Kinetics of the Iodine Clock Reaction Objective To fully determine the rate law for the iodine clock...
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![Page 1: Kinetics of the Iodine Clock Reaction Objective To fully determine the rate law for the iodine clock reaction using the method of initial rates.](https://reader035.fdocuments.in/reader035/viewer/2022081813/56649e7b5503460f94b7cecc/html5/thumbnails/1.jpg)
Kinetics of the Iodine Clock Reaction
Objective• To fully determine the rate law for the
iodine clock reaction using the method of initial rates
![Page 2: Kinetics of the Iodine Clock Reaction Objective To fully determine the rate law for the iodine clock reaction using the method of initial rates.](https://reader035.fdocuments.in/reader035/viewer/2022081813/56649e7b5503460f94b7cecc/html5/thumbnails/2.jpg)
The Reaction
The Rate Lawx,y,z are the orders of reaction
k is the rate constant
A is the collision factor
Ea is the Activation energy
![Page 3: Kinetics of the Iodine Clock Reaction Objective To fully determine the rate law for the iodine clock reaction using the method of initial rates.](https://reader035.fdocuments.in/reader035/viewer/2022081813/56649e7b5503460f94b7cecc/html5/thumbnails/3.jpg)
The Reaction
The Rate
These are colorless
![Page 4: Kinetics of the Iodine Clock Reaction Objective To fully determine the rate law for the iodine clock reaction using the method of initial rates.](https://reader035.fdocuments.in/reader035/viewer/2022081813/56649e7b5503460f94b7cecc/html5/thumbnails/4.jpg)
How will we measure the Rate?
• We could monitor [I2]t using UV/VIS spectroscopy
• But we will instead use the I2 clock reaction and the method of initial rates
![Page 5: Kinetics of the Iodine Clock Reaction Objective To fully determine the rate law for the iodine clock reaction using the method of initial rates.](https://reader035.fdocuments.in/reader035/viewer/2022081813/56649e7b5503460f94b7cecc/html5/thumbnails/5.jpg)
What is the I2 Clock Reaction?
• To the reaction we add thiosulfate S2O32-(aq)
• S2O32-(aq) reacts very fast with any I2
• Only when all the S2O32-(aq) is used up do we
start to see I2
![Page 6: Kinetics of the Iodine Clock Reaction Objective To fully determine the rate law for the iodine clock reaction using the method of initial rates.](https://reader035.fdocuments.in/reader035/viewer/2022081813/56649e7b5503460f94b7cecc/html5/thumbnails/6.jpg)
Why do we add Starch?
• In addition to thiosulfate we will be adding a small amount of starch
• Starch is an indicator for I2
• In the presence of I2 starch turns blue/black
• This will help us to see the I2 when all the thiosulfate is used up
![Page 7: Kinetics of the Iodine Clock Reaction Objective To fully determine the rate law for the iodine clock reaction using the method of initial rates.](https://reader035.fdocuments.in/reader035/viewer/2022081813/56649e7b5503460f94b7cecc/html5/thumbnails/7.jpg)
Measuring the Rate• We have 3 reactions going on simultaneously
• As soon as all the S2O32- is used up I2 stays in solution
and reacts with starch and the solution turns green/blue/black
![Page 8: Kinetics of the Iodine Clock Reaction Objective To fully determine the rate law for the iodine clock reaction using the method of initial rates.](https://reader035.fdocuments.in/reader035/viewer/2022081813/56649e7b5503460f94b7cecc/html5/thumbnails/8.jpg)
Measuring the Rate• We measure the time it takes for the solution to change
color
• This is the time it takes all of the [S2O32-]o to get used up
![Page 9: Kinetics of the Iodine Clock Reaction Objective To fully determine the rate law for the iodine clock reaction using the method of initial rates.](https://reader035.fdocuments.in/reader035/viewer/2022081813/56649e7b5503460f94b7cecc/html5/thumbnails/9.jpg)
Measuring the Rate
• Measure the time Δt it takes to turn blue then the rate is calculated as
![Page 10: Kinetics of the Iodine Clock Reaction Objective To fully determine the rate law for the iodine clock reaction using the method of initial rates.](https://reader035.fdocuments.in/reader035/viewer/2022081813/56649e7b5503460f94b7cecc/html5/thumbnails/10.jpg)
Method of Initial Rates
• Make up flask 1 and flask 2 for a given mixture
• Pour flask 2 into flask 1 and start timing• When solution starts to appear colored
stop timer• The time on the stop watch is Δt• Write time on board• Measure T(oC)• Dispose down sink • Repeat second trial
![Page 11: Kinetics of the Iodine Clock Reaction Objective To fully determine the rate law for the iodine clock reaction using the method of initial rates.](https://reader035.fdocuments.in/reader035/viewer/2022081813/56649e7b5503460f94b7cecc/html5/thumbnails/11.jpg)
Day 2: Getting Ea and A
ignition tubes
hotplate
reaction vessel 2reaction vessel 1
thermometer
• Allow the contents of vessel 1 and vessel 2 to reach thermal equiibrium with the water• Add the contents of vessel 2 into vessel 1 – and leave it in the beaker• Stir with the thermometer
• 2 measurements above RT• 2 measurements below RT• 2 measurements at RT• Write T(oC) and Δt on board• Use class data