Iodine Clock Reaction

Iodine Clock Reaction

Lab #18

Purpose: To mix different solutions to see how increasing the concentration changes the reaction rate.

Materials:

·  250 ml beaker, a 50 ml beaker and 50 ml flask

·  Graduated cylinder

·  Solution B: Na2S2O5 solution with starch & 5mL of 1M H2SO4 made with 0.22g of Na2S2O5 and 4g of starch in 1L deionized H2O. (Note add the H2SO4 day of the lab.)

·  Solution A: KIO3 solution made with 4.4g KIO3 dissolved in 0.6L of deionized H2O.

·  Catalyst solution: Ammonium molybdate (VI) tetrahydrate 0.176g per 100mL of water

Procedure:

1.  Clean 250 ml beaker, a 50 ml beaker and 50 ml flask.

2.  Fill a 250 ml beaker with deionized water.

3.  Trial #1: Add 2 ml solution A and 8 ml deionized H2O to a flask. Add 10 ml of solution B to a separate beaker. Mix the solutions in the flask and record the time in seconds until the color changes.

4.  Trial #2: Add 4 ml solution A and 6 ml deionized H2O to a flask. Add 10 ml of solution B to a separate beaker. Mix the solutions in the flask and record the time in seconds until the color changes.

5.  Trial #3: Add 6 ml solution A and 4 ml deionized H2O to a flask. Add 10 ml of solution B to a separate beaker. Mix the solutions in the flask and record the time in seconds until the color changes.

6.  Trial #4: Add 8 ml solution A and 2 ml deionized H2O to a flask. Add 10 ml of solution B to a separate beaker. Mix the solutions in the flask and record the time in seconds until the color changes.

7.  Trial #5: Add 10 ml solution A to a flask. Add 10 ml of solution B to a separate beaker. Mix the solutions in the flask and record the time in seconds until the color changes.

8.  Trial #6: Testing a catalyst. Add 2.0 ml of solution A, 0.5 ml of Catalyst, and 7.5 ml deionized H2O to a flask. Add 10 ml of solution B to a separate beaker. Mix the solutions in the flask and record the time in seconds until the color changes

Data: Trial Time (sec)

Trial #1

Trial #2

Trial #3

Trial #4

Trial #5

Trial #6

Analysis:

Show the calculations for how you would calculate the molarities KIO3 and Na2S2O5 stock solutions?

Calculate the molarity of Solution A in trials 1-5.

Plot the Molarity of solution A versus time for solution A for trial 1-5. This graph will have 5 points. Plot concentration on the y-axis and time on the x-axis. (Graph should be 1/2 page).

Conclusion:

Does the plot make a straight line? What does a catalyst do for the reaction? How did the concentration of solution A control the rate?