titration user guide.pdf

8/10/2019 Titration User Guide.pdf

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Virtual ChemLab

Acid-Base and Potentiometric Titrations

Brigham Young University


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Table of Contents

Overview..................................................................................................................1

The Titration Laboratory.......................................................................................3Quick Start ..........................................................................................................3

The Simulation.....................................................................................................5Overview........................................................................................................5Simulation Principles and Features ...................................................................6

Laboratory...........................................................................................................8Overview........................................................................................................8Transferring Solutions ...................................................................................11

Analytical Balance .........................................................................................12Overview.................................................................................................12Weighing Solids .......................................................................................13

Pipets...........................................................................................................14Buret and Graphing.......................................................................................14Meters..........................................................................................................15

Indicators .....................................................................................................15Pull-Down TV................................................................................................16

Saving Data..................................................................................................16Stockroom.........................................................................................................16

Overview......................................................................................................16

Selecting Reagents........................................................................................18Preset Experiments .......................................................................................18

Assignments .................................................................................................18Creating Practice Unknowns ..........................................................................19

Lab Book ...........................................................................................................21

The Electronic Lab Book.....................................................................................22Overview...........................................................................................................22Typing/Editing Notes and Inserting Links.............................................................23

Navigation .........................................................................................................23Functions...........................................................................................................24Reporting ..........................................................................................................25

Web Options......................................................................................................27


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Overview

Welcome to Virtual ChemLab: Titrations, a realistic and sophisticated simulation of quantitative

acid-base and potentiometric titration experiments. In this virtual laboratory, students are free tochoose equipment, select reagents, perform titrations, and make the choices and decisions that

they would confront in an actual quantitative experiment and, in turn, experience the resultingconsequences. As in all Virtual ChemLablaboratories, the main focus of the titration laboratory

is to allow students the ability to explore and discover, in a safe and level-appropriate setting, theconcepts and ideas that are important in the study of acid-base and electrochemistry and the

procedures and techniques that form the foundation of titrimetric methods.

The virtual titration laboratory allows students to perform precise, quantitative titrationsinvolving acid-base and electrochemical reactions. The available laboratory equipment consists

of a 50 mL buret, 5, 10, and 25 mL pipets, graduated cylinders, beakers, a stir plate, a set of 8acid-base indicators, a pH meter/voltmeter, a conductivity meter, and an analytical balance for

weighing out solids. Acid-base titrations can be performed on any combination of mono-, di-,and tri-protic acids and mono-, di-, and tri-basic bases. The pH of these titrations can be

monitored using a pH meter, an indicator, and a conductivity meter as a function of volume, andthis data can be saved to an electronic lab book for later analysis. A smaller set of potentiometric

titrations can also be performed. Systematic and random errors in the mass and volumemeasurements have been included in the simulation by introducing buoyancy errors in the mass

weighings, volumetric errors in the glassware, and characteristic systematic and random errors inthe pH/voltmeter and conductivity meter output. These errors can be ignored, which will produce

results and errors typically found in high school or freshman-level laboratory work, or thebuoyancy and volumetric errors can be measured and included in the calculations to produce

results better than 0.1% in accuracy and reproducibility.

The Virtual ChemLabsimulations are available in a network version, a single user or studentversion, or a CD-Only version. In the network version (a typical computer lab installation)

electronic assignments and notebook submissions are handled directly through the local areanetwork or via the web through the web connectivity option. In the single user or student version,

there is assumed to be no internet connection to receive assignments or submit results;consequently, the simulations are limited to using paper assignments contained in the Virtual

ChemLabworkbooks or using assignments written by your instructor. However, a studentversion can be enabled to use the web connectivity option, which enables the exchange of

electronic assignments and notebook results using a regular internet connection. In the CD-Onlyversion, Virtual ChemLabcan be run directly off the CD without having to be installed on a hard

drive. The CD-Only version comes packaged only with textbooks and cannot be enabled to useelectronic assignments. The CD-Only version is designed explicitly to use workbooks that are

included with the text. For increased speed the contents of the Virtual ChemLabCD can becopied to and run from the hard drive.

Please note that this users guide provides information principally for the network or web-enabled

version of Virtual ChemLab. While reading through the users guide, keep in mind that a studentversion and CD-Only version of the software are almost identical to a network version except for

two main differences. (1) In both student and CD-Only versions, the hallway contains anelectronic workbook from which students select experiments that correspond to assignments in


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their accompanying real workbooks. Details on using the electronic workbook are given in theGetting Startedsection of the real workbook. (2) In the initial installed configuration for a

student version, no electronic assignments can be given or received, although preset and practiceunknowns will be available. Note, however, that a student version can be converted to a web-

enabled version by turning on the web connectivity option and creating a local user account.

Details on the web connectivity option can be found in the electronic lab book section of thismanual.


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Figure 1. The hallway leading into the different virtual rooms in Virtual ChemLab. TheOrganic Chemistry door accesses the virtual organic laboratory, the Stockroom door

accesses the Instructor Utilities, and the General Chemistry door accesses fivedifferent general chemistry laboratories.

The Titrations Laboratory

Quick Start

From the hallway (Figure 1), click on the General Chemistry door and enter your password. If

you do not know your password, contact your instructor. If you are receiving assignmentsthrough a regular internet connection either at home or in a computer lab (instead of a direct

client/server connection), you will need to first create a local user account for the currentcomputer you are using by clicking on theAdd New Userbutton. To add a new user, you will

need to provide your user ID, password, and the URL address for your web connection. Thesewill be provided by your instructor. This only needs to be done once for each computer you use.


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If you do not need to receive electronic assignments, click on the Guestbutton on the card readerto gain access to the laboratory.

If your version contains an electronic workbook on a table in the hallway, you can enter the

general chemistry laboratory by clicking on the General Chemistry door or by clicking on the

electronic workbook and selecting an experiment. If you must activate yourself as a user toreceive electronic assignments from your instructor, click on the General Chemistry door andonce inside the laboratory click on any lab book and select the Web Optionsbutton. Details on

how to use the web connectivity feature are found in the Electronic Lab Book section below.

Once in the laboratory (shown in Figure 2), you will find five different laboratory benches thatrepresent five different general chemistry laboratories. Mousing over each of these laboratory

benches pops up the name of the selected laboratory. To access the titrations laboratory, click themiddle table directly in front. On the far right-hand side of the room there is a chalkboard used to

display messages from the instructor or display a summary of assignments. If one or moremessages are available from the instructor, the text Messages will be displayed repeatedly on

the chalkboard. Clicking on the chalkboard will bring up a larger image of the chalkboard wheremessages and assignments can be viewed. Messages can be deleted by clicking on the eraser.

Once inside the titrations laboratory, go to the stockroom counter by clicking on the stockroom

window. Located inside the stockroom are reagent bottles containing acids, bases, inert salts,oxidants, and reductants as well as a clipboard containing a set of predefined titrations. A

titration experiment is started by selecting and dragging to the stockroom counter any two bottles

Figure 2. The general chemistry laboratory. The general chemistry laboratory contains five

different laboratories, each of which is accessed by clicking on the appropriate labbench. The chalkboard to the right in the laboratory is used to access messages from

the instructor and to see a summary of assignments.


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from the acid and base shelves or an oxidant and a reductant from the potentiometric shelf.Assigned unknowns are selected by dragging bottles from the left side of the Unknowns shelf,

and practice unknowns can be defined by clicking on the Unknowns sign. Clicking on thegreenReturn to Labarrow will return you to the laboratory where the selected bottles can be

dragged to the laboratory bench.

Once in the laboratory, a titration experiment is setup by adding a titrant to the buret and theanalyte to a beaker and placing the beaker on the stir plate. For acid-base titrations, pH and

conductivity probes can be placed in the analyte beaker to monitor the reaction as well as anindicator. For potentiometric titrations, a pair of Platinum (Pt)/Standard Calomel (SCE)

electrodes can be used to monitor the titration. Solids can be weighted out accurately using ananalytical balance and solution volumes can be quantitatively measured using either graduated

cylinders or volumetric pipets. Clicking on the buret, pH/voltmeter, and the conductivity meterson the lab bench will open external windows which will allows these values to be measured and

saved to the electronic lab book. This data can also be graphed as the titration proceeds using thegraphing function located in the buret window.

Other important items in the laboratory include the pull-down TV in the upper right-hand corner

whereHelpand assignment instructions are accessed. The electronic lab book is accessed byclicking on the lab book lying on the table. The lab book is used to record procedures,

observations, and conclusions. Volume, pH, conductivity, and voltage data from the titrationscan be saved to the lab book by clicking on the Savebutton located in the buret, pH/voltmeter, or

conductivity windows. This data is saved in the form of links that can be opened and then copiedand pasted into a spreadsheet program for further calculations and graphing. The general

chemistry laboratory is accessed by clicking on the exit sign.

The Simulation

Overview

The primary purpose of the titration simulation is to provide students a realistic environment

where they can explore and better understand acid-base chemistry and electrochemistry usingfundamental titrimetric methods. In Virtual ChemLab: Titrations, experiments are performed in a

framework consistent with the other Virtual ChemLabsimulations; that is, the student is put intoa virtual environment where they are free to choose their reagents and equipment, build a

conceptualexperiment of their own design, and then experience the resulting consequences. Thefocus in the titration simulation is to allow students to perform these titrations on knowns and

unknowns, monitor the titrations using a variety of methods, and interpret their results in termsof the acid-base chemistry and electrochemistry learned in the classroom.

Before the advent and widespread availability of instrumental techniques, quantitative

determinations of unknown concentrations of acids, bases, and metals relied extensively ontitrimetric methods. While modern instrumental methods have supplanted many titrations for

specific analytes, a titration is still the method of choice for many quantitative determinations,particularly for acids and bases. Therefore, it is still important that students understand and

experience the concepts and parameters that govern a titration experiment. These parameterswould include (a) selecting the correct reagent for the analyte, (b) accurately delivering known


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(6)When beakers are placed on the stir plate, a stirring bar is placed in the beaker to enablestirring of the solution during the titration. However, the stirrer motor is not automatically

turned on. If stirring is not on during the titration, then the pH/voltage, conductivity, andindicator color changes will occur with a significant time delay to mimic the slow mixing of

titrant and analyte solutions without stirring. When stirring is on, there will still be a delayed

response but only on the order of a second.

(7)Actual volumetric burets and pipets do not deliver volumes that correspond exactly to the

scale etched on the barrel. These volumetric errors are simulated in the laboratory byassigning appropriate error functions to each piece of precision glassware available in the

laboratory. These glassware errors are unique to each student but remain constant over time.Consequently, for precise work, the glassware errors can be calibrated by delivering

indicated volumes of water and weighing the water on the analytical balance. Note that theerror function for the burets is not a constant; consequently, several calibrations at different

volumes will need to be performed.

(8)

Items that are weighed on a balance in air are buoyed up by the air causing the observedmass, as displayed by the balance, to be different than the true mass. This buoyancy

correction is small but does make a statistically significant contribution when accuraciesapproaching 0.1% are needed. The mass readings displayed on the analytical balance in the

simulation are observed masses and have been reverse corrected from the true mass. Thedetails involved in making buoyancy corrections can be lengthy, but the equation that is

commonly used to make the corrections is as follows:

mtrue = mobs

1 air

weights

1

air

sample

where mtrueis the true mass, mobsis the observed mass, airis the density of air, weightsis the

density of the weights (typically 8.0 gcm-3

) and sampleis the density of the sample. The

density of air can be calculated using a variety of methods, but each requires knowledge of

the temperature and barometric pressure. The temperature and current barometric pressurefor the day is given on the LED display located on the wall. Note that the barometric pressure

will change from day to day in the virtual laboratory but will remain constant for the entireday.

(9)

The accuracy and point-to-point noise are two sources of error that are intrinsic to each pieceof glassware, the analytical balance, and to the pH/voltage and conductivity meters.Appropriately sized errors of each kind are applied in the simulation to each piece of

equipment in order to provide an opportunity for realistic error analysis. In addition, thevirtual auto-reading function of the volumetric buret can be turned off to force a visual

determination of the volume delivered by the buret.


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Laboratory

Overview

The essential features of the laboratory (shown in Figure 3) are described as follows starting

from the upper left hand corner of the lab and proceeding clockwise.

Stockroom. Clicking on the stockroom window brings the user to the stockroom counter.While at the stockroom counter, acid-base or potentiometric reagents can be selected from

the stockroom shelves and placed on the counter. Note that for acid-base titrations, anycombination of acids and bases (including acid-acid and base-base combinations) can be

selected for a titration experiment, and an inert salt can also be selected to study the effect ofinert ions on the pH of the solution. Assigned unknowns can be selected from the unknown

Figure 3. The virtual titration laboratory. Each of the different parts of the main laboratory are

labeled. See below for more details.


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shelf, and practice unknowns can be prepared by clicking on the Unknowns label. Theclipboard hanging in the stockroom can also be clicked to select preset experiments or accept

an assignment.

Pull-Down TV. In the upper right-hand corner of the laboratory is a small handle that, when

clicked, pulls down a TV that can display information in three different modes. In assignmentmode, the TV displays the assignment instructions that may be included with the assignedunknowns currently out in the laboratory. This is intended to allow easy reference to the

assignment instructions while performing the work in the virtual laboratory. When anassignment has not been accepted, the assignment mode is left blank. In tutorial mode, the

TV displays the contents of the buret, pipet, graduated cylinders, and beakers when thecursor is placed over the object. In the help mode, the TV lists the help menu for the

laboratory.

Indicator Chart.The indicator chart shows the color of each available indicator as a function

of pH. Clicking on the chart brings up a new window with the indicator chart enlarged for

easy viewing.

Exit. Clicking the exit sign exits the titration laboratory and returns the user to the general

chemistry laboratory.

LED Display.The LED display is used to display the temperature in the laboratory and the

current barometric pressure. The temperature or pressure is selected by clicking on theappropriate label on the LED display. Note that the laboratory temperature is fixed at 25C

but the barometric pressure will change daily. The temperature and pressure are necessary for

buoyancy corrections.

Graduated Cylinders. There are four graduated cylinders (5, 10, 25, and 50 mL), and they areused to measure volumes of reagents and water with intermediate accuracy andreproducibility.

Water Bottle.The water bottle is used to add approximately 1 mL of water to a beaker or

graduated cylinder.

Distilled Water.Distilled water can be added to beakers and graduated cylinders by dragging

the beaker or graduated cylinder to the sink underneath the distilled water faucet (the faucet

closest to the wall). Distilled water is added as long as the beaker or graduated cylinder iskept in the sink.

Disposal Bucket.The disposal bucket is used to discard beakers and the contents of

graduated cylinders. Clicking on the disposal bucket will clear the entire laboratory.

Indicators.For acid-base experiments, eight indicators are available on the lab bench. Colorsfor each indicator as a function of pH are shown on the indicator chart. An indicator can only

be added to a beaker while it is on the stir plate and only one indicator can be added. An


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indicator is added by either dragging the dropper to the beaker on the stir plate or double-clicking on the selected indicator.

pH Standards.The pH 4 and pH 10 buffer standards are used to calibrate the pH meter before

measuring the pH of a solution. The calibration is accomplished by dragging the pH probe to

one of the buffer solutions and then clicking the appropriate pH button on the pH meterwindow (after it has been turned on). A pH meter calibration requires both the pH 4 and pH10 standards.

Meters.The pH meter and conductivity meter are used to measure and monitor the pH and

conductivity of the solution on the stir plate. For potentiometric experiments, the pH meterturns into a voltmeter. Probes for the two meters are kept in the rack to the left of the meters,

and the probes can be dragged and then placed in the beaker on the stir plate. Note that thepH meter must be calibrated with the pH 4 and pH 10 standard buffer solutions before

obtaining meaningful results. The meters are turned on by clicking on the red/green lights onthe meters, which will, in turn, open external windows for each meter. These windows are

used to display the readings for each meter and to save the data to the lab book.

Stir Plate. The stir plate is used to stir the analyte solution during the titration. Stirring is

turned on by clicking on the front dial. A red light illuminates when stirring is on.

Buret.The buret is used to deliver known volumes during the course of a titration. Solutions

are added to the buret by dragging the solution (either in a beaker or in a reagent bottle) tothe buret and holding while the solution is poured in. The stopcock has four available

delivery rates and is operated by clicking and dragging on the handle or by single-clicking onone end of the stopcock. The stopcock can be closed quickly by double-clicking on the center

of the stopcock. Clicking on the buret will open an external window showing a close-up ofthe meniscus in the buret.

Pipets.Pipets are used to deliver fixed volumes with high accuracy and reproducibility. A

pipet is placed on the ring stand by dragging a pipet from the drawer or by double clicking ona pipet. A pipet is filled by placing a beaker contain the solution underneath the pipet and

then clicking on the pipet bulb to suck up the solution into the pipet. The solution in the pipetis delivered by clicking on the pipet bulb.

Beakers.Needed beakers for any experiment are obtained by clicking and dragging from the

beaker drawer or by double-clicking on a beaker in the drawer. Beakers may be placed in thebalance area, on the stir plate, or on either side of the stir plate. Water can be added to a

beaker by dragging it to the sink and placing it under the distilled water faucet. Solutions areadded to beakers by dragging the bottle, another beaker, or a graduated cylinder to the beaker

and holding while the solution is poured out.

Reagent Bottles.Reagent bottles from the stockroom can be dragged from the counter andplaced on the laboratory bench next to the lab book. Solutions from these bottles can be

poured into beakers or graduated cylinders by dragging the bottle to the desired location andthen holding while the solution pours out.


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Lab Book. The lab book is used to record procedures and observations while performing

experiments in the virtual laboratory. Data from the experiments can also be saved as links inthe lab book where it can then be copied and pasted into an external spreadsheet program for

further analysis.

Balance Area.Clicking on the analytical balance will zoom into the balance area. Whilezoomed in to the balance area, solids can be scooped out of the reagent bottle and then placed

on weighing paper or in a beaker for weighing. Solutions can also be weighed on theanalytical balance. Items to be weighed must be placed in the balance area before zooming

in. The operation of the analytical balance is similar to those found in typical instructionallaboratories. Clicking on theReturn to Labarrow will return the user back to the laboratory

view.

Bell. The bell located on the stockroom counter is used to access Help.

Transferring SolutionsSolutions are generally transferred from a beaker, bottle, or graduated cylinder to anothercontainer by dragging the item with the solution and dropping it onto another beaker, graduated

cylinder, or the buret. Details and exceptions to this general rule are given below, and details onusing the pipets and buret are given in their respective sections. Note that solutions and reagents

cannot be mixed except on the stir plate while doing an actual titration. However, inert salts canbe added to an analyte solution in order to study the effect of changes in the ionic strength.

(1)Solutions from bottles can be poured into beakers and the buret by clicking and dragging the

bottle to a beaker or the buret and holding while the solution pours out. The solution willcontinue to pour as long as the bottle is held in place. For beakers, spilling will occur if too

much solution is added. For the buret, pouring proceeds until the buret is filled to the zeromark.

(2)To transfer solutions to the graduated cylinders, drag the bottle or beaker containing the

solution and drop it on the selected graduated cylinder. This will transfer enough solution tothe fill the graduate cylinder to the indicated volume. Bottles contain an infinite source of

solution, but if a beaker does not contain sufficient solution for the selected graduatedcylinder, then the cylinder will only be partially filled.

(3)Solutions in beakers can be transferred to the buret, graduated cylinders, or another beaker.

This is done by dragging the beaker and dropping it on the selected item. In the case of the

buret and graduated cylinders, enough solution will be transferred to fill to the top of thecontainer. In the case of another beaker, the entire volume of solution will be transferredfrom the first beaker to the second beaker.

(4)Water can be added to beakers and graduated cylinders by dragging the beaker or graduated

cylinder to the sink and placing it underneath the distilled water faucet. Water will continueto be added as long as the beaker or graduated cylinder is in the sink. For beakers, spilling

will occur if too much water is added. For graduated cylinders, filling will automatically stop


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when the graduated cylinder is full. Note that water can be added to an existing solution todilute it.

Analytical Balance

Overview. Clicking on the balance while in the main laboratory zooms into the balance view

(shown in Figure 4) where solid reagents and solutions can be weighed on the analytical balance.

The primary use of the balance in the virtual laboratory is to weigh out solid reagents and toweigh the water delivered by the pipets and the buret in order to calibrate them. The essentialfeatures of the balance view are described below.

Balance. The simulated balance is modeled after a typical analytical balance with a mass

resolution of 0.2 mg. Items (beakers, weighing paper, and solids) can be weighed bydragging and dropping the item on the balance. The balance has a maximum capacity of 200

g. The Tarebutton can be used to tare or zero out the balance.

Figure 4. The zoomed in or balance view. Each of the different parts of the balance area are

labeled. See below for more details.


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These pipets are used by (1) double clicking on the desired pipet or dragging the desired pipet tothe clamp on the left of the buret, (2) placing the solution (in a beaker) underneath the pipet, (3)

clicking on the pipet bulb to draw up the solution, (3) placing an empty beaker underneath thepipet, and (4) clicking on the pipet bulb again to drain the liquid into a separate beaker. Note that

the pipets deliver reproducible volumes within the typical errors associated with volumetric

glassware, but the volume delivered is not exactly the volume indicated on the selected pipet.The pipets can be calibrated by delivering water into a beaker and then weighing the amount ofwater delivered by the pipet.

Buret and Graphing

The buret is used to deliver known volumes during thecourse of a titration. Solutions are added to the buret

by dragging the solution (either in a beaker or in areagent bottle) to the buret and holding while the

solution is poured in. The stopcock has four availabledelivery rates and is operated by clicking and dragging

on the handle or by single-clicking on one end of thestopcock. The stopcock can be closed quickly bydouble-clicking on the center of the stopcock. Clicking

on the buret will open an external window showing aclose-up of the meniscus in the buret. The volume can

be read manually by interpolating the bottom of themeniscus against the volume scale on the buret, or the

volume can be read automatically by saving data to thelab book by clicking on theSavebutton. More detail

on automatically saving the titration data is given inthe Saving Data section below.

Also located on the Buret

Window is the Graphbutton.Clicking on the Graphbutton will

bring up a graphing window thatwill plot the pH (or potential for

potentiometric experiments) as afunction of volume titrated during

the course of the titration. Thegraph will also plot the

conductivity of the solution. The

Savebutton will save the graph tothe lab book, and the Clearbuttonwill clear the graph. When

allowed by the instructor, the PlotWindow is an effective means to monitor the titration as titrant is added, but it is not intended for

any serious data analysis. Data analysis should be performed on the actual data saved to the labbook using the Savebutton located on the Buret Window or on the meter windows.


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Meters

The pH meter and conductivity meter are used to

measure and monitor the pH and conductivity of thesolution on the stir plate during the course of a titration.

For potentiometric experiments, the pH meter turns intoa voltmeter. Probes for the two meters are kept in the

rack to the left of the meters, and the probes can bedragged and then placed in the beaker on the stir plate.

Note that the pH meter must be calibrated with the pH 4and pH 10 standard buffer solutions before obtaining

meaningful results. The meters are turned on by clickingon the red/green lights on the meters, which will, in turn,

open external windows for each meter. These windowsare used to display the readings for each meter and to

save the data to the lab book.

The Savebutton on each meter window is used to save the volume, pH (or potential), andconductivity to the lab book. The Savebuttons on the meter windows perform the same functionas the Savebutton on the Buret Window. Clicking on any of the Savebuttons (except on the Plot

Window) initiates the saving process to the lab book. Details on saving data to the lab book aregiven below.

The pH probe must be calibrated with the pH 4 and pH 10 buffer solutions before the meter will

display the correct pH. This is done by placing the probe in the pH 4 buffer and then pressing thepH 4button and repeating the process for the pH 10 solution except clicking on thepH 10

button. The calibration must be performed each time the pH meter is turned on.

Indicators

For acid-base

experiments, eightindicators are

available on the labbench. Colors foreach indicator as a

function of pH areshown on the

indicator chart.

Clicking on the chartbrings up a newwindow with the

indicator chartenlarged for easy

viewing. Anindicator can only be

added to a beaker


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Reagents.Reagents for titration experiments are selected by clicking on the chosen bottlesfrom the reagent shelves and dragging them to the stockroom counter. Bottles can also be

selected by double-clicking on the bottle. Bottles are returned to the reagent shelves in asimilar manner. For acid-base experiments, any combination of an acid and base, acid and

acid, or base and base can be selected for a titration. For acid-base experiments, an inert saltmay also be selected. For potentiometric experiments, any combination of an oxidant and

reductant can be selected.

Unknown Shelf.The unknown shelf is used to retrieve assigned and practice unknowns andto create practice unknowns. Assigned unknowns will occupy the three left-most positions on

the shelf and practice unknowns will occupy the three right-most positions. Clicking on theUnknowns sign will zoom into the unknown shelf and allow practice unknowns to be

defined.

Figure 5.The titration stockroom. Reagents for titration experiments can be selected bydragging bottles down to the stockroom counter. The clipboard is used to select

preset experiments or view assignment instructions.


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Clipboard. Clicking on the clipboard gives access to 15 preset titration experiments that arealready predefined and ready to run. Be aware that access to these preset experiments can be

turned off by the instructor. The clipboard also gives access to instructions for assignedunknowns given by the instructor.

Activity Coefficients.The activity coefficient box allows the activity coefficients to be turnedoff in the calculations of pH and voltage for the titration experiments. Some instructors mayuse this to explore the importance of activity coefficients in equilibrium calculations.

Bell. As in most stockrooms, the bell is used to access Help for the stockroom.

Return to Lab Arrow. Clicking theReturn to Labarrow returns the user to the laboratory.

Selecting Reagents

Reagents for titration experiments are selected by clicking on the chosen bottles from the reagentshelves and dragging them to the stockroom counter or by double-clicking on the bottle. Bottles

are returned to the reagent shelves in a similar manner. For acid-base experiments, anycombination of an acid and base, acid and acid, or base and base can be selected for a titration.For acid-base experiments, an inert salt may also be selected. For potentiometric experiments,

any combination of an oxidant and reductant can be selected.

Preset Experiments

When allowed by the instructor, the clipboard gives access to a list of 15 titration experiments

that are predefined and ready to run. To select one of these experiments, click on the clipboardand then click on the desired experiment. The appropriate reagents will be automatically selected

and placed on the stockroom counter. Clicking theReturn to Labarrow will then automatically

place the reagents on the table in the laboratory and setup of the experiment. If, after havingselected the preset experiment from the clipboard, the reagents on the stockroom counter aretouched or moved before returning to the laboratory, the preset nature of the experiment will be

turned off and the experiment will have to be setup manually in the laboratory. Several of thepreset experiments come with reagents with unknown concentrations or unknown impurity

levels. The purpose of these preset experiments is to determine the concentration of the unknownsolution or the weight percentage of the unknown solid. When reporting these unknowns to yourinstructor, be sure to include the unknown number.

The following point should be kept in mind: The 15 preset experiments that are included with the

installation cover many of the fundamental titration experiments in acid-base and

electrochemistry. These preset experiments are only a small set of the large number ofexperiments that can be designed and implemented in this simulation.

Assignments

Below the preset experiments on the clipboard, the next available titration assignment that has

been released by the instructor will be listed. The information given in this assignment area is theassignment number, the title of the assignment, the due date, and the points possible. A titration


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assignment consists of one or two bottles (called unknowns) placed on the left side of theunknown shelf that contain a solution of unknown concentration and/or a solid with an unknown

weight percentage. A third bottle may also be placed on the unknown shelf for acid-baseassignments containing an inert salt required for the titration. As part of the assignment, reagents

normally placed on the reagent shelves may be removed, assigned new known concentrations, or

assigned new unknown concentrations. Certain pieces of equipment may also be madeunavailable.

An assignment is accepted by dragging the unknowns off the unknown shelf and placing them onthe stockroom counter. Any changes in the regular reagent bottles on the reagent shelves will be

made at this time. As part of the assignment, instructions may also be included which can be

found on the clipboard by clicking on the View Assignment Instructionslabel located below the

assignment information. The instructions can also be found on the TV while the unknowns are

out in the laboratory.

When an assignment has been accepted, two changes are made to the operation of the laboratory.

(1) Clicking on theAssignmentbutton on the pull-down TV will display the assignmentinstructions. The assignment instructions on the TV are a reference while doing the work in thelaboratory and will be available as long as the assignment is out in the laboratory. (2) After an

assignment has been accepted, a new section is created in the lab book (named with theassignment number) where only the notes and saved data associated with that assignment can be

recorded. Each assignment will have its own section, and these sections can only be modifiedwhile the assignment is out in the laboratory. When the experimental work is finished and the

observations, results, and conclusions have been recorded in the lab book, the assignment issubmitted for grading by clicking on theReportbutton in the lab book. As part of the reporting

process, all unknown concentrations and weight percents will need to be recorded. Aftersubmitting an assignment, further editing in the assignment section is locked out. See the Report

section below for more detail.

The laboratory can be put back into a normal exploratory mode by either reporting theassignment, clearing the laboratory by returning the reagents to the stockroom or by clicking on

the disposal bucket.

Creating Practice Unknowns

Practice unknowns can be generated that will allow students to test titration procedures andcalculations without a score being assigned to the result. The practice unknown view (shown in

Figure 6) is accessed by clicking on the Unknowns label on the unknown shelf. The keyelements of the unknown view include (a) the three unknown bottles, (b) the acid/base

potentiometric switch, and (c) theReturn to Stockroomarrow.

A practice unknown is defined using the following steps:

(1)Use the acid/base potentiometric switch to define the unknowns as either acid-base orpotentiometric.


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(2)Using the drop-down list on one of the bottles, select a reagent that will be used as theunknown. The drop-down list can be accessed by either clicking on the arrow or the Select

Unknown at the top of the label.

(3)Define the minimum and maximum range within which the random concentration or weightpercent will be generated.

(4)

Repeat this process for the other bottles if necessary. Note that each bottle is an independentunknown and that only one practice unknown can be out in the laboratory at any given time.The three bottles allow multiple unknowns to be defined at the same time for convenience.

(5)Click on theReturn to Stockroomarrow to return to the stockroom and generate the

unknowns. The actual concentrations or weight percentages of the unknowns are accessed byreporting the results in the lab book using theReportbutton. New unknown concentrations

are automatically generated after reporting the results.

Figure 6. The practice unknown view in the stockroom as accessed by clicking on theUnknowns sign on the unknown shelf. Practice unknowns are defined byselecting a reagent, defining the minimum and maximum range for the

concentration or weight percent, and returning to the stockroom.


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Lab Book

The laboratory notebook is used to write and save experimental procedures and observations foreach student and to submit the results of assignments. Data from the titration laboratory can also

be saved to the lab book for later reference and more detailed analysis. The notebook isorganized by sections and pages. New pages can be created as needed for each section. The first

section is labeled Practice and is always the section that is available to the student anytime aninstructor assignment is notout in the laboratory. When an assignment is accepted for the first

time, a new section is created in the lab book (named with the assignment number) where onlythe notes associated with that assignment can be recorded. Each assignment will have its own

section, and these sections can only be modified while the assignment is out in the laboratory.Once an assignment has been submitted for grading, no other modifications are allowed. After an

assignment has been submitted, an extra page is added to the end of the section where gradinginformation will be posted.

The lab book is launched by clicking once on the lab book located on the bench top. Detailed

information on how to use the lab book is located in the lab book sections below.


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Electronic Lab Book

Overview

The laboratory notebook is used to write and save experimental procedures and observations foreach student and to submit the results of assignments to the instructor for grading. In addition,

TLC plates and NMR and IR spectra from the organic laboratory; detector output from thequantum laboratory; P, V, T, and ndata from the gases laboratory; volume, pH/voltage, and

conductivity data from titration experiments; and time versus temperature data from thecalorimetry laboratory can be saved in the notebook as well.

The notebook is organized by sections and pages. The section name and current page number forthe section are listed at the top of the page. New pages can be created as needed for each section.The default section is labeled Practice and is always the section that is available to the student

when an assignment is notout in the laboratory. When an assignment is accepted for the firsttime, a new section is created in the lab book (named with the assignment number) where only

the notes associated with that assignment can be recorded. Each assignment will have its ownsection, and these sections can only be modified while the assignment is out in the laboratory.

Once an assignment has been submitted for grading, no other modifications are allowed. After an

Figure 7.The electronic lab book used by the student to record notes.


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assignment has been submitted, an extra page is added to the end of the section where gradinginformation will be posted. Note that electronic assignments can only be accepted and submitted

for a client/server installation or when web connectivity has been enabled.

Typing/Editing Notes and Inserting Links

To start recording notes on the current page, click the page until a cursor appears.

Notes can be typed as normal until the bottom of the page. New pages are not automaticallycreated. Text can be inserted past the end of the page (and accessed using the arrow keys), but

text that extends beyond the end of the page is notaccessible to the instructor during grading.Text is always inserted when typed, and text can be deleted with both the forward and backward

delete keys. Blocks of text can be marked using conventional methods, which in turn, can be cut,copied, and pasted using Ctrl-x, Ctrl-c, and Ctrl-v, respectively, for PC computers or Cmd-x,

Cmd-c, and Cmd-v for Macintosh. Mouse clicks or arrow keys are used to move around on thepage. No other keys are defined for the lab book.

When you generate TLC plates, NMR spectra, and IR spectra in the organic laboratory; detector

output from the quantum laboratory; P, V, T, and ndata from the gases laboratory; volume,pH/voltage, and conductivity data from the titration laboratory; or time versus temperature data

from the calorimetry laboratory, you can save these results to the lab book by pressing the SaveorRecordbutton on the appropriate window. Each TLC, NMR, IR, detector output, gas data,

titration data, or calorimetry data saved in the lab book is saved as a link (in blue or red) with aunique label and is placed on the last line of the current page. Clicking a link displays the saved

item as it was originally shown in the laboratory. NMR spectra and IR spectra saved from thespectra library are labeled as such. Gas, titration, or calorimetry data that were saved during an

experiment are displayed as a table in a display window and can be copied and pasted into aspreadsheet program for further analysis. Links can be deleted from the lab book by deleting the

entire link label, and links can be moved by adding or deleting text around a link. Links cannotbe moved using cut (or copy) and paste commands.

Navigation

Moving around inside the lab book from page to page and section to section is accomplishedusing the four buttons grouped at the top of the left page of the lab book. The functionality for

each of these buttons is described in the sections that follow.

Prev/Next

The Previous andNextbuttons are used to go to the previous or next page in the current section.

If a page in either the downward or the upward direction is not available in the section, thebutton is grayed out and not active.

Search Notes

The Search Notesbutton is used to specify a word or an exact phrase that can be searched for inthe current section or in the entire lab book. Shown on the right is the Search dialog area that is

placed on the left page of the lab book when the Search Notesbutton has been pressed. The text


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box is used to enter the word or words that will be searched for. TheSearchbutton initiates the search for the word or words typed in the

text box. If a match is found, the page with the match will be shownon the right page of the lab book with the match highlighted. Pressing

the Searchbutton again will search for the next occurrence. After a

match has been found, pressing the OKbutton will close the Searchdialog and switch the lab book to the new page. Pressing the Cancelbutton closes the Search dialog and keeps the lab book on the old

page. The Current SectionandAll Sectionsradio buttons specifywhether the search is to be made on the current section or over all

sections in the lab book, respectively.

Go To Page

The Go To Pagebutton is used to jump to any page in any of the sections in the lab book. Shown

in the accompanying figure is thedialog box that is displayed when the

Go To Pagebutton is pressed. Thefirst box lists the available sections inthe lab book by name. Clicking one of

these will then list the available pagesfor the highlighted section in the

second box. Clicking one of the pageswill switch the lab book to the

indicated page and section. Pressingthe Cancelbutton keeps the lab book

on the old page.

Functions

Grouped below the navigation buttons are a set of buttons which perform various functions in the

lab book. These functions are described in the sections that follow.

New Page

This button creates a new page at the end of the current section. The button is only active whenyou are on the last page of the section. Pages cannot be inserted elsewhere in the section.

Delete Page

This button deletes the current page in the currently selected section. A warning is given beforethe deletion occurs.

Rename Section

This buttons brings up a dialog box that allows the name of

the current section to be changed. By default, the first sectionin the lab book is given the name Practice, and other sections


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that are added to the lab book for each assignment are given the nameAssignment nwhere nrepresents the assignment number. The practice section is for keeping notes when exploring and

learning in the laboratory, and the assignment sections are used for keeping notes duringassignments and are eventually graded by the instructor. TheRename Sectionfunction allows

these default names to be changed.

Print

This button brings up a dialog box that allows either the current page or the current section to be

printed to a user-selected printer. Links cannot be printed.

Report

This button allows the current assignment to be submitted to the instructor for grading and isonly active when an assignment is out in the laboratory. Upon submitting an assignment for

grading, further modifications to the assignment section are locked out and an extra page isadded to the end of the section containing grading information specific to the assignment. The

exception to this is when an Inorganic or Titration practice unknown is submitted which onlyreveals the actual contents or concentration of the unknown and no grading is performed. If web

connectivity has been enabled (see the Web Optionsbutton below) then, after submitting theassignment, the student will be prompted to update these results to the server immediately. If

Automatic Updates has been selected, this update is performed automatically after submitting theassignment.

Inorganic Assignments Pressing theReportbutton for an inorganic assignment brings up a

report window where the possible cations in the unknown are listed. To report the contents ofthe unknown, click the appropriate tiles corresponding to the cations present in the unknown.

For assigned unknowns, these selections can be saved by pressing the Savebutton allowing

the user to return to the lab for further work on the unknown. The Savebutton is disabled forpractice unknowns. When the assigned or practice unknown is ready for grading, click theSubmitbutton, which in turn, brings up a warning box stating that no further modifications

can be made to the assignment. Clicking OKsubmits the unknown and then marks eachcation in the unknown as correct (green) or incorrect (red). For assigned unknowns, the score

is also posted, and the entire grading report is written on the last page of the assignmentsection.

Quantum Assignments Pressing theReportbutton for a quantum assignment brings up atext box warning the student that submitting an assignment prevents further modification of

the assignment section. Selecting OKbrings up a second warning box which, when OKis

selected again, submits the assignment, closes the lab book, and clears the laboratory.Grading information is placed on the last page of the section.

Gases Assignments Pressing theReportbutton for a gases assignment brings up a text boxwarning the student that submitting an assignment prevents further modification of the

assignment section. Selecting OKbrings up a second warning box which, when OKisselected again, submits the assignment, closes the lab book, and clears the laboratory.

Grading information is placed on the last page of the section.


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Titration Assignments Pressing theReportbutton for a titration assignment brings up adialog box which asks the student to enter the concentration or weight percent of theunknown or unknowns that were assigned. A warning is also given about locking out the

section after the assignment has been submitted. Selecting OKbrings up a second warningbox which, when OKis selected again, submits the entered values, submits the section notes,

pops up a text box with the correct values, closes the lab book, and clears the laboratory. Thecorrect concentrations and/or weight percents, the entered concentrations and/or weight

percents, and grading information is placed on the last page of the section.

Calorimetry Assignments Pressing theReportbutton for a calorimetry assignment brings upa dialog box, which asks the student to enter the heat of reaction, solution, or combustion or

the heat capacity of the unknown or unknowns that were assigned. Note that it is important toplay close attention to the units that are requested. A warning is also given about locking out

the section after the assignment has been submitted. Selecting OKbrings up a secondwarning box which, when OKis selected again, submits the entered values, submits the

section notes, pops up a text box with the correct values, closes the lab book, and clears thelaboratory. The correct values, the entered values, and grading information is placed on the

last page of the section.

Figure 8. The report window for reporting inorganic assignments. Use theReturn to Notesbutton to cancel the submission process.


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Web Options

Overview.This button is the main access point for the web connectivity option of the program.

The Virtual ChemLabsimulations can be installed in a client/server mode or in astandalone/student mode. In the client/server mode (a typical computer lab installation)

electronic assignments and notebook submissions are handled directly through the local areanetwork. In the student mode, there is no direct connection to receive assignments or submit

results and, therefore, the simulations are limited to working locally without electronicassignments. Consequently, paper assignments or exploratory work are the typical applications

for a student version. With the Web Optionsfunction, a web-based connection can be establishedand configured to enable the exchange of electronic assignments and notebook results without a

direct network connection. Some computer lab installations may find this to be the favored modeof operation as well.

The information that is needed to setup web connectivity is (1) a user ID, (2) a password (often

your student ID), and (3) the URL for the web connection. This information must be provided bythe instructor or system administrator. Once this information has been obtained, you will then

only need an active network connection either through a dialup service, cable modem, DSLservice, regular campus access, or any other valid means. Note that a network connection is onlynecessary when updating notebook results and receiving assignments. All other activity in the

simulations can be performed off-line.

Figure 9. The Web Optionspage used for establishing and configuring

web connectivity. Web connectivity allows for the exchange ofelectronic assignments and notebook results via the internet.


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Shown in Figure 9 is the Web Optionspage after it has been enabled for web connectivity. Thereare four functions performed on this page: (1) Enable web connectivity, (2) Create local user

accounts by specifying the user ID, password, and URL, (3) Retrieve from and update to theweb, and (4) Delete local user accounts. Descriptions of each button and text field is given

below.

Enable Web Connection.Clicking this button turns on the web connectivity functionality andallows local user accounts to be created (see Create Accountbelow). As shown in Figure 12, the

web connectivity has already been enabled. Once at least one user account has been successfullycreated, the web connectivity functionality cannot be disabled until all local accounts have been

deleted (seeDeletebelow).

Create Account.Because class assignments, notebooks, and grades are unique to each studentregistered in the ChemLab database, a unique account must be created for each user on each

computer. Clicking the Create Accountbutton allows a new local user account to be created byentering a valid user ID, password, and URL. There are two important considerations to keep in

mind when creating accounts. First, before any accounts are created, access to the laboratories isimmediate and bypasses the card reader requesting password (student ID) information. The first

account can only be created in the lab book using the Create Accountbutton, and subsequententry into the laboratories will require providing the correct password at the card reader. After

the first account has been created, new local accounts can be created using theAdd New Userbutton on the card reader. Second, for computer lab installations, each user cannot be guaranteed

of using the same computer each time they access the program. Consequently, their local accountwill not always be found on the computer available to them. TheAdd New Userbutton on the

card reader will be useful to create local accounts as needed when using different computers.

User ID. To create a local account, a valid user ID must be entered in this field. This user ID willbe provided by the instructor and is case sensitive. The user ID is typically the first 6 letters of

the last name followed by the first and middle initials (for example, SmithJD). The entered userID is saved by clicking on the Savebutton or by pressing Enter or Tab. Using Enter or Tab will

automatically advance the cursor to the password field.

Password.A password is also necessary to create a local account and will be provided by theinstructor. The password is also case sensitive. The password entered here will also be the same

password (usually a student ID) that will be used to enter into the laboratory at the card reader(see Create Account). The entered password is saved by clicking on the Savebutton or by

pressing Enter or Tab. Using Enter or Tab will automatically advance the cursor to the URLfield.

URL.The actual web connectivity functionality works by passing assignment and notebook

information between the student and a central database via a servlet engine running on a webserver at a certain URL address. The exact (case sensitive) URL address that will be used to pass

assignment and notebook information must be specified in this field. The URL address will beprovided by the instructor. Note that the most recent valid URL address will become the default

address for any subsequent local user accounts; however, each local user may have a uniqueURL address. Also note that most URL addresses will be longer than the length of the text box


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provided. Text at the end of the URL can be accessed by using the arrow keys. Pressing Enter orthe Savebutton will initiate the account validation process. An internet connection is necessary

in order to validate the user ID and password information.

Enable Automatic Updates.Checking this box will enable automatic updates (both receiving

from and sending to the server) when entering the laboratory at the card reader, exiting alaboratory, and when submitting assignments. This option is recommended when an internetconnection is continuously available. This option is also permanently selected for computer lab

installations using web connectivity.

Send Updates. Clicking on this button will immediately send the notebook and assignmentinformation up to the server where they will be collected by the instructor. This button is the only

location where updates can be sent to the server on demand; however, warnings are given toupdate to the server when exiting laboratories and submitting assignments. If the Send Updates

button has been clicked even though there have been no changes made to the notebook, awarning is given indicating that an update is not needed. If an update is still selected (by

clicking Yesat the prompt), then an update will be forced to the server replacing any oldinformation.

Receive Updates. Clicking on this button will immediately collect any new assignments,

messages, or grading information posted by the instructor. This button is the only location whereupdates can be received from the server on demand; however, an update can be performed

automatically at the card reader ifEnable Automatic Updateshas been selected. If theReceiveUpdatesbutton has been clicked even though there have been no changes made to the

information on the server, a warning is given indicating that an update is not needed. If an updateis still selected (by clicking Yesat the prompt), then an update will be forced from the server

replacing any old information stored locally.

Save. Clicking the Savebutton saves any text entered in the User ID, Password, or URL fields.Clicking Savein the URL box also initiates the account validation process with the server.

Cancel.Clicking the Cancelbutton cancels the account creation process and resets the Web

Optionspage back to its initial state. Clicking Cancel does not cancel any web operations thatmay be in progress.

Delete.Clicking on this button deletes the current local account from the local hard drive and

returns the user back to the hallway. Deleting all the local user accounts returns the softwareback to the original installed state and disables the web connectivity option. A warning is given

before the actual account deletion occurs.

titration user guide.pdf

Documents