【Daily Question】Chemical Analysis Edition 2018.12.30

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This post was last edited by zjp on 2018-12-30 08:03. Multiple-choice question: Under which of the following circumstances will a positive error occur in the measurement (or calibration) results? () A. Titrate a certain base sample with an HCl standard solution. The burette used was not cleaned properly, resulting in droplets remaining on its inner wall during titration. B. When using K2Cr2O7 as a standard to determine the concentration of Na2S2O3 solution by the iodometry method, the titration was carried out too quickly, and the reading from the burette was taken too early. C. The standard used for determining the standard concentration became damp during weighing. (For calibration, direct titration is used.) ) D. When titrating the calcium and magnesium content using an EDTA standard solution, the titration rate is too fast. AC