CHEMISTRY 103-104

PRINCIPLES OF CHEMISTRY

Report Sheets for Laboratory Experiments

CARL P. FICTORIE

DORDT COLLEGE

SIOUX CENTER, IOWA

Copyright © 2009

Laboratory Equipment

The following equipment will be necessary to carry out the experiments in this course and

should be in your lab drawer. You may be asked to provide a $5.00 deposit in order to obtain a

key to your assigned drawer. Lost keys will be replaced for a $5.00 fee. Use the list and pictures

in your text to identify your equipment and check that it is present in good condition during

check-in and check-out. You will not be charged for lost or broken equipment, but you must

properly check out and have your T.A. check your lab drawer in order to receive your key

refund.

You will also need a bound laboratory notebook, safety glasses, and a fine point permanent

marker. You would be wise to regularly bring your calculator and textbook to lab.

Fall 103 Spring 104 Equipment In Out In Out 3-250-mL Erlenmeyer flasks ____ ____ ____ ____

3-600-mL or 400-ml beakers ____ ____ ____ ____

1-250-mL beaker ____ ____ ____ ____

4-100-mL beakers ____ ____ ____ ____

1-plastic funnel ____ ____ ____ ____

1-200 mm (8") test tube ____ ____ ____ ____

4-large test tubes (150 mm/6") ____ ____ ____ ____

8-small test tubes (100 mm/4") ____ ____ ____ ____

3-glass stirrers/rubber policemen ____ ____ ____ ____

1-pair of tongs ____ ____ ____ ____

1-100-mL volumetric flask ____ ____ ____ ____

1-10-mL graduated cylinder ____ ____ ____ ____

1-25-mL graduated cylinder ____ ____ ____ ____

1-10 mL pipet ____ ____ ____ ____

1-10 mL graduated pipet ____ ____ ____ ____

1 thermometer ____ ____ ____ ____

1-evaporating dish ____ ____ ____ ____

1-wire screen (may be insulated) ____ ____ ____ ____

1-wash bottle ____ ____ ____ ____

3-watch glasses ____ ____ ____ ____

2-magnetic stir-bar ____ ____ ____ ____

2-spatulas (different styles) ____ ____ ____ ____

1-pair tweezers ____ ____ ____ ____

1-pipette bulb (light blue) ____ ____ ____ ____

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NAME: _______________________________________ LAB SECTION: ______

PARTNER: _______________________________________

Experiment 1 Report Sheet Laboratory Safety And Chemical Hygiene

Laboratory Protocol Exercise

This exercise is intended to provide you with the reasons behind many of the laboratory

protocols. Pairs of lab partners (4 students) will work as a group on this activity.

For each of the protocols listed, provide reasons for their necessity. You should provide

multiple reasons for each. You should consider the negative impacts of not following the

protocol. For example, the protocol regarding not working alone in the laboratory is justified on

the grounds that: (1) students are new to the lab and need supervision (this reason diminishes

with experience), (2) if one person gets injured, the other person can administer first aid or obtain

help, (3) one person can catch an error or oversight on the part of the other person and call

attention to it before an accident happens or an experiment gets ruined, and (4) if the persons are

working on different projects (as might be the case in industry) the persons can act as witnesses

to each other's work for the purposes of patent protection or result verification. Note that not all

the reasons are based on safety principles.

1. Do not wear jewelry in the laboratory.

2. Wash your hands when you leave the laboratory.

3. Never perform unauthorized experiments.

4. Never bring food or drink into the laboratory.

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5. Keep your bench space neat and organized.

6. Label all containers (bottles, beakers, flasks, etc.) with the contents.

7. Always confine long hair in the laboratory.

8. Students may bring visitors only with the instructor's consent.

9. Know beforehand the hazardous characteristics of the chemicals with which you will be

working.

10. Wear safety glasses at all times in the laboratory.

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For each of the statements below, discuss whether it is true or false, including whether other

conditions might impact the veracity of the statement (that is, it might be partly true).

a) Doing things safely is not merely the right way to work—it is the only way.

b) You can get injured in the laboratory even if you have followed all necessary precautions.

c) Gloves will protect your hands from hazardous chemicals.

d) If you can smell a chemical, it is causing you harm.

e) Hazardous waste cannot be poured down a drain (into a sanitary sewer).

f) It is possible to reduce one's risk of injury to zero.

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Safety Resources and Laboratory Equipment

This exercise is intended to familiarize you with the layout of the laboratory, the fixed

equipment, and the safety equipment. Attached is a map of the building.

Evacuating the Laboratory

Knowing how to exit the building quickly can be a matter of life and death. This part of the

exercise is intended to teach you the locations of the three main building exits.

1. Each lab has three exits (one leads to the other lab via the balance room).

2. Each lab exit leads to one of the main building exits (the main lobby exit, the south west exit,

and the east exit).

3. Use the building maps to plot a course from the lab to each exit and draw a line on the map

showing the course.

4. Starting from the lab each time, go to the exit. Outside you will find a lab TA who will

initial this sheet after confirming that the course is acceptable and checking your name (be

prepared to show an ID as we haven't mastered names yet!).

Main Lobby Exit _____ SW Exit _____ East Exit _____

Equipment Scavenger Hunt

This part of the exercise will help you learn the location of various laboratory and safety

equipment. Below is a list of lab equipment. On the map of the chemistry labs, indicate the

location of the equipment using the abbreviation given. Many items are located in the lab, but

some are in SB210, the hall, or the lobby. Find the equipment in both labs as you might work or

need emergency equipment from the other lab. Identify below any items you could not find.

Equipment List Analytical Balances (AB) Instructor's Mailbox (MB)

Broken Glass Box (BG) MSDS Binder (MSDS)

Storage cubbies (ST) Normal Trash Can (NT)

DI Water Carboys (DI) Paper Towel Holder (PT)

Drinking Fountain (DR) Recycling Bin (RB)

Dust Pan and Brush (DP) Pencil Sharpener (PS)

Emergency Response Flip-book (ER) Reagent Balances (RB)

Eye Wash (EW) Safety Shower (SS)

Fire Alarm Pull Station-Hall (FA) Public Telephone (PH)

Fire Alarm Pull Station-Lab (FA)

Fire Blanket (FB)

Fire Extinguisher-Hall (FE) Emergency Phone Numbers

Fire Extinguisher-Lab (FE) Fire:

First Aid Kit (FK) Police:

Graded Homework Box (HW) College Security (daytime):

Graded Lab Report Box (LR) Hazardous Materials:

Instructor's Office (IO) Poison Control Center:

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Figure 1.1 Map of Science Building: Ground and Upper Levels

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NAME: _______________________________________ LAB SECTION: ______

PARTNER: _______________________________________

Experiment 2 Report Sheet Floaters and Sinkers: The Density of Sodas

Show representative calculations on the right margin.

A Brief Exercise to Illustrate Uncertainty in Measurement

a) Volume of liquid in displayed buret (mL): _______

b) Extra Credit--class mean and standard deviation of volume measurement.

________ ________

Are the Densities of Coke and Diet Coke Different?

Record your observation and provide a hypothesis to explain the phenomenon.

Determining Density with a Graduated Cylinder

a) Mass of cylinder (g): ________ Assigned. Soda:

Sample 1 Sample 2 Sample 3

b) Mass of cylinder w/ soda (g): ________ ________ _________

c) Mass of soda (g): ________ ________ _________

d) Density (g/cm3): ________ ________ _________

e) Avg. d and St. Dev. ________ ________ (g/cm3)

Report individual density values to the instructor.

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Determining Density with a Pipet

a) Mass of beaker (g): ________ Assigned. Soda:

Sample 1 Sample 2 Sample 3

b) Mass of beaker w/ soda (g): ________ ________ _________

c) Mass of soda (g): ________ ________ _________

d) Density (g/cm3): ________ ________ _________

e) Avg. d and St. Dev. ________ ________ (g/cm3)

Report individual density values to the instructor.

Determining Density with a Buret

a) Mass of beaker (g): ________ Assigned. Soda:

Sample 1 Sample 2 Sample 3

b) Initial Volume (mL) ________ ________ _________

c) Final Volume (mL) ________ ________ _________

d) Total Volume (mL) ________ ________ _________

e) Mass of beaker w/ soda (g): ________ ________ _________

f) Mass of soda (g): ________ ________ _________

g) Density (g/cm3): ________ ________ _________

h) Avg. d and St. Dev. ________ ________ (g/cm3)

Report individual density values to the instructor.

Conclusions

1. In a brief paragraph, list the conclusions that can be drawn regarding the density of Coke and

Diet Coke and regarding the accuracy and precision of the various tools.

2. What conclusions can you draw about the property of density based on the discussion?

Suggest reasons why Coke and Diet Coke have different densities.

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NAME: _______________________________________ LAB SECTION: ______

PARTNER: _______________________________________

Experiment 3 Report Sheet The Statistics of Sampling

Data for Your Lot

a) Size of bag (oz or g): _______

b) Counting:

Color _____ _____ _____ _____ _____ _____ Total (n)

Sample #1 _____ _____ _____ ______ ______ ______ _____

Sample #2 _____ _____ _____ ______ ______ ______ _____

Sample #3 _____ _____ _____ ______ ______ ______ _____

Mean, _____ _____ _____ ______ ______ ______ _____

Fraction, px _____ _____ _____ ______ ______ ______

s _____ _____ _____ ______ ______ ______ _____

s/ x =sr _____ _____ _____ ______ ______ ______ _____

σx,r _____ _____ _____ ______ ______ ______

Once you have this table completed, give a copy to the instructor.

Questions Based on Your Lot

1. For a lot of three samples, one can be about 90% confident that random error is the only

concern if a measured mean (your px) is within 2 standard deviations (high or low) of an

accepted reference value. That is:

x

spp refxsamplex 2,,

Is this the case for the assigned color in your set of samples?

2. Compare s/ x and x,r for your data in light of the discussion in the Introduction.

Data from the Class

You need only concern yourself with the assigned color M&Ms (red unless told otherwise), on

the assumption that principles apply to all the colors. The instructor will collect the data in class

and provide copies for your use.

Questions Based on Class Data

1. For each of the lots, is the measured mean (pred) within two standard deviations of the

reference value (pred = 0.25)?

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2. Does the value of the relative standard deviation, sr,red, vary with the size of the sample?

Does this indicate any preference for sample size?

3. How large (what value of n) is needed to ensure that x,r for the red M&Ms is less than

0.01pred (1% relative standard deviation)?

4. Consider the water hardness lab. The calcium content in the hard water is about 600

mg/L CaCO3. This corresponds to about 6.0 x 10-3

mol/L of calcium. Water has a

concentration of approximately 55.55 mol/L. If we assume the aqueous solution is a

mixture of relatively uniform particles (molecules, mostly water), and assume the density

of hard water is 1.0 g/mL, what is the predicted standard deviation x,r in the

concentration of the calcium in a 10.0 mL sample of hard water? What does this tell you

about the significance of sampling error in a well mixed liquid solution?

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NAME: _______________________________________ LAB SECTION: ______

PARTNER: _______________________________________

Experiment 4 Report Sheet Measuring A Molecule: Avogadro's Number

Data and Calculations

Note: for lines 5, 6, 8, and 9, the c refers to calculations regarding the cube shape and the r

refers to the rectangular solid

1a. # of drops per mL __________ ± __________

b. Volume of one drop (mL) __________

Trial #1 Trial #2 Trial #3

2a. # drops stearic acid soln __________ __________ __________

b. Volume of soln used (mL) __________ __________ __________

3a. Concentration of soln (g/L) __________

b. Mass of stearic acid used (g) __________ __________ __________

4. Volume of monolayer (cm3) __________ __________ __________

5a. Diameter of watchglass (cm) __________ ± __________

b. Area of water surface (cm2) __________ __________ __________

6. Thickness of monolayer (cm) __________ __________ __________

7. Area occupied by c_________ __________ __________

one molecule (cm2) r_________ __________ __________

8. Number of molecules in layer c_________ __________ __________

r_________ __________ __________

9. Moles acid in layer _________ __________ __________

10. Avogadro's number c_________ __________ __________

r_________ __________ __________

11. Average and Std. Dev. c_________ ± _________

r_________ ± _________

12. Avogadro's number for _________ ± _________

cylindrical shapes (extra credit)

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Questions

Note: answer in your notebook and on the back of your report sheet.

1. Which of the shapes gives the best estimate of Avogadro's number?

2. List possible sources of error in the experimental method. How can each kind of error be

minimized?

3. List possible sources of errors in the assumptions made in the microscopic model.

4. Which of the measured data values limits the precision of this experiment?

5. The molar volume of any substance is the volume occupied by one mole of that substance.

a. Calculate the molar volume (cm3/mol) of stearic acid from its known molar mass and

density.

b. The molar volume divided by Avogadro's number will give the volume of one

molecule, if there is no empty space in the molecular packing. Calculate this

molecular volume using the accepted value of Avogadro's number. Compare it with

the molecular volumes that you calculate from your data and assumptions [7(a) and

7(b) on the preceding page]. Is your order of magnitude correct?

6. In a paragraph, discuss the results in light of the assumptions made in the model. The

discussion should include a statistical analysis also.

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NAME: _______________________________________ LAB SECTION: ______

PARTNER: _______________________________________

Experiment 5 Report Sheet Determination of the Formula of a Hydrate – A Greener Approach

Initial Hydrate.

1. Crucible ID# _________

2. Mass of empty, dry crucible _________

3. Mass of crucible with hydrate _________

4. Initial mass of hydrate _________

Dehydrated Copper(II) Chloride

1. First mass of dehydrated CuCl2 in crucible _________

2. Second mass of dehydrated CuCl2 in crucible _________

3. Final mass of dehydrated CuCl2 _________

4. Moles of CuCl2 in the hydrate _________

5. Mass of water driven off the hydrate _________

6. Moles of water driven off the hydrate _________

7. Formula of the CuCl2 hydrate _________

8. Full name of hydrate: _________________________________

Rehydrated CuCl2

1. Mass of bottle recycled sample bottle before addition _________

2. Mass of bottle recycled sample bottle after addition _________

3. Mass rehydrated CuCl2 _________

4. % recovery of hydrate _________

"Hurry up and wait" Questions

1. Define ―hydrate‖ and discuss the bonding associated with a hydrate.

2. If a hydrated salt loses 0.3211 g of mass when heated strongly, how many moles of water

were driven off? Show your work.

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3. Write the chemical formula for Magnesium sulfate heptahydrate.

4. Give the chemical name of the following salt: FeCl3 6H2O.

General Questions

5. Why must the crucible and lids be heated before the initial weighing?

6. How would your final result (value of ―?‖ in the formula) have been affected if the crucible

had been damp before the first weighing? Too high? Too low? Not affected? Explain.

7. Drying agents, or desiccants, are sometimes used to keep humidity low inside packaged

goods (like leather shoes and purses, or camera equipment). What type of substance

encountered in this experiment might serve well as a desiccant? Explain.

8. Unfortunately not all of your original sample will end up in the container for reuse. At what

points in the experiment do you ―lose‖ some of the sample? Give an example of one pro and

one con of the method you used to recycle the hydrate.

9. This experiment initially used a barium salt to demonstrate the dehydration of a salt. In

addition, the salt was thrown away. Propose a reason why you think this does not implement

the concepts of green chemistry. Refer to the world wide web for a listing of the 12

Principles of green chemistry

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NAME: _______________________________________ LAB SECTION: ______

PARTNER: _______________________________________

Experiment 6 Report Sheet Preparation And Analysis Of A Ni(II) Coordination Compound

Preparation of Ni(II) coordination compound.

1. Mass of NiCl2 6H2O _________

2. Mass of Nickel(II) coordination compound _________

3. % yield of Nickel(II) coordination compound _________

(cannot be calculated until empirical formula has been determined)

Analysis of Ammonia. Sample 1 Sample 2 Sample 3

1. Mass nickel compound sample _________ _________ _________

2. Molarity of HCl solution _________

3. Volume of HCl solution used _________ _________ _________

4. Moles HCl used/moles ammonia _________ _________ _________

5. Mass of ammonia in sample _________ _________ _________

6. Mass % ammonia in sample _________ _________ _________

7. Avg mass % NH3 in sample _________ ± _________

Analysis of Nickel.

1. Molarity of EDTA solution _________

2. Mass nickel compound sample _________ _________ _________

3. Volume of EDTA solution used _________ _________ _________

4. Moles EDTA used/moles Ni _________ _________ _________

5. Mass of nickel in sample _________ _________ _________

6. Mass % nickel in sample _________ _________ _________

7. Avg mass % Ni in sample _________ ± _________

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Analysis of Chloride. Sample 1 Sample 2 Sample 3

1. Mass AgNO3 _________

1. Molarity of AgNO3 _________

2. Mass nickel compound sample _________ _________ _________

3. Volume of AgNO3 used _________ _________ _________

4. Moles Ag/moles chloride _________ _________ _________

5. Mass of chloride in sample _________ _________ _________

6. Mass % chloride in sample _________ _________ _________

7. Average mass % chloride in sample _________ ± _________

Determination of Empirical Formula

Formula of nickel(II) compound _________

1. Calculate and report the percent (by mass) composition of the compound for NH3, Ni2+

, and

Cl-. Include standard deviations for each percentage. For each, you will need to determine

the number moles and then the mass of analyte (NH3, Ni+2

, or Cl-) from the titration data.

The ratio of mass analyte to mass sample is the % mass of the analyte.

2. Using the percent composition, determine the empirical formula of your complex (assume it

contains one Ni atom per formula unit).

3. Write balanced net ionic equations for the synthesis and for the various analytical processes

for this compound based.

4. Calculate the percent yield for the preparation of the Ni(II) compound. This requires

knowledge of the synthesis reaction and the formula of the coordination compound.

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NAME: _______________________________________ LAB SECTION: ______

PARTNER: _______________________________________

Experiment 7 Report Sheet Atomic Spectroscopy

A. Calibration of the Spectroscope.

Record your observed He lines and reference to known values.

Observed Actual Observed Actual Observed Actual

B. The Hydrogen Spectrum Line 1 2 3 4

1. Color _______ _______ _______ _______

2. Wavelength (nm) _______ _______ _______ _______

3. Wavelength (cm) _______ _______ _______ _______

4. n2 _______ _______ _______ _______

5. R (cm-1

) _______ _______ _______ _______

6. Mean value of R (cm-1

) _______ ± _______

7. Energy of atomic level n2 (J) _______ _______ _______ _______

C. Other Emission Spectra

Answer the first three questions for each of the available spectrum tubes.

1. What is the overall color of the spectrum tube?

2. What are the wavelengths and colors of the main lines in the spectra?

3. Is the answer to #2 consistent with the answer to #1? Why?

a. For mercury, compare the tube to a regular fluorescent bulb and a regular incandescent

bulb.

b. Compare and contrast the spectra.

4. Why is the spectrum tube "bluer" than fluorescent tubes (consider the frosting)?

(It would be helpful to do research on the Internet to add depth to your discussion of the

fluorescent bulb.)

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Questions

1. Bohr showed that the Rydberg constant could be calculated from known fundamental

constants. The equation is:

ch

meR e

32

0

42

)4(

2 (7-1)

Using a resource that provides accurate values for each of these constants (such as the

Handbook of Chemistry and Physics or NIST Fundamental Constants database), calculate R

(in cm-1

, watch for units) and compare it to your value. Discuss any differences in the two

values. Also show that the units work. (Hint: during this calculation, intermediate values

can become very small, <10-100

, which can cause an error or a result of zero on some

calculators. One way around this is to alternate multiplying values in the numerator with

dividing values in the denominator so that intermediate values remain within the limits of the

calculator.)

2. How would the absorption spectrum of an atom differ from its emission spectrum? How

would one measure an absorption spectrum?

3. What is the longest possible wavelength for a line in the Balmer (n2 = 2) series? What is the

shortest possible wavelength? Does the whole series fall within the visible spectrum (400-

700 nm)?

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NAME: _______________________________________ LAB SECTION: ______

PARTNER: _______________________________________

Experiment 8 Report Sheet Determination of Manganese in Steel

A. Beer's Law Plot

Include the Beer's Law plot.

Include copies of the spreadsheet outputs.

The value of the molar absorptivity, , is ______ ± ______

B. Percent Mn in Steel

1. Sample ID# ______

2. Mass of sample taken ______

3. Absorbance of sample ______ ______ ______

4. Average absorbance ______ ± ______ (from spreadsheet)

5. Concentration, mol/L ______ ± ______ (from spreadsheet)

6. Mass % Mn in sample ______ ± ______

(show the calculations used to obtain 6)

Questions

1. You will notice from Figure 8.1 that 525 nm corresponds to a maximum in the absorbance

spectrum. Why should we use a maximum in the absorbance rather than a minimum such as

425 nm?

2. Why is it important to use the maximum value, rather than an intermediate value such as 500

nm? (This answer is different than the answer to #1.)

3. Which colors of the spectrum are absorbed by permanganate? Which are transmitted? How

does this give rise to the observed color of permanganate?

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NAME: _______________________________________ LAB SECTION: ______

PARTNER: _______________________________________

Experiment 9 Report Sheet Polymers

Questions

1. Your nylon string is pretty weak, but nylon is used to make strong ropes. Explain how your

string could be used to make a strong rope.

2. Why does the sebacoyl chloride solution float on top of the hexamethylenediamine solution?

3 Describe the physical changes that occur in the mixture while you make the slime.

4 Describe the physical changes that occur in the mixture while you make the silly putty.

5 Compare and contrast the properties of the three polymers you made. What’s the same?

What’s different?

6 Crazy-glue® is a cyanoacrylate polymer. The monomer unit is shown below. Draw a

segment of the polymer.

H

H C

N

O

CH3

O

methyl cyanoacrylate

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NAME: _______________________________________ LAB SECTION: ______

PARTNER: _______________________________________

Experiment 11 Report Sheet Soap Making

a) Formulation: _______

b) Mass of Reagents used (g):

Water _______

NaOH _______

Canola Oil _______

Lard _______

Olive Oil _______

Soy oil _______

Shortening _______

_________: _______

Total Mass: _______

c) Total mass of soap after curing (g): _______

d) Compare the total mass of cured soap with the mass of reagents used. Are the masses the

same or different? Explain your answer.

Analysis

a) Describe the color and scent of the soap. Are they what you expected?

b) Use your soap to wash your hands using tap water. Describe how it feels, how well it lathers,

bubble sizes, and how well it rinses away.

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c) Use your soap to wash your hands using DI water. Describe how it feels, how well it lathers,

bubble sizes, and how well it rinses away.

pH Tests

color pH classify

a) pH of DI water: _____ ____ ______

b) pH of skin: _______ ____ ______

c) pH of soap: _______ ____ ______

d) Discuss the results, why would the acidity of soap be the same or different than the acidity of

skin?

Questions

1. Determine the molar mass of a triglyceride made with equal numbers of lauric, oleic, and

linoleic acids. What is the SAP value of this triglyceride?

2. For your formulation, what are the most abundant and second most abundant fatty acids?

This is done by taking the percentage of each fatty acid from Table 2, and multiplying by the

mass used in the formulations. Masses of the same fatty acid from different fats or oils are

then added. Are the properties of the end soap consistent with these fatty acids?

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NAME: _______________________________________ LAB SECTION: ______

PARTNER: _______________________________________

Experiment 12 Report Sheet Volumetric Studies of Acid-Base Reactions

A. Standardization of NaOH

Sample 1 2 3

1. Mass of KHP _______ _______ _______

2. Volume NaOH used _______ _______ _______

3. Molarity of NaOH _______ _______ _______

4. Average molarity of NaOH _______ ± _______

B. Vinegar Analysis

Brand of vinegar used and cost _______ _______

1. Volume NaOH used _______ _______ _______

2. Molarity of dilute vinegar _______ _______ _______

3. Avg. molarity of diluted vinegar _______ ± _______

4. Molarity of original vinegar _______ ± _______

5. Mass % acetic acid _______ ± _______

C. Molar Mass of Unknown Acid Unknown: _________

1. Mass of unknown acid _______ _______ _______

2. Volume NaOH used _______ _______ _______

3. Molar mass of acid (monoprotic) _______ _______ _______

4. Average molar mass-monoprotic _______ ± _______

5. Molar mass of acid (diprotic) _______ _______ _______

6. Average molar mass-diprotic _______ ± _______

7. Identity of your unknown acid ________________

Explain your reasoning

Attach Answers to Questions

1. Does your analysis show that the vinegar has at least 5% acetic acid? Justify your answer.

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NAME: _______________________________________ LAB SECTION: ______

PARTNER: None for this experiment

Experiment 15 Report Sheet Molecular Modeling

A. VSEPR Theory

There are ways to determine the shape of a molecule. Valance Shell Electron Pair Repulsion

Theory is one of the methods used to determine the shape of a compound. This exercise will

allow you to build and view a few compounds to verify this theory.

1. When you start PCModel, select Structure Name under the Edit menu. Enter your name,

which will allow you to identify printouts you are asked to make.

2. Build and minimize water, ammonia, and methane. Record the MMX energy and Hf for

each. For each of these, use query to determine the center atom to hydrogen bond length and

the angle indicated in the diagram below. (Build H2O first, then NH3, then CH4. Use the PT

function to change atoms.)

3. For water, print the structure, (check the energy window check-box in the print dialog box)

after using query and minimizing. This will print the picture, the bond angle and bond

distance, along with the calculation results from the output window. You may print as often

as you wish, but must turn in any printouts requested in this experiment (all the exercises).

4. Do the bond lengths get smaller or larger going from methane to water?

5. What happens to the bond angles in each? What causes the change in bond angle?

6. What name is given to the shape of each compound?

Compound EMMX Hf Bond length

Bond angle

Name of Shape

methane

ammonia

water

Molecular structures of methane, ammonia, and water

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B. Bond Lengths - Single, Double, or Triple Bonds

Two factors determine the length of a bond. These are: 1) the type of bond between the two

atoms and 2) the types of atoms which make up the bond. The purpose of this exercise is to allow

you to look at how the type of bond affects the bond length.

1. Build and minimize ethane, ethene, and ethyne. Record the energy and Hf for each. Hf

displays as Hf in the output window. (Hint: in PC Model you can convert ethane to ethene

by using the add bond function, then the H/AD function). For each of these, use query to

determine the carbon-carbon bond length and the angle indicated in the diagram below.

2. Do the carbon-carbon bond lengths get smaller or larger going from ethane to ethyne?

5. What is the relationship between the bond length and the strength of the bond?

6. Do the carbon-hydrogen bond lengths change significantly?

7. Include printouts for each of the three structures.

Compound EMMX Hf Hexpt C-C bond

length

C-H bond

length

H-C-H bond angle

ethane

ethene

ethyne

Molecular structures of ethane, ethene, and ethyne

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C. Bond Lengths - Type of Atoms

Two factors determine the lenth of a bond. These are: 1)the type of bond between the two atoms

and 2) the types of atoms which make up the bond. The purpose of this exercise is to allow you

to look at how the type of atom affects the bond length.

1. Build and minimize the halogen series of methanes: fluoromethane, chloromethane,

bromomethane, and iodomethane. For each, record the energy, Hf, carbon-halogen bond

length, and the angle indicated in the diagram below.

2. Do the lengths increase or decrease from fluorine to iodine? Does this match what you expect

to see from your study of the periodic properties?

8. Which is a better property to use to determine the stability of a compound, the energy or the

Hf?

9. Include a printout for one of the four molecules.

Compound EMMX Hf C-X bond length

H-C-X bond angle

fluoromethane

chloromethane

bromomethane

iodomethane

Molecular structures of

fluoromethane, chloromethane, bromomethane, and iodomethane

30

D. Bond Energy

Aliphatic carbon centered radicals are stabilized by alkyl groups. In a series of compounds, the

bond dissociation energy of a CH bond decreases as the resulting radical center becomes more

substituted.

This exercise uses the carbon radical. This is a molecule from which a hydrogen atom has

been removed, leaving behind a carbon with three substituents and a single, non-bonded electron,

R3C , which is a neutral molecule. The carbon radical is made by removing hydrogens using the

[H/AD] tool, converting the desired carbon to the radical using the [C ] button on the periodic

table, and adding the hydrogen atoms back to the molecule.

1. Build and minimize ethane, propane, tert - butane, and their corresponding free radicals. Also

build the isopropyl radical.

2. Are the energy differences in the table reflected in your calculations?

3. Include a printout for tert-butane and the tert-butyl radical.

4. Plot a graph of the difference in H, or the ( H), between the radical and its corresponding

hydrocarbon [ H (radical) - H (hydrocarbon)] vs. the number of carbon substituents on the radical.

Compound Hf Hexpt H(radical) -

H(hydrocarbon)

ethane -20.2 N/A

ethyl radical 26.5

propane -24.6 N/A

propyl radical 22.7

isopropy radical 19.1

tert-butane -31.5 N/A

tert-butyl radical 8.4

All experimental values from Benson Thermochemical Kinetics,Wiley, 1979; p. 299, gas phase

at 300 K, and CRC 1996 edition.

31

E. Rotational Energy Barriers

In organic molecules, there is ordinarily free rotation around a carbon-carbon single bond.

However, as the substituents on the carbon atoms become larger, steric hinderance restricts the

rotation.

1. Draw an ethane molecule and minimize the structure. Use "Query" on the toolbar to measure

and record the C-C bond distance, the C-H bond distance, the C-C-H bond angle, and the H-

C-C-H dihedral angle. Build an ethane molecule with a model kit and arrange the structure to

match the minimized structure from PC Model. Use the [CPK Surface] function on the

[View] menu to look at a space filling model.

2. Select the two carbon atoms. Select the [Rot_E] function in the [Compute] menu. This

function will calculate and graph the MMX energy as the molecule is rotated about the

selected bond. Adjust the Step Size to 5° and the Total Rotation to 360° and click on [OK]. A

graph will appear. Print the graph (it automatically dumps to the default printer). The

horizontal axis is the dihedral angle, the angle of rotation. The vertical axis is the MMX

energy. Describe the features of the graph and associate them with the features of the

molecule as you rotate it about the C-C bond. Record the minimum and maximum MMX

energies from the graph. Exit the window.

3. Use the periodic table to change one hydrogen on each carbon to flourine. Flourine displays

with the same color as carbon. If you use [View]-[Labels] and display "Hydrogens and Lone

Pairs" the non-carbon atoms will be labelled. Minimize the structure and obtain the same

bond distance and bond angle information as above. Build a model of 1,2-difluoroethane and

match the structure to the minimized structure. Also view the CPK structure.

4. Use the [Rot_E] function to evaluate the rotational energy barriers and print print the plot.

Record the minimum and maximum energies. Compare and contrast the graph with that of

ethane.

5. Is your structure the lowest energy structure on the plot (your structure corresponding to the

leftmost point)? If not, what is the lowest energy structure?

6. On each graph, draw line structures to show the geometry of the molecule at the bottom of

each valley and at the top of each peak.

7. Use the periodic table to change the fluorines to iodines. Repeat the steps above for 1,2-

diiodoethane. Compare and contrast your results with ethane and difluoroethane.

32

8. (Extra Credit) Repeat the comparison for butane (using the central C-C bond for rotations).

Compound EMMX Hf C-C (Å) C-X (Å) C-C-X (°) X-C-C-X (°) Rot-E min

Rot-E max

Ethane

FH2C-CH2F

IH2C-CH2I

Butane

(use middle C-

C bond)

C C

H

HH H

HH

ethane

C C

F

HH H

HF

difluoroethane

C C

CH3

HH H

HCH

3

butane

C C

I

HH H

HI

diiodoethane showing points for measuring dihedral angle

1

2 3

4

33

F. Rotational Barriers in 2-Butene

Rotation about single bonds, absent significant steric hinderance, is facile. However, rotation

about double bonds is difficult due to the presence of a bond.

Rotational Energy Barriers

Rot_E Max

Rot_E Min

# minima

trans-2-butene

C-C bond

trans-2-butene

C=C bond

cis-2-butene

C=C bond

1. Compare the rotational barriers around a C-C single bond and a C=C double bond. Using the

model kit, build a model of trans-2-butene, being careful to match the orientation of the

terminal methyl groups to match PC Model's picture.

2. Build trans-2-butene in PCModel and minimize the structure. In the minimized trans-2-

butene, [SelAtm] a terminal C and the C bonded to it, one of the single bonds. On the

[Compute] menu, select [Rot_E]. Change the "Step Size" to 5° and the "Total Rotation" to

360° and click on [OK]. A graph will appear. This is a plot of the MMX energy versus

dihedral angle, the angle of rotation about the C-C single bond. Match the observed minima

and maxima to the orientation of the methyl group. Discuss the reason for the peaks. Record

the minimum and maximum MMX energy. Print the plot and exit the window.

3. Repeat the Rot_E process, but now select the two atoms that form the C=C double bond.

Compare the Min-Max difference to that for the C-C single bond. How many minima are

there? What geometries do the minima correspond to? Do both minima have the same

energy? Why or why not?

4. On each graph, draw line structures to show the geometry of the molecule at the bottom of

each valley and at the top of each peak.

34

5. (Extra Credit) Repeat, but start with cis-2-butene. Do you get the same Min-Max MMX

energies as trans-2-butene? Should you get the same energies? Why or why not?

6. (Extra Credit) PC Model has a feature called "Dihedral Driver". It also calculates molecular

energy as one rotates a bond, but minimizes the structure at each step. To use this function,

you must select four atoms. For example, in butane, we can label the four atoms Ca-Cb=Cc-

Cd. To measure the molecular energy as you rotate about the double bond, you select all four

atoms Ca, Cb, Cc, and Cd in this order. In other words, you need to select one extra atom on

each of the atoms in the bond of interest. Use the dihedral driver to prepare graphs for both

trans- and cis-butene and compare the results. Do you get the same Min-Max MMX energies

as trans-2-butene? Should you get the same energies? Why or why not?

CH3

C C

CH3

H

H

H

C C

CH3

H

CH3

H

C C

C

H

H CH3

HH

trans-2-butene cis-2-butene 1-butene

35

G. Resonance

1. Draw and minimize the following compounds with and without assigning the pi atoms.

Record the data requested in the table below. Be sure the bond length queries are visible

before proceeding to the next step.

2. Select "Pi atoms" from the "Mark" menu, click on "All" if needed, and click on [OK]. A tilde

(~) character should appear at each atom in the ring indicating that these are now considered

atoms. When the atoms are added, reminimize 3-4 times before making the

measurement. ( atoms can be removed/reset by selecting "Reset" from the "Mark" menu,

checking the " atoms" box in the dialog box and clicking on [OK]. The tilde characters

should then disappear.)

3. Do you observe that the difference in Energy with and without pi electrons is similar to the

listed resonance energy in these rings? (Subtract the Energy of benzene with pi electrons

from the Energy of benzene without pi electrons).

4. Measure the C-C single bond length and the C=C double bond length in benzene, with and

without the atoms. Compare the results.

Compound EMMX Hf Hexpt Resonance Energy

C-C bond length (Ǻ)

C=C bond length (Ǻ)

benzene without

atoms N/A N/A

benzene with

atoms 19.59

pyrrole without

atoms N/A N/A N/A

pyrrole with

atoms 15.07 N/A

furan without

atoms N/A N/A N/A

furan with atoms -14.88 N/A

All experimental values from CRC 1996 edition

N

H

O

benzene furanpyrrole

36

H. Extra Credit

The Journal of Chemical Education publishes a monthly feature called "Featured

Molecules". The feature is available online at

<http://jchemed.chem.wisc.edu/JCEWWW/Features/MonthlyMolecules/index.html>. Visit the

web site and choose no less than two molecules. The molecules must fit within the following

criteria:

Published within the past two years.

No less than 4 carbon atoms.

At least one molecule must contain at least one oxygen, nitrogen, or sulfur.

At least one molecule must contain a ring structure.

Should be unique compared to other students in the class.

Use PCModel to draw and minimize the molecules (separately) and print the output as above,

including the output window. Compare your structure to that from the feature. Are any

differences merely a result of a different point of view--can you rotate the molecule to get the

same view? If the differences are more significant, resulting from energy barriers or isomers?

Why did J. Chem. Ed. choose to feature this molecule? Cite the issue fully. The J. Chem. Ed.

website also posts the molecules in a Jmol format, which is an applet that most Java-enabled web

browsers (IE and Firefox, for example) can display. The Jmol figure can be manipulated on

screen; click and drag rotates; and right-click brings up a menu of options.

5 points will be awarded for meeting the minimum criteria noted above. Additional points

will be awarded for particularly challenging molecules to reproduce.

37

NAMES: _______________________________________ LAB SECTION: ______

PARTNER: _______________________________________

Experiment 16 Report Sheet Thermochemistry: Heats of Reaction

A. Calorimeter Constant Trial 1 2 3

1. Mass of calorimeter ______ ______ ______

2. Mass of calorimeter and cold water ______ ______ ______

3. Mass of cold water ______ ______ ______

4. Temperature of cold water ______ ______ ______

5. Mass of calorimeter and hot and cold water ______ ______ ______

6. Mass of hot water ______ ______ ______

7. Temperature of hot water ______ ______ ______

8. Final temperature reached ______ ______ ______

9. Temperature change, ΔT, in hot water ______ ______ ______

10. Temperature change, ΔT, in cold water ______ ______ ______

11. Calorimeter constant ______ ______ ______

12. Mean value of calorimeter constant ______ ± ______

B. Heat of Solution

1. Mass of NH4Cl in sample ______ ______ ______

2. Moles of NH4Cl in sample ______ ______ ______

3. ΔT ______ ______ ______

4. Heat lost by solution, qsolution ______ ______ ______

5. Heat lost by calorimeter, qcalorimeter ______ ______ ______

6. Heat gained by reaction, qrxn ______ ______ ______

7. Measured ΔHsol(NH4Cl) (kJ/mol) ______ ______ ______

8. Mean value of ΔH ______ ± ______

9. Handbook value of ΔHo

f NH4Cl(aq), kJ/mol ______

10. Handbook value of ΔHo

f NH4Cl(s), kJ/mol ______

11. Calculated ΔHsol(NH4Cl) (using ΔHfo values) ______

12. Percent errorΔHsol(NH4Cl) ______

38

C. Heat of Neutralization of a Strong Acid

1. Volume of NaOH ______ ______ ______

2. Moles of limiting reagent,____ ______ ______ ______

3. ΔT ______ ______ ______

4. Heat gained by solution, qsolution ______ ______ ______

5. Heat gained by calorimeter, qcalorimeter ______ ______ ______

6. Heat evolved by reaction, qrxn ______ ______ ______

7. Measured ΔH of neutralization of HCl, kJ/mol ______ ______ ______

8. Mean ΔH of neutralization ______ ± ______

9. Percent error ______

Attach your answers to the questions to the report sheet.

39

NAMES: _______________________________________ LAB SECTION: ______

_______________________________________

_______________________________________

Submit only one report per group.

Experiment 17 Report Sheet Kinetic Study Of Reactions Of The Ferroin Complex

Results Table

Run T1 = _____ T2 = _____ n Ea

(kJ/mol) k' (s

-1) k (______) k' (s

-1) k (______)

A1

A2

B1

B2

C1

C2

D

-Shaded cells need not be filled in.

-Include temperatures.

-Provide proper units for k.

-Representative calculations must be included on the reverse of this sheet or on

a separate page.

1. Attach all graphs (properly formatted and labeled).

2. Write down the rate law for each reaction:

A)

B)

C)

(over)

40

3. Write down and explain the mechanisms for each of the reactions:

41

EXPERIMENT 14 DATA SHEET: KINETICS OF FERROIN TEMP (°C): GROUP:

A1 A2 B1 B2 C1 C2 D

Time Abs Time Abs Time Abs Time Abs Time Abs Time Abs Time Abs

42

EXPERIMENT 14 DATA SHEET: KINETICS OF FERROIN TEMP (°C): GROUP:

A1 A2 B1 B2 C1 C2 D

Time Abs Time Abs Time Abs Time Abs Time Abs Time Abs Time Abs

43

NAME: _______________________________________ LAB SECTION: ______

PARTNER: _______________________________________

Experiment 18 Report Sheet Equilibrium Studies Of The Iron(III) Thiocyanate Ion

A. Calibration Plot

1. Molar concentration Fe(NO3)3, (I) ______

2. Molar concentration KSCN, (III) ______

3. Standard Solutions 1 2 3 4 5

a. Volume KSCN (mL) ______ ______ ______ ______ ______

b. [SCN-], mol/L in std. soln. ______ ______ ______ ______ ______

c. [FeNCS2+

], mol/L (same as b) ______ ______ ______ ______ ______

d. Absorbance, A ______ ______ ______ ______ ______

e. Construct a calibration curve for A vs. [FeNCS2+

] and attach a copy.

f. Instructor's approval of graph ______

g. Your best estimate of for FeNCS2+

at 455nm ______ ± ______

B. Calculation of K

I. Set of Equilibrium Solutions

1. Molar concentration of Fe(NO3)3, (II) ______

2. Molar concentration of KSCN, (IV) ______

3. Equilibrium Solutions (Based on Table 15.2)

a. Total volume of std. sol'n ______ ______ ______ ______ ______

b. Vol. Fe(NO3)3 (mL) added ______ ______ ______ ______ ______

c. Vol. KSCN (mL) added ______ ______ ______ ______ ______

d. diluted [Fe3+

], initial ______ ______ ______ ______ ______

e. diluted [SCN-], initial ______ ______ ______ ______ ______

Note: The data tables here provide room to do the Initial-Change-Final equilibrium calculation

in all of its gory detail.

44

II. Equilibrium Calculations

Solutions 1 2 3 4 5

1. Absorbance, A ______ ______ ______ ______ ______

2. [FeNCS2+

] at equilibrium ______ ______ ______ ______ ______

from calibration curve

3. Calculations of [Fe3+

] at equilibrium

a. Initial [Fe3+

] (same as I.3.d) ______ ______ ______ ______ ______

b. [Fe3+

] reacted (same as II.2) ______ ______ ______ ______ ______

c. Final [Fe3+

] at equilibrium ______ ______ ______ ______ ______

4. Calculations of [SCN-] at equilibrium

a. Initial [SCN-] (same as I.3.e) ______ ______ ______ ______ ______

b. [SCN-] reacted (same as II.2) ______ ______ ______ ______ ______

c. Final [SCN-] at equilibrium ______ ______ ______ ______ ______

5. Calculation of Kc using equilibrium values (2.a, 3.c, and 4.c)

]][SCN[Fe

][FeNCS3

2

______ ______ ______ ______ ______

6. Average Kc _____ ± _____

*Show Calculations for Solution 1

I-C-F Table to illustrate the connections between the various values:

Fe+3

+ SCN- FeSCN

+2

Initial I.3.d I.3.e 0

Change -II.2 -II.2 II.2

Final II.3.c II.4.c II.2

IV. Question

1. Consider the reaction

A + 3B 2C + 4D

A solution was prepared by mixing 50.0 mL of 1.00 x 10-3

M A, 100.0 mL of 2.00 x 10-3

M

B, 10.0 mL of 1.0 M C, and 75.0 ml of 1.50 x 10-3

M D. At equilibrium the concentration of

D was measured and found to be 6.0 x 10-4

M. Calculate:

(a) the equilibrium concentrations of A,B,C, and D;

(b) the value of the equilibrium constant K for the reaction.

45

NAME: _______________________________________ LAB SECTION: ______

PARTNER: _______________________________________

Experiment 19 Report Sheet Determination of Total Water Hardness by EDTA Titration

A. Preparation Of EDTA Solution

1. Mass EDTA (g) ________

2. Conc. EDTA (mol/L) ________

B. Total Water Hardness

Source of hard water: ____________________

Sample 1 2 3 4

1. Initial Buret Reading: ________ ________ ________ ________

2. Final Buret Reading: ________ ________ ________ ________

3. Volume EDTA (mL): ________ ________ ________ ________

4. Total hardness (mg/L) ________ ________ ________ ________

5. Avg. Total Hardness ________ ± ________

C. Permanent Water Hardness

Sample 1 2 3 4

1. Initial Buret Reading: ________ ________ ________ ________

2. Final Buret Reading: ________ ________ ________ ________

3. Volume EDTA (mL): ________ ________ ________ ________

4. Perm. hardness (mg/L) ________ ________ ________ ________

5. Avg. Perm. Hardness ________ ± ________

6. Temporary Hardness ________

Show example calculations.

46

Questions

1. Rate the total hardness of your sample based on the scale below.

HARDNESS

SCALE

mg/L

CaCO3

equivalent

Soft <17

Slightly Hard 17-60

Moderately Hard 60-120

Hard 120-180

Very Hard >180

2. It is recommended that college age people intake 1000 mg of calcium per day. How many 8

ounce (250 mL) glasses of your hard water (assuming all the hardness is due to calcium) do

you need to drink every day to intake this quantity?

3. Water softeners soften water by replacing the Ca+2

and Mg+2

with Na+. They do this using

materials called ion exchange resins, a solid material that has pores coated with functional

groups such as –SO3-. The pores then trap the cations via ionic forces. The water softener

contains a tank filled with a saturated sodium chloride solution (called brine). When the brine is

pumped through the ion exchange resin, the high concentration of Na+ in the brine pushes the

Ca+2

and Mg+2

out of the resin and replaces it with sodium. During operation, the hard water

passes through the resin and the calcium and magnesium, having +2 charges, are more strongly

attracted to the resin and replace the sodium. Obviously, two sodium ions are needed for each

calcium or magnesium ion. Suppose a household uses 5,000 gallons per month of softened water

with the total hardness you determined. How many pounds of salt (NaCl) will the household use

to soften this water each month? (Consider the pallets of 40-lb bags of salt available at various

stores in town.)

47

NAME: _______________________________________ LAB SECTION: ______

PARTNER: _______________________________________

Experiment 20 Report Sheet Buffers And Titrations

Titration of monoprotic weak acid.

Prepare a pH titration curve for the unknown acid. Indicate which unknown acid you have on

your graph and label all axes and important points (e.g., equivalence point, etc.)

Attach answers to the questions posed in the experiment.

48

49

NAME: _______________________________________ LAB SECTION: ______

PARTNER: _______________________________________

Experiment 21 Report Sheet Voltaic Electrochemical Cells

Section D

Cell Cathode Anode Cell Potential

(Expt) (Theory)

I + II Cu Zn ______ ______

I + III ______ ______ ______ ______

I + IV ______ ______ ______ ______

II + III ______ ______ ______ ______

II + IV ______ ______ ______ ______

III + IV ______ ______ ______ ______

Section E

Cell Cathode Anode Cell Potential

(Expt) (Theory)

I + V ______ ______ ______ ______

I + VI ______ ______ ______ ______

I + VII ______ ______ ______ ______

50

51

NAME: _______________________________________ LAB SECTION: ______

PARTNER: _______________________________________

Experiment 22 Report Sheet Isolation of Copper from a 5-Cent Coin

Anode and Cathode

1. Initial mass of nickel anode ________

2. Initial mass of Cu cathode ________

3. Final mass of nickel anode ________

4. Change in mass of nickel anode ________

5. Final mass of Cu cathode ________ (wait till completely dry)

6. Change in mass of Cu cathode ________

7. % Yield of Cu on cathode ________

Observations

Record your observations during the electrolysis process.

Results

Prepare a graph of current vs. time in Excel and attach the chart to this report sheet.

Calculations

1. Total charge delivered through circuit (C) ________

2. Moles e- delivered through circuit ________

3. Mass of Ni lost from nickel coin ________

4. Moles of Ni lost from nickel coin ________

5. Moles e- needed to oxidize Ni ________

5. Mass of Cu lost from nickel coin ________

6. Moles of Cu lost from nickel coin ________

7. Moles e- needed to oxidize Cu ________

8. Total moles e- used to oxidize coin ________

Discuss your results.