I apologize in advance, as there is an enormous amount of information presented for this experiment.
The experiment deals with kinetics, and evaluating the rate law for iodate from graphical relationships generated from the changing concentration of iodate and time. In doing so, the objective is to find out if the reaction rate with respect to [IO
3] does or does not depend on the concentration of [IO
3]. If the reaction rate is dependent on the concentration of [IO
3] we want to determine if the dependence is linear or exponential, using the reaction plots, zero, first, and second order.
In studying one reactant at a time, and then plotting the experimental data in three different ways, ie. [IO
3-], ln[IO
3-], 1/[IO
3-], the student will determine if the reaction is zero, first, or second order with respect to that reactant. Whichever plot renders a linear relationship corresponds to the correct rate law, which is presented in the table below,
Table 1: Summary of the kinetics for reactions that are zero, first, and second order in iodate concentration
Plot needed for best-fit line (y = mx + b)
0 ; 1st ; 2nd
[IO
3-] vs. T ; ln[IO
3-] vs. T ; 1/[IO
3-] vs. T
Relationship of the rate constant, k, to the slope
0 ; 1st ; 2nd
slope = -k ; slope = -k ; slope = k
Rate law
0 ; 1st ; 2nd
Rate = k ; Rate = k[IO
3-] ; Rate = k[IO
3-]2
A 0 order reaction should show no dependence on concentration.
http://i49.tinypic.com/2czyph2.jpgA 1st order reaction should show a linear dependence on concentration.
http://i48.tinypic.com/oje8v8.jpgA 2nd order reaction should show an exponential dependence on concentration, as evidenced by each individual rate law.
http://i47.tinypic.com/dnjb04.jpgThis procedure makes use of the following tables,
Table 2: Kinetics data for determining the reaction order of iodate
Run – [IO
3] initial, M – [IO
3] final, M – Run Time, s – Plot Time, s
0 ; N/A ; 0.00800 M ; T0 ; T0
1 ; 0.00800 M ; 0.00700 M ; T
1 ; T
0 + T
1 2 ; 0.00700 M ; 0.00600 M ; T
2 ; T
0 + T
1 + T
23 ; 0.00600 M ; 0.00500 M ; T
3 ; T
0 + T
1 + T
2 + T
3 4 ; 0.00500 M ; 0.00400 M ; T
4 ; T
0 + T
1 + T
2 + T
3 + T
4 5 ; 0.00400 M ; 0.00300 M ; T
5 ; T
0 + T
1 + T
2 + T
3 + T
4 + T
5 6 ; 0.00300 M ; 0.00200 M ; T
6 ; T
0 + T
1 + T
2 + T
3 + T
4 + T
5 + T
6Table 3: Volumes of Solution A, water, and Solution B to add together
*Solution A, mL: 0.0200 M KIO
3 and 0.0200 M K
2SO
4**Solution B, mL: 0.0100 M Na
2SO
3, 0.0390 M H
2SO
4, and 0.2% Starch
Run ; Solution A, mL* ; mL H
2O ; Solution B, mL**
1 ; 40 ; 35 ; 25
2 ; 35 ; 40 ; 25
3 ; 30 ; 45 ; 25
4 ; 25 ; 50 ; 25
5 ; 20 ; 55 ; 25
6 ; 15 ; 60 ; 25
Procedure: The student will take a mixture of solution A and water in one beaker and add solution B into it. The student will then record the time it took, from adding solution B into solution A to the point that the mixture turns blue. The data will be plotted onto three separate graphs to determine the relationship,
Graph 1: [IO
3], M vs. Time, s
Graph 2: ln[IO
3] vs. Time, s
Graph 3: 1/[IO
3], 1/M vs. Time, s
Questions:
-In Table 2 above towards the right end of the table, there is ‘run time’ and ‘plot time.’ Run time, I’m assuming is the recorded time of each run, that it takes for the mixture to turn blue, and plot time, is simply adding the run times together, ie. for Run 1, since Run 0 has a run/plot time of 0 seconds, the time it takes for Run 1 is added, and the process is repeated for each subsequent run. Is this assessment correct? -How will I determine the order, will it be the graph that presents the linear relationship? This is my hypothesis, based on the presented data in the tables, is that this experiment will be a second order reaction, since the lower the concentration of the final iodate’s concentration, the larger its plot time on the x-axis, when the solution turns blue.
-What are the three main factors (that we have control over) affecting the rate of a reaction? Which factor is involved in the experiment? 1. Concentration, which is the factor used in the experiment, since the student mixed varying concentrations of iodate.
2. Temperature
3. Presence of a Catalyst
-Given the different orders of the reactions, what happens to the rate of a reaction, when the concentration of the reagent is doubled? The reaction rate will increase, since a direct relationship exists between concentration and reaction rate, that is, when the concentration of a reactant is doubled, the reaction rate also doubles. Using the collision theory, if we double the concentration of A, there are twice as many molecules of A in the same volume, so the molecules of B in that volume now collide with twice as many A molecules per second than before. Given that the reaction rate depends on the number of effective collisions per second, the rate doubles.
But the question for me is, how does this affect the different orders of the reactions?
-In a zero order reaction?
-In a first order reaction?
-In a second order reaction?
Is it just less time required for the rate reaction on the x-axis? 
ChemBuddy | 
Chem Reddit | 
Topic: Kinetics: Measuring Reaction Rates (Read 2801 times)