Name _________________________________ Hour________ Iodine Clock Reaction Lab Chemistry Calculate the molarity (M) of each of the reactants used in the lab:  I use 1 gram of NaHSO3 to make 1 liter of solution. Answer: ________________________  I use two grams of KIO3 to make 1 liter of solution. Answer: _________________________ Net ionic equation: 2IO3- + 5HSO3- + 2H+  I2 + 5HSO4+ + (Na and K are spectator ions so do not show up in the net ionic equation) In this reaction starch binds to the IO3- and is colorless. When all of the IO3- reacts and is converted into products is when you notice the color change. Instructions 1. Rinse out all graduated cylinders and beakers with tap water AND dionized water before you start 2. Fill the RED graduated cylinder with 10 mL of HSO3- using the pipette in the larger beaker. Fill the YELLOW with 10 mL of IO3- using the pipette in the large beaker. It is VERY important that you keep the pipettes in the CORRECT large beakers or you will contaminate the solutions!! 3. Pour each graduated cylinder into a separate small beaker. 4. Pour the two liquids together. Start the timer right when the liquids hit each other. Move the liquids back and forth between the two beakers three times and set the beakers onto the lab bench. 5. Stop and record the time right when the color changes. 6. Rinse out the two beakers with tap water and dionized water. Repeat the procedure for trials 2-4. Remember both the water and IO3- go in the yellow graduated cylinder. 7. Once you have completed all trials, experiment with the amount of IO3- and water to get your reaction to change color in your assigned amount of time. You must ALWAYS use 10 mL of HSO38. Once you think you have the correct concentrations, set up the experiment one last time, call the teacher over to record your final time. How close you are to your assigned time is a large portion of your grade. 9. Clean your station, fill out the data table, and answer the questions on the back of this sheet. Data Trial mL of HSO3- mL of IO3- mL of H2O 1 10 10 0 2 10 8 2 3 10 6 4 4 10 4 6 Assigned time: _____________________ Time (s) Rate (1/time) Actual time: ____________________ (timed/recorded by teacher) Questions 1. Use this space to write down data for additional trials you did to find your assigned time. Once you had your actual time recorded, write the amount of each of the reactants you used at the bottom HSO3- _____________ IO3- _____________ water _____________ 2. In trials 1-4 you are adding more water each time. This water is changing the concentration of which of your reactants? Is it increasing or decreasing the concentration? Explain your answer. 3. Why do you think the amount of HSO3- in the reaction must stay at 10 mL? Hint: why can you not change that variable also? 4. How does the concentration of reactants affect the rate of a reaction?