Chemical Systems and Equilibrium

1. Chemical Systems and Equilibrium - Equilibrium Constant -

2. Equilibrium Law in Chemical Reactions • Please READ pp. 439 – 440 • Equilibrium constant (Keq) is the value obtained from the mathematical combination of equilibrium concentrations using the equilibrium law expression.

3. For the general chemical reaction aA + bBcC+ 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

4. Stating the obvious… • 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

5. The Magnitude of KeqWhat does it tell us??? (1) Ratio of products to reactants at a specific temperature

6. The Magnitude of KeqWhat 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)

7. The Magnitude of KeqWhat 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)

8. The Magnitude of KeqWhat does it tell us??? (4) If Keq is around 1, then the product and reactant concentrations are comparable.

9. Learning Checkpoint Word, to your mother! p. 442 Practice UC # 1 p. 444 Practice UC # 2, 3, 4 p. 445 Practice UC # 5, 6 • Read and summarize p. 445 - 446 – Limitations of Equilibrium Constants and Percent Reaction Values AND Heterogeneous Equilibria