The purpose of this laboratory course is to familiarize you with experimental approaches to the theoretical concepts presented in Physical Chemistry lectures. In performing the experiments, you will be introduced to basic apparatus and will learn fundamental experimental techniques used in physical chemistry.

Just as important to the performance of an experiment is the analysis and reporting of the results. The experiment might just as well not be undertaken if the results are not properly interpreted and reported. The report should demonstrate the ability to organize thoughts and understand the concepts involved. It is not unusual to spend more time on the analysis of the data and the writing of the report than on the actual performance of the experiment. To best utilize the time allotted for an experiment, it is necessary for you to come to the lab prepared (read the experiment in advance) and to spend the laboratory period in full concentration on your work. Computers are provided in the laboratory so that you can graph the data. It is expected that all data obtained in the first period will be graphed and presented to the instructor at the beginning of the second period along with a brief progress report (1 page).

All work in the laboratory will be done in pairs except under the special permission or direction of the instructor. During the first laboratory period, the instructor will assign your partner. Each pair will be given a group number to facilitate assignment of experiments. Each partner of a given pair is expected to carry their own weight as far as the experimental work is concerned. Although the experiments are performed in pairs, the lab reports are to be done individually Any two reports that are identical in the theory and/or discussion parts are not acceptable and will be returned to the individuals for rewriting. Each pair will work on only one experiment at a time. The only exception being that preparation of solutions for a following experiment can be carried out while working on a current experiment.

Attendance in laboratory courses is a requirement! Being absent is unfair to your partner and to yourself. Since it is almost impossible to make up missed labs as all laboratory sections are filled to capacity, it is incumbent upon the student to be present during his/her regular laboratory and to contact his/her instructor at the earliest possible date if an absence is to or does occur. Excessive absences will result in incompletes or failures.

The semester is devoted to experiments illustrating theory which has most likely been covered in Chem 231 and 235 lectures. The five experiments that are to be performed (two weeks/experiment) by each group will be assigned by the instructor. Under no circumstances is a group to do an experiment other than that which is assigned to them. Formal written reports shall be submitted for each of these experiments. In addition, an oral report is to be presented during the 13th and 14th weeks of the semester.

The limited number of set-ups requires that the experiments be run on a rotating schedule. A schedule will be posted in order to facilitate prelaboratory planning and enable you to make the most efficient use of your time. A group assigned a piece of equipment for a given period has access to that equipment for that period only. It will be necessary for you to plan ahead in order to make efficient use of your time and be able to finish with the assigned equipment in the time allotted to you.(Translation:read the experiment before coming to lab!)

Week(s)

1 Introductory remarks. Check-in of Lab Drawer. Assignment of Lab Groups and Experiments: Read pages 1-11. Safety Lecture. A Special section of Math 225 will be devoted to the detailed discussion of Data Analysis.

2-3 Perform first experimental assignment.

4-5 Lab report due for first experiment at beginning of lab period of fourth week; perform second-experimental assignment. Week 5 instructor will return and discuss the graded reports with each student individually.

6-7 Third experimental assignment(lab report for second experiment due sixth week).

8-9 Fourth experimental assignment (lab report for third experiment due eighth week).

10-11 Fifth experimental assignment (lab report for fourth experiment due tenth week).

12 Make-up lab/general clean up (lab report for fifth experiment due twelfth week). CHECK-OUT.

13-14 Oral Reports.

Effective use of laboratory time is essential. To do a good job on a given experiment should take all the time alloted for that experiment. Sloppy jobs in record times will be rewarded with poor grades. The efficient students who finish an experiment early will find a productive means of filling out the time. (Translation: additional runs recommended.)

All experimental work must cease and cleaning up must begin ten minutes before the end of a laboratory period. Equipment that is to be returned to the stockroom should be submitted at this time. The physical chemistry stockroom is serviced by Mr. Yogesh Gandhi and the Physical Chemistry Laboratory instructors are Dr. Bozzelli and Dr. Grow.

Beginning with Chem 235A, students are to purchase a National Blank Student Laboratory Research Notebook from Saunders. This book may subsequently be used in other courses, therefore reserve the first few pages for a Table of Contents.

Data obtained in the laboratory must be recorded by each member of the group in his/her own carbon tear-sheet notebook! The need for neat and careful tabulation of data cannot be stressed too greatly. To accomplish this a data sheet is prepared in duplicate before the experiment is started. The carbon copy is submitted at the end of each day after it has been initialled by the instructor. All data sheets must be initialled. Remember, each student records his/her own data and submits his/her own carbon copy.

Data sheets are to have as a heading the student's name, partner's name, the date, and experiment number. They should contain all significant records of observations. For example, in recording the weight of a material, it is necessary to plan for the weight of the weighing bottle before and after removal of the sample. Model numbers of instruments that are of significance should be recorded. No ERASURES are to be made. Incorrect entries should be crossed out. Use a ball point pen, pencil is unacceptable!

In many experiments you will being using sensors. It is very possible that the discs with your experimental information will be corrupted in some manor. It is a good idea to record as much as possible in your lab. notebook so that the information is not lost. You are responsible for the data and back up discs are recommended.

Under the heading of "Apparatus" in the directions for each experiment in this outline, the following abbreviations are used:(S) refers to material or apparatus obtainable from the stockroom. This equipment, unless otherwise specified, is to be returned to the stockroom at the end of the laboratory period for which it was checked out.

(D) refers to apparatus already in the student's desk.

(L) refers to apparatus, chemicals, or stock solutions already in the laboratory. The chemicals are located in two cabinets; one cabinet is for solids and one is for liquids. Stock solutions are on the side shelf along the south wall of the lab.

(H) refers to chemicals located in the hood.

(D,S) refers to the fact that some or all of this equipment is in your desk; check-out remainder from stockroom but return it at completion of the experiment or at end of lab period, whichever is applicable.

(P) refers to solutions which are to be prepared by the student. Most of the time these solutions can be prepared by appropriate dilution of a stock solution. Sometimes the solution has to be prepared fresh from chemicals available in the cabinet.

(M)refers to this manual.

There are Four section to this manual. In this section, the general procedures to be used in the lab are discussed.

In the second section each experiment is discussed in detail and some theory is presented. However, do not consider the theory presented here to be complete. Your lecture course materials should be consulted for each and every experiment.

The third section contains information on sensors. If under the heading of "Apparatus", a sensor is indicated, this part of the manual must be consulted. The general information on how to conect the sensors is contained in the beginning of the section under "Serial Box",there is a short description on how most of the sensors work, and a "QuickStart" procedure, which describes how to use the sensor.

Finally, the manual for large peices of equipment used in the experiments are provided. If a manual is provided for an experiment, It will be stated under the heading of "Apparatus.

The policy of the Department of Chemical Engineering, Chemistry and Environmental Science is NOT to use any chemical in instructional laboratories which has been classified by OSHA as a Category I carcinogen. This does not mean that the chemicals you will be using are not hazardous. All chemicals are potentially hazardous. Those found in the instructional laboratory are not harmful if directions for use are followed, but any one of them may cause harm or serious injury if misused. Therefore it is essential to understand the possible hazards involved.

A good common sense question to ask before performing an experiment is "What would happen if ...?" To answer this you need to have an understanding of the hazards associated with the chemicals and equipment involved. Knowledge of stability, toxicity, reactivity and flammability of the chemicals used will dictate the precautions to be taken. This information is generally supplied on the labels of reagent bottles. Additionally, such information is available for 380 specific chemicals for which there are Federal regulations in the Health Safety Manual on Chemical Hazards distributed by the Radiation Biohazards Committee of the Institute. A copy of this is available at the stockroom window for your reference. There should also be a copy on the Instructor's desk in the lab.

For a given experiment, warnings are given in this Laboratory Manual if it is deemed necessary to take special precautions when working with a chemical. As a general rule of thumb, avoid direct contact with any chemical. A good common sense safety practice is to always wash face, hands, and arms upon leaving the laboratory.

Dispensing of Chemicals. For the experiments which use organic liquids, premeasured quantities are available at the stockroom. The amounts supplied are more than adequate to perform the experiments. The need of additional quantities, indicative of being wasteful, is considered Poor Laboratory Technique and as PLT, grade penalties of 10% may be applied. This policy requires that you, the student, plan ahead and not be extravagant with regard to the use of chemicals. The procedure is simple! To obtain the desired chemical for the assigned experiment, you must sign the CHEMICALS REGISTER at the stockroom window. Information to be supplied: NAME/DATE/SECTION #/Experiment #/CHEMICAL.

Waste Disposal. The Environmental Protection Agency RCRA Regulations require that accurate records be kept for hazardous chemical wastes. Accordingly, each time a chemical is added to a waste container in the Physical Chemistry lab, the following information must be entered into the registry of that container: DATE/STUDENT'S NAME/NAME OF CHEMICAL/VOLUME (approximate).

To facilitate compliance with these regulations, it is recommended that you collect the waste organic solvents in a covered container (e.g., bottle with screw cap) while actually performing the experiment(s). These collected wastes are then to be deposited into the appropriate waste container at the conclusion of the experiment(s). In this way, only one entry into the REGISTRY is required per experiment or group of experiments.

NOTE: ONLY ORGANIC SOLVENTS (No aqueous solutions) are to be placed into the RED waste containers. Pour non toxic aqueous solutions down the drain and flush with copious amounts of H2O.

Lab Clean-up. Students are responsible for keeping the laboratory clean! The laboratory will be bright and shiny the first day of the semester and will stay that way if each of you clean up after him/herself at the conclusion of each period. You are responsible for the bench areas and balances which are assigned to you. Leaving your working areas cluttered and/or dirty is considered PLT and, as such, will result in appropriate grade penalties. Each member of a partnership is held equally responsible and will share grade penalties in a like manner. The GA's and Instructors will check the Balance Room and all working areas at the conclusion of each lab period.

Balance Assignments. Balances are assigned according to group number (Group #1 uses Balance #1, etc.). You are to use only that balance to which you are assigned. If your balance does not work properly, consult the instructor immediately! It will be repaired and/or other arrangements for weighing will be made.

Effective communication, both written and oral, is essential for an engineer or scientist to be successful. Written reports are stressed in this course, but an oral report is also required.

A formal written report in a manila folder or similar cover is required for each of the five experiments performed during the semester. They are due at the beginning of the first laboratory after the experiment is completed. Absence from class, except for due cause, does not constitute a waiver of this requirement. Late reports are penalized (5% each day late). The absolute deadline for acceptance of any report is two weeks past its due date, the report will not be accepted after that time. All five reports are to follow the format on the following page.

During the 13th and 14th week of the semester, an oral report is to be given on one of the experiments performed during the semester. The assignment for this presentation will be made by the instructor after consultation with each pair of students in the class. To facilitate the presentations an overhead projector is to be used. Instructions for preparation of the transparancies will be distributed in the latter part of the semester. More information about these oral reports will be forthcoming.

I.TITLE PAGE

Experiment Number

Experiment Name

Your Name

Partner's Name

Date(s) Experiment was Performed

Date Due

Abstract

II. INTRODUCTION

1. Object of the Experiment (one sentence)

2. Brief Discussion of the Theory (citing pertinent equations and defining all terms used in the equations)

III. EXPERIMENT

A Summary of the method(s) used to obtain the data should be included. It is important to mention any variation from the procedure described in the handout, or operating manuals.

IV RESULTS & CALCULATIONS

1. Table of Data for Individual Runs, and Calculated Results for

Individual Runs

2. Graphs

3. Sample Calculations of Results (for each type of calculation)

V. ERROR ANALYSIS

1. Systematic and Random Errors; Sources and Estimated Magnitudes

2. Propagation of Error to Assign Uncertainty to Calculated

Results (Sample Calculation)

VI. DISCUSSION & CONCLUSIONS

1. Results ± Limits of Error and Comparison with Literature Values

2. Discussion of Reasons for Disagreement

3. Recommendations for Improving Experiment

4. Answer Questions at End of Experiment

VII. RFERENCES & NOTES

References are to be presented in a formal way. e. g.

References

Be forewarned that it takes time to write a decent laboratory report, and it is advisable not to put this important task off until the last minute. Two methods for propagating errors are preferred, the MOST PROBABLE and the MAXIMUM PROPAGATED ERROR. The following simple example illustrates the difference between these two methods.

The molecular weight of an ideal gas may be calculated from the ideal gas law PV = (W/M)RT where

P = pressure (atm)

V = volume (liters)

W = weight (grams)

T = temperature (oK)

R = 0.08206 l.atm/moleoK

In an experiment with CH4 a student obtains the following values and estimates the indicated errors:

P = 735 ± 1 mm

V = 210 ± 2 ml

W = 137 ± 2 mg

T = 25 ± 1 oC

Calculate M, the maximum propagated error in M, and the most probable propagated error in M from the uncertainties, assuming CH4 follows the ideal gas law exactly.

MAXIMUM PROPAGATED ERROR: M = f(W,R,T,P,V) as M = (WRT/PV)

or 0.5 g/mole

So, M = 16.5 ± 0.5 g/mole

At this point, one should answer the Question "What is the largest error source?"

dW/W = 0.0146; dR/R = 0; dT/T = 0.0035; dP/P = 0.00136; dV/V = 0.00955

LARGEST ERROR IS IN WEIGHING.

MOST PROBABLE PROPAGATED ERROR. M = WRT /PV

or 0.3 g/mole

THUS M = 16.5 ± .3 g/mole

QUESTION:

Which is the correct method to use when propagating errors?

ANSWER:

Generally, when the quantity to be determined is a function of three or more experimental variables, the maximum propagated error over estimates the uncertainty (Why?) and the most probable propagated error is a more realistic measure of the uncertainty.

In our example, the molecular weight M is a function of 4 experimental variables (W, T, P, V) and hence the maximum propagated error of dM = ± .5 is an over estimate. Hence, the molecular weight should be reported as M = 16.5 ± .3 grams/mole.

Many times the quantity of interest is determined from the slope of a linear plot of the data. In this case, the uncertainty in the quantity is best estimated assuming the line is defined by two points, and by propagating using the Most Probable Propagated method. The following example illustrates this method.

Example: ln(P) =

Write the equation in terms of 2 points

We have: P1,P2, T1, T2 and the errors dP1, dP2, dT1, dT2

Use the most probable propagated error as a measure of error in D H, as follows:

D H = f(P1, P2, T1, T2)

Evaluate the partials using the values of P1, P2, T1, and T2, and then substitute these values into the equation for dD H. Note that this is only an estimate in error; a more rigorous treatment can be made when a least squares analysis is made.

Neatness in working habits and surroundings is considered essential to good laboratory work. Students are responsible for the cleanliness of bench tops, balance rooms, and working spaces in any part of the laboratory. Liquids and solids should be cleaned up and spilled mercury recovered PDQ! Clean up pieces of broken apparatus. A brush and dust pan are available (S).

Laboratory work can not be done outside of the regularly scheduled period! Students are not to enter the laboratory until the instructor is present! Report faulty or broken apparatus to the instructor immediately! Temperatures of the thermostats should be checked and deviations from the set value reported.

Failure to comply with the above stated rules and safety precautions is considered POOR LABORATORY TECHNIQUE (PLT) to say the least, and will result in a corresponding reduction in your laboratory grade.

I, as a student in Chem 235A lab, have read, understand and will abide by the above stated rules and regulations.

Signed _______________________________