Integrated Rate Laws Skills Check
1.
Determining the order of a chemical reaction and its half-life:
The following data were obtained for the decomposition of N2O5 in CCl4 at 45oC:
Initial concentration of Initial Rate, Ms-1
[N2O5]
0.50
1.55 E -4
1.0
3.10 E -4
1.5
4.65 E -4
a. Show that the reaction is first order.
b. What is the value of k?
c. What is the value of the half-life for the reaction?
2. Determining a rate constant from the half-life for a first-order chemical reaction
The half-life of a first-order reaction is 0.06 seconds. What is the rate constant for the reaction?
3. Use the specific rate constant for a first-order chemical reaction to determine concentration and
time.
N2O5 decomposes in the solvent CCl4 as follows:
2N2O5  4NO2 + O2
The specific rate constant for the first-order decomposition of N2O5 is 6.32 x10 -4 s-1.
a. What is the concentration of N2O5 remaining after 2 hours if the initial concentration of
N2O5 was 0.500 M?
b. How much time is required for 90% of the reactant to decompose?
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4.
Determining whether a chemical reaction is first-order or second-order.
Sucrose (C12H22O11), which is commonly known as table sugar, reacts in dilute acid solutions to
form two simpler sugars, glucose and fructose, both of which have the formula C6H12O6: At 23oC
and in 0.5M HCl, the following data were obtained for the disappearance of sucrose:
Time (min)
[C12H22O11] (M)
0
0.316
39
0.274
80
0.238
140
0.190
210
0.146
a. Is this reaction first order or second order with respect to Sucrose?
b. What is the value of the rate constant?
5.
Determining concentrations at a certain time for second order reactions.
Consider the decomposition of nitrogen dioxide. The reaction is second order in NO2 with
k=0.543 M-1s-1. If the initial concentration of NO2 in a closed vessel is 0.0500M, what is the
remaining concentration after 1.5 hours?
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