I'm very stuck with this lab and really need *delete me*!
The purpose of this experiment is to study the kinetics of the reaction between iodide, I-, and peroxydisulfate, S2O8 2-, ions. Effect of Concetration.
Given equation:
S2O82- (aq) + 2I- (aq) ---------------> I2 (aq) + 2SO42- (aq)
I2 (aq) + 2S2O32- (aq) ----------------> S4O62- (aq) + 2I- (aq
Rate = - d / dt [S2O82- ] = d[I2]/dt
= k [S2O82- ]x [I-]y
log (rate) = log k + x log [S2O82-] + y log [ I-]
Rate = d[I2]/dt = 1/2d[S2O32-] / dt
By plotting the data of time versus moles give us k value.
Volume of reagents:
(NH4)2S2O8 Starch KNO3 EDTA KI Na2S2O3 aliquots (5 in total)
RUN 1 10.0 ml 1.0 ml 27.0 ml 1 drop 10.0 ml 1.0 ml each
RUN 2 20.0 1.0 17.0 1 drop 10.0 1.0 ml each
RUN 3 10.0 1.0 17.0 1 drop 20.0 1.0 ml each
Concetration 0.25 M 0.25M 0.25M 0.20 M
Data for RUN 1:
aliquote # time (s) Moles of [S2O3]2-
1 151 s 0.0002 moles
2 300 s 0.0004
3 453 s 0.0006
4 625 s 0.0008
5 814 s 0.001
(Moles of S2O3 2- above were calculated by 0.20M Na2S2O3 (given concentration) x 0.001 L (each aliquot 1.0 ml) =0.0002 moles; and so on)
Then, using microsoft excel, i'm asked to plot this data, moles of S2O3 2- consumed vs. time (in seconds) for kinetic run.
RUN 1 formula for the straight line (that goes through 5 points from our data) is y = (1.2x10^-6)X + 1.7x10^-5. [y = mx + b]
RUN 2 y = (2.8x10^-6)X + 1.2x10^-5
RUN 3 y = (2.6x10^-6)X + 1.8x10^-5
Question 1: From the slope of the line and the stoichiometry of the reactions involved, calculate for each run the rate of reaction of (NH4)2S2O8 in moles/sec. Using these values and the average volume of the reaction mixture during the run (50.0 ml), determine for each run the rate of reaction of (NH4)2S2)8 in miles/liter/sec.
Question 2: Calculate the initial (time zero) amounts of [S2O8]2- and I- in the reaction mixture for each run and taking 50.0 ml as the total volume of the solution determine the concentration of [S2O8]2- and I-
Question 3: The rate equation has the form: rate = k [S2O8 2-]^x [I-]^y. Three sets of values for rate, [S2O8 2-] and [I-] have been determined. Hence by using simultaneous equations, k, x, and y can be evaluated. Determine the order of the reaction with respect to S2O8 2-, (x), the order with respect to I-, (y), and the specific rate constant, (k), then write the rate law equation for the reaction as determined by the experimental data.