• 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...


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.


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.


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)

    compared to the other molarities and therefore had a reduced probability of steric hindrance - which is another cause for the increase in the rate of reaction. Also my graphs show the gradient is increasing which proves my main hypothesis of rate of reaction increasing as concentration of the solution.

  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.

    With my preliminary testing in mind, I have decided to use 50 ml of liquid overall, and 1g of marble chips. Method EQUIPMENT LIST * Clamp * Clamp-stand * Stopper * Timer * Distilled Water * Hydrochloric Acid * Marble Chips * Conical Flask * Gas Syringe * Petri Dish

  2. Rates of Reaction- Hydrolysis of Urea by Urease

    Additionally, the graph provides a clear visual representation of this data, and as a result the decline in reaction time is displayed suitably and easily interpreted. This is a definite indication and demonstration of the relationship between temperature and the time taken for an enzyme reaction to occur.

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

    A beaker was taken and using a pipette, 0.1ml of starch was placed into the beaker. The beaker must be wrapped in paper to keep light out so that the temperature is kept constant. Under the beaker was placed a piece of paper with a cross drawn on it with a marker pen.

  2. Investigating the rate of a reaction

    Also to control the temperature I will be completing all experiments at room temperature, to ensure that the tests are accurate. Below shows the table where I will be recording my results from the experiments. After collecting the results I will plot them of different types of graphs to analyse my data graphically.

  1. Rates of Reaction

    Temperature For a reaction to take place, the particles of the reactants have to collide with each other (collision theory). The particles of the reactants will only collide with one another if there is enough activation energy. By increasing the temperature we are also increasing the activation energy.

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

    In each case, the concentration of the enzyme catalase was kept constant, as were all other conditions such as temperature. As expected, the graphs start off with differing gradients, depending on the initial concentration of hydrogen peroxide. Table 3 shows the initial rates of the experiments in Figure 8.

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