Equilibrium constant

The equilibrium constant K ( equilibrium constant) gives a ratio of activities or corresponding sizes (see below) of the substances involved in a chemical reaction again, for a net flux is energetically impossible by the chemical reaction. The activity of a substance under certain circumstances, with the amount of substance concentration equal to, usually with low molar concentration. If the reactants and products of the reaction in the given by the equilibrium constant activity ratio before, so the reaction is in chemical equilibrium. Then no net flow takes place through the reaction, the flow through the forward reaction is the same as the flow through the reverse reaction, the free energy is constant, its change is zero.

Definition

The equilibrium constant for a reaction

Is thermodynamically defined by the ratio ( mass action law ) of reactants and products at equilibrium.

This is either the concentration of the substance ( amount of substance per volume of =, also written ), mole fraction, molality, pressure, fugacity or relative activity.

Is the change in the standard reaction Gibbs energy of a reaction known we can immediately estimate the standard equilibrium constant calculated:

Wherein the universal gas constant, temperature, and the Euler number.

Importance

The equilibrium constant makes possible a statement on the direction and the energetics of the reaction. It gives no information about the rate of the reaction.

Applies

So the net reaction can only take place in the following direction

Applies

So the net reaction can only take place in the following direction

There is no net flow through the reaction ( The flow through the outward or return reaction are then equal., you can, but need not be zero).

Therefore, we define:

As an alternative force. As long as a reaction takes place. If the force is zero, however, so the system is in equilibrium. The equilibrium constant is a function of temperature. In the reaction is not directly involved substances, the equilibrium constant of a reaction can change, for example, are equilibrium constants in aqueous media often strongly influenced by pH dependent (see Nernst equation).