• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Iodine Clock Reaction

Extracts from this document...


Annesha Mohamed Dec. 7th/2004 IODINE CLOCK REACTION The rate law states that r, will always be proportional to the product of the initial concentrations of reactants, where these concentrations are raised to come exponential values. The order of reaction is the exponent value that describes the initial concentration dependence of a particular reactant. If the order of reaction is 0, then doubling the initial concentration of a reactant has no effect on rate; if order of reaction is 1, then doubling initial concentration doubles rate; and if order of reaction is 2, then doubling initial concentration quadruples rate of reaction. "Iodine Clock" refers to a group of reactions which involve the mixing of two colorless solutions to produce a solution which remains colorless for a precise amount of time, then suddenly changes to a deep purple-blue color of starch-iodine complex. The time is controlled by the temperature and/or the concentrations of the reactants. The rate of this reaction depends on the temperature, and on the concentrations of iodate ions. This reaction alone does not give very impressive delays and color changes. The time delay until the appearance of the blue color is inversely related to the rate of the reaction --the faster the reaction, the shorter the delay but the color development is directly related to the rate--a sharp change in the color requires a moderately fast reaction. ...read more.


The time taken for the change colour to occur was measured from the first drop of Solution A in Solution B to the first appearance of colour in new solution. The pipette was not allowed to touch Solution B so as to eliminate the need for rinsing it after each reaction. o Additionally, the contents of Well 2 of spot plate A were transferred to Well 2 of spot plate B and the time elapsed before colour change was evident was recorded. This process was continued until no visible traces of colour could be detected when different concentrations of Solution A were added to constant concentrations of Solution B. OBSERVATIONS/ANALYSIS: The reactions are: 1. IO3- + 3HSO3- --> 3SO4 2- + 3H+ (slow) 2. 5I- + IO3- + 6H+ --> 3I2 + 3H2O (slow) When all the Bisulfite is used up: 3. I2 + HSO3- + H2O --> 2I- + SO4 2- + 3H+ (fast) 4. I2 + I- --> I3- (fast) 5. I3- + starch --> I3- starch complex (blue black) [KIO3] 0.0522 mol/L [NaHSO3 ] 0.0538 mol/L Time(s) 1 ?t(s) Final concentration of Solution (mol/L) V2 equals 20 drops 0 0 0 0 0 10 drops 10 drops 5.490 0.1821 C1V1 = C2V2 0.0522 x 10 = C2 20 C2 = 0.02610 ...read more.


(i.e. if the concentration of iodate ions is doubled, the rate of reaction will also be doubled. Doing such investigations can be tedious, but the realization that the results are actually beneficial and reliable makes it worthwhile. In this reaction though, errors occur, but not so much that the results were not acceptable. Firstly, the concentration of reactants may have been inaccurate. It is important to add specific volumes of water to the wells for Solution A, so as to dilute the concentration, and yield a volume of 10 drops of solution in the well. The sizes of the water drops were not all equal, even though pipettes were cautiously picked so that all three looked about the same size. When transferring Solution A from spot plate A to B, the pipette might have accidentally touched Solution B. This would have thrown off the accuracy of the concentration of Solution A. As always, measuring short time intervals prove difficult and times may have been inexact. Nonetheless, the goal of the experiment was met. A dramatic colour change enabled us to investigate the effect of concentration on rate of reaction and figure out that when concentration of reactants and rate of reaction increase proportionally, the order of reaction is 1. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Patterns of Behaviour section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Patterns of Behaviour essays

  1. Rates of Reaction - The Iodine Clock

    To determine the order of a reaction by graphical means: By performing an experiment repeatedly, varying the concentrations of a particular variable whilst keeping the other volumes and conditions constant, it is possible to determine the order of reaction with respect to that chemical.

  2. The Iodine Clock Investigation

    time will have a half-life that isn't constant, but one that increases dramatically as the reaction proceeds. This graph is visibly much 'deeper' than a graph showing a first order reaction. N.B. The graphs above only show the order of a reaction with respect to substance A, and do not necessarily show the overall order of the reaction.

  1. A-Level Investigation - Rates of Reaction – The Iodine Clock

    Trial experiments should be performed for each of the three variables to determine the volumes of non-limiting reagents (controlled variables) that will exhibit the best possible range of results when reacted together along with the limiting reagent. The best range (and therefore chemical mixture)

  2. Activity of Diastase On Starch

    At temperatures just above optima, there may be a situation where the enzyme is in a sort of equilibrium where it temporarily loses some of it's structure and then regains it to work again. At higher temperatures these bonds literally get shaken apart and the three -dimensional structure of the protein destabilises.

  1. Investigating the Factors Affecting the Rate of Reaction for the Iodine Clock

    However there are no catalysts that would affect the speed of this reaction. Plan My task is to carry out a number of experiments in order to see how one factor affects the rate of reaction for the iodine clock experiment.

  2. The Iodine Clock

    Potassium Iodide (cm3) Sodium Thiosulphate (cm3) Ammonium Persulphate (cm3) Water (cm3) Startch (cm3) Total Volume (cm3) Time (s) 5 3 5 11 1 25 334 10 3 5 6 1 25 145 5 6 5 8 1 25 451 5 3 10 6 1 25 133 These results show how

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work