Learning Goal: To understand how to use integrated rate laws to solve for concen

Question

Learning Goal: 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? 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×2 hr=110 miles traveled

Part A

The rate constant for a certain reaction is k = 7.60×103 s1 . If the initial reactant concentration was 0.550 M, what will the concentration be after 17.0 minutes?

Express your answer with the appropriate units.

Part B

A zero-order reaction has a constant rate of 1.40×104M/s. If after 80.0 seconds the concentration has dropped to 1.50×102M, what was the initial concentration?

Express your answer with the appropriate units

Explanation / Answer

Part A.

from the unit of rate constant, the reaction is first order.

Thus Ln[A0/At] = Kt ; Ln [0.55/At] = 7.60*10-3 *17*60 = 7.752 ; Ln [0.55/At] = 7.752

At=0.55/e7.752 = 0.0002364 M

Part B;

for zero order reaction, A0 - At = Kt ; thus A0 = At + K*t = 1.50×102 M + 1.40×104*80 M = 0.015 +0.0112 = 0.0262 M

therefore , initial concentration is 2.62*10-2 M

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