Group No. 3
III-Magnesium III-Magnesiu m
Cortez, Jesseyriche Isaiah’l B.
28 January 2013 Experiment No. 28
A Study of Reaction Rates: The Iodine Clock Reaction
I.
Objectives The objectives of this experiment is to observe the effects of concentration and temperature on
the reaction times of reactions. reac tions. This includes the plotting of results on a graph.
II.
Equipment and Materials -
III.
2 test tubes 1 400-mL beaker 2 graduated cylinders (10 and 25 mL) 2 thermometers (-10°C to 120°C) 1 stopwatch 1 gas burner 2 10-mL pipettes 2 20-mL beakers
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1 iron ring 1 iron stand 1 wire gauze ice distilled water 600 mL solution A (4.3g KIO3/L) 1 L solution B (0.2g Na2S2O5, 4g starch, and 5 mL 1 M H2SO4/L)
Procedure
Part I: The Effect of Concentration Changes
Using a clean pipet, 10.0 mL of Solution A was added into a 20-mL beaker.
Using a clean pipet, 10.0 mL of Solution B was added into i nto another 20-mL beaker.
Solution A was poured into the beaker containing Solution B, and poured back and forth three times.
The time it took for a reaction to take place was recorded.
Five other solutions were prepared by adding 9.0, 8.0, 7.0, 6.0, and 5.0 mL of solution A to 1.0, 2.0, 3.0, 4.0, and 5.0 mL of water, respectively.
The mixing and observing were repeated for the five new solutions
Part II: The Effect of Temperature
Using a clean pipet, 10.0 mL of Solution A was added into a 20-mL beaker.
Using a clean pipet, 10.0 mL of Solution B was added into another 20-mL beaker.
Solution A was poured into the beaker containing Solution B, and poured back and forth three times.
The time it took for a reaction to take place was recorded.
Depending on the temperature given by the teacher, the chemicals were cooled/heated using an ice/hot water bath. (Cooled for our group)
Steps 1-4 were repeated for the cooled/heated chemicals a total of eight times.
IV.
Data and Results
I. The Effect of Concentration Changes Solution A
H2O
Solution B
10.0 mL 9.0 mL 8.0 mL 7.0 mL 6.0 mL 5.0 mL
0.0 mL 1.0 mL 2.0 mL 3.0 mL 4.0 mL 5.0 mL
10.0 mL 10.0 mL 10.0 mL 10.0 mL 10.0 mL 10.0 mL
Concentration of Solution A in A + B 50% 45% 40% 35% 30% 25%
Time of Reaction (in s) 37.2 46.5 47.3 46.4 60.7 71.1
II. The Effect of Temperature Temperature
5oC o 10 C o 15 C 20oC Room Temp 35oC 40oC
Time of the reaction (in s) for trial number 3 4 5 6
1
2
171.00 83.00 62.00 64.00 40.70 38.80 27.83
160.00 80.00 60.00 48.20 36.54 33.40 25.40
140.00 93.00 60.00 50.30 34.57 41.50 27.28
-58.00 61.00 48.80 40.30 45.50 36.23
--63.00 42.06 40.30 45.50 36.23
--62.00 54.00 38.71 31.20 28.53
7
8
--64.00 58.10 30.68 37.60 27.57
--70.00 45.20 44.60 74.90 27.73
Average time of reaction (s) 157.00 78.50 62.64 51.00 38.05 38.89 28.63
IV.
Discussion / Data Analysis
Part I. 1. The concentration of KIO 3 in Solution A is 0.02 M. Calculate the number of moles KIO 3 in each mL of Solution A 0.02 M means 0.02 moles per liter . This leads to the equation: 0.02 moles x 1 liter liter
-5
= 2.0 x 10 moles per mL.
1000 mL
2. Calculate the initial molar concentration of KIO 3 in each of the mixtures A plus B prepared in Concentration of Solution A 10.0 9.0 8.0 7.0 6.0 5.0
Concentration of KIO3 46.01 % 41.41 % 36.81 % 32.21 % 27.61 % 23.01 %
3. Why is it important to keep the total volume of 10 mL during the dilution of Solution A? It is important to keep the volume of the Solution A and its diluted variants constantly at 10 mL so that the results can be as accurate as possible. Changing the total volume of the Solution A mixtures will mess with the results, making them less accurate.
4. Plot the graph of the concentration-time data with time on the vertical axis (ordinate) and the concentration of the KIO3 on the horizontal axis (abscissa). See attached graphing paper.
5. What generalizations can you make concerning the effect of varying the concentration on the time of the reaction? The lower the concentration of Solution A, the higher the time it takes for a reaction to happen becomes. In the same line of reasoning, the higher the concentration, the lower the reaction time becomes.
6. How is the time of the reaction related to the rate of reaction? They are inversely proportional. The higher the time of re action is, the lower the rate of reaction is. And in the same way, the lower the time of reaction is, the higher the rate of reaction is.
Part II. 1. Plot a graph of the temperature-time data with temperature on the horizontal axis (abcissa) and time on the vertical axis (ordinate). See attached graphing paper.
2. What general relationship can you derive from the graph? The higher the temperature, the lower the time of reaction becomes. In the same way, the lower the temperature, the higher the time of reaction becomes.
3. Make a prediction on the time of the reaction at 0 oC and at 50oC assuming that the other variables in the experiment are kept constant. o
I predict that the time of reaction at 50 C will be playing around the 20 s line, and the reaction o
time at 0 C will be playing around at the 3 minutes area, or the 180 s area.
V.
Conclusion After the experiment, it can be concluded that temperature and concentration both affect the
reaction times of solutions, albeit indirectly.
VI.
References Houston, P. (2006), Chemical Kinetics, Chemical Kinetics and Reaction Dynamics, Dover Publications, Mineoda, New York Brown, T.L., Burdge, J.R., Bursten, B.E., & Lemay, H.E. (2003). Chemistry: the central science ninth edition. New Jersey: Pearson Education Inc. Baguio, S.S.M., & Vergara, L.F. (1995). Chemistry and technology laboratory manual. Quezon City: Marren Publishing House Inc. Chang, R. (1994). Chemistry fifth edition. New York: McGraw-Hill Companies Inc.
