The reactant concentration in a zero-order reaction was 5.00×10 2 M after 140 s

Question

The reactant concentration in a zero-order reaction was 5.00×102M after 140 s and 2.50×102M after 325 s . What is the rate constant for this reaction?

k0th=1.35×104 Ms

Part C

The reactant concentration in a first-order reaction was 5.30×102M after 20.0 s and 5.60×103M after 70.0 s . What is the rate constant for this reaction?

Express your answer with the appropriate units.

Part D

The reactant concentration in a second-order reaction was 0.620 M after 150 s and 5.20×102M after 785 s . What is the rate constant for this reaction?

Express your answer with the appropriate units. Include an asterisk to indicate a compound unit with mulitplication, for example write a Newton-meter as N*m.

k0th=1.35×104 Ms

Part C

The reactant concentration in a first-order reaction was 5.30×102M after 20.0 s and 5.60×103M after 70.0 s . What is the rate constant for this reaction?

Express your answer with the appropriate units.

Part D

The reactant concentration in a second-order reaction was 0.620 M after 150 s and 5.20×102M after 785 s . What is the rate constant for this reaction?

Express your answer with the appropriate units. Include an asterisk to indicate a compound unit with mulitplication, for example write a Newton-meter as N*m.

Explanation / Answer

for zero order, rate = k
[A] = [A]º - k t
0.025M = 0.05M - k(185sec)
0.025M = 185k
k = 1.35x10^-4M/sec

[A] = [A]º - k t
0.025M = [Aº] - (1.35x10^-4M/sec x 140sec)
0.0439M = [Aº]

C)
[A] = [A]º e^(-kt)
0.0056M = 0.053M x e^(k x 50sec)
0.1056 = e^(-50k)
ln0.1056 = -50k
-2.247 = -50k
k = 0.045/sec

D)
[A] = [A]º/ 1 + k t [A]º
[A] = 0.052M
[Aº] = 0.62M
t = 785sec - 150sec=635 sec

0.052M=0.62M+k(635*0.62M)

0.916=k635

k=0.00144/sec

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