Iodine Reaction Lab

A. i) The rate of a reaction is the change of a substance’s concentration per units of time. The reaction rate of an experiment is dependent on many things including concentration, presence of a catalyst, and, most importantly, temperature. Temperature and reaction rate are directly correlated, which means that as one increases, so does the other. It is a general approximation that the rate of a reaction will increase by a factor of two for every 10°C jump in temperature. Increased temperature is directly related to an increase in molecular motion, which means that there will be more effective collisions. According to the collision theory, the more effective collisions that occur, and the faster a reaction occurs. This is because an effective …show more content…
i) In the experiment, iodine was a zero order reactant. If a reactant is zero order then there is no relationship between concentration and rate. A low concentration of iodine was used due to its high levels of toxicity. While iodine is necessary for humans in small doses, large amounts of iodine are harmful when taken orally as well as when in contact with the skin. About 1 mg of pure iodine is the maximum amount of iodine that is beneficial towards humans. High concentrations of iodine can cause tissue damage and even result in chemical burns. Taken orally, iodine can be deadly. The reaction called for much more than 1 mg of iodine, so using a low concentration helped ensure safety. Since I2’s concentration will not affect the rate of the reaction, the risk of using a high concentration of I2 is not necessary. Using .005M of iodine will produce the same results that using 50M of iodine would. When concentration is plotted vs. time and a straight line appears, it means a reaction is zero order; if the rate were affected by concentration, there would be a curve. The absence of a curve shows that the reaction occurs at a steady rate. A zero order reaction such as this typically occurs when other reactants have much higher concentrations, which is the case in this reaction. Acetone has a concentration of 4M, while HCl has a concentration of 1M. Additionally, iodine had such a low concentration because it is the rate determining reactant. Since the other two reactants were …show more content…
This resulted in a margin of error between trial #1’s experimentally obtained rate and trial #1’s predicted rate being 8.13%. The predicted rate was determined by using the corrected rate law, as well as the corrected average k constant, which is 3.76x10-5 1/sM. The formula used to find the percent error was . The overall percent error between the average predicted rate (calculated with the corrected k constants) and the experimentally obtained average rate, not just trial one’s results, was 2.4%. The percent error could have results from many sources of error. The times were all hand timed and sometimes it was difficult to tell when the iodine had completely neutralized so the times may be slightly off. Additionally, when collecting the times, it was difficult to get the smaller digits, such as milliseconds because of the speed of the stopwatch, which is another reason the times may be off. The amounts of reactants used may have varied slightly from the directions due to human error, which may have resulted in inaccurate results. These inaccuracies most likely resulted in the incorrect order of iodine. Experimentally, iodine was found to have a ½ order; however, its correct order is 0. This may have been do to incorrect times resulting in incorrect