To quote from Silberberg: "Few quantitative ideas are more central to your understanding of chemistry than the mole and its relation to the amounts of substances on the macroscopic and molecular levels...
Chapter 3 Outline
3.1 The Mole
3.2 Determining the Formula of an Unknown Compound
3.3 Writing and Balancing Chemical Equations
Breakdown, Brief Discussion & Help With Sample Problems: What You Should Know
The arithmetic component of CHEM 200 becomes apparent in this section, and much of that arithmetic revolves around the concept of the mole. To quote Silberberg: "The mole, like the dozen, represents a certain number of objects." Specifically, a mole of a substance contains the number of entities equal to the number of atoms in exactly 12 grams of carbon-12. That number is 6.02 x 10 exp23 (ten to the twenty-third power)...a number that is referred to as Avogadro's number.
Of equal importance is the fact that the atomic mass of an element expressed in amu (i.e. the numbers on the period chart) is numerically the same as one mole of atoms of the element expressed as grams.
In other words, one atom of sulfur has a mass of 32.07 amu...and one mole of sulfur atoms has a mass of 32.07 grams. Time and time again throughout the rest of CHEM 200, the numerical data on the periodic chart will be utilized in efforts to determine the number of moles of an element and/or compound...since the above bold-faced statement applies to compounds as well as to elements.
All of which leads up to the concept of molar mass (M), which is the mass of one mole of entities of the substance and has units of grams per mole (g/mol).
All of these concepts, as well as mass percent, are tied together in the sample problems in this section...some of which are discussed in the links below.
click here for a few words about SAMPLE PROBLEM 3.1 (page 89)
click here for a few words about SAMPLE PROBLEM 3.2 (page 89)
click here for a few words about SAMPLE PROBLEM 3.3 (page 91)
click here for a few words about SAMPLE PROBLEM 3.4 (page 92)
3.2 Determining the Formula of an Unknown Compound
The concepts of empirical and molecular formulas were introduced in Chapter 2...and sample problems that illustrate calculations involving these terms are contained in sample problems 3.5 and 3.6.
click here for a few words about SAMPLE PROBLEM 3.5 (page 94)
click here for a few words about SAMPLE PROBLEM 3.6 (page 95)
3.3 Writing and Balancing Chemical Equations
...is all about balancing chemical equations. The five "rules" for balancing equations are listed on pages 101 and 102. Sample problem 3.8 requires knowledge of these rules in order to balance a chemical equation.
click here for a few words about SAMPLE PROBLEM 3.8 (pages 102-103)
3.4 Calculating the Amounts of Reactant and Product
...this section is extremely important for all CHEM 200 students, but especially important for students who, for one reason or another, have had difficulty with previous chemistry courses (at SIU and elsewhere). In a word, CHEM 200 is all about problems.
Here's an illustration of what this section is all about.
Suppose you have a balanced chemical equation such as (1) below:
(1) 3A ---> 2B + 5CIf you are given a flask with X grams of A, and you have access to a periodic chart, it is possible to determine how many grams of B, and how many grams of C, form in the reaction.
The process is simple...and the transformation of grams of A to moles of A to moles of B (or C) to grams of B (or C)...is perfectly illustrated in the right-hand margin of page 107 (which applies to Sample Problem 3.9).
click here for a few words about SAMPLE PROBLEM 3.9 (page 105-107)
Also discussed in this section is the concept of limiting reagents...Sample Problem 3.11 nicely illustrates the necessary concepts pertaining to limiting reagents. This is an important aspect of CHEM 200.
click here for a few words about SAMPLE PROBLEM 3.11 (page 110-111)
Finally, the terms theoretical yield and percent yield are introduced in the latter part of 3.4. Sample Problem 3.12 involves calculating percent yield.
click here for a few words about SAMPLE PROBLEM 3.12 (page 112-113)
3.5 Fundamentals of Solution
Stoichiometry
...and once again, this section is also extremely important for CHEM 200 students, because of the important fundamental concepts that are discussed within it--solute, solvent, concentration, and molarity.
Implicit in these concepts are terms such as mass, volume, dilution, and molar mass.
All CHEM 200 students should be comfortable working the sample problems within this section. The links below contain audio tips for several of them...
click here for a few words about SAMPLE PROBLEM 3.14 (page 115)
click here for a few words about SAMPLE PROBLEM 3.15 (page 117)
click here for a few words about SAMPLE PROBLEM 3.17 (page 119)
exercises such as numbers 3.19, 3.37, 3.47, 3.57, and 3.89 are all straightforward problems of the type that are often found on CHEM 200 exams