PRACTICE FINAL EXAM CHEMISTRY 152

This practice final represents the format and general types of questions that you should expect to see on the final

exam. Do not limit your studying to completing this final – you can also go back to old tests and “redo” them, redo

Mastering Chemistry assignments for practice, study from old quizzes, etc.

Good luck and may the electromotive force be with you! (I will be posting a key later on.)

1. Which of the following would have the most positive value for ∆S?

a) 3 NO (g) NO2 (g) + N2O (g) b) NH3 (g) NH3 (l)

c) 2 I (g) I2 (g) d) 2 CO2 (g) 2 CO (g) + O2 (g)

e) None of these reactions would have a positive ∆S.

2. A process will be spontaneous at all temperatures if

[a] the enthalpy change is − and the entropy change is +.

[b] the enthalpy change is + and the entropy change is +.

[c] the enthalpy change is − and the entropy change is − .

[d] the enthalpy change is + and the entropy change is −

[e] all reactions will be nonspontaneous at some temperature.

3. A reaction has the following thermodynamic data:

∆H value = -425 kJ/mol

∆S value = 78.5 J/molK

Which of the following is true for this reaction?

a) Both ∆H and ∆S favor the reaction's spontaneity.

b) Both ∆H and ∆S oppose the reaction's spontaneity.

c) ∆H favors the reaction, but ∆S opposes it.

d) ∆H opposes the reaction, but ∆S favors it.

e) The reaction cannot occur at room temperature.

4. For a given reaction, rxnG is large and negative. Which of the following statements is true?

[a] The reaction will not take place at all. [b] Reactants are favored at equilibrium.

[c] Products are favored at equilibrium. [d] The equilibrium constant, K, is small.

[e] All of these are true.

5. The following reaction is nonspontaneous at 25C.

CaCO3 (s) CaO (s) + CO2(g) H = 177.8 kJ

If S = 160.5 J/K, what is the lowest temperature at which the reaction will be spontaneous?

a) spontaneous at

all temperatures b) 1108 K c) spontaneous at

no temperature

d) 1.10 K e) 298 K

Consider the following reaction for the next three questions.

2 N2O5 (g) 4 NO2 (g) + O2 (g)

At 25C for this reaction, the following data are relevant.

Substance Hf S

N2O5 11.29 kJ/mol 355.3 J/Kmol

NO2 33.15 kJ/mol 239.9 J/Kmol

O2 -- 204.8 J/Kmol

6. What is ∆H for the reaction?

a) 110.02 kJ b) 21.86 kJ c) 21.86 kJ d) 155.20 kJ e) 155.20 kJ

7. What is ∆S for the reaction?

a) 89.5 J/K b) 249.2 J/K c) 453.8 J/K d) 249.2 J/K e) 115.6 J/K

8. What is ∆G for the reaction at 25C?

a) 135 kJ b) 98.7 kJ c) 25.2 kJ d) 11.2 kJ e) 0 kJ

9 . For the reaction BrO3- + 5Br

-+ 6H

+ 3Br2 + 3H2O at a particular time, [BrO3

-]/t = − 1.5 10

-2 M/s. What is

[Br-]/t at the same instant?

A. - 13 M/s B. - 330 M/s C. - 1.5 10-2

M/s D. - 3.0 10-3

M/s

E. - 7.5 10-2

M/s

10. Nitric oxide gas (NO) reacts with chlorine gas according to the equation

NO + ½Cl2 NOCl.

The following initial rates of reaction have been measured for the given reagent concentrations.

Which of the following is the rate law (rate equation) for this reaction?

a. rate = k[NO]

b. rate = k[NO][Cl2]1/2

c. rate = k[NO][Cl2]

d. rate = k[NO]2[Cl2]

e. rate = k[NO]2[Cl2]

2

11. For the reaction X + Y Z, the reaction rate is found to depend only upon the

concentration of X. A plot of 1/X verses time gives a straight line.

Keeping in mind what this graph tells you about the order of reaction, what is the rate law for this reaction?

A. rate = k [X]

B. rate = k [X][Y]

C. rate = k [X]2

D. rate = k [X]2[Y]

12. What information can be obtained directly or calculated from graphs of the integrated rate laws?(time vs 1/[X],

time vs ln[X], etc)

A. The rate constant from the slope of the line.

B. The initial concentration from the y intercept

C. The order of the reaction (0 order, vs 1st order vs 2

nd order)

D. All of the above

13. The rate law for the reaction H2O2 + 2H+ + 2I

- I2 + 2H2O is rate = k[H2O2][I

-]. The following mechanism has

been suggested.

Identify all intermediates included in this mechanism.

a. H+ and I

-

b. H+ and HOI

c. HOI and OH-

d. H+ only

e. H2O and OH-

14. The rate law for the reaction 2NO2 + O3 N2O5 + O2 is rate = k[NO2][O3]. Which one of the following

mechanisms is consistent with this rate law?

a.

b.

c.

d.

(note: The answer for a is found above a. The answer for b is found above b. . .etc)

15. The activation energy of a reaction may be lowered by,

[a] increasing the concentration of the reactants

[b] increasing the temperature

[c] adding a catalyst

[d] answers b and c are both correct

[e] answers a, b, and c are all correct.

16. Consider the following reaction:

COCl2 CO + Cl2 K = 2.2 10–10

How does the equilibrium concentration of the reactant compare to the equilibrium concentrations of the

products?

[a] It (the reactant) is much smaller.

[b] It (the reactant) is much larger.

[c] They (reactants and products) are about the same.

[d] They (reactants and products) have to be exactly equal.

[e] Impossible to determine from the given information.

17. At 700K, the reaction,

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

has an equilibrium constant, Kc = 4.3 104

, and the following concentrations are present:

[SO2] = 10.0 M [O2] = 10.0 M [SO3] = 0.10 M

Is the mixture at equilibrium?

[a] Yes, the mixture is at equilibrium.

[b] No, the reaction will proceed in the forward direction (toward products).

[c] No, the reaction will proceed in the reverse direction (toward reactants).

[d] Impossible to determine without additional information.

18. For the following reaction at equilibrium, which choice gives a change that will shift the position of equilibrium

to favor formation of more products?

2NOBr(g) 2NO(g) + Br2(g), Hºrxn = 30 kJ/mol

A. Increase the total pressure by decreasing the volume.

B. Add more NO.

C. Remove Br2.

D. Lower the temperature.

E. Remove NOBr.

19 At 600C, Kp = 1.25 X 102 for the endothermic reaction:

A + B C + D

The temperature is decreased to 300C. What happens to the value of the equilibrium constant, K?

[a] K increases [b] K remains the same [c] K decreases

[d] impossible to determine without additional information.

20. At 400C, Kc = 250 for the equilibrium:

A2(g) + B2(g) 2AB(g)

If 1.00 mol A2 and 1.00 mol B2 are introduced into an empty 4.00 L container, find the equilibrium

concentration of AB at 400C.

[a] 0.03 M [b] 0.44 M [c] 1.76 M [d] 4.8 M [e] 5.8 M

A2(g) + B2(g) 2AB(g)

I 0.25 0.25 0

C -x -x +2x

E 0.25-x 0.25-x 2x

250 = (2x)2

15.81 = 2x 3.95 – 15.81x = 2x 3.95 = 17.81x x = .22M 2x = 0.44M

(0.25-x)2 .25-x

21. The pH of a 1.0 M HCl solution is:

[a] 0.00 [b] 1.00 [c] 1.00 [d] 7.00 [e] 14.00

22. What is the hydroxide ion concentration, OH−, in a solution having a pH of 3.62?

[a] 2.6 1011

M [b] 4.2 1011

M [c] 3.8 104

M [d] 3.8 104

M [e] 5.1 1010

M

23. Which of the following solutions will be the least basic?

[a] 0.10 M NaOH [b] 0.10 M Ba(OH)2 [c] 0.10 M HF

[d] 0.10 M HCl [e] 0.10 M NH3

24. Which of the following statements is true regarding a 0.10 M weak base solution, A−?

[a] [OH−] > [A

] [b] [OH

−] = [HA] [c] [OH

−] = [A

]

[d] pH = 13.00 [e] [H3O+] = [OH

]

25. Consider the weak acid, HA (Ka = 1.0 10

5). What is the percent ionization of a 0.250 M solution of this

weak acid?

[a] 0.63% [b] 0.0063 % [c] 1.0 104

% [d] 15.8% [e] 0.14%

26. Which aqueous solution is expected to be basic?

[a] NaCl [b] NaF [c] KCN [d] NH4Cl

[e] none of these will be basic [f] both b and c are basic

27. The Ka values for several acids are given below. Which acid has the weakest conjugate base?

[a] Ka = 3.2 108

[b] Ka = 5.6 1010

[c] Ka = 1.8 105

[d] Ka = 4.2 107

[e] Ka = 1.3 102

28. Which of the following mixtures would produce an effective buffer solution?

a) 1.0 M H2SO4 / 1.0 M NaHSO4

b) 1.0 M H2 SO3 / 1.0 M Na2SO3

c) 1.0 M Na2SO3/ 1.0 M NaHSO3

d) 1.0 M HNO2 / 1.0 M NaF

e) 1.0 M HNO3 / 1.0 M NaNO3

29. A buffer solution is prepared that is 0.78 M NaHCO3 and 0.14 M Na2CO3. What is the pH of the solution?

[Ka(HCO3−) = 5.6 10

11]

[a] 3.94 [b] 4.50 [c] 9.50 [d] 10.99 [e] 9.31

30. What is the net ionic equation for the reaction between HNO3 and KOH?

[a] HNO3 + KOH KNO3 + H2O

[b] K+ + NO3

KNO3

[c] H+ + NO3

+ K

+ + OH

K

+ + NO3

+ H2O

[d] H+ + OH

H2O

31. A solution of 0.100 M HA, is titrated with 0.100 M NaOH. What indicator would be the best choice to detect

the equivalence point of this titration? [Ka(HA) = 4.3 X 10-6

]

[a] methyl red (pKa = 5.00) [b] bromthymol blue (pKa = 7.30)

[c] phenolphtalein (pKa = 8.7) [d] thymol blue (pKa = 9.20)

[e] alizarin yellow (pKa = 10.2)

32. Which is the relationship between Ksp and molar solubility, x, for PbI2?

[a] Ksp = x2 [b] Ksp = 4x

3 [c] Ksp = 27x

4 [d] Ksp = 108x

5 [e] None of these

33. The solubility of MgCO3 is 1.8 10-4

mol/L. What is Ksp for this compond?

[a] 1.8 10-4

[b] 3.6 10-4

[c] 1.3 10-7

[d] 3.2 10-8

[e] 2.8 10-14

34. The Ksp value for PbCl2 is 2.4 10

-4. What is the molar solubility of PbCl2?

[a] 2.4 10-4

M [b] 6.2 10-2

M [c] 7.7 10-3

M [d] 3.9 10-2

M [e] 6.0 10-5

M

35. Will a precipitate of PbI2 form, when 500 mL of 0.0025M Pb(NO3)2 is added to 400 mL to 0.0035 M NaBr?

[Ksp(PbBr2) = 8.7 X 10-9

]

[a] Yes, Q < Ksp [b] No, Q > Ksp [c] Yes, Q > Ksp [d] No, Q < Ksp

[e] Impossible to determine without additional information.

36. The oxidation state of iodine in HIO4 is:

[a] –1 [b] +1 [c] +5 [d] +7

37. The cellE for a particular electrochemical reaction was found to be cellE = −1.38 V. This value of cellE

means that this reaction is

[a] spontaneous and ∆G° is negative. [b] nonspontaneous and ∆G° is positive.

[c] in an equilibrium state and ∆G° is zero. [d] spontaneous and ∆G° is positive.

[e] endothermic and ∆H° is positive.

38. In a particular galvanic (voltaic) cell, the spontaneous reaction that occurs is:

Zn(s) + Cu2+

(aq) Cu(s) + Zn2+

(aq)

Consider the following three statements and choose the correct answer.

(I) The copper metal is the negative electrode (anode).

(II) A salt bridge will be unnecessary in this spontaneous cell.

(III) The electrons flow from the Zn electrode to the Cu electrode

[a] only I is true [b] only III is true

[c] II and III are true, I is false [d] I and III are true, II is false

[e] I, II, and III are all true

39. Balance the following equation in acidic solution. When balanced with the smallest set of whole number

coefficients, the coefficient of NO3 is:

Cu(s) + NO3 − (aq) → Cu2+

(aq) + NO(g)

[a] 5 [b] 4 [c] 3 [d] 2 [e] 1

3(Cu → Cu2+

+ 2 e−)

2( 3e− + 4 H

+ + NO3

− → NO + 2 H2O)

6e- + 3 Cu + 8 H

+ + 2 NO3

− → 3 Cu

2+ + 2 NO + 4 H2O+ 6e

−

Subtract out the 6e− on both sides.

40. Given the following standard reduction potentials:

Fe2+

(aq) + 2e Fe(s) red

E = 0.45 V

Ag+(aq) + e

Ag(s) red

E = +0.80 V

determine the standard cell potential, cellE , of the following redox reaction and state if the reaction is spontaneous

or not.

Fe2+

(aq) + Ag(s) Ag+(aq) + Fe(s)

[a] 0.35V, not spontaneous (reactant favored) [b] 1.25 V, not spontaneous (reactant favored)

[c] +0.35 V, spontaneous (product favored) [d] +1.25, spontaneous (product favored)

[e] Impossible to determine with information provided.

41. Which of these species will act as a Lewis acid (more than one choice may be correct)?

A. NH3

B. NH4+

C. H2O

D. BF3 E. F

-