Exp 5 Altered Procedure.docx

Modified Procedure for Experiment 5: Rate and Order of a Chemical Reaction

1. Before the start of the experiment, you will have to calibrate the gas pressure sensor and the temperature probe (if used). Set up the experiment as shown below. You will set up this experiment four different times at four different temperatures, 10oC, 25oC (room temperature), 35oC and 50oC. For 10oC, you must use an ice water bath to lower the temperature. For 25oC, you do not need to immerse the Erlenmeyer flask setup into any water because it is room temperature. For both 35oC and 50oC, you have to use a hot water bath so the set-up has to be immersed into water that has been heated on a hot plate. Check the temperature with a thermometer or you can use a temperature probe. If you use a temperature probe, you must calibrate it first.

Figure 1 2. Weigh a known quantity 0.01g of calcium carbonate and place it in the flask.

Modified Procedure for Experiment 5: Rate and Order of a Chemical Reaction 3. Place the flask in a water bath and connect a Gas Pressure sensor to Channel 1 of the Vernier Computer interface. Connect the interface to the computer using the proper cable. 4. Through a second hole in the stopper, add 1.5 mL of 1.0 – 2.0 M hydrochloric acid using the 5mL syringe. 5. Start the Logger Pro program on your computer. 6. Prepare to run the reaction and collect pressure data. 7. Gently shake the flask and click to begin the data collection. Gather data till the pressure does not change. 8. Repeat the experiment at least three more times at the different temperatures. 9. The data should contain pressure-time graphs for four different temperatures at which the reaction was performed. Make sure to save all 4 runs because your data will be processed using the Logger Pro application. 10. Record the initial pressure and the final pressure for each run at each temperatures. 11. Include in this section all graphs of raw data, and construct a table to display raw data and experimental uncertainties.

II. Transforming Data using Logger Pro 1. You will create a new calculated column and make sure to choose the appropriate run that you will use from the drop down box. Name the column Run 1 10oC and the short name 10oC. 2. You will have to add an equation to calculate the data. Press functions and choose ln. ln () will show up. You will add a parenthesis so now you have ln((). In between the closed parenthesis you will type the final pressure for run 1. Subtract under parameters, choose pressure. Example: ln((650Pressure). You will then divide by the final pressure so ln((650-Pressure)/650). Press done. All of the values for Run 1 will be calculated and you can then plot your graph. 3. The graph that you want to plot is ln[PfCO2-PiCO2)/ PfCO2] vs. time. Do a

Modified Procedure for Experiment 5: Rate and Order of a Chemical Reaction linear regression of the graph and get the slope of this line. It will give you –k. Slope=-k. Right click, the analysis box and add uncertainty to the data. Do a print screen and copy graph to a WORD document names Run 1 10oC. 4. You will repeat the transformation of data for all temperatures. 5. Once you have k for all temperatures, you will plot the ln k vs. Temperatures. The slope will give you the ability to solve for Ea. Slope=-Eq/R where R is a constant for gas pressure. You will calculate the activation energy or Ea for the experiment. (Do this calculation before you leave lab. It must be signed off by either Dr. Stubbs or Dr. Morris).

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Tables and Graphs You will have a data table with all raw data included. Final pressure, initial pressure, temperature, amount of CaCO3, amount of HCl, slope and y-intercept along with uncertainties. The second data table will include the k’s at each temperature, the temperatures, ln k. You should have 4 graphs at each temperature where ln[PfCO2-PiCO2)/ PfCO2] is plotted on the y-axis and time is plotted on the x-axis. Each graph will have a linear fit with slope and y-intercept data plus the uncertainties. You will have a final graph with ln k on the y-axis and temperature on the x-axis. You will do a linear fit to this graph and the slope and y-intercept. Use this slope to calculate the activation energy. This can be done in Excel. Make sure that you have 2 data tables and 5 graphs included in your lab report. Make sure to label each graph and table with the appropriate caption.

IV. Calculations Show calculations for ln[PfCO2-PiCO2)/ PfCO2], ln k, and activation energy in your lab reports.