1082-1st Chem Exam(C)-1090408
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1) Which one of the following is the least soluble in water?
A) CH3CH2CH2CH2CH2OH B) CH3OH
C) CH3CH2OH D) CH3CH2CH2OH
E) CH3CH2CH2CH2OH Answer: A
2) Which one of the following substances is more likely to dissolve in benzene (C6H6)?
A) HBr B) NaCl C) CH3CH2OH D) NH3
E) CCl4 Answer: E
3) When solutions of strong electrolytes in water are formed, the ions are surrounded by water molecules.
These interactions are described as a case of . A) dehydration
B) saturation C) crystallization D) hydration
E) supersaturation Answer: D
4) The greatest gas solubility in water is predicted under what conditions?
A) low temperature, low partial pressure B) low temperature, high partial pressure C) high temperature, high partial pressure D) high temperature, low partial pressure
E) Solubility of gases cannot be predicted.
Answer: B
5) Which of the following concentration unit is temperature dependent?
A) mass percent B) molarity C) mole fraction D) molality
E) none of the above.
Answer: B
6) A 4.55 L sample of water contains 0.115 g of sodium ions. Determine the concentration of sodium ions in ppm if the density of the solution is 1.00 g/mL.
A) 25.3 ppm B) 13.2 ppm C) 36.5 ppm D) 52.3 ppm E) 12.7 ppm
Answer: A
7) Commercial grade HCl solutions are typically 39.0% (by mass) HCl in water. Determine the molarity of the HCl, if the solution has a density of 1.20 g/mL. (HCl = 36.46 g/mol)
A) 12.8 M B) 7.79 M C) 13.9 M D) 10.7 M E) 9.35 M
Answer: A
8) The dissolution of water in octane (C8H18) is principally prevented by . A) dipole-dipole attraction between octane molecules
B) hydrogen bonding between water molecules C) London dispersion forces between octane molecules D) ion-dipole attraction between water and octane molecules
E) repulsion between like-charged water and octane molecules Answer: B
9) A solution is formed at room temperature by vigorously dissolving enough of the solid solute so that some solid remains at the bottom of the solution. Which statement below is true?
A) The solution is considered unsaturated.
B) The solution is considered saturated.
C) The solution is considered supersaturated.
Answer: B
10) Soap has an ionic and a polar end. It works well to remove oil by
A) surrounding the oil with the polar end, and the water interacts with the nonpolar end.
B) surrounding the oil with the nonpolar end, and the water interacts with the polar end.
C) surrounding the oil and water with the polar end.
D) surrounding the oil and water with the nonpolar end.
Answer: B
11) A solution contains 11% by mass of sodium chloride. This means that . A) the density of the solution is 11 g/mL
B) 100 mL of the solution contains 11 g of sodium chloride C) there are 11 g of sodium chloride in 1.0 mL of this solution D) the molality of the solution is 11
E) 100 g of the solution contains 11 g of sodium chloride Answer: E
12) A 0.200 m solution of which one of the following solutes will have the lowest vapor pressure?
A) glucose B) AlCl3 C) KCl D) LiCl E) CaCl2
Answer: B
13) A 0.100 L solution is made by dissolving 0.441 g of CaCl2 in water and the measured osmotic pressure of this solution is 2.56 atm at 27 °C. What is the actual van’t Hoff factor, i, for the solute in this solution? (R = 0.0821 L-atm/mol-K; CaCl2 = 110 g/mol)
A) 2.62 B) 3 C) 1.98 D) 1 E) 0.38
Answer: A
14) An unknown compound is composed of 65.46% C, 5.47% H, and 29.07% O. A sample weighing 5.34 g dissolved in 60.00 g H2O, lowers the freezing point to -0.600°C. What is the molecular formula of the compound? (Kf for water = 1.86°C/m; C = 12.0, O = 16.0, H = 1.0 g/mol).
A) C3H3O B) C15H15O5 C) C5H10O D) C9H9O3 E) C10H20O2
Answer: B
15) Based on the following energy profile, predict which of following statement is correct? (kf: forward reaction rate constant, kr: reverse reaction rate constant, Kc: equilibrium constant.)
A) kf = kr and Kc = 1 B) kf > kr and Kc > 1 C) kf > kr and Kc < 1 D) kf < kr and Kc < 1 E) kf < kr and Kc > 1 Answer: B
16) For which of the following values of Kc will the equilibrium mixture consist almost entirely of reactants?
A) 1.00 B) 1 × 10-10 C) 0.030 D) 30 E) 4 × 108
Answer: B
17) A chemical equilibrium has been established for the following system:
Co(H2O)62+(aq) + 4 Cl—(aq) ⇌ CoCl42—(aq) + 6H2O(l) (pink) (blue)
What the system will undergo if hydrochloric acid is added?
A) The equilibrium will shift to the left.
B) The equilibrium constant will be increased.
C) It should become more blue.
D) More Co(H2O)62+ will be produced.
E) It should become more pink.
Answer: C
18) For which of the following reactions does Kp = Kc?
A) 2SO2(g) + O2(g) ⇌ 2SO3(g)
B) 3Fe(s) + 4H2O(g) ⇌ Fe3O4(s) + 4H2(g) C) C(s) + H2O(g) ⇌ CO(g) + H2(g)
D) 2 Cl2(g) + 2 H2O(g) ⇌ 4 HCl(g) + O2(g) E) H2(g) + I2(s) ⇌ 2HI(g)
Answer: B
19) Which one of the following will change the value of an equilibrium constant?
A) varying the initial concentrations of products B) changing temperature
C) varying the initial concentrations of reactants D) changing the volume of the reaction vessel
E) adding other substances that do not react with any of the species involved in the equilibrium Answer: B
20) 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 equilibrium constant (Kc) for the following equilibrium reaction:
N2(g) + 1/2 O2(g) ⇌ N2O(g)
A) 7.0 × 10-44 B) 2.6 × 10-22 C) 1.6 × 10-9 D) 4.2 × 1017 E) 2.4 × 10-18 Answer: E
21) The process of dissolving CaSO4 in water is known to be exothermic:
CaSO4(s) ⇌ Ca2+(aq) + SO42-(aq)
If the temperature of the solution is decreased, CaSO4 becomes:
A) Less soluble B) More soluble
C) No change in solubility occurs Answer: B
22) A mixture is prepared with [CO] = 0.035, [Cl2] = 0.015, and [COCl2] = 0.95. It is known that Kc for the equilibrium CO (g) + Cl2 (g) ⇌ COCl2 (g) is 1.2 × 103 at 400°C. Predict what will happen.
A) The reaction occurs in the reverse direction.
B) The reaction occurs in the forward direction.
C) The reaction is at equilibrium so no net reaction occurs.
Answer: A
23) A mixture of 1.374 g of H2 and 70.31 g of Br2 is heated in a 2.00 L vessel at 700 K. These substances react according to H2(g) + Br2(g) ⇌ 2HBr(g). At equilibrium, the vessel is found to contain 0.566 g of H2. What is the equilibrium constant (Kc) for this reaction? (MW: H2 = 2.0159; Br2 = 159.81)
A) 146 B) 3.32 x 10-3 C) 0.261 D) 58.5 E) 6.67
Answer: D
24) Write the equilibrium constant (Kc) expression for the reaction:
3 Sn(s) + 4 HNO3(aq) + H2O(l) ⇌ 3 H2SnO3(s) + 4 NO(g) A) Kc = [H2SnO3]3[NO]4
[Sn]3[HNO3]4[H2O]
B) Kc = [NO]4 [HNO3]4
C) Kc = [H2SnO3]3[NO]4 [Sn]3[HNO3]4 D) Kc = [H2SnO3][NO]
[Sn][H2O][HNO3]
E) Kc = [H2SnO3]3[NO]4 [HNO3]4 Answer: B
25) For the reaction: C2H4Br2 + 3 KI → C2H4 + 2 KBr + KI3
At the time when C2H4Br2 is being consumed at a rate of 2.0 × 10-5 M/s, what is the rate at which KBr is being formed?
A) 1.0 × 10-5 B) 4.0 × 10-5 C) 2.0 × 10-5 D) 0.67 × 10-5 E) 5.0 × 10-6 Answer: B
26) On which factor the rate constant of a reaction does not depend upon?
A) the presence or absence of a catalyst B) the nature of reactant and product C) the temperature
D) the concentration of reactant and product E) the activation energy
Answer: D
Information of following two questions:
The data of following two questions in the table below were obtained for the reaction:
A + B → C
Experiment
Number [A] (M) [B] (M) Initial Rate (M/s)
1 0.451 0.885 1.13
2 0.451 1.77 1.13
3 1.35 0.885 10.17
27) The rate law for this reaction is rate = .
A) k[B] B) k[A]2 C) k[A][B] D) k[A]2[B]2 E) k[A]2[B]
Answer: B
28) The magnitude of the rate constant (M–1s–1) is .
A) 13.2 B) 42.0 C) 5.56 D) 2.21 E) 0.278
Answer: C
29) Which of the following represents the integrated rate law for a zeroth-order reaction (reaction type: A → product) ?
A) 1[A]t = kt + 1 [A]o B) [A]t = - kt + [A]o C) ln[A]t = - kt + ln[A]o D) lnk2
k1 = Ea R 1
T1 - 1 T2 E) k = Ae(-Ea/RT) Answer: B
30) The rate constant of a first-order process that has a half-life of 3.50 min is s-1.
A) 0.198 B) 1.65 × 10-2 C) 0.693 D) 3.30 ×10-3 E) 1.98
Answer: D
31) If the reaction 2HI → H2 + I2 is second order, which of the following will yield a linear plot?
A) 1/[HI] vs time B) log [HI] vs time C) ln [HI] vs time D) [HI] vs time
E) [HI]2 vs time Answer: A
32) The second-order decomposition of HI has a rate constant of 1.80 x 10-3 M-1s-1. How much HI remains after 27.3 s if the initial concentration of HI is 4.78 M?
A) 4.55 M B) 3.87 M C) 0.258 M D) 2.20 M E) 2.39 M
Answer: B
Information of following three questions:
The following mechanism has been proposed for (CH3)3AuPH3 decomposes into C2H6 and (CH3)AuPH3:
Step 1 : (CH3)3 AuPH3 k1
k-1⇌ (CH3)3 Au + PH3 (fast) Step 2 : (CH3)3 Au k2
→ C2H6 + (CH3)Au (slow) Step 3 : (CH3)Au + PH3 k3
→ (CH3) Au PH3 (fast) 33) What is the overall reaction?
A) CH3)Au → C2H6 + (CH3)AuPH3 B) (CH3)3AuPH3 → (CH3)3Au + PH3 C) (CH3)3AuPH3 → C2H6 + (CH3)AuPH3 D) (CH3)3Au → C2H6 + (CH3)Au
E) (CH3)2AuPH3 → C2H6 + AuPH3 Answer: C
34) How many intermediates were presented in the mechanisms?
A) 5 B) 2 C) 3 D) 4 E) 1
Answer: C
35) What is the rate law predicted by this mechanism?
A) rate = k[C2H6][AuPH3]
B) rate = k[(CH3)AuPH3]
[C2H6]
C) rate = k[AuPH3]
[C2H6]
D) rate = k[(CH3)3AuPH3]
[PH3]
E) rate = k[(CH3)3AuPH3][PH3]
Answer: D
36) Which of the following is not an example of a dynamic equilibrium? (assume that the situation doesn't change with time)
A) a supersaturated solution B) solid solute in saturated solution
C) solute gas and liquid solvent in a closed container D) liquid and vapor at the normal boiling point
E) liquid and vapor in a closed container Answer: A
37) At elevated temperatures, methyl isonitrile (CH3NC) isomerizes to acetonitrile (CH3CN):
CH3NC (g) → CH3CN (g)
The reaction is first order in methylisonitrile. The attached graph shows data for the reaction obtained at 198.9 °C.
What is the rate constant (s-1) for the reaction at 198.9 °C?
A) +6.2 B) +5.2 × 10-5 C) -1.9 × 104 D) +1.9 × 104 E) -5.2 × 10-5
Answer: B
38) The rate of the reaction CH3COOC2H5(aq) + OH-(aq) → CH3COO-(aq) + C2H5OH(aq) was measured at several temperatures, and the experimental data and pretreated data are as follows:
What is the energy of activation (kJ/mol) for this reaction? (R = 8.3145 J/K-mol)
A) 8.4 × 123 B) 46.8 C) 4.3 × 103 D) 5.63 E) 0.178
Answer: B
39) A reaction is found to have an activation energy of 38.0 kJ/mol. If the rate constant for this reaction is 1.60 × 102 M-1s-1 at 249 K, what is the rate constant at 349 K? (R = 8.3145 J/K-mol)
A) 4.20 × 105 M-1s-1 B) 7.94 × 104 M-1s-1 C) 1.26 × 103 M-1s-1 D) 2.38 × 105 M-1s-1 E) 3.08 × 104 M-1s-1 Answer: E
40) Assume both the forward and reverse are elementary step in the reaction:
N2O4(g) kf
kr⇌ 2 NO2(g)
Which of the following variables are equal when the reaction reaches equilibrium?
A) kf and kr
B) [N2O4] and [NO2]2
C) the forward reaction rate and reverse reaction rate D) [N2O4] and [NO2]
E) kf2 and kr Answer: C
