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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: timzor on July 06, 2010, 01:23:49 PM

Title: Titrations with polyprotic acids.
Post by: timzor on July 06, 2010, 01:23:49 PM

Hi guys,

Just having trouble understanding why polyprotic acids have more than one equivalence points. For example when titrating H₂SO₄ with NaOH, why are there two equivalence points

H₂SO₄ --> HSO₄- + H⁺
HSO₄- --> SO₄^2- + H⁺

If I react the H⁺ with OH^- wont both reactions go forward to replace the H+ and so only one equivalence point formed?

Thanks.

Title: Re: Titrations with polyprotic acids.
Post by: cliverlong on July 07, 2010, 05:45:38 AM

http://www.chemguide.co.uk/physical/acidbaseeqia/phcurves.html
http://www.chembuddy.com/?left=pH-calculation&right=pH-polyprotic-acid-base

Multiple K_a values

Clive