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Chapter 17: Q10P (page 428)

A0.3268-gunknown containing Pb(CH3CHOHCO2)2(leadLactate, FM 385.3) plus inert material was electrolyzed to produce 0.1111gofPbO2(FM239.2). Was the PbO2deposited at the anode or at the cathode? Find the weight percent of lead lactate in theUnknown.

Short Answer

Expert verified

PbO2was deposited at the anode. The weight percent of lead lactate is wleadlactate=54.76%.

Step by step solution

01

Electrogravimetric Analysis

  • Separation along with the quantification of metals are mainly observed in electrogravimetricanalysis.
  • Electrolysis of the analyte solution is done during this procedure.
02

Determine the lead lactate

The reaction is

PbCH3CHOHCO2+2H2O鈫�PbO2+2lactate+4H++2e-

Pb2+Is oxidized to Pb4+at the anode

First, we need to calculate n of PbO2

role="math" localid="1663650526992" nPbO2=mPbO2MPbO2=0.1111g239.2g/molnPbO2=4.64脳10-4molnPbO2=nleadlactate,themassoftheleadlactateismleadlactate=nleadlactate路Mleadlactatemleadlactate=4.64脳10-4mol脳385.3g/molmleadlactate=0.17896g

So, the w lead lactate is:

wleadlactate=mleadlactatemwleadlactate=0.17896g0.3268gwleadlactate=0.5476=54.76%

The lead lactate is 54.76%.

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Most popular questions from this chapter

The figure shows the behavior of Ptand Ag cathodes at whichreduction ofH3O+toH2(g)occurs. Explain why the two curves arenot superimposed.

Current versus voltage forPtand Agelectrodes in O2 -free, aqueous H2SO4

Adjusted topH3.2.

What is the purpose of the Nafion the membrane in Figure 17-33

Chemical oxygen demand by coulonetry. An electrochemical device incorporating photooxidation on a \({\rm{Ti}}{{\rm{O}}_2}\) surface could replace refluxing with \({{\rm{C}}_2}{\rm{O}}_7^{2 - }\) to measure chemical oxygen demand (Box 16-2). The diagram shows a working electrode beld at \( + 0.30\;{\rm{V}}\) versus \({\rm{Ag}}\mid {\rm{AgCl}}\) and coated with nanoparticles of 'TiO . Wltraviolet2inradiation generates electrons and holes in \({{\rm{T}}_1}{{\rm{O}}_2}\). Holes oxidize

organic matter at the surface. Electrons reduce \({{\rm{H}}_2}{\rm{O}}\) at the auxiliary electrode in a compartment connected to the working compartment by a salt bridge. The sample compartment is only 0.18 mm thick with a volume of \(13.5\mu \,{\rm{L}}\). It requires \(\~1\;\,{\rm{min}}\) for all organic matter to diffuse to the \({\rm{Ti}}{{\rm{O}}_2}\) surface and be exhaustively oxidized.

Left: Working electrode. Fight Photocument response for sample and blank Both solutions contain \(2{\rm{M}}\,{\rm{NaNO}}\). (Dst from H zhso, D. fisng. 5 . zhang K. Cutteral, and R. Jshn, "Development of a Drect Fhotselectrocherrical Method for Deterrination of Gherrical Ouygen Demand," And. Chan. 2004, 76 155.)

The blank curve in the graph shows the response when the sample compartment contains just electrolyte. Before inradiation, no current is observed. Ultraviolet radiation causes a spike in the current, followed by a decrease to a steady level near \(40\mu \). This current arises from oxidation of water at the \({\rm{Ti}}{{\rm{O}}_2}\)sufface under ultraviolet exposure. The upper curve sbows the same experiment, but with wastewater in the sample compartment. The increased current arises from oxidation of organic matter. When the organic matter is consumed, the cument decreases to the blank level. The area between the two curves tells us how many electrons flow from oxidation of organic matter in the sample.

  1. Balance the oxidation half-reaction that occurs in this cell:

\({{\rm{C}}_e}{{\rm{H}}_k}{{\rm{O}}_a}\;{{\rm{N}}_s}{{\rm{X}}_x} + {\rm{A}}{{\rm{H}}_2}{\rm{O}} \to {\rm{BC}}{{\rm{O}}_2} + {\rm{CX}} + {\rm{DN}}{{\rm{H}}_3} + {\rm{E}}{{\rm{H}}^ + } + {\rm{F}}{{\rm{e}}^ - }\)

where X is any halogen. Express the stoichiometry coefficients A, B, C, D, E, and F in terms of c, h, o, n, and x.

  1. How many molecules of \({{\rm{O}}_2}\)are required to balance the halfreaction in part (a) by reduction of oxygen (\({{\rm{O}}_2} + 4{{\rm{H}}^ + } + 4{{\rm{e}}^ - } \to 2{{\rm{H}}_2}{\rm{O}}\))?
  2. The area between the two curves in the graph is \(\int_0^\infty {({I_{{\rm{sample }}}}} - {I_{blank}})dt = 9.43\,{\rm{mC}}{\rm{.}}\) This is the number of electrons liberated by complete oxidation of the sample. How many moles of \({{\rm{O}}_2}\) would be required for the same oxidation?
  3. Chemical oxygen demand (COD) is expressed as mg of \({{\rm{O}}_2}\) required to oxidize 1 L of sample. Find the COD for this sample.
  4. If the only caidizable substance in the sample were \({{\rm{C}}_9}{{\rm{H}}_6}{\rm{N}}{{\rm{O}}_2}{\rm{CIB}}{{\rm{r}}_2}\). what is its concentration in molL?

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.]

(a) At what cathode potential will Sb(s)deposition commence from 0.010MSbO+solution at pH 0.00? Express this potential versus S.H.E. and versusAg|AgCI. (Disregard overpotential, about which you have no information.)

SbO++2H++3e-鈫�Sb(s)+H2OE掳=0.208V

(b) What percentage of0.10MCu2+could be reduced electrolytically to Cu(s)before0.010MSbO+in the same solution begins to be reduced at pH 0.00?
See all solutions

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