The rate constant for a certain reaction is k = 4.20x10-3 s-1 . If the initial r

Question

The rate constant for a certain reaction is k = 4.20x10-3 s-1 . If the initial reactant concentration was 0.950 mol L-1, what wi the concentration be after 18.0 minutes? Express your answer with the appropriate units. Hints ? 0.886M Submit My Answers Give Up Incorrect; Try Again; 3 attempts remaining; no points deducted Part B A zero-order reaction has a constant rate of 1.50x10* mol Ls1. If after 35.0 seconds the con 9.00×10-2 mol L i, what was the initial concentration? Express your answer with the appropriate units. Hints Value Units Submit My Answers Give Up

Explanation / Answer

1)

we have:

[A]o = 0.950 M

t = 18.0 minutes = 18.0*60 s = 1080 s

k = 4.20*10^-3 s-1

use integrated rate law for 1st order reaction

ln[A] = ln[A]o - k*t

ln[A] = ln(0.95) - 4.2*10^-3*1080

ln[A] = -0.0513 - 4.2*10^-3*1080

ln[A] = -4.5873

[A] = 1.018*10^-2 M

Answer: 1.02*10^-2 M

B)

we have:

[A] = 0.09 M

t = 35.0 s

k = 1.5*10^-4 s-1

use integrated rate law for 1st order reaction

ln[A] = ln[A]o - k*t

ln(0.09) = ln[A]o - 1.5*10^-4*35

ln[A]o = -2.4079 + 1.5*10^-4*35

ln[A]o = -2.4027

[A]o = 0.0905 M

Answer: 0.0905 M

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