April 2014
Chem 1312- Honors
Exam 3
READ DIRECTIONS
Read Directions
LAST Name __________________________
First Name _________________________
1. lAST NAME 1ST ON SCANTRON
2.DoNot Erase Scantron
3. Nomenclature on Back of Scntron As shown only
4. Turn in Scantron only
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1) The elementary reaction representing the formation of ozone:
O2 ( g ) + O(g ) + M(g )
O3 ( g ) + M* ( g ) is an example of a ________ reaction.
A) tetramolecular
B) unimolecular
C) bimolecular
D) termolecular
1)
2) A mechanism for a naturally occurring reaction that destroys ozone is:
Step 1: O3 ( g ) + HO(g )
HO2 ( g ) + O2 ( g )
Step 2: HO2 ( g ) + O(g )
HO(g ) + O2 ( g )
2)
Which species is an intermediate?
A) H O2
B) O
C) O3
D) H O
3) The slowest step in a reaction mechanism is called the ________ step.
A) rate-determining
B) activation
C) elementary
D) rate law
3)
4) Which of the following statements are true about reaction mechanisms?
I. A rate law can be written from the molecularity of the slowest elementary step.
II. The final rate law can include intermediates.
III. The rate of the reaction is dependent on the fastest step in the mechanism.
IV. A mechanism can never be proven to be the correct pathway for a reaction.
A) I, II, III
B) I, III
C) II, IV
D) I, IV
4)
5) When the concentration of A is doubled, the rate for the reaction: 2 A + B
2 C quadruples.
When the concentration of B is doubled the rate remains the same. Which mechanism below is
consistent with the experimental observations?
A) Step 1: A + B
B) Step 1: A + B
D (fast equilibrium)
D (slow)
Step 2: A + D
2 C (slow)
Step 2: A + D
2 C (fast equilibrium)
5)
C) Step 1: 2 A
D (fast equilibrium)
Step 2: B + D
E (slow)
Step 3: E
2 C (fast)
D) Step 1: 2 A
D (slow)
Step 2: B + D
E (fast)
Step 3: E
2 C (fast)
6) What factor affects the rate of a chemical reaction?
A) orientation of molecules
B) fraction of collisions with sufficient energy
C) collision frequency
D) All of these
6)
7) The fraction of collisions with sufficient energy to react is equal to
A) p
B) e-Ea/RT
C) A
7)
1
D) Ea
8) When the temperature of a gas whose activation energy is 55 kJ/mol is increased from 300 K to
320 K, the fraction of collisions with sufficient energy to react
A) decreases by a factor of 4.
B) decreases by a factor of 2.
C) increases by a factor of 2.
D) increases by a factor of 4.
8)
9) Consider a bimolecular reaction in the gas phase. Which one of the following changes in
condition will not cause an increase in the rate of the reaction?
A) increase the volume at constant temperature
B) increase the temperature at constant volume
C) add a catalyst
D) All of these will increase the rate of reaction.
9)
10) A catalyst increases the rate of a reaction by providing a different reaction pathway that
A) lowers only the energy of the products.
B) lowers only the energy of the reactants.
C) lowers only the activation energy.
D) All of these are affected by the presence of a catalyst.
10)
11) A mechanism for a naturally occurring reaction that destroys ozone is:
Step 1: O3 ( g ) + HO(g )
HO2 ( g ) + O2 ( g )
Step 2: HO2 ( g ) + O(g )
HO(g ) + O2 ( g )
11)
Which species is a catalyst?
A) O
B) H O2
C) H O
D) O3
12) Which of the following does not affect the rate of a bimolecular reaction?
A) temperature
B) presence of a catalyst
C) concentrations of reactants
D) All of these affect the rate.
12)
13) The Haber process is the synthesis of ammonia gas from hydrogen and nitrogen on a hot metal
surface. What is the catalyst and what type of catalysis is occurring?
A) NH3 , homogeneous
B) H 2 , homogeneous
C) N 2 , homogeneous
D) metal surface, heterogeneous
13)
14) Biological reactions are catalyzed by
A) lipids.
B) steroids.
14)
C) carbohydrates.
D) enzymes.
15) The equilibrium equation is also known as the law of
A) constant concentration.
B) dynamic equilibrium.
C) coefficients.
D) mass action.
15)
16) Which of the following statements is false regarding the equilibrium constant, Kc ?
A) The numerical value of Kc depends on the form of the balanced equation.
16)
B) Kc for a reaction at a particular temperature always has the same value.
C) When quoting Kc it is customary to omit units.
D) Kc for the reverse reaction is the negative of Kc for the forward reaction.
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17) What is the activation energy for the destruction of ozone?
A) 392 kJ
B) 406 kJ
C) 14 kJ
17)
D) none of these
18) Which statement about the equilibrium constant is true? The value of Kc
A) changes as reactant concentration changes.
B) never changes.
C) changes as temperature changes.
D) changes as product concentration changes.
18)
19) Which statement is true for a reaction with Kc equal to 2.43 × 10-12?
A) Increasing the temperature will not change the value of Kc .
19)
B) The reaction proceeds hardly at all towards completion.
C) The reaction proceeds nearly all the way to completion.
D) There are appreciable concentrations of both reactants and products.
20) What is true about the relationship of Kp and Kc for the reaction:
2 CH4 ( g ) + 3 O2 ( g )
A) Kp > Kc
C) Kp = Kc
2 CO(g ) + 4 H2 O(g )?
B) Kp and Kc are not related.
D) Kp < Kc
21) If Kc is the equilibrium constant for a forward reaction, 2 A
A
20)
B, what is Kc for the reaction 4
21)
2B?
A) Kc
B) 2 Kc
C)
1 K
c
2
D) ( Kc ) 2
22) For which one of the following reactions will Kc = Kp?
A) COCl2 ( g )
B) ZnO(s ) + CO(g )
CO(g ) + Cl2 ( g )
Zn(s ) + CO2 ( g )
C) CO(g ) + 2 H2 ( g )
D) 2 O3 ( g )
CH3 OH(g )
3 O2 ( g )
3
22)
23) If Kc = 0.900, and Kp = 538 for a hypothetical reaction, which of the equations below could
represent the reaction at 25°C?
A) A(g )
B) A(g ) + B(s )
2 C(s ) + D(g )
3 C(g )
C) B(g )
D) A(l ) + 2 B(g )
C(l) + D(l )
2 C(g )
23)
24) The oxidation of sulfur dioxide by oxygen to sulfur trioxide has been implicated as an
important step in the formation of acid rain: SO2 ( g ) + O2 ( g )
SO3 ( g ). If the equilibrium
partial pressures of SO2 , O2 , and SO3 are 0.564 atm, 0.102 atm, and 0.333 atm respectively at
1000 K, what is Kp at that temperature?
24)
A) 8.11
B) 3.42
C) 5.79
D) 0.292
25) A 1.50 L vessel contains an equilibrium mixture of 0.100 mol of NO, 0.150 mol of Br2 , and
0.250 mol of NOBr at 25°C. What is the value of Kp for the reaction below?
A) 2.56
2 NO(g ) + Br2 ( g )
B) 62.5
25)
2 NOBr(g )
C) 1.53 × 103
D) 1.28 × 102
26) "If a stress is applied to a reaction mixture at equilibrium, the reaction occurs in the direction
that will relieve the stress." This statement is called
A) the Law of Combining Volumes.
B) the Law of Mass Action.
C) Le Châtelier's principle.
D) the First Law of Thermodynamics.
26)
2 Cl2 ( g ) + 2 H2 O(l ), the equilibrium constant is 0.063 at
27) For the reaction: 4 HCl(g ) + O2 ( g )
400 K. If the reaction quotient is 0.100, which of the following statements is not correct?
A) [O2 ] will increase.
B) [HCl] will increase.
C) [Cl2 ] will decrease.
D) [H2 O] will increase.
27)
28) Iron oxide ores are reduced to iron metal by exothermic reaction with carbon monoxide:
FeO(s ) + CO(g )
Fe(s ) + CO2 ( g )
28)
Which of the following changes in condition will cause the equilibrium to shift to the right?
A) add CO2
B) raise the temperature
C) add CO
D) add FeO
29) A Br nsted-Lowry acid is best defined as a substance that can
A) accept a hydroxide ion.
B) donate a proton.
C) donate a hydroxide ion.
D) accept a proton.
29)
30) What are the Br nsted-Lowry bases in the following chemical reaction?
C 5 H 5 N(aq) + H2 O(l)
C5 H 5 NH+(aq) + OH-(aq)
30)
A) C 5 H 5 N, H2 O, OH-
B) C 5 H 5 N, C5 H 5 NH+
D) C 5 H 5 N, OH-
C) C 5 H 5 N, H2 O
31) What is the conjugate base of the Br nsted-Lowry acid HPO4 2- ?
A) HPO4 2B) H 2 PO4 C) H 3 PO4
31)
D) PO4 3-
32) What is the hydronium ion concentration of an acid rain sample that has a pH of 3.15?
A) 1.41 × 10-11 M
B) 10.85 M
C) 7.08 × 10-4 M
D) 3.15 M
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32)
33) Human tears have a concentration of H3 O+ that is 3.16 × 10-8 . The concentration of OH- in
human tears is
A) greater than 3.16 × 10-7 and tears are acidic.
33)
B) greater than 3.16 ×10-7 and tears are basic.
C) less than 3.16 × 10-7 and tears are basic.
D) less than 3.16 × 10-7 and tears are acidic.
34) What is the pH of a 0.020 M Barium Hydroxide solution?
A) 1.40
B) 12.60
C) 1.70
34)
D) 12.30
35) The pH of 0.150 M acetic acid, is 2.78. What is the value of Ka for acetic acid?
A) 2.8 × 10-6
B) 1.1 × 10-2
C) 1.7 × 10-3
D) 1.9 × 10-5
36) BF3 and NH3 undergo a Lewis acid-base reaction forming an adduct. Which picture below
correctly represents the curved arrow notation for the initial Lewis acid-Lewis base
interaction in this reaction; what is the Lewis acid and the Lewis base?
A) Picture (3) is correct; NH3 is the Lewis acid and BF3 is the Lewis base.
B) Picture (1) is correct; NH3 is the Lewis acid and BF3 is the Lewis base.
C) Picture (2) is correct; BF3 is the Lewis acid and NH3 is the Lewis base.
D) Picture (4) is correct; BF3 is the Lewis acid and NH3 is the Lewis base.
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35)
36)