Accelerated Chemistry Chapter 17 Name ______
Kinetics Lab – “The Iodine Clock Reaction”
Introduction: The iodine clock reaction is an excellent reaction to study when learning about kinetics. The reaction shows a sudden burst of color, but only after a period of time. We will study this reaction to learn about the effect of changing concentration and temperature on reaction time.
Materials: Solution A (part I) is made by mixing 14.33 g of KIO3 in 2 L of solution.
Solution A (part II) is made by mixing 1 part solution A with 1 part water.
Solution B is made by boiling 2400 mL of water, then slowly adding 10 g of starch (iodometry starch) mixed with 50 mL of cold water. When the solution is cool, adding .5 g of NaHSO3. The morning of the experiment, add up to 10 mL of 1.0 M H2SO4 so that the reaction between A and B takes between 10 and 20 seconds.
2 graduated cylinders (one for A, one for B), thermometer, hot plate, ice, 2 250 mL beakers (hot and cold water bath), 3 beakers (150 mL beaker for obtaining 130 mL of solution B – 100 mL beaker for obtaining 55 mL of solution A part I – a 50 mL beaker for obtaining 30 mL of solution A part II), 3 small pipettes for accurately measuring solutions A and B, stopwatch, 4 test tubes and test tube rack.
Lab Requirements:
1. Complete all data tables.
2. Complete all graphs on 1 piece of graph paper. Make sure that all graphs are properly labeled. Staple your graph to the back of this handout.
3. Answer the questions asked in the lab.
Procedure (Part I): The effect of concentration on reaction rates
1. Use a 150 mL beaker for obtaining 100 mL of solution B, and a 100 mL beaker for obtaining 55 mL of solution A part I.
2. Carefully measure the prescribed amounts of solution A and water in one graduated cylinder. Do the same for solution B. Once you’ve measured, pour each solution in a separate test tube.
3. You now need to mix the two test tubes and time the reaction. Start the timer as soon as one solution touches the other. Pour one test tube into the other, pour back into the empty test tube, then repeat. Wait for the reaction to happen, and hit stop on the timer when it does. Record your time (to the nearest tenth of a second) in the data table below.
4. Rinse out your test tubes well. Dispose of the contents in the sink.
5. Repeat steps 2 and 3 for all of the trials in the data table. When diluting, add solution A to the graduate first, then add water drop by drop from the sink.
Data Table 1
mL Solution A / mL water / mL Solution B / Time (sec) / Rate (1/sec)10.0 / 0
/ 10.0
9.0 / 1.0
/ 10.0
8.0 / 2.0 / 10.0
7.0 / 3.0
/ 10.0
6.0 / 4.0 / 10.0
5.0 / 5.0 / 10.0
4.0 / 6.0 / 10.0
3.0 / 7.0 / 10.0
2.0 / 8.0 / 10.0
1.0 / 9.0 / 10.0
6. Draw each of the following graphs on one side of graph paper:
A. Concentration of solution A (x-axis) vs. time (sec)
B. Concentration of solution A (x-axis) vs. rate (1/sec)
*** Note: For the concentration of A, multiply the mL A in the data table by 10. Your first concentration will be graphed as 100%, your second trial 90%, etc. These concentrations are % volume.
Part II: The effect of temperature on reaction rates
1. Carefully read all directions for this part before beginning.
2. Use a 100 mL beaker to obtain 30 mL of “special” solution A. Use a 50 mL beaker to obtain 30 mL of solution B.
3. Mix 10.0 mL of solution A with 10.0 mL of solution B at three different temperatures and record the reaction times. Make one of your temperatures room temperature (use your thermometer to measure air temperature). Use an ice bath to conduct a test at a lower temperature. Use a hot plate to create a hot water bath for the higher temperature test. Do not heat the test tubes above 35 oC!!!
4. When using a water bath, make sure that you place your still separate test tubes of A and B in the bath for a few minutes before beginning the reaction so the solutions can equalize in temperature. Once they have equalized, mix back and forth as you did in part I, then return them to the bath until the reaction is completed.
5. Record your answers in the table below (Data Table 2), then write them on the board. Next copy the class data in the table below Data Table 3):
Data Table 2
Time / TemperatureData Table 3
Time / Temperature / Time / Temperature4. Draw the following graph on the back of your graph paper:
Make a graph of temperature (x-axis) vs. time(sec).
Note: Make a graph of your data (use pen to mark your points and make a small circle around your points. Make the best line you can to show the relationship between temperature and time. Next graph the class data. Use pencil to mark those points and use a pencil to make the best line you can to show the relationship between temperature and time.
Questions:
1. What is the name of the theory that explains the results of this lab?
2. What is the effect of dilution on reaction time?
3. What is the effect of dilution on reaction rate?
4. What is the effect of temperate on the time of reaction?
5. Draw three simple graphs below (label axis, but don’t use #s) that show the relationships explored in this lab.
Graph 1 Graph 2 Graph 3
This lab can be done as a dry lab. Give the kids the data and let them complete the lab.
mL Solution A / mL water / mL Solution B / Time (sec) / Rate (1/sec)10 / 0
/ 10.0 / 7.0
9 / 1.0
/ 10.0 / 9.0
8 / 2.0 / 10.0 / 12.0
7 / 3.0
/ 10.0 / 14.0
6 / 4.0 / 10.0 / 15.0
5 / 5.0 / 10.0 / 18.0
4 / 6.0 / 10.0 / 21.0
3 / 7.0 / 10.0 / 28.0
2 / 8.0 / 10.0 / 42.0
1 / 9.0 / 10.0 / 84.0
Time / Temperature
23.0 / 33.0
33.0 / 8.0
35.0 / 4.0
28.0 / 21.0
28.0 / 22.0
33.0 / 6.0
28.0 / 16.0
27.0 / 30.0
18.0 / 34.0
27.0 / 24.0
31.0 / 22.0
36.0 / 1.0
31.0 / 13.0
26.0 / 27.0