Environmental Engineering Reference
In-Depth Information
e
-
P
Ion
transport
H
2
(g) →
pH
2
= 1 atm
{I
-
} = 1
{H
+
} = 1
SHE
Indicator electrode
1/2H
2
(g) → H
+
+ e
-
1/2 I
2
(aq) + e
-
→ I
-
following is an oxidizing agent: H
2
,I
2
,orI
? (c) Which one of the following is
incorrect for the reaction: H
2
þ I
2
@
2H
þ
þ2I
? (i) Two moles of electron are
involved, (ii) The oxidation of H
2
takes place at the anode, (iii) Electron moves from
cathode to anode.
5. Write the standard cell notation for the cell shown in Problem 4.
6. Write the standard cell notation for the cell shown in Figure 11.5 employed for dissolved
oxygen measurement.
7. Why TISAB is added to the sample solution when ion selective electrode (ISE), such as
fluoride electrode, is used to measure the ion concentration?
8. Explain the principles of ion selective electrode used for the measurement of (a) pH and
(b) nitrate.
9. Is pH membrane electrode based on the redox reaction that can be described by the
Nernst equation? Why or why not?
10. Describe the precautions for the use and maintenance of glass pH electrodes.
11. Give a list of common ions of environmental significance that can be analyzed by ion
selective electrodes.
12. The potential (E
1
) in a 0.0015 mol/L F
standard was measured to be 0.150 V by a
fluoride electrode in reference to a saturated calomel electrode. For the same electrodes,
a voltage of 0.250 (E
2
) was measured in a sample containing an unknown concentration
of F
. Calculate the concentration of F
in the unknown sample (Hint: Use Eq. 11.12).
13. Three electrochemical titration methods are discussed in this chapter: potentiometirc,
coulometric, and amperometric titration. (a) Describe the fundamental differences of the
principles and (b) Give examples of environmental measurements.
14. Use a table to compare the similarities and differences between potentiometry,
coulometry, and voltammetry. Consider the following comparisons: (a) The electrical
measurement (e.g., current, potential, and charge), (b) The types of cells (galvanic and
electrolytic), (c) The fundamental equation employed for quantitative measurement
(Nernst, Faraday, and Ohm's), and (d) The ability for qualitative determination.
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