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?