急---chem lab 問題(titration)

2007-09-21 5:03 am

add ethanedioic acid to sodium hydroxide for titration

why is phenolphthalein a suitable indicator for this titration???

更新1:

錯左應該係 add sodium hydroxide to ethanedioic acid for titration why is phenolphthalein a suitable indicator for this titration???

回答 (1)

snake_snake2000

2007-09-21 5:25 am

✔ 最佳答案

it is beacuse this titration is a weak acid strong base titration. the end point lies on the alkaline region.

since ethanedioic acid is a weak acid, H ions is given out slowly, so the titration curve will have sharp change from alkaline to neutral, then guardul decrease from neutral to acidic. As we know, we want a sharp change in pH so the indicator can change colour sharply. The alkaline region will be the only choose, thus, phenolphthalein, which has colour changing range (about pH8~10) is suitable

參考: don't copy my answer

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