MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

1052-2nd Chem Exam-1060517(A)

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

Please use this titration curve to answer the following two questions.

Indicator pKa

methyl orange 3.46

methyl red 5.00

bromocresol purple 6.12 bromthymol blue 7.10

thymol blue 8.90

phenolpthalein 9.10

1)

A 25.0 mL sample of a solution of a monoprotic acid is titrated with a 0.115 M NaOH solution. The titration curve above was obtained. Which of the following indicators would be best for this titration?

A)

bromocresol purple

B)

bromthymol blue

C)

phenolpthalein

D)

methyl red

E)

thymol blue

Answer: B

2)

A 25.0 mL sample of a solution of a monoprotic acid is titrated with a 0.115 M NaOH solution. The titration curve above was obtained. The concentration of the monoprotic acid is about ________ mol/L.

A)

0.115

B)

25.0

C)

0.100

D)

0.0600

E)

0.240

Answer: A

3)

Which one of the following pairs cannot be mixed together to form a buffer solution?

A)

C5H5N, C5H5NHCl

B)

NaClO, HNO3

C)

NH2CH3, HCl

D)

HC2H3O2, NaOH (C2H3O2- = acetate)

E)

KOH, HI

Answer: E

4)

What change will be caused by addition of a small amount of HCl to a solution containing fluoride ions and hydrogen fluoride?

A)

The concentration of hydronium ions will increase significantly.

B)

The concentration of fluoride ions will increase as will the concentration of hydronium ions.

C)

The concentration of fluoride ion will decrease and the concentration of hydrogen fluoride will increase.

D)

The fluoride ions will precipitate out of solution as its acid salt.

E)

The concentration of hydrogen fluoride will decrease and the concentration of fluoride ions will increase.

Answer: C

5)

Of the following solutions, which has the greatest buffering capacity?

A)

0.087 M NH3 and 0.088 M NH4Cl

B)

0.234 M NH3 and 0.100 M NH4Cl

C)

0.100 M NH3 and 0.455 M NH4Cl

D)

0.543 M NH3 and 0.555 M NH4Cl

E)

They are all buffer solutions and would all have the same capacity.

Answer: D

6)

Which below best describe(s) the behavior of an amphoteric hydroxide in water?

A)

With conc. aq. NaOH, its clear solution forms a precipitate.

B)

With conc. aq. NaOH, its suspension dissolves.

C)

With both conc. aq. NaOH and conc. aq. HCl, its suspension dissolves.

D)

With conc. aq. HCl, its suspension dissolves.

E)

With conc. aq. HCl, its clear solution forms a precipitate.

Answer: C

7)

A 25.0 mL sample of 0.723 M HClO4 is titrated with a 0.273 M KOH solution. The H3O+ concentration after the addition of 0.00 mL of KOH is ________ M.

A)

0.0181

B)

0.430

C)

0.273

D)

0.723

E)

none of the above

Answer: D

Please use this table to answer the following four questions.

Name Formula Ksp

Cadmium carbonate CdCO3 5.2 × 10-12 Cadmium hydroxide Cd(OH)2 2.5 × 10-14 Calcium fluoride CaF2 3.9 × 10-11 Silver iodide AgI 8.3 × 10-17 Zinc carbonate ZnCO3 1.4 × 10-11

8)

Which compound listed below has the greatest molar solubility in water?

A)

_CaF2

B)

_CdCO3

C)

_ZnCO3

D)

_Cd(OH)2

E)

AgI

Answer: A

9)

Which compound listed below has the smallest molar solubility in water?

A)

AgI

B)

_Cd(OH)2

C)

_CaF2

D)

_ZnCO3

E)

_CdCO3

Answer: A

10)

What is the concentration of iodide ions in a saturated solution of silver iodide?

A)

9.1 × 10-9

B)

1.4 × 10-8

C)

3.0 × 10-10

D)

3.8 × 10-11

E)

3.5 × 10-9

Answer: A

11)

In which of the following aqueous solutions would you expect AgI to have the highest solubility?

A)

0.050 M BaI2

B)

0.050 M KI

C)

0.010 M AgNO3

D)

pure water

E)

0.050 M NaI

Answer: D

12)

The pH of a solution that contains 0.800 M acetic acid (Ka = 1.76 × 10-5) and 0.172 M sodium acetate is ________.

A)

8.578

B)

9.913

C)

5.422

D)

8.370

E)

4.087

Answer: E

13)

A solution of NaF is added dropwise to a solution that is 0.0122 M in Ba2+. When the concentration of F- exceeds ________ M, BaF2 will precipitate. Neglect volume changes. For BaF2, Ksp = 1.7 × 10-6.

A)

1.2 × 10-2

B)

7.0 × 10-5

C)

2.1 × 10-8

D)

3.0 × 10-3

E)

1.4 × 10-4

Answer: A

14)

The Kb of ammonia is 1.76 × 10-5. The pH of a buffer prepared by combining 50.0 mL of 1.00 M ammonia and 45.0 mL of 1.00 M ammonium nitrate is ________.

A)

9.291

B)

4.632

C)

9.372

D)

4.742

E)

none of the above

Answer: A

15)

According to the Arrhenius concept, an acid is a substance that ________.

A)

tastes bitter

B)

is capable of accepting one or more H+

C)

causes an increase in the concentration of H+ in aqueous solutions

D)

reacts with the solvent to form the cation formed by autoionization of that solvent

E)

can accept a pair of electrons to form a coordinate covalent bond

Answer: C

16)

A Br nsted-Lowry acid is defined as a substance that ________.

A)

acts as a proton acceptor

B)

acts as a proton donor

C)

decreases [H+] when placed in H2O

D)

increases Ka when placed in H2O

E)

increases [OH-] when placed in H2O

Answer: B

17)

Using the data in the table, which of the conjugate bases below is the strongest base?

Acid Ka

HOAc 1.8 × 10-5 HC7H5O2 6.3 × 10-5 HNO2 4.5 × 10-4

HF 6.8 × 10-4

A)

OAc-

B)

F-

C)

_C7H5O2-

D)

_NO2-

E)

OAc- and C7H5O2-

Answer: A

18)

Which solution will be the most basic?

A)

_{0.10 M H2O}

B)

0.10 M CH3OH

C)

0.10 M KOH

D)

0.10 M Ba(OH)2

E)

All solutions have equal basicity.

Answer: D

19)

Which of the following ions will act as a weak base in water?

A)

Cl-

B)

ClO-

C)

_NO3-

D)

OH-

E)

None of the above will act as a weak base in water.

Answer: B

20)

Of the compounds below, a 0.1 M aqueous solution of ________ will have the highest pH.

A)

NaClO, Ka of HClO = 3.2 × 10-8

B)

KCN, Ka of HCN = 4.0 × 10-10

C)

NaHS, Kb of HS- = 1.8 × 10-7

D)

NH4NO3, Kb of NH3 = 1.8 × 10-5

E)

NaOAc, Ka of HOAc = 1.8 × 10-5

Answer: B

21)

Calculate the concentration (in M) of hydronium ions in a solution at 25.0 °C with a pOH of 4.223.

A)

5.98 × 10-5

B)

1.00 × 10-7

C)

1.67 × 104

D)

5.99 × 10-19

E)

1.67 × 10-10

Answer: E

22)

The conjugate base of H2PO4- is ________.

A)

_H2PO4

B)

_HPO42-

C)

_PO43-

D)

_H3PO4

E)

none of the above

Answer: B

23)

Ka for HCN is 4.9 × 10-10. What is the pH of a 0.068 M aqueous solution of sodium cyanide?

A)

2.96

B)

11.07

C)

13.24

D)

0.74

E)

7.00

Answer: B

24)

The Ka of hypochlorous acid (HClO) is 3.00 × 10-8. What is the pH at 25.0 °C of an aqueous solution that is 0.0200 M in HClO?

A)

-9.22

B)

+4.61

C)

-2.45

D)

+2.45

E)

+9.22

Answer: B

25)

The pH of a 0.55 M aqueous solution ammonia, NH3, at 25.0 °C is 11.50. What is the value of Kb for NH3?

A)

6.0 × 10-5

B)

1.1 × 10-9

C)

1.8 × 10-5

D)

2.0 × 10-9

E)

none of the above

Answer: C

26)

The acid-dissociation constants of phosphoric acid (H3PO4) are Ka1 = 7.5 × 10-3, Ka2 = 6.2 × 10-8, and Ka3 = 4.2 × 10-13 at 25.0 °C. What is the pH of a 2.5 M aqueous solution of phosphoric acid?

A)

0.86

B)

0.13

C)

1.82

D)

2.51

E)

0.40

27)

A reaction that is spontaneous as written ________.

A)

is very rapid

B)

is also spontaneous in the reverse direction

C)

will proceed without outside intervention

D)

is very slow

E)

has an equilibrium position that lies far to the left

Answer: C

28)

Which of the following statements is true?

A)

Processes that are spontaneous in one direction are spontaneous in the opposite direction.

B)

Spontaneity can depend on the temperature.

C)

Processes are spontaneous because they occur at an observable rate.

D)

All of the statements are true.

Answer: B

29)

Which one of the following processes produces a decrease of the entropy of the system?

A)

boiling of alcohol

B)

explosion of nitroglycerine

C)

sublimation of naphthalene

D)

dissolving sodium chloride in water

E)

dissolving oxygen in water

Answer: E

30)

Given the following table of thermodynamic data, Substance Hf° (kJ/mol) S° (J/mol · K)

TiCl4 (g) -763.2 354.9

TiCl4 (l) -804.2 221.9

complete the following sentence. The vaporization of TiCl4 is ________.

A)

nonspontaneous at all temperatures

B)

spontaneous at all temperatures

C)

spontaneous at low temperature and nonspontaneous at high temperature

D)

nonspontaneous at low temperature and spontaneous at high temperature

E)

not enough information given to draw a conclusion

Answer: D

31)

S is positive for the reaction ________.

A)

2SO3 (g) 2SO2 (g) + O2 (g)

B)

Ag+ (aq) + Cl- (aq) AgCl (s)

C)

_{H2O (l) H2O (s)}

D)

CaO (s) + CO2 (g) CaCO3 (s)

E)

N2 (g) + 3H2 (g) 2NH3 (g)

Answer: A

32)

For an isothermal process, the entropy change of the surroundings is given by the equation:

A)

S = -qsys / T

B)

_{S = qsys T}

C)

S = q lnT

D)

S = -q lnT

E)

S = -qsys T

Answer: A

33)

A reaction that is not spontaneous at low temperature can become spontaneous at high temperature if H is ________ and S is ________.

A)

+, +

B)

-, -

C)

+, -

D)

-, +

E)

+, 0

Answer: A

34)

The standard Gibbs free energy of formation of ________ is zero.

(a) H2O (l) (b) Fe (s) (c) I2 (s)

A)

(a) only

B)

(b) only

C)

(c) only

D)

(b) and (c)

E)

(a), (b), and (c)

Answer: D

35)

Consider the reaction:

NH3 (g) + HCl (g) NH4Cl (s)

Given the following table of thermodynamic data at 298 K:

Substance Hf° (kJ/mol) S° ( J/K · mol)

NH3 (g) -46.19 192.5

HCl (g) -92.30 186.69

NH4Cl (s) -314.4 94.6 The value of K for the reaction at 25 °C is ________.

A)

1.4 × 108

B)

150

C)

1.1 × 10-16

D)

8.4 × 104

E)

9.3 × 1015

Answer: E

36)

Which one of the following processes produces a decrease in the entropy of the system?

A)

dissolution of LiOH(s) in water

B)

freezing of Fe(l) into Fe(s)

C)

melting ice to form water

D)

mixing of two gases into one container

E)

evaporation of liquid ethanol into gaseous ethanol

Answer: B

37)

For a given reaction, H = +22.2 kJ/mol and S = +81.1 J/K-mol. The reaction is spontaneous ________.

Assume that H and S do not vary with temperature.

A)

at all temperatures

B)

T < 250 K

C)

250 K < T < 274 K

D)

274 K < T

Answer: D

Use the table below to answer the questions that follow.

Thermodynamic Quantities for Selected Substances at 298.15 K (25 °C) Substance H°f (kJ/mol) G°f (kJ/mol) S (J/K-mol)

Oxygen

O2 (g) 0 0 205.0

H2O (l) -285.83 -237.13 69.91

Sulfur

S (s, rhombic) 0 0 31.88

SO2(g) -269.9 -300.4 248.5

SO3(g) -395.2 -370.4 256.2

38)

The value of S° for the decomposition of gaseous sulfur trioxide to solid elemental sulfur and gaseous oxygen, 2SO3 (g) 2S (s, rhombic) + 3O2 (g)

is ________ J/K · mol.

A)

+166.4

B)

+19.3

C)

-19.3

D)

+493.1

E)

-493.1

Answer: A

39)

The value of H° for the decomposition of gaseous sulfur dioxide to solid elemental sulfur and gaseous oxygen,

SO2 (g) S (s,rhombic) + O2 (g) is ________ kJ/mol.

A)

+269.9

B)

0.0

C)

-269.9

D)

+135.0

E)

-135.90

Answer: A

40)

What is the equilibrium constant Keq for the oxidation of solid elemental sulfur to gaseous sulfur dioxide?

S (s, rhombic) + O2(g) SO2 (g)

A)

4.54 x 1052

B)

1.129

C)

0.886

D)

2.20 x 10-53

E)

-300.4

Answer: A