Electrolyzed Solution, Volume

Another indirect electrochemical heahng method involves the artificial kidney machine, with electrochemical regeneration of the dialysis solution. The common kidney machine is a dialyzer in which blood of the patient (who suffers from kiduey insufficiency) and a dialysis solution are pumped arouud iu two differeut loops, aud carbamide (urea), creatinine, and other metabolites are transferred by dialysis into the dialysis solution. For complete extraction of the metabolites, each hemodialysis session requires almost 200 L of this solution to be pumped through, so hemodialysis cau only be performed in a hospital setting. In machines equipped with electrochemical regeueratiou, the dialysis solutiou is ruu iu a closed loop, iucludiug au electrolyzer in which the carbamide is oxidized to nitrogen and carbon dioxide. The solution volume needed in this loop is rather small, so that portable kidney machines could become a reality. 

Coulometry. If it can be assumed that kinetic nuances in the solution are unimportant and that destmction of the sample is not a problem, then the simplest action may be to apply a potential to a working electrode having a surface area of several cm and wait until the current decays to zero. The potential should be sufficiently removed from the EP of the analyte, ie, about 200 mV, that the electrolysis of an interferent is avoided. The integral under the current vs time curve is a charge equal to nFCl, where n is the number of electrons needed to electrolyze the molecule, C is the concentration of the analyte, 1 is the volume of the solution, and F is the Faraday constant. 

A 1.0 M solution of NaOH is electrolyzed, generating 02(g) at the anode. A current of 0.15 A is passed through the cell for 75 minutes. Calculate the volume of (wet) oxygen generated in this period if the temperature is held at 25°C and the total pressure is 0.985 atm. [Hint Use the vapor pressure of water at this temperature from Table 10.1.)... 

The Water Coulometer. A number of aqueous solutions, when electrolyzed between inert electrodes, evolve oxygen at the anode and hydrogen at the cathode. It is therefore possible to use, as a measure of the coulombs passed, the loss in weight of the solution, the volume of either gas, or the combined volumes of both gases. In the most accurate... 

An acidified solution was electrolyzed using copper electrodes. A constant current of 1.18 A caused the anode to lose 0.584 g after 1.52 X 10 s. (a) What is the gas produced at the cathode and what is its volume at STP (b) Given that the charge of an electron is 1.6022 X 10 C, calculate Avogadro s number. Assume that copper is oxidized to Cu ions. 

Fluorine (F2) is obtained by the electrolysis of liquid hydrogen fluoride (HF) containing potassium fluoride (KF). (a) Write the half-cell reactions and the overall reaction for the process, (b) What is the purpose of KF (c) Calculate the volume of F2 (in liters) eollected at 24.0°C and 1.2 atm after electrolyzing the solution for 15 h at a current of 502 A. 

Several related bulk electrolysis techniques should be mentioned. In thin-layer electrochemical methods (Section 11.7) large AIV ratios are attained by trapping only a very small volume of solution in a thin (20-100 fxm) layer against the working electrode. The current level and time scale in these techniques are similar to those in voltammetric methods. Flow electrolysis (Section 11.6), in which a solution is exhaustively electrolyzed as it flows through a cell, can also be classified as a bulk electrolysis method. Finally there is stripping analysis (Section 11.8), where bulk electrolysis is used to preconcentrate a material in a small volume or on the surface of an electrode, before a voltammetric analysis. We also deal in this chapter with detector cells for liquid chromatography and other flow techniques. While these cells do not usually operate in a bulk electrolysis mode, they are often thin-layer flow cells that are related to the other cells described. 

When a solution of volume 100 cm containing metal ion, at a concentration 0.010 M is electrolyzed with a rapid scan at a large-area (10 cm ) rotating disk electrode, a limiting current of 193 mA is observed for reduction to metal M. Calculate the value of the mass transport coefficient mj 2+, in cm/s. If an electrolysis of the solution is carried out at this electrode at controlled potential in the limiting current region, what time will be required for 99.9% of the to be plated out How many coulombs will be required for this electrolysis ... 

The above-prepared solution (75 ml.) is diluted with an equal volume of H3O and electrolyzed at a platinized Pt cathode (surface = 5 cm. ) at 2.5 amp. until hydrogen evolves. The anode is made of smooth Pt sheet it is Immersed in 5 N HCl, which is separated from the cathode space by means of a clay cell. 

It is often said that one can run polarograms many times with the same solution because the amount of material electrolyzed under polarographic conditions is so small. With the system described in problem 8, for how long could one electrolyze at the plateau of the wave before the diffusion current changes by 1% Assume that the volume of solution in the polarographic cell is 50 mi. 

Later Drechsel electrolyzed normal capronic acid with alternating currents. The electrolytic solution contained, in a volume of 3 liters, 200 g. of capronic acid as magnesium salt and was nearly saturated with acid magnesium carbonate. Platinum electrodes were used. At the end of the experiment the following compounds could be identified in the solution ... 

A certain amount of cobalt sulfate solution in which a certain pH value was prepared and the concentration of Co was 1.0 moFL V The chromatographic column was stripped by this solution to start extraction. When it got balanced, the chromatographic column was stripped by HAc-NaAc buffer solution with a certain pH value. When the stripped liquid reached a certain eluate volume, HCl solution in which a certain concentration was used as eluant and stripped cobalt. Finally the metal cobalt was obtained by concentrate and electrolyzes eluate. 

---