Some tips to help with your lab.
graphs of ln(Abs) vs. time SHOULD give straight line graphs. SHOULD. Try eliminating some of the data, like at the beginning or at the end where it started to level off. If that doesn't work, report what you collected knowing it SHOULD have been first order.
when looking at the rate constant under different temperatures, use the following resources (along with your book) to aid in your lab write-up
http://bouman.chem.georgetown.edu/S02/lect4/lect4.htm
http://chemistry.tutorvista.com/inorganic-chemistry/arrhenius-equation.html
http://chemwiki.ucdavis.edu/Physical_Chemistry/Kinetics/Reaction_Rates/Temperature_Dependence_of_Reaction_Rates/Arrhenius_Equation/Arrhenius_Plot
