1、Volumetric ANALYSIS,Introduction,Analytical Chemistry: determining the chemical composition of samples of matter. Qualitative analysis: identify of functional groups, or atomic, molecular structure of analyte ( what?) Quantitative analysis: amount of analyte ( how much?),3,定性分析 Qualitative analysis

2、物質(zhì)的組成 定量分析 Quantitative analysis 成分的含量 結(jié)構(gòu)分析 Structure analysis 物質(zhì)的結(jié)構(gòu) DNA測序（DNA Sequencing) 形態(tài)分析 Species analysis 物質(zhì)的形態(tài) 能態(tài)分析 Energy-state analysis 物質(zhì)的能態(tài),分析方法的分類,Classical methods (Chemical analysis),Qualitative analysis: Analytes,Products,recognized,yield,treated with reagents,Colors Boiling (melting

3、) points Solubilities Odors Optical activities Refractive indexes,Quantitative analysis: gravimetric; titrimetric,Instrumental methods (Instrumental analysis),Early in 20th century,Measurements of physical (chemical) properties of analytes: -conductivity; electrode potential; light absorption (emiss

4、ion); mass-to-charge ratio; fluorescence,Highly efficient chromatographic and electrophoretic techniques,replaced,Distillation, extraction, precipitation,a. Development of instruments and computer,b. Development of separation methods,c. Classification of instrumental analysis,Optical Analysis (spect

5、rometry); Electrochemical Analysis; Chromatography,General principles of volumetric analysis,Chemical analyses can be made by determining how much of a solution of known concentration is needed to react fully with an unknown test sample.,通過測定需要多少已知濃度的溶液與未知樣品徹底反應(yīng)來做化學(xué)定量分析。,The method is generally refe

6、rred to as volumetric analysis and consists of titrating the unknown solution with one of known concentration (a standard solution).,General principles of volumetric analysis,這個方法一般稱為容量分析，由已知濃度（標準溶液）的溶液滴定未知濃度的溶液。,By titration, you can determine exactly how much of a reagent is required to bring abou

7、t complete reaction of the test solution.,General principles of volumetric analysis,通過滴定法，你可以準確測定需要多少試劑可完成實驗溶液的完全反應(yīng)。,Usually, completion of the reaction is indicated by a sudden, visible change in the reaction system that coincides with the stoichiometric relationship between moles or equivalents of

8、 the reagent solution and the reactant in the test solution.,General principles of volumetric analysis,通常，反應(yīng)體系里完全完成的反應(yīng)有一個可見的，突然的變化來預(yù)示；而這與試劑溶液及反應(yīng)溶液中的反應(yīng)物之間的摩爾或當(dāng)量之化學(xué)計量關(guān)系是吻合的。,A drop or two of an appropriate indicator solution produces a color change at the point where the reaction is complete - referre

9、d to as the end point.,General principles of volumetric analysis,一到兩滴合適的指示劑溶液在反應(yīng)完成的那一點產(chǎn)生顏色的變化-稱為終點 。,The normality of an acid or base of unknown concentration may be determined by titration. The advantage of using normality rather than molarity is that equal volumes of solutions of equal moralities

10、have identical capacities for neutralization, because they contain the same number of equivalent weights.,General principles of volumetric analysis,酸或堿的未知當(dāng)量濃度可由滴定法來確定。這里使用當(dāng)量濃度而不是摩爾濃度的優(yōu)點是相同摩爾數(shù)的相同體積的溶液有相同的中和能力，因為它們所含的當(dāng)量重量相同。,In a titration, we compare equivalent weights of acid and base. The number of

11、 equivalents of acid is equal to the product of the volume of the acid solution and its normality:,General principles of volumetric analysis,滴定中我們比較酸,堿的當(dāng)量。酸的當(dāng)量數(shù)等于酸溶液產(chǎn)品的體積和其當(dāng)量濃度: Va X Na =equivalents of acid,Selecting an analytical method,What accuracy is required?-Accuracy/Bias How much sample is av

12、ailable?-sensitivity What is the concentration range of the analyte?-Dynamic range What components of the ample will cause interference?-Selectivity What are the physical and chemical properties of the sample matrix? -analytical methods How many samples are to be analyzed?-economic standpoint,Defini

13、ng the problem:,Precision and accuracy,15,精密度(precision)：在相同條件下，多次測定結(jié)果相互接近的程度。 偏差(diviation)：表示精密度的大小，偏差越小，測定結(jié)果的精密度越高。,精密度與偏差,所有滴定步驟都必須謹慎操作,Procedure of volumetric analysis,Care must be exercised throughout the titration procedure.,Titration of Vinegar According to the equation One molecule of NaOH

14、neutralizes one molecule of acetic acid, or one gram-molecule weight of NaOH neutralizes one gram-molecular weight of acetic acid. (gram-molecular weight, amount of a molecular substance whose weight, in grams, is numerically equal to the molecular weightof that substance.),Procedure of volumetric a

15、nalysis,Calculate the amount of acetic acid present in the vinegar. Report this amount as the percentage of acetic acid,Procedure of volumetric analysis,計算乙酸在食醋中的含量。 用乙酸的百分比報告這一含量,If pH meter is available, repeat the above process using a pH meter for constantly determining the pH. When the endpoint

16、 is reached, continue adding the base to expand the curve further. Make a graph for this titration.,Procedure of volumetric analysis,如果有pH計，那么重復(fù)上述過程，用酸度計持續(xù)不斷測定pH值。當(dāng)?shù)竭_終點時，繼續(xù)加堿使曲線進一步延伸。給這個滴定過程做圖。,Calculate the percentage of acetic acid in vinegar.,Questions to consider,計算醋里乙酸的百分比。,What is the pH range for phenolphthalein?,Questions to consider,酚酞pH范圍是什么（多少）？,Why should the solution in the flask constantly be stirred?,Questions to consider,為什么燒瓶中的溶液要不斷的攪拌？,Consider a hypothetical experiment in which you weighted out 2.0g of oxalic acid and titrated it with 43ml of 1.5N NaO