1) The reactant concentration in a zero-order reaction was 0.100 M after 125 s a

Question

1) The reactant concentration in a zero-order reaction was 0.100 M after 125 s and 4.00×102 M after 390 s . What is the rate constant for this reaction? Express your answer with the appropriate units. Indicate the multiplication of units, as necessary, explicitly either with a multiplication dot or a dash. THE ANSWER WAS k0th = 2.26×104 Ms

What was the initial reactant concentration for the reaction described in Part A?

2)The reactant concentration in a first-order reaction was 5.30×102 M after 45.0 s and 2.10×103 M after 65.0 s . What is the rate constant for this reaction? Express your answer with the appropriate units. Indicate the multiplication of units, as necessary, explicitly either with a multiplication dot or a dash.

3) The reactant concentration in a second-order reaction was 0.490 M after 200 s and 6.80×102 M after 710 s . What is the rate constant for this reaction? Express your answer with the appropriate units. Indicate the multiplication of units, as necessary, explicitly either with a multiplication dot or a dash.

Explanation / Answer

1.    Kt   = [ [A]0 - [A]t ]

       K(390-125)   = (0.1-0.04)

    K                  = 0.06/265   = 0.000226M/sec   = 2.26*10^-4M/sec

Kt   = [ [A]0 - [A]t ]

0.000226 *125 = [A]0 - 0.04

0.02825    = [A]0 - 0.04

[A]0           = 0.02825+0.04 = 0.06825M

2. K = 2.303/t log[A0]/[A]

        = 2.303/(65-45) log0.053/0.0021

        = 2.303*1.4020/20   = 0.16sec^-1

3. Kt = [ 1/[A] - 1/[A0]

   K(710-200) = [ 1/0.068 -1/0.49]

K*510          = 14.7-2.0408

K                     = 12.6592/510    = 0.0248M^-1sec^-1

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