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Lab
Activity 13: Concentration and Rate of a Chemical Reaction
Background:
The study of reaction rates is a part
of chemical kinetics. In this investigation, you will perform the same
reaction 5 times. Each time, however, you will use a different concentration
of potassium iodate. By measuring the amount of time it takes for the
reaction to occur at each concentration, you will see how changes in concentration
affect the rate of a chemical reaction.
You will begin the reaction by mixing a potassium iodate solution (Solution
A) with a NaHSO3-starch solution (Solution B). This reaction results in
the formation of free iodine. The presence of free iodine can be detected
by the blue-black color that results when it begins to react with the
starch (from Solution B).
Purpose:
To determine how the concentration of a reacting substance controls the
rate of a chemical reaction in which it takes part.
Materials:
| -10 ml graduated cylinder |
-2 large test tubes |
-test tube rack |
| -KIO3 solution A |
-NaHSO3-starch solution B |
-watch/timer |
Safety:
Always wear safety goggles and a lab apron
or coat when working in the lab.
Procedures:
Part I
1. Use a graduated cylinder to measure 6.0 ml of solution A and pour it
into a large test tube. Rinse the cylinder and measure 6.0 ml of solution
B and pour it into a second large test tube.
2. Pour the sample of solution A into the sample of solution B and back
again into the empty test tube. Use a timer to record the time to the
nearest second, when the solutions show the first sign of the presence
of iodine (the appearance of a blue-black color.)
3. Record this time to the nearest second and calculate the amount of
time it took for the reaction to occur.
4. Repeat steps 1-3 until you get two, consecutive close measurements
of the reaction time. (Now you are a master at mixing the two solutions.)
Part II
1. Use a clean graduated cylinder to measure the first concentration of
solution A shown on the table below. Pour this concentration of solution
A into a large test tube. Rinse the cylinder. Measure 3 ml of Solution
B and pour it into the second large test tube.
2. Pour the test tube with Solution A into the test tube of Solution B
and back again into the empty test tube. . Use a timer to record the time
to the nearest second, when the solutions show the first sign of the presence
of iodine (the appearance of a blue-black color.)
3. Repeat procedures 1-2 for each of the concentrations listed on the
table below. Keep the quantity of solution B constant and remember to
begin timing the reaction when the two solutions first come into contact
with each other.
Table 1: Reaction Rate
| Solution
A (ml) |
Solution
B (ml) |
Water
(ml) |
Total
vol. (ml) |
Total
Time (sec ) |
Speed
(1/time) |
| 6 |
3 |
1 |
10 |
|
|
| 5 |
3 |
2 |
10 |
|
|
| 4 |
3 |
3 |
10 |
|
|
| 3 |
3 |
4 |
10 |
|
|
| 2 |
3 |
5 |
10 |
|
|
SFP
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