Because all alkali metals react with water, it is not possible to measure the standard reduction potentials of these metals directly as in the case of, say, zinc. An indirect method is to consider the following hypothetical reaction Li1(aq) 1 1 2H2(g) Li(s) 1 H1(aq) Using the appropriate equation presented in this chapter and the thermodynamic data in Appendix 3, calculate E for Li1(aq) 1 e2 S Li(s) at 298 K. Compare your result with that listed in Table 18.1. (See back endpaper for the Faraday constant.)
Week6-ToxicMetalsandElements ToxicMetals • Metals(lead,mercury,nickel) • Otherelements(arsenic,selenium) • Naturallyoccurring,combustion,occupational,hazardouswastesites CharacteristicsofhazardousSubstancesontheCERCLAPriorityList • Posethemostsignificantpotentialthreattohumanhealthbecausetheyhave knownorsuspectedtoxicityandpotentialforhumanexposure NPL-NationalPriorityList ClassificationofToxicEffectsofmetals Majortoxicmetalswithmultipleeffects Cd,Pb,Hg,Ni,As,Cr,Be,Rn Essentialmetalswithpotentialfor Zn,Cu,Fe,Mn,Mg,Mo,I,Se toxicity Metalsrelatedtomedicaltherapy Au,Al,Ga,Bi,Li,Pt Minortoxicmetals Ba,Ag,Sn,Ti,U,V Biomagnification-toxicsubstancessuchasheavymetalsbecomemore concentratedandpotentiallymoreharmfulastheymoveupthefoodchain Bioaccumulation-elementsmayaccumulateinfoodsources Uptake-substancessuchaselementsthataretakenupinedibleportionsof produceorotherfoods High-levelcontacts-usuallyoccupational AcuteToxicMetalPoisoning • s/shaverapidonset—fromafewminutestoapproximatelyonehour • s/s o Dependinguponportalofentry,symptomsmayconsistof gastrointestinaleffects(vomitingandstomachpain)andneurological effects(headaches,respiratorydistress,andconvulsions) Long-termExposureatLowLevels • s/s o difficulttodifferentiatefrom
