Hydrogen Peroxide and Iodide Kinetics Essay

(Be sure to state references for any cited value at the end of this report. Additionally, all report material must be in INK – pencil or white-out will render the work ineligible for mark appeal) 1.What observations and conclusions can you note about each of the three reactions that occurred in the test tubes where you combined potassium iodide, KI, and hydrogen peroxide, H2O2 (in part 1) of the experiment? (Give a detailed explanation of any observations that you made, i.e., what made the colour change, what reactions happened?) ANSWER: 2.Use the information below to develop the necessary calculations for the rate of reaction from the solutions in part B of the experiment †¢Calculate the initial molarity of iodide ion in each of the solutions, once your solutions are mixed. Remember: The KI stock solution concentration was known: , and you used a specific volume of the solution, -. However, at the start of the reaction you must account for the fact that the total volume of each solution was 200 mL. ANSWER: †¢Calculate the initial molarity of the hydrogen peroxide in each of your solutions, once the solutions have been mixed. Remember: The H2O2 stock solution concentration was known: , and you used a specific volume of the solution, . However, at the start of the reaction you must account for the fact that the total volume of each solution was 200 mL. ANSWER: †¢Calculate the number of moles of sodium thiosulfate, Na2S2O3, that was initially present in each solution. Remember: The Na2S2O3 stock solution concentration was known: and you used a specific volume of the solution, . This information is used to determine the number of moles. ANSWER: †¢Balance the reaction that occurred in each of the solutions. Refer to Eq. 1, 3, and 4 in the laboratory instructions for the components that are involved. ANSWER: †¢Calculate the number of moles of hydrogen peroxide that has reacted: Note: You will need to use stoichiometry to determine this. ANSWER: †¢Calculate the change in concentration of hydrogen peroxide in each case, i.e., moles of H2O2 reacted per litre of solution. Hint: Recall the total volume, and you have calculated the number of moles that reacted, previously. ANSWER: †¢Calculate the rate of the reaction, which is simply the change in concentration of H2O2 (calculated above) divided by the time it took for the reaction to complete. i.e., the numbers of moles per litre of peroxide consumed divided by the number of seconds required to react completely. ANSWER: †¢Complete the table below – you can manually do the calculations to fill all of the cells, or it is possible to use a spreadsheet program to calculate the values. (RECOMMENDED) The process you have used above can be repeated to provide the values for each of the entries in the table. ANSWER: 3.Use the following steps to calculate the values of a and b as described in the lab procedure (under the heading: The rate law and our process for obtaining a, b, and k.) In the solutions A, B and C, the concentration of hydrogen peroxide used was the same. Therefore, these solutions are a suitable series for an examination of the dependence of the rate of reaction on the concentration of the iodide ion. Similarly, solutions C, D, and E have the same concentration of iodide ion. Therefore, those solutions can be used to examine the dependence of the rate of reaction on the concentration of hydrogen peroxide. Recalling Eq. 5 – Eq. 7 in the laboratory instructions, by plotting ln(rate) against ln[I-], using data from solutions A, B, and C, we can determine the value of a for this reaction. Similarly, by preparing a plot of ln(rate) against ln[H2O2] using the data from solutions C, D and E, we can evaluate b for this reaction. See the laboratory instructions near Eq. 5-7 for an explanation of how a and b can be determined from the slopes of the straight lines of best-fit that should be obtained using the experimental data-points. †¢Graph 1: Plot ln(rate) against ln[I-] using the data from the table for solutions A, B, and C. Add the best-fit straight line through your experimental points and determine the slope of this line. This is best accomplished by using a spreadsheet program to generate the graphs, and adding a â€Å"regression line† or â€Å"trendline† with the equation for the line displayed. The value of the slope from this line will be the value of b (as shown in Equation 6 of the lab manual). Remember: the final value of b should be integer or half-integer. ANSWER: †¢Graph 2: Plot ln(rate) against ln[H2O2] using the data from the table for solutions C, D, and E. Add the best-fit straight line through your experimental points and determine the slope of this line. This is best accomplished by using a spreadsheet program to generate the graphs, and adding a â€Å"regression line† or â€Å"trendline† with the equation for the line displayed. The value of the slope of this line is the value of a (as shown in Equation 7 of the lab manual). Remember: the final value of a should be integer or half-integer. ANSWER: 4.Using Equation 2 of the lab manual, calculate the values of k (at room temperature) for each reaction trial you performed, using your values of a, b, and the rate and concentration information in the table. You should end up with 5 values of k, for the five trials that you performed at room temperature. ANSWER: Calculate the average value of k. Use this value of k, and the values of a and b to write out the general rate law for the reaction, (see Eq. 2). ANSWER: 5.Using the rate of reaction for solution A at room temperature, and the rate of the reaction at elevated temperature, use Eq. 10 from the lab procedure to calculate the activation energy, Ea. (Note: pay attention to the units of the gas constant, R)