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Chapter 11
The reaction for the Haber process, the industrial production of ammonia, is
N2(g) + 3 H2(g) → 2 NH3(g)
Assume that under certain laboratory conditions ammonia is produced at the rate
of 6.29  10–5 mol L–1 s–1. At what rate is nitrogen consumed? At what rate is
hydrogen consumed?
The following data were obtained in the decomposition of H2O2(aq) to O2(g) and
H2O(). The rate at which oxygen gas was produced was measured. (No oxygen
was present initially.)
(a) Calculate the average rate in mL/min for the first 3.3 minutes.
(b) Calculate the average rate in mL/min for the first 6.9 minutes.
The reaction of CO(g) + NO2(g) is second-order in NO2 and zero-order in CO at
temperatures less than 500 K.
(a) Write the rate law for the reaction.
(b) How will the reaction rate change if the NO2 concentration is halved?
(c) How will the reaction rate change if the concentration of CO is doubled?
One reaction that destroys O3 molecules in the stratosphere is
NO + O3 → NO2 + O2
When this reaction was studied in the laboratory, it was found to be first order
with respect to both NO and O3, with a rate constant of 1.9  104 L mol–1 s–1. If
[NO] = 1.2  10–5 mol L–1 and [O3] = 2.0  10–5 mol L–1, what is the rate of this
The rate of the decomposition of hydrogen peroxide, H2O2, depends on the
concentration of iodide ion present. The rate of decomposition was measured at
constant temperature and pressure for various concentrations of H2O2 and of KI.
The data appear below. Determine the order of reaction for each substance, write
the rate law, and evaluate the rate constant.
The following experimental data were obtained for the reaction
Determine the reaction order for each reactant and the value of the rate constant.
Rate data were obtained at 25°C for the following reaction. What is the rate law
for this reaction?
Expt. Initial [A] Initial [B]
(mol L–1) (mol L–1)
Initial Rate of
Formation of C
(mol L–1 min–1)
3.0  10–4
9.0  10–4
3.0  10–4
6.0  10–4
A possible reaction for the degradation of the pesticide DDT to a less harmful
compound was simulated in the laboratory. The reaction was found to be firstorder, with k = 4.0  10–8 s–1 at 25°C. What is the half-life for the degradation of
DDT in this experiment, in years?
A substance undergoes first-order decomposition. After 40.0 min at 500°C, only
12.5% of the original sample remains. What is the half-life of the decomposition?
If the original sample weighed 243 g, how much would remain after 2.00 hr?
The labels on most pharmaceuticals state that the medicine should be stored in a
cool, dark place. In the context of this chapter, explain why this is sound advice.
The table below presents measured rate constants for the reaction of NO with
ozone at three temperatures. From these data, determine the activation energy of
the reaction in kJ/mol. (Assume the temperatures all have two significant
Many reactions occur in the formation of photochemical smog, including the
reaction of ozone with various volatile organic chemicals, or VOCs. The table
below shows the Arrhenius expression for four such reactions.
(a) Which reaction is likely to be the fastest at 310 K?
(b) Which reaction has the lowest activation energy?
(c) Which has the highest activation energy?
Show the details of your calculation.
What is the rate law for each of the following elementary reactions?
(a) Cl(g) + ICl(g) → I(g) + Cl2(g)
(b) O(g) + O3(g) → 2 O2(g)
(c) 2 NO2(g) → N2O4(g)
HBr is oxidized in the following reaction:
4 HBr(g) + O2(g) → 2 H2O(g) + 2 Br2(g)
A proposed mechanism is
HBr + O2 → HOOBr
HOOBr + HBr → 2 HOBr
HOBr + HBr → H2O + Br2
(a) Show that this mechanism can account for the correct stoichiometry.
(b) Identify all intermediates in this mechanism.
(c) What is the molecularity of each elementary step?
(d) Write the rate expression for each elementary step.
(e) Identify the rate-determining step.
The following statements relate to the reaction for the formation of HI:
H2(g) + I2(g) → 2 HI(g)
Rate = k[H2][I2]
Determine which of the following statements are true. If a statement is false,
indicate why it is incorrect.
(a) The reaction must occur in a single step.
(b) This is a second-order reaction overall.
(c) Raising the temperature will cause the value of k to decrease.
(d) Raising the temperature lowers the activation energy for this reaction.
(e) If the concentrations of both reactants are doubled, the rate will double.
(f) Adding a catalyst in the reaction will cause the initial rate to increase.
Experiments show that the reaction of nitrogen dioxide with fluorine
2 NO2(g) + F2(g) → 2 FNO2(g)
has the rate law
Rate = k[NO2][F2]
The reaction is thought to occur in two steps.
Step 1: NO2(g) + F2(g) → FNO2(g) + F(g)
Step 2: NO2(g) + F(g) → FNO2(g)
(a) Show that the sum of this sequence of reactions gives the balanced equation
for the overall reaction.
(b) Which step is rate determining?
Homework 11 Chapter 12
Name ________________ Student ID ______________ Date ______________
Write equilibrium (mass action) expressions for each of the following reactions:
(a) H2(g) + I2(g)
(b) 2 NO(g) + O2(g)
(c) N2(g) + 3 H2(g)
(d) CO(g) + NO2(g)
(e) 2 CO(g) + O2(g)
2 NO2(g)
2 NH3(g)
CO2(g) + NO(g)
2 CO2(g)
Write equilibrium expressions for each of the following equilibria:
(a) 2 C(s) + O2(g)
(b) Zn2+(aq) + H2S(g)
ZnS(s) + 2 H+(aq)
(c) HCl(g) + H2O()
H3O+(aq) + Cl–(aq)
(d) H2(g) +
2 HI
Which of the following is more likely to precipitate the hydroxide ion?
(a) Cu(OH)2(s)
(b) Ca(OH)2(s)
Cu2+(aq) + 2 OH–(aq)
Ca2+(aq) + 2 OH–(aq)
K = 1.6  10–20
K = 7.9  10–6
The reaction, 3 H2(g) + N2(g)
2 NH3(g), has the following equilibrium
constants at the temperatures given:
at T = 25°C, K = 2.8  104
at T = 500°C, K = 2.4  10–7
(a) At which temperature are reactants favored?
(b) At which temperature are products favored?
Consider the following equilibria involving SO2(g) and their corresponding
equilibrium constants:
SO2(g) +
2 SO3(g)
2 SO2(g) + O2(g)
Which of the following expressions relates K1 to K2?
(a) K2 = K12
(b) K22 = K1
(c) K2 = K1
(d) K2 = 1/K1
(e) K2 = 1/K12
The following data were collected for the reaction, H2(g) + I2(g)
2 HI(g),
at equilibrium at 25°C.
[H2] = 0.10 mol L–1, [I2] = 0.20 mol L–1, [HI] = 4.0 mol L–1
Calculate the equilibrium constant for the reaction at this temperature.
The equilibrium constant for the reaction, 3 H2(g) + N2(g)
2 NH3(g), at
a given temperature is 1.4  10–7. Calculate the equilibrium concentration of
ammonia, if [H2] = 1.2  10–2 mol L–1 and [N2] = 3.2  10–3 mol L–1.
Hydrogen gas and iodine gas react via the following equation:
H2(g) + I2(g)
2 HI(g)
Kc = 76 (at 600 K)
If 0.050 mol HI is placed in an empty 1.0-L flask at 600 K, what are the
equilibrium concentrations of HI, I2, and H2?
The equilibrium constant of the reaction of Cl2(g) with PCl3(g) to produce
PCl5(g) is 51 at a particular temperature. If the initial concentration of PCl3 is
0.012 mol L–1 and the initial concentration of Cl2 is 0.125 mol L–1, what are the
equilibrium concentrations of all species?
At a particular temperature, the equilibrium constant, K, for the dissociation of
N2O4 into NO2 is 133. If the initial concentration of N2O4 is 0.100 mol L–1, what
are the concentrations of all species at equilibrium?
2 NO2
The following reaction is in equilibrium in lake water:
HCO3–(aq) + H+(aq)
Predict the change in the reaction quotient, Q, for each disturbance below, and
use that prediction to explain how the equilibrium is shifted by the stress.
(a) NaHCO3 is added to the lake.
(b) H2CO3 is added.
(c) NaOH is added.
In each of the reactions, how does the equilibrium respond to an increase in
(a) 2 SO2(g) + O2(g)
(b) H2(g) + I2(g)
2 HI(g)
How would a temperature increase affect each of the equilibria below?
(a) AgNO3(s)
(b) C(s) + O2
2 SO3(g)
Ag+(aq) + NO3–(aq)
∆H° = 22.6 kJ mol–1
∆H° = –209 kJ mol–1
2 CO(g)
Consider the following system:
4 NH3(g) + 3 O2(g)
2 N2(g) + 6 H2O()
H = –1530.4 kJ
(a) How will the amount of ammonia at equilibrium be affected by
(1) removing O2(g)?
(2) adding N2(g)?
(3) adding water?
(4) expanding the container at constant pressure (by increase temperature)?
(b) Which of the above factors will increase the value of K? Which will decrease
15. Write the Ksp expression for each of the following equilibria for dissolution of the
salt in water:
(a) AgI(s)
Ag+(aq) + I–(aq)
(b) PbI2(s)
Pb2+(aq) + 2 I–(aq)
(c) Hg2I2
Hg22+(aq) + 2 I–(aq)
(d) Cu(IO3)2
Cu2+(aq) + 2 IO3–(aq)
Because barium sulfate is opaque to X-rays, it is suspended in water and taken
internally to make the gastrointestinal tract visible in an X-ray photograph.
Although barium ion is quite toxic, barium sulfate’s Ksp of 1.1  10–10 gives it
such low solubility that it can be safely consumed.
(a) What is the molar solubility of BaSO4?
(b) What is its solubility in grams per 100 g of water?
Calculate the Ksp of the following compounds, given their molar solubilities: (a)
AgCN, 7.73  10–9 M, (b) Ni(OH)2, 5.16  10–6 M, (c) Cu3(PO4)2, 1.67  10–8 M
Will a precipitate of Mg(OH)2 form when 25.0 mL of 0.010 M NaOH is combined
with 75.0 mL of a 0.10 M solution of magnesium chloride? The Ksp is 1.6  10–13
19. What are the products of each of the following acid–base reactions? Indicate the acid
and its conjugate base and the base and its conjugate acid.
(a) NH3 + H2O
(b) NH4+ + H2O
(c) CH3COOH + H2O
20 The ionization constant of a very weak acid, HA, is 4.0  10–9. Calculate the
equilibrium concentrations of H3O+, A, and HA in a 0.040 M solution of the acid.

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