To understand how to use integrated rate laws to solve for concentration. A car

Question

To understand how to use integrated rate laws to solve for concentration.

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?

Part A

The rate constant for a certain reaction is k = 5.30×103 s1 . If the initial reactant concentration was 0.700 M, what will the concentration be after 9.00 minutes?

Part B

A zero-order reaction has a constant rate of 1.70×104M/s. If after 80.0 seconds the concentration has dropped to 6.00×102M, what was the initial concentration?

Explanation / Answer

A)
Unit of rate constant is s-1
So it is 1st order reaction.

t = 9 min = 9*60 s= 540 s
use for 1st order reaction:
[A]= [Ao]*e^(-k*t)
      = 0.7*e^(-5.3*10^-3 * 540)
      =0.04 M
Answer: 0.04 M

B)
use for zero order reaction:
[Ao]-[A]= k* t
[Ao]- (6*10^-2) = 1.7*10^-4 * 80
[Ao] = 0.0736 M

Answer: 0.0736 M

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