1042_1st Exam_1050330(A)
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1) For the reaction: 2N2O5(g) 4NO2(g) + O2(g) the rate law is:
[O2]
t =k[N2O5]
At 300 K, the half-life is 2.50 × 104 seconds and the activation energy is 103.3 kJ/mol O2. At the time when N2O5 is being consumed at a rate of 1.2 × 10-4 M/s, what is the rate at which NO2 is being formed?
A) 3.0 × 10-5 M/s B) 2.4 × 10-4 M/s C) 6.0 × 10-5 M/s D) 1.2 × 10-4 M/s E) 4.8 × 10-4 M/s Answer: B
2) The reaction has the rate law Rate = k[A][B]2. Which will cause the rate to increase the most?
A) doubling [A]
B) quadrupling [A]
C) tripling [B]
D) doubling [B]
E) lowering temperature Answer: C
3) The reaction A + B C + D is second order in A and zero order in B. The value of k is 0.012 M-1 min-1. What is the rate of this reaction when [A] = 0.125 M and [B] = 0.435 M?
A) 3.4 × 10-3 M min-1 B) 1.3 M min-1 C) 1.5 × 10-3 M min-1 D) 1.9 × 10-4 M min-1 E) 5 × 10-4 M min-1 Answer: D
4) Data for the reaction A + B C are given below. Find the rate constant for this system.
Experiment [A], M [B], M Initial rate, M/s
1 0.030 0.060 2.5 × 10-5
2 0.030 0.020 2.5 × 10-5
3 0.060 0.060 10.0 × 10-5
A) 2.8 × 10-2 M2s-1 B) 1.7 × 10-3 M-1s-1 C) 2.8 × 10-2 Ms-1 D) 2.8 × 10-2 M-1s-1
E) 1.7 × 10-3 Ms-1 Answer: D
5) In the first order, reaction A products, [A] = 0.400 M initially and 0.250 M after 15.0 min, what will [A] be after 175 min?
A) 1.04 × 10-3 M B) 2.31 × 10-1 M C) 1.67 × 10-3 M D) 3.70 × 10-2 M E) 6.024 × 10-3 M Answer: C
6) For the reaction A products, the following data are obtained:
[A] = 1.512 M, t = 0 min [A] = 1.490 M, t = 1.0 min [A] = 1.469 M, t = 2.0 min
What is the rate constant, k, for the reaction?
A) 1.4 × 10-2 M-1 min-1 B) 2.2 × 10-2 M-1 min-1 C) 9.7 × 10-3 M-1 min-1 D) 1.0 × 10-2 M-1 min-1 E) 3.6 × 10-3 M-1 min-1 Answer: C
7) A variable that has NO effect on reaction rate is:
A) energy of activation B) concentration C) catalyst D) temperature
E) none of these Answer: E
8) What is the rate constant at 305 K for the reaction:
2N2O5 2N2O4 + O2,
if k = 3.46 × 10-5 s-1 at 298 K and Ea = 106 kJ/mol?
A) 2.4 × 10-5 s-1 B) 1.2 × 10-5 s-1 C) 4.8 × 10-5 s-1 D) 9.2 × 10-5 s-1 E) 6.0 × 10-5 s-1 Answer: D
9) For the reaction: 2N2O5(g) 4NO2(g) + O2(g) the rate law is:
[O2]
t =k[N2O5]
At 300 K, the half-life is 2.50 × 104 seconds and the activation energy is 103.3 kJ/mol O2. What is the halflife at 310 K?
A) 6.57 × 103 s B) 2.49 × 104 s C) 9.51 × 106 s D) 1.87× 10-1 s E) 9.51 × 104 s Answer: A
10) What is the rate law for the following reaction and mechanism?
2HgCl2 + C2O42- 2Cl- + 2CO2 + Hg2Cl2 (overall reaction)
HgCl2 + C2O42- HgCl2C2O42- (F)
HgCl2C2O42- + C2O42- Hg + 2Cl- + CO2 + C2O4CO22- (S)
Hg + HgCl2 HgCl2 (F)
C2O4CO22- C2O42- + CO2 (F)
A) Rate = k[HgCl2][C2O42-]
B) Rate = k[HgCl2]2[C2O42-]
C) Rate = k[HgCl2]2[C2O42-]2 D)Rate = k[HgCl2]
E) Rate = k[HgCl2][C2O42-]2 Answer: E
11)The first order reaction A products has t1/2 = 150 sec. What percent of the sample remains unreacted after 300 sec?
A) 100% B) 50% C) 0.0% D) 25% E) 12.5%
Answer: D
12) If the half-life of a reaction depends on the concentration of the reactant, then the reaction cannot be ________
order.
A) third B) zero C) second D) first
E) none of these Answer: D
13) The rate constant for a first-order reaction is k = 0.00073 s-1. Determine the percent of reactant that has decomposed after 500 s.
A) 69% B) 43% C) 31% D) 57% E) 37%
Answer: C
14)For which of the following reactions does Kp = Kc?
A)3Fe(s) + 4H2O(g) Fe3O4(s) + 4H2(g) B)C(s) + H2O(g) CO(g) + H2(g)
C)H2(g) + I2(s) 2HI(g) D)2SO2(g) + O2(g) 2SO3(g)
Answer: A
15) Given the following:
I) N2O(g) + 1/2 O2(g) 2NO(g) Kc = 1.7 × 10-13 II) N2(g) + O2(g) 2NO(g) Kc = 4.1 × 10-31
Find the value of the equilibrium constant for the following equilibrium reaction:
N2(g) + 1/2 O2(g) N2O(g)
A) 2.6 × 10-22 B) 2.4 × 10-18 C) 1.6 × 10-9 D) 4.2 × 1017 E) 7.0 × 10-44 Answer: B
16)Consider the following reaction.
C(s) + H2O(g) CO(g) + H2(g)
At equilibrium at a certain temperature, [H2O(g)] = 0.12 M, and [CO(g)] = [H2(g)] = 1.2 M. If suddenly these concentrations are increased by 0.50 M, which of the following is true?
A)Since Kc does not change, nothing happens. B) more products are formed
C)Kc = 4.66 D)more H2O(g) will be formed
Answer: B
17)For the reaction: 3 Fe(s) + 4 H2O(g) Fe3O4(s) + 4 H2(g) what is the effect on equilibrium of increasing temperature of an exothermic reaction?
A) The reaction shifts to the right.
B)The Kp is doubled.
C) The reaction shifts to the left.
D)The Kp is decreased.
E) There is no change.
Answer: C, D
18)For the reaction; N2(g) + 3 H2(g) 2 NH3(g), the equilibrium amount of NH3 will be increased by:
I. increaseing the pressure II. adding H2 III. removing N2 IV. decreasing the pressure
A) III only B) II, III C) I, II D) I, III E) II, IV
Answer: C
19) For the following reaction O2(g) 2O(g)
what conditions favor production of oxygen atoms?
A) low temperature and high pressure B) high temperature and high pressure C) high temperature and low pressure D) low temperature and low pressure Answer: C
20) Consider the following equation:
N2O4(g) 2 NO2(g) Kc = 5.8 × 10-3
If the initial concentration of N2O4(g) = 0.040 M and the initial concentration of NO2(g) is 0 M, what is the equilibrium concentration of N2O4(g)?
A) 2.3 × 10-6 M B) 3.3 × 10-2 M C) 1.9 × 10-2 M D) 1.7 × 10-2 M E) 2.6 × 10-2 M Answer: B
21)For the reaction 2 NO(g) N2O4(g) Kp equals:
A)Kc(RT) B)RT/Kc C)Kc D)Kc/RT E) Kc(RT)2
Answer: D
22) Given the following reactions,
2PCl3(g) 2P(g) + 3Cl2(g) Kc = 0.0667 PCl3(g) + Cl2(g) PCl5(g) Kc = 4.0 calculate Kc for the reaction below.
2P(g) + 5Cl2(g) 2PCl5(g)
A) 23 B) 240 C) 1.1 D) 60
Answer: B
23)For a reaction, the reaction quotient, Qc > K, the reaction:
A) shifts to the left B) shifts to the right C) is exothermic D) is at equilibrium
E) is endothermic Answer: A
24) At a certain temperature, Kc = 0.0500 and H = +39.6 kJ for the reaction below.
2MgCl2(s) + O2(g) 2MgO(s) + 2Cl2(g) Calculate Kc for the reaction
MgO(s) + Cl2(g) MgCl2(s) + 1 2O2(g)
and indicate whether the value will be larger or smaller at a lower temperature.
A) 4.47, larger B) 0.224, smaller C) 0.224, larger D) 400, smaller Answer: A
25) For the reaction: 2 NO2(g) 2 NO(g) + O2(g), the partial pressure of O2(g) at equilibrium is 0.3500 atm. Ptotal = 1.0866 atm. What is Kp for this reaction?
A) 2.86 B) 128 C) 0.350 D) 182 E) 66.9
Answer: B
26) A mixture, containing 0.0750 M HCl(g) and 0.0330 M O2(g) is allowed to come to equilibrium at 480 °C.
4HCl(g) + O2(g) 2Cl2(g) + 2H2O(g)
At equilibrium [Cl2] = 0.030 M. What is the value of Kc?
A) 890 B) 0.13 C) 1.3 D) 480 E) 1.1 × 10-3
Answer: A
27) Which of the following is the strongest base?
A) Cl- B)H2O C) NO3- D) ClO4- E) F-
Answer: E
28) Choose the INCORRECT statement. The term pH:
A) = -log [H3O+]
B) = -ln [H+]
C) is more convenient than exponential notation D) refers to the "potential" of hydrogen ion
E) = 14 - pOH Answer: B
29) 0.272 g of a monoprotic solid acid (mw = 189 g/mol) is dissolved in water to produce 25.0 mL of a solution with pH = 4.93. Determine the ionization constant of the acid.
A) 2.8 × 10-7 B) 4.1 × 10-8 C) 2.4 × 10-9 D) 1.4 × 10-10 E) 2.1 × 10-4 Answer: C
30) For which of the following polyprotic acids is the first ionization step approximately 100%?
A)H2CO3 B)H2S C)H3PO4 D)H2SO3 E)H2SO4
Answer: E
31) What is the [HPO4-2] of a solution labeled "0.10 M Phosphoric Acid"?
[Ka1 = 7.1 × 10-3; Ka2 = 6.3 × 10-8; Ka3 = 4.2 × 10-13]
A) 1.6 × 10-9 B) 4.2 × 10-13 C) 1.6 × 10-16 D) 6.3 × 10-8 E) 7.1 × 10-3 Answer: D
32)The pH of a solution of NH4C2H3O2 is approximately 7. The best explanation is:
A) Aqueous ammonia and acetic acid have approximately equal ionization constants.
B) Ammonium acetate is a weak electrolyte.
C) The salt is a product of a strong acid and a strong base.
D) This salt does not react with water.
E) All salts of weak acids and weak bases are neutral.
Answer: A
33) Which species in the following reaction acts as a Lewis acid?
CuSO4(s) + 4NH3(aq) Cu(NH3)42+(aq) + SO42-(aq) A) Cu(NH3)42+
B) Cu2+
C) SO42- D)NH3
E) All are acids.
Answer: B
34) Consider the reaction:
HC2H3O2 + H2O H3O+ + C2H3O2-
Choose the pair of substances that are both bases in the reaction.
A) H2O and C2H3O2- B) HC2H3O2 and C2H3O2- C) HC2H3O2 and H3O+
D) H2O and H3O+
E) all are bases Answer: A
35)A saturated aqueous solution of calcium hydroxide is approximately 0.13% calcium hydroxide, by mass, and has a density of 1.02 g ml-1. What is the pH of such a solution?
A) 11.95 B) 12.25 C) 12.75 D) 13.00 E) 12.55
Answer: E
36) Hypochlorous acid (HOCl) has an ionization constant of 3.2 × 10-8. What is its percent ionization in 1.0 M and 0.10 M solutions, respectively?
A) 0.57% and 0.18%
B) 0.32% in both C) 0.032% and 0.0032%
D) 0.57% in both E) 0.018% and 0.057%
Answer: E
37)For the following compound, predict whether the solution is acidic, basic or neutral and why: NaC2H3O2.
A) basic because it is a weak base B) acidic because it is a strong acid C) neutral because there is no hydrolysis D) basic because it is the salt of a weak acid
E) acidic because it is the salt of a weak base Answer: D
38) What is the pH of a 0.052 M solution of sodium acetate? Ka = 1.8 × 10-5
A) 5.3 B) 10.0 C) 3.0 D) 8.7 E) 11.0
Answer: D
39) List the following acids in order of increasing strength:
HBrO HIO HClO
A) HIO < HClO < HBrO B) HBrO < HIO < HClO C) HClO < HIO < HBrO D) HClO< HBrO < HIO
E) HIO < HBrO < HClO Answer: E
40) Which indication of relative acid strengths is INCORRECT?
A) HCl > HF B)H2SO3 > HNO3 C)HClO2 > HClO
D)CH3CO2H > CH3CH2OH E)H2SO4 > H2SO3
Answer: B
