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QUESTIONS AND PROBLEMS

1. Explain why electrochemical methods measure the activity rather than concentration?
2. Given the E 0 values of the following two half-reactions:

Zn ! Zn 2þ þ2e E 0

¼ 0 : 763 V

Fe ! Fe 2þ þ2e E 0 ¼ 0 : 441 V

(a) Write a balanced complete oxidation-reduction reaction.
(b) Explain whether the corrosion of an iron pipe (i.e., Fe ! Fe 2þ ) in the presence of
Zn=Zn 2þ is thermodynamically possible or not?
(c) Explain whether or not Zn will protect the corrosion of iron pipe if metallic Zn is in
direct contact with the iron pipe?

3. Construct a complete balanced oxidation-reduction reaction from each pair of two half-
reactions:

ðaÞ H 2 ! 2H þ þ2e Fe 2þ ! Fe 3þ þe

4O 2 ðgÞþH þ þe ¼¼ ½H 2 O H 2 ! 2H þ þ2e
ðcÞ 2IO 3 þ12H þ þ10e ¼¼ I 2 þ6H 2 O2I ¼ I 2 þ2e
4. Given the electrochemical cell as shown in the figure below: (a) Which one of
the following is being oxidized: H 2 ,H þ ,I 2 , or both H 2 and I 2 ? (b) Which one of the

ðbÞ 1 =

* Suggested readings.