1012_2nd Exam_1020417
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1) Choose the INCORRECT statement.
A)
The common ion in a mixture of a weak acid and a strong acid is the hydronium ion.
B)
A weak acid-strong base will produce a longer vertical section of a titration curve than will a strong acid-strong base.
C)
For an accurate titration, the end point needs to match the equivalence point.
D)
The pH of a buffer solution changes only slightly with addition of a small amount of acid or base.
E)
The pH of a buffer depends mainly on the
pKaof the weak acid component of the buffer.
Answer: B
2) How will addition of sodium chloride affect the pH of a HCl solution?
A) It will lower the pH.
B) It will raise the pH.
C) The solution becomes hotter.
D) The pH cannot be measured.
E) The pH will not change.
Answer: E
3) How will addition of sodium acetate to an acetic acid solution affect the pH?
A) The pH will not change.
B) The solution becomes hotter.
C) The pH cannot be measured.
D) It will lower the pH.
E) It will raise the pH.
Answer: E
4) A solution containing equimolar amounts of a weak acid with Ka= 10-5and its sodium salt has:
A) pH dependent on concentration ratios B) pH < 7
C) pH = 7
D) pH dependent on the nature of the acid anion E) pH > 7
Answer: B
5) What is the buffer range (for an effective 2.0 pH unit) for a benzoic acid/sodium benzoate buffer? [Ka for benzoic acid is 6.3 × 10-5]
A) 4.7 - 6.7 B) 7.4 - 9.4 C) 5.3 - 7.3 D) 8.8 - 10.8 E) 3.2 - 5.2
Answer: E
6) What factor governs the selection of an indicator for a neutralization titration?
A) the final volume of the solution B) the molarity of the standard solution
C) the pH at the stoichiometric (equivalence) point D) the volume of titrant
7) Phenol red indicator changes from yellow to red in the pH range from 6.6 to 8.0. State what color the indicator will assume in the following solution: 0.10 M HC2H3O2( Ka=1.8 × 10-5).
A) yellow
B) red-yellow mixture C) red
D) The indicator is its original color.
E) There is not enough information to answer this question.
Answer: A
8) In the titration of 50.0 mL of 0.0200 M C6H5COOH(aq) with 0.100 M NaOH(aq), what is/are the major species in the solution after the addition of 5.0 mL of NaOH(aq)?
A) C6H5COO- and Na+ B) C6H5COOH, OH-, and Na+ C) C6H5COOH, C6H5COO-, and Na+ D) C6H5COOH
E) H3O+ and OH- Answer: C
9) Determine the [F-] of the solution with initial concentrations: [HF] = 1.296 M, [NaF] = 1.045 M. ( Ka for HF is 6.6 × 10-4)
A) 2.344 M B) 0.251 M C) 1.046 M D) 5.3 × 10-4M E) 8.2 × 10-4M
Answer: C
10) 25 mL of 0.10 M HCl is titrated with 0.10 M NaOH. What is the pH at equivalence?
A) 7.0 B) 6.2 C) 7.5 D) 7.1 E) 8.6
Answer: A
11) 1.80 grams of an impure mixture containing Na2CO3 required 84.0 ml of 0.125 M H2SO4 for complete neutralization. What percent of the mixture is Na2CO3?
A) 120% B) 1.1% C) 62% D) 57% E) 31%
Answer: C
12) What is the pH of a 1.0 M solution of Na2CO3? ( For H2CO3: Ka1= 4.4 × 10-7, Ka2= 4.7 × 10-11)
A) 12.2 B) 2.5 C) 5.8 D) 7.0 E) 10.3
Answer: A
13) Examine the titration curve shown below. Which of the following titrations could it represent?
A) titrating HCl by NaOH B) titrating Ca(OH)2 by HCl C) titrating HCl by NH3 D) titrating H2SO4by NaOH
E) titrating NH3 by HCl Answer: B
Information for following three questions:
7.500 g of a weak acid HA ( Ka= 2.5 × 10-5) is added to distilled water to produce 500.0 mL of solution with [H3O+] = 1.92 × 10-3.
14) What is the initial concentration of the HA?
A) 0.150 M B) 0.500 M C) 0.250 M D) 0.100 M E) 0.040 M.
Answer: A
15) What is the molar mass of this weak acid?
A) 75 g/mol B) 750 g/mol C) 100 g/mol D) 252 g/mol E) 64 g/mold.
Answer: C
16) What is the freezing point of the solution ( density of the solution is 1.00 g/mL )? ( Kf for H2O is 1.86 °C/m)
A) - 0.283 °C B) - 0.142 °C C) 0 °C D) 0.25 °C E) 100 °C
Answer: A
17) What is the Ksp expression for magnesium phosphate, Mg3(PO4)2? A) Ksp= [Mg2+]2[PO43-]3
B) Ksp= [Mg2+][PO43-] C) Ksp= [Mg2+]3[PO43-] D) Ksp= [Mg2+]3[PO43-]2
E) Ksp= [Mg2+]3[PO43-]2/[Mg3(PO4)2] Answer: D
18) Which of the following has the largest molar solubility?
A) Mg(OH)2, Ksp = 2 × 10-11 B) Fe(OH)3, Ksp = 4 × 10-38 C) BaSO4, Ksp = 1.1 × 10-10 D) Cr(OH)2, Ksp = 6.3 × 10-11
E) AgCl, Ksp = 1.6 × 10-10 Answer: D
19) A solution contains [Ba2+] = 5.0 × 10-5 M, [Ag+] = 3.0 × 10-5 M, and [Zn2+] = 2.0 × 10-7 M. Sodium oxalate is slowly added so that [C2O42-] increases.
Salt BaC2O4 ZnC2O4 Ag2C2O4 Ksp1.5 × 10-8 1.35 × 10-9 1.1 × 10-11
What is the concentration of the first cation to precipitate when the second cation just begins to precipitate?
A) 1.1 × 10-11 B) 1.35 × 10-9 C) 5.0 × 10-5 D) 1.3 × 10-6 E) 2.2 × 10-6 Answer: E
20) Choose the compound that is LESS SOLUBLE in an acidic solution than in pure water.
A) FeS B) C6H5COOH C) Mg(CO3)2 D) KCl E) Ca(OH)2
Answer: B
21) Choose the compound that is most soluble in water.
A) HgS B) ZnS C) PbS D) SnS E) K2S
Answer: E
22) In a qualitative cation analysis, the unknown ion is not precipitated by HCl, H2S, or CO32-. A flame test produced a violet flame. The unknown ion is ________.
A) Fe2+ B) Pb2+ C) NH4+ D) K+ E) Ag+
Answer: D
Information for following three questions:
AgCl(s) Ag+(aq) + Cl-(aq) Ksp = 1.8 ×10-10 ( at 25 °C ) Ag+(aq) + 2 NH3(aq) [Ag(HN3)2+](aq) Kf = 1.6.×107 ( at 25 °C )
23) What is the molar solubility of AgCl in pure water at 25 °C?
A) 3.2×10-7 M B) 1.1×10-9 M C) 1.8×10-10 M D) 5.2×10-2 M E) 1.3×10-5 M Answer: E
24) What is the molar solubility of AgCl in 1.0×10-3M AgNO3 at 25 °C?
A) 1.8×10-7 M B) 5.2×10-6 M C) 6.6×10-3 M D) 1.3×10-5 M E) 1.8×10-10 M Answer: A
25) What is the molar solubility of AgCl in 0.100 M NH3 25 °C?
A) 2.0×10-8 M B) 4.9×10-3M C) 1.8×10-5 M D) 5.0×10-6 M E) 3.3×10-7 M Answer: B
26) Choose the INCORRECT statement.
A) A zero G means the system is at equilibrium.
B) A spontaneous reaction is one that must have a negative value of H.
C) If a process is spontaneous, the reverse process is nonspontaneous.
D) Entropy is related to the way in which the energy of a system is distributed among the available microscopic energy levels.
E) A nonspontaneous reaction can be made to occur by coupling it with a spontaneous reaction to form an overall spontaneous reaction.
Answer: B
27) Which of the following has the highest entropy?
A) 1 mole of liquid water at 30 °C B) 1 mole of ice at -10 °C
C) 1 mole of water vapor at 100 °C D) 1 mole of water vapor at 30 °C
E) 1 mole of water at 10 °C Answer: C
28) Which of the following substances under equal conditions and in the same phase has the greatest molar entropy?
A) NO B) N2O4 C) N2O3 D) NO2 E) N2O5
Answer: E
29) Order the following by increasing entropy.
CO(g), COCl2(g), CO2(g), CaO(s) A) CO2 < CO < CaO < COCl2
B) CaO < CO < CO2 < COCl2 C) CO < CaO < COCl2 < CO2 D) CO2 < CaO < COCl2 < CO E) COCl2 < CO < CaO < CO2 Answer: B
30) A chemical reaction such as the following:
2NH3(g) N2(g)+ 3H2(g) H° = 92.22 kJ This means the reaction:
A) will be spontaneous at low temperature B) is spontaneous at all temperatures C) is not spontaneous at any temperature D) will be spontaneous at high temperature Answer: D
31) Consider the reaction: 3 N2(g)+ 2 O3(g) 6 NO(g)
Hf° 0.00 142.26 90.37 kJ/mol S° 191.5 237.7 210.6 J/mol K What is G°rxn for this reaction in kJ at 500 K?
A) -1.00 × 105 kJ B) 93 kJ
C) 151 kJ D) 441 kJ
32) Consider the reaction at 25 °C:
AgI(s) Ag
+
(aq) + I (aq)Gf° -66.19 77.11 -51.57 kJ/mol What is Ksp for AgI at 25 °C? ( R = 8.3145 J mol-1 K-1 )
A) 3.2 × 10-12 B) 4.7 × 103 C) 8.5 × 10-17 D) 0.96 E) 1.2 × 1016 Answer: C
33) If the enthalpy of vaporization of chloromethane, CH3Cl, is 21.5 kJ/mol at the normal boiling point, 249 K, calculate S°vap.
A) 86.3 J mol-1 K-1 B) 896 J mol-1 K-1 C) 5.35 J mol-1 K-1 D) 11.6 J mol-1 K-1 E) 252. J mol-1 K-1 Answer: A
34) Which of the following statements must be true for the entropy of a pure solid to be zero?
I. The temperature must be 0 K.
II. The solid must be crystalline, not amorphous.
III. The solid must be perfectly ordered.
IV. The solid must be an element.
A) I and II B) I C) I, II, III, and IV D) I, II, and III
Answer: D
35) Calculate S° for the formation of one mole of solid sodium bromide from the elements at 25°C.
Species S°, J/(K · mol) NaBr (s) 86.8
Na (s) 51.3
Br2 (l) 152.2
A) -116.7 J/K B) 86.8 J/K C) -40.6 J/K D) -81.2 J/K
Answer: C
36) Which of the following is zero at 25 °C?
A) G°f for H2O(l) B) S° for H2O(l) C) S° for N2(g) D) G°f for N2(g)
Answer: D
37) For the reaction N2O4(g) 2NO2(g), H°f= +57.2 kJ/mol and Kp= 0.113 at 25 °C. Estimate the Kp at 56 °C. ( R = 8.3145 J mol-1 K-1 )
A) 2.35 × 10-6 B) 1.00 C) 6.57 × 105 D) 0.415
Answer: B
38) In figure (1) below oxygen molecules, represented by unshaded spheres, and chlorine molecules, represented by shaded spheres, are in separate compartments. Figure (2) shows the equilibrium state of the system after the stopcock separating the two compartments is opened. Assuming the oxygen and the chlorine behave as ideal gases, what are the signs (+, -, or 0) of H, S, and G for this process?
A) H = 0, S = +, G = - B) H = -, S = +, G = -
C) H = +, S = -, G = + D) H = 0, S = -, G = +
Answer: A
Information for following two questions:
39) According to the diagram, the forward reaction is
A) spontaneous at d, at equilibrium at e, and nonspontaneous at f.
B) nonspontaneous at d, at equilibrium at e, and spontaneous at f.
C) nonspontaneous at d and e, and spontaneous at f.
D) spontaneous at d, e, and f.
Answer: A
40) According to the diagram,
A) G° is positive and the equilibrium composition is rich in reactants.
B) G° is negative and the equilibrium composition is rich in products.
C) G° is negative and the equilibrium composition is rich is reactants.
