Question

1. The following data were collected in a kinetics experiment for the disproportionation of A₂ in a buffered solution: 3 A₂ -> products

The "generic" rate law for the reaction is rate = k[A₂]^p

[A2]0	Time for color change	Rate (min-1)
0.10	7.50 minutes
0.20	2.00 minutes
0.30	1.30 minutes
0.40	0.90 minutes
0.50	0.50 minutes

Plot the data according to the method described in this experiment to determine p, the order of the reaction with respect to A₂. (Hint: The reaction order is not a whole number. Round the order to 2 significant figures.) ****I think the initial concentration of A₂ must be calculated from the data given?? I am not sure how to proceed. This is all the information I have. *****

5. How is the order of the reaction with respect to H₂O₂ determined in the experiment

a. chemically?

b. graphically?

6. Explain how the rate constant, k^', is determined for the rate law in the experiment.

7. Explain how the activation energy, E_a, is determined for the reaction in the experiment.

Answer 1

A2O	Time for colour change	Rate (min-1)
0.10	7.50 mints	1.33
0.20	2.00	2.50
0.30	1.30	2.56
0.40	0.90	2.78
0.50	0.50	4.00

This is second order reaction in the presence of Iodine catalyst

so we have to calculate rate equation for the above compounds in table

1/[A]=Kt+1/[A₀]..........................(1)

where

[A]=A₀/2....................................(2)

Therefore

substitute eq'2 in eq'1

1/[A₀]=K*t

give known terms in above table

[A₂0]=0.10

t=7.50

Therefore

K=1.33min^-1 similarly calculate remaining values.

following data we can draw a plot between concentration vs time

We draw the graph between lnK (y-axis) vs 1/T (x-axis)

In order to calculate the activation energy we need an equation that relates the rate constant of a reaction with the temperature (energy) of the system. This equation is called the Arrhenius Equation:

K=Ze^^-E_a/RT

Where Z (or A in modern times) is a constant related to the geometry needed, k is the rate constant, R is the gas constant (8.314 J/mol-K), T is the temperature in Kelvin. If we rearrange and take the natural log of this equation, we can then put it into a "straight-line".So now we can use it to calculate the Activation Energy by graphing lnk versus 1/T.When the lnk (rate constant) is plotted versus the inverse of the temperature (kelvin), the slope is a straight line. The value of the slope (m) is equal to -Ea/R where R is a constant equal to 8.314 J/mol-K.