(1) What is the half-life for the reaction starting at t=0 s ? ______ s What is

Question

(1) What is the half-life for the reaction starting at t=0 s? ______s

What is the half-life for the reaction starting at t=1000 s? _______s

Does the half-life increase, decrease or remain constant as the reaction proceeds?

_________(increase/decrease/remain constant)

(2) Is the reaction zero, first, or second order? _______(zero/first/second)

(3) Based on these data, what is the rate constant for the reaction? Ms-1

Explanation / Answer

starting at T = 0sec , a = 0.00882 M

   half-concentration = 0.00882/2 = 0.00441 M, t = 1000 sec

   half -life(T1/2) = 1000 sec

starting at T = 1000 sec , a = 0.00441 M

half-concentration = 0.00441/2 = 0.0022 M, t = 1500 sec

   half -life = 1500-1000 = 500 sec

half life increases, as the reaction proceeds.

2) t1/2 x (1/a^(n-1))

(t1/2)1/(t1/2)2 = (a2/a1)^(n-1)

   (1000/500) = (0.00441/0.00882)^(n-1)

   n = order of reaction, = 0

so that, it is a zero order reaction.

zero order kinetics

k = [A]0-[A]/ t

let us take ,

[A]0 = initial concentration = 0.00882 M

[A] = concentration after first half life time(t) = 0.00441 M

first half life time(t1/2)1 = 1000 s

k = (0.00882-0.00441)/1000 = 4.41*10^-6 M.s-1

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