CHM 2045C Module 8 Assignment Outline

The test outline for Module 8 of Exam #3 includes all of Chapter 5 for the Kotz 6e text. Some of the review from previous chemistry may be found in Chapter 14. Below is a Part by Part test outline with links to sample tests and answers plus text reference sections to study for that objective:

Module Eight: Solutions/Oxidation & Reduction (Chapter 5)

A. _____(03) Solution Properties-From Lecture 5.1 Answers
B. _____(03) Factors Affecting Rate of Dissolving-From Lecture Answers
C. _____(04) Solution Definitions-From Lecture Answers
D. _____(04) Solution Preparation Problems-Section 5.5 Answers
E. _____(04) Solution Dilution Problems-Section 5.8  Answers
F. _____(08) Solution Reaction Problems-Section 5.10 Answers
G. _____(08) Rewrite Equations Ionically –Section 5.2 Answers
H. _____(10) Redox Equations-Sections-Section 5.7  Answers
I.  _____ (03) Solution Discussion Question-Chapter 5 Answers
J.  ____  (03) Writing Ionzation Reactions acids/salts Sect 5.3 Answers
L.  _____(05) pH calculations-Section 5.9 Answers
M. _____(10) Multiple Choice-Solutions/Redox   
______(65) Total = ______%

Part A: Solution Properties

Back in Module 1 in chapter 1 on page 16 a solution was introduced as a homogeneous mixture and you included them in your matter chart for Part A of Module 1.  In Section 5.1 on page 176 a solution is again defined as a homogeneous mixture of two or more substances.  The two new words are introduced, solute and solvent.  From your prior chemistry Parts A & B are review. The text assumes in Chapter 5 that you remember the basics of solution. There is a second chapter on solutions, which is chapter 14. Now for chapter 5 and Module 8 there are six properties of a true solution which is not list in either chapter 5 or 14.  You will write five for :

1.  It is homogeneous mixture of two or more components, solute and solvent

 2.  It has variable composition, that is, the ratio of solute and solvent may be varied.

 3. The dissolved solute is molecular or ionic in size

 4. It may be colored or colorless but it is usually transparent

 5. The solute remains uniformly distributed throughout the solution and will not settle out with time (every drop has exactly the same concentration)

 6. The solute generally can be separated from the solvent by purely physical means (for example evaporation or distillation)

Part B: Factors Affecting Rate of Dissolving  

Part B covers the dissolving process which is not reviewed in Chapter 5. This is reviewed in Sections 14.2 and 14.3 of Chapter 14 on pages 662-666 and 669-672, but the answer to the same test for Partb is a quick summary:

State two factors greatly affecting the solubility of a gas in a liquid:

(1) Temperature (increased temperature of a solvent also generally increases the kinetic energy of the solute  and the gas solute acquire more of a tendency to escape from the solvent. Therefore, Cooling the solvent increased the solubility of a gas in a liquid solvent.)

 (2) Pressure (increasing the pressure (partial pressure) of a gas solute increases the solubility proportionally of that solute in the liquid (Henry’s Law)

What is the main factor affecting the solubility of a liquid in a liquid:

 (3) Nature of the solute and solvent: the like dissolves like rule. The general principle that solubility is greatest when the polarity of the solute is similar to that of the solvent

 State four factors which governs the rate of dissolving a solid in a liquid:

 1.  Particle Size (increased surface area increases rate of solution i.e powders have greater surface area than crystals
                                and will dissolve faster)

 2. Temperature (increased temperature of solvent generally increases rate of solution,  except gases in liquids is opposite)

 3. Concentration of Solution- when the solute and solvent are first mixed the rate of dissolving is at a maximum, as saturation approaches the rate of dissolving slows

 4. Agitation or stirring-the effect of agitation is kinetic which increses the rate of solution.

Part C: Solution Definitions 

One negative for our testbook is that in any chapter they do not have a summary of the key terms introduced in the chapter at the end of the chapter. When you access the index in the back of the text you will find that some of the key terms from the text are defined in the Index, which saves the publisher from having a separate glossary section in the appendices.  The study guide for the text which can per purchased separately does have key terms listing to start the study guide for each chapter.

Part C is labeled Part C and not Part K, because this section is review terms from previous chemistry and not all the terms from the chapter. From the study guide, here are the key terms listed for chapter 5. Those listed in red are the terms you are responsible for in Part C:

Acid,  Acid-base indicator,  Acidic oxide, Base, Basic oxide, Concentration, Electrode, Electrolyte, Equivalence point, Exchange reaction, Molarity, Net ionic equation, Neutralization process, Nonelectrolyte, Oxidation number, Oxidation, Oxidation-reaction reaction (Redox reaction), Oxidizing agent, Precipitate, Precipitation reaction, Primary standard, Product-favored reaction, Reducing Agent, Reduction, Salt, Solute, Solution, Solvent, Spectator ion, Standardization, Strong acid, Srong base, Strong electrolyte, Titration, Volumetric Flask, Weak acid, Weak Base, Weak electroyte.

In Chapter 14 there are 42 key terms which will be covered in CHM 2046C, but the four in red above plus five from Chapter 14 are review. The ones also defined in chapter 14 are: Colloids, Molality, Parts per Million, Saturated Solution, Solubility, Supersaturated solution,  Suspension, Unsaturated solution,  and Weight percent (Percent by Weight).

The other vocabulary words included in Part C which are not in either chapter are: Concentrated Solution, Dilute Solution, and Volume Percent.

Part D: Solution Preparation Problems   

There are three measurements of solutions in preparation problems of which two will be given and the third will  be asked in Part D for preparing a solution in a laboratory. The three are: mass of solute, volume of solution (not volume of solvent-you should know the difference), and the concentration of the solution.

There are six methods of measuring the concentration of a solution: Molarity, Weight Percent, Volume Percent, Molality, Parts Per Million, and Normality.  Section 5.8 of Chapter 5 defines molarity on page 206. Problems for Part D will focus mainly on Molarity, but Weight percent is also fair game. The other four methods of measuring concentration will not be asked in Part D. 

 If the problem states the mass of the solute and the volume of the solution prepared is given, then Molarity is unknown for one problem type. The other common problem is how to make a known volume of a known concentration of a solution and you have to find the mass. The example on page 209 is that type as is Exercise 5.14 on the same page. At the end of the chapter you may work the following problems which are typical for Part D calculations: P 226 #41-50. This should be review from CHM 1025C.

Part E: Solution Dilution/Concentration Problems 

In Section 5.8 of Chapter 5 there is a second type of method for preparing a solution.  On page 205 Diluting a More Concentrated Solution is discussed. On pages 210 and 211 is the discussion. On page 210 is the Problem Solving Tips 5.2. Example 5.10 is shown on page 211. Then Example 5.15 on the same page is a typical Part E Problem. Additional exercises may be worked for Part E at the end of the chapter: page 226 Problems 51-#54.

Part F: Solution Reaction Problems

In Section 5.10 of Chapter 5 pages 214-221 is the discussion of three problem types for Part F: General Solution Stoichiometry, Acid-Base Titration and Redox Titration. You will have one of each of the last two types to calculate in Part F. The solution reaction concept map is shown on Page 215 in Problem-Solving Tip 5.3. Now we need a balanced equation to cross the bridge from one chemical to another, except this time they are in solution and not a mass solid as in Module 5 Part J.

Example 5.14 is an example of the first problem asked in Part F as well as Example 5.15 on page 215. The second problem asked in Part F will be a titration using an Redox reaction. Example 5.16 on page 220 is a sample for the second problem asked in Part F.  In addition to exercise 5.19 on page 276, exercise 5.20 on page 216, Exercise 5.21 on page 220, and Exercise 5.22 on page 221, you should work Problems #61-76 on pages 226-227 to practice Part F.

Part G Rewriting Equations Ionically

Students who have difficulty in writing chemical formulas from names in Module 4 sometimes find Part G difficult. Others just see it as the reverse process and can write the correct charges on the ions anbd know where to split apart the compound when the substance dissolve in water to make a solution of ions.

In Section 5.2 on page 183 is the discussion of Net Ionic Equations.  To do Part H you need to be good at writing equations in aqueous solutions ionically. Problem-Solving Tip 5.1 on page 185 summarizes the process. Example 5.3 on page 184 demonstrates the process step by step. You should work Exercise 5.4 on page 185 plus the end of the chapter exercises #23-26 on pages 224-225.

Part H: Redox Equations

In CHM 1025C an entire chapter is devoted to Oxidation-Reduction Reactions. However, this chapter is skipped by many 1025C instructors such as myself and decided that you will be asked to do this in both CHM 2045C (Chapter 5) and again in CHM 2046C (Chapter 20).  I have advised students going from CHM 1025C to CHM 2045C to keep their 1025 text as it usually has many pages if not a chapter devoted to a topic versus a page or two in a typical college chemistry text such as Kotz.

In Section 5.7 of Chapter 5 Oxidation-Reduction (or REDOX for short) is introduced. There are three methods for solving REDOX balancing. The first is the Oxidation Number Process or Electron Transfer Method. Section 20.1 continues the discussion of Balancing REDOX reactions with the focus on the Ion-Electron Method sometimes called the Half Equation Method. You may use either method to balance the two redox problems presented in Part H.

Electron Transfer Method

In the first method you have to be able to write the oxidation number for each element in a compound. This is explained on page 200 with an example on page 201: Example 5.6.   From the oxidation numbers of the elements, you can determine which elements gain electrons from reactant to product or which lose. Problems #35-36 page 225 will give you Oxidation Number practice, while Problems 37-40 test you strength in recognizing the reactant(s) oxidized and the reactant(s) reduced as well as the oxidizer and the reducer. To balance REDOX by the electron transfer method, you make the electron gain equal to the electron loss by applying the proper coefficients then balance the remaining compounds by inspection. You may research the Internet for step by step balancing Redox by Electron Transfer. A good web site is:
http://members.aol.com/profchm/redox.html

George Bodner of Purdue University is one of the leading chemical educators in the country.  He has a very complex web site as well as being an author of many chemistry book including General Chemistry. He has two good web pages for oxidation-reduction. The first is the general discussion of oxidation-reduction reactions: http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch19/oxred_1.php

Ion-Electron Method

In the second method, Ion-Electron Method,  you do not need to know the concept of oxidation numbers, but MUST be able to split compounds into their correct ions with their correct charges. In this method you balance the elements first step by step, then balance the electron last. It is a longer process, but I think it is easier. The Method is subdivided into reactions which are Acidic, Basic or Neutral. For Part H you will balance one REDOX reaction by either method which will be in Acidic Solution and the other will be in a Basic Solution.

Our textbook demonstrates the Ion-Electron Method in section 20.1 on pages 947-948.  Example 20.1 shows the general method of Ion-Electron. Example 20.2 on page 948 demonstrates an example in Acidic Solution.  Example 20.3 shows the step-by-step method in basic Solution on pages 951-952.  Try Exercise 20.1  page 948,  Exercise 20.2 and 20.3 page 950, and Exercise 20.4 Page 952. 

George Bodner's REDOX site gives you eight practice problems with the step by step Ion-Electron Method: http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch19/oxred_2.php

My web site also give a long discussion step by step to Balance REDOX: 
http://www.hccbrandon.net/chem1211/redox/redoxOH.htm

Try the following Acidic Media equations for practice:

Acid Media Homework:

Zn      +       NO3 1-   +     H 1+      à   Zn 2+    +   NH4 1+     +    H2O

MnO4 1-   +   C2O4 2-  +   H 1+      à   Mn 2+   +   CO2         +    H2O

Cr2O7 2-   +   C2H5OH  +   H 1+   à   Cr 3+   +   HC2H3O 2     +    H2O

SO4 2-     +     CH2O     +   H 1+     à   H2S     +   CO2         +    H2O

FeS   +       NO3 1-   +     H 1+        à   NO   +   Fe 2+    +   SO4 2-     +    H2O

Cr2O7 2-   +   Cl 1-   +     H 1+        à   Cr 3+   +   Cl2     +    H2O

H2O2   +   MnO4 1-   +     H 1+        à   Mn 2+   +   O2         +    H2O

Try the following Basic Media equations for practice:

Basic Media Homework:

Cr 3+         +       ClO3 1-   +     OH 1-      à   CrO4 2-  +   Cl 1-     +    H2O

Mn2-        +        Br2          +   OH 1-      à    MnO2   +   Br 1-     +    H2O

Fe(OH)2    +       O2         +    H2O         à   Fe 3+       +   OH 1-     

Zn              +     NO3 1-     +    OH 1-      à    ZnO2 2-  +     NH3     +   H2O

AsO2 1-       +    ClO 1-      à    AsO3 1-   +    Cl 1-     (basic solution)

MnO4 1-     +     C2O4 2-    +    OH 1-     +  H2O   à     MnO2    +    CO3 2- 

N2H4         +    O2           à     N2          +   H2O2      (basic solution)

 Try problems #1-#6 on page 990 or our text for more practice at balancing REDOX equations.

Those reactnt(s) that lose electrons determines the Oxidation part of the reaction and the reactant that under goes oxidation is called the Reducing Agent. Purdue's web site discusses these labels:
http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch19/oxred_3.php  

Part I: Solution Discussion Questions      

The following are discussion questions which deal with basic definitions introduced in Chapter 5:

(1) Define oxidation and reduction in terms of electron transfer.
(2) In an oxidation reduction equation, what is the oxidizing agent?
    What is the reducing agent?
(3)  How can you recognize whether a reaction is a redox reaction or not?
(4)  Name three types of reactions which are NOT oxidation reduction and give at least one example
(5) What is the equivalence point in a titration of an acid and a base?
Is there a difference between the equivalence point and the end point of the titration when using an acid/base indicator to determine the end point?

The answers are posted on the grading outline web site and have been included in the sample test answer handout.

Part J: Writing Ionization Reactions 

In section 5.1 of Chapter 5 the is a discussion of the solubility of compounds in water which produce ionic solutions. Stong Acids, Strong Bases, and Soluble Salts are show as a single direction arrow, while Weak Acids, Weak bases, and Insoluble salts have a double arrow for a reversible reaction.

Examples are show on page 177, 178, 186, and 188.

Part L:   pH Scale Calculations  

Section 5.9 of Chapter 5 demonstrates the concept of pH. Equations 5.2 and 5.3 show how to make the calculations in Part L. Example 5.11 shows how to calculate pH from the concentration of the acid or basic solutions. You are expected to know these two formulas for the calculations in Part L. Exercise 5.17 page 214 plus the problems at the end of the chapter #55-#60 on page 226 are additional examples for your practice.