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Explain why the titrations of Ca2+ with EDTA were performed at pH~10. Would the titration reach...

Explain why the titrations of Ca2+ with EDTA were performed at pH~10. Would the titration reach a satisfactory endpoint if the titration had been performed at pH = 6?

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Answer #1

Ans. The titration of Ca2+ with EDTA is performed at pH = 10 because of following reasons:

i)

The complete deprotonation of EDTA occurs at a high pH(strong basic conditions) only for the successful complexation with Ca2+ ions.

ii) The Eriochrome black T indicator used gives a color change in the range of around 8-11 pH only.

iii) The H+ ions formed are consumed easily at pH=10, thereby driving the reaction in forward direction.

No, the titration would not achieve a satisfactory endpoint if the titration is carried out at pH=6.

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