CHEM 1B
Dr. R. Rinehart

EXAM 3 Description

REVISED 7/26/09

READ THIS GENERAL STATEMENT CAREFULLY:

Your mission in this course is to obtain for yourself a useful working knowledge and understanding, at an appropriate level, of selected topics in general chemistry, as elaborated in your text and in class. The resources available to you include: the text, lectures and class handouts posted on this site, laboratory exercises, references in print and on the internet, consultation with the instructor outside of class, tutors, study groups, and whatever other legitimate means are necessary. There is no easy path to success. Put the work in. It is particularly important to pay attention to the following: chapter summary, key terms and concepts, and the assigned problems. You will not be able to demonstrate adequate mastery of the material unless you understand the principles involved! Similarly, you will find it pointless to memorize key terms without knowing what they mean and how they can be applied.

“Right, sure, yeah, yeah, yeah – just tell us what’s going to be on the test, doc.”

What? Questions designed to show if you have learned to use these principles and their associated language.

How? Generally by means of objective questions in a variety of formats: fill-ins, short answers, matching, multiple choice, true-false, listing, categorizing, prioritizing, and problem-solving, drawing and/or interpreting diagrams, writing (and sometimes balancing) equations, completing tables, and making rational deductions are all highly probable possibilities.

With that in mind, a brief description of what you can expect follows:

probable exam setup:

Q#	Subjects from Ch 16 & 17 covered [in my own inimitable range of styles]
	vocabulary: this time YOU may have to write the definitions! I define/describe, you give the term
	predicting behavior of acids, bases, and salts
	pH, buffers, titrations, titration curves, indicators
	calculations of pH, pK_a, concentrations of various species, etc. including solubility calculations and some titration calculations
	Did you fill out the pK_a table yet????

PROBLEM PROTOTYPES

1. A weak acid ( or weak base) is found to be ____% dissociated at a pH (pOH) of _____.
Calculate its K_a <or pK_a> (K_b or pK_b)

2. ___ moles of a specified salt [made up of familiar ions, K_a or pK_a (K_b or pK_b) will be given] is dissolved in enough water to make ____ mL of solution. Is the resulting solution acidic or basic?
►Calculate its pH.

3. ___ moles of specified weak acid or weak base [K_a or pK_a (K_b or pK_b) will be given] is dissolved in enough water to make ____ mL of solution.

► Calculate its pH.

4. A buffer solution is made up by dissolving ___ moles of specified weak acid or weak base and ___ moles of its salt [made with a strong acid or base] in enough water to make ____ mL of solution.
[K_a or pK_a (K_b or pK_b) will be given].

►Calculate its pH.

►Calculate its pH after the addition of ____ mL of ____ M [strong acid or strong base] <or after the addition of ___ mol of H₃O⁺ or OH^->

5. An inorganic salt or metal hydroxide [perhaps identified by its name, in which case you will be expected to write its formula] is dissolved in water. Is the resultant solution acidic or basic?

6. A ___ M solution of a weak acid [or weak base] has a pH of _____. Calculate its K_a or pK_a (K_b or pK_b) .

7. Given K_sp data, determine whether a particular cation at specified concentration [normally 0.10M] will precipitate in the presence of an anion, whose concentration you may have to calculate using given K_a and pH data.

Alternatively, concentration of an anion may be given and you will have to determine a pH value that just prevents precipitation. There are lots of variations on the theme, but if you understand K_sp , K_a and pH calculations, you should be able to deal with this.