1.GravimetricGravimetricmethodsare1.GravimetricGravimetricmethodsarequantitativemethodsthatarebasedupondeterminingthemassofapurecompoundtowhichtheanalyteischemicallyrelated.theanalyteisconvertedtoa21A.TypesofGravimetric1A.TypesofGravimetricPrecipitationAgravimetricmethodinwhichthesignalisthemassofaprecipitate.Agravimetricmethodinwhichthesignalisthemassofanelectrodepositonthecathodeoranodeinanelectrochemicalcell.VolatilizationAgravimetricmethodinwhichthelossofavolatilespeciesgivesrisetothesignal.31B.precipitationformandweighing++ CaCCH1B.precipitationformandweighing++ CaCCH 2+++41B-1.precipitation5HighGoodcrystalline1B-1.precipitation5HighGoodcrystallineRequirementstheprecipitation1B-2.weighing6穩(wěn)定，不易與O2H1B-2.weighing6穩(wěn)定，不易與O2H2OCO2eg：determinationofweighingAl 0.1888eg：determinationofweighingAl 0.18880.10001.704g0.00021000.100071CChemical aaA→mM→abABb mBBFmBaMmmAAbMbMBAStoichiometric1CChemical aaA→mM→abABb mBBFmBaMmmAAbMbMBAStoichiometricM2nF 244M4442MFMgPP MMgP StoichiometricMFaMStoichiometricMFaMb9A0.5000goresampleresultedinCalculatethepercentofCr2O3intheMCrF A0.5000goresampleresultedinCalculatethepercentofCr2O3intheMCrF 2M4mBaCrOMCrmF 2Mms40.25302.Solubilityof2A.solubility[MaoA[A2.Solubilityof2A.solubility[MaoA[AMMKoK[M][A]K 一般不考慮離子強度的影響，書后表中數(shù)據(jù)為活度積引入相應(yīng)的副反應(yīng)系數(shù)[M'][A']KK A條件溶度積(conditionalsolubilitymmnnsmmmnnsmnKsp(ms)m(ns)nKspsmnmmnn2B.Influenceofthe2B.Influenceofthesolubilityof2B-1.Commonion2B-2.Salt2B-3.Acid2B-4Complex2B-5Other2B-1.CommonionKsp2B-1.CommonionKspsMA(s)MAMs++AsKspMA(s)MAMs++AsKspKspsKsps[M2B-2.Salt 2B-2.Salt [M][A]MIs2B-3.Acid+-1K2B-3.Acid+-1KsKA(H1）knownCalculatethesolubilityofCaC2O4inpH=4.00andpH=2.00solution,respectively.設(shè)CaC2O4在pH4.00溶液中的溶解度為1）knownCalculatethesolubilityofCaC2O4inpH=4.00andpH=2.00solution,respectively.設(shè)CaC2O4在pH4.00溶液中的溶解度為2.0:Ka 5.9102,K 6.4H121[H]2K[H]K 2.56 (HKa A(Hs2.01097.2105(mol/同理設(shè)CaC2O4在pH2.00溶液中的溶解度為s 同理設(shè)CaC2O4在pH2.00溶液中的溶解度為s C (H s'2.06.1104(mol/2）unknown affect MH2O=+AHA+OH-s02）unknown affect MH2O=+AHA+OH-s0s0Kmsmn 0pH7.00AHA的離解控制酸s0>10-s0<10-solution.Ksp(Ag2S)=10K48.4s 334solution.Ksp(Ag2S)=10K48.4s 334[H 7KS2(HKKa aKsp,AgSS(H102.5107s1.11032 442B-4.Complex2B-4.ComplexM=LLMAKms M(M=LLMAKms M(KspM(smmnn1i[L]M(ComplexL是OH1ComplexL是OH1i[L]iS0很小，[L]例如AgI在0.1mol/LNH3S0較大，[L]例如pH10時BaSO4在0.01mol/LEDTACalculatethesolubilityofBaSO4CalculatethesolubilityofBaSO4inpH10.0Inthesolution,theconcentrationofEDTAthatisnotincomplexwithBa2+is0.020mol/L.Ksp( 4lg pH10:lgY(H[Y[Y']0.020/10Y(H[Y[Y']0.020/10Y(HBa(Y1KBaY[Y]1107.6103molsKsp(BaSO4 Ba(Y=MA…+AAl(OH)34AgIAgI,AgI=MA…+AAl(OH)34AgIAgI,AgI,AgI2,234AgBrAgBr,AgBr2CalculatethesolubilityofAgClin0.10mol/LCl-([ClCalculatethesolubilityofAgClin0.10mol/LCl-([Cl-]:1Ksp(AgCl,2105.234105.70,34K'sp(AgCl)Ksp(AgCl)K'sp(AgCl)Ksp(AgCl)Ag(ClKsp(AgCl)(11[Cl]2[Cl]23[Cl]34[Cl]4109.75(1103.481 105.304K'sp(AgCls4.510mol[ClCommon[Cl]/molCommon[Cl]/mols/mol02B-5.Other**2B-5.Other***SrSO4S*SrSO4S=6.2×10-4S=6.7×10-4S=9.3×10-4calculatethesolubilityofcalculatethesolubilityofinaqueoussolution(ignorehydrolysis),in0.01molL－1CaCl2solution,0.01molL（1）KspmolL[Ca2+][F－]2=s·（2s）2=∴s=（2）considerthecommonionmolL（3）considertheacid128.FFKKnA(（3）considertheacid128.FFKKnA(H2 F(Hsmmnn4s1.9103mol3.classificationandformationprocessof3A.classificationof小大0.1~143.classificationandformationprocessof3A.classificationof小大0.1~140.02小大AlO.nH 2Typesof3B.Formationprocessof沉淀的形成是一個復(fù)雜過程,有關(guān)這方面的理論都是定性的解釋或經(jīng)驗公式的描述,很不成熟3B.Formationprocessof沉淀的形成是一個復(fù)雜過程,有關(guān)這方面的理論都是定性的解釋或經(jīng)驗公式的描述,很不成熟4Cr44 4Cr44 4H核 臨界 10- 相成均相particleparticle聚集速度>定向速度無定形沉淀定向速度>聚集速度4.Factorsoninfluence4.Factorsoninfluenceoftheprecipitate4A.4B.4C.Methodstothecontaminateof4A.Coprecipitationisaprocess4A.CoprecipitationisaprocessinwhichnormallysolublecompoundsarecarriedoutofsolutionbySurfaceadsorptionMixedCrystalocclusionorinclusion4A-1.Surface4A-1.SurfaceBaSO4Ba-NO3-3BaSO4Ba-NO3-3BaSOO44AdsorptionisoftenthemajorAdsorptionisoftenthemajorsourcecontaminationincoagulatedcolloidsbutofnosignificanceincrystallineprecipitates.Methodforminimizingadsorbedimpuritiesoncolloids.4A-2.Mixed 的半徑相近、晶格相同、電荷相同時，在沉淀4A-2.Mixed 的半徑相近、晶格相同、電荷相同時，在沉淀4A-3.occlusionor4A-3.occlusionor Whenrapidgrowthtrapsapocketofsolution.WhiletheWhenrapidgrowthtrapsapocketofsolution.Whilethesolventcanberemoved,thetrappedionswillremainafterdrying. Coprecipitationerror Coprecipitationerror Coprecipitatedimpuritiesmaycauseeithernegativeorpositiveerrorsinananalysis.(contaminant)不是被測組分的組成，留，如Ba(NO3)2會產(chǎn)生正誤差。因為Ba(NO3)2的式量大于sulfate,但如果吸留的是BaCl2則會5.Selectionofprecipitated5A.Crystallineprecipitate5B.5.Selectionofprecipitated5A.Crystallineprecipitate5B.Amorphous5C.HomogeneousPrecipitated5A.Crystalline沉淀與母液放置一段時間，小顆粒晶體逐漸溶解，大顆粒晶體進一步長大，晶體結(jié)構(gòu)更完整，沉避免局部過濃形成大量的晶降低溶液的相對過飽和程度，控制聚Precipitated5A.Crystalline沉淀與母液放置一段時間，小顆粒晶體逐漸溶解，大顆粒晶體進一步長大，晶體結(jié)構(gòu)更完整，沉避免局部過濃形成大量的晶降低溶液的相對過飽和程度，控制聚集速度，形成大顆粒結(jié)晶；比表面小，吸附??；雜質(zhì)濃度小，減小共沉陳攪慢熱稀Precipitated5B.Amorphous促進沉淀凝聚，防止形成膠體溶液，減少沉淀對雜質(zhì)的減小離子的水化程度，形成沉淀含水量少，體積較小，結(jié)構(gòu)較緊Precipitated5B.Amorphous促進沉淀凝聚，防止形成膠體溶液，減少沉淀對雜質(zhì)的減小離子的水化程度，形成沉淀含水量少，體積較小，結(jié)構(gòu)較緊中和膠體微粒的電荷，降低水化程度，防止膠體溶液攪熱濃快5C.Homogeneous在酸性介質(zhì)中沉淀5C.Homogeneous在酸性介質(zhì)中沉淀例H2C2O42NH3CaCO244可得到具有結(jié)晶性質(zhì)的Fe2O3nH2O等水合氧化物AAB。2AgCl沉淀在0.1mol·L–1KNO32AgCl沉淀在0.1mol·L–1KNO3BBBACB.DBACB.DBCACBCACBD6、質(zhì)量為mg的有機化合物，加入濃H2SO4燒為G6、質(zhì)量為mg的有機化合物，加入濃H2SO4燒為Gg的Pt，則試樣中N%BGM(NG2M(N Mm(A) M(Pt)mGM(NGM(N(C) 2M(Pt)mmAtelevatedtemperatures,Atelevatedtemperatures,NaHCO3isconvertedquantitativelytoNa2CO3:2NaHCO3(s)Na2CO3(s)CO2(g)Ignitionofa0.3592gsampleofanantacidtabletcontainingNaHCO3andnonvolatileimpuritiesyieldedaresidueweighing0.2362g.CalculatethepercentpurityoftheA0.2795gsampleofanorganicmixturecontainingonlyC6HA0.2795gsampleofanorganicmixturecontainingonlyC6H6Cl6(290.83g/mol)andC14H9Cl5(354.49g/mol)wasburnedinastream