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Chapter Ten Titrimetry

Chapter Ten Titrimetry. Inorganic chemistry Organic chemistry Physical chemistry Analytical chemistry. Chemistry. 试 样 用 量. 分析目的. 分析对象. 方法原理. 分析任务. 仲裁分析 arbitral. 定性分析 qualitative. 定量分析 quantitative. 结构分析 structural. 无机分析 inorganic. 有机分析 organic. 化学分析 chemical.

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Chapter Ten Titrimetry

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  1. Chapter TenTitrimetry Inorganic chemistry Organic chemistry Physical chemistry Analytical chemistry • Chemistry

  2. 试 样 用 量 分析目的 分析对象 方法原理 分析任务 仲裁分析 arbitral 定性分析 qualitative 定量分析 quantitative 结构分析 structural 无机分析 inorganic 有机分析 organic 化学分析 chemical 仪器分析 instrumental 常量分析 macro 半微量分析 semi-micro 超微量分析 ultra-micro 微量分析 micro 例行分析 routine 分析方法的分类

  3. 1 分析任务 • 定性分析（qualitative analysis）： 鉴定物质由哪些元素、原子团或化合物组成 • 定量分析(quantitative analysis)： 测定物质中有关成分的含量 • 结构分析(structural analysis)： 研究物质的分子结构或晶体结构

  4. 2 试样用量 区别于被测组分含量高低（质量分数的大小）： 常量组分（ > 1%）、 微量组分（0.01%~1%）、 痕量组分（ < 0.01%）

  5. 3 分析目的 • 例行分析（Routine analysis）： 一般化验室日常生产中的分 析，也称常规分析 • 仲裁分析（Arbitral analysis）： 对分析结果有争议，要求权威部门用指定的方法、准确测定，进行裁判原分析结果是否正确，也称裁判分析。 • 仲裁分析对分析方法和分析结果准确度要求高。

  6. Quantitative analysis(定量分析) Gravimetric analysis Chemical analysis Volumetric analysis Spectrometry Instrumental analysis Chromatographic method Electrochemical analysis

  7. Acid-base titration (neutralization titration) • Oxidation-reduction titration • Coordination titration (EDTA titration) • Precipitation titration Volumetric analysis (volumetry, titrimetry)

  8. 10-1 General Principles of titration 10-2 Acid-Base Titration 10-3 EDTA Titration 10-4 Analytical Error and Significant Figures

  9. A titration is a standard laboratory method of chemical analysis which can be used to determinethe concentration of a unknown reactant. • In a titration two reagents are mixed, one with aknown concentrationandone with an unknown concentration. • There is some way to indicate when the two reagents have reacted essentially completely, and at the end of the titration the unknown solution's concentration can be calculated.

  10. General Principles of titration • Titration consists of adding carefully metered volumes of the solution ofknown concentrationto the othersolution ofunknown concentrationto reach an end-point.

  11. Typically, one reagent is a solution and is added from a buret. This solution is called the titrant or standard solution. The solution from the buret is added to a conical flaskthat contains either a measured volume of a solution or a weighed quantity of solid that has been dissolved. The buret has graduations that are used to read the volume of titrant added to the conical flask.

  12. Titration: Titrant (standard solution) Analyte (sample) Stoichiometric point Indicator Error of titration End point of titration

  13. Titrant in buret Analyte(sample) in conical flask indicator

  14. titration : fill buret remove bubble fill pipette(Ⅰ、Ⅱ) titration Ⅰ titration Ⅱ

  15. The requirement of a titration are as follows: 1.The reaction should be stoichiometric.   2. The reaction should be rapid. 3. There should beno side reactions, and the reaction should be specific. 4. There should be a marked change in some property of the solution when the reaction is complete. 5. The point at which the reaction is observed to be complete is called the end point. 6. The reaction should be quantitative.

  16. Operation system in titrametric analysis • 1. Prepare the standard solution • 2.standardization of the standard solution • 3.determine the content of the sample

  17. Standard Solution • Standard solution The concentration of a standard solution must be known within the limits of accuracy necessary in the actual analysis for which it is being used. Significant figure Four figures are necessary

  18. Prepare the standard solution • 1. Direct method: used primary standard substance Na2CO3 standard solution

  19. 2. Indirect method: NaOH standard solution HCl standard solution 2.间接配制法（标定法） 先配成一种接近所需浓度的溶液， 然后用基准物质（或用已经用基准物质标定过的另一标准溶液）来标定它的准确浓度。这种操作过程叫做“标定”。——间接法配制标准溶液。

  20. Standardization of standard solution HCl by Na2CO3 , NaOH by HCl 1.配制溶液： 配制成近似所需浓度的溶液。 2.标定： 准确称取基准准物，溶解后滴定。 3.确定浓度 由基准物质的质量或标准溶液的 浓度以及所取试液的体积计算之。

  21. primary standard substance • A primary standard substance should fulfill these requirements: 1. It should be 100.00%pure 2. It should be stable to drying temperatures 3. It should be readily available. 4. it should have a high formula weight.(large mole weight) 5. Reaction quickly

  22. titre Determine the content of the sample １毫升标准溶液(A)相当于被测物(B)的质量。 • 表示为 TB/A = g·mL-1或 %·mL- • T (Fe /K2Cr2O7)= 0.005260gmL-1，表示 1 mL K2Cr2O7标准溶液相当于0.005260g Fe， 即1 mLK2Cr2O7标准溶液恰好能与0.005260g Fe2+反应. • 若滴定消耗21.45mL K2Cr2O7标准溶液，试样中含Fe量为多少？ 0.005260gmL-1×21.45mL = 0.1128g

  23. 10-2 Acid-Base titration 1 Titration of a Strong Acid with a Strong Base the chemical reaction is the neutralization H3O+(aq) + OH- (aq) 2H2O(l) titrant: 0.1000 mol/L NaOH (in buret) titrate: 0.1000 mol/L HCl 20.00ml (in conical flask)

  24. ①. Initially, V =0.00ml NaOH added [H3O+]= 0.1000mol/L pH = 1.00 ②. V=18.00ml NaOH mol/L added mmoles acid left unreacted=2.000-1.800 =0.2000 volume solution =20.00+18.00=38.00ml pH = 2.28

  25. ③. V=19.80ml NaOH mol/L added mmoles acid left unreacted = 2.000-1.9800 = 0.02000 volume solution = 20.00+19.80 = 39.80ml pH = 3.30

  26. ④.V=19.98ml NaOH mol/L added mmoles acid left unreacted = 2.000 - 1.9800 =0.02000 volume solution = 20.00+19.98 = 39.98ml pH = 4.3

  27. ⑤. V=20.00ml NaOH mol/L added It is arrived at the equivalence point, the point in this titration: [H3O+] = [ OH-] [H30+ ] = 1.00×10-7 (mol/L) pH = 7.00

  28. ⑥. V=20.02ml NaOH mol/L added after the equivalence point mmoles base unreacted = 2.002-2.000 = 0.02000 volume solution = 20.00+20.02 = 40.02ml pOH = 4.30 pH =14-4.3=9.7

  29. ⑦.V=20.20ml NaOH mol/L added pOH = 3.30 pH =14-3.3=10.7

  30. ⑧.V=22.00ml NaOH mol/L added pOH = 2.32 pH =14-2.32 =11.68

  31. ⑨.V=40.00ml NaOH mol/L added pOH = 1.5 pH =14-1.5=12.5

  32. Titration jump 10 20

  33. Figure 10-1: A titration curve for the titration of a strong acid by a strong base.

  34. The magnitude of the titration jumpwilldepend on both the concentrationof the acid and the concentration of the base. • Usually, the concentration of standard solution should be 0.1000~0.5000mol/L

  35. Titration curves at different concentration • titration jump △p • 4.3～9.7 5.4 • 5.3～8.7 3.4 • 3 6.3～7.7 1.4 curve1. 100ml 0.1 mol/L HCl versus 0.1mol/L NaOH curve2. 100ml 0.01 mol/L HCl versus 0.01mol/L NaOH curve3. 100ml 0.001 mol/L HCl versus 0.001mol/L NaOH

  36. 突跃范围与酸碱浓度的关系 • 溶液的浓度愈稀，滴定突跃范围愈窄；若酸碱浓度低于10－4 mo1·L―1时，没有明显的滴定突跃。 • 酸碱溶液的浓度高时，滴定突跃范围就宽。 • 但每滴溶液中所含的酸碱溶液的量增多，在计量点附近多加或少加半滴（0.02ml）标准溶液而引起的误差较大。 所以在分析工作中，通常采用0.1～0.5 mo1·L―1的酸碱标准溶液。

  37. 2、Titration of a Weak Acid with a Strong Base titrant: 0.1000mol/L NaOH (in buret) titrate: 0.1000mol/L HAc 20.00ml (in conical flask) .

  38. 2-1. V =0.00ml NaOH HAc + H2O Ac- + H3O+

  39. 2-2. Less than the equivalent volume of NaOH has been added HAc(aq) + OH-(aq) = H2O(l) + Ac-(aq)

  40. 1). V = 18.00ml of 0.1000mol/LNaOH has been added

  41. 2).V = 19.98ml of 0.1000mol/LNaOH has been added:

  42. 3. V =20.00ml The equivalent volume of NaOH has been added • Ac- + H2O = HAc + OH- at equivalence point:

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