· Web viewThe objective of this experiment is to determine the order of a reaction. For this we will look at the redox reaction between Fe3+ ions and I- ions. ... The I 2 produced

Order of a reactionIntroduction:

The objective of this experiment is to determine the order of a reaction. For this we will look at the redox reaction between Fe3+ ions and I- ions. The equation for the reaction is represented as follows.

2Fe(NO3)3 + 2KI 2Fe(NO3)2 + 2KNO3 + I2

2Fe3+(aq) + 2I-

(aq) 2Fe2+(aq) + I2

The I2 produced in this reaction imparts a color to this solution; hence we can study the rate of formation of Iodine using a colorimeter and measure the change in absorbance using the Beer Lamberts law.

Beer Lamberts Law

A=log10I 0I

A = lc

‘A’ represents absorbance, which we will be measuring. ‘’ is molar absorptivity. ‘I0’ is the intensity of light at zero absorbance or the blank. ‘I’ represents the absorbance of the coloured solution or intensity of light passing through the sample solution. If I < I0 some light has been absorbed by the solution. ‘l’ represents the length of the light path through the solution and ‘c’ represents the concentration of the solution.

A=log10I 0I

The ExperimentObjective of the experiment:

The objective of this experiment is to determine the order of each of the reactants and the overall order of the reaction.

2Fe3+(aq) + 2I-

(aq) 2Fe2+(aq) + I2

Rate = k[Fe3+]x [I-]y

In order to determine the value of ‘x’ and ‘y’, we will use the Colorimeter and a Labquest

Principle:

The initial rate method is being adopted to determine the order of the reaction. For that we will study the effect of changing concentration on the rates of the reactants.

The initial rates are determined using the colorimeter, which determines the changing rate instantaneously; using this data the order of the reactants will be determined, and hence the order of the reaction.

Reagents Required:

0.02 M Fe3+ from Fe(NO3)3.9H2O. The iron(III)nitrate is prepared in 0.1 M HNO3 solution

0.02 M I-(aq) solution. The aqueous solution is prepared by dissolving solid KI in distilled water.

Distilled water or deionized water 0.1 M HNO3 for preparing the iron (III) solution 1 liter of each of the reagents should be sufficient for 10 groups of students, for rinsing and

about 5 trials.

Equipment’s and Glassware

Labquest Colorimeter Cuvettes Wash bottle with distilled water Graduated pipettes Beral pipettes 100 mL Volumetric flask Three way bulbs for measuring and transferring reagents 50 mL beakers Lint free tissue or least Kleenex to wipe the cuvettes Stop Watch

©Stan Vincent Eureka 2015 – Order of a reaction SCH4U

Procedure

Turn on the lab-quest and connect the colorimeter – Leave the colorimeter turned on at least 5 minutes before you start data collection.

Lab quest set up.o Go to > Sensors > Data Collection > o Time bases > Rates = 1 sample/s > Interval = 1 s / sample > Length = 200 secondso OK

Colorimetero Select the wavelength 470 nm using < or >o Prepare a blank: In this case the blank is the Fe3+ ion solution. Fill the cuvette 3/4th with

the blank. Close the cuvette.o Place it in the colorimeter; the clear side of the cuvette should face the white triangle.

Close the colorimeter. o Press calibrate. It is a one button calibration.o When the red light stops blinking and the absorbance on the Lab quest is 000 the

instrument is calibrated.


Reagents required:

Fe3+ 0.02 M in 100 mL = Ci

0.02 M KI in 100 mL = Ci

Distilled water Mix the volumes needed according to the table provided (at least 3 trials; 1,2 &3)

NOTE: Do not mix the two solutions until you are ready to record the readings.

DILUTION

Table 1 DILUTION

Trial FeCl3 (mL) KI (mL) H2O (mL)

1 10.0 10.0 0.02 10.0 5.0 5.0

3 5.0 10.0 5.0

DATA TABLEThis table now gives you values which can be used to solve for the order of the reaction using initial rate method.

TABLE 2 RATE OF REACTION

Trial [Fe3+] [I-] Initial rate (s–1)

Value of ‘m’ from Labquest

1 0.01M 0.01M

2 0.01M 0.005M

3 0.005M 0.01M


C f=C iV iV fC f=

C iV iV f

Data collection:Note: There should be consistency for the time taken between mixing the two solutions and data collection for all the three trials, use a stop watch.

Trial 1

1. Pipette 10 mL of Fe3+ (Iron(III) solution) into a 50 mL clean dry beaker followed by 10 mL of I - (Potassium Iodide) solution into the same beaker. It would be a good idea to start a stop watch to maintain consistency in time between mixing the reagents and start of data collection. After mixing the solutions properly using a glass rod, transfer the mixture to a clean cuvette using an eye dropper or a beral pipette, close the cuvette.

2. Place the solution in the colorimeter that has been calibrated, close the colorimeter3. Press the play button to start the data collection4. Wait for 200 seconds for the collection to be complete. Data collection stops after 200 seconds.5. Dispose the solutions appropriately as instructed.

Trial 2 and Trial 3

1. Prepare the solutions for trial 2 and 3 separately using the table 1 data.2. Press the file cabinet icon on the Labquest 3. Repeat steps 2 to 5 under Trial 14. Repeat all these steps for trial 3.


Data Analysis on the Labquest:

Open Run 1 Select a segment of the graph for 30 seconds (50 seconds to 80 seconds as shown in the video) Select analyze Choose curve fit Absorbance Linear Now write down the value of ‘m’ or slope of line in the data table Next select OK Choose Run 2 and repeat the process until you find the slopes for all the three runs. Record the

data. Once you have the values you can calculate the order of the reaction

Note: When the slope is determined after collection of data for all three runs, you get the slope for the same time segment for all three runs. This will work positively if the time between start of experiment and data collection (pressing the play button for data collection) are the same.


Calculation:The order can be determined using initial rate method calculation

Trial1Trial 2 Should give you the order of iodide ions

Rate 1Rate 2

= [0.01]x

[0.005]x

[ ][ ]

= [0.01]x

[0.005]x

Solve for ‘x’

‘x’ is the order of Iodide ions

Similarly solve for ‘y’

Trial1Trial3 Should give you the order of Fe3+ ions

Rate1Rate 3

= [0.01]y

[0.005]y

[ ][ ]

= [0.01]y

[0.005]y

Solve for ‘y’

‘y’ is the order of Fe3+ ions

Rate = k[Fe3+]y [I-]x

Repeat calculation for the different trials performed to complete the lab.


Pre lab Questions: Order of a Reaction(Student has to submit before the experiment starts)

1. Define order of a reaction

2. Write the units for zero, first and second order reactions.

3. If the concentration of a reactant is doubled, and the rate of the reaction increases 8 fold, what is the order of the reactant?

4. Calculate the mass of Fe(NO3)3.9H2O required to prepare 250 mL of 0.02 Molar solution.

5. Why do we add 0,1 M HNO3 solution while preparing the Iron(III)nitrate solution?


Discussion questions:To be submitted after performing the lab along with a lab report (Discussion questions may be part of the lab report if writing a lab report)

1. What is the order for each of the reactant in the lab you just performed, explain your rationale?2. Writ the rate law for the experiment that you performed.3. Is the rate law and law of mass action the same? Does it suggest a possibility for the mechanism for

this reaction, explain.4. List all possible instrumentation errors.5. List all possible human errors that you may have encountered?6. List all the errors that could have been avoided in this lab.7. What are some possible modifications that you would suggest for this experiment?8. Write a conclusion for you experiment 9. Include data sheet along with calculation.


Data sheet – Submit to teacher after labTo be submitted to the teacher on the day of the lab immediately after data collection.

This table now gives you values which can be used to solve for the order of the reaction using initial rate method.

TABLE 2 RATE OF REACTION

Trial [Fe3+] [I-] Initial rate (s–1)

Value of ‘m’ from Labquest

1

2

3


C f=C iV iV fC f=

C iV iV f

Quick Setup And Short Lab Guide1. Wear goggles at all times2. If you come in contact with any solution please wash it off using cold tap water3. Inform you teacher ASAP4. Connect the colorimeter to the Labquest5. Turn on the Labquest6. Set the wavelength to 470 nm using the <> arrows on the colorimeter7. Allow the colorimeter to warm up for 5 minutes8. Sensor set up

a. Select sensor > Data Collection> Mode> Time Based> b. Rate = 1 sample/ secondc. Interval = 1 sample / secondd. Duration = 200 seconds

9. Colorimetera. Prepare a blank: In this case the blank is the Fe3+ ion solution. Fill the cuvette 3/4th with the

blank. Close the cuvette.b. Place it in the colorimeter; the clear side of the cuvette should face the white triangle of the

colorimeter. Close the colorimeter. c. Press calibrate. It is a one button calibration.d. When the red light stops blinking and the absorbance on the Lab quest is 000 the

instrument is calibrated.10. Now prepare solutions for one trail at a

time and perform data collection for all the three trials, use Table 1 data. Use 50 mL beakers and measuring pipettes.

11. Data Analysis on the Labquest: Open Run 1 Select a segment of the graph for 30 seconds (50 seconds to 80 seconds as shown in the video) Select analyze Choose curve fit Absorbance Linear Now write down the value of

‘m’ or slope of line in the data table Next select OK Choose Run 2 and repeat the process until you find the slopes for all the three runs. Record the

data. Once you have the values you can calculate the order of the reaction using the calculation page

12. Dispose the reagents you have mixed in the cans placed in the fume cupboard. Wash glassware and return to appropriate locations.


Table 1 Dilution guideline

Trial FeCl3 (mL) KI (mL) H2O (mL)

1 10.0 10.0 0.02 10.0 5.0 5.03 5.0 10.0 5.0

Trial [Fe3+] M [I-] M Initial rate (s–1) = m

1 0.01 0.012 0.01 0.0053 0.005 0.01

Teacher Notes The order of the reaction is 1 with respect the iodide ions [I -] and zero with respect to Fe3+

The rate law. Rate = k[Fe3+]0[I-] Prepare 0.02 M Fe3+ by dissolving 8.0808 grams of Fe(NO3)3

.9H2O in 0.1 M HNO3 or you can dissolve the compound in water and add 100 mL of 1 M HNO3 before making up the solution. (This has to be done by the teacher)

Prepare 0.02 M KI solution by dissolving 3.3201 g KI in 1 liter using distilled water.

Note: When the slope is determined after collection of data for all three runs, you get the slope for the same time segment for all three runs. This will work positively if the time between start of experiment and data collection (pressing the play button for data collection) are the same. Use a stops watch if need be.


Resources for Sharing and CollaborationFor Sharing and Collaboration you may use the Yapp app. After you download it from iTunes or google play

Select “I have been invited to yapp”

Enter the following at the end of the url CDK45Z

And you will be connected to the Eureka 2015 app for this workshop.

You will have all the necessary information there.

Have a QR Code Reader then this is for you.

Facebook page, link given below.

Chemistry and Chocolates: http://goo.gl/uVtuYe

QR Code for Chemistry and Chocolates

For Downloads of the lab and excel workbook

http://goo.gl/Xu6EUk

Password for access is eureka2015


http://goo.gl/Xu6EUk

http://goo.gl/uVtuYe

· Web viewThe objective of this experiment is to determine the order of a reaction. For this we will look at the redox reaction between Fe3+ ions and I- ions. ... The I 2 produced

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