Questions (Lectures 1-8) PDF

Preview

Summary

Download Questions (Lectures 1-8) PDF

Description

Spas D. Kolev,

School of Chemistry, The University of Melbourne,

CHEM30012,

Analytical and Environmental Chemistry, Lectures 1-8

CHEM30012 (Analytical and Environmental Chemistry) Sample Exam Questions Question 1:

What is the difference between a galvanic and an electrolytic

electrochemical cell?

Question 2:

A Cd plate is immersed in a 1 M CdSO4 solution and a Ag plate is

immersed in a 1 M AgNO3 solution. Calculate the corresponding electrode potentials, write the electrode reactions, and indicate which of the two electrodes will be the anode and which will be the cathode. Use concentrations instead of activities. Sketch the line diagram of the corresponding galvanic electrochemical cell. Eo (Cd2+

+ 2e -  Cd)

= -0.402 V

Eo (Ag+

+ e-  Ag)

= 0.799 V

Question 3: M KClO4

What is the activity coefficient of the K+ ion in a solution of: 1.00x10-3 2 and 1.00x10-3 M Na2SO4? (use ) X X

Question 4:

 log   0.51 z

I

Write the stoichiometric equations of the two reactions involved in

generating the potential of the Ag/AgCl reference electrode. The concentration of which ion determines the potential of this electrode?

Question 5:

Calculate the potential of a Ag/AgCl reference electrode

immersed in a 1.00x10-3 M solution of NaCl. Use concentrations instead of activities. The solubility product of AgCl (Ksp) is 1.82x10-10 mol2/L2 and Eo’ = Eo = 0.779 V.

Question 6:

What electrochemical quantity is measured in potentiometry. Is a

typical potentiometric electrochemical cell a galvanic or an electrolytic cell?

Spas D. Kolev,

School of Chemistry, The University of Melbourne,

Question 7:

CHEM30012,

Analytical and Environmental Chemistry, Lectures 1-8

Why aren’t metallic electrodes of the first kind used widely for

potentiometric analyses?

Question 8:

Name the four main types of ion-selective electrodes.

Question 9:

Sketch a typical fluoride ion-selective electrode and name its

main

components? Explain its response mechanism.

Question 10:

How many electrodes are used in a typical voltammetric cell? Explain

their role in a voltammetric measurement?

Question 11:

What causes concentration polarization?

Question 12:

What current is used in quantitative polarographic analysis? Why is it

necessary to use a supporting electrolyte and to avoid shaking the polarographic cell during measurements?

Question 13:

Why is dissolved oxygen removed from the sample solution before

polarographic measurements?

Question 14:

Can we determine polarographically metal ions with negative formal

potentials in the presence of the hydrogen ion?

Question 15:

What characteristics of the polarographic wave are used for

quantitative and qualitative polarographic analysis?

Question 16:

How is the charging current generated in polarographic

measurements?

Question 17:

Why does differential pulse polarography offer higher resolution over

direct current polarography?

Spas D. Kolev,

School of Chemistry, The University of Melbourne,

Question 18:

CHEM30012,

Analytical and Environmental Chemistry, Lectures 1-8

Name the two steps used in ASV and PSA? What electrochemical

processes take place at a mercury working electrode during each one of these two steps if the analyte is a metal cation? Which one of these two steps involves mechanical stirring of the solution and why is this necessary?

Question 19:

What physical quantity is measured during the stripping step in

potentiometric stripping analysis? If the transient analytical signal in potentiometric stripping analysis is a step-wise curve with one potential plateau, which characteristic of this curve will you use to determine the concentration of the analyte?

Question 20:

What is the difference between the potential pulses applied in

differential pulse polarography and in normal pulse polarography?

Question 21:

What process is responsible for the accumulation of the analyte

in adsorptive stripping voltammetry?

Question 22:

What physical quantity is measured in amperometry and how

can it be related to the concentration of the analyte? Can amperometry be used in qualitative chemical analysis?

Question 23:

How can you determine from a cyclic voltammogram whether a

half-reaction is reversible?

Question 24:

Which potentials are maintained constant in electrogravimetry

without potential control and in controlled-potential electrogravimetry?

Question 25:

What is equivalent conductance? Calculate the mass of 1

equivalent of H2SO4 if the molar mass of H2SO4 is 98....