Chemical Equilibrium

In the previous blogpost, we have discussed on the concepts of chemical equilibrium in a reversible reaction.

We have also discussed on the formula to determine Equilibrium Constant, K_c and K_p.

For Reversible Reactions involving Gases, we should use the following formula:

Equilibrium constant, K_p = (P_C)^c (P_D)^d / (P_A)^a (P_B)^b

Let’s apply the formula to a question that was given by my students from a local Junior College (JC).

Now, at equilibrium, reactant (X) and products (Y and Z) will be all present together.

Since the question stated that the pressure is constant (value is P) and the temperature is also constant, we can assume that the total pressure, P_T of the gases at equIlibrium is P.

By stoichiometry ratio comparison of equation

X <=> Y + Z;

Since Mole of Y = Mole of Z at equilibrium, therefore

Partial Pressure of Y, P_Y = Partial Pressure of Z, P_Z

Since equilibrium partial pressure of X, P_X is 1/7 P, it means that the other 6/7 P of pressure must be shared equally among Y and Z.

Thus,… Continue reading ...

A reversible reaction is one in which can proceed in both directions i.e. forward and reverse reactions.

The reactants are not completely converted to products. Instead, an intermediate position or EQUILIBRIUM is reached whereby both reactants and products are present.

This also means that reversible reactions are never complete, a mixture of reactants and products is obtained.

At equilibrium in a reversible reaction:

1. Rate of forward reaction = Rate of reverse reaction

2. Concentration of the reactants and the products are unchanged

It is important to know what is the EQUILIBRIUM CONSTANT, which is defined as the measure of the extent to which the reaction are coverted into products before equilibrium is reached.

Consider the equilibrium, aA + bB <=> cC + dD
Equilibrium constant, K_c = [C]^c[D]^d / [A]^a[B]^b and is a constant at a given temperature

For reactions involving gases, the equilibrium constant can be represented in terms of the partial pressure, P, of the gases and is give by the symbol, K_p.

Consider the equilibrium, aA (g) + bB (g) <=> cC (g) + dD (g)
Equilibrium constant, K_p = (P_C)^c

Chemical Equilibrium: Question on Equilibrium Constant, Kp

Chemical Equilibrium: Reversible Reaction Introduction