process is non - spontaneous
The change in the Gibbs energy for a reaction in which all the reactants and products are in the standard state is known as standard Gibbs energy change
(∆G°)
The relationship between Gibbs energy changeand standard Gibbs energy changeis given as
∆G = ∆G° + RTlnQ
where,
R is universal gas constant
T is absolute temperature
Q is reaction quotient
For a reaction A + B C + D
'.' Q =
ΔG = ΔG° + RTln
At equilibrium, when ΔG = 0 and Q = Kc, the equation
ΔG = ΔG° + RTln
Becomes ΔG = ΔG° + RTlnKc
ΔG° = - RTlnKc
lnKc =
Taking antilog on both sides,
K = e
If ΔG° < 0, then becomes positive and e - ∆ G ⁰/ RT >1
If k > 1 It is a spontaneous reaction.
If ΔG° > 0, then becomes positive and e - ∆ G ⁰/ RT <1
If k < 1 It is a non-spontaneous reaction.
According to Le Chatelier's principle: "If a system at equilibrium is subjected to a change in the temperature, pressure or concentration of the reactants or the products that govern the equilibrium, then the equilibrium position shifts in the direction in which this change is reduced or nullified."