(1)

At equilibrium, the rates of the forward and reverse reactions are equal.

ratef = rater

ratef = K1 [A] [B]

rater = K2 [C] [D]

K1 [A] [B] = K2 [C] [D]

K1

[C] [D]

---- = --------

K2

[A] [B]

K1

---- = Keg

K2

(2) Simply, the ionization (equilibrium) constant is equal to the product of the

mol/L concentrations of the products formed in the reaction divided by the product of the

concentrations of the reactants.

(3)

Kb.

(4) Ka and Kb are determined for weak acids and bases only. If the Ka or Kb

of a strong acid or base, respectively, were determined it would be an infinitely large

number.

(5)

Values of equilibrium constants are interpreted as follows:

(a) The constant indicates the strength of a weak electrolyte.

(b) The smaller the value of the Ka or Kb, the weaker the acid or base

respectively.

+

What is the [H ] of a 0.100 mol/L solution of acetic acid if the Ka for HC2H3O2 is

1.75 X 10-5?

Solution. Determine the equation for the dissociation of the weak acid.

HC2H3O2 <====> H+ + C2H3O2-

MD0837

9-6