The Determination of Thermodynamic Functions

CHEM 457 - Experimental Physical Chemistry

Experiment 03

The Determination of Thermodynamic Functions of the Reactions in
a Commercial Alkaline-Manganese Dioxide Galvanic Cell
Student Name:____________________________ Date:______________ Score:_______/ 10 points
PLEASE SHOW ALL WORK FOR FULL CREDIT.
The standard electromotive force (emf) of the cell Pt(s) | H2(g) | HBr(aq) | AgBr(s) | Ag(s) was
measured over a range of temperatures, and the data were fitted to the following polynomial:

E 0 (V ) = 0.07131− 4.99x10 −4 (T (K ) − 298K ) − 3.45x10 −6 (T (K ) − 298K )2
1. Evaluate the standard reaction Gibbs energy (∆rG°) at 298 K. (2 points)

2. Predict the equilibrium constant, K, from the standard equilibrium constant for the cell
reaction Ag+(s) + ½ H2(g)
Ag(s) + H+(aq). (2 points)

3. Evaluate the standard reaction entropy (∆rS°) at 298 K. (2 points)

4. Evaluate the standard reaction enthalpy (∆rH°) at 298 K. (2 points)

5. What would be the measured voltage of Schematic A, if R = 1.6111V and M = 1.6021V?
(1 points)

6. The voltmeter, used in Experiment 3, cannot measure
voltages below 1 uV and displays 5 significant figures,
regardless of the voltage range measured. At room
temperature the voltage of battery R and M are 1.6111 V
and 1.6021 V, respectively. What is the advantage of
measuring the voltage as shown in Schematic A compared
to direct measurement of M? (1 points)

Schematic A