A reaction A --> B has the following time dependence for the concentration of [A

Question

A reaction A --> B has the following time dependence for the concentration of [A] vs time. For t=(0 s, 5 s, 10 s, 15 s, 25 s) the concentration of [A]=(30.00 M, 17.91 M, 12.77 M, 9.92 M, 6.86 M). The initial concentration of [A] is the value at t=0 s.

(A)Calculate the values of the rate constant k assuming that the reaction is first order.
What is the value of k at 5 s? s-1
What is the value of k at 10 s? s-1
What is the value of k at 15 s? s-1
What is the value of k at 25 s? s-1
(B)Calculate the value of k assuming that the reaction is second order.
What is the value of k at 5 s? M-1s-1
What is the value of k at 10 s? M-1s-1
What is the value of k at 15 s? M-1s-1
What is the value of k at 25 s? M-1s-1
(C)Use your results from parts A and B above to decide what the order of the reaction is for your data. (Enter 1 or 2)
(D)What is the concentration of [A] at time t=62 s? M

Explanation / Answer

A) Since reaction is first order, A = A0e-kt

For t = 5, A = 30e-5kv = 17.91

=> k = 0.103

For t = 10, 12.77 = 30e-10k

=> k = 0.0854

For t = 15, 9.92 = 30e-kt

=> k = 0.074

For k = 25,

6.86 = 30e-kt

=> k = 0.059

B) If reaction is second order,

For t = 5, k = -0.5/t(1/A0 - 1/A)

=> k = 0.0025

For t = 10, k = 0.00248

For t = 15, k = 0.00249

For t = 25, k = 0.00248

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