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Chapter 17: Q5P (page 427)

(a) which voltage,V1orV2in the diagram is constant in controlled-potential electrolysis? Which are the working, auxiliary, and reference electrodes in the diagram?

(b) Explain how the Luggin capillary in Figure 17-4 measures the electric potential at the opening of the capillary.

Short Answer

Expert verified
  • The voltage V2in the diagram is constant in controlled – potential electrolysis.

Step by step solution

01

Definition of Controlled – potential electrolysis:

  • Bulk electrolysis is also known as potentiostatic coulometry or controlled potential coulometry.
  • The experiment is a form of coulometry which generally employs a three electrode system controlled by a potentiostat.
02

Illustration of electrodes: 

  • The electrodes are: Auxiliary, reference, working


03

 Measuring electric potential by using Luggin capillary: 

  • The potential of the electrode we are testing is measured so that along the surface of this electrode at a distance of 2-3 mm put the top of the so-called Luggin's capillary that is over the vessel and / or of the corresponding electrolyte bridges connected to some reference electrode with which forms a separate cell.
  • With the help of a known value of the reference electrode potential and of the measured cell voltage the electrode potential is calculated.
  • In Figure 17-4, the potentiometer measures the voltage between the Cu electrode and a reference electrode immersed in 1.0 V2and connected to the bulk solution via a Luggin capillary, AgCl.

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Most popular questions from this chapter

Chlorine has been used for decades to disinfect drinking water. An undesirable side effect of this treatment is reaction with organic impurities to create organochlorine compounds, some of which could be toxic. Monitoring total organic halide (designated TOX) is required for many water providers. A standard procedure for TOX is to pass water through activated charcoal, which adsorbs organic compounds. Then the charcoal is combusted to liberate hydrogen halides:

Organichalide(RX)→o2/800°CCO2+H2O+HX

HX is absorbed into aqueous solution and measured by coulometric titration with a silver anode:

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When 1.00 L of drinking water was analyzed, a current of 4.23 mA was required for 387 s. A blank prepared by oxidizing charcoal required 6 s at 4.23 mA. Express the TOX of the drinking water as μmol halogen/L. If all halogen is chlorine, express the TOX as μgCI/L.

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