quiz 6 skeleton

8/12/2019 Quiz 6 Skeleton

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Christian RuizCHEM102

Possible Quiz 6 (Chapters 15 & 16) Questions

1.

In the titration of hydrofluoric acid (HF) with sodium hydroxide (NaOH) the resulting

2.56 millimoles of conjugate base and 16.2 millimoles of acid gave a pH of 2.34. Find the

K a of hydrofluoric acid.

a. 7.2 x 10 -4

b. 1.4 x 10-3

c. 1.8 x 10-5

d. 6.23 x 10-8

2. Identify the pH of the equivalence point in the titration of 0.1 M NH 3 with 0.1 M HCl.

a. pH < 7

b. pH = 7

c. pH > 7

3. Which of the following will form a buffer solution when equal amounts are mixed with

water?

a. HNO 3 and NaNO 3

b. NaOH and NaCl

c. CH 3COOH and CH 3COONa

d. H2SO 4 and NH 3


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4. Which equation represents the Henderson-Hasselbach equation for the pH of a basic

buffer?

a. pH = pK a + log(

b. pH = 14 - pK b + log(

c. pH = pK b + log(

d. pH = 14 - pK b + log(

5. Which expression represents the K sp of Ba(IO 3)2?

a. K sp = [Ba 2+]2[IO 3-]

b. K sp = [Ba 2+][IO 3-]2

c. K sp = [Ba 2+][IO 3-]

d. K sp = [Ba 2+]2[IO 3-]2

6. What is the pH of a solution when 20 mL of 0.1 M H 2SO 4 is titrated with 10 mL of 0.05

M KOH?

a. 2.43

b. 1.48

c. 1.23

d. 8.68


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7. How many mL of 0.03 M HCl is needed to titrate 64.5 mL of 0.004 M NaOH?

a. 8.6 mL

b. 9.3 mL

c. 10.4 mL

d. 2.3 mL

8. Identify the pH of the equivalence point in the titration of 0.1 M H 3PO 4 with 0.1 M

Ba(OH) 2.

a.

pH < 7 b. pH = 7

c. pH > 7

9. At which point in the titration of a weak acid with a strong base will the pH = pKa of the

acid?

a. the equivalence point

b. 1/3 the equivalence point

c. half the equivalence point

d. the equivalence point

10. Given that the equilibrium Al(OH) 3 ( s) Al 3+ (aq ) + 3OH - (aq ) has K sp = 1.9 x 10 -33 and

[Al 3+] = 9.2 x 10 -12 , find the [OH -]

a. 2.1 x 10 -22

b. 5.9 x 10 -8

c. 2.4

d. 9.1 x 10 -30


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11. For the equilibrium reaction shown below, which change will result in a spontaneous

forward reaction?

2SO 2 ( g ) + O 2 ( g ) 2SO 3 ( g )

a. Adding SO 3

b. Removing O 2

c. Adding SO 2

d. Adding a catalyst

12. Which of the following is/are false?

I.

Entropy increases as a substance changes state from liquid to solid.

II. A nonspontaneous forward reaction requires an input of free energy.

III. Adding a catalyst will disrupt the spontaneity of an equilibrium reaction.

a. I and II

b. II and III

c. I and III

d. I only

e. II only

13. Which of the following does not describe a substance at its thermodynamic standard

state?

a. 1 M concentration

b. 10 atm pressure

c. 25C

d. 1 atm pressure


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14. Calculate the standard free energy of formation ( G f ) for water in the following reactionat 25C, given that G for the reaction is -14.41 kJ/mol, G f for C 2H4 is 68.1 kJ/mol,and G f for CH 3CH 2OH is -174.9 kJ/mol:

C2H4 ( g )+ H 2O ( g ) CH 3CH 2OH ( g )

a. -228.6 kJ/mol

b. -390 kJ/mol

c. 209.9 kJ/mol

d. 51.3 kJ/mol

15. For which process is S positive in the system? a. H2O ( g ) H2O ( s)

b. 2H 2 ( g ) + O 2 ( g ) 2H 2O ( g )

c. MgCl 2 ( s) Mg 2+ (aq ) + Cl - (aq )

d. C4H10 ( g ) C4H10 (l )

16. What does the sign of a positive G , the standard free energy change, imply?

a. The equilibrium concentrations predominate mainly as reactants.

b. The equilibrium concentrations predominate mainly as products.

c. The equilibrium concentrations are approximately equal regarding the reactants

and products.

17. Calculate the standard entropy change for the formation of water, 2H 2 ( g ) + O 2 ( g )

2H2O ( l ), given S for H 2O is 69.9 J K -1 mol -1, S for H 2 is 130.6 J K

-1 mol -1, and S for

O2 is 205.0 J K -1 mol -1.

a. -400.5 J J K -1 mol -1

b. -326.4 J K -1 mol -1

c. -88.9 J K -1 mol -1

d. -325.8 J K -1 mol -1


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18. Which phrase(s) do(es) not describe a system at a low temperature?

I. The system is at a low entropy level.

II. The system has a high degree of molecular randomness.

III. The molecules in the system have a low degree of molecular motion.

IV. The molecules in the system have a high degree of intermolecular bonding.

a. I only

b. II only

c. III only

d.

I, III, and IVe. II and IV

19. True or false: Endothermic reactions are always nonspontaneous.

a. True

b. False

20. According to the second law of thermodynamics:

a. The total enthalpy of a system and its surroundings always increases in a

spontaneous reaction.

b. The total entropy of a system and its surroundings always decreases in a


c. The total entropy of a system and its surroundings always increases in a


d. The total entropy of a system and its surroundings always increases in a

nonspontaneous reaction.

quiz 6 skeleton

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