Description
https://www.youtube.com/watch?v=KWJpKNQfXWo
Here is a simulator (requires flash): http://introchem.chem.okstate.edu/DCICLA/iodine_clock.html. To use the simulator, you select your reactants, always totaling 100 mL in this case (instead of 20.0 mL in our experiment), click start, and then, when the solutions are all in the reaction beaker, click to start the timer. Watch for the color change to turn OFF the timer. You can see the times based on concentration of each reactant, as well as temperature, just like our data from lab. This is just a demo to show you what the lab work is like. We do not use any data from this simulator.
The data we take in the lab is simply the time until we see the color change. The time is influenced strongly by consistent stirring and the timing of the stopwatch turning on/off. After you complete the pre-lab quiz online, you will get access to data to use in your notebook for the post-lab work.
Here’s a video overview of the lab: https://www.youtube.com/watch?v=li0jcKXrkfQ
You will make your own stock solution of sodium bisulfite and potassium iodate (Part I) and then use these stock solutions to create your reaction mixtures for trials #1 – 10. Do not make the solutions in Part I more than once. One solution will be made from a solid, the other will be made by diluting an aqueous solution.
Weighing a solid: It’s handy to fold the weigh paper into quarters so you can easily guide the solid into the flask. Your value does not have to match the expected value exactly– just write the actual mass used. Take the weigh paper out of the balance when you add more solid so you will not spill chemicals inside the balance. Make sure you have at least 3 decimal place (“milligram” balance”).
Work in pairs, and keep track of the two 10-mL cylinders to avoid contamination between solutions. Part II requires three trials of the same volumes of each stock solution. Note that the two solutions dilute each other when mixed, and you will calculate the new concentration of each reactant at the moment it is combined with the other solution. Use M1V1 = M2V2 and notice the final volume is the same for each trial.
For every trial, combine the reactants and start the stopwatch at that exact moment. Write the time at which the color changes. Look for initial color change, whether it is a light color or a dark color.
Part III requires the use of different volumes of each solution. Again, you will calculate the new, diluted concentration of each reactant at the moment it is mixed with the other solution. (What is the total volume now?) Don’t forget to reflect proper significant figures in your measurements!
Part IV requires repeating the initial volume combination at two additional temperatures. For the warmer temperature, keep your eyes on the solution– it can change pretty fast!
For the calculations on page 85, show a single calculation for a single trial with your lab report. The rest of the calculations may be shown in your notebook.
