Did the reaction actually stop when the blue-black color appeared? Explain briefly
EXPERIMENT 16 A Kinetic Study of an Iodine Clock Reaction OBJECTIVES: To measure experimental reaction rates under different conditions. To use the method of initial rates to determine the order of reaction. To determine the rate constant of a reaction at different temperatures. To determine the activation energy of a reaction using graphical techniques. rate law. To make deductions regarding a reaction mechanism, based on the INTRODUCTION: According to chemical kinetics, it is possible to write down a Rate Law' for any chemical equation: Rate k[A]m [B] This rate law can be used to calculate the rate at which that particular reaction will proceed when a given concentration' of [A] and [B] are present in the system. However, to do this we must know the value of (it is temperature dependent). k rate constant m order with respect to concentration of A. n order with respect to concentration of B. It is important to realize that the values of k, m and n cannot be determined by looking at the chemical equation. They must be deduced experimentally someone must actually run and time the reaction under varying conditions. In this lab, we will studythe Rate Law forthe following reaction between the persulfate ion,s2os and the iodide ion. General Rate Lane. Rate -k ]m [s20g2-1n This reaction is called a clock reaction b of the thiosulfatestarch indicator system we use to time the reaction. Every you run this reaction, your flask will contain an indicator system consisting of time 5.0 x 105 moles of thiosulfate' ions, S2032, and a little starch. When the two reactants, Ose are first mixed start the reaction, every molecule of I2 that is produced reacts immediately with any nt according to the following chemical equation. S2032-preset 21- S40 12 2 S203 This removes the first 2,5 x 10 s moles I2 (look at stoichiometry of reactions above) from the system but then the thiosulfate is gone. This point is marked by the almost instantaneous appearance of an intense blue-black Also called Rate Equation and Rate Law Expression square brackets around anything, [X], means moles per liter of Xor molarin of x. You pipet 100 ml of 0.0050 M Naasio, into each flask.