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R-16
B.
Based on your results from the measured cell potentials in the above Table, draw a graph of E
ox
versus log[Ag
+
] for Part I. Use graph paper with a 1.0 mm grid and be sure to label your graph
clearly. Attach this graph to your Report. (1.0 marks)
C.
On your graph for Part IB, calculate the slope of the line. (0.2 marks)
Nernst equation suggests the (theoretical) slope of the line should be (0.1 mark)
.
Part II. The Determination of an Equilibrium Constant
1.
The equilibrium constant for the following reaction:
2 Ag
+
(aq)
+ Cu
(s)
Cu
2+
(aq)
+ 2 Ag
(s)
can be found experimentally by finding the E
cell
values for a series of cells in which the [Cu
2+
] is
kept constant and the concentration of Ag
+
(aq)
varies. By plotting a graph of
E
cell
versus log [Ag
+
], the concentration of Ag
+
(aq)
required to give E
cell
= 0.000 V can be
determined from the x-axis intercept. When E
cell
= 0.000 V then the system is at equilibrium.
a)
Draw a graph of E
cell
versus log[Ag
+
] for Part II. Note that your log [Ag
+
] values can be
obtained from the Table for Part I. Use graph paper with a 1.0 mm grid and be sure to label
your graph clearly.
NOTE: Use an appropriate x-axis scale so that the x-intercept can be obtained.
Attach this graph to your Report. (1.0 marks)
b)
From your graph (Part II), what is the experimental value for log [Ag
+
] when
E
cell
=0.000 V? _________
What is [Ag
+
] at this point? _____________ (0.2 marks)
c)
Calculate an experimental K
eq
for this reaction using the experimentally determined [Ag
+
] above.
(Hint: Simply write the equilibrium expression for this reaction and substitute with the
appropriate concentrations.) (0.5 marks)
