Experiment 4

Experiment 4 - EXPERIMENT 4 Kinetics of the Iodine Cock...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
EXPERIMENT 4 Kinetics of the Iodine Cock reaction 31 E XPERIMENT 4 Kinetics of the Iodine Clock reaction 4.1. Purpose In experiment 4, the rate law of the Iodine Clock reaction is established, and a value for the activation energy of the reaction is derived. 4.2. Background One of the goals in a chemical kinetics study is to derive an equation that can be used to predict the relationship between the rate or the speed of a reaction and the concentration of the reactants. Such an experimentally determined relation is called a rate law , or rate equation . If one considers a hypothetical reaction such as the one displayed in equation 4.1, a·A + b·B + c·C + … products (4.1) then the rate of the reaction v r is often of the form as shown in equation 4.2: v r = k ·[A] m ·[B] n ·[C] p · ( 4 . 2 ) The characteristic proportionality constant k is called the rate constant of the reaction. The kinetic exponents m , n, p … are generally small, positive whole numbers, although in some cases they may be zero, or fractions of two integer numbers. Note that the kinetic exponents are not related to the stoichiometric coefficients. Usually, m a, n b, and so on. The kinetic exponents define the order of a reaction. The reaction of equation 4.1 then is of order m in A, of order n in B, and of order p in C, and the overall order of reaction is the sum of the kinetic exponents. A successful reaction is made up of three intertwined events: it depends on the reactants coming together, orientating and aligning themselves properly and having sufficient energy to complete the interaction to form product. In this lab we will we will explore what roles the concentration of the reactants and the temperature or energy have on the rate of a particular reaction.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
EXPERIMENT 4 Kinetics of the Iodine Cock reaction 32 4.1.1 The Iodine Clock The Iodine Clock reaction is a classical demonstration experiment to display chemical kinetics in action; it was discovered in 1886 by Landoldt. This reaction is also an example of a chemical clock ; a mixture of reacting chemical compounds in which the concentration of one component shows an abrupt change accompanied by a visible color effect. In self-indicating reactions of this type, in which nothing seems to happen for while and then a change suddenly becomes visible, the onset of the color change may be used to time the reaction. The iodine clock reaction exists in several variations. Common to all protocols is the oxidation of iodide anion to yield molecular iodine; the various reactions differ in the choice of the oxidizing agent. Persulfate, iodate, and chlorate may be employed, among other agents. To make an Iodine clock work, we need to include two components, detection and time delay , which we now shall discuss in detail 4.1.2 Detection in the Iodine Clock In this experiment, we will explore the hydrogen peroxide variation of the Iodine Clock reaction. This reaction starts from a solution of hydrogen peroxide with sulfuric acid which proceeds conveniently slow
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/29/2008 for the course CHEM 118 taught by Professor Jacobsen during the Spring '08 term at Tulane.

Page1 / 10

Experiment 4 - EXPERIMENT 4 Kinetics of the Iodine Cock...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online