Chemical Kinetics 2 Overview Getting Started Techniques Procedure FAQ Full Lab Manual Introduction & Goals Chemistry & Background Key Questions Prelab Problems Safety Procedure In Your Write-up Experiments Index ChemLab Home		FAQ Index Question 1 My activation energy doesn't agree with my lab partner's. What could be wrong? Question 2 Why do I have to plot my data during the experiment? I hate that! Question 3 How do I extrapolate my data to find t = using the Least Squares Applet on the website? Submissions Submit a question or an answer to the FAQ Questions & Answers Question 1 My activation energy doesn't agree with my lab partner's. What could be wrong? Look carefully at the units for your calculation of the activation energy. You are plotting ln k vs. 1/T, and the units of the slope will be units of temperature. To calculate the activation energy, you will multiply the slope times -R. So R should be in units of J/mol K, the temperatures and slope should be in units of K, giving an activation energy in J/mol units. Typical mistakes are to neglect to convert the temperature values to Kelvin units and to use the gas constant R in the incorrect units. Question 2 Why do I have to plot my data during the experiment? I hate that! There are lots of good reasons to plot your data as you measure them. Plotting gives you a much better feel for trends in the data that may not be obvious if you just record the numbers. Looking at a plot may point out an experimental problem, like a mis-measured reaction mixture or a drifting spectrometer, for example. It is better to find out about problems early in a run rather than after spending 20 minutes recording data that are not useable! Question 3 How do I extrapolate my data to find t = using the Least Squares Applet on the website? You need the x intercept of your plot, which is the time when A = 0. The slope and intercept from the Least Squares applet give you the equation of the line. If you use this equation and substitute 0 for y, you can solve for the x value, which will be the x-intercept. Submissions Submit to the FAQ If you have either a question or an answer to a question about this experiment, please email it to your lab instructor. You will receive a reply to your submission, and we may also add it to this FAQ page.
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