Reaction Rates Laboratory
Purpose: To determine the effects of concentration and catalysts on the rates of chemical reactions.
Theory:
The concentration of reactants, as well as catalysts, have a profound effect
on the rates at which chemical reactions proceed. The following net ionic reactions
will take place one after the other in varying concentrations and with a catalyst
present to examine these effects.
Solution B is the limiting reagent (S2082-,above in bold) is the limiting reagent. Solution B also contains starch so that when it is depleted, I2 collects in excess and forms a deep blue color with the starch, indicating the completion of the reaction. The catalyst used will be CuS04(aq).
Materials:
(3) 10 mL graduated cylinders
100 mL beaker
stopwatch
dropping pipet
stirring rod
pen/pencil
apron
safety goggles
Reagents
Solution A: 0.20 M KI (aq)
Solution B: 0.0050 M NG25203 (aq) (starch)
Solution C: 0.10 M (NH4)25208 (aq)
Catalyst: CUS04 (aq)
Deionized or Distilled Water
Procedure:
Part 1:
1. Place 5 mL of Solution B into the beaker.
2. Pour A & C into the beaker in the concentrations listed for each appropriate
trial in the table below.
3. Begin timing immediately, and stir the mixture.
4. At the first sign of color, record the time in the data table below.
5. Rinse the beaker between each trial, first with tap water, and then with
deionized or distilled water.
Table 1
| Trial | Solution A (mL) | Solution B (mL) | Solution C (mL) | time (s) |
| 1 |
10
|
5
|
10
|
|
| 2 |
7.5 + 2.5 water
|
5
|
10
|
|
| 3 |
5.0 + 5.0 water
|
5
|
10
|
|
| 4 |
2.5 + 7.5 water
|
5
|
10
|
|
| 5 |
10
|
5
|
7.5 + 2.5 water
|
|
| 6 |
10
|
5
|
5.0 + 5.0 water
|
|
| 7 |
10
|
5
|
2.5 + 7.5 water
|
Part 2
Add 2 drops CuS04 to Solution C before each reaction. Then proceed from step 1 from Part 1.
Table 2
| Trial | Solution A (mL) | Solution B (mL) | Solution C (mL) | time (s) |
| 8 |
10
|
5
|
10.0 + cat
|
|
| 9 |
7.5 + 2.5 water
|
5
|
10.0 + cat
|
|
| 10 |
5.0 + 5.0 water
|
5
|
10.0 + cat
|
|
| 11 |
2.5 + 7.5 water
|
5
|
10.0 + cat
|
Data Analysis:
At a computer, go into MSExcel. Make a workbook containing the following data columns, and enter their appropriate data, where possible. Trial, Solution A (mL), Solution A (M), Solution B (mL), Solution B (M), Solution C (mL), Solution C (M), time (s). Use the formula bar, as you have learned in previous classes, to calculate the concentration for the (M) columns of each Solution. Next, insert a chart graphing the concentration of Solution A (y axis) vs. time using the data for trials 1-7. Next, insert another chart graphing Solution C concentration (y-axis) vs. time (x-axis), using Trials 1-7. Use the XY Scatter or Line graph choices for your graphs. Name these graphs "UNCATALYZED REACTION." Next, create two more charts in the same manner, but this time make the graphs for trials 8-11, the catalyzed reaction. Name these graphs "CATALYZED REACTION." When all four charts are in your table and properly labeled on each axis, print them, add this to your laboratory sheet to be turned in.