In This Experiment, You Will Determine the Order with Respect to the Concentration of Iodate

Name______Date______

KINETICS LAB

Introduction

In this experiment, you will determine the order with respect to the concentration of iodate (IO3–) and a value for the rate constant for the following reaction:

5 HSO3– + 2 IO3– → I2 + 5 SO42– + H2O + 3 H+

rate = k [IO3–]x [HSO3–]1

You will start with colorless solutions, which will change color shortly after being mixed. The color is produced by a separate reaction between elemental iodine and starch.

Materials

solution #1: 0.048 M KIO3

solution #2: 1% starch and 0.032 M NaHSO3

10, 50, and 100 mL graduated cylinders

250-mL Erlenmeyer flasks

deionized water

timer

Procedure

It is essential that the two solutions not be mixed in any way until you are ready to run the experiments. Do not mix up the graduated cylinders used for solution #1 and solution #2.

The general procedure for each experiment is as follows:

1. According to the data table, measure the appropriate amount of solution #1 in the 50-mL graduated cylinder and place it in a clean Erlenmeyer flask. Add to the flask the appropriate amount of deionized water.

2. In a clean 10 mL graduated cylinder, measure 10 mL of solution #2.

3. Pour the measured amount of solution #2 into the flask containing solution #1 and deionized water. Immediately begin the timer and gently swirl the solution until a reaction is observed.

4. Once the reaction has taken place, record the time in seconds on the data table.

Follow this procedure for each experiment listed in the data table. Complete two trials for each experiment.

The completed trials may be poured down the drain. When the experiment is completed, thoroughly rinse all flasks and graduated cylinders with tap water.

Calculations

1. Determine the average time for each experiment and enter the results into the data table.

2. The concentration of IO3– before the experiment is 0.048 M. Calculate the initial molarity of IO3– for each experiment.

exp #1:

exp #2:

exp #3:

exp #4:

3. The initial concentration of HSO3– is 0.0032 M. To determine the initial rate for each experiment, divide this concentration by the average time for each experiment.

exp #1:

exp #2:

exp #3:

exp #4:

4. Complete the following table:

Exp #

5. What is the order of the reaction with respect to IO3–?

6. Write the rate law and calculate a value for the rate constant, k.