1. You are studying the kinetics of a new reaction which turns product A-> B. Ho
ID: 697092 • Letter: 1
Question
1. You are studying the kinetics of a new reaction which turns product A-> B. However, we know that in many cases chemical reactions are much more complicated than this. Our new reaction is no exception. Reactant A can form more than one product. It can form a by-product C. So A can go through one of two reaction pathways, either A->B or A-> C. You have done some preliminary experiments to figure out the order of A with respect to each reaction and you have some assumption about what the k constants would be. You come up with the following equation to guide you along the way -d[A]/dt k1[A]A2+ k2[A] a) If you assume that k1 = 0.5 and k2 = 0.3 and your rate of disappearance is 1.5 M/s (at a time t) can you calculate the concentration of [A] at that moment? (5 pts) b) Write an equation similar to this for the appearance of product B. Assume that k1[AJA2 contributes to the appearance of B. (5 pts) c) For a slightly different reaction that looks like this-d/dt = k1[A] + k2 [A], can you find the integrated rate law. (10 pts)Explanation / Answer
a)
-d(A)/dt = k1(A)^2 + k2(A)
Rate of diappearence = 1.5 M/s = -d(A)/dt
K1 = 0.5 and k2 = 0.3
1.5 = 0.5(A)^2 + 0.3(A)
[A] = 1.458 M
b)
A ------> B
Rate disappearence = -d[A]/dt = k1[A]^2
Rate appearence = +d[B]/dt = k2[A]^2
c)
-d[A]/dt = k1[A] + k2[A]
-d[A]/dt = k1*k2[A]
-(1/[A])d[A] = k1*k2 dt
integrating on both sides with respect to them,
-ln[A] = k1*k2 * t + C
we will write k1*k2 = k3 another rate constant.
if t=0 then the above equation becomes,
-ln[A0] = 0 + c
c = -ln[A0]
substitute the c value in the above equation then,
-ln[A] = k3*t -ln[A0]
K3 = 1/t*ln[A0]/[A]
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