C H E M I C A L R E A C T I O N S

A N D E Q U I L I B R I U M

C H E M I C A L

E Q U I L I B R I U M

E Q U I L I B R I U M C A L C U L A T I O N S

CHEMICAL EQUILIBRIUM

In a chemical reaction, chemical equilibrium is the state in which both reactants and products are pre-sent in concentrations which have no further tendency to change with time. Usually, this state results when the forward reaction proceeds at the same rate as the reverse reaction. The reaction rates of the forward and backward reactions are generally not zero, but equal. Thus, there are no net changes in the concentrations of the reactant(s) and product(s). Such a state is known as dynamic equilibrium.

Chemical equilibrium is based on the fact that reversible reactions do not go to completion. Chemical equilibrium exists when two opposing reactions occur simultaneously at the same rate. A chemical equilibrium is a reversible reaction where the forward reaction rate is equal to the reverse reaction rate. Thus, Molecules are continually reacting, even though the overall composition

of the reaction mixture does not change.

The RATE of the forward reaction equals the RATE of the reverse reaction. Symbolically, this is repre-

sented as:

aA(g) + bB (g) ⇌ cC (g) + dD (g)

PRINCIPLES OF CHEMICAL EQUILIBRIUM

Chemical equilibrium is a state in which the rate of the forward reaction equals the rate of the backward reaction. In other words, there is no net change in concentrations of reactants and products. This kind

of equilibrium is also called dynamic equilibrium.

I N T R O : I N C H E M I C A L

E Q U I L I B R I U M

Eqiliburium law can define a constant

Kc is defined for a reversible reaction at a given temperature as the product of the equilibrium concentrations (in M) of the products, each raised to a power equal to its stoichiometric coefficient in the balanced equation, divided by the product of the equilibrium concentrations (in M) of the reactants, each raised to a power equal to its stoichiometric

coefficient in the balanced equation.

Factors That Affect Chemical Equilibrium

1) concentration 2) pressure

3) volume 4) temperature

5) Catalysts- have no effect on position of equilibrium

Th e C o n c e pt o f E q u i l i b r i u m

Chemical equilibrium occurs when a reaction and its re-

verse reaction proceed at the same rate.

A SYSTEM AT

EQUILIBRIUM

Once equilibrium is achieved, the amount of each reactant and prod-uct remains con-

stant.

THE EQUILIBRIUM CONSTANT

To generalize this expression, consider the reaction.

The equilibrium expression for this reaction would be the LAW of MASS ACTION

E QU ILIB RIU M LAW