Chemical Kinetics: the Iodine Clock Reaction

CHEMICAL KINETICS: THE IODINE CLOCK REACTION

BERLINJOY DIANNE N. TARAMPI

INSTITUTE OF BIOLOGY, COLLEGE OF SCIENCE

UNIVERSITY OF THE PHILIPPINES, DILIMAN, QUEZON CITY 1101, PHILIPPINES

DATE SUBMITTED: 27 FEBRUARY 2015

DATE PERFORMED: 13 FEBRUARY 2015

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ABSTRACT

This study aims to test the concentrations of the reactants, the temperature of the system, and the presence of a catalyst as a function of the rate of the reaction. It makes use of chemical kinetics and its various rate laws to compute for the rate constant and orders of the reaction with respect to the reactants of the rate determining step defined by the expression r = k[S2O82-][I-]. In this experiment, persulfate and iodide ions were made to react to form iodine. The first iodine compounds to be formed were consumed by thiosulfate, S2O32-, which was converted to tetrathionate, S4O62-, in the process. Once all thiosulfate was converted, latter iodine compounds produced would interact with starch resulting to an abrupt change in color, marking the end of the reaction time. Using initial rates method, the reaction was found to be a second-order reaction. Concentration was directly proportional to the rate; an increase in temperature sped up the reaction, also the addition of CuSO4, a catalyst. Obtained Arrhenius constant and activation energy, Ea, were 2.39 ×1010 and 53.4 KJ respectively.

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INTRODUCTION

Chemical Kinetics is the study of the rate at how fast or how slow a reaction proceeds under a given set of conditions. Factors that affect a reaction’s rate are the molar concentrations of its reactants, the temperature of the system, and the addition of a catalyst, which usually aids in speeding up a reaction without affecting the products of the reaction.

The rate of the reaction, defined by this equation (1)

rate = -∆[A]a∆t = ∆[B]a∆t (1)

given: aA ↔ bB...