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

The Iodide - Persulphate Reaction: Determining the Effect of Concentration on Reaction Rate

Extracts from this document...

Introduction

The Iodide - Persulphate Reaction: Determining the Effect of Concentration on Reaction Rate Name: April Yue Date: February 10, 2004 Student ID: 20131652 Section: 006 T.A. : Mary Diep April Yue (20131652) CHEM 123L Feb. 10, 2004 Experiment 3: The Iodide - Persulphate Reaction: The Effect of Concentration on Reaction Rate Introduction: In this experiment, we utilized the ability for the iodide ion to become oxidized by the persulphate ion. Our general reaction can be described as: (NH4)2S2O8 + 2KI --> I2 + (NH4)2SO4 + K2SO4 (1a) However, we know that in an aqueous solution, all of these compounds except iodine will dissociate into their ionic components. Thus we can rewrite the equation in a more convenient manner: S2O82- + 2I- --> I2 + 2SO42- (1b) It is important however to note that the NH4 and K ions are still in the solution, they are just unreactive. In order to measure the rate of the reaction, the conventional method would be to measure the species in question at certain times. However, this would be inconvenient, especially for a three hour laboratory period. Since the iodide ion can be oxidized by the persulphate ion, we can use sodium thiosulphate to be an indicator of the presence of iodine in the solution. For this experiment, we can simply calculate the rate of the reaction by timing the amount of iodine being produced in several runs. ...read more.

Middle

log [S2O8-2] m= rise = -2.678 - (-2.055) = -0.623 = 1 run -2.041 - (-1.439) -0.602 slope 2: -log ?t vs. log [I-] n= rise = -2.635 - (-2.055) = -0.58 = 1 run -1.74 - (-1.138) -0.602 3. Sample Calculations: Rate of Reaction for run #1: Rate = -?S2O8-2 / ?t = -9.09 x 10-4 M / 113.5 s = 8.01 x 10-6 M s-1 Rate constant (k) for run #1: k = Rate / ( [S2O8-2]m [I-]n ) k = 8.01 x 10-6 M s-1 / {(3.64 x 10-2 M)1(7.27 x 10-2 M)1} k = 3.03 x 10-3 s-1 Ionic Strength (�) for run #1: � = 0.5 ? CiZi2 � = 0.5{([NH4]x(+1)2) + ([S2O8]x(-2)2) + ([K]x(+1)2) + ([I]x(-1)2) + ([Na]x(+1)2) + ([S2O3]x(-2)2)} � = 0.187 mol L-1 Table 2 - Calculations Summary Table Run # [S2O8-2] (M) [I-] (M) [S2O3-2] (M) -?S2O8-2 (M) ?t (s) Rate (M s-1) Rate Constant, k (s-1) Ionic Strength (M) 1 3.64 x 10-2 7.27 x 10-2 1.82 x 10-3 -9.09 x 10-4 114 -8.01 x 10-6 3.03 x 10-3 0.187 2 1.82 x 10-2 7.27 x 10-2 1.82 x 10-3 -9.09 x 10-4 218 -4.16 x 10-6 3.15 x 10-3 0.187 3 9.09 x 10-3 7.27 x 10-2 1.82 x 10-3 -9.09 x 10-4 476 -1.91 x 10-6 2.89 x 10-3 0.187 4 3.64 x 10-2 3.64 x 10-2 1.82 x 10-3 -9.09 x 10-4 228 -3.98 x 10-6 3.01 x 10-3 0.187 ...read more.

Conclusion

Since the ionic strength has also decreased, it has some effect on the resulting rate constant and therefore skews the results a bit. The rest of the results seem to agree with the logical way the experiment should have occurred. For example, the runs with the longer elapsed times had the slower reaction rates and vice versa with the runs with the shorter elapsed times. This makes sense due to the linear relationship between reaction rate and time. Some sources of error in this experiment may have been a mistake in mixing certain reactants, or inaccuracy with measuring volume of the solutions. It was more likely that there was inaccurate measuring of the solutions because it was quite difficult to always use the Mohr and transfer pipettes precisely. Conclusions: The purpose of this experiment was to determine how concentration of a certain reactant in a reaction can affect the rate of the entire reaction. The experiment was overall a success because we could see that when we varied the concentrations of certain compounds, the reaction rate was affected accordingly. Overall we know that the rate of the reaction is linearly proportional to the concentration of your reactant. However, if your reaction can exist in equilibrium and you increase the concentration of a product, the reaction will favour in the left direction, and if you are measuring rate of product formation, this will result in a decrease in reaction rate. Reference(s): Chemistry Department, First Year Chemistry: Chem 123L Laboratory Manual. University of Waterloo: 2004 ...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. Peer reviewed

    Rates of Reaction

    5 star(s)

    the user cannot recover and may record the information drawing out false conclusions leading to a wrong investigation. For this particular reason tests were repeated to draw out anomalous results. These results would be much different compared to the others.

  2. Rates of Reaction - The Iodine Clock

    The best range (and therefore chemical mixture) is one that shows quite a large variation in time for a small change in the concentration of limiting reagent (independent variable), the times for the reaction to reach the end-point should lie between approximately thirty seconds (for the fastest)

  1. Investigation into the Effect Concentration has on Rate of Reaction.

    * Connect the end of the connecting tube to the gas syringe * Measure 1g of medium-sized marble chips. * Add chips to the flask. * Put the stopper in the flask and start the stop-clock * Record the amount of gas in the syringe at 10 second intervals for 3 minutes.

  2. An Investigation into the effect of concetration on the Rate of Reaction Between Potassium ...

    A stop clock was taken and as the two solutions were poured in to the beaker the stop clock was started. A person observed above the beaker until the two solutions had reacted and the cross had disappeared and then the stop clock was stopped.

  1. Find out how the rate of hydrolysis of an organic halogen compound depends on ...

    The cross is no longer visible when a certain amount of sulphur has formed. The reaction time to reach this point can be measured using different starting concentrations of sodium thiosulphate solution. The volume of each solution and the concentration of the hydrochloric acid must be kept constant in each experiment.

  2. Rates of Reaction- Hydrolysis of Urea by Urease

    Sodium Hydroxide was also extremely corrosive and it was necessary to prevent contact with the skin and eyes. Phenolphthalein caused skin irritation and was harmful to inhale. Therefore the experiments were conducted in a laboratory, with direct access to sinks and running water.

  1. Rate of Reaction

    So I will be using this method. Concentration: The lower the concentration the slower the rate of reaction. This is because the higher the concentration the more hydrochloric acid molecules are present meaning the chances of collision are higher. Method In the reactions I used 3cm strips of magnesium and 50ml of diluted hydrochloric acid.

  2. The Iodine Clock

    E.g. 572+608 = 1180/2 = 590 s. Conclusion: The graph has a positive line to it, it shows that when the concentration of the thiosulphate increases so does the amount of time that it takes for the solution to react, this is what I predicted would happen.

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