Introduction to qualitative analysis lab answers

This will be important, because for mixtures 1–3, you need to do all three runs at the same temperature. Record the temperature of the bath in your lab notebooks. 1–10 Chemistry 142 Grossmont College The Experiment Prepare a table in you lab notebook to record the data. The table should look something like this: TABLE 1.2 time interval (min.) Mix #2 Temp Mix #3 Temp Mix #4 Temp Mix #5 temp Mix #6 temp volume reading volume reading volume reading volume reading volume reaching volume reading E PL M SA 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 Mix #1 Temp When all is ready, pour the hydrogen peroxide into the reaction mixture, raise the beaker or leveling bulb to somewhere near the top reading on the buret or gas tube and seal up the system. Once you bring the level of the beaker of leveling bulb to the same height as the liquid in the buret, take your first reading. It is not necessary to take readings in the first few seconds, so it is more important to get a good reading than to take a reading as fast as possible. Because the water level will be moving, you will only be able to measure the volume to within ± 0.1 mL. While one member of your group is recording data, another should be swirling the Erlenmeyer flask at as constant a rate as possible. If mixture #1 is stirred much less rapidly than mixture #3, this will affect your results. Continue reading data every thirty seconds (being sure to equalize the water level each time) for ten minutes or until at the water level in the buret has dropped at least 35 mL. Re-measure the temperature in the bath. Your temperature will be the average of that measured before and after the experiment. Repeat the procedure for mixture #2 and #3, being sure to record the temperature before and after the run. The effect of changing temperature on the rate of decomposition of H2O2. Repeat the procedure, using the same volumes of reagents as that used in mixture #1 at three other temperatures. The minimum temperature should not be below 5 degrees centigrade, and the maximum temperature should not be above 45 degrees. For example if your room temperature data was collected at 21.2 °C, you could do runs at 12 °C, 30 °C and 40 °C (remember to always record your temperature Chemistry 142 Grossmont College 1–11 The Kinetics of the Dissociation of Hydrogen Peroxide to the maximum precision the thermometer allows). In these runs it is especially important to let the solutions equilibrate at the temperature of the water baths. The solutions should be allowed to equilibrate for at least three minutes. Hopefully, the cold or hot water baths will be at a fairly constant temperature. Be sure to record the temperature both before and after each run, and take an average. Calculations The first step in performing the calculations is to prepare plots of volume versus time for all six runs. If your graphing routine allows, you can plot all six runs on the same graph. Another option is to plot runs 1-3 on one graph and runs 1, 4, 5, and 6 on another. Be absolutely sure you know which curve corresponds to which run, and label your graph so that it is clear which is which as well. For each of your runs, determine the maximum slope of the graph. You may do this by hand using a ruler and getting the slope from calculating the rise over the run. Alternatively, you may use VernierGraph to determine the maximum slope of the curve. In any case, report the maximum slope of each run. This is the initial rate of the reaction. Be careful about the units of the reaction rate. It would be helpful to record the results in a table. Next, use the method of initial rates and your room temperature data to determine the order of the reaction with respect to each of the reactants. Whatever mathematical method you use to extract these orders, do not round off to an integer or to a half-integer at this point. Once you have the orders, report your rate law for the reaction you studied. At this point, go ahead and round the orders to the nearest integer or half-integer. Now that you have the rate law, calculate the rate constant for each of your six runs. Again, be careful about ...