5 20 Points Consider The Following Cell Ag S Agcl S Kci Sat Ca Aq Ca C204 S Pb C204 5 Pb S The Ce 1 (85.53 KiB) Viewed 32 times
5. (20 points) Consider the following cell: Ag(s)| AgCl(s), KCI (sat) || Ca²+(aq)| Ca(C204)(s), Pb(C204)(5) Pb(s) The cell is constructed using an Ag/AgCl reference electrode and a lead electrode that is coated with a paste made up of calcium oxalate and lead oxalate. This cell responds (via the measured cell voltage) to the activity (or concentration) of calcium in solution. Consider that the experimental solution has an “ionic strength” adjuster so that calcium activity is constant. The experimental solution pH >8 so that any oxalate is completely ionized. a. Given the following information: Pb2+ (aq)+2e + Pb(s) E = -0.13V PbC,0,(s) + Pb2+ (aq) + C,02(aq) = 8.5x10-9 CaC,0,(s) + Ca²+ (aq) + C203- (aq) K sp2 = 1.8x10-9 spl The reference electrode (Ag/AgCl) has a voltage of 0.198V Write out the Nernst equation for this cell. Demonstrate that the measured cell voltage will be a function of Ca2+ concentration (assume the activity coefficient of Ca2+ is 1).
b. If the Ca2+ concentration is 2.5 mM what is the predicted cell voltage. c. Is this an electrode of the first, second or third kind?
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