oxalic acid

用戶98670

2008-02-24 6:18 pm

a student stopped her oxalic acid titration as soon as she saw a faint pink color in the solution. however, she failed to swirl the solution properly, so she didnt realize that the pink color would have disappeared. will her reported molarity of concentrated oxalic be too large? too small? unaffected? exaplain your choice.

回答 (1)

Uncle Michael

2008-02-24 7:15 pm

✔ 最佳答案

The reported value of molarity of oxalic acid would be too small.

In the titration, the solution of a strong alkali (e.g. NaOH) in the burette is added to the oxalic acid solution in the conical flask.
If a faint pink colour appears when the solution is not properly swirled, it shows that the oxalic acid in the faint pink part of the solution is completely reacted, but there are still unreacted oxalic acid in other (colourless) parts. The amount of the strong base is less than that required. Since the concentration of the oxalic acid is calculated based on the amount of the strong base added, the reported value of the concentration of the oxalic acid would be small than the accepted value.

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