The Iodine Clock Reaction

Better Essays
The Iodine Clock Investigation

Introduction

This is an investigation into the rate of a reaction and the factors that contribute to how fast a reaction will take place. Through the recording and analysis of raw data, this investigation also allows us to apply generally accepted scientific rules and to test them against results gained from accurate experimental procedures.

Aim

The aim of this experiment is to investigate the rate at which iodine is formed when the concentration and temperature of the reactants are varied, and to attempt to find the order and activation energy.

The Chemistry

'THE IODINE CLOCK ' - This is the experiment that will be used to investigate reaction rates, and it is a reaction between acidified hydrogen peroxide and potassium iodide:

2H+(aq) + 2I¯ (aq) + H[-1] 2O2 (l) ÕI2 (aq) + 2H2O2 (aq)

Iodide ions are firstly oxidised by the hydrogen peroxide, as shown in the above equation. The iodine that is then produced reacts immediately reacts with thiosulphate ions as follows:

I2 (aq) + 2Na2S2O3 (aq) Õ 2NaI (aq) + Na2S406 (aq)

As soon as all of the thiosulphate ions have reacted with the iodine, the excess iodine molecules react with the 2% starch solution that is present in the reaction. This can be seen as an instant change in colour, from a colourless solution, to a deep purple coloured solution. This change in colour denotes the completion of the reaction. Factors affecting the rate of reactions:

All chemical reactions occur at a definite rate under particular conditions. In order to increase the rate at which reactions occur, the frequency at which reacting molecules collide must be increased.
This may be achieved in a number of ways:

1. By increasing the concentrations of reacting species.

2. By increasing the temperature.

3. By increasing the pressure (only really significant in reactions involving gases).

4. By the use of a suitable



Bibliography: 'Chemistry Students Book ' - Nuffield Advanced Science  'Chemistry In Context ' - Graham Hill And John Holman  'Basic Inorganic Chemistry ' - Cotton, Wilkinson, Gaus  'Inorganic And Physical Chemistry ' - A. Holderness  'Advanced Chemistry ' - P.R.S. Murray  'Chemistry In Focus ' - John Andrew And Paul Rispoli  'Chemistry ' - Ken Gadd And Steve Gurr

You May Also Find These Documents Helpful

  • Good Essays

    The Iodine Clock Reaction

    • 824 Words
    • 4 Pages

    Chemical Kinetics: The Iodine-Clock Reaction: S2O82−(aq) + 2 I−(aq) → I2(aq) + 2 SO42−(aq) To measure the rate of this reaction we must measure the rate of concentration change of one of the reactants or products. Here, it is convenient to carry out a clock reaction involving the product I2. To do this, you will include (to the reacting S2O82− and I−) i) a small (but accurately known) amount of sodium thiosulfate, Na2S2O3, and ii) some starch indicator. The added Na2S2O3 does not interfere with…

    • 824 Words
    • 4 Pages
    Good Essays
  • Powerful Essays

    Iodine Clock Reaction

    • 1655 Words
    • 7 Pages

    ON THE RATE OF REACTION Aim To study the effect that temperature and concentration of iodide ion solution have on the rate of iodide ion I⁻ oxidation by peroxodisulphate ion S₂O₈⁻, creating an iodine clock reaction. Introduction I decided to choose as the topic for my investigation the rate of reaction for its vital importance in the human body. Indeed I am really interested in Biology and especially physiology and I would like to study medicine. The rate at which different reactions happens in the…

    • 1655 Words
    • 7 Pages
    Powerful Essays
  • Powerful Essays

    Iodine Clock Reaction

    • 1364 Words
    • 6 Pages

    instructions. Clock reactions If you choose a project that explores the kinetics of a chemical reaction you will need a way of measuring the rate of the reaction. Clock reactions provide an interesting way of doing this for some systems. In a typical reaction the first part of a graph showing the concentration of product against time is approximately a straight line (see Figure 1). If you choose any value of concentration that lies on this straight line (say c1) the initial rate of reaction can be…

    • 1364 Words
    • 6 Pages
    Powerful Essays
  • Good Essays

    Iodine Clock Reaction

    • 5803 Words
    • 24 Pages

    Kinetics of the Harcourt-Essen Reaction Name: Manpreet Kaur Candidate Number: 7123 AS and A2 Aims: AS AIMS: 1. Investigate the effect of temperature on the rate of reaction. For this aim 3 sets of results will be obtained by timing how long it takes for the colour change to occur in different temperatures determined by the use of an electric water bath. With these results, the effect of temperature on the rate of reaction will be investigated. 2.…

    • 5803 Words
    • 24 Pages
    Good Essays
  • Powerful Essays

    Iodine-Clock Reaction

    • 2660 Words
    • 11 Pages

    CHEMICAL KINETICS: IODINE-CLOCK REACTION DATE SUBMITTED: 14 DECEMBER 2012 DATE PERFORMED: 7 DECEMBER 2012 ABSTRACT Chemical kinetics involving reaction rates and mechanisms is an essential part of our daily life in the modern world. It helps us understand whether particular reactions are favorable and how to save time or prolong time during each reaction. Experiment demonstrated the how concentration, temperature and presence of a catalyst can change the rate of a reaction. 5 runs of dilution…

    • 2660 Words
    • 11 Pages
    Powerful Essays
  • Good Essays

    CONCLUSION The experimentally obtained data collected for the reaction between IO3- and HSO3- at various temperatures is clearly supported by the Arrhenius equation. Referring to Graph 1.7, the line of best fits clearly passes through most of the data points displaying a linear relationship between temperature and the rate of the reaction. The R-squared of the graph which is a statistical measure of how close the data are to the fitted regression line is 0.9818. This number is extremely low which…

    • 1146 Words
    • 5 Pages
    Good Essays
  • Satisfactory Essays

    Iodine Clock

    • 278 Words
    • 2 Pages

    perform an experiment known as the "iodine-clock" reaction, in which hydrogen peroxide reacts with iodide to form iodine, and the iodine subsequently reacts with thiosulfate ion until the thiosulfate has been consumed. At that point, the reaction solutions turn blue in the presence of starch. The experiment helps students understand the fundamentals of chemical kinetics --- the speeds at which reactions take place. 1. Activation Energy * Chemical reactions are thermodynamically "favorable"…

    • 278 Words
    • 2 Pages
    Satisfactory Essays
  • Good Essays

    Introduction The purpose of this experiment is to determine the rate equation for the “Iodine Clock Reaction” experiment. The experiment will consider the equations 〖2I〗^-+S_2 O_8→2〖〖SO〗_4〗^(2-)+I_2 and I_2+2〖S_2 O_3〗^(2-)→2I^-+S_4 O_6 in order to determine the rate law of Rate=k[〖〖S_2 O_8〗^(2-)]〗^a 〖[I^-]〗^b by using the experimental data to calculate the values of exponents a and b as well as the rate constant k. Experimental Supplies Needed: 250 mL Erlenmeyer flask, 100 mL beaker, graduated…

    • 1015 Words
    • 5 Pages
    Good Essays
  • Powerful Essays

    EXPERIMENT 3-CHEMICAL KINETICS: THE IODINE-CLOCK REACTION J.CHAN1 and C.CABANLIG2 1NATIONAL INSTITUTE OF MOLECULAR BIOLOGY AND BIOTECHNOLOGY, COLLEGE OF SCIENCE 2NATIONAL INSTITUTE OF MOLECULAR BIOLOGY AND BIOTECHNOLOGY, COLLEGE OF SCIENCE UNIVERSITY OF THE PHILIPPINES, DILIMAN, QUEZON CITY 1101, PHILIPPINES DATE SUBMITTED: JANUARY 8, 2013 DATE PERFORMED: DECEMBER 5, 2012 ------------------------------------------------- ABSTRACT The kinetics of the reaction between persulfate (S2O82-) and…

    • 2764 Words
    • 12 Pages
    Powerful Essays
  • Powerful Essays

    EFFECT OF CONCENTRATION ON REACTION RATE The aim of this experiment is to find the effect of varying the concentration of iodide ions on the rate of reaction between hydrogen peroxide and an acidified solution of potassium iodide: H2O2(aq) + 2H+(aq) + 2I⁻ → 2H2O(l) + I2(aq) The course of this reaction can be followed by carrying it out in the presence of small quantities of starch and sodium thiosulfate solutions. As the iodine molecules are produced they immediately react with the thiosulfate…

    • 1498 Words
    • 6 Pages
    Powerful Essays