CEE125 Lab Manual-Winter2015

8/10/2019 CEE125 Lab Manual-Winter2015

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CHEMICAL AND ENVIRONMENTAL ENGINEERING 125 Analytical Methods for Chemical & Environmental Engineers Laboratory

Laboratory Manual

Edition

2015

DEPARTMENT OF CHEMICAL &ENVIRONMENTAL ENGINEERING BOURNS COLLEGE OF ENGINEERINGUNIVERSITY OF CALIFORNIA, RIVERSIDE


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A N A L Y T I C A L M E T H O D S F O R C H E M I C A L A N D E N V I R O N M E N T A L E N G I N E E R S L A B O R A T O R Y

Laboratory Manual

UC Riverside, 2014Bourns College of Engineering

Department of Chemical and Environmental EngineeringRiverside, CA 92521


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Table of Contents

C H A P T E R 1

Laboratory Exercises, Organization,

and Scheduling 1

Laboratory Preparation 3

Personnel 4

C H A P T E R 2

Laboratory Conduct 5

General Rules 6

Care and Use of Laboratory Equipment 7

Care and Use of Chemical Reagents 9

C H A P T E R 3

General Considerations 11

Sources of Errors 12

Uncertainty Analysis 13

Statistical Analysis of Data 14

Population Statistics 14

Graphical Analysis 15

C H A P T E R 4

Experiment #1 Accurate volume

measurement by using burets and pipet 18

Experiment #2 - Identification of a substance

by acid-base titration 21

Experiment #3 - UV-Vis Spectroscopy-

Determination of the cobalt and Nickel

concentrations 22

Experiment #4 - AAS 23

Experiment #5 - HPLC 24

Experiment #6 - GC 26

C H A P T E R 5

Guidelines for lab report submission and

grading policy 27


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I N T R O D U C T I O N

1

INTRODUCTION

What is the purpose of Analytical Methods for Chemical and Environmental Engineers Laboratory

he course, Analytical Methods for Chemical and Environmental EngineersLaboratory, CHE & ENVE 125, is designed to provide an introduction intoinstrumental methods and their use in chemical and environmentalengineering.

To avoid crowded lab conditions and give each student as much hands-one experienceas possible, each lab section is limited to 20 students. Students will work in groups oftwo/four. Groups will stay together throughout the quarter. It is important that themembers of the group work together to complete the laboratory exercises and submit

written reports in a time efficient manner. It is strongly recommended that each groupreview the informational handouts together prior to doing the lab work, and determine

work tasks before conducting the lab. During each session each student should recordthe experimental data in her/his laboratory notebook.

All lab reports are submitted as group lab reports. Write-ups are due at 5 pm one week after the lab is conducted and are to be given to the laboratory instructor(TA). Requirements for the lab write-ups will be discussed later in this chapter.

Laboratory Exercises, Organization, andScheduling

There are a total of 7 different laboratory exercises for CHE/ENVE 125. The twolabs on basic laboratory measurement techniques and five labs on instrumental analysis

will be conducted over ten weeks.

Chapter

1 T


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The two laboratory measurement technique laboratories are:

Lab No. Topic1 Accurate volume measurement by using burets

and pipet2 Identification of a substance by acid-base titration

The four instrumental analysis laboratories are:

Lab No. Topic3 UV-Vis Spectroscopy-Determination of the

cobalt and Nickel concentrations4 Atomic Absorption Spectroscopy (AAS)5 High Performance Liquid Chromatography

(HPLC)6 Gas Chromatography (GC)

As noted previously, there will be two/four students per lab group. Unless a student withdraws from the class, the composition of each lab group will remain fixed for theentire quarter. During the first week of the quarter, groups will be determined andassigned a number.

If difficulties arise within a group, please communicate them to the faculty member incharge. REMEMBER, HOWEVER, AN IMPORTANT CHARACTERISTICTHAT EMPLOYERS ASK ABOUT IS HOW WELL A PROSPECTIVE

EMPLOYEE CAN WORK AS A TEAM . In a company you will not be able to pickthe people you work with. You must be able to overcome personal idiosyncrasies toget the job done - period.

The general laboratory schedule will be:

WeekNo.

Date Task

1 January 6, 7, 8 Introduction, lab safety training2 January 13, 14, 15 Laboratory measurement technique3 January 20, 21, 22 Laboratory measurement technique4 January 27, 28, 29 Instructions on use of instruments5 February 3, 4, 5 Instrumental analysis laboratory6 February 10, 11, 12 Instrumental analysis laboratory7 February 17, 18, 19 Instrumental analysis laboratory8 February 24, 25, 26 Instrumental analysis laboratory9 March 3, 4, 5 Presentation


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The schedule for measurement technique experiments for all groups is as follows:

LabNo.

Topic All Groups

1 &2 Laboratorymeasurement

techniques1/13 to1/22 1/13 to1/22 1/13 to1/22 1/13 to1/22

Instructions onuse of instruments

1/27,1/28 &

1/29

1/27,1/28

&1/29

1/27,1/28 &

1/29

1/27,1/28 &

1/29

The schedule for instrumental analysis experiments is as follows:

LabNo.

Instrument Group A & E

GroupB & F

GroupC & G

GroupD & H

3 UV-Vis 2/3,2/4 &

2/5

2/10,2/11 &

2/12

2/17,2/18 &

2/19

2/24,2/25 &

2/264 AAS 2/24,

2/25 &2/26

2/3, 2/4& 2/5

2/10,2/11 &

2/12

2/17,2/18 &

2/195 HPLC 2/17,

2/18 &2/19

2/24,2/25 &

2/26

2/3, 2/4& 2/5

2/10,2/11 &

2/126 GC 2/10,

2/11 &2/12

2/17,2/18 &

2/19

2/24,2/25 &

2/26

2/3, 2/4& 2/5

When you find out what your lab group number is - write it down here.

MY LAB GROUP NUMBER IS ________.

MY INSTRUMENT ANALYSIS GROUP LETTER IS ________.

Laboratory PreparationLaboratory notebook. Notes and data should be recorded with an ink pen in apermanently bound laboratory notebook. The most useful notebook is one thathas pages that makes graphing easy. Students should purchase one before thebeginning of the first exercise and use the same notebook for each experiment.Record pre-experiment notes, changes from standard procedures made during


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the course of the experiment, data, preliminary data reduction (for example,checks of a calibration curve to make sure an instrument is operating correctly),and any other observations that you may feel are interesting and noteworthy.

Why is it important to record information in a permanently bound notebook?Loose papers and pages in spiral bound notebooks are easily lost. Further, apermanently bound notebook is a journal of your in the laboratory. Journals areextremely important when legal issues such as patents and lawsuits come about.The time and activities associated with the experiment are entered sequentially.Thus, there can be no question of whether information was added at a timeother than when the experiment was conducted and that the information wasindeed collected from the experiment and not another source.

Each laboratory session requires considerable preparation . Students are expectedto be familiar with the general procedures before coming to the lab session and shouldhave her/his laboratory notebook ready to enter data. DATA SHOULD NOT BE

RECORDED ON SCRAP PIECES OF PAPER. The TAs will not be responsiblefor providing data for the experiments or making sure students have collected all of thenecessary data.

The laboratory manager and TAs will generally check that all of the equipment is ingood working order and they will make sure that all necessary gases and/or solutionsare available for the labs. The TAs will demonstrate the proper used of the equipment.However, other than ensuring that the students carrying out the lab exercises in a safemanner, the TAs will be there primarily to answer questions, not run the instrumentsfor the lab exercise.

PersonnelClass Instructor: The professor for the class is Dr. Ashok Mulchandani, his officeis in B317, his phone is (951) 827-6419, and his email address is [email protected].

Laboratory Manager

The Chemical & Environmental Engineering Laboratory Manager is Kathy Cocker.Her office is in A229 Bourns Hall and her email address is [email protected].

Laboratory Instructors The TAs for Winter 2015 are Tingjun Wu (email address: [email protected]), JustinNeal (email address: [email protected]) and Trupti Terse (email address:[email protected]).

TA Office hours: TBA


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L A B O R A T O R Y S A F E T Y A N D P R O T O C O L

5

LABORATORY SAFETY AND PROTOCOL

What to do and what not to do above all use common sense!

The Chemical and Environmental Engineering Programs are privileged to haveexcellent teaching and research laboratories in Bourns Hall. Rooms B108, B134 andB235 are the principal wet-lab teaching laboratories. B314, B316, B318, B328, B328A,

B350 and B334 are the research laboratories areas. The general research topics andfaculty responsible for the research labs are as follows:

B312 Bourns Biotechnology research laboratory Dr. Mulchandani

B314 Bourns - Nanobiotechnology - Dr. Ashok Mulchandani

B316 Bourns - Genetic engineering - Dr. Ian Wheeldon

B318 Bourns Dr. Mark R. Matsumoto

B328 Bourns - Dr. Phillip Christopher ; Dr. Xin Ge; Bacterial adhesionlaboratory - Dr. Sharon Walter

B350 Bourns-Nano electrochemical system laboratory Dr. Nosang V.Myung

B334 Bourns - Cold room (general support)

If you are interested in working in any of these areas or with any of these facultymembers, students are encouraged to contact the various faculty members.

LABORATORY CONDUCTProper conduct of everyone in the laboratories is important not only for the efficientand congenial operation of the labs, but also for the safety of all involved. Thisconduct applies to ALL STUDENTS - undergraduate, graduate, and postdoctoral.

ALL STUDENTS ALSO NEEDED TO COMPLETE AN ONLINE

Chapter

2


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SAFETY TRAINING ON OR BEFORE JANUARY 15, 2013. Student can gothrough the following link to complete their online safety training.

http://ehs.ucr.edu/training/online/lso/indexlms.html

General Rules

Clothing and shoes: Closed toe shoes and pants that cover the ankles are mandatory.Open toe sandals are not adequate protection from chemical spills. Spills andaccidents can (and do) happen. Students should not wear clothes that they are worriedabout damaging and must purchase a lab coat from the bookstore for participation inclass labs. Clothing is readily damaged as a result of chemical spillage and splashing,particularly from strong acids, bases, and redox chemicals. As an added precaution

students should wear a chemical resistant apron when handling strongacid/base/solvent chemicals.

Safety Goggles: CHEMICAL SAFETY GLASSES OR GOGGLES MUST BEWORN AT ALL TIMES IN THE LABORATORY . If you wear eyeglasses, theyshould have splash shields to protect against chemical splashing. Regular eyeglasses, bythemselves, are not adequate protection against chemical splashing. Also, certainchemicals may ruin plastic lenses. It is recommended that students purchase a pair ofchemical safety glasses/goggles from the bookstore and reserve them for their personaluse when working in the laboratories.

Eyewash stations and showers: There is an eyewash and safety shower located inthe teaching and research laboratories. In addition, drench showers are located inseveral of the research labs. Familiarize yourself with the location and use of thesesafety items.

Eating and Smoking: Eating, drinking or smoking is not permitted in any of thelaboratories.

Animals and Pets: Animals and pets are not permitted in any of the laboratories.

Refrigerator and Ovens: Refrigerators, incubators, and ovens located in thelaboratories are not to be used for storing or preparing food.

Flames: Open flames should be placed in a fume hood if possible and always on anon-flammable surface away from combustible material. Never leave open flamesunattended in the lab.

Chemical Spills: Small spills should first be neutralized: sodium borate for base spillsand sodium bicarbonate for acid spills. After neutralizing mop or sponge up spillsimmediately. Large spills should first be contained with an absorbent material such as

Please read theserules thoroughly.They are veryimportant inensuring thatstudents have asafe labexperience.
http://ehs.ucr.edu/training/online/lso/indexlms.htmlhttp://ehs.ucr.edu/training/online/lso/indexlms.htmlhttp://ehs.ucr.edu/training/online/lso/indexlms.html


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vermiculite and then neutralized. Additional absorbent may then be added to take upthe neutralized liquid and picked up. A faculty member or the Laboratory Manager,and Environmental Health and Safety (25528) should be notified when a large spilloccurs.

Volatile Organics: A fume hood should be used when using or dispensing a volatileorganic reagent. If the reagent is to be regularly used or dispensed for a project, asadditional protection, an appropriate respirator should be purchased, fitted, used, andregularly maintained. Respirators should not be shared; they are to be purchased,fitted, used, and maintained by one person. Environmental Health and Safety will fitand test respirators free of charge.

Pipetting: NEVER pipet any solutions by mouth. Pipet with a pipet bulb or apipettor. After using any pipet, please place it in a pipet storer for subsequent washingin a pipet washer.

Gas cylinders: Pressurized gas cylinders should be strapped or chained to a benchtop or wall. Before moving cylinders always remove regulators and screw on the cap.DO NOT attempt to change regulators without prior training. Depending on the gastype, regulator threading and connections vary to prevent mixing of incompatiblematerials. Empty gas cylinders should be returned to the supplier as soon as possible.

Chemical waste disposal : Chemical wastes, spent and old reagents, and effluentsfrom bench-scale reactor systems SHOULD NOT BE DISPOSED INTO THEFLOOR DRAINS OR SINKS! Before beginning your laboratory experiment, check

with a faculty member of the Laboratory Manager regarding proper disposal ofexpected wastes. Environmental Health and Safety will collect and dispose of

hazardous wastes upon request.Daily departure : Check your work area when you leave for the day to be sureeverything is clean and neat. If you are the last person in the room, check all sinks inthe room to make sure the tap water is turned off. Make a cursory glance around theremainder of the laboratory to see if there are any major problems. If you are the lastone to leave for the day, please check each lab to see that all tap water is off, that thereare no major problems, and that all doors are locked. As you leave the laboratory

TURN OFF THE LIGHTS AND LOCK THE DOORS.

CARE AND USE OF LABORATORY EQUIPMENT

Many of the analytical instruments and much of the laboratory equipment in theChemical and Environmental Engineering Laboratories are commonly used for bothteaching and research. Therefore, it is imperative that each student use and maintaininstruments and equipment properly.


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BEFORE USING ANY ANALYTICAL INSTRUMENT

Read the instruction manual or obtain training by qualified personnel on the use, care,

and maintenance of the instrument . Please contact the Laboratory Managerregarding instruction manuals or training.

Failure to use and maintain instruments properly will lead to poor laboratory resultsand jeopardize the progress of important research projects. Students who use andmaintain of laboratory instruments and equipment improperly may be subject todisciplinary action.

From time to time, students may experience problems when using some of theanalytical instruments. When problems occur, they should be discussed with theLaboratory Manager. DO NOT ATTEMPT TO "FIX" THE INSTRUMENTS

WITHOUT CONSULTING WITH A FACULTY MEMBER OR THELABORATORY MANAGER.

Balances: Balances and their surrounding areas should be cleaned using a brush aftereach use. Residual traces of reagents, liquids, etc. should not be evident. Theexperiment of the next person using the balance may be ruined by your laziness andlack of consideration.

pH Meters: pH meters are available in various laboratory rooms. They are not to bemoved from the room without permission from the Laboratory Manager or facultymember. The pH probes should not be used in harsh solutions or solutions that may

foul the probe. After use, the probes should be rinsed and placed in a neutral buffersolution for storage; pH meters should be placed in a stand -by mode.

Ovens and Furnaces: Convection ovens are primarily for reagent desiccating andsolids/moisture analyses, and are typically set at around 100 to 110oC. Muffle furnacesare primarily used for volatile solids analyses and are set at around 550oC. Do notadjust the temperatures of ovens or furnaces without consulting with the other users.

Autoclaves: In addition to small autoclaves located in several of the researchlaboratories, a large autoclave for sterilizing glassware and culture media is located inB358 Bourns Hall. Students needing to use this autoclave should consult with theLaboratory Manager before use.

Fume hoods: The Chemical and Environmental Engineering Laboratories containtwo types of fume hoods: canopy (elephant trunk) and sash. Sash-type fume hoodsare to be used for making up strong acid/base reagents, dispensing volatile chemicals,and performing digestions and extractions. When using sash-type fume hoods, theglass screen should be lowered at all times, except when placing equipment and orchemicals inside. Always prepare reagents with the glass screen lowered, wearing


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goggles at all times. DO NOT STORE EQUIPMENT, CHEMICALS ORREAGENTS IN SASH-TYPE FUME HOODS. Canopy fume hoods are to be used

when hazardous volatile vapors may be emitted from a bench-scale laboratoryexperiments that runs for long periods of time.

Dishwashers: There are various laboratory dishwashers located in the labs to be usedfor glassware cleaning. Instructions for their use can be obtained from the LaboratoryManager. Often, however, glassware will need to be washed by hand. When washingglassware, etc. by hand always wear goggles and gloves. You may not know whatresidual chemicals may be present in dirty glassware. Do not store dirty glasswarearound the sinks. Wash them first before leaving them to dry around the sink. This

will prevent an accident occurring when someone else picks up the glassware.

WHEN USING CHROMIC ACID OR OTHER DILUTE ACID SOLUTIONS TO WASH GLASSWARE, BE SURE TO CLEAN THE SINKS, FLOORS, ANDSURROUNDING AREAS THOROUGHLY. YOU MAY CAUSE THE NEXTPERSON TO HAVE SERIOUS BURNS AS A RESULT OF YOURNEGLIGENCE!

Borrowing: Environmental Engineering laboratory instruments and large equipmentshould not be moved from room to room. If there is a need to do so for yourresearch, obtain permission from a faculty member or the Laboratory Manager.EQUIPMENT OR SUPPLIES OF ANY KIND MAY NOT BE BORROWED ORREMOVED FROM THE LABORATORIES FOR USE BY OTHERDEPARTMENTS WITHOUT FIRST FILLING OUT A DEPARTMENTALEQUIPMENT LOAN FORM. SEE THE LABORATORY MANAGER FORPERMISSION AND THE NECESSARY FORMS. DO NOT LOAN

EQUIPMENT OR SUPPLIES TO NON-CHEMICAL/ENVIRONMENTALENGINEERING FACULTY OR STUDENTS WITHOUT CONSULTING WITH THE LABORATORY MANAGER.

CARE AND USE OF CHEMICAL REAGENTS

Dry chemicals are separated generally into two categories: organic chemicals andinorganic chemicals. Strong liquid acids and bases are stored separately in cabinetsunder fume hoods. Volatile liquids are stored in cabinets which have exhaust ventbuilt in to carry away any off-gases.

Labeling: When new reagents are received, either for general lab use or for a specificproject, mark each bottle or jar of chemical with the month and year received, and yourinitials (e.g. Rec'd 10/96 MRM). Also mark the bottle or jar when the chemical is firstopened (e.g. Open 12/96 MRM). Use labeling tape (not masking tape) or adhesivelabel. Grease pencil, or other non-permanent marker, is not acceptable; labelinginformation is easily erased.


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Dispensing: When weighing reagents, use an intermediate container. Carefullydispense the approximate amount of reagent you'll need into the intermediatecontainer first, then transfer the reagent onto the weighing vessel or paper in thebalance. Do not return excess chemical (in the intermediate container) back into the

reagent bottles.

Strong Acids and Bases: Liquid acids and bases should be dispensed in a sash-typefume hood. Carry acid/base bottles in the rubber acid/base carrier, or use a cart.Never carry acid/base bottles by the handle or neck. When holding an acid/basebottle, always have one hand under the base of the bottle. Wear goggles, apron andgloves when dispensing and mixing strong acids or bases. Mix strong acids or bases ina Pyrex or Kimax flask or beaker. Ordinary flint glass reagent bottles will crack fromthe heat. Add the acid or base to water in small incremental amounts over time.

ALWAYS add concentrated acids or bases to water. NEVER add water toconcentration acids or strong bases!!

Storage and Labeling of Reagent Solutions: Reagent solutions should be preparedusing volumetric flasks or graduated cylinders. However, solutions should NOT bestored in them. After a reagent solution is made, it should be placed in a clean,appropriately sized reagent bottle. The reagent bottle should then be labeled with thefollowing information: contents, date of preparation, preparer's initials, project,disposal date (date beyond which reagent should be discarded), and other special

warnings (e.g. flammable, volatile, extremely caustic, etc.). An example is: 0.1 MSodium Hydroxide, Caution, Corrosive, MRM, Prep. 11/1/14, Dis. after 2/1/15.Improperly marked reagents must be assumed to be old and will be discarded.

Water: There are three kinds of water available in our laboratories:

Tap water: Water at the sinks is regular water from the municipal water supply.However, because there are many chemicals in use and the possibility of backflushingexists, all of the taps are marked, Industrial Water - Do Not Drink. If you wantdrinking water, please use the drinking fountains near the lavatories.

Reverse osmosis (RO) water - This water is available from the special taps markedDI at each sink. This water is very high q uality and is adequate for most reagentpurposes.

Nanopure water - This water is made by taking RO water and passing it throughactivated carbon, two mixed bed ion exchange columns, and a 0.2 micron filter. This

water is the highest quality water available in the Chemical and EnvironmentalEngineering laboratories, and should be used sparingly, for mixing high purity reagentsand standards, and for final rinsing of special glassware.


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D A T A A N A L Y S I S B A S I C S

11

DATA ANALYSIS BASICS

Some form of analysis is required on experimental data. The analysis may be avery simple qualitative assessment about an observed trend or it may involvecomplex error analysis coupled with a statistical analysis to determine the

probability of true differences between experimental data sets.

While the ability to carry out experiments and collect data is important, the usefulnessof conducting experiments depends on careful analysis of the collected data. Withoutanalysis, an experiment is merely a work task. Data analysis can be used for a variety ofpurpose such as determining 1) whether collected data are reasonable, 2) theuncertainty associated with the measurements 3) whether significant differences in datasets exist as a result of changed operating conditions, and 4) empirical mathematicalmodels for relationships between different parameters. However, the analysis ofexperimental data is an acquired skill that improves (hopefully) with experience. Oneof the purposes for this course is that students begin to develop these skills.

General Considerations A good outline that can be used for experimental data analysis has been developed byHolman1 (1994).

1. Examine data for consistency. Are the measurements reasonable? This basic questionis the common sense approach to experiments. A simple example is when you fillup your car with gasoline, you expect your gas gage to read Full right after. If itdoesnt, you suspect something is wrong like the gage is broken, your gasoline tankleaked, or the pump wasnt working correctly.

This same logic applies to engineering experiments. When you bubble pureoxygen gas through water that is not saturated with oxygen, you would expect thatdissolved oxygen concentration to increase, not decrease or stay the same. Why doyou know this? Based on mass transfer considerations (of course!).

1 Holman, J.P. Experimental Methods for Engineers , 6th ed., McGraw-Hill, Inc., San Francisco, 1994.

Chapter


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To use this common sense approach it is important that the experimenter befamiliar with the expected trends/readings based on theory and/or pastexperience. You dont want to continue doing an experiment i f you are collectingbad data. If you know beforehand what to expect, this type of situation can be

avoided. The more thorough the understanding of what is expected based ontheory and/or experience prior to the start of an experiment, the more likely it isthat the experiment will be successful.

2. Perform a statistical analysis of data where appropriate . When measurements are repeatedseveral times, statistical parameters such as mean, median, and standard deviationare useful in evaluating the level of precision for a particular measurement, andlevel of confidence for a given data set.

3. Estimate uncertainties in the results . All instruments that measure something have anuncertainty associated with them. For example, when a thermometer reads 100 oC,is it accurate to 1oC or 0.1oC. If the temperature reading is used in conjunction foranother parameter such as heat content, then the temperature uncertainty carriesover to heat content as well. Generally, these types of uncertainties can beestimated before the experiment is conducted.

4. Anticipate results from theory . The theory or theories relevant to the experimentsubject should be carefully reviewed to determine what trends may be expectedbefore the experiment takes place. This step is particularly important indetermining an appropriate graphical presentation of the experimental data. Forexample, if a first-order system is subjected to a step input, a semilog plot of thedata should result in a linear plot. Use of dimensionless parameters (e.g. Reynoldsnumber, Peclet number) may also provide important insights.

5. Correlate the data. The experimental data should be interpreted in terms of physicaltheories or the basis of previous experimental work (done by others). The resultsshould be examined to see if they conform to or differ from previousinvestigations or standards.

Sources of ErrorsErrors occur in all experiments. Some of the errors can be avoided while otherscannot. Most of the errors that can be avoided are due to uncontrollable variables,and/or lack of experience or carelessness on the part of the experimenter. These typesof errors can be avoided by carefully reviewing each step and condition (variable) in anexperiment and assessing whether they can significantly affect the outcome of theexperiment. If so, then the experimenter should alter the experiment, or pay particularattention to certain aspects of the experiment, to ensure that a gross error does notoccur. As the saying goes, An ounce of prevention is worth a pound of cure. This


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means that time spent preparing an experiment is well worth the effort. A great deal oftime and money can be wasted as the result of poor planning.

Beyond these controllable errors, there are errors of uncertainty. These are errors

that are beyond the control of the experimenter. There are two principal uncertaintyerrors, fixed and random. Fixed, systematic, or bias errors are errors that are generatedrepeatedly by the same amount for an unknown reason. For example, a ruler used tomeasure length indicates a length of 1 m. However, the ruler actually measures 0.99 m

when compared to the actual standardized 1 m length. Thus, the ruler always measures1 cm short per m measurement. These types of errors are often unknown. Calibrationof an instrument to an absolute standard, such as National Bureau of Standards (NBS)standards, is the best way to detect and/or avoid systematic errors.

The second type of uncertainty errors is random errors . These errors are caused by a variety of reasons that cannot be avoided such as experimentalist bias, fluctuations ininstrument readings, minor temporal variations in variables, etc. Every measurementhas a random uncertainty associated with it. This uncertainty is often related to theaccuracy of the instrument. For example, a pH probe may have an accuracy of 0.01pH units within the pH range between 2 and 12. This means that, properly calibrated,that this particular pH probe is accurate to within 0.01 pH unit between pH 2 and pH12. Outside of those pH ranges, the pH probes accuracy may or may not fall withinthat specification.

Uncertainty (Error) Analysis Whenever a measurement is made there always is some uncertainty. The instrument

manufacturer may define this uncertainty, or may be estimated by the experimenter(based on experience). Whatever the case, these measurement uncertainties are carriedon when a calculated result is generated. Many measurement uncertainties may beassociated with a single calculated result. The overall uncertainty for the calculatedresult is a function of the error associated with each measurement. In general, thisoverall uncertainty can be calculated as:

21

22

22

2

11

nn

T e x R

e x R

e x R

E

where R = function of the independent (measured) variables, x i = independent(measured) variable i , e i = uncertainty in measured variable i , and E T = overalluncertainty in calculated function R .

As a simple example, consider the volume of a rectangular box that is determined bymeasuring its dimensions with a ruler that has an accuracy of 0.2 cm. The measured


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dimensions are L = 45 cm, W = 60 cm, and H = 20 cm. Based on thesemeasurements, volume would be 54,000 cm3.

To determine the uncertainty of the volume:

2

2

2

700,24560

9002045

200,12060

cm LW H V

cm LH W V

cmWH LV

LWH V

E T 1,200 cm 2

0.2 cm

2

900 cm 2

0.2 cm

2

2,700 cm 2

0.2 cm

2

12

620 cm 3

Statistical Analysis of Data The purpose of this section is to not to provide a comprehensive overview of statisticaldata analysis, but rather to review important concepts and outline appropriateapplication of statistics to experimental data. Most of this information has beencovered in previous courses. More in depth coverage of statistical data analysis can be

obtained from course work or various textbooks.Population Statistics

When a set of repeated measurements is made, the individual readings will vary fromeach other. Most often statistical measures are used to describe the entire set ofmeasurements in terms of a centralized number, the spread of the data, and frequencyof distribution. Typical parameters include:

Arithmetic mean (or average) -n

ii xn

x1

1

Median- middle data point of a sequentially ordered data set. The datum for which halfof the data points in the set are higher and half are lower in value is the median.


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Standard deviation - descriptor of the spread of the data compared to the mean =

21

1

2

1n

x xn

ii

Confidence interval - the probability that the actual mean value lies within a certainnumber of values around an experimental mean. As an example, if a measured flowreading has a mean of 100 and a standard deviation of 5, the 95% confidence interval

would be 100 1.96(5) = 100 9.8. In other words, there is a 95% probability thatthe actual mean value is between 90.2 and 109.8.

Chauvenets criterion - sometimes one or two data points seem to be very differentcompared to all of the other data points in a population. While it is logical to throw

out these types of data points, it is possible to apply a statistical test, Chauvenetscriterion, to determine whether data may be discarded. To apply this criterion, thedeviation of each data point from the mean must be calculated and divided by thestandard deviation: / x xi . The calculated value is compared to Chauvenetscriterion, which is a function of the number of readings in the population.

Number oftotal readings 3 4 5 6 7 10 15 25 50 100

Max.deviation,

/max x xi

1.38 1.54 1.65 1.73 1.80 1.96 2.13 2.33 2.57 2.81

Graphical AnalysisExperimental scientists and engineers are well known for the use of graphs to highlightcertain data trends and insights. However, random graphing of data usually generatesan excess of charts that are useless. Considerable thought must be given to thephysical phenomena involved in each experiment before preparing a plot. The person

who understands the physical processes (the theory) is usually the person who canmost successfully present experimental data graphically.

The most common graphical technique is the correlative graph in which therelationship between two variables is plotted in a linear manner. To do this, theexperimenter must know what type of function will best describe the data. Thisknowledge is based on theoretical understanding of physical phenomena.

A summary of plotting methods for various functions to obtain straight lines.


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Function Plotting Method Slope Y-interceptbax y y vs. x on linear paper a b

bax y log y vs. log x on log-log paper b log abxae y log y vs. x on semilog paper b log e log a

bxa x y

y

1 vs. x

1 on linear paper a b

2cxbxa y 1

1

x x y y vs. x on linear paper c b + cx 1

cbxa

x y

1

1

y y x x vs. x on linear paper

1

2

xa

bb a + bx 1

2csbxae y

11

1

log x x

y y vs. x on semilog

paper

c log e b + cx 1 log e

bxe y 1

y11

log vs. x on semilog

paper

b

xb

a y y vs. 1/x on linear paper b a

xba y y vs x on linear paper b a

The best method to determine the slope and y-intercepts for these various plots is theuse of the least squares method of linear regression, which is found in many standardplotting software packages such as Excel.


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L A B O R A T O R Y E X E R C I S E S

17

LABORATORY EXERCISES

This chapter contains summaries of the laboratory exercises that CHE and ENVE 125 students will be conducting during this course.

As noted previously, there are a total of 10 different laboratory exercises forCHE/ENVE 125. The four labs on basic laboratory measurement techniques and sixlabs on instrumental analysis will be conducted over ten weeks.

The three laboratory measurement technique laboratories are:

Lab No. Topic1 Accurate volume measurement by using burets and pipet2 Identification of a substance by acid-base titration

The five instrumental analysis laboratories are:

Lab No. Topic

3 UV-Vis Spectroscopy: Determination of the cobalt andnickel concentration

4 Atomic Absorption Spectroscopy (AAS) 5 High Performance Liquid Chromatography (HPLC)6 Gas Chromatography (GC)

To reiterate there will be two students per lab group for laboratory measurementtechnique experiments and four students per lab group for instrumental analysisexperiments.

Students are strongly encouraged to review the relevant sections in their texts prior to

conducting each laboratory exercise

Chapter

4


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E X P E R I M E N T S

18

Exercise # 1:

This lab period is designed to ensure precise and accurate use of basic laboratorymeasurement techniques. These techniques will be needed throughout the rest ofthe laboratory course and must be mastered to ensure the success of futureexperiments.

1. Burets: Burets measure the volume of fluid delivered. The delivered volume is calculated as the difference of the initial and final buret readings.(It is noted that always starting from 0.00 on the buret may lead to a biaserror if the first graduation mark is miscalibrated.) Sources of errorinclude:

I. Linear interpolation error in initial readingII. Linear interpolation error in final readingIII. Limiting variations of the true volume due to non-

uniformity in the bore of the buret, temperaturefluctuation during measurement, non-uniformity ofdrainage

IV. Determinate error (user error): Grossreading/recording errors, bias (preference of evendigits, 0s or 5s)

a. Fill your buret with temperature-equilibrated deionized water. Take an initial reading.b. Deliver approximately 5 mL of water to a pre-tared container.c. Record the buret reading. (Ensure that any excess water on the tip

of the buret is transferred to the weighing vessel by gently placingthe vessel to the tip of the buret.)

d. Record the final weight of the vessel.e. Deliver approximately 7 mL additional water to the weighing

vessel.f. Record the buret reading and new weight of the vessel.g. Deliver approximately 10 mL additional water to the weighing

vessel.h. Record the buret reading and new weight of the vessel.

Assuming the sample sizes are not too small, the relative standarddeviation of this experiment should be 1 to 2 %. You have used amass balance with much higher precision than the volume reading and

we will assume therefore that the weight measurement is exact based


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on the number of significant figures in the reading. Therefore, youshould calculate the relative standard deviation by:

i. Converting volume delivered by buret to mass delivered. (Consult

with your lab T.A. on the temperature of the water. The T.A. willprovide you with a water density chart based on watertemperature.)

ii. Calculating mass difference between buret measurement andbalance measurement for each delivered volume. (DM)

iii. RSD ((

M 1

W 1

)2

3

( M

2

W 2

)2

3

( M

3

W 3

)2

3)

12 where W is the weight

determined by the mass balance.If the RSD value is greater than 0.002 repeat the experiment. If you

fail again to achieve an RSD < 0.002, contact the TA for advice. Ifyour RSD is less than 0.002, have the T.A. initial that you havecompleted this portion of the experiment.

2. Pipets. Pipetting is a valuable technique to deliver/transfer knownquantities of liquid. Pipetting is generally a more precise technique for

volumetric delivery than a buret if the volume to be delivered is known apriori. Errors in pipetting include:

I. Linear interpolation of initial reading (Note: pipets only have oneof these errors, burets have two)

II. Variability in drainage, temperature changes, and variations in

the size of the drop remaining in the pipet tip.III. Gross user error.It is important to always note the type of pipet used. The most commontype of pipet is the to deliver style. These are typically designated on thepipet as td.

These pipets are designed to drain with gravity as the driving force and willalways have a small quantity of fluid left in the tip. Therefore, remainingfluid should not be delivered using the pipet bulb.

a. Fill a pipet (5 or 10 mL) with temperature-equilibrated deionized water.Deliver the fluid to a pre-tared vessel. Measure the final tare weight.

b. Repeat step a 2 times. (total of 3 measurements)c. Repeat step a. This time use the pipet bulb to deliver all fluid inthe pipet. What is the error in delivering the full amount?

d. Calculate the relative standard deviation for your pipet work. TheRSD should be below 0.0015. If not, repeat experiment. If theexperiment still fails, contact your T.A.. Your T.A. will help youdetermine the source of errors and correct them. Once you have


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obtained a RSD below 0.0015, have your T.A. sign off on yourpipet abilities.

3. Put your above skills to use:a. Prepare a 0.25 M aqueous solution of nickel(II) nitrate

hexahydrate, Ni(NO 3 ) 6H2O. (MW = 290.81 g mol-1

) using ananalytical balance, 50 mL volumetric flask (contains 50.0 mL atcalibration mark), and distilled water. Calculate the solutionconcentration made to the appropriate number of significantfigures. (Note: you are aiming for approximately 0.25 M solution,you tell me the exact concentration you made.)

b. Pipet 5 mL of your Ni 2+ solution into a 50 mL volumetric flaskand dilute to 50 mL. (calibration mark is 50.00 mL; a 10 mL pipetdelivers 10.00 mL fluid)

c. Transfer the Ni 2+ solution to a disposable cuvette. Measure the visible light absorbance of the solution at 658 nm. Use distilled

water as a blank. Your T.A. will help you with this measurement.4. Report: Your report need only consist of your T.A. signatures that youcompleted the buret and pipet training, the concentration of your Ni 2+ solution (with appropriate number of significant figures), and theabsorbance of your solution and blank.


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21

Exercise #2 : Determination of the concentration of KHP insolution (Potassium Hydrogen Phthalate) in an unknown.

The unknown concentration of KHP in an aqueous solution will be determinedby titration with a standardized solution of NaOH. The equivalence point for thetitration will be determined using phenalphthalein as a color indicator. (Faintestpink possibly perceptible).

During the first part of this experiment you will make 0.25 M NaOH andstandardize it against a primary KHP standard. The second part of theexperiment will use the standardized NaOH to determine the concentration ofKHP in the unknown sample.

You will be provided with pre-dried KHP of a stated purity. Keep the KHP inthe dessicator as much as possible to prevent the KHP from picking up moisturefrom the laboratory air. Prior to coming to lab, determine the approximatemass of KHP you will dissolve with 50 mL of water so that you will require35-40 mL of 0.25 M NaOH to neutralize. Also be sure you know how tocalculate the amount of 6 M NaOH to dilute to obtain 500 mL of 0.25 MNaOH.

1. Make 500 mL of approximately 0.25 M NaOH solution.

2. Accurately weigh out (record actual mass) your calculated amount of KHP anddissolve into approximately 50 of de-ionized water. Use some of your dilution

water to help transfer any residual KHP in the weighing tray to solution. Also, besure to note the stated purity of the KHP for your later calculations. Add 1-2drops of phenolphthalein to the KHP solution. Use your buret to accuratelydeliver the NaOH until you have the faintest pink possibly perceptible. Be sure torecord the initial and final volume.

3. Repeat step 2 for a minimum of three total trials. (The greater the number oftrials, the more confident you can be about your measured concentration.)

4. Obtain from the TA your unknown KHP solution. Use a small portion of theunknown for a sacrificial titration so you can estimate the volume of theunknown necessary so that you use approximately 35-40 mL of NaOH when

titrating. Perform a minumum of three titrations to determine the molarity of theunknown.

5. Report: The molarity of KHP determined for each trial, the average, and thestandard deviation.


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Exercise # 3: Determination of the Cobalt and Nickelconcentrations using spectrophotometry. (Adapted fromNJIT Chem 221 lab manual)

EDTA will be used to form a stable (colorful) complex with cobalt and nickel.EDTA reacts with both of these metals at pH in excess of 4. You will makecalibration solutions for cobalt and nickel separately and determine theirabsorption spectra. This will help identify the ideal wavelengths for measurementof the cobalt/nickel mixture. Using beers law and a linear combination ofequations you may determine the concentration of both components in theunknown solution.

Procedure:

1. Pipet duplicate 40 mL aliquots of Ni and Co standard samples into four100 mL volumetric flasks. Add 10 mL of buffer (1 M NH 4Cl, 1 M NH 3 in

water, prepared in advance by your T.A.) to each flask. Add 1.6 gdisodium salt EDTA. Stopper and warm flasks on a hot plate for 20minutes to ensure complete formation of the complex. Cool and dilute to

volume. Prepare a blank containing 12 mL buffer solution, 1.6 g disodiumEDTA in 100 mL of solution.

2. Use the spectrophotometer to scan the absorbance of each solutionbetween 350 to 650 nm. From the curves, determine the optimal

wavelengths to measure cobalt and nickel at.

3. Pipet duplicate 40 mL aliquots of the unknown solution into two 100 mL volumetric flasks. Add 3.8 g EDTA and 10 mL buffer, warm for 20minutes, and measure the absorbance of each of the standards at the two

wavelengths determined in step 2. Make at least five readings at each ofthe wavelengths.

4. Report: Concentration of cobalt and nickel in the unknown solutiondetermined for the duplicate unknowns.


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Exercise # 4: Atomic Absorption Spectroscopy Atomic Absorption Spectroscopy (adapted from NJIT lab manual)

Flame atomic absorption spectroscopy is widely used for analysis of mostmetals because of its simplicity, effectiveness, and relatively low cost. In thislab we will use flame AAS to determine the sodium content in an unknownsolution, and in some snack foods. Sodiums characteristic wavelength for AAanalysis is 589 nm.

Procedure:

1. Make 200 mL of dilute nitric acid (HNO 3 ) by a 1:1 dilution ofconcentrated HNO 3. Prepare 5, 10, 15, and 20 ppm Na standard solutionsby diluting your stock solution (concentration given on bottle) withdeionized water. You dilute nitric acid will serve as your blank.

2. Unknown. Obtain your unknown from your lab T.A. The T.A. willinstruct you on how to use the instrument. First, measure the absorbanceof the blank, then the standards starting from lowest to highestconcentration. Measure the absorbance of the blank again beforemeasuring your sample.

3. Snack food determination. You need to bring some snack food for thislab. Make sure you look at the snack food label. First you must getthe snack food into the appropriate form for analysis. Grind and mixsome of the snack food you have brought. Weigh out triplicate 0.50 gsamples into 200 mL Erlenmeyer flasks. Add ~50 mL of dilute HNO 3.

Place on hot plate in fume hood and bring to a boil. Simmer for 30minutes. Cool and transfer (quantitatively) your solution to a 100 mL volumetric flask. Dilute to the mark with distilled water and mixthoroughly. Filter each solution through filter paper into a clean, dry 100mL flask. Measure using the AAS. If the value is out of range (high),dilute and repeat. You should do this for three separate snack foods ofyour choice.

4. Report: Sodium in unknown sample (ppm). For the snack food report thesodium as a percentage of the food. Be sure to compare to value onpackage.


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Exercise # 5: High Performance Liquid Chromatography An HPLC analysis of the artificial sweetener, aspartame, in beverages.

SCOPE AND APPLICATION This analytical procedure is for the identification and quantification of aspartamepresent in an artificially sweetened beverage.

SUMMARY OF METHOD For this lab, you will use an Agilent high performance liquid chromatograph (HPLC)equipped with a DAD detector to identify and quantify the concentration ofaspartame. You will use a calibration standard to identify the retention time ofaspartame and generate a calibration curve.

The HPLC sample injection, column, and operating conditions will be set up priorto the lab. We will use a 10mM Potassium phosphate dibasic (pH 6.3, adjusted

with phosphoric acid) mobile phase buffered at a flow rate of 1.0ml/min. Thedetector wavelength will be set to a single channel at 210 nm.

EQUIPMENT AND SUPPLIES

Agilent 1200 HPLC system: Vacuum DegasserQuatenary PumpStandard AutosamplerDiode Array Detector

Agilent Chemstation Software Agilent ZORBAX SB-C18, 5 um, 150 mm 4.6 mm Agilent LC Setup per SAE 930142Required Chemicals:

Water (HPLC grade)Potassium Phosphate Dibasic (HPLC grade)Phosphoric Acid (HPLC grade)

Procedure:

1. You will be provided with pure aspartame to generate your calibrationsolutions and determine the retention time of aspartame. Using serialdilutions, you will make 5 solutions in a range of concentrations for yourcalibration curve. You should have an idea of what range to calibrate for.

You will use methanol as your solvent. Inject these into the HPLC.


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2. Using the HPLC software, integrate the each chromatogram to determinethe peak areas of aspartame at each concentration. Generate a calibrationcurve with this data.

3. You will need to bring in an artificially sweetened beverage that

contains aspartame (Nutrasweet).4. Bring the beverage to room temperature. If the beverage is carbonated, it will need to be degassed by letting it stand out for a few hours. Filter~10ml of the beverage into a clean labeled vial. Transfer ~2ml of this

volume to autosampler vials.5. Inject the sample into the HPLC.6. Using the HPLC software, integrate the chromatogram to determine peak

area of aspartame and quantify it using your calibration curve.


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Exercise # 6: Gas Chromatography You will use the gas chromatograph (GC) to identify and quantify theconcentrations of three organic compounds. In this lab you will be given a small-capped vial of the unknown and a choice of four possible organic compounds.Based on the retention time index of each compound you should be able toidentify the unknown species. You will then produce a calibration standard toidentify the concentration of the unknown species.

Procedure:

7. The possible organic compounds in your unknown are cyclohexane,benzene, toluene, and heptane. Note: The GC has an auto-injector that

will inject 1 mL of a given compound into the system. You will usemethylene chloride as your solvent. The unknown mixture concentrations

are in the range of 50 ug/mL to 250 ug/ml.8. Before coming to lab, develop a strategy to identify yourcompounds.

9. The TA will show you how to use the instrument, the separation columnused, and the temperature program that will separate these compounds.

10. Prepare calibration standards for the compounds identified. This is doneby serial dilution of the stock hydrocarbons. If you semi-quantitativelyperformed step 2, you should have an idea what range to calibrate for. Aminimum of three points is necessary for a good GC calibration.

11. Report: identity of unknowns and their concentrations.


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27

GUIDELINES FOR LAB REPORTPREPARATION AND GRADINGCRITERIA

This chapter contains the guidelines for Lab report submission of the laboratoryexercises that CHE and ENVE 125 students will be conducting during thiscourse.

General Rules:- The group grade for all lab reports will be worth 50 points . The point break down

for each section is as follows:o Front Matter: 2 pointso Introduction/Background: 10 pointso Experimental Apparatus and Procedures: 10 pointso Results and Discussion: 15 pointso Conclusion: 6 pointso References and Appendices: 2 pointso Xerox Copies of Laboratory Notebook: 5 points

- All reports must be prepared using a word processing system such as Microsoft Word orcomparable. Figures should be prepared using Excel or similar. Tables should beprepared using Microsoft word as well. HANDWRITTEN WORK SHOULD NOTBE GRADED.

- An individual grade for each member of the group will also be assigned based upon thequality of their contribution to the report. This grade will also be out of 50 and theaverage of the individual and group grade will represent the students overall grade for thelab report [ Average of the individual = 50% individual grade + 50% of the groupgrade ]. If more than one-person works on a section, both will receive the same individualgrade for that section. This total out of 50 should be determined from the sum of thepoints earned by each member on their respective sections.

- ALL writing should be in complete sentences with appropriate grammar and spelling.

Chapter


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- Writing should be in the third person and the past verb tense should be used.

- Writing should be specific and concise (not rambling, redundant and repetitive).

- There should be no blank or free space anywhere in the report.

- All equations should be numbered.

- In total, the reports for experiments in which an experimental protocol was providedshould be no more than 10 pages of written text. Note these page limits are not a requirement. In total, the written portion (Intro, Experimental, Results and Discussion, Conclusions,and References) should not exceed these limits. The front matter (Title, Table ofContents, List of Table and Figures) does not count toward this total, nor do Figures and

Appendices.

- Pages should be numbered. Additional details: the cover should not have a page number;the table of contents and list of tables and figures should be pages i and ii, respectively;the first page of your report is 1 and all subsequent pages are number in the appropriateprogression.

Section Grading Criteria:

1. Front Matter (2 points):

- Does the report include a:- Cover page that identifies the experiment number and title, the due date of the

report, and the group number and group members.- A table of contents that lists all the section headers and the page in the report

where that section is located. The table of contents should also indicate whichmember of the group contributed to each section.

- A list of tables/figures including the appropriate table/figure number, table/figuretitle, and the page in the report where the table/figure can be found.

- Are these items located at the front of the report (the first 3 pages; note, these do notcount against your page total).

2. Introduction and Background (10 points):

- Generally, the introduction should provide:

o a clear statement of the goal and objectives for the experiment o background information that is needed to understand the remainder of

the report.

o additional references to pertinent literature related to the project. - All equations and topics that are not common knowledge shou ld have references.

3. Experimental Apparatus and Procedures (10 points) :


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- This section should provide sufficient information on the apparatus andexperimental procedures.

- It should be written in the PAST TENSE (e.g., we measured not we measure

- It should not be a copy and paste of the laboratory manual. Without a reference,this is plagiarism.

4. Results and Discussion 15 points) :

- This section should give the results of the experiments in tabular and/or graphicalform. Each table and figure should be numbered (e.g., Figure 1 or Table 1) in theappropriate order discussed in the text.

- In addition, a brief narrative discussion of EACH table and/or graph should begiven. Discussion should focus on important features of the data and not be simplya repetition of numbers.

- All tables and figures should be located at the end of the written portion of thereport (after references but prior to the appendix). Be sure they:o Present clear and informative figures and tables. Make sure all variables are

defined. For figures, make sure all axes are labeled (with units), that they uselegends to distinguish between multiple sets of data, and avoid the use of colorsunless they print the document in color.

o Put the tables before the figures at the end of the report.o Number each figure and table according to the order they are discussed in the

text.o Provide each figure and table with a title and caption. Both the title and caption

should be in sentence form and be as descriptive (yet concise) as possible.Captions should not be used to discuss or interpret the figure. Rather, it shouldclearly describe what the figure/table presents, and in the case of figures withdata, list key conditions under which the data was collected.

o Be sure that all figures and tables are discussed in the text.o Figures are visually appealing (no border, minimal gridlines, do not overlap

regression lines with lines connecting data points)o Make sure appropriate significant figures are used in all calculations and in

reporting all values.

5. Conclusion (6 points) :

- This section should summarize all important results and interpretations in light ofgoal and objectives for the experiment.

- At least one recommendation should be made for further study or improvement inthe experiment. If no recommendations are provided, a justification for the omission

must be stated.6. References (and Appendices): 2 points

- A list references used in preparing the report must be provided

- Appropriate bibliography formatting must be used. For example, if citations in thetext are by number, this list should correspond to the numbering system. If (Author,

Year) notation is used for citations, the list must be alphabetical.


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- Wikipedia and similar web pages are NOT acceptable sources for scientific literature.

- The appendices should include all additional information relevant to the experimentbut not necessarily integral to the experimental write-up. Specifically, raw data tables,raw data collected from analytical instruments, example calculations, etc. should be

included here.- The appendix should be located after table and figures

7. Xerox Copies of Laboratory Notebook - Each student in the group must attach Xerox copies of his/her laboratory notebook

pages that are relevant to the particular lab after the Appendix.

- These pages will be graded out of 5 points

CEE125 Lab Manual-Winter2015

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