化学专业英语第六课仪器分析英文课件.pptVIP

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. General principles of volumetric analysis The method is generally referred to as volumetric analysis and consists of titrating the unknown solution with one of known concentration (a standard solution). General principles of volumetric analysis By titration, you can determine exactly how much of a reagent is required to bring about complete reaction of the test solution. General principles of volumetric analysis 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 the reagent solution and the reactant in the test solution. General principles of volumetric analysis A drop or two of an appropriate indicator solution produces a color change at the point where the reaction is complete - referred to as the end point. General principles of volumetric analysis 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 have identical capacities for neutralization, because they contain the same number of equivalent weights. General principles of volumetric analysis In a titration, we compare equivalent weights of acid and base. The number of equivalents of acid is equal to the product of the volume of the acid solution and its normality: Procedure of volumetric analysis 所有滴定步骤都必须谨慎操作 Procedure of volumetric analysis Titration of Vinegar According to the equation One molecule of NaOH 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 numeri