Unit 1

Our first unit will go into more depth on one of your topics from late in the semester of CHEM 151, acid-base chemistry.  The specific topics covered will be the common ion effect in acids and bases, buffer solutions, and acid-base titrations (don’t worry if these terms don’t mean anything to you yet).

In order to understand these topics, it is necessary to have a good grasp and recall of concepts and problem solving skills of the CHEM 151 acid-base material, so we will start with a review of that (if you complete the review in a week, you’ll be on track).

After completing the review and the new material on acids and bases, we will end the unit by taking principles you learned in CHEM 151 about equilibrium reactions and constants and applying it to slightly soluble and insoluble salts (remember those from solubility rules?) in a discussion of solubility equilibria.

Unit 1 Learning Objectives

Purpose of the Learning Objectives:

This is the list of learning objectives for Unit 1 from the course syllabus.  I know, it is long.  I don’t expect you to read it now before studying.  So how should you use it? Think of it as:

  1. An outline of the course and the material you will be studying in Unit 1 (and tested on the Unit 1 Exam).
  2. A list of things you should be able to do to demonstrate to me (and more importantly, yourself) that you have a good grasp of these concepts and skills in chemistry.  This will serve as a good review checklist – as you study for Exam 1, it’s worth giving these items a look to see if you can do them – if you can, you are likely well prepared.  If you can’t, that’s where you should focus your study and get help if needed.

Review Objectives from CHEM 151:

After having reviewed, students should be able to:

  1. Write the equation for an acid/base reaction (either ionization or neutralization) identifying the Brønsted – Lowry acids or bases present.
  2. Given an acid or base, write the conjugate base or acid.
  3. Explain the relationship between the strength of an acid and the strength of its conjugate base.
  4. Recognize the common strong acids“:  HCl(aq), HBr(aq), HI(aq), HNO3, H 2SO4, HClO3, and HClO4.
  5. Recognize the common strong bases:  Group IA metal hydroxides, Ca(OH)2 and Ba(OH)2.
  6. Calculate [H+], pH,  [OH–], and/or 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
  8. Calculate the Ka/Kb for a weak acid/base given the pH of a solution of known concentration.
  9. Calculate percent ionization of an acid or base from initial concentrations and Ka or Kb values or vice-versa.
  10. Interconvert between the Ka of an acid and the Kb of its conjugate base.
  11. Write the balanced chemical equations for hydrolysis of a salt then predict whether the salt solution will be acidic, basic or neutral.
  12. Calculate the pH of salt solutions.

Aspects of Aqueous Equilibria:

After having completed this unit, students should be able to:

  1. Define common ion effect and explain how it affects an acid/base or solubility equilibrium.
  2. Define, explain, and be able to identify buffer solutions.
  3. Explain how buffer solutions are prepared and calculate the amount of the components required to prepare a buffer given pH.
  4. Using chemical equations, describe how a buffer solution can resist a change in pH when a small amount of H+ (from strong acid) or OH– (from strong base) is added.
  5. Calculate the pH of a buffer solution starting with an initial concentration of the buffer components and Ka or using the Henderson-Hasselbalch equation using the pKa and the initial buffer component concentrations.
  6. Calculate the change in pH of a buffer solution of known composition caused by adding a small amount of strong acid (H+) or strong base (OH–).
  7. Define buffering capacity and given a choice of buffers select which one has a higher buffering capacity.
  8. Define titration, titration curve, indicator, end-point, equivalence point and mid point (half-equivalence point).
  9. Sketch a titration curve and identify various points on the curve.
  10. Calculate the pH at various points along a titration curve for a strong acid with a strong base, strong base with a strong acid, weak acid with strong base or weak base with strong acid given the volume of the titrant and the concentration of the components.
  11. Calculate the Ka for a weak acid  or Kb for a weak base from titration curve data.
  12. Select the proper indicator for an acid-base titration.
  13. Distinguish between solubility and solubility product constant.
  14. Write the dissociation equation and the Ksp expression for a salt given its name or chemical formula.
  15. Calculate the Ksp given the solubility of a partially soluble salt or the solubility given Ksp.
  16. Explain, using equations, the effect of a common ion on the solubility of a salt.
  17. Calculate the solubility of a salt in the presence of a common ion.
  18. Write the equations for the reaction that occurs to increase the solubility when an acid is added to a salt then predict whether its solubility depends on pH and calculate the molar solubility of a salt at a given pH.
  19. Predict whether a precipitate will form when two solutions of known concentration of ions are mixed.
  20. Predict when ions are added to a solution containing a mixture of several ions, the minimum concentration of the added ion that will cause precipitation and what salt will precipitate.

Unit 1 Topics

Study these in order:

Unit 1 Online Homework

Online homework problems for Unit 1 are posted at the online homework  website. You can access all the homework problems for the semester using the menu at the top of the page or on the right sidebar on that website.  Also, links for each homework assignment will be provided in the course material for each topic.  Here is a link to the homework for the first course topic – CHEM 151 Acid Base review. These homework problems are designed to help you learn the course material and practice problem solving skills.  They allow unlimited attempts and are ungraded.

Additionally, there are supplemental graded homework questions available on D2L.  These supplemental questions will make up the 100 point homework grade for the semester  (11 assignments at 10 points each with the lowest being dropped). 13 points will be available for each assignment, with any points earned over 10 for each assignment being bonus points or extra credit.  The supplemental homework questions can be accessed on D2L by clicking the “assessments” tab in the top menu then clicking “quizzes”.  They will have due dates throughout the semester, with each due date available on the course schedule.  These questions will be graded and you will be given two tries for each one (many are multiple choice).  They will be much easier to answer if you complete and understand the ungraded problems on the website first (and for many of them it is necessary to complete the problems on the website first).

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