CHEMISTRY 216
General Chemistry II: Principles of Chemical Reactions
Winter Term, 2014
Homework Assignment #4 (13 points)
Due: Monday, February 3, 2014
1.
The following data were obtained for the decomposition of HOF at 25 oC..
2 HOF (g) → 2 HF (g) + O2(g)
time (min)
[ HOF ] mol/L
0
0.850
5
0.754
10
0.668
a.
b.
2.
From Figure 14-4 in the textbook (p. 561 in the 12th edition; p. 511 in the 11th edition) estimate the
a.
b.
3.
Calculate the average rate of disappearance of HOF during the first 5 minutes and during the
second 5 minutes.
What is the average rate of formation of O2 during the first 5 minutes?
average rate of decomposition of butyl chloride from 300 to 600 seconds
instantaneous rate of decomposition of butyl chloride at 400 seconds
The reaction between dihydrogen phosphate ion and the hydroxide ion is
H2PO 4–(aq) + OH–(aq) → HPO 42––(aq) + H2O(l)
The following data were obtained for this reaction.
[H2PO 4–] mol/L
0.0030
0.0030
0.0090
a.
b.
c.
4.
[OH –] mol/L
0.00040
0.00080
0.00040
Initial Rate of formation of HPO42– (mol/L sec)
2.0 x 10-3
8.0 x 10-3
6.0 x 10-3
What is the order of the reaction with respect to H2PO 4–, with respect to OH–, and the overall
order ?
Write the rate law for the reaction.
Determine the value of the rate constant, k.
Data for the decomposition of dinitrogen oxide (2 N2O(g) → 2 N2(g) + O2(g)) on a gold surface at
900 oC are given below.
time (min)
[N2O] mol/L
a.
b.
0
0.0998
30.0
0.0680
60.0
0.0464
90.0
0.0316
120.0
0.0216
Determine whether the reaction is zero, first, or second order. Show clearly how you reached
your conclusion.
Determine the rate constant, k.
5.
The decomposition of formic acid, HCO2H, is a first-order reaction with a rate constant of
1.9x 10-2 sec–1 at 550 oC.
HCO 2H(g) → CO2(g) + H2(g)
If one begins with a sample that is 0.200 M HCO 2H at 550 ˚C, calculate the concentration of HCO2H
after 2.5 minutes.
6.
Mercury is eliminated from the body in a first-order reaction with a half-life of 60 days. If a person
eats a piece of tuna fish contaminated with 1 milligram of mercury, how much of this mercury will
remain in the body after 150 days?
7.
Given the following rate-constant data on the gas-phase decomposition of N2O5
N2O5(g) → 2 NO 2(g) + 1/2 O2(g)
T (˚K)
k (sec–1)
a.
b.
8.
273
7.87 x 10–7
298
3.46 x 10–5
308
1.35 x 10–4
328
1.50 x 10–3
Use a plot of ln k versus 1/T to determine the activation energy of the reaction.
From the standard enthalpies of formation (Appendix C), calculate ∆Ho for this reaction and
draw an energy diagram similar to the diagrams shown in Exercise 14.10 (p. 579 in the12th
editiion; p. 595 in the 11th edition) showing Ea for both the forward and the reverse reaction
and ∆Ho. (Note: ∆Hfo for N2O5(g) = +11.3 kJ/mol)
Egg protein albumin is precipitated when an egg when an egg is cooked in boiling water. The
activation energy (Ea) for this first-order reaction is 52.0 kJ/mol. For many people, the ideal softboiled egg requires 3 minutes when the boiling water is 100 oC. Estimate the time required to prepare
this "3-minute" egg at an altitude where the temperature of boiling water is 90 oC.
Suggested Additional Problems:
Chapter 14: (12th Edition)
Visualizing Concepts: 14.3, 14.5, 14.8
Excercises: 14.19, 14.21 a, b, , 14.27, 14.31, 14.33, 14.37, 14.43, 14.49, 14.57, 14.65
Chapter 14: (11th Edition)
Visualizing Concepts: 14.2, 14.3, 14.6
Excercises: 14.15, 14.17, 14.23, 14.27, 14.29, 14.33, 14.37, 14.43, 14.51, 14.57
2

Chemistry 10123 and 10125, Exam 3 Answer Key March 3, 2014

Frühjahrsprüfung - SV OG Nienburg

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