Cliffs AP Chemistry, 3rd Edition

7. For each reaction in #3 above, predict the potentials from the data obtained and found in
   Table 4 and compare it to the measured values found in Table 5.

Redox Rxn Predicted Voltages Measured Voltage

()aq+ ()aq

Cu ++Fe Cu Fe

()ss()

(^22) " + 0.99 + (−0.55) = 0.44 0.50
()aq+ ()aq
Pb++Mg Pb Mg
()ss()
(^22) " + 0.48 + 0.60 = 1.08 1.00
()aq+ ()aq
Cu ++Pb Cu Pb
()ss()
(^22) " + 0.99 + (−0.48) = 0.51 0.51

8. Using the Nernst equation, predict the expected voltage of the cell which contained the
   0.0100 M Cu2+(aq)solution and compare it to the actual voltage obtained.

()aq ()aq +

Zn Cu ++Zn Cu

()ss()

+^22 " E°= 1.00 V

.

[]

EE log.. log[ ]

n QV Cu

0 0592 100 Zn

2

0 0 0592

2

2

==-- +

+

== 100 ..VV-0 0592. 2 log0 0100.^1094

This compares favorably to the 1.01 V that was actually measured.

9. Using the data from the cell containing the unknown Ag+(aq)solution, calculate the Ksp
   of AgCl.

()aq ()aq +

Zn 22 Ag++Zn Ag

()ss()

+^22 " E°= 1.56V

+ + 2 e.

.

:

:.

..

ox Zn Zn E V

red Ag e Ag E V

EE E V V V

076

076

080

080 156

() ()

() ()

s aq ox

aq s red

ox red

"^2

"

=

=+ =

+=

++

• 
  

+-

%

%

%%%

..

[ ]

EE log log[]

n QE Ag

0 0592 Zn

2

0 0592

2

==^00 --^2

+

+

...

[]

log

Ag

091 156=-0 0592 2 1 + 2

]

.

]

.

[[

log

Ag Ag

(^11) ++ 22 ==21 959" 9 1 10# (^21) [Ag+] = 1.0 × 10 –11
KAgCl 1010 11010sp==[][].+-_ ###--^11 i ^h=.^11
The actual Kspfor AgCl is 1.56 × 10 –10at 25ºC.

10. From the data on the cell containing the Cu2+(aq)and NH3(aq)mixture, write the reaction and
    determine the formation constant, Kfand compare it to the accepted value for Kfof
    2 × 1013 M–4.

()aq ()aq +

Zn Cu ++Zn Cu

()ss()

+^22 " E = 0.56 V; E°= 1.10 V

In a 6.0 M NH 3 solution, most of the Cu2+(aq)will combine with NH 3 to form Cu(NH 3 ) 4 2+(aq)

as evidenced by the magnitude of Kf.

Cu^2 +]aqg+ 4 NH (^33) ]aqg?Cu NH^ h 42 +]aqg
Part III: AP Chemistry Laboratory Experiments