Unit 4

There are two topics in Unit 4 : Chemical Equilibrium and Acids and Bases.

Most of the chemical reactions we have studied so far in this course have been one way reactions, where a reactant or reactants undergo chemical change to produce a product or products.  The reaction proceeds in the “forward” direction from reactants to products.  In equilibrium reactions, both the forward and reverse (products back to reactants) occur at the same rate.  You will learn about characteristics of equilibrium reactions, how to tell is a reaction is at equilibrium, how an equilibrium reaction will proceed under various conditions, and equilibrium calculations.

The second topic of Unit 4 is acids and bases. You had a brief introduction to acids and bases in Unit 2 — we will now look at them in more detail.

Unit 4 Learning Objectives

Chemical Equilibrium

  1. Given the balanced equation of a reversible reaction, write the equilibrium constant expression.
  2. Relate equilibrium constant magnitude to the position of the equilibrium and the relative equilibrium concentrations of reactants and products.
  3. Given the equilibrium constant for one reaction, determine the value of the equilibrium constant for a related reaction.
  4. Write an equilibrium expression for reactions involving a solid or a liquid.
  5. Calculate Kc or Kp from each of the following:
    1. Equilibrium concentrations or partial pressure of all species.
    2. Initial concentrations and one equilibrium concentration.
  6. Given the concentrations of all recating species, calculate the reaction quotient, Q, and predict the direction of reaction.
  7. Use the equilibrium constant to calculate equilibrium concentrations.
  8. Based on LeChatelier’s principle explain how relative equilibrium quantities of reactants and products are shifted by changes to the equilibrium conditions.

Acids and Bases

  1. List some general properties of acids and bases.
  2. Given the chemical formula of any acid or base in the “Formula & Nomenclature” handout, give the name and vice versa.
  3. Given an acid/base reaction, identify the Bronsted, Arrhenius and Lewis acids or bases present.
  4. Given an acid or base, write the conjugate base or acid.
  5. Describe the autoionization of water and write and apply the Kw expression.
  6. Calculate [H+], pH and/or [OH-], pOH given the value of any one of the variables or the concentration of a strong acid or base.
  7. Calculate all equilibrium concentrations and pH or pOH in a solution of a weak acid or base given the Ka or Kb or vice versa.
  8. Calculate percent ionization of an acid or base from initial concentrations and Ka or Kb values.
  9. Explain the relationship between the strength of an acid and the strength of its conjugate base.
  10. Write the equations for the dissociation of weak acids and weak bases and/or Ka and Kb expressions.
  11. Calculate all equilibrium concentrations and pH or pOH in a solution of a weak acid or base given the Ka or Kb or vice versa.
  12. Calculate percent ionization of an acid or base from initial concentrations and Ka or Kb values.
  13. Use pKa or pKb to predict the relative acid base strengths.
  14. Interconvert between the Ka of an acid and the Kb of its conjugate base.
  15. Write simple acid-base reactions for:
    1. a. Ionization of a weak acids
    2.  b. Dissociation of strong acids
    3. c. The addition of a strong acid/base to a weak base/acid
    4. d. the dissociation of salts in water
    5. e. Lewis acid-base reactions
  16. Recognize the common strong acids: HCl(aq), HBr(aq), HI(aq), HNO3, H2SO4, HCl103 and HClO4.
  17. Calculate the Ka/Kb for weak acid/base given the pH of a solution of known concentration.
  18. Using a balanced chemical equation for both the cation and anion, predict whether a salt solution will be acidic, basic, or neutral.
  19. Calculate the pH of salt solutions.
  20. Use knowledge of chemical structure to predict relative acid-base strength.

Unit 4 Topics

Study these in order:

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