Chemistry Class 12 NCERT Solutions: Chapter 4 ChemicalKinetic Part 8
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Q: 15. The experimental data for decomposition of in gas phase at are given below:




















(i) Plot against t
(ii) Find the halflife period for the reaction.
(iii) Draw a graph between and t.
(iv) What is the rate law?
(v) Calculate the rate constant.
(vi) Calculate the halflife period from k and compare it with (ii).
(i)
(ii) Time corresponding to the concentration, is the halflife. From the graph, the halflife is obtained as .
(iii)
t(s) 


0 


400 


800 


1200 


1600 


2000 


2400 


2800 


3200 


(iv) The given reaction is of the first order as the , is a straight line. Therefore, the rate law of the reaction is
(v) From the plot, we obtain
Again, slope of the line of the plot is given by
Therefore, we obtain,
(vi) Half –life is given by,
This value, 1483 is very close to the value that was obtained from the graph.
Q: 16. rate constant for a first order reaction is . How much time will it take to reduce the initial concentration of the reactant to its value?
Answer:
It is known that,
Hence, the required time is