Question

a) At a certain temperature, the rate constant for this reaction is 5.09× 10–4 s–1. Calculate the half-life of cyclopropane at this temperature.

b) Given an initial cyclopropane concentration of 0.00190 M, calculate the concentration of cyclopropane that remains after 2.40 hours.

Answer #1

from the units of the rate constant it is clear that it is first order

units for first order reaction is s-1

relation between rate constant and half life is

t1/2 = 0.693 / k = 0.693 / 5.09× 10^{–4} s^{–1}
= 1.36 x 10^{3}

part B

formula for first order is

k = (2.303 / t ) x log[A0/A]

A0 = intial concentration which is given as 0.0019 M

A = concentration after 2.4 h

t = 2.4 h convert in to sec = 2.4 x 60 = 144 min x 60 = 8640 s

k = rate constant = 5.09× 10^{–4} s^{–1}

plug in these values

5.09× 10^{–4} s^{–1} = (2.303 / 8640 s ) x
log[0.0019 / A]

log[0.0019 / A] = 1.909

0.0019 / A = 10^{1.909}

0.0019 / A = 81.20

A = 0.0019 / 81.20

A = 0.0000234 or

A = 2.34 x 10^{-5} M

Consider the first-order reaction described by the equation
cyclopropane---propene
At a certain temperature, the rate constant for this reaction is
5.42× 10–4 s–1. Calculate the half-life of cyclopropane at this
temperature.
Given an initial cyclopropane concentration of 0.00510 M,
calculate the concentration of cyclopropane that remains after 1.70
hours.

Part A The rate constant for a certain reaction is k = 2.40×10−3
s−1 . If the initial reactant concentration was 0.650 M, what will
the concentration be after 18.0 minutes? Express your answer
with the appropriate units.
Part B
A zero-order reaction has a constant rate of
4.50×10−4M/s. If after 40.0 seconds the
concentration has dropped to 4.50×10−2M, what
was the initial concentration?
Express your answer with the appropriate units.

A certain second-order reaction (B→products) has a rate constant
of 1.60×10−3 M−1⋅s−1 at 27 ∘C and an initial half-life of 296 s .
What is the concentration of the reactant B after one
half-life?

Part A : A certain first-order reaction (A→products) has a rate
constant of 9.30×10−3 s−1 at 45 ∘C. How many minutes does it take
for the concentration of the reactant, [A], to drop to 6.25% of the
original concentration?
Part B : A certain second-order reaction (B→products) has a rate
constant of 1.10×10−3M−1⋅s−1 at 27 ∘C and an
initial half-life of 278 s . What is the concentration of the
reactant B after one half-life?

Part A: The rate constant for a
certain reaction is k = 5.00×10−3 s−1 . If the initial reactant
concentration was 0.250 M, what will the concentration be after
2.00 minutes?
Part B: A zero-order reaction has
a constant rate of 3.40×10−4 M/s. If after 80.0 seconds the
concentration has dropped to 6.00×10−2 M, what was the initial
concentration?

1.) The rate constant for a certain reaction is k =
3.40×10−3 s−1 . If the initial reactant concentration
was 0.550 M, what will the concentration be after 20.0
minutes?
2.)A zero-order reaction has a constant rate of
1.10×10−4
M/s. If after 80.0 seconds the concentration has
dropped to 9.00×10−2M, what was the initial
concentration?

Part A
A certain first-order reaction (A→products) has a rate constant
of 7.20×10−3 s−1 at 45 ∘C. How many minutes does it take
for the concentration of the reactant, [A], to drop to 6.25% of the
original concentration?
Express your answer with the appropriate units.
Answer:
6.42 min
Part B
A certain second-order reaction (B→products) has a rate constant
of 1.35×10−3M−1⋅s−1 at 27 ∘Cand an initial
half-life of 236 s . What is the concentration of the reactant B
after...

The rate constant for a certain reaction is k = 2.00×10−3 s−1 .
If the initial reactant concentration was 0.400 M, what will the
concentration be after 20.0 minutes? Express your answer with the
appropriate units.
Part B A zero-order reaction has
a constant rate of 4.70×10−4 M/s. If after 70.0 seconds the
concentration has dropped to 2.00×10−2 M, what was the initial
concentration?

A) The rate constant for a certain reaction is k = 2.60×10−3 s−1
. If the initial reactant concentration was 0.200 M, what will the
concentration be after 16.0 minutes
B)A zero-order reaction has a constant rate of
4.20×10−4M/s. If after 60.0 seconds the
concentration has dropped to 9.00×10−2M, what
was the initial concentration

Part A:
The rate constant for a certain reaction is k = 6.90×10−3 s−1 .
If the initial reactant concentration was 0.700 M, what will the
concentration be after 9.00 minutes
Part B:
A zero-order reaction has a constant rate of
4.90×10−4M/s. If after 45.0 seconds the
concentration has dropped to 7.00×10−2M, what
was the initial concentration?

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