Part A Learning Goal To understand how to use integrated rate laws to solve for

Question

Part A Learning Goal To understand how to use integrated rate laws to solve for concentration The rate constant for a certain reaction is k7.40x103 s-1If the initial reactant concentration was 0.450 what will the concentration be after 18.0 minutes? Express your answer with the appropriate units A car starts at mile marker 145 on a highway and drives at 55 mi/hr in the direction of decreasing marker numbers. What mile marker will the car reach after 2 hours? View Available Hint(s) This problem can easily be solved by calculating how far the car travels and subtracting that distance from the starting marker of 145 IA alue Units Figure 1 of 2 > Submit Previous Answers Request Answer X Incorrect; Try Again; 5 attempts remaining Part B A zero-order reaction has a constant rate of 4.90x10-4 M/s. If after 60.0 seconds the concentration has dropped to 3.50x102 M, what was the initial concentration? Express your answer with the appropriate units View Available Hint(s)

Explanation / Answer

A)
we have:
[A]o = 0.450 M
t = 18.0 min = 18.0*60 s = 1080 s
k = 7.4*10^-3 s-1
seeing the unit of k, we can say that it is 1st order reaction

use integrated rate law for 1st order reaction
ln[A] = ln[A]o - k*t
ln[A] = ln(0.45) - 7.4*10^-3*1080
ln[A] = -0.7985 - 7.4*10^-3*1080
ln[A] = -8.7905
[A] = 1.52*10^-4 M
Answer: 1.52*10^-4 M

B)
we have:
[A] = 0.035 M
t = 60.0 s
k = 4.9*10^-4 M/s

use integrated rate law for 0 order reaction
[A] = [A]o - k*t
0.035 = [A]o - 4.9*10^-4*60
[A]o = 0.064 M
Answer: 0.064 M

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