Chemistry

Redox and Electrochemistry
This section should be fresh in your minds because we just did this section
in the text. Closely related to electrochemistry is redox chemistry. Count on
at least one question on this on the test. Make sure you can:
• balance redox reactions in both acidic and basic medium
• identify substance being oxidized and reduced, oxidizing agents and
reducing agents
• galvanic and electrolytic cells
• identify cathode and anode in cell
• direction of electron flow in cells
• Do electrolytic cell stoichiometry with amperes and Faradays
• Nernst equation
• Calculate G and K from E˚ data
• Calculate E˚ given a table of reduction potentials
#1
A direct current of 0.125 ampere was passed through 200 milliliters of a 0.25 molar
solution of Fe2(SO4)3 between platinum electrodes for a period of 1.100 hours. Oxygen
gas was produced at the anode. The only change at the cathode was a slight change in the
color of the solution.
At the end of the electrolysis, the electrolyte was acidified with sulfuric acid and was
titrated with an aqueous solution of potassium permanganate. The volume of the KMnO4
solution required to reach the end point was 24.65 milliliters.
(a) How many faradays were passed through the solution?
(b) Write a balanced half-reaction for the process that occurred at the cathode during the
electrolysis.
(c) Write a balanced net ionic equation for the reaction that occurred during the titration
with potassium permanganate.
(d) Calculate the molarity of the KMnO4 solution.
#2
A dilute solution of sodium sulfate, Na2SO4, was electrolyzed using inert platinum
electrodes. In a separate experiment, a concentrated solution of sodium chloride, NaCl,
was electrolyzed also using inert platinum electrodes. In each experiment, gas formation
was observed at both electrodes.
(a) Explain why metallic sodium is not formed in either experiment.
(b) Write balanced equations for the half–reactions that occur at the electrodes...