Chapter 21

PROFESSOR'S FAVORITE PROBLEM Contributed by Professor Dong-Soo Lee, Yonsei University, South Korea Your friend asserts that in a purely aqueous medium (i.e., not containing any organic solvent), it is impossible to have a specific conductance less than that of pure water. You, on the other hand, know that in very dilute strong acid and base solutions, the conductivity can indeed be less than that of pure water. Compute and plot the specific conductance of a \(0.05-5 \mu \mathrm{M}\) solution of \(\mathrm{LiOH}\)

Of common electrolytes, \(\mathrm{KCl}\) is used most often in many electrochemical devices like reference electrodes, etc. What property leads to this choice?

Three molecules of similar size are bearing one, two, and three negative charges, respectively. (a) Which molecule has the highest electrophoretic mobility? (b) Is the electrophoretic mobility a positive or negative value?

You are having a difficult time separating potassium and ammonium ion by CE using a certain BGE at pH 7 under + HV applied. It has been suggested that you could (a) add some 18 -crown-6 to the BGE, (b) increase the \(\mathrm{pH},\) (c) increase the voltage, (d) use a longer capillary, (e) reverse the voltage polarity, and (f) use a smaller capillary. What would you expect to happen if you take these steps individually, without altering other parameters?