Measures-of-mass-grams措施质量克教学课件

Re-expressingconcentrations

-theplanofthenext3presentationsWewilltackletheproblemofre-expressingconcentrationsinthreestages.Theseareshownonthenext3slides:-Pharmaceuticalcalculations2Molarity

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RatioMass/volumeMolarity

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RatioCurrentpresentation‘PharmaceuticalCalculations(2)’dealsonlywithinter-conversionswithinthiscategory.

i.e.onemass/volumeintoanother.Pharmaceuticalcalculations3Molarity

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RatioMass/volumeMolarity

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RatioThenextpresentation‘PharmaceuticalCalculations(3)’willdealwithinterconversionsEITHERfrommass/volumetoanothersystemORfromanothersystemtomass/volumePharmaceuticalcalculations4Molarity

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RatioMass/volumeMolarity

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RatioThen‘PharmaceuticalCalculations(4)’willdealwithinter-conversionsfromanysystemtoanyother,usingmass/volumeasanintermediatestepwherenecessary.Inter-convertingconcentrationsexpressedasmass/volumeTipsTip(1)Takeiteasy–Doonestepatatime.Example:Youneedtoconvert25mgper5mltounitsofg/L.Ifyouareveryconfidentyoucoulddoitinasinglestep,changingboththevolumeandthemassunits.However,atthisstage,youareprobablybettertacklingonethingatatime.Itwouldbepossibletochangeeitherthevolumefirstandthenthemassorviceversa.EitherisOK.Intheexamplecalculationthatfollows,volumeistackledfirst.Tip(1)Takeiteasy–Doonestepatatime.Example:Youneedtoconvert25mgper5mltounitsofg/L.Firstconvertthevolumetolitres

25mgper5ml=5mg/ml

=5,000mg/LThenconvertthemasstograms

5,000mg/L=5g/LTip(2)Whenconvertingfromoneunittoanother,jumponelevelatatime.Example:Youneedtoconvert0.0025g/Ltounitsofmicrogram/100ml.Whentacklingthemassunits,don’ttrytojumpdirectlyfromgtomicrograms;goviamilligrams.Convertgramstomicrogramsviamg

0.0025g/L=2.5mg/L

=2,500microgram/LConvertthevolumeto100ml

2,500microgram/L=250microgram/100mlTip(3)The“Increase/decreasebothunits”ruleWhenaconversioninvolveseither:IncreasingboththemassandvolumeunitsbyonelevelorDecreasingboththemassandvolumeunitsbyonelevelthereisnoeffectivechangeofunitsandthenumberstaysthesame.15mg/ml=15g/L(mggoesuptog.mlgoesuptoL.)200mg/L=200microgram/ml(mggoesdowntomicrogram.Lgoesdowntoml.)0.75ng/ml=0.75microgram/L(nggoesuptomicrogram.

mlgoesuptoL.)Tip(4)AvoidintermediatecalculationswithexcessivelysmallorlargenumbersExample:Asolutioncontains1.5microgramper0.1ml.Re-expressasg/L.Youcouldproceedasbelow(ButIwouldn’trecommendit!)Convertmicrogramstogramsviamg

1.5microgram/0.1ml=0.0015mg/0.1ml

=0.0000015g/0.1mlConvertthevolumetolitres

0.0000015g/0.1ml=0.000015g/ml

=0.015g/LProfusionofzerosmakesarithmeticerrorsverylikely!Tip(4)AvoidintermediatecalculationswithexcessivelysmallorlargenumbersAbetterapproachis:Asolutioncontains1.5microgramper0.1ml.Re-expressasg/L.Convert0.1mlto1ml

1.5microgram/0.1ml=15microgram/mlConvertmicrogramtomg

15microgram/ml=0.015mg/mlUsethe“increase/decreasebothunits”rule

0.015mg/ml=0.015g/LExamplesofinter-convertingmass/volumeconcentrationsQuestion1(of12)Re-express0.75mg/100mlinunitsofmicrogram/100mlAnswersareprovidedafterallthequestions.Examplesofinter-convertingmass/volumeconcentrationsQuestion2(of12)Re-express2.5mgper5mlinunitsofmg/LAnswersareprovidedafterallthequestions.Examplesofinter-convertingmass/volumeconcentrationsQuestion3(of12)Re-express655mg/Linunitsofmicrogram/mlAnswersareprovidedafterallthequestions.Examplesofinter-convertingmass/volumeconcentrationsQuestion4(of12)Re-express800mg/Linunitsofg/100mlAnswersareprovidedafterallthequestions.Examplesofinter-convertingmass/volumeconcentrationsQuestion5(of12)Re-express40mgper5mlinunitsofg/LAnswersareprovidedafterallthequestions.Examplesofinter-convertingmass/volumeconcentrationsQuestion6(of12)Re-express35mg/Linunitsofg/LAnswersareprovidedafterallthequestions.Examplesofinter-convertingmass/volumeconcentrationsQuestion7(of12)Re-express50mg/mlinunitsofg/LAnswersareprovidedafterallthequestions.Examplesofinter-convertingmass/volumeconcentrationsQuestion8(of12)Re-express150microgram/mlinunitsofmgper5mlAnswersareprovidedafterallthequestions.Examplesofinter-convertingmass/volumeconcentrationsQuestion9(of12)Re-express0.035g/100mlinunitsofmg/LAnswersareprovidedafterallthequestions.Examplesofinter-convertingmass/volumeconcentrationsQuestion10(of12)Re-express7,500pg/mlinunitsofmicrogram/mlAnswersareprovidedafterallthequestions.Examplesofinter-convertingmass/volumeconcentrationsQuestion11(of12)Re-express60microgramper5mlinunitsofmgper5mlAnswersareprovidedafterallthequestions.Examplesofinter-convertingmass/volumeconcentrationsQuestion12(of12)Re-express0.004mg/mlinunitsofng/mlAnswersareprovidedafterallthequestions.Examplesofinter-convertingmass/volumeconcentrationsAnswer1Re-express0.75mg/100mlinunitsofmicrogram/100ml[Onlymassunitschange]0.75mg/100ml=750microgram/100mlExamplesofinter-convertingmass/volumeconcentrationsAnswer2Re-express2.5mgper5mlinunitsofmg/L2.5mgper5ml=5mg/10ml

=500mg/LExamplesofinter-convertingmass/volumeconcentrationsAnswer3Re-express655mg/Linunitsofmicrogram/ml[Use“Increase/decreasebothunits”rule]655mg/L=655microgram/mlExamplesofinter-convertingmass/volumeconcentrationsAnswer4Re-express800mg/Linunitsofg/100ml800mg/L=0.8g/L

=0.08g/100mlExamplesofinter-convertingmass/volumeconcentrationsAnswer5Re-express40mgper5mlinunitsofg/L40mgper5ml=8mg/ml

[Use“Increase/decreasebothunits”rule]

8mg/ml=8g/LExamplesofinter-convertingmass/volumeconcentrationsAnswer6Re-express35mg/Linunitsofg/L[Onlymassunitschange]

35mg/L=0.035g/LExamplesofinter-convertingmass/volumeconcentrationsAnswer7Re-express50mg/mlinunitsofg/L[Use“Increase/decreasebothunits”rule]

50mg/ml=50g/LExamplesofinter-convertingmass/volumeconcentrationsAnswer8Re-express150microgram/mlinunitsofmgper5ml150microgram/ml=0.15mg/ml

=0.75mgper5mlExamplesofinter-convertingmass/volumeconcentrationsAnswer9Re-express0.035g/100mlinunitsofmg/L0.035g/100ml=35mg/100ml