Iodine Clocks are reactions which involve mixing colorless solutions to produce a sudden color change after an initial induction period (http://web.mst.edu/~gbert/IClock/discussion.htm). The color change occurs because of the formation of a starch-iodine complex(see appendix a). An iodine molecule slips into an amylose coil, part of starch (http://antoine.frostburg.edu/chem/senese/101/redox/faq/starch-as-redox-indicator.shtml).
The time delay is inversely related to the rate of the reaction(http://web.mst.edu/~gbert/IClock/discussion.htm).
This means that a faster reaction gives a shorter delay and a slower reaction lengthens the delay. Therefore, the length of the induction period can be used to calculate the rate of a chemical reaction.…show more content… Chemical kinetics is the study of chemical reactions regarding reaction rates, effect of various variables, re-arrangement of atoms and other aspects of chemistry (http://www.science.uwaterloo.ca/~cchieh/cact/c123/chmkntcs.html). The rate of a reaction can be measured by the rate at which a reactant is used up, or the rate at which a product is formed(http://www.bbc.co.uk/schools/gcsebitesize/science/add_edexcel/chemical_reactions/ratesrev1.shtml). Reaction rate is affected by temperature, which works with the arrhenius model, and catalysts, which act as physical scaffolds for the reaction to work on. The Law of Mass Action also states in its first part that the velocity of a reaction depends on the molecular concentrations of the reactants (http://www.cebm.net/the-laws-of-life-guldberg-and-waages-law-of-mass-action/). This is related to the collision theory. The collision theory, proposed by Max Trautz and William Lewis, is strongly interconnected with chemical kinetics (http://chemwiki.ucdavis.edu/Core/Physical_Chemistry/Kinetics/Modeling_Reaction_Kinetics/Collision_Theory/Collision_Theory_I ). It explains that for a reaction to occur, particles must collide. However, not every collision means that a product is formed. The particles must be in the right orientation with the right activation energy. Increasing the concentration of a reactant means that more particles are available for more collisions to occur. For…show more content… In the differential rate law, k may be alone (A0 = one) or [A] may be squared. These exponents are known as the order of the reaction. Zero-order in the reactant means that there is no effect on the initial rate of reaction, first order means that the rate of reaction doubles as the reactant doubles and second order means that when the reactant is doubled, the rate quadruples (http://chemwiki.ucdavis.edu/Core/Physical_Chemistry/Kinetics/Rate_Laws/The_Rate_Law ). Although the index may be higher, orders zero to two are the most common. [A] and [B] are used separately to calculate m and n. The overall order of the reaction can be defined as the sum of the powers, i.e., m+n (http://www.cosbkup.gatech.edu/group/chem780/CHAPT2.pdf). The variable k should ideally be the same in the graphs of both [A] and [B]. In a linear graph, the gradient (represented here by k) is constant. This is why k is a constant. As the differential rate law changes, so does the integrated rate law for each order. The x and y axes and slope of the graph then change as well (see appendix b). Thus, by trying the different plots and selecting the one which gives a straight line, the order of the reaction with respect to [A] or [B] can be obtained
