CHM 1025C Module 8 Assignment Outline

The test outline for Module 8 of Exam #3 includes all of Chapter 14 for the Corwin 4th Edition text. Writing Equations ionically is covered in Chapter 15, section 15.11. pH is covered in Chapter 15. Redox is also covered in Chapter 17 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 (Chapter 14 & 17 )

A. _____(10) Solution Properties-From Lecture

B. _____(10) Factors Affecting Rate of Dissolving-Sec 14.1, 14.2, 14.5, 14.6  & From Lecture

C. _____(10) Solution Definitions-Sect 14.7, 14.8, 14.9 & From Lecture

D. _____(10) Solution Preparation Problems-Section 14.7, 14.8, 14.9

E. _____(10) Solution Dilution Problems-Section Sect 14.10

F. _____(20) Solution Reaction Problems-Section 14.11

G. _____(30) Rewrite Equations Ionically –Section 15.11

H. _____(30) Redox Equations-Sections-Section 17.2—17.5

L.  _____(10) pH calculations-Section 15.8, 15.9

M. _____(25) Multiple Choice-Solutions/Redox Chap 14, 17

______(115) Total = ______% Chapter 14 & 17

Part A: Solution Properties

Back in Module 1 a solution was introduced as a homogeneous mixture of a solute and solvent and you included them in your matter chart for Part A of Module 1.  In Section 14.1 on page 386 a solution is defined as a homogeneous mixture of two or more substances.  The two new words are introduced, solute and solvent, is defined in section 14.2.  Sections 14.1-14.5 cover Parts A & B. In  chapter 14 and Module 8 we start with six properties of a true solution which are not listed in chapter  14 as a separate list.  You will write five of these six properties for Part A:

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. In Section 14.1 of Chapter 14 on pages 387-388 there is a discussion of solubility and temperature plus solubility and pressure. The following answers the first question:

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)

In section 14.2 the properties of liquids dissolved in liquids focus on the main property which is polarity. Now is the time to review polar covalent bonds section 12.6.  Polar covalent bonds depend on the electronegativities of the two elements. If two elements differ in electronegativity between 0.4 and 1.7, then polar covalent bonds are formed. If the difference between the two atoms is greater than 1.7 then ionization takes place. A solution containing ions must be dissolved by polar molecules as a solvent. Next you must understand the three dimensional geometry of the molecules to determine if a molecule is polar. Molecules with polar covalent bonds the dipoles, which are vectors, created by the polar covalent bonds, are summed. If there is a net moment of force the molecule is polar. However, it is possible for a compound to have polar covalent bonds and be nonpolar when the net summation of the vectors total zero . At the end of Chapter 12, section 12.10 this is explained.

In section 14.2, the “Like Dissolves Like Rule” depends on the polarity of the molecules of the solute and the solvent. 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  In Section 14.4 the discussion of the dissolving leads to Section 14.5 the rate of dissolving, which is the next question in Section B of Module 8.

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 increases the rate of solution.

From the textbook:  Part C: Writing Ionization Reactions

In section 8.9 of Chapter 8 the is a discussion of the solubility of compounds in water which produce ionic solutions. Strong 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.

From the textbook:  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 (Mass) Percent, Volume Percent, Molality, Parts Per Million, and Normality.  Section 14.9 of Chapter 14 defines molarity on page 401. 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. Example 14.9 on page 402 is that type as is Exercise 14.10 on the same page. At the end of the chapter you may work the following problems which are typical for Part D calculations: P 411-2 #43-52 involve mass percent, while #53-64 involve Molarity.   Part E: Solution Dilution/Concentration Problems

In Section 14.10 of Chapter 14 there is a second type of method for preparing a solution.  On page 404 Dilution of a Solution is discussed. On page 405 is Example 14.11 of diluting a more concentrated solution.  At the end of the chapter are two additional exercises #65 and #66 on page 412. Part F: Solution Reaction Problems    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 can not see it as the reverse process and can not write the correct charges on the ions or even know where to split apart the compound when the substance dissolve in water to make a solution of ions.

In Section 15.11 on page 438 is the discussion of Net Ionic Equations.  To do Part H, REOX Equations,  you need to be good at writing equations in aqueous solutions ionically.  Problem-Solving on page 439 summarizes the process. Example Exercise 15.15 on page 439 and Exercise 15.16 on page 440 demonstrate the process step by step. You should work the Practice Exercise on page 441 plus the end of the chapter exercises #73-78 on page 447.  The following Rules are written at the top of the Part G test:

Show as ions: soluble salts (aq) and strong acids (aq); leave as molecules/formula units insoluble salts (s), weak acids (aq), covalent molecules. (Strong hydroxide bases are hydroxides which are also soluble salts are written ionically.)

Strong Acids are: Perchloric Acid; Hydrochloric Acid; Nitric Acid; Sulfuric Acid; Hydrobromic Acid; Hydroiodic Acid.

Strong Bases are: Sodium hydroxide, Potassium hydroxide, Calcium hydroxide, Barium hydroxide, Strontium hydroxide

Here are a set of worked examples:

1.    KOH (aq)         +        HNO3(aq)     à          KNO3(aq)         +          HOH(l)

Decide which compounds should be split into ions:

K|OH (aq)       +      H|NO3(aq)   à       K|NO3(aq)      +       HOH(l)

Strong base            strong acid           soluble salt       covalent molecule

Rewrite the ionic species as ions, and leave the rest as compound formulas:

K1+(aq)+OH1-(aq)+H1+(aq)+NO31-(aq)àK1+(aq)+NO31-(aq)+HOH(l)

Cancel the Spectator Ions:

K1+(aq)+OH1-(aq)+H1+(aq)+NO31-(aq)àK1+(aq)+NO31-(aq)+HOH(l)

1.    KOH (aq)         +        HNO3(aq)     à          KNO3(aq)         +          HOH(l)

OH 1-(aq)             +        H 1+(aq)             à           HOH (l)

------------------------------------------------------------------------------

2.     CuSO4 (aq)     +      Na2CO3 (aq)   à     CuCO3  (s)          +      Na2SO4 (aq)

Decide which compounds should be split into ions:

Cu|SO4 (aq)     +    Na2|CO3 (aq)   à   CuCO3 (s)    +    Na2|SO4 (aq)

Soluble Salt            Soluble Salt        Insoluble salt        Soluble Salt

Rewrite the ionic species as ions, and leave the rest as compound formulas

Cu2+(aq)+SO42-(aq)+2Na1+(aq)+CO32-(aq)à

CuCO3(s) + 2Na1+(aq)+SO42-(aq)

Cancel the Spectator Ions:

Cu2+(aq)+SO42-(aq)+2Na1+(aq)+CO32-(aq)à

CuCO3(s) + 2Na1+(aq)+SO42-(aq)

2.     CuSO4 (aq)     +      Na2CO3 (aq)   à     CuCO3  (s)          +      Na2SO4 (aq)

Cu 2+            +         CO3 2-         à       CuCO3   (s)

--------------------------------------------------------------------------------------------

3.   NaOH (aq)    +   NH4NO3 (aq)   à   NaNO3 (aq)    +    NH3 (g)    +   HOH (l)

Decide which compounds should be split into ions:

Na|OH (aq)   +   NH4|NO3 (aq)   à   Na|NO3 (aq)    +  NH3 (g)    +   HOH (l)

Strong Base       Soluble Salt          Soluble Salt       molecular   molecular

Rewrite the ionic species as ions, and leave the rest as compound formulas:

Na1+(aq)+OH1-(aq)+NH41+(aq)+NO31-(aq)à

Na1+(aq)+NO31-(aq) + NH3 (g)+HOH(l)

Cancel the Spectator Ions:

Na1+(aq)+OH1-(aq)+NH41+(aq)+NO31-(aq)à

Na1+(aq)+NO31-(aq) + NH3 (g)+HOH(l)

3.    NaOH (aq)    +   NH4NO3 (aq)   à   NaNO3 (aq)    +    NH3 (g)   +   HOH (l)

OH 1-       +        NH4 1+      à    NH3 (g)   +  H2O (l)

------------------------------------------------------------------------------------------

4.    BaBr2 (aq)   +   ZnSO4 (aq)        à     BaSO4 (s)        +      ZnBr2   (aq)

Decide which compounds should be split into ions:

Ba|Br2 (aq)   +   Zn|SO4 (aq)        à   BaSO4 (s)    +    Zn|Br2   (aq)

Soluble Salt      Soluble Salt         Insoluble salt        Soluble Salt

Rewrite the ionic species as ions, and leave the rest as compound formulas

Ba2+(aq)+ 2Br1-(aq) + Zn2+(aq) + SO42-(aq)à

BaSO4(s) + Zn2+aq) + 2Br1-(aq)

Cancel the Spectator Ions:

Ba2+(aq) + 2Br1-(aq) + Zn2+(aq) + SO42-(aq)à

BaSO4(s) + Zn2+(aq) + 2Br1-(aq)

4.    BaBr2 (aq)   +   ZnSO4 (aq)        à     BaSO4 (s)        +      ZnBr2   (aq)

Ba 2+         +       SO4 2-          à       BaSO4 (s)

---------------------------------------------------------------------

5.    Cr(OH)2 (s)   +   HCl   (aq)      à    First Complete the Product:

Cr(OH)2 (s)   +   2HCl   (aq)      à  CrCl2 (aq)    +  HOH (l)

Decide which compounds should be split into ions:

Cr(OH)2 (s)   +  2 H|Cl   (aq)      à      Cr|Cl2 (aq)    +  HOH (l)

Insoluble Salt   Strong Acid            Soluble Salt     Molecular

Rewrite the ionic species as ions, and leave the rest as compound formulas:

Cr(OH)2 (s) +2H1+(aq) + 2Cl1-(aq)àCr2+(aq)+ 2Cl1-(aq) + HOH(l)

Cancel the Spectator Ions:

Cr(OH)2 (s)+ 2H1+(aq)+ 2Cl1-(aq)à Cr2+(aq)+ 2Cl1-(aq) + HOH(l)

5.    Cr(OH)2 (s)   +  2 HCl   (aq)      à      CrCl2  (aq)        +  H2O (l)

Cr(OH)2 (s)   +  2 H 1+ (aq)      à    Cr 2+ (aq)  +  2 H2O (l)

From the Textbook:    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 Oxudation 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 coefficents then balance the remaining compounds by inspection. You may research the Internet ofr 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-reducation 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 demoinstrates 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 gves you eight practice problems with the step by step Ion-Electron Method:

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)

Bi2O3     +     OCl 1-    +    OH 1-     à     BiO3 1-   +    Cl 1-  +  H2O

BH41-  +  ClO31-  à H2BO31- + Cl1-    (basic solution)

Fe(OH)2      +     Pb(OH)31-      à  Fe(OH)3  +  Pb   (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:

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 K: Solution Definitions

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.  Instead twenty Key Terms are defined in the Matching Section of Chapter 14 page 409.

Part C is labeled Part C instead of Part K, because I never changed the numbering many years ago when I made Key terms Part K of every chapter. Also the terms cover three chapters instead of one.

Chapter 14 terms are: Colloid, dipole, Henry’s Law, immiscible, Like Dissolves Like, mass/mass percent, miscible, molarity, net dipole, nonpolar solvent, polar solvent, saturated solution, solubility, solute, solvent, solvent cage, supersaturated solution, Tyndall effect, unsaturated solution.

Some additional words for solutions: Molality, Parts per Million, Suspension,.

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

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.  pH + pOH = 14 at Room Temperature and one atmospheres pressure  