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Chapter 17: Q15P (page 428)

What does a mediator do?

Short Answer

Expert verified

Between the analyte and the electrode, the mediator transfers electrons.

Step by step solution

01

Define mediator:

The mediatoradvises and aids the parties in reaching their own resolution.The mediator does not decide the conclusion, but rather assists the parties in understanding and focusing on the critical problems that must be addressed in order to achieve an agreement.

02

Role of Mediator:

The mediator transfer electrons between the analyte and electrode. When the analyte is oxidized or reduced, the mediator is regenerated.

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Most popular questions from this chapter

Consider the cyclic voltammogram of the Co3+compoundrole="math" localid="1663646447735" Co(B9C2H11)2- . Suggest a chemical reaction to account for each wave. Are the reactions reversible? How many electrons are involved in each step? Sketch the sampled current and square wave polarograms expected for this compound.

Cyclic voltammogramofrole="math" localid="1663646461802" Co(B9C2H11)2- . [Data from W. E. Geiger, Jr., W. L. Bowden, and N. El Murr, "An Electrochemical Study of the Protonation Site of the Cobaltocene Anion and of Cyclopentadienylcobalt(I) Dicarbollides," Inorg. Chem. 1979,18,2358.]

Peak current (IP)and scan rate (v) are listed for cyclic voltammetry of the reversible reaction Fe( II ) Fe(III ) of a water-soluble ferrocene derivative in 0.1MNaCLIf a graph of IPversusvgives a straight line, then the reaction is diffusion controlled. Prepare such a graph and use it to find the diffusion coefficient of the reactant from Equation17 - 21for this one-electron oxidation. The area of the working electrode is0.0201cm2, and the concentration of reactant is 1.00mM.

Consider the following electrolysis reactions.

Cathode:H2O(l)+e-⇌12H2(g,1.0bar)+OH-(aq,0.10M)

Anode:Br-(aq,0.10M)⇌12Br2(l)+e-

  1. Calculate the voltage needed to drive the net reaction if current is negligible.
  2. Suppose that the cell has a resistance of2.0Ω and a current of 100 mA. How much voltage is needed to overcome the cell resistance? This is the ohmic potential.
  3. Suppose that the anode reaction has an overpotential of 0.20 V and that the cathode overpotential is 0.40 V. What voltage is needed to overcome these effects combined with those of parts (a) and (b)?
  4. Suppose that concentration polarization occurs [OH-]s. at the cathode surface increases to 1.0 M and[Br-]s at the anode surface decreases to 0.010 M. What voltage is needed to overcome these effects combined with those of (b) and (c)?

Suppose that the diffusion current in a polarogram for reduction of Cd2+at a mercury electrode is14μAIf the solution containsof 25mLof0.50mMCd2+what percentage ofCd2+is reduced in the 3.4 min required to scan from-0.6to-1.2V?

Calculate the cathode potential (versus S.C.F.) needed to reduce cobalt(II) to 1.0μMin each of the following solutions. In each case, Co(s) is the product of the reaction. (Disregard any overpotential.)

(a) 0.10MHClO4

(b)0.10MC2O42-(Find the potential at which)[Co(C2O4)22-]=1.0μM

role="math" localid="1668354628300" Co(C2O4)22-+2c-→Co(s)+2C2O42-   E°=-0.474V

(c)0.10MFIJTA at pH 7.00(Find the potential at whichCo(HI)TA)2-∣=1.0μM.)
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