CHAP. 11: ELECTROCHEMISTRY [CONTENTS] 398
- With the electrolyte we note its molality or activity in brackets. This may be omitted if
it is unimportant in the given case. - For gas electrodes, the gas pressure or fugacity is given in brackets. For amalgam elec-
trodes, the composition of the amalgam is given in brackets. - A dash (—) is written between a gas electrode and its carrier.
- In the case of electrodes of the second type, the symbol (s) is written with the chemical
formula of undissolved salt, emphasizing that it is not salt in a solution.
Example
Describe the following galvanic cells:
a) Zn|ZnSO 4 (m 1 )||CuSO 4 (m 2 )|Cu⊕
b) Pt—H 2 (pst)|HCl(a±= 1)|AgCl(s)|Ag⊕Solution
a) The cell is formed by a zinc anode dipped into a solution of zinc sulfate of the molalitym 1.
This half-cell is separated by a salt bridge from another half-cell formed by a solution of copper
sulfate of the molalitym 2 into which a copper cathode is dipped.
b) The cell is formed by a hydrogen anode with platinum as its carrier. Hydrogen pressure equals
the standard pressure. The electrode is dipped into a solution of hydrochloric acid whose mean
activity equals one. A silver electrode covered with solid silver chloride is dipped into the same
electrolyte. This electrode is the cathode.11.8.3 Electrical work
For the electrical workWelwe have
Wel=−zFE , (11.108)wherezis the number of electrons exchanged during the reaction in the cell,F is the Faraday
constant, andEis the cell potential.
Note:Work is related to 1 mole of reaction turnovers, see8.1, and consequently depends
on the way the reaction is written.