Chemical Equilibrium

We covered a few of the things in this chapter earlier in the semester: solubility, equilibrium constants, K_w, pH and pOH, and the reversibility of reactions, for example. The major new thing that I want you to learn about is Le Chatelier's principle:

If a stress is applied to a system that is in equilibrium, the system will respond in such a way as to relieve the stress and restore the equilibrium under the new set of conditions.

Concentration: When you add one of the reactants to a system in equilibrium, the reaction shifts to the products.; When you add one of the products, the reaction shifts toward the reactants.

Pressure (or Volume): If you increase the pressure (or decrease the volume), the reaction shifts toward the side with the fewer total number of moles of gas.
: If you decrease the pressure (or increase the volume), the reaction shifts toward the side with the greater number of moles of gas.

Temperature: When you increase the temperature, it's just like adding "heat" as a reactant, the reaction shifts away from the side where the heat is. That is, if it's an endothermic reaction (where heat is a reactant), then the reaction shifts toward the products. In an exothermic reaction, heat is a product, so the reaction would shift back toward the reactants.

Know how to write the equilibrium constant expression for any reaction.

Given the value for [H⁺], {OH^-], pH, or pOH, you should be able to calculate any of the other three values.

Know how to calculate the pH of a solution of a strong acid or strong base, given the concentration (molarity) of the solution.