Chemical Systems and

Equilibrium- Equilibrium Constant -

1

Please READ pp. 439 – 440

Equilibrium constant (Keq) is the value obtained from the mathematical combination of equilibrium concentrations using the equilibrium law expression.

 

2

Equilibrium Law in Chemical Reactions

For the general chemical reaction 

aA + bB cC + dD

Keq = [C]c[D]d

                             [A]a[B]b

where A, B, C, and D are chemical entities in gas or aqueous phases

a, b, c, and d are the coefficients in the balanced chemical equation, and

Keq is the constant called the equilibrium constant

3

The molar concentration of the products are always multiplied by one another and written in the numerator, and the molar concentrations of the reactants are always multiplied by one another and written in the denominator.

The coefficients in the balanced chemical equation are equal to the exponents of the equilibrium law expression

The concentrations in the equilibrium law expression are the molar concentrations of the entities at equilibrium

4

Stating the obvious…

(1) Ratio of products to reactants at a specific temperature

5

The Magnitude of Keq

What does it tell us???

(2) If Keq is huge, then products are greatly favoured and the equilibrium lies to the right (Percent Reaction is above 50)

6

The Magnitude of Keq

What does it tell us???

(3) If Keq is very small, then the reactants are greatly favoured and the equilibrium lies to the left. (Percent Reaction is below 50)

7

The Magnitude of Keq

What does it tell us???

(4) If Keq is around 1, then the product and reactant concentrations are comparable.

8

The Magnitude of Keq

What does it tell us???

p. 442 PracticeUC # 1p. 444 PracticeUC # 2, 3, 4p. 445 PracticeUC # 5, 6 Read and summarize p. 445 - 446 – Limitations

of Equilibrium Constants and Percent Reaction Values AND Heterogeneous Equilibria

Learning Checkpoint

9

Word, to your mother!