简介:在高中阶段,同浓度的NaHCO3溶液和CH3COONa溶液的pH比较在高中习题和各地高考题中都多次涉及,但笔者经过多方面实验和计算,发现两者比较存在很多问题,教师编制练习题时应审慎处理。
简介:采用HF/DFT的混合泛函PBE0和UPBE0优化了配合物[Os(PH3)2(CN)2(N^N)](其中N^N=2,2′-吡啶)的基态和激发态结构.在基态和激发态结构的基础上,利用含时密度泛函理论(TD-DFT)方法,结合极化连续介质(PCM)模型分别计算了它在二氯甲烷(1)、甲醇(2)、气态(3)和乙腈(4)溶液中的吸收和发射光谱.研究结果表明:优化得到的几何结构参数和相应的实验值符合得非常好.在极性较大的溶剂(2和4)中Os—P(1)和Os—C(1)键较长,Os—N(3)键较短,溶剂的极性会影响配合物的电子云分布.配合物在1-4溶剂中的最低能吸收和发射均来自分子轨道68→71的激发,该激发被指认为[d(Os)+π(CN)+π(N^N)→π*(N^N)]的跃迁具有混合的MLCT/LLCT特征.配合物在1-4溶剂中的最低能吸收和发射分别在471,410,488和445nm以及598,536,634和545nm,表明随着溶剂极性的逐渐增大(3〈1〈4〈2),最低能吸收和发射发生明显的蓝移.这显示出通过改变溶剂极性可以调节配合物的发光颜色.
简介:Monoammoniumphosphate(1molL^-1),monopotassiumphosphate(1molL^-1)andaluminumchloride(5×10^-3molL^-1)wereusedtoinvestigatetheinfluenceofpHontheformationofNH4-taranakiteandK-taranakiteinsystemswithahighNH4H2PO4orKH2PO4concentration.TheexperimentaldataindicatedthatthereactionproductsofaluminumwithNH4H2PO4orKH2PO4changedwiththepHinthesystems.InapHrangeof2.5to10.0,asthepHincreased,theproductsineitherammoniumorpotassiumsystemfollowedthesequence:taranakite,amorphous(NH4,K)2AIH(PO4)2.4H2O,andthencrystalline(NH4,K)AlPO4OH.2H2O.However,thepHrangesoftheformationoftheseproductsinammoniumsystemweredifferentfrompotassiumsystem.NH4-taranakiteformedfrompH2.75topH5.75,whereasK-taranakiteformedinthepHrangeof3.00to5.0,Fromthetheoreticalcalcuationbyacomputerprogram(GEOCHEMversion2.0),NH4-taranakteandK-taranakitecouldformatthepHfrom1.50to8.30andfrom1.25to8.45,respectively.ThesepHrangesweremuchwiderthantheexperimentalresults.Thedifferencebetweentheexperimentaldataandtheoreticaldatawasattributedtothelackofkineticdataand/ortheincompletenessandinaccuracyofthethermodynamicdatainthedatabaseoftheprogram.ThepHrangesoftheformationofthetaranakitesindicatedthatthetaranakitescouldexistintheimmediatevicinityofphosphateferilizerzoneasreactionproductsofphosphatefertilizerswithsoils,especiallyacideicsoils,resultinginthefixationofnotonlyphosphatebutalsonitrogenand/orpotassiuminsoils.
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简介:Thecopolymerizationofp-diethynylbenzene(PDEB)withphenylacetylene(PhA),4,4’-diethynylbiphenyl(DEBP)orm-diethynylbenzene(MDEB)arestudiedbyvaryingmoleratiosofmonomers.WhenthemoleratiosofPDEB/PhAarelessorequalto1/5,thecopolymersaresolubleandfusible,buttheothercopolymersareinsolubleandinfusible.Theresultsshowthatthegoodsolventofcross-linkedcopolymersisbenzeneandtheirsolubilityparameteris9.15cal0.5.cm(-1.5).Andtheirswellability(θp),Hugginsparameter(χ),density(d425)andtheaveragemolecularweightsbetweencrosslinks(c)aremeasured.Itisfoundthatθpandcofcopolymersaregreaterbutd425islessthanthatofrespectivehomopolymers.IRspectrashowthatthecopolymershavetransoidconfigurationandsmallnumberofunreactedethynylgroupsexistinthecopolymers.Themechanismaboutthepolymerizationoracetylenicderivativesinitiatedby(Ph3P)2PdCl2isdiscussed.
简介:Withtherapiddevelopmentofglobalinformationhighway,multimediacommunicationtechnologyplaysamoreandmoreimportantroleinnationaleconomicandsocialdevelopment.However,themultimediacommunicationsystemisacomplicatedrealtimedistributedsystemanditssoftwareisdifficulttodevelop.Inordertoimprovetherapiddevelopmentandapplicationofthemultimediacommunicationtechnology,thereisanurgentneedtocarryoutthebasicresearchworkofsoftwaredevelopmentplatforminthisfield.