MULTIPLE CHOICE: 60 points.  Questions 1-20 are multiplle choice, worth 3 points each.  On your scantron sheet mark  the letter corresponding to the one correct answer.

1)  What are the BrMnsted-Lowry bases in the following chemical reaction

C5H5N(aq) + H2O(l)  C5H5NH+(aq) + OH-(aq)?

A) C5H5N, OH-

B) C5H5N, H2O, OH-

C) C5H5N, H2O

D) C5H5N, C5H5NH+

 

2)  Which is the net ionic equation for the neutralization reaction of a strong acid with a weak base?

A) H3O+(aq) + NH3(aq)  NH4+(aq) + H2O(l)

B) HCl(aq) + NaOH(aq)  H2O(l) + NaCl(aq)  

C) HCl(aq) + NH3(aq)  NH4Cl(aq)  

D) H3O+(aq) + OH-(aq)  2 H2O(l)

 

3)  What is the conjugate base of the Bronsted-Lowry acid HPO42-?

A) H3PO4

B) PO43-

C) HPO42-

D) H2PO4-

 

4)  A solution with a hydrogen ion concentration of 3.25 x 10-2 M is ________ and has a hydroxide concentration of ________.

A) acidic, 3.08 x 10-13 M

B) basic, 3.08 x 10-13 M

C) acidic, 3.08 x  10-12 M

D) basic, 3.08 x 10-12 M

 

5)  Which statement about buffers is true?

A) A buffer does not change pH on addition of a strong acid or strong base.

B) Buffers consist of a strong acid and its conjugate base.

C) Buffers resist change in pH upon addition of small amounts of strong acid or strong base.

D) Buffers have a pH = 7.

 

6)  What is the [CH3CO2-]/[CH3CO2H] ratio necessary to make a buffer solution with a pH of 4.44? Ka = 1.8 x 10-5 for CH3CO2H.

A) 0.94:1

B) 0.50:1

C) 1.1:1

D) 2.0:1

 

7)  What is the solubility product constant, Ksp, for the slightly soluble salt Fe(OH)2? The equation of interest is Fe(OH)2(s) +H2O(l) = Fe2+(aq) + 2 OH-(aq)

A) Ksp = 1/{[Fe2+][OH-]2}

B) Ksp = [Fe2+][OH-]2

C) Ksp = {[Fe2+][OH-]2}/{[Fe(OH)2][H2O]}

D) Ksp = {[Fe2+][OH-]2}/[Fe(OH)2]  

 

8)  Calculate the pH for an aqueous solution of acetic acid that contains 2.15 x 10-3 M hydronium ion.

A) 2.67

B) 2.15x 10-3

C) 11.33

D) 4.65 x 10-12

 

9)  What is the strongest acid of the following?

A) HOCl

B) HOBr

C) HOI

D) All are equivalent.

 

10)  Ammonia NH3, has a base dissociation constant of 1.8 x 10-5. What is the conjugate acid of ammonia and what is its acid dissociation constant?

A) NH4+, 1.9 x 109

B) NH2-, 5.6 x 10-10

C) NH4+, 5.6 x 10-10

D) NH4+, 1.8 x 10-5

 

11)  BF3 and NH3 undergo a Lewis acid-base reaction forming an adduct. Which picture below correctly represents the curved arrow notation for the initial Lewis acid-Lewis base interaction in this reaction; what is the Lewis acid and the Lewis base?

 

               

  

A) Picture (4) is correct; BF3 is the Lewis acid and NH3 is the Lewis base.

B) Picture (1) is correct; NH3 is the Lewis acid and BF3 is the Lewis base.

C) Picture (3) is correct; NH3 is the Lewis acid and BF3 is the Lewis base.

D) Picture (2) is correct; BF3 is the Lewis acid and NH3 is the Lewis base.

 

The following plot shows two titration curves, each representing the titration of 50.00 mL of 0.100 M acid with 0.100 M NaOH.

 

 

12)  Which point a-d represents the equivalence point for the titration of a strong acid?

A) point a

B) point b

C) point c

D) point d

 

13)  Which point a-d represents a buffer region?

A) point a

B) point b

C) point c

D) point d

 

14)  Which of the following is a nonspontaneous process?

A) N2 (g) + 3 H2 (g) ® 2 NH3 (g) if P(H2) = P(N2) = 1 atm, P(NH3)­ = 0, and Kp = 4 x 105

B) the expansion of a gas into a vacuum

C) 2 NH3 (g) ® N2 (g) + 3 H2 (g) if P(NH3) = 1 atm, P(H2) = P(N2) = 0  Kp = 2 x 10-6

D) none of the above

 

15)  Sodium reacts violently with water according to the equation:

2 Na(s) + 2 H2O(l) ® 2 NaOH(aq) + H2(g)

The resulting solution has a higher temperature than the water prior to the addition of sodium. What are the signs of DHo  and DSo for this reaction?

A) DHo  is negative and DSo is negative.

B) DHo  is positive and DSo is negative.

C) DHo  is negative and DSo is positive.

D) DHo  is positive and DSo is positive.

 

16)  What is W in Boltzmann's formula, S = k ln W?

A) a fraction indicating the probability of obtaining a result

B) the work times Avogadro's number

C) the number of ways of obtaining the state

D) a random number

 

17)  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, II, III, and IV

B) I

C) I and II

D) I, II, and III

 

18)  Which of the following gas molecules has the greatest standard molar entropy at 25oC?

A) CH3CH3

B) CH2CH2

C) C2H2

D) All have the same entropy.

 

19)  Which should have the highest standard molar entropy at 25eC?  

A) Al(s)

B) Al(g)

C) Al(l)

D) All three should have a standard molar entropy of zero.

 

20)  Which statement is true about the formation of CaCO3(s) from CaO(s) and CO2(g) at 1.00 atm?

CaO(s) + CO2(g) ® CaCO3(s)             DHo  = -178.7 kJ and DSo = -150.4 J/K

A) The reaction is spontaneous at all temperatures.

B) The reaction is spontaneous at low temperatures.

C) The reaction is spontaneous at high temperatures.

D) The reaction is not spontaneous at any temperature.

 

PROBLEMS. In the questions below you must show all of your work clearly to receive full credit.

21)  (10) Methylamine, CH3NH2, is a weak base with Kb =3.7 x 10-4. 

 

a) Write the equation for the reaction that occurs when methylamine is dissolved in water.

 

 

 

b)  What is the pH of a 0.250 M aqueous solution of methylamine?

 

 

 

 

 

 

 

 

 

 

 

 

22)  (10) Consider the tiration of 50.0 mL of 0.200 M formic acid, HCO2H,

 (Ka = 1.8 x 10-4) with 0.250 M NaOH.

 

a)  Calculate the pH after the addition of 10.0 mL of the NaOH solution.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

b)  Is the pH at the equivalence point greater than 7, equal to 7 or less than 7?  Explain your answer, and include the relevant chemical equation in your explanation.

 

 

 

 

 

 

 

 

 

 

 

 

23)  (10) Consider the reaction:   2 SO2(g)  + O2(g)    2 SO3(g) and the data below.

Substance             DGfo, kJ/mol at 25oC

SO2(g)                     -300.2

SO3(g)                    -371.1

O2(g)                       0.00

 

a) What is the standard free energy change, DGo for this reaction?

 

 

 

b) Is the reaction spontaneous under standard-state conditions at 25oC?  Please explain.

 

 

 

 

 

 

 

 

 

c)  What is DG if the partial pressures are:  100 atm SO3, 0.10 atm O2 and 0.10 atm SO2

 

 

 

 

 

 

 

 

 

 

 

24)  (10) Will a precipitate of PbCl2 form on mixing equal volumes of 0.010 M Pb(NO3)2 and 0.010 M HCl?  The Ksp of PbCl2 is 1.2 x 10-5?


 

MULTIPLE CHOICE: 60 points.  Questions 1-20 are multiplle choice, worth 3 points each.  On your scantron sheet mark  the letter corresponding to the one correct answer.

1)  A

 

2)  A

 

3)  B

 

4)  A

 

5)  C

 

6)  B

 

7)  B

 

8)  A

 

9)  A

 

10)  C

 

11)  D

 

12)  D

 

13)  A

 

14)  D

 

15)  C

 

16)  C

 

17)  D

 

18)  A

 

19)  B

 

20)  B

 

PROBLEMS. In the questions below you must show all of your work clearly to receive full credit.

21) 

 

22) 

 

23) 

 

24)