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Exam 4B
Spring 2004

April 23, 2004


Possibly useful information:

Go = Ho – TSo

U = qw

w = –PV

Go = wmax

S = RlnW

 

Complex Ion

Kf (25 oC)

 

Cd(NH3)42+

1.3×104

 

Co(NH3)62+

1.3×105

 

Cu(NH3)42+

1.1×1013

 

Ni(NH3)62+

5.5×108

 

Zn(NH3)42+

4.1×108

 

 

Substance

Ho (kJ/mol)

So (J/mol•K)

Ba(OH)2(s)

–946.0

107

BaCl2(s)

–858.1

123.7

H2O(g)

–241.8

188.7

H2O(l)

–285.8

69.91

Cl(g)

–234

153.25

Cl(aq)

–167.2

56.5

K+(g)

514.197

154.47

K+(aq)

–252.4

102.5

KOH(s)

–424.8

78.87

KOH(aq)

–482.4

91.63

Na+(g)

609.839

147.85

Na+(aq)

–240.1

59.0

NaOH(s)

–425.6

64.48

NaOH(aq)

–469.2

48.1

 

Half–reaction

Eored (V)

Co3+(aq) + e Co2+(aq)

1.82

ClO3(aq) + 3 H2O(l) + 6 e Cl(aq) + 6 OH(aq)

0.622

Ni(OH)3(s) + e Ni(OH)2(s) + OH(aq)

0.48

Co(OH)3(s) + e Co(OH)2(s) + OH(aq)

0.17


1. Complete and balance the following reactions:

a. Sr(OH)2(s) + C6H5COOH(aq)

b. Co(NO3)3(aq) + Na2CO3(aq)

c. Ni2+(aq) + NH3(aq)

d. MnO4(aq) + HClO3(aq) Mn2+(aq) + HClO4(aq)

e. MnO4(aq) + Mg(s) MnO2(s) + Mg(OH)2(s)

2. Identify the oxidation number for:

a. As in H3AsO4

b. Fe in Fe2O3

3. Cu(OH)2 is a sparingly soluble salt. Determine if the solubility will increase, decrease, or stay the same in the following solutions. Briefly (15 words or less) explain your answer.

a. 1 M HCl solution.

b. 1 M Cu(NO3)2 solution.

c. 1 M NH3 solution.

4. Consider the reaction of solid barium chloride with aqueous potassium hydroxide solution.

a. Write the reaction.

b. Find Ho at 25 oC.

c. Find So at 25 oC.

d. Find Go at 25 oC.

5. Consider the cell:

Pt(s)|Co(OH)3(s)|Co(OH)2(s)| pH = 14 ||ClO3(aq)|Cl(aq)| pH = 14 |Pt(s)

a. Write the oxidation half–reaction.

b. Write the reduction half–reaction.

c. Write the net reaction.

d. Find the cell potential under standard conditions.