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 ml/hr in the direction of decreasing marker numbers. What mile maker will the car reach after 2 hours? This problem can easily be solved by calculating how far the car travels and subtracting that distance from the starting marker of 145. 55 mi/hr Times 2 hr = 110 miles traveled The rate constant for a certain reaction is k = 100 Times 10^-3 s^-1. If the initial reactant concentration was 0.750 M, what will the concentration be after 20.0 minutes? A zero-order reaction has a constant rate of 4.90 Times 10^-4 M/s. If after 60.0 seconds the concentration has dropped to 3.50 Times 10^-2 M, what was the initial concentration?

Explanation / Answer

Part A

Based on the rate constant, the reactin is first order and for first order reaction

CA/CAO= e-kt

Where CA= concentration at any time, t and CAO= initial concentration, 0.75M and

And k= rate consntant =1*10-3/sec= 10-3*60/min=0.06/min

CA=0.75*e(-0.06*20) =0.23M

Part B

For Zero order reaction CA= CAO-kt

CAO= CA+kt= 3.5*10-4 +60*4.9*10-4 =0.02975M ( initial concentration)

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