- Information for your use:
K = °C + 273
R = 0.08206 Latm/mol·K
K = 8.314 J/mol· K
[A] = [A]o- kt
ln[A] = ln[A]o - kt
ln ([A]/[A]o) = -kt
kt½ = ln2 = 0.693
1/[A] = 1/[A]o+ kt
k = Ae-Ea/RT
ln (k2/k1) = (-Ea/R)(1/T2 - 1/T1)
pH = - log [H3O+]
pOH = - log [OH-]
At 25 ° C: [H3O+] [OH-] = 1.0x10-14
pH + pOH = 14
1. (4 Points)
A catalyst increases the rate of a chemical reaction by
raising
the temperature
increasing
the concentration
increasing
the fraction of molecules with a given energy
providing
a lower energy pathway for the reaction
decreasing
DH
for the reaction
2. (6 points)
For the reaction in aqueous solution, 2UO2+ + 4H+®
U4+ + UO22+ + 2H2O , the following
initial rates were obtained: From these data, the rate law for the reaction
is:
| [UO2+],M | [H+],M | Initial Rate, Ms-1 |
| 0.0030 | 0.200 | 2.34 x 10-4 |
| 0.0030 | 0.400 | 4.68 x 10-4 |
| 0.0015 | 0.400 | 1.17 x 10-4 |
Rate
= k[UO2+][H+]
Rate
= k[UO2+]2[H+]
Rate
= k[UO2+][H+]2
Rate
= k[UO2+]2[H+]4
Rate
= k[UO2+]1/2[H+]
3. (5 Points)
The rate constant for the zero order decomposition of
NH3 on a tungsten surface at 1100 ºC is 2.0 x 10-4
M min-1 . If the initial concentration of NH3 is
0.0060 M, how many minutes are required for the concentration to drop to
0.0050 M?
5.09.5142142
4. (4 Points)
The isotope iodine-131 has a half-life of 8.05 days and decays by first
order kinetics. What is the rate constant, including units, for the decay
reaction?
8.05
day
6.96
x 105 sec
1.44
x 10-6 sec-1
1.24
x 10-3 day-1
8.61
x 10-2 day-1
5. (5 Points)
For the decomposition of hypobromite ion in aqueous solution, 3BrO-®
BrO3- + 2Br-, it is observed that a plot
of 1 / [BrO-] versus time in seconds gives a straight line with
a slope of 0.056 M-1s-1. The rate law for this reaction
is:
Rate
= 0.056
Rate
= 0.056[BrO-]
Rate
= 0.056[BrO-]2
Rate
= 12[BrO-]
Rate
= 12[BrO-]2
6. (5 Points)
The following data are for the gas phase decomposition of di-t-butyl
peroxide (DTBP) to form acetone and ethane, C8H18O2(g)
®
2C3H6O(g) + C2H6(g), at 420K.
The order of the reaction with respect to DTBP is:
| [DTBP], M | 24.8 | 12.4 | 6.2 | 3.1 |
| time, min | 0 | 80 | 160 | 240 |
zerofirstsecondminus
oneminus
two
NO2 + F2 ® NO2F + F slow
F + NO2 ® NO2F fast
7. ( 4 Points)
The overall reaction is
NO2
+
F2 ® NO2 F +
F
F +
NO2 ® NO2 F
2NO2
+ F2 ® 2NO2 F
NO2
+ F ® NO + OF
NO2
+ F2 ® NO + O2 F2
8. (3 Points)
The catalyst is:
NO2
F2
NO2
F
F
there
is none
9. (4 Points)
The rate law consistent with this mechanism is:
Rate
= k[NO2]
Rate
= k[NO2]2
Rate
= k[NO2]2[F2]
Rate
= k[F][NO2]
Rate
= k[NO2][F2]
10. (4 Points)
At 298K he equilibrium constant for the reaction NH4HS(s)
«
NH3(g) + H2S(g) is 1.8 x 10-4. If an equilibrium
mixture of the three compounds in a 1.00 L container contains 0.50 mol
NH4HS(s) and 0.012 mol H2S(g), how many moles of
NH3(g) are present?
0.00750.0150.0300.330.67
For the equilibrium N2(g) + O2(g) « 2NO(g) , the equilibrium constant has a value of 4.5 x 10-31 at 298K. Which of the following are true? Choose all that apply.
- When a sample of NO is introduced into an evacuated container at 298K, at equilibrium most of the sample will have decomposed to form N2 and O2 .
- When equal amounts of N2 and O2 are mixed in an evacuated container at 298K, at equilibrium about half of each will have reacted to form NO.
- Fortunately gaseous mixtures of N2 and O2 do not react to an appreciable extent at 298K or we would all be breathing NO.
1
only2 only3
only1 and
21 and
3
2 H2(g) + CO(g) « CH3OH(g) DH = - 103 kJ and Kc = 25.6 at 200° C.
12. (4 Points)
If the volume of the above equilibrium system is decreased at constant temperature, the amount of CH3OH will
increasedecreasenot
changedecrease
then increaseincrease
then decrease
13. (4 Points)
If the temperature of the above equilibrium system is increased, the
value of the equilibrium constant will
increasedecreasenot
changedecrease
then increaseincrease
then decrease
14. (4 Points)
What is the value of Kc at 200 °C for the reaction ½
CH3OH(g) « H2(g)
+ ½ CO(g)
0.03910.1985.0625.6640
15. (4 Points)
The following equilibrium takes place in aqueous solution. At very
high chloride ion concentrations, when the total concentration of the cobalt
species is about 1 M, the equilibrium system would appear:
Co(H2O)62+ + 4Cl- « CoCl42- + 6H2O Co(H2O)62+ is pink CoCl42- is blue
pink
due to the pink color of the aquo complex
blue
due to the blue color of the chloro complex
colorless
due to the high concentration of the colorless chloride ion
pinkish-blue
since both colored species are present in comparable amounts
green
because chlorine gas, which is green, would form
16. (4 Points)
Which one of the following aqueous solutions is basic?
pH =
4.0
[OH-]
= 4.0x10-8
pH
= 6.9
[H3O+]
= 2.0x10-7
none
are basic
17. (4 Points)
What is the hydroxide ion concentration in an aqueous solution that
has a pH of 4.40 at 25 ° C?
2.5
x 10-10
3.8
x 10-9
1.5
x 10-7
5.7
x 10-6
4.0
x 10-5
HF + H2O « H3O+ + F–
18. (4 Points)
The two acids in the equilibrium system are
HF and
H2O
H3O+
and F–
HF
and H3O+
H2O
and F–
there
is only one acid
19. (4 Points)
The conjugate ______ of HF is ______ .
acid,
H2O
base,
F–
acid,
H3O+
base,
H2O
acid,
F–
Draw a reaction coordinate diagram for a typical exothermic reaction, reactants ® products, in the space below. Label the diagram clearly, indicating the reactants, the products, and the activation energy. With reference to this diagram, explain why for most reactions the rate of the reaction increases with increasing temperature.
Do a calculation to show what activation energy corresponds to the rule of thumb that the rate of a reaction near 25 °C (298K) doubles for each 10 degree rise in temperature.
CH3OH(g) « CO(g) + 2H2(g)
22. (5 Points)
When 1.000 mole of methanol, CH3OH(g), is introduced into an evacuated 10.0 L container at 500K, the equilibrium amount of CO(g) is found to be 0.753 moles. What is the value of Kc at 500K?
Hint: ICE might help your thinking.
If a mixture of the three gases at 500K is introduced into a container so that the initial concentration of all three gases is 0.500 M, describe what will happen? Hint: Use your value of Kc from question 22.
