Q.A )The reactant concentration in a zero-order reaction was 8.00×10 2 M after 1

Question

Q.A )The reactant concentration in a zero-order reaction was 8.00×102M after 105 s and 3.50×102Mafter 300 s . What is the rate constant for this reaction? = answer= k0th = 2.31×104 Ms

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

C. The reactant concentration in a first-order reaction was 8.40×102M after 20.0 s and 8.40×103Mafter 95.0 s . What is the rate constant for this reaction?

D. The reactant concentration in a second-order reaction was 0.480 M after 140 s and 5.30×102M after 745 s . What is the rate constant for this reaction?

Thank you!

Explanation / Answer

A) rate constant = -(3.5 x 10^-2 - 8 x 10^-2)/(300-105) = 2.31 x 10^-4 M/s

B) For zero order reaction.

[A] = [Ao] - kt

with,

[A] = 0.08 M

t = 105 s

we get,

0.08 = [Ao] - 2.31 x 10^-4 x 105

initial concentration [Ao] = 0.104 M

C) rate constant for first order reaction

ln[A] = ln[Ao] - kt

with,

[A] = 8.4 x 10^-3 M

[Ao] = 8.4 x 10^-2 M

t = 95 - 20 = 75 s

we get,

ln(8.4 x 10^-3/8.4 x 10^-2) = -k x 75

rate constant (k) = 0.0307 s-1

D) For second order reaction,

1/[A] = 1/[Ao] + kt

with,

[A] = 5.3 x 10^-2 M

[Ao] = 0.480 M

t = 745 - 140 = 605 s

we get,

1/(0.053) = 1/(0.480) + k x 605

rate constant (k) = 0.0277 M-1.s-1

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