In this chapter we'll check again concepts of chemical equilibrum, energy, gibbs free energy, to see who involved are in the thermodynamics theories.
We need to recall that the relative concentrations of reactants and products in the equilibrium state is expressed by the equilibrium constant. In this chapter we will examine the relation between the Gibbs Free Energy change for a reaction and the equilibrium constant.
the most common expression for the chemical equilibrium is A + B ⇌ C + D , where the reactants are A and B and the products are C and D. This equation mainly applies for gases.
But here is a point: If the sym of the standard free energies of the products is less than that of the reactants, de Gibbs Free Energy Differential for the reaction will be negative and the reaction will proceed to the right. The products of the concentration of the products, divided by the product of the concentration of the reactants is called the equilibrium constant. This constant will help us to understand the phenomenom of each reaction and other qualities. In order to understand how equilibrium constants relate to the differential of Gibbs Free Energy Differential (∆G°), we need to assume that all our reactants are gases, so that the free energy of the gas "a", for example, is given by the next expression: G(a) = G°(a) + RTln(P(a))
The free energy diferential for the reaction is the sum of all free energies of the products minus the sum of free energies of the reactants. So we obtain the next expression: ∆G = G(c) + G(d) - G(a) - G(b)
So we could and up to this expression: ∆G = ∆G° + RT(PcPd/PaPb)
and (PcPd/PaPb) we could express it like Q The free energy is a quanity that becomes more negative during the course of any natural process. Thus a chemical reaction takes place, "G" only falls and will never become more positive. Eventually a point is reached where any further transformation of reactants into products would cause G to increase. At this point "G" is at a minimum, and no further net chane can take place; the reaction is at equilibrium.