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Chemical Kinetics

Question
CBSEENCH12006288

The experimental data for decomposition of N2O5 [2N2Os → 4NO2 + O2] in gas phase at 318 k are given below:

(a) Plot [N2O5] again t.
(b) Find the half life period for the reaction.
(c) Draw a graph between log [N2O5] and t.
(d) What is rate law?
(e) Calculate the rate constant.
(f) Calculate the half life period from K and compare it with (ii). 

Solution
(a) Plot of [N2O5] vs. time.


(b) Time taken for the concentration of N2O5 to change from 1.63 x 10–2 mol L–1 to half the value.
t0.5 = 1420 s [from the graph] (c) Plot of log (N2O5) vs. time.

t

log10[N2O5]

0

400

800

1200

1600

2000

2400

2800

3200

3600

- 1.7918

- 1.8665

- 1.9431

- 2.0315

- 2.1079

- 2.1938

- 2.2757

- 2.3752

- 2.4559

- 2.5376

 

(c)


d) The given reaction is of the first order as the plot log[N2O5] v/s time, is a straight line.
Therefore the rate of reaction is

Rate = k[N2O5]

e) Form the plot, log [N2O5] v/s T, we obtained
slope= 

-2.46-(-1.79)3200-0= -0.673200Again, slope of line plot log [N2O5] v/s time is given by -K/2.303therefore, we obtained -k2.303 =-0.673200 k=4.82 x 10-4 s-1



f) Half-life is given by

 t12 = .693K    =0.6934.82 x 10-4   = 1.438 x 103  =1438s

This value, 1438 second is very closed to the value that was obtained form the graph.