CHM 1025C Module Five Assignment Outline

The test outline for Module 5 of Exam #3 includes Chapters 8, 9 and 10, 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 Five Part I:Chemical Equations & Stoichiometry (Chap 8, 9, 10)

A._____(05) Molecular Mass Calculation-Section 9.3 Answers a

B._____(05) Mole Calculations-Sections 9.2, 9.4 Answers bcd

C._____(05) Percentage Composition Calculation-Section 9.7 Answers bcd

D._____(05) Empirical Formula Calc. from % Comp-Section 9.8 Answers bcd

E._____(05) Basic Stoichiometric Definitions-Chapter 8, 9,& 10 Answers ef

F._____(20) Balancing Chemical Equations -Sections 8.2-8.3 Answers ef

G._____(05) Predicting Single Replacement Products . Sections 8.7-8.8 Answers

H._____(10) Predict Double Replacement & Neutralization Reactions

                                                                                             Sections 8.10 & 8.11 Answers h

I.______(10) Mole-Mole Problems Sections 10.1-10.2 Answers ij

J._____ (10) Mass-Mass Stoichiometric Problems-Sections 10.3 & 10.4 Answers ij

K._____(10) Excess/Limiting Reagent Problems-Section 10.7-10.8 Answers kl

L._____ (05) Per Cent Yield Problems/Impure Reagents-Section 10.9

M._____(25) Multiple Choice Chapters 8, 9, & 10 (answers at bottom)

______(115) Total = ______%

Hardcopy of the lecture notes from Chapter 4 of another textbook (Similar to Chapters 8,9,10) produced Dr. Andrea Wallace of Coastal Georgia Community College are posted on line at:
http://www.hccbrandon.net/chem1211/mod5/11Chap4.htm

Your author has flipped Chapters 8 and 9 from addition to addition. Parts A,B,C,D are the heart of the 4th edition Chapter 9, formerly Chapter 8 in the 2nd and 3rd editions. So we did ABCD after doing EF in lecture.

Chapter 8 introduced Chemical Equations which are tested in Parts E,F,G,H. So we will start this Assignment outline with Part E and the Chapter 8 topics:

Part E: Basic Stoichiometric Definitions:

In Module Three we studied the composition of an atom. In Module Four we made compounds. Now for Module Five we finally should be able to react these compounds in chemical reactions. The basic symbology of a chemical reaction is explained in Section 8.2 for Chapter 8 of the Corwin text. See Table 8.1 on page 200.

What are reactants? What are products. What does the arrow between mean? How do we indicate the phase of the chemical? Look at page 199-200. Table 8.1 summarizes the symbols of a chemical reaction.

Back in Chapter 4 in Section 4.8 on page 92, the author introduces the Law of Conservation of Mass. This leads to the stoichiometric coefficients that balance a chemical reaction on page 204.

Part F Balancing Chemical Reactions

Section 8.3 shows guidelines for balance an chemical reaction on page. You should be able to balance a chemical reaction by inspection. In section 8.3 pages 202-203 are Corwin’s 5th edition guidelines for balancing an equation by inspection. I also have a web page with suggestiobns on how to approach balancing. Here is a summary of another set of guidelines:

Rules and Suggestions for Balancing Equations

1)     The same # and type of atom must be present on each side of the equation.

2)     Balancing is accomplished by adding coefficients.  NEVER change the subscripts.

3)     Coefficients must be in the smallest whole # ratio.

4)     Balancing is done by trial and error.

5)     Usually Balance H’s and O’s last or an element that appears in more than one place of either side of the reaction .

6)      Balance polyatomic ions as one unit in Ion Exchange reactions..

 

 In Section 8.4 five types of reactions: Combination, Decomposition, Single Replacement, Double Replacement, and Neutralization reactions are introduced. You should be able to do questions #21-24 on Page 224. These question types make good multiple choice as they deal with the general theory of chemical reactions.

At the end of the chapter on page 224 are six set of chemical equations (Questions #17-22) for you practice you skills at balancing equations by inspection.

The interactive ChemiCalc web site  will allow you to check your balancing chemical reaction skills. The practice test has a few difficult reactions where you might go to:
http://people.emich.edu/bramsay1/ccc-release/chem.html
and check your work.

Part G:

Sections 8.5 Combination Reactions and Section 8.6 Decomposition reactions discuss methods to predict the products of these types of chemical reactions. You should gain an understanding of the general principles of these types of reactions, but I WILL NOT ASK YOU to predict products for Combination and Decomposition reactions.

Section 8.7 introduces the Activity Series Concept., which leads to Section 8.8 Single Replacement Reactions. Our objectives for Part G:

1.      To explain the concept of an activity series for metals

2.      To explain the difference between the activity series for all metals and what is special about the six active metals

3.      To predict whether a single replacement reaction occurs by referring to the activity series

In the activity series insert (H2O) and (H) to understand where water and acids play a role in single replacement reactions.

After viewing some of the single replacement reaction demonstrations below, Part G requires you to predict the products (if there is a reaction) for single replacement reactions if the Activity Series and the Active Metal Series is give (which is printed at the top of this test section).

 

 

Given the following Activity Series (most common metals in nature):

Li > K > Ba > Sr > Ca > Na > (H2O**) >Mg > Al > Mn > Zn > Fe > Cd > Co > Ni >Sn> Pb > (H*) > Cu > Ag > Hg > Au
*[the (H) represents the hydrogen in an aqueous acid]
**[water is never placed in the activity series but I placed it there so you can do the active metal reactions with water as follows]

 The rule to follow is a single replacement reaction takes place only if the metal or (H) is more active than the metal or (H) it is replacing. Li will react with everything, while Hg will replace only gold. And poor gold does not react with any of the cations of metals. Therefore gold is found pure in nature, while the very active metals such as potassium and sodium are never found pure in nature, but are found as minerals (ionic compounds).

Will Mg metal react with Nitric Acid? Yes
                (Mg has a great reactivity then [H] in the series)

Mg (s) + 2 HNO3 (aq)   →  Mg(NO3)2 (aq)  + H2 (g)

Will Copper react with Nitric Acid? no
                     (Cu is below [H] in the activity series)

Cu (s)  +  HNO3 (aq)  →  no reaction

Given the following Active Metals:

Li > K > Ba > Sr > Ca > Na> (H2O)

The six very active metals are so reactive they will replace one of the two hydrogens in water and form alkaline hydroxides as products.  Hydrogen gas will bubble out of the solution. See some of the above movies for demonstrations.

Will Sodium react with water?  yes
                    (Na is one of the six active metals above)

2 Na(s) + 2 HOH (l)  2 NaOH (aq)  +  H2 (g)

For Part G practice, work all questions #53-66 on pages 226-227. For multiple choice questions you should be able to answer #47-52 on Page 225.

 

 

 

Part H:

In Parts H you will predict the products of double replacement and neutralization reactions in sections 8.10 and 8.11. First you must understand what solubility means. Section 8.9 explains the solubility rules. Table 8.2 has been printed at the top of Part H test section as well as below.

I have also provided you with a Solubility Matrix that you may use on tests to replace the above Table.

It is not covered in this section of the  book as a separate topic but on page 546 the reaction of a hydrocarbon with oxygen, or our most common type of reaction, burning is explain. This reaction is classified as: Combustion.  Any hydrocarbon or oxy-hydrocarbon will burn in oxygen to form two products, carbon dioxide and water. You are expected to be able to write these reaction, give the organic compound. For example burning gasoline:

2 C8H18  +   25 O2  à   16 CO2  +  18 H2O

 

Section 8.10 shows precipitation reactions. Section 8.11 shows you how to complete the product of an acid base naturalization reaction.

 We first will write ion exchange in aqueous solutions and shows the decomposition which takes place when H2CO3 and NH4OH are formed as products. You need these skills to do the Qualitative Analysis labs, especially the cases of the unlabelled powders and liquids labs.  These labs will give you the experience you need to do Part H.

To understand the Qualitative Labs Section 8.1 explains the evidence for chemical change:

1.      A gas is released

2.      An insoluble solid is produced (precipitate)

3.      3. A permanent color change is observed

4.      A heat energy change is notes.

How do I get you to visualize what in the test tube when you NaCl (aq).

Section 15.11 demonstrates net ionic reactions. I had dropped this requirement for the CHM 1025C course, but put it back in last Fall 2008. It is required for CHM 2045C and you also need to know it for REDOX reactions. Here are the rules:

Show as ions: soluble salts and strong acids/bases; leave as molecules/formula units insoluble salts, weak acids, covalent molecules.

 

Strong acids are: Perchloric Acid; Hydrochloric Acid; Nitric Acid; Sulfuric Acid; Hydrobromic Acid; Hydroiodic Acid. All otgher aciuds are weak.

Strong Bases are: Sodium hydroxide, Potassium hydroxide, Calcium hydroxide, Strontium hydroxide, and Barium hydroxide. All other basic hydroxides are weak.

The course home page has several interactive sites to help you with Parts F, G, H:

Module 5: Chapter 8
(Chemical Reactions)

Balancing Equations Rules && Suggestions

Balancing Chemical Equations
Corwin Interactive Shockwave Program

Reading a Chemical Reaction
Flash Demo

A Balanced Chemical Equation
Flash Demo

Double Replacement Reactions
Flash Demo

Chapter 8 Movies
(Chemical Reactions):
Flame Tests for Alkali Metals
Corwin Demo Movie

Combination Demo:
Reactions with Oxygen
Corwin .mov Movie

Combination Demo:
Formation of NaCl
Corwin .mov Movie
Decomposition Demo:
Decomposition of HgO
Corwin .mov Movie

Single Replacement Demo:
Formation of Ag Crystals
Corwin .mov

(Activity Series)
Single Replacement Demo:
Reaction of Zn with SnCl2
Corwin .mov

(Active Metals)
Single Replacement Demo:
Sodium and Potassium in Water

Double Replacement Demo:
Precipitation Reactions
Corwin .mov Movie

Kotz Chapter 4 Movies

What is a mole? Chapter 9 concentrates on the Mole Concept.

You must know the value of Avagadro's Number to three significant figures
(M-5 Parts B& E): 

6.02 x 1023  particles  is equal to one mole of these particles.

View the Movie:
http://www.hccbrandon.net/mole/WebExport/mole/ie5/index.html

Part A: Molecular Mass:

On page 1164 Section 5.5  the atomic mass of an element is defined as amu per atom. It is very important that you know from the film and Section 9.3 that the units of molar mass is grams/mole. On pages 237-238 there are examples of how to change mass to moles and moles to mass.

At anytime after you complete M-5 A, you should be able to calculate the molar mass of a compound using the periodic chart. Most stoichiometric word problems most of the time never give you this value which you may need to solve the problem most of the time.

There are problems at the end of chapter 9 to practice your molar mass calculation of a compound:
page 2547 problems #13-16.

Part B: Mole Calculations:

Your text has a lot of focus to convert masses and volumes to mole to actual particles. Section 9.2 relates the number of particles (Avagadro’s Number) to the number of moles. In 9.4 the moles are related to mass starting with the number of particles. Then vice versa. Section 9.5 defines Molar Volume. We will wait till Module 6 to do Sections 9.5 and 9.

This is the only time in the course you will need to use Avogadro's number to relate actual particles to masses and volumes. In the lab we move from masses to mole and never focus on the number of particles. For part B addition problems may be found on page 254 #17-22.

Part C: Percent Composition:

Module 5 Part C is covered in Section 9.7 of the textbook,  pages 244-245, calculating the Percent Composition of a Compound. Example 9.12 on page 245 demonstrates the process. You will calculate the Percent Composition of one compound on M-5 Exam.

There is an interactive web site that will allow you to check your work for Parts A & C. The author of ChemiCalc (which I posses two site licenses if you want a copy),  Dr. Bert Ramsay of Eastern Michigan University, has placed a small fraction of his program online. Check out:
http://people.emich.edu/bramsay1/ccc-release/chem.html

For additional examples at the end of the chapter do the Percent Composition on page 255 #39-46

 

Part D: Empirical Formula from Percent Composition and Mass Data:

Module 5 Part D is a calculation of the Empirical and Molecular Formula from the Percent Composition which is described on pages 246-249. Example 9.14 page 247 demonstrates this process for the calculation from Percent Composition.

On page 246 is an example of calculating the empirical formula from mass data (Example 9.13). 

For Section 9.9 page 248 You must know from this section what the difference is between an Empirical Formula and a true Molecular Formula of a compound and this will be tested in the Multiple choice section.

Section 13.10-Hydrate introduces the concept hydrates and Anhydrates which we may do as one of our M-5 crucible labs. Most crystalline salts come as hydrates, meaning water molecules are part of the crystalline structure. You should be able to interpret a hydrate formula where the dot between the two compounds reads "in combination with".  CuSO4 ∙ 5 H2O reads one formula unit of CuSO4 in combination with 5 molecules of water.

 There are problems at the end of the chapter to practice your empirical formula calculation of a compound: pages 255-256 problems #47-56.

 

Part I: Mole-Mole Problems

Density was the first two dimensional unit (mass/volume) introduced in Chapter 3. In section 9.3 the second two dimensional unit Molar Mass  (grams/mole) was introduced. In sections 10.1 and 10.2 the concept of the mole ratio is introduced.

I have broken the section into two types of problems, the Mole-Mole Problem (section 10.2) for Part I, and the Mass-Mass Problem for Part J (Section 10.4).

The Mole-Mole Problem is only a one step dimensional analysis problem. However, it is the bridge between molecules that has to be crossed in all stoichiometric problems involving a chemical reaction as described below.  In addition to the sample test, there are five mole-mole problems at the end of the chapter for your practice: page 283 problem #7 through #12.

All roads in stoichiometry require a balanced chemical reaction and the coefficients used to balance the chemical reaction are used as the bridge to change from one chemical to another using the MOLE RATIO. This is also why in your dimensional analysis sequence you need to label the unit with compound the unit describes. You should not just use 4 grams or 5 moles, you should say 4 gramsNaCl or 5 moleNaCl. Notice that in all the worked examples in chapter 4, the units are labeled with the compounds being measured.


 

Part J: Mass-Mass Problems:

Mass relationships in stoichiometric calculations require a three step dimensional analysis sequence:

MassA --> MolesA --> MoleB --> MassB


 

Example 10.5 on page 266 shows this road map.

You need to work many examples of these problems.  On page 284 at the end of the chapter please try #19-#28.

 

Part K: Excess-Limiting Reagent Problems

Read section 10.7 for the discussion of the limiting reagent concept. Then section 10.8 applies the concept to problems of the text to modify mass-mass problems to deal with the excess-limiting reagent concept in a chemical equation.

 Corwin solves the Limiting-Excess reagent problems similar to my strategy. You have two gram-gram problems. Then which ever problem produces the least amount of product is the LIMITING REAGENT

Part L: Impure Reagent/Percent Yield Calculations

Section 10.9 of the text introduces the concept of theoretical yield and actual yield. When you do a mass-mass calculation in Part J above, the amounts you calculate are theoretical amounts. In Part K we saw that when you chemically react compounds, usually only one of the reactants will be used up and the other reagent(s) are usually in excess amounts to insure completion of the reaction. In the laboratory we hardly ever produced the theoretical amounts calculated in a Part J type problem. Instead we have a mass which is less than the theoretical amount (yield) and this is called the actual yield. The formula in section 10.9 page 279 shows how to calculate the per cent yield when an actual amount is given.

Percent Yield is just another way we can add an extra step to a mass-mass calculation in Part J. Also we can add another % to the problem. Many chemicals do not come as pure reagents. They are usually labeled technical grade reagents and are less than 100% pure. So if you have an impure reagent, you must apply the Percentage in the beginning to change the amount of impure reagent to the real/pure amount of reagent that will chemically react.

The book does not have a separate section for impure reagents.

For Part L there are only four simple problems for you to practice these objectives at the end of the chapter. On page 286 problems #59-74 cover Percent Yield without applying the concept to the gram-gram problem type.