2 An initial rate study was performed on the reaction system. Data for the exper

Question

2 An initial rate study was performed on the reaction system. Data for the experiment are given in the table below. A Using the information above, determine the order of the reaction with respect to each of the following: i) Cr ii) MnO4 B The reaction is known to be third order with respect to H+. Using this information, and your answers to part A above, complete the following: i) Write the rate law for the reaction ii) Calculate the value to the rate constant, k, including the appropriate units. C Calculate the rate of the reaction when [Cl] = 0.0250 M, [MnO4] = 0.0036 M and [H+] = 2.50 M. D Is it likely the reaction occurs in a single elementary step? Justify your answer.

Explanation / Answer

A )   

Let the rate law be

rate = K [ Cl-]^a [ Mn04-] ^b [ H+] ^c

consider trail 1 and 2 . both [Mn04-] and [ H+] are same in both the cases

so rate law is reduced to

rate 1 / rate 2 = [ Cl- 1 / Cl-2 ] ^ a

2.25 x 10-8 / 2.03 x 10-7 = [ 0.0104 / 0.0312 ] ^a

a = 2

1) so the order is 2 with respect to Cl-

now consider trail 2 and 3 , both [ Cl-] and [ H+] are same in both cases

the rate law reduced to

rate 2 / rate 3 = [ Mn04- 2 / Mn04- 3 ] ^b

2.03 x 10-7 / 1.02 x 10-7 = [ 0.004 / 0.002] ^b

b = 1

2) the order is 1 with respect to Mn04-

B) Given order is 3 with respect to H+

so the rate law is

rate = K [ Cl-]^2 [ Mn04-] [ H+]^3

consider trail 1

2.25 x 10-8 = K [ 0.0104]^2 [ 0.004] [ 3 ] ^3

K = 1.926 x 10-3 M-5 S-1

3) rate = 1.926 x 10-3 x [ 0.025]^2 x [ 0.0036] [ 2.50]^3

rate = 6.77 x 10-8

No it is not likely to take in a single elementary step

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